SMRU > Research > Fishery Interactions
Marine mammals have for a long time been viewed in some quarters as serious competitors with fisheries. Indeed this is one of the main reasons cited by whaling nations as to why they need to keep whaling. At the individual level, marine mammals are also frequently unintentionally caught in fishing activities, and the cumulative effects of these bycatches at the population level can in some cases be severe. In many areas individual marine mammals also cause damage to fishing operations and to aquaculture by removing fish from nets, hooks and fish traps. In fact marine mammals probably interact with fisheries to a much greater extent than is immediately obvious, taking advantage of the ready availability of fish that are being herded or caught by fishing gear.
Competition with fisheries and ecosystem level interactions with fisheries involve looking at fishery catch and landings data as well as stock abundance data. This means that we have to collaborate with colleagues in fishery laboratories in the UK and elsewhere where such data are collated. Modelling the interactions also requires detailed information on the feeding habits and density of marine mammals in different areas, and may also involve using information from tagging or sightings programmes to make inferences about seasonal movements.
Studies on by-catch revolve around making observations of fishing operations on board commercial fishing vessels, and where it is deemed necessary, helping the fishing industry to minimise the frequency of such events. Likewise, where marine mammal depredations are considered an economic threat, it may be necessary to find ways of deterring them from specific fishing gears. Most such exercises involve tests by trial and error in the field.
Phil Hammond and Simon Northridge contribute to the work of the Scientific Committee of the International Whaling Commission on whale fishery interactions.
Sophie Smout and John Harwood have looked at the dynamics of diet in response to changing fish availability.
Simon Northridge has been running a UK wide monitoring programme looking at marine mammals bycatch for many years, and has also been involved in testing and developing bycatch mitigations measures in collaboration with the fishing industry. The issue of depredation has also been addressed by measuring the impact of marine mammals on fishing gear, and trialling deterrent measures.