Working Group on Marine Mammal Ecology (WGMME)

The Working Group on Marine Mammal Ecology met in 2022 to address five terms of reference. Under the first of these, ToR A, new information on cetacean and seal population abundance, distribution, population/stock structure, was reviewed, including information on vagrant marine mammal species. This was done to ensure the recording of possible range changes in marine mammal species in the future. 

For cetaceans, an update is given for the different species, providing for a latest estimate for all species studies. In this report, particular attention is given to the updating of information from Canadian and US waters, and together with those countries, latest estimates for cetacean species are provided. For seals, latest monitoring results are given for harbour, grey and Baltic ringed seals. In addition, where possible, local long-term trends are illustrated for those species, based on earlier WGMME efforts to assemble these data into the WGMME seal database. For both species’ groups, a first account of vagrant species is provided

Unlike earlier reports, cetacean and seal management frameworks in the North Atlantic were discussed under ToR B, where an overview is given including local management frameworks and regional conventions regarding marine mammals. Also, implications of the new US Marine Mammal Protection Act import provisions rule were examined.

ToR C provides an overview of new published information with regards to anthropogenic threats to marine mammal populations following on from the review by WGMME in 2015 (ICES, 2015) and subsequent updates. These are considered under the following headings: cumulative effects, fishery interactions, chemical pollution, marine debris, underwater noise, ship strikes and other physical trauma, tourism, and climate change.

ToR D is a collaboration with WGBIODIV to identify foraging areas and estimate prey consumption by harbour seal, grey seal and harbour porpoise in the North Sea case study area. WGBIODV plans to further develop multi species models in the North Sea including large predators and needs information on diet preference for the different species. Based on WGMME 2021, caveats and limitations that may affect the use of these data are explained and were obtained to pilot sample datasets to illustrate the available data. There is a need for comparative studies to calibrate the estimates derived from these different methods, and develop new methods such as the use of DNA. The group expects shifts in the diet of marine top predators and therefore the necessity to ameliorate methods to study this. A workshop on diet studies to be held in association with other relevant bodies in 2023 is suggested to ensure comparable methods are used. 

ToR E is in collaboration with WGBYC to contribute to the Roadmap for ICES PETS bycatch advice. This is done by reviewing aspects of marine mammal-fishery interactions which are not fully covered by WGBYC (notably strandings) on marine mammals. The results of the questionnaire held in 2021 are presented, reviewing the benefits and limitations for using strandings to determine bycatch rates, how best procedures can be improved, whilst identify-ing the need for better reporting of strandings of seals across the region. The group suggests to (i) develop a best-practice manual or framework on marine mammal strandings to inform bycatch assessment. This could be published as a CRR; (ii) to develop a data call and database for such data; and (iii) to organise a workshop or workshops to develop (i) and (ii) above.