This research theme continues to identifying and assessing possible impacts of offshore marine renewable energy developments on marine mammals, focusing mainly on seals.

MRE 1 Annual Report Year 1

The work presented under the Marine Renewable Energy (MRE) theme falls in to three tasks;

MRE 1.1 – Fine scale marine mammal behaviour around tidal energy devices.
MRE 1.2 – Harbour seal movement modelling.
MRE 1.3 – Estimating collision risk using available information.

Since MRE 1.1 will not start until year 2 of the project, and the deliverables for MRE1.3 have been amalgamated into the Marine Scotland project CR/2014/12 (which will report separately), this annual report presents on the progress for MRE 1.2 only.

MRE1.2

• Progress is reported on the development of an Inter-Haulout Transition Rate Model to explore and characterise harbour seal population movements in the area of Orkney and the Pentland Firth.
• Data from 41 tagged seals were collated and processed. A method was developed to accurately position haulout bouts within the tracks from these tagged animals. This was particularly necessary for the Argos tags as they provide less accurate position track data than GPS/GSM tags.
• A method was also developed to cluster the large number of individual haulout sites into a smaller number of haulout site clusters. This process reduced the amount of computation time required to run the model.
• At a given haulout site, the probability of a simulated seal being associated with any one of the 41 individual haulout transition matrices generated from the tagging data will be proportional to the amount of time that the tagged animal spent at that site.
• The simulations within in this model have not yet been completed. However, all the methodological developments have been completed.
• The structure of a proposed harbour seal Individual Based Model (IBM) is presented with the aim of ultimately demonstrating proof of concept of the IBM approach. The model is based on individuals alternating between foraging at sea and hauling out ashore, based on their individual states (internal properties such as body condition). Movement models based on both memory and exploration are being developed and will be incorporated. Shortest sea-route algorithms have been developed to assist in simulating the memory-based movement of seals to specific targets.
• Whilst the major simulations within this model have not yet been optimised, illustrative movement simulations have been completed. The ultimate challenge is thus to produce a model of appropriate complexity whose predictions (emergent properties) fit well with independent tagging data. The methodology for model validation and parameter estimation is under development after which proof of concept can be demonstrated.

A copy of the MRE 1 annual report year 1 is available for download.

MRE 2 Annual Report Year 1

Following on from the work of Thompson et al. (2015), modifications were made to collision apparatus to reduce the uncertainty surrounding the effective collision speeds of seals with modelled tidal turbine blades.

A copy of the MRE2 annual report year 1 is available for download.

MRE 1 Annual Report Year 2

The work presented under the Marine Renewable Energy (MRE) theme falls in to three tasks;

MRE 1.1 – Fine scale marine mammal behaviour around tidal energy devices.
MRE 1.2 – Harbour seal movement modelling.
MRE 1.3 – Estimating collision risk using available information.

Since the deliverables for MRE1.3 have been amalgamated into the Marine Scotland project CR/2014/12 (which has reported separately), and there is nothing to report for MRE 1.2 in this project year, this annual report presents on the progress for MRE 1.1.

MRE 1.1

• This task aims to monitor the behaviour of harbour seals (and other marine mammals) in the vicinity of an operational tidal turbine. A monitoring system utilising a combination of Passive Acoustic Monitoring (PAM), Active Acoustic Monitoring (AAM) and video cameras was designed to identify the species of marine mammal and to construct 3D tracks of animals in close proximity to the tidal turbine.
• The PAM system, consisting of three clusters of four hydrophones, to detect and track vocalising cetaceans was designed and built. This was successfully installed and tested with the Atlantis control systems on the Atlantis AR1500 Turbine Support Structure (TSS).
• A multibeam AAM system (using Tritech Geminis) to detect and track marine mammals in 3D was designed and manufactured. This has been mounted on a seabed platform 30 m to the side of the turbine axis, which should provide good coverage of the turbine and surrounding waters.
• A bespoke mounting frame for the sonars was designed and built allowing the pitch and roll angles of the sonars to be measured and adjusted as required. This was built with anodised steel and is controlled using two motorized actuators.
• To reduce post hoc analyses, new marine mammal classification algorithms and 3D tracking outputs had to be integrated into the existing multibeam sonar software. This was carried out by Tritech software engineers and has been fully implemented in a bespoke version of the SeaTec software (V2.0020.05).
• In collaboration with Atlantis engineers, a High Current Underwater Platform (HiCUP) to house the AAM system was redesigned to meet with deployment specifications, and to ensure stability in the current flow predicted at the tidal turbine location. The HiCUP construction was completed and lift tests and inspections have been certified by Atlantis. It was attached on a mounting bracket on the Atlantis TSS and loaded out onto the seabed.
• A two camera video system to image marine mammals at the turbine was designed and manufactured. The high-end video surveillance cameras used have an all-round view over a full hemisphere. The cameras were modified to include ultraviolet LED’s in custom built underwater housings in order to reduce biofouling on the windows. Cameras have been successfully installed on the Atlantis TSS, and tested with the Atlantis control systems prior to installation of the TSS on the seabed.
• The full sensor system was deployed successfully with the Atlantis TSS on 24th October 2016.
• Ten harbour seals were caught in the Inner Sound during September and October 2016 and were fitted with high resolution UHF/GPS and depth logger tags so that fine scale movement can be interpreted within a wider spatial context. These aim to provide real time locations of seals to base stations on shore each time a seal surfaces, providing supporting evidence helping to determine if a collision occurs between a seal and a turbine.

MRE1.2

• A prototype individual based model (IBM) of harbour seal movement over time scales of days/weeks has been developed for the Pentland Firth / Orkney area. Many of the parameters in the model are place-holders (albeit realistic ones), with values that will be refined in the next stage of model development. The prototype IBM has a simple structure but it nonetheless captures the basic movement patterns and behaviour that is observed in harbour seal telemetry data.
• Full description and analysis of the work carried out under this deliverable will be presented in the final report, to be submitted by July, 2017.

A copy of the MRE1 annual rep year 2 is available for download.

MRE 2 Annual Report Year 2

In the absence of any field data, collision risk models currently assume that all collisions between marine mammals and tidal turbines will be fatal. This precautionary assumption is not likely to be true and could lead to over-estimation of mortality rates. This has the potential to be a serious constraint on the development of the tidal energy industry.This issue was initially addressed in MMSS/001/11 – MR 7.2.3 through a series of collision trials using grey seal carcasses and a simulated turbine blade fixed to the keel of a jet drive boat. The model turbine blade ran along the curved keel of the boat. This curved deployment angle was likely to have reduced the energy transferred from the boat to the carcass when compared with a collision with a perpendicular blade, so the results of these initial trials were treated with caution. Refinements were made to the experimental set-up for the second set of trials, outlined in this report. Three lengths of aluminium box-section were welded to the keel of the boat to act as bolt-points for rigid support beams. These support beams were bolted to the turbine blade model to secure its deployment angle. The resulting deployment angle was close to perpendicular to the surface water at the point of impact, as confirmed by photographs.

Five juvenile grey seal carcasses were subjected to collision trials at a range of speeds between 9.26 m.s-1 and 10.29 m.s-1. Four carcasses were struck twice and the final carcass was struck three times, each time at a different location. Pre and post-trial x-rays as well as post-trial computerised tomography scans and post-mortems were carried out to establish trauma associated with the collisions. No skull damage was observed in the trials but all cases showed varying degrees of spinal fracture and three out of five cases showed signs of damage to the rib-cage. Massive diaphragmatic rupture was found in all cases. Other injuries noted were herniation and maceration of the liver, and lung congestion. However, soft-tissue damage was not considered a reliable indicator of collision consequences given the reduced integrity of the organs as a result of the freeze-thaw process. All of these pathological features were considered to have been likely to be lethal to a seal.

These results indicate that collisions with the tip of a tidal turbine blade travelling at >10.29 m.s-1 would be lethal to a juvenile grey seal. When compared to the results from MMSS/001/11 – MR 7.2.3 it would appear a threshold exists (above 5.32 m.s-1 and below 10.29 m.s-1) below which a significant proportion of turbine blade collisions would not produce lethal, skeletal damage. Further trials, using the same experimental set-up and a combination of previously frozen and un-frozen seals is planned to a) establish a mortality threshold, and b) assess soft-tissue damage.

A copy of the MRE2 annual report year 2 is available for download.

MRE1  Annual Report Year 3

The work presented under the Marine Renewable Energy (MRE) theme falls in to three tasks;

MRE 1.1 – Fine scale marine mammal behaviour around tidal energy devices.
MRE 1.2 – Harbour seal movement modelling.
MRE 1.3 – Estimating collision risk using available information.

As MRE 1.2 has been delivered and the deliverables for MRE1.3 were amalgamated into the Marine Scotland this annual report only considers MRE 1.1 as MRE 1.2 and 1.3 have been completed.

MRE 1.1

• This task aims to monitor the behaviour of marine mammals in the vicinity of an operational tidal turbine. A monitoring system utilising a combination of Passive Acoustic Monitoring (PAM), Active Acoustic Monitoring (AAM) and video cameras was deployed to identify marine mammal species using the areas around the turbine and to construct 3D tracks of their movements.
• The environmental monitoring system was successfully installed on the Turbine Support Structure (TSS) at Nigg on 3 October 2016 with deployment of the TSS at the site on 24 October 2016. Following the installation of the Atlantis Turbine in February 2017, initial commissioning of the monitoring system revealed a communications failure with all of the sensors. This was corrected during shore-based maintenance of the turbine in the summer of 2017.
• The Atlantis turbine was successfully re-deployed in mid-October 2017 and a second period of monitoring system commissioning was conducted. Power to the monitoring system turbine became available on 18 October and initial communications tests established that the PAM system was fully functional. However, no communications could be established with the video camera systems or the Gemini multibeam sonars. Plans to recover the platform with the sonars are currently being developed.
• Since commissioning, the PAM system has been operating stably for 95.7 % of the time. From the start of data collection up to the end of 31 December 2017 (~ ten weeks) a total of 11 dolphin and 199 porpoise encounters were made. This equates to a mean of 2.8 porpoise encounters and 0.2 dolphin encounters per day.
• A key output from the PAM data analyses will be the 3D locations of echolocation clicks in relation to the turbine. Echolocation click localisation techniques are currently being refined using the data collected. An important aspect of 3D localisation is to calibrate the array by pinging it with a sound source from a known location; trials to do this are being planned and will be used to improve localisation accuracy.
• To examine fine scale movement of seals in a wider spatial context, 24 harbour seals were caught and tagged in the Inner Sound during two field efforts between 26 September and 3 October 2016, and between 2 and 13 April 2017. These data aim to provide real time locations of seals to base stations on shore each time a seal surfaces, providing supporting evidence to determine if a collision occurs between a seal and a turbine.
• In total 115,100 locations were recorded from the tagged seals during the two tagging deployments. Seals spent 16 % of their time in the Inner Sound, with a relatively low number of locations (195) recorded within the MeyGen lease area. Only three seals were recorded at the surface within 100 m of any of the turbines; the closest surface location to any of the turbines was 35.15 m.

A copy of the MRE1 annual report year 3 is available for download.

MRE1  Annual Report Year 4

The work presented under the Marine Renewable Energy (MRE) theme falls in to three tasks;

MRE 1.1 – Fine scale marine mammal behaviour around tidal energy devices.
MRE 1.2 – Harbour seal movement modelling.
MRE 1.3 – Estimating collision risk using available information.

This annual report only considers MRE 1.1 as MRE 1.2 and 1.3 have been completed.

MRE 1.1

This task aims to monitor the behaviour of marine mammals in the vicinity of an operational tidal turbine. A monitoring system utilising a combination of Passive Acoustic Monitoring (PAM), Active Acoustic Monitoring (AAM) and video cameras was deployed on a MeyGen turbine in the Pentland Firth to identify marine mammal species using the areas around the turbine and to construct 3D tracks of their movements.

After initial deployment on 24th October 2016, power to the turbine did not become available until 18th October 2017 when initial communications tests established that the PAM system was fully functional. However, no communications could be established with the video cameras or the Gemini multibeam sonars.

The sonar platform was recovered by SIMEC Atlantis Energy on 23rd July 2018 during planned operations to recover two other turbines. Subsequent inspection and fault diagnosis was undertaken by SMRU personnel at Nigg Energy Park on 7th August 2018. A number of possible failure points were identified including minor damage to the umbilical cable from the TSS, severe corrosion of the Hydrobond connectors used to attach the umbilical cable to the junction box, and water ingress in the junction box.

Since commissioning in October 2017, the PAM system has been operating stably for 95.3% of the time. The turbine was removed for maintenance from 22nd September 2018 to 18th December 2018, with PAM data collection resuming on the 19th December 2018.

The PAM system remains operational with routine checks and data archiving continuing. As agreed in the Steering Group meeting on 19th September 2018, monthly reporting was discontinued following the September 2018 report. Data collected following 31st January 2019 will not be manually processed for detections.

From the start of data collection up to the end of 31st January 2019 (~ 13 months monitoring), a total of 27 dolphin and 571 harbour porpoise encounters (≥ 30 clicks) were made. This equates to a mean of 1.6 (SD = 1.0) porpoise encounters and 0.1 (SD = 0.2) dolphin encounters per day.

A key output from the PAM data analyses will be the 3D locations of echolocation clicks in relation to the position and operational status of the turbine. Field trials to calibrate 3D localisation algorithms were conducted on 6th August 2018. This involved pinging the PAM array with a sound source from a vessel at known locations and depths. Data collected in these trials have been useful with the ongoing refinement of the PAMGuard localisation algorithms.

24 harbour seals had previously been tagged in the Inner Sound to quantify the movements of seals in a wider spatial context. A further 16 harbour seals were tagged between 16th and 24th April 2018. Of these, 12 transmitted location data and 12 transmitted high resolution dive data.

Of the tags deployed in 2018, 504 days of data were collected which included 53,484 GPS locations. Tagged seals spent ~12% of their time within the Inner Sound and ~0.001% within the MeyGen lease area. A total of 3 GPS locations were recorded within 50m of a turbine and the closest GPS location was 37m from a turbine.

A copy of the MRE1 annual report year 4 is available for download.

This research theme continues to try to identify and assess possible factors affecting the population levels of UK harbour seals.

HSD 2 Annual Report Year 1

Numbers of harbour seals (Phoca vitulina) have dramatically declined in several regions of the north and east of Scotland, while numbers have remained stable or have increased in regions on the west coast. For any management and mitigation plans to address this situation, the relative contribution of various factors in the decline of harbour seals in Scotland needs to be identified, understood and assessed. Potential drivers of the decline include changes in prey quality and/or availability, increasing grey seal population size which may be influencing harbour seal populations through direct predation or competition for prey resources, and the occurrence and exposure of seals to toxins from harmful algae.

Previous work by Matthiopoulos et al. (2014) and Caillat and Smout (2015) developed and fitted an age-structured population model to data from the well-studied subpopulation of harbour seals in Loch Fleet (Moray Firth), to evaluate the contributions of different potential proximate causes to the observed decline. After reviewing the existing software, this model has been re-coded directly into R, a framework that will allow for future development and maintenance, and has been designed to be adapted to different model structures and future data sets. Preliminary results are consistent with those obtained from the original OpenBUGS modelling. Future work will have as its key objective the identification of the important drivers of population change in harbour seals, from those being studied as listed above. Temporal and spatial variation in these drivers will be incorporated into the population model.

Harbour seal haulout sites located in different regions of Scotland were visited in the spring and the summer of 2015 to collect information on their suitability for long-term monitoring of harbour seal populations, including their suitability for live captures, scat sampling, aerial and ground survey counts during pupping and moulting and photo-identification. This will allow empirical data to be collected and vital rates (fecundity and survival) to be estimated, for inclusion in the population model.

A haulout site located in West Burray (Orkney) has been selected to represent a region of decline, and a haulout site by Peninver (East Kintyre) has been selected to represent a region of stability or increase. In addition, photo-identification data will also be collected in Dunvegan Loch (Isle of Skye). The regional scope of local populations at each study site (Orkney, Kintyre and Isle of Skye) has been defined to direct future collation of any relevant environmental and biological data. Existing aerial survey counts of harbour and grey seals at each of the defined areas have been collated for use in the age-structured population model.

As part of the live captures programme, female harbour seals will be fitted in 2016 with low-cost electronic location tags, developed to allow a larger number of captured seals to be tagged and designed to regularly relay GPS locations from terrestrial locations. Data from these tags and from ten SMRU GPS/GSM phone tags will inform and direct the extent of the photo-identification re-sighting effort at haulout sites in 2016.

Domoic acid (DA) concentrations have been measured in urine and faecal samples collected from harbour seals in 2015, as a continuation of the work carried out by Jensen et al. (2015). DA is still being found in harbour seals around the Scottish coast and whilst concentrations vary between the different matrices (blood, faeces and urine) and samples, due to variation in exposure and time from uptake to excretion, some individuals appear to be consuming relatively high levels of toxin. Data from the monitoring of biotoxins in shellfish by the Centre for Fisheries and Aquaculture Science (Cefas) and Harmful Algal Blooms (HABs) by the Scottish Association for Marine Science (SAMS) were available for all of 2015 and January 2016. These datasets provide some indication of the occurrence of HABs and toxin-producing blooms in the regions of interest.

To further improve understanding of potential drivers of population change, initial contacts have been made to investigate the availability of prey samples relevant to seals foraging from the study sites, as well as the availability of prey abundance data from long-term fish surveys in the different regions of interest.

An update is provided on the current state of knowledge of the causes of spiral lacerations in seals based on necropsy results of stranded individuals since November 2014. Occurrences around Scotland are summarised along with objective assessments of the cause of the wound patterns, based on a weighted scoring system.

A copy of the HSD2 annual report year 1 is available for download.

HSD 2 Annual Report Year 2

Numbers of harbour seals (Phoca vitulina) have dramatically declined in several regions of the north and east of Scotland, while numbers have remained stable or have increased in regions on the west coast. For any management and mitigation plans to address this situation, the relative contribution of various factors in the decline of harbour seals in Scotland needs to be identified, understood and assessed. Potential drivers of the decline include changes in prey quality and/or availability, increasing grey seal population size which may be influencing harbour seal populations through direct predation or competition for prey resources, and the occurrence and exposure of seals to toxins from harmful algae.

Previous work by Matthiopoulos et al. (2014) and Caillat and Smout (2015) developed and fitted an age-structured population model to data from the well-studied subpopulation of harbour seals in Loch Fleet (Moray Firth), to evaluate the contributions of different potential proximate causes to the observed decline. Work has continued to build on the original Moray Firth study, re-coding a simplified version of the population model in JAGS language. A decision support tool (DST) has also been developed to include a biologically realistic simulation model and a model-fitting step that attempts to recover the parameters used in the simulation. A simple population model was successfully fitted to historical data for Scapa Flow (Orkney), with the Markov chain Monte Carlo (MCMC) converging and estimating reasonable-seeming parameter values. The DST was used to explore fitting limited data sets. The simulation/fitting approach showed that the fitting software was able to estimate parameters from the data even when the data set was ‘thinned’ (data not available for every year) and when no pup count data were available.

Live capture-release studies were conducted in Orkney in April and May 2016 under the SMRU Animal (Scientific Procedures) Act, 1986, (Home Office Licence No. 192CBD9F). Adult and juvenile harbour seals were captured, individual covariate data were collected from each seal and telemetry tags (GSM/GPS and LO tags) were deployed on adult seals, primarily on females, to direct the photo-identification effort prior to and during the pupping season. Pregnancy status was determined from progesterone concentrations in the plasma and in blubber, and from 17 beta-oestradiol concentration in plasma. Results show the blubber concentrations of progesterone may be a much more reliable indicator of pregnancy than levels in plasma. The proportion of the live-captured adult females that were pregnant was 61.5% (95% CI 35% – 88%), which is lower than would have been expected. However, given the small sample size further investigations must be carried out before any conclusions can be drawn. Domoic acid concentrations in the urine and faecal samples collected from the live capture-release animals were determined. Two animals had levels below the limit of detection, but the majority (88%) were above this level, indicating some low level exposure. Additionally, a further six scats collected at the capture haulout sites during May and June were also analysed. Of these, three were positive for DA but the remainder were below the limit of detection or samples were too small for analysis. Two fishing trips to collect prey samples were undertaken in the waters off Scapa Flow on the west coast of Orkney mainland. A total of 85 fish guts were sampled: 35 cod samples, 12 haddock, 36 ling and two torsk. All fish viscera were analysed for domoic acid content, using the same method as for the seal samples. All samples were positive for domoic acid at or above the limit of detection, although, in general, concentrations in all fish sampled were at low levels.

Moult aerial helicopter surveys were conducted in August 2016 in Orkney as part of the annual surveys conducted by SMRU. Breeding aerial surveys were also conducted in 2016 in Scapa Flow (Orkney), Kintyre and Isle of Arran, and Loch Dunvegan, using a fix-wing aircraft and digital photography. The difficulty of locating seals at haulouts from the aircraft and the impossibility of identifying age classes in the digital photographs led to the decision of excluding such data from the population model.

A summary of all seal carcasses reported to SMASS within and nearby the study sites between June 2016 and March 2017 is provided, with details on species, age class and proximate cause of death when available.

A copy of the HSD 2 annual report year 2 is available for download.

HSD 2 Annual report Year 3

Numbers of harbour seals (Phoca vitulina) have dramatically declined in several regions of the north and east of Scotland, while numbers have remained stable or have increased in regions on the west coast. For any management and mitigation plans to address this situation, the relative contribution of various factors in the decline of harbour seals in Scotland needs to be identified, understood and assessed. Potential drivers of the decline include changes in prey quality and/or availability, increasing grey seal population size which may be influencing harbour seal populations through direct predation or competition for prey resources, and the occurrence and exposure of seals to toxins from harmful algae (domoic acid and saxitoxins).

Population model

Work continued to develop an integrated harbour seal population model. The model-fitting process was built upon, using a decision-support simulation tool to fit an age-structured population model to harbour seal count data, investigating the effect of ‘reducing’ the data by only including moult counts (excluding pup counts) and thinning the number of available data points. A visualisation tool was developed to support discussions about the relative impacts of effects that might be important during the different phases of harbour seal life-history. Based on simulated data, a number of scenarios were explored in which additional mortality, fecundity, and adult and pup survival were allowed to vary within plausible limits. The resulting effect on the predicted (simulated) population growth was visualised by means of a surface plot.

Photo-identification mark-recapture to estimate fecundity and survival

Photo-identification data were collected at selected harbour seal haulout sites in Orkney, Kintyre and Loch Dunvegan (Isle of Skye) during the pupping season in 2016 and 2017, primarily during the months of June and July. All photographs were graded for quality and individual seals identified from the unique patterns in their pelage. Photo-identification data collected in 2017 is currently being processed. For 2016, a summary of all catalogued seals by area with details on approximate age class and reproductive history has been made. Loch Dunvegan produced the highest number of catalogued seals. One of the monitored haulout sites in Kintyre was male-dominated, while mum-pup pairs were found in other sites.

Live capture-release studies

Live capture-release studies were conducted in Isle of Skye in March and Orkney in April and May 2017 in accordance with the SMRU Animal (Scientific Procedures) Act, 1986, (Home Office Licence No. 192CBD9F). Adult and juvenile harbour seals were captured, individual covariate data were collected from each seal, and telemetry tags (GSM/GPS and LO tags) were deployed primarily on adult females. Pregnancy status was determined from progesterone concentrations in the plasma and in blubber. The proportion of the live-captured adult females that were pregnant was 100% (95% CI 95% – 100%) in Isle of Skye and 67% (95% CI 39% – 95%) in Orkney, but the proportions were not statistically significantly different. Given the small sample size, further investigations must be carried out before any conclusions can be drawn. Domoic acid concentrations in the urine and faecal samples collected from the live capture-release animals were determined. Domoic acid concentrations were lognormally distributed, with some individuals having very high levels but in most animals concentrations were low. There was no difference in the median concentrations by region, with the Skye animals also being exposed to domoic acid.

Prey samples

Two fishing trips to collect prey samples were undertaken in July and November 2017 in the waters of Scapa Flow. Additionally, opportunistic fish samples were collected in North Ronaldsay. All fish viscera were analysed for domoic acid content, using the same method as for the seal samples. All samples were above the limit of detection, with the bullrout, and mackerel caught in the summer showing the highest concentrations. Fish guts sampled in Orkney in July 2017 and in Sinclair Bay (Caithness) in June 2017 were analysed for PSP toxins, but none of the samples contained any detectable level of saxitoxin.

Counts of harbour seals during the moult

Aerial surveys of harbour seals numbers hauled out during the moult were conducted in the study sites of Kintyre, Scapa Flow (Orkney) and Loch Dunvegan (Isle of Skye) in August 2015, 2016 and 2017, respectively, as part of the annual surveys conducted by SMRU (funded by Scottish Natural Heritage (SNH) and Natural Environment Research Council (NERC)). Results on the number of harbour and grey seals counted within the defined study areas are presented.

Stranded seals

A summary of all seal carcasses reported to Scottish Marine Animal Stranding Scheme (SMASS) within and nearby the study sites between March 2017 and February 2018 is provided, with details on species, age class and proximate cause of death when available.

A copy of the HSD 2 annual report year 3 is available for download.

HSD 2 Annual report Year 4

Numbers of harbour seals (Phoca vitulina) have dramatically declined in several regions of the north and east of Scotland, while numbers have remained stable or increased in regions on the west coast. For any management and mitigation plans to address this situation, the relative contribution of various factors in the decline of harbour seals in Scotland need to be identified, understood and assessed. Potential drivers of the decline include changes in prey quality and/or availability, increasing grey seal population size which may be influencing harbour seal populations through direct predation or competition for prey resources, and the occurrence and exposure of seals to toxins from harmful algae (domoic acid and saxitoxins).

Integrated population model

In Year 4, efforts towards developing an integrated harbour seal population model included review and expert elicitation of plausible ranges for harbour seal vital rates, simulation of population trends with different sets of vital rates, and analysis of population sensitivity to changes in individual vital rates. Through the expert elicitation process, participants decided on consensus distributions that reflected the availability and uncertainty of published estimates of vital rates for harbour seals. The simulation exercise demonstrated that the population is sensitive to changes in adult survival, and that a decrease in adult survival is required to explain a decline of the magnitude observed at sites like Scapa Flow, Orkney. The next step will be to incorporate photographic mark-recapture data and environmental covariates into the integrated population model framework.

Photo-identification mark-recapture to estimate fecundity and survival

Photo-identification data were collected at selected harbour seal haulout sites in Orkney, Kintyre and Loch Dunvegan (Isle of Skye) during the pupping seasons of 2016, 2017 and 2018, primarily during the months of June and July. To build individual sighting and reproductive histories, which will be then used to estimate fecundity and survival rates, all photographs are first graded for photographic quality, and then individual seals are identified from the unique patterns on their pelage. Photo-identification data collected in 2018 are currently being processed. For 2016 and 2017, a summary of all catalogued seals by area with details of estimated age class and reproductive history is provided. The total number of seals identified in each area and year ranged between 155 and 550 seals, with Isle of Skye having the largest numbers, both for adults and pups. There was a consistency in the proportion of females seen with a pup and/or pregnant between years in each area. However, these proportions should not be interpreted as fecundity rates. The re-sighting rates of adult females that had pupped in 2016 were high in all three areas (range 77.8 % to 88.5%), and 59.0% to 61.1% of these females were seen again with a new pup in 2017.

Live capture-release studies

Pregnancy rates: Further analysis of the proportion of live captured females that were pregnant in each region was carried out. A proportion of the sampled females (n=23) were subsequently observed during the photo-ID fieldwork in Orkney and the Moray Firth. This provided a training dataset of animals observed pregnant or with a pup. Combining these observations with the pregnancy hormone, progesterone, concentrations in the blood and blubber for these animals resulted in a probability estimate of the proportion of pregnant females in each region. There was no difference in the percentage of animals that, according to their hormone levels, had a >60% probability of pupping among the different regions, despite a lower percentage in Orkney compared to elsewhere (Moray Firth 83%, Pentland Firth 88%, Skye 83%, Orkney 69%). This was largely due to the small sample sizes and the degree of regional variability. However, comparing these results with the regional fecundity estimates may indicate if reproduction is indeed lower in the regions of decline.

Nutritional stress indicators: Serum and plasma samples were analysed for selected clinical chemistry parameters to determine nutritional condition. A principal component analysis (PCA) was used to investigate whether there were any differences between the samples collected from the animals on Isle of Skye compared to Orkney. The variability in the data was much greater for Orkney than for Isle of Skye but the values were all within what would be considered clinically normal for this species. Thus, from these data there was no evidence that the captured seals are experiencing nutritional stress or were malnourished.

Toxins in prey and live captured seals

Toxins from harmful algal blooms continue to be found in the urine of harbour seals. Low levels of domoic acid were measured in live captured animals. However, these levels probably underestimate the peak levels

that individuals would have been potentially exposed to during feeding bouts, due to the short half-life of domoic acid and the time elapsed between feeding and sampling. Work is currently underway to estimate peak exposure.

The role of toxins in harbour seal health may also be inferred by measuring their levels in prey items. Samples of fish prey of various species found in the diet of harbour seals in two of the study areas, Scapa Flow in Orkney and Loch Dunvegan on Isle of Skye, were obtained. Concentrations of domoic acid were low in all species although all fish were sampled outside a toxic bloom event period. To better understand how the toxin levels in prey relate to the domoic acid levels found in urine and faeces, estimated domoic acid ingestion rates were compared to toxic thresholds. Results showed that up to 6% of adults and 31% of juveniles could be consuming levels high enough to affect kidney and reproductive function. However, all were below any lethal thresholds. If possible, further samples will be collected during bloom events in these regions.

During the fish-sampling fieldwork at sea, opportunity was taken to evaluate different methods to characterise prey presence at a selection of the putative seal feeding areas, inferred from telemetry movement data. The methods included sonar logs and baited camera traps. In addition, the species of fish caught at each sampling location also served as a (biased) proxy of species presence. This evaluation is on-going.

Counts of harbour seals during the moult

Aerial surveys of harbour seal numbers hauled out during the moult were conducted in the study sites of Kintyre, Scapa Flow (Orkney) and Loch Dunvegan (Isle of Skye) in August 2015, 2016 and 2017, respectively, as part of the annual surveys conducted by SMRU (funded by Scottish Natural Heritage (SNH) and Natural Environment Research Council (NERC)). Results on the number of harbour (and grey) seals counted within the defined study areas are presented and the population trends have not changed (stable in Kintyre and Skye, declining in Orkney). The Kintyre area was also surveyed in 2018; photographs taken and resulting counts are currently being processed.

Stranded seals

A summary of all seal carcasses reported to Scottish Marine Animal Stranding Scheme (SMASS) within and nearby the study sites between March 2018 and March 2019 is provided, with details on species, age class and proximate cause of death when available. A total of 162 seal carcasses were reported in this period, mostly reported in Orkney (n=133). These included 123 grey seals, 19 harbour seals, and 20 seals for which species could not be determined. Post-mortem examination could only be conducted for one carcass, as the others were not in good condition or could not be recovered. Proximal cause of death was determined for 26 seals from observations, 25 of which were possible cases of grey seal attack, including three harbour seals, 21 grey seals (mostly weaned pups) and 1 seal of unknown species.

A copy of the HSD 2 annual report year 4 is available for download.

This research theme focuses on the interactions between seals and commercial wild salmon fisheries around Scotland.

SSI Annual Report Year 1

This document reports on progress made on marine mammal research at wild salmon fisheries during 2015. The objectives of the research were: 1) to continue studies into the effectiveness and practical application of Acoustic Deterrent Devices (ADDs) and the modification of salmon nets to mitigate the effects of seals on these fisheries; 2) to collect shot seals for dietary analysis; and 3) to provide support to District Salmon Fishery Boards (DSFBs). Activities related to the first two objectives were primarily focused on two sites in the Moray Firth; Gamrie Bay and Portmahomack.

During 2015, trials on the efficacy of an Airmar ADD continued near Crovie, Gamrie Bay, as did the evaluation of net modifications at this fishery by assessing the effectiveness of two different sizes of fish court entrance. Both ADD trials and net modification trials were conducted at the same netting site, with a balanced design of ADD ‘on’ and ‘off’ periods across the deployment of the two types of net.

Underwater video equipment collected footage from inside the nets for over 1200 hours. The fishery provided salmonid catch and fish damage statistics for each haul of the net for the entire season, and environmental data were collected from a weather station deployed close to the netting site. Analysis of the collated data showed there was a significantly lower probability of detecting a seal during ADD ‘on’ treatments compared with ADD ‘off’ treatments. Furthermore, undamaged catch per unit effort was significantly greater when the ADD was ‘on’ compared with ‘off’, but also significantly greater when the wind direction was onshore compared with offshore. Net modification trials enabled the identification of a compromise that excluded seals from the fish court whilst allowing swift passage of fish through the net, reducing depredation opportunities for seals in both chambers of the net.

At Gamrie Bay (More Head) and Portmahomack, support was provided for fishery-led ADD deployments. In both instances the deployments were run entirely by the fisheries who also collected and provided catch statistics and anecdotal observations. The overall perception of the fishers towards the ADD was positive, and was supported by the data which indicated that landings were higher when the ADDs were ‘on’ and that levels of damage were lower. There was still some evidence however that seals can depredate and damage fish in the nets while ADDs were ‘on’.

During 2015, a further twelve shot seal carcasses were recovered from bag-net sites. Diet information from these seals shows that lethal control is becoming increasingly selective, with a greater proportion of the recovered seals having consumed salmonids. This may be the result of the increasing use of ADDs and net modifications which are helping to reduce the shooting of transient seals.

Presentations have been provided on these studies, along with further support to river fisheries when requested, particularly from the Dee Fishery Board. Where requests for support were received, this led to a channel of communication between those working in river fisheries and SMRU, which is beginning to form the basis of good collaborative work.

This project is continuing to produce encouraging results from the use of ADDs and net modifications at mitigating the effects of seals on these fisheries, and is maintaining positive and open relations with both net and river fisheries.

A copy of the SSI annual report year 1 is available for download.

SSI Annual Report Year 2

This report provides a brief overview of fieldwork currently underway and due to be completed by 31st March, 2017. Identification of seals, their behaviour in river systems and observed frequency of salmonid predation will provide a better understanding of how seals use the river and help to develop practical options to reduce the need for lethal removal. Information gathered will help assess the effectiveness of non-lethal methods aimed at reducing the conflict between seals and salmon fisheries. A perception held by salmon fisheries is that seals cause serious damage to salmon and trout stocks. The data collected under this effort will provide insights into the potential level of impact of seals on salmonid stocks. Data processing will be conducted over the next few months, and final reporting on this fieldwork is scheduled by 31st August 2017.

A copy of the SSI annual report year 2 is available for download.

Interim Report on Seals and Wild Salmon Fisheries

This interim report documents findings from observational studies of seals at the Donmouth harbour seal haulout and provides an update on the ongoing analysis of seal observations from the River Dee, as well as other activities associated with the Seals and Salmon Interactions programme.

A copy of the Interim Report on Seals and Wild Salmon Fisheries is available for download.

SSI Annual Report Year 3

This annual report documents progress made under the Seals and Salmon Interactions (SSI) theme of the Marine Mammal Scientific Support Research Programme. It provides an update on the ongoing scientific and management advice activities between April 2017 and March 2018. The overall aim of the SSI theme over the past 12 months has been to help reduce conflict between river fisheries and seals.

The scientific activities reported include completion of the processing of the 50,000 photo-identification images from the 2016-2017 field effort, the capture and tagging of four harbour seals at the Donmouth haulout and the subsequent mapping of tracks to date, and additional scat and skin sampling to better understand diet and association with breeding areas through genotyping.

The management activities reported include the development and trialling of methods to catch river-using seals, and the support provided to District Salmon Fishery Boards (DSFBs) and river fisheries. In particular, details of catching methods that have been deployed in the River Dee and at the Donmouth haulout in late 2017 and early 2018 are described.

Other activities completed this year include delivery of an interim report documenting findings from the study of seals in rivers, including a preliminary investigation of seal sightings, predation rates and the spatial distribution of seals in Aberdeen Harbour (available for download), and a briefing paper, “Review of options (including non-lethal measures) to limit seal access to salmon rivers”, was also delivered.

A copy of the SSI annual report year 3 is available for download.

SSI Annual Report Year 4

The overall aim of the Seals and Salmon Interactions (SSI) project is to reduce conflict between seals and salmon fisheries. The current focus of the SSI is to reduce conflict within river systems. Project activities have been split into those with a scientific focus and those with a management focus. This annual report details progress and outputs from both scientific and management activities carried out over the last 12 months.

Scientific activities have focussed on addressing a series of questions relating to seal behaviour and ecology within river systems to inform issues raised by fisheries. Data collected during a 12-month observational study of Aberdeen Harbour and the River Dee in 2016-2017, as well as data from a movement (using telemetry) and diet study, have been processed and analysed within this reporting period with the aim of answering questions about how animals use the river system habitat. Approximately 50,000 photographic images from the observational study across the River Dee and Donmouth seal haulout site have been processed. The analysis of these images has resulted in the identification of 19 individual grey seals and 17 individual harbour seals from the River Dee. Of these 36 individual seals, 14 were categorised as salmonid specialists, 15 as regular users of the river system, and 7 as transient, based on the frequency of occurrence and their behaviour. It is believed that very few individual seals using the harbour/river were not identified during this period. Seals were seen throughout the year in the harbour but most often during winter months higher up the river. Predation events were also recorded during the observation period and it was found that predation events in the harbour peaked between December and February. A statistical model of predation events predicted the highest probability of an event occurring was during the first two quarters of the year (January-June) and increased with increasing river flow.

The presence of bottlenose dolphins and otters was also recorded during observation periods and piscivorous bird feeding events were photographed in an attempt to identify prey items. The presence of bottlenose dolphins was highest between January and June (coinciding with the period of highest probability of a salmonid predation event by seals) and otter presence was highest during the winter months (October-March). Photographs were taken of piscivorous bird predation events to provide information on the diversity of prey species available within the harbour environment.

Results of the telemetry and diet study of seals using the Donmouth haulout have previously been reported in full in an Interim Report delivered in 2018 and therefore are only summarised in this Annual Report. The scat samples were dominated by whiting and flatfish otoliths, and only one scat contained salmonid otoliths, which were of smolt size. The results from DNA metabarcoding of the scat samples require further investigation and validation. Telemetry tags were deployed on four harbour seals from the Donmouth haulout site. The tag data revealed that most of the seals spent their time travelling and foraging close to the coast. Only one seal spent time within the River Dee, and this was an individual that had already been identified and categorised as a regular user of the river. The tag data for this individual has provided further insight into the behaviour of seals that regularly use the river but that are not salmonid specialists. Skin samples from the four tagged seals were genotyped and results indicated that these seals most likely originated from more northern populations, e.g. Orkney, as opposed to populations in south east Scotland.

Management activities have focussed on the development of methods for catching river-using seals, developing monitoring methods and providing support to DSFBs for developing and evaluating management activities. A floating trap has been designed and constructed for catching seals within rivers. The deployment of this trap has been postponed due to several logistical constraints and therefore there has been no evaluation of its effectiveness. Catching at a seal haul-out at the Donmouth was however successful, resulting in the capture and tagging of four harbour seals.

It was agreed to pursue the development of a system to monitor for the presence of seals in stretches upriver of the tidal limit, and to allow for monitoring around the clock. A specification was drawn up with requirements for a video surveillance system. System components have now been purchased and will be constructed and evaluated as a seal monitoring tool.

A copy of the SSI annual report year 4 is available for download.

Current state of knowledge of effects of offshore renewable energy generation devices on marine mammals & research requirements. Update, September 2014

An initial review of the current state of knowledge on the effects of offshore renewable energy generators on marine mammals was provided to the Scottish Government in August 2013. This report provides an update to the 2013 report, highlighting improvements to the current state of knowledge of effects of offshore renewable energy generators on marine mammals and provides an update on progress on the prioritised list of research gaps presented in the previous report.

A total of 28 specific research gaps were identified in the previous report. Of these, 16 were at that time already under investigation to some extent with either active research projects or planned and funded future projects.

The 12 remaining projects were yet to secure funding. Of these, funding has been secured for two (AVOID and ARRY) and discussions are underway in relation to funding for a further two (TAG and MECH). The remainder remain unfunded. Largely the research priorities remain similar, but additional priorities that were not highlighted in the original report have been identified.

In parallel with this study, an analysis of research requirements for developing models to identify Population Consequences of Disturbance (PCOD) was carried out under the ORJIP programme. As part of this work, a number of research priorities were identified and this has been used to extend the list of research gaps and amend the priorities of specific projects in this update.

A copy of the updated final report MR1_and_MR2_update_VF1 is available for download.

The Scottish Government has the duty to ensure that the development of offshore renewable sectors is achieved in a sustainable manner in the seas around Scotland. There is a need to evaluate potential interactions between offshore renewables and marine wildlife as a matter of priority. One such potential interaction is the effect of underwater turbine generators on marine mammals. This report considers the possible technological methods for tracking fine scale underwater movements of marine mammals around marine tidal devices.

The target specification for interaction data as follows: a range of 100mof the turbine which have a temporal resolution of 1s and a spatial precision of 1m. These data requirements place a heavy demand on existing technology. However, we identify three generic methodologies that show potential: Animal-borne telemetry devices (tags), Passive sonar arrays to track animals that vocalise or that carry acoustic pingers, and Active sonar systems, the underwater equivalent of radar.

Animal-borne telemetry devices. These electronic ‘tags’ are attached to locally captured animals (acoustic pinger tags are discussed below). Capturing cetacea is not currently feasible and so this technique is limited to seals. The difficulty in recapturing individual tagged UK grey and harbours seals (within the six month attachment period) means that those type of tag which rely on retrieval for downloading data are not an option. The best option is a tag that relays surface GPS locations and detailed dive depth profiles through the mobile phone system (the GPS/GSM tag). GSM coverage is sufficient for most tidal devices areas. It is technically possible to incorporate dead reckoning (DR) so that the 3-D underwater track can be accurately generated in between surface GPS locations. The drawback is that water current data are required for this calculation at a level of detail that is not currently feasible.

Passive acoustic detection (PAM). PAM is essentially an array of hydrophones that can detect (to species level) and track vocalising animals (primarily toothed whales – especially porpoises and dolphins). A static array of hydrophones around a turbine should be capable of achieving the required level of precision. It is an unsatisfactory system for baleen whales that vocalise unpredictably. Whilst seals also do not regularly vocalise, they could be captured and fitted with individually coded acoustic ‘pinger’ tags. They would thus be capable of being tracked by a PAM system.

Active Sonar. Active sonar is akin to underwater acoustic radar. It has been proven to detect and track marine mammals in the vicinity of underwater turbines at sufficient spatial and temporal scales. It is good at detecting both seals and cetacea and viewing the raw data usually allows distinction between a seal and an odontocete. However we recommend that active sonar is used in conjunction with a PAM system, whereby the species (or individual, if acoustically tagged seals are used) discrimination is greatly improved. Active sonar is the only technology that will detect and track baleen whales.

To balance the strengths and weakness of the above technologies we suggest that the following generic configuration represents the best probability of achieving the overall objective:

Establish a static PAM array around one or more turbine to track vocalising odontocetes.

Tag local seals (c. 20+) with acoustic pingers so that they can also be detected and tracked by the PAM array.

Establish one or more active sonars on the turbine to detect and track all marine mammal species (including baleen whales). Generic discussions with engineers indicate that such an approach is feasible. However site-specific discussions have yet to take place.

Detection of a turbine blade actually striking a marine mammal is essential to interpret the consequences of fine scale movement. However none of the tracking technologies is likely to provide data sufficient to confidently discriminate an actual marine mammal strike from a near miss. Although high risk, we suggest that the feasibility of two possible approaches be explored. First, the physical detection of a strike using stress sensors built into the turbine blades. Second, the development of an underwater video surveillance system.

Appendix II of the report provides a case study of the proposed technology at the proposed Sound of Islay turbine array.

A copy of the final report, entitled MR3_Fine_scale, is available for download.

SMRU have had a close working relationship with various departments within Marine Scotland as well as with Scottish Natural Heritage and the Joint Nature Conservation Committee. This has previously been in the form of either informal discussions for short or easily answered questions or structured formal research contracts to answer more demanding or time consuming questions.   In developing the MMSS 001/11 research programme Marine Scotland identified a need for a flexible form of advice service that would be intermediate between these two approaches. It was required to still respond rapidly to new and emerging issues but to also be able to call on SMRU staff to respond to any questions related to marine mammals.   This task therefore aimed to deliver effective and timely advice (based on the best available information) to Marine Scotland and other public bodies upon request. The advice is based on the best available information to support Scottish Government requirements on issues relating to marine mammals and marine renewable developments.

A copy of the final report, entitled MR4_advice_function_VF1, is available for download.

This report describes seal density maps, produced by the Sea Mammal Research Unit, University of St Andrews as a deliverable of Scottish Government Marine Mammal Scientific Support Research Programme MMSS/001/11. The report outlines how the maps can be interpreted and the extent of their limitations with a set of caveats. Appendix 1 describes methodology and software used.

Grey seal (Halichoerus grypus) telemetry data from 1991-2011 and harbour seal (Phoca vitulina) telemetry data from 1991-2012 were combined with count data from 1988-2012 to produce UK-wide maps by species of estimated density and associated confidence intervals. The usage maps are available for download as GIS shape files from the Marine Scotland Interactive website (http://www.scotland.gov.uk/Topics/marine/science/MSInteractive/Themes).

MR5.1 At-sea usage and activity

MR5.2 Activity classification using state space modelling

The state-space model developed for defining activity budgets on a coarse resolution (6 hours) was used to define activity budgets at a fine temporal resolution (2 hours) based on both geo-centric and hydro-centric movements. Hydro-centric movements (active movement of seals through the water) were estimated by deleting vectors of current from the geographic movement data. ARGOS data were excluded because the temporal resolution of the location data prohibits the delineation of fine resolution activity budgets.

Activity budgets at a 2 hour resolution were successfully defined using the data from 90% of the 76 GPS/GSM tags considered. Problems apparent when defining activity budgets on the coarse resolution (including the estimation of only one diving state) appeared to be reduced when considering the fine resolution. Although there were some spatial differences in apparent foraging on the two resolutions, the activity budgets defined on the coarse resolution did not appear to be subject to consistent biases.

A significantly higher proportion of time was estimated to be devoted to foraging when hydro-centric rather than geo-centric movements were considered, indicating the importance of incorporating data on water movement when modelling activity budgets in marine animals.

MR5.3 Harbour seal haul-out monitoring, Sound of Islay

The purpose of this report is to provide an overview of the current techniques available for monitoring seal haul-out sites either at the Sound of Islay or at haul-out sites elsewhere.

This report builds on existing knowledge of harbour seal behaviour in the Sound of Islay and the South-East Islay Skerries SAC based on telemetry data collected in 2011 and 2012 with an assessment of data collected by GPS phone tags deployed in April 2014.

Controlled disturbance trials were carried out to assess the effect of disturbance by increased boat activity on haul-out behaviour. Concurrent monitoring of haul-out sites using remote camera systems recorded behavioural responses to trials, as well as giving daily seal counts at particular sites.

Modelling of transition probability indicated that controlled disturbance trials did not affect the probability of harbour seals transiting from one haul-out site to another. Seals generally displayed a high degree of site fidelity. The relationship between site fidelity and transition probability varied with whether seals hauled out again on the same or on a subsequent low tide period after a disturbance. Overall seals were more likely to transit from one haul-out site to another if the trip in between included at least one high tide period.

The results of this study suggest that increased boat activity during the construction phase of the proposed tidal turbine development will not cause individual seals to transit from one haul-out site to another. If seals are flushed from their haulout they are likely to return to the same haul-out site either during the same or on a subsequent low tide period. The recommendation of this report is therefore that monitoring effort to mitigate against any perceived risk of an increase in levels of disturbance by boat need only be on a local scale relative to any proposed development.

In light of these results a simple, time lapse photography based method of haulout monitoring that should provide sufficient information to identify and characterise any boat based disturbance events is described.

MR5.4 Inter-haul-out transition rates

The aim of this study was to predict the changes in the number of seals hauled at the South-East Islay Skerries Special Area of Conservation (EIS SAC) in response to disturbance at other haul-out sites.

Telemetry data from 25 harbour seals (Phoca vitulina), tagged between 2011 and 2014 at capture sites close to the Sound of Islay, were used to populate a movement model based on individual haul-out transition matrices. This model generalised the matrices in order to represent population movements. Disturbance was modelled as the serial permanent closure of one of the 35 haul-out sites used by the tagged seals. The model excluded movement during the breeding season. The modelled response was the change in numbers hauled out at the Ardmore haul-out site within in the EIS SAC. The varying effect of disturbing different haul-out sites reflected the complexity of the haul-out network.

Most disturbances had a positive effect of the number of seals at Ardmore (range: -0.5% to +21%). Haul-out sites with the largest effects were within 50 km of Ardmore and there was little or no effect when the disturbed site was more than 150 km away. However, the response was variable and within 50km distance did not predict which disturbed haul-outs affected Ardmore, as many sites within 50km had little or no effect. Thus the power to infer the effect of remote haulout disturbance by distance alone was limited, other than to say that the effect was greatest within 50 km of the haulout of interest.

However, within a range of 50km, the shortest network path between the disturbed haul-out site and Ardmore provided more information about which sites had an effect. Haul-out site networks adjacent to Ardmore (such as Machrihanish and Eilean nan Coinein) had a larger influence. There was no significant effect when a disturbed haul-out site was more than two transition jumps (connections) from Ardmore. Such network path information can be efficiently obtained in other areas with a simplified and cheaper telemetry system.

The effect of disturbance on the entire EIS SAC depended on the representativeness of the 25 tagged seals’ usage within the EIS SAC. The distribution of haul-outs in the August moult survey differed from the haulout usage of the tagged seals in this study. However, this may be due in part to redistribution during the breeding season. If the tagged seals were representative, the proportional effect of a disturbance to the EIS SAC would be similar. If, however, seals that used other haul-out sites in the EIS SAC were part of a completely different network of haul-out sites then the effect reported here would be reduced.

Whilst useful in this study, the model that was developed was essentially mechanistic. The limitations of this approach are reviewed and recommendations about future work using Individual Based Models are made.

Copies of the final reports, entitled MR5_Seal_density_maps, MR5-1_at-sea_usage_and_activity_VF2 MR5-2_activity_classification_using_state_space_modelling_VF2 and MR5-4_inter-haul-out_transition_rates_VF1 are available for download.

MR6.1 Review of methodology and main results of the JCP analysis of cetacean densities in the context of marine renewable development.

There are a number of potential issues affecting the populations of cetaceans living in or using UK waters. Without knowing the distribution and abundance of these animals the ability to assess how any of these issues could be affecting UK cetaceans is limited.

The revised Joint Cetacean Protocol (JCP) Phase III report attempted to estimate the abundance and distribution of cetaceans from a disparate data set of dedicated and platform of opportunity surveys. It also considered trends in cetacean abundance in the North Sea and waters out to the shelf-edge west of the UK and Ireland, also examining subareas within that area.

The modelling of the data involved sophisticated statistical methods and required various simplifications to be made. A formal model selection process was used but alternative models might produce very different estimates. It is recommended that work is carried out to explore whether moving to indices of abundance and/or maps of relative densities will simplify the model and reduce the risk of producing misleading results without compromising the results of the project.

For some species, the patterns identified by the models are inconsistent with other available sources of information. In particular, the JCP estimate for harbour porpoise abundance in 1994 is difficult to reconcile with that from the SCANS survey.

The JCP report contains many important caveats about the robustness and reliability of its results. It is not obvious that the results of the analyses it contains provide a suitable basis for the conservation and management of cetacean populations around the UK.

A copy of the final report, entitled MR6-1_review_of_JCP_VF2, is available for download.

MR6.2 Definition of ‘range’ in the context of marine renewable energy development and marine mammal conservation.

There are a number of potential issues affecting the populations of cetaceans living in or using UK waters. Without knowing the distribution and abundance of these animals the ability to assess how any of these issues could be affecting UK cetaceans are limited.

The area of sea, or range, specifically used by each cetacean species is an important factor when looking at issues such as Marine Renewable developments. If a development site falls within the natural range of a cetacean species, that species may be likely to be present and therefore collection of baseline data is of vital importance. However, the definition of a natural range, and whether a particular species is likely to be present at a particular site, is not straightforward as cetaceans may only be present at a site seasonally or sporadically because of their wide ranging movements.

There are a wide variety of techniques developed to explore the issue of animal range but not all of these may be suitable for cetaceans, and for some there are not adequate data. Further research will be necessary to ascertain whether there is enough existing cetacean sightings data to explore the utility of some of the measures that have been devised, and therefore to find a model that best serves the need to define the ‘natural range’ of these animals both within the context of the Habitats Directive and any other legislative obligations.

A copy of the final report, entitled MR6-2_define_range_VF2, is available for download.

Studies of harbour seal behaviour in areas of high tidal energy: Part 1. Movement and diving behaviour of harbour seals in Kyle Rhea.

The report presents a summary of the data collected during the initial transmitter deployments on harbour seals in the Kyle Rhea study area in 2012. As such it forms one of a series of interim reports describing the movements and diving behaviour of seals in areas of high tidal energy. It is designed simply to present the information most likely to be of use in assessing the potential impacts of any tidal turbine deployments in an easily accessible format.

Nine harbour seals caught and tagged at sites within the channel at Kyle Rhea. These seals were fitted with GPS equipped GSM phone tags that provided continuous tracking and dive behaviour data for a total of 506 seal days. The tagged seals concentrated their diving activity within the channel (57% of location fixes) at Kyle Rhea.

All of the seals tagged in Kyle Rhea swam repeatedly through the channel in the vicinity of the proposed turbine deployments. We present an example of how seals were distributed in the water column as they passed through one section of the channel. The filtered data shows a clear bimodal pattern in transits with respect to distance from the shore, with transits being less frequent in the central, deeper section of the channel. In addition, there appears to be a reduced density of transits in mid-water through the central deep channel. This would be an expected consequence of the dive profile patterns and has clear and important implications for estimating collision risk. However, the interpolation error due to timing of GPS fixes and the small but significant GPS position error mean that the transit depth and location data will still contain substantial error.

MR 7.1.1 Quantifying porpoise depth distributions and underwater behaviour in tidal rapids areas.

A vertical hydrophone array has been developed to provide new insights into harbour porpoise dive depths, underwater movements and echolocation behaviour in tidal habitats. This information is of direct relevance to understanding and reducing environmental impacts of tidal current driven turbines. Analysis of field data is on-going however we have demonstrated that it is possible to investigate the behaviour of porpoises in tidal areas using passive acoustics and further work is likely to yield reliable depth distributions.

A copy of the final report, entitled MR7-1-1_porpoise_depth_VF2, is available for download.

MR 7.1.2 The density and behaviour of marine mammals in tidal rapids.

Harbour porpoises (Phocoena phocoena) are one of Europe’s most common cetaceans and they are protected under European law. The current expansion of the tidal energy industry has highlighted concerns about anthropogenic activity in tidal habitats, particularly whether deployed turbines may pose a collision risk to animals. However, the ecological significance of tidal habitats for harbour porpoise is poorly understood and little data exists to inform on the potential risk that tidal turbines may pose. One key metric that needs to be measured to inform on this risk is the depth distribution of animals, for example, if harbour porpoises spend the majority of their time at the surface in tidal habitats then collision risk with deeper turbines will be very low. This report details the results of a three year project to develop, test and survey with a system capable of accurately determining the position of harbour porpoises underwater.

Determining the dive depths of animals is difficult. Tags are a possibility, however, there are no tagging programmes in the UK and the likelihood any one tagged animal would spend a significant time in tidal areas may be small. Passive acoustic monitoring (PAM) is a methodology which can detect the presence, classify the species and localise the position of animals, by listening to their vocalisations. Harbour porpoise use high frequency echolocation clicks almost continually for orientation, prey detection, navigation and social interactions, making them ideal candidates for studies using PAM. However, in order to achieve the accurate underwater tracking required to determine a depth distribution, a large dispersed array of multiple underwater receivers (hydrophones) is required.

Deploying such an array in a tidal habitat is difficult. Fixed structures would be inordinately expensive to deploy in areas with up to 8.5 knots of current and therefore a drifting hydrophone array was developed. The array consisted of 10-12 hydrophones, deployed between 3-45m underwater, from a small research vessel. The practical considerations for such a system are numerous; the array must be quickly recoverable and deployable, any movement underwater must be measured precisely and the delicate electronics used must be sufficiently rugged to remain operational in the particularly harsh environmental conditions present in tidal rips.

In addition to these considerations there are general issues with PAM. Porpoise have narrow beam profiles and hence are easy to miss if facing away from the hydrophone array. Noise and multiple animals clicking at the same time can also be problematic. Many of these issues were overcome by utilising new localisation and tracking methods developed during the project, however, difficulties remain in the fact that usually only fragments of tracks, rather than entire dive profiles, are detected. For the purposes of determining a depth distribution this information is adequate. However, it makes studies on the fine scale behaviour of animals more challenging.

Six tidal sites were surveyed over three years. Over 8514GB and 234 hours of data were collected resulting in 5210 tracks of animals. These were used to create depth distributions for each dive site. Two sites, Corryvreckan/the Great Race and Kyle Rhea contained by far the highest number of detected porpoise vocalisations per hour. Both sites are comparatively deep and porpoises had remarkably similar depth distributions during the day with animals spending 75% of time in the upper 38-40m of the water column. Kyle Rhea was the only site surveyed at night and showed a shift in the depth distribution, with animals spending more time in shallow waters.

The data summarised here provide the first substantial general dataset on porpoise depth distributions and underwater behaviour in tidal rapids. Given that virtually no data existed before, the data presented here can be used to improve collision risk estimates. However, the variation between sites evident in this dataset emphasises the importance of collecting data on a site by site basis.

The continual development of hardware, open source accessible software and PAM localisation methods during this project mean that a methodology now exists to determine depth distributions of harbour porpoises in tidal sites. However, this only forms a subset of the data required to inform on the ecological significance of such an area. Further work needs to focus on combining fine scale tracking of animals with visual/acoustic surveys and long term data recorders.

A copy of the final report, entitled MR7-1-2_porpoise_in_tidal_rapids_VF1, is available for download.

MR 7.2.1 Collision Risk: a brief review of available information on behaviour of mammals and birds in high tidal energy areas.

The large body of published literature focusing on the movement, habitat preference and behaviour of marine birds and mammals was examined for evidence of overlap of marine mammals and birds with sites with potential for tidal energy generation developments. From the review it is clear that there is a wide range of species that use areas of high tidal energy and there is confirmation of the overlap between ecologically important mammal and bird populations with possible tidal turbine sites.

A copy of the final report, entitled MR7-2-1_collision_risk_review_VF1, is available for download.

MR 7.2.2 Collision risk and impact study: Examination of models for estimating the risk of collisions between seals and tidal turbines.

The rate at which collisions can be expected to occur between marine mammals and tidal energy generation devices is potentially important to both the conservation of these species and the industry. Developers need to identify potential adverse effects of their proposed developments. For seals, this means demonstrating, among other things, that development and operation will not have an adverse effect upon the integrity of any SACs for which seals are a qualifying interest. Seals are seen as a particular problem in this respect because they frequent coastal locations where most tidal turbine developments have been proposed.

The major difficulty in estimating likely rates of collision is the lack of information on how animals will respond to active turbines. It is possible that they will be attracted, increasing their overall risk, though it seems more likely that they will avoid some potential collisions. Without such information, which is likely to be difficult to collect even once there are operational turbines, estimation is limited to encounter rates. Encounter rates are defined as the number of seals per unit time which turbines would strike if seals did not respond to the presence of the device. Those can be rescaled by assuming rates of avoidance, but that process will necessarily be approximate.

This report examines two models that have been proposed for estimating the rate at which seals can be expected to encounter tidal turbine blades. It also summarises a method that has been applied to calculate the risks to riverine fish from passing through hydroelectric power stations. The assumptions and implications of using the methods are discussed.

One approach was developed at SAMS Research Services Ltd (SRSL; Batty et al., 2012). It simplifies calculations by simplifying the shape of animals into spheres that would be of equivalent risk and assuming that animals’ speeds are independent of their direction relative to the turbine blade. The two versions of that model seem to have errors in the equations they present, but their overall intent is clear.

An alternative approach was a development of the Band model for the risk of birds being struck by wind turbines. That 2012 model assumed the animal’s motion was parallel to the axis of rotation of the turbine. Counterintuitively, the model’s representation of a “flapping bird” is a more appropriate approximation of a seal than is its “gliding bird” one. The model was broadly similar to the one presented by von Raben for fish passing through a hydroelectric power plant.

The two approaches produce broadly similar results from their different simplifications. Given the greater uncertainty in the animals’ responses, either could be used to give an estimate that will be less of an overestimate than simply estimating the number of animals likely to pass through the disc swept by a turbine rotor. If more detailed comparisons, such as between devices, are required, then a better estimate could be made by averaging the risks over an estimate of the likely joint distribution of animal speeds, directions and orientations throughout the tidal cycle.

In practice, the results of any assessments of overall risk are likely to be determined by the assumptions made about animals’ ability to avoid collisions. Until data on avoidance rates become available, further refinements of the models of encounter rates may be of limited value.

A copy of the final report, entitled MR7-2-2_collision_risk_impact_models_VF1, is available for download.

MR 7.2.3 Collision risk and impact study: Field tests of turbine blade-seal carcass collisions.

In the absence of any field data, collision risk models currently assume that all collisions between marine mammals and tidal turbines will be fatal. This precautionary assumption is not likely to be true and will lead to over-estimation of mortality rates. Estimated mortality rates are likely to be a serious constraint on turbine deployments and reducing the uncertainty should have the effect of reducing these rate estimates.

To address this issue a series of collision trials were carried out with grey seal (Halichoerus grypus) carcasses using a shaped, rigid bar fixed to the keel of a jet drive boat to simulate the leading edge of a turbine blade. The blade profile chosen represented a section near the tip where it is narrowest/sharpest and therefore most potentially damaging. The boat was driven at and collided with a number of previously frozen grey seal carcasses at a range of speeds. The angle at which the carcass was struck influenced the effective speed of that collision. This was accounted for by measuring the angle of the centre line of the keel to the water’s surface (which varied with the vessel’s speed) using video cameras and incorporating this into the effective speed calculations. Carcasses were impacted at a range of effective speeds from 1.95 m/s to 5.32 m/s. Resulting injuries were assessed via inspection of radiographs and by detailed post-mortem analysis. These data and the estimates of effective collision speeds were used to assess the likelihood of injury or death in real collisions.

Post-trial x-rays and post-mortems revealed no evidence of skeletal trauma. Neither were there obvious indicators of trauma such as tears, avulsions or rupture in the integument, musculature or organs, in any of the test subjects as a result of the collision trials. However, due to the difficulties in assessing soft tissue damage such as bruising and tissue oedema in previously frozen carcasses these soft tissue assessments were not considered reliable indicators of trauma in this experiment.

The results of the trials suggest that slow speed collisions with the tips of tidal turbines, at less than the maximum 5.32 m/s measured in this test, are unlikely to produce serious or fatal injuries in grey seals. It seems likely that a significant proportion of impacts would not be fatal, given the range of speeds tested in this set-up and the speeds with which wild seals will be exposed to when interacting with tidal turbines (see Data derived collision risk assessment). These are however, preliminary results and should be treated with caution as they are limited in their inability to assess soft-tissue damage or to determine potential unconsciousness as a result of collisions.

A copy of the final report, entitled MR7-2-3_collision_risk_impact_field_VF1, is available for download.

MR7.2.4 Data based estimates of collision risk: An example based on harbour seal tracking data around a proposed tidal turbine array in the Pentland Firth.

This report presents an estimate of the risk of collision between harbour seals (Phoca vitulina) and tidal turbines on the basis of observed behaviour patterns derived from targeted telemetry tracking studies and recent population survey data. The collision risk associated with a proposed turbine array development in the Pentland Firth was used as a worked example of the method.

A brief summary of the movement data collected during transmitter deployments on harbour seals in the Pentland Firth study area in 2011 was presented, with an emphasis on information that is most likely to be of use in assessing the potential impacts of tidal turbine deployments.

A process to estimate the number of times that telemetry tagged seals could pass through the area of the proposed turbine array was described. The method incorporates dive depth data to estimate the number of times tagged seals would have passed through the swept area of individual turbines in a hypothetical turbine array within the site.

Telemetry data from seals tagged at various sites in the Pentland Firth and Orkney was used to support an estimate of the number of seals likely to be at risk of interacting with such an array. The expected number of collisions between harbour seals and turbines in the array was based on details of their movements relative to the locations and movements of hypothetical tidal turbine blades, assuming that seals are oblivious to the presence of devices i.e. show no avoidance and take no evasive action.

1. • It was estimated that 1.2 seals per year (approx. 95% confidence interval (C.I.) 0.8- 2.0) would collide with individual turbines.
   • Scaling that estimate up to the full 86 turbine array suggested that 103 (approx. 95% C.I. 73 – 152) collisions would occur per year.
   • This estimate was approximately 15% of the rate derived from collision risk models for the same site.

The preliminary information from collision experiments was then used to give estimated mortality rates from such collisions. The effects of interpolation error due to timing of GPS fixes and the small, but significant, GPS position error on the estimates of interaction rates are discussed and an attempt is made to incorporate estimates of variability from other sources such as population estimates. Areas where such error distributions are poorly understood and require additional research are highlighted.

A copy of the final report, entitled scottish-natural-heritage-commissioned-report-no-900, is available for download.

MR 8.1 Tests of acoustic signals for aversive sound mitigation with harbour seals.

Some anthropogenic activities that produce intense sound in the marine environment present a risk of causing injury to the body tissues and auditory systems of sensitive marine life. It is an offence to kill or injure a seal under the Marine (Scotland) Act 2010 and in addition both grey and harbour seals are on Annex II of the Habitats Directive and are qualifying features for Special Areas of Conservation set up to promote their conservation. For these reasons, mitigation measures to minimise the risk of causing damage or injury are often a requirement when licences are issued to carry out risky activities in the marine environment. The traditional approach to mitigation is for observers to search for marine mammals (including seals) using visual and acoustic techniques, within a mitigation zone and to delay or halt risky activities if animals are detected. (A mitigation zone should be defined as an area within which animals are at an elevated risk of suffering damage. Joint Nature Conservation Committee (JNCC) guidance suggests that mitigation zones around piling should have a radius of at least 500m.) Such monitoring mitigation is unlikely to be fully effective when animals are difficult to sight at the surface and are rarely vocal, when mitigation ranges are large and when operations are required to continue in poor sighting conditions and at night. Mitigation monitoring can also be very costly to achieve at offshore sites. Aversive sound mitigation is a promising alternative or complimentary approach which would involve moving vulnerable animals out of the mitigation zone before activities such as pile driving commence, using appropriate aversive acoustic signals. In this project data was collected to assess how effectively aversive sound mitigation could be applied to harbour seals by conducting a series of controlled exposure experiments (CEEs).

Three sound sources (a Lofitech ADD, an Airmar ADD and broadcast killer whale calls) were assessed as potential sound sources for aversive sound mitigation. The findings suggest that, of the devices tested, the Lofitech ADD is the most effective at eliciting behavioural responses from harbour seals which should be useful for mitigation.

Our results show that out to a range of around a kilometre, all seals might be expected to show a readily identifiable change in behaviour. However, not all responses resulted in straight forward movement away from the sound source. Response also varied between CEEs in ways which may reflect the particular circumstances of the experiment as well as the motivation and status of the subjects.

Three observations from this work are particularly pertinent to those planning to use aversive sound mitigation. The first is the propensity for seals which are close to shore at the start of a CEE to move very close inshore and then move along shore in very shallow waters. This may well be a general and effective anti-predator response but the extent to which it would protect animals from exposure to intense sound needs further investigation. The second is the observation that animals that were traveling when faced with a CEE ahead of them would rarely reverse their tracks. More commonly they would “swerve” around the sound source, passing closer to it than the range at which avoidance behaviour was first noted and on occasion passing within a few hundred metres of it. Clearly, if this occurred during a mitigation exercise then animals might experience higher sound exposure. Studies should be carried out to investigate how animals respond to multiple sound sources in the field which could inform how they should be spaced to achieve effective mitigation. A final important observation is that animals apparently foraging within an area would often start to return to that area soon after a CEE. An implication of this for aversive sound mitigation is that the potentially damaging activity should start immediately after (or during) the mitigation broadcast.

It will be extremely difficult to measure behavioural response of seals to pile driving because any individual tagged animals would be unlikely to be close to pile driving when it started and it is not feasible to use or replicate pile driving as an experimental sound source. However, the observations made during this study of animals responding to what were clearly aversive signals may provide insights into how seals might react to pile driving.   Although seals showed an increase in speed during CEEs this was only modest. This limited response probably reflects energetic constraints on maximum sustainable swim speed which would also limit their escape speed from pile driving. The mean “escape” swim speeds observed during CEEs were lower than those assumed in some exposure models and, in contrast to the assumptions in most models, seals did not always swim directly away from the sound source. These considerations emphasise the desirability of moving animals to a “safe range” using a mitigation sound source whose characteristics can be controlled and measured beforehand using field CEEs.

A copy of the final report, entitled MR8-1_ADD_mitigation_VF2, is available for download.

MR 8.2 Sound Exposure Explorer Tool

The purpose of the Sound Exposure Explorer (SEE) is to provide a simple interactive utility which can be used to explore simple sound exposure scenarios, especially those involving cumulative exposures to moving animals. Using the tool, the cumulative exposure of animals can be calculated and plotted for different exposure scenarios; the “starting ranges” at which acoustic doses received over the course of an exposure scenario will exceed particular predetermined thresholds are also calculated. The intention is not to replace more sophisticated products which may incorporate complicated models of propagation loss and animal movements but to provide a straightforward, readily-understood and easy-to-use tool which can be used to make a first broad assessment of a sound exposure scenario and can provide a benchmark against which the conclusions from more complicated modelling exercises can be compared.

In its current form the utility focuses on the calculation of cumulative exposure for an animal which moves through a sound field created by one or more sound sources.

The conceptual framework of the SEE generally follows that laid out by Southall et al 2007 and many of the thresholds and parameters they propose are available as pre-set values or defaults within the utility.

SEE is open source; thus any developer can check or enhance the underlying Java source code. Our intention in planning and designing the SEE has been to provide a basic functionality within an architecture that will allow for future development and expansion as required.

A copy of the final report, entitled MR8-2_Sound_Exposure_Explorer_Tool2_Manual_VF1, is available for download.

Review of the status, trends and potential causes for the decline in abundance of harbour seals around the coast of Scotland.

A copy of the report CSD1-1_Review_of_potential_causes_for_harbour_seal_decline is available for download.

CSD 1.2 & CSD 2 Workshop report on decline in abundance of harbour seals around the coast of Scotland and discussion of mitigation and management measures

Workshop report on decline in abundance of harbour seals around the coast of Scotland and discussion of mitigation and management measures.

A copy of the updated report, entitled CSD1-2_and_CSD2_Workshop_report_on_decline_in_abundance_of_harbour_seals , is available for download.

CSD 3.1 Improved estimates of digestion correction factors and passage rates for harbour seal (Phoca vitulina) prey.

Harbour seal diet composition and diversity

Grey seal diet composition and prey consumption

CSD 3.4: Comparing the Diet of Harbour and Grey Seals in Scotland and Eastern England

CSD 4 Harbour seal decline: population modelling

CSD 5 Changes in at-sea foraging trips of harbour seals and grey seals in south-east Scotland

CSD 6 Harbour seal decline workshop II, 24^th April, 2014

This investigation was driven by the need to determine the cause of spiral lacerations in seals; a cause of death which has been reported with increasing incidence in the UK for the past decade. The purpose of this study was to demonstrate the ability of certain propulsion systems used on vessels to cause these types of injuries. The effect of animal size, propeller speed and propeller type on the occurrence of seal- propeller interactions was investigated. All trials were conducted with scale models of seals comprised of silicon rubber cores and wax outer layers.

A total of 59, 80 and 75 seal models were recorded and analysed for the ducted propeller, open propeller and Voith-Schneider propeller treatment groups respectively. Each propeller type was tested at four different rotation speeds and three model sizes representing different life stages were subjected to each speed. Only scale models which were subjected to a ducted propeller (a propeller fitted with a static housing) displayed characteristic injuries similar to those seen on stranded seals in the UK and Canada. Propeller speed was a significant factor in determining damage attributes, with slower speeds producing more spiral lacerations. Model size appeared to be unimportant in determining damage characteristics. Open propellers and Voith-Schneider propellers did not produce these patterns in any of the trials.

Ducted propulsion systems were the only mechanism which produced spiral lacerations under these test conditions. Consequently observations on candidate vessels are vital to gain a better understanding of the circumstances under which these interactions can occur in coastal regions. Viable mitigation can then be developed to reduce the number of cases and protect seal populations.

SSI Seals and wild salmon fisheries

This document reports on the progress made during 2014 with regard to marine mammal research at wild salmon fisheries. The objectives were: to continue studies into the effectiveness of Acoustic Deterrent Devices (ADDs) and the modification of salmon nets to mitigate the effects of seals on these fisheries; collect shot seals for dietary analysis and provide support to district salmon fishery boards (DSFBs). Activities primarily focused on two sites in the Moray Firth, Portmahomack and Crovie.

During 2013 the salmon net fishery at Portmahomack reported that seals were regularly seen at the net and that salmon landings were damaged by seals despite the use of an ADD. During 2014 seal sightings and salmon landings data were collected and photo-identification of seals from land-based photography was used to identify individual seals. Images were collected (n=1197) and all seal sightings at the net while the ADD was ‘on’ were attributed to adult male grey seals. Photo-identification revealed only two adult male grey seals were prepared to visit the salmon net while the ADD was ‘on’.

During 2013 tests began on the effectiveness of an ADD at Crovie. This work continued in 2014 through the collection and processing of underwater video footage to study the rate at which seals entered the net. The deployment of a C-POD was trialled to provide information on the presence of cetaceans during ADD ‘on’ and ‘off’ treatments; however, the elevated noise levels during ADD ‘on’ periods compromised the C-PODs ability to detect cetaceans. Dolphins and porpoises were regularly detected on the C-POD during ADD ‘off’ periods. Land-based observations recorded dolphins during both ADD ‘off’ and ‘on’ periods. Seal sightings were between five and six times higher during ADD ‘off’ periods compared to ADD ‘on’.

At Crovie in 2014 the evaluation of net modifications continued by examining the effectiveness of a different size of net entrance. Results from the 2014 study suggested that the new design increased salmon landings and reduced fish hesitation in the outer part of the net, an important aspect of reducing depredation from this area.

In April 2014 a report on the diet of seals shot at salmon nets from 2005 to 2013 was produced. The most frequently encountered prey was whitefish, sandeels and flatfish. However, an increase in the proportion of seals testing positive for salmonid DNA since the introduction of ADDs and net modifications may suggested that fewer ‘transient’ seals are now being shot with lethal control becoming more targeted to those consuming salmon.

Sea Mammal Research Unit (SMRU) personnel have continued to provide presentations on these studies and have provided support to river fisheries when requested. Where requests for support have been received this has led to the formation of a channel of communication between those working in river fisheries and SMRU that is beginning to form the basis for good collaborative work.

This project is continuing to produce encouraging results from the use of ADDs and net modifications at mitigating the effects of seals on these fisheries, and is maintaining positive and open relations with both net and river fisheries.

A copy of the report, entitled SSI_seals_and_salmon_VF1, is available to download.