Can we estimate the catch of NE Atlantic Mackerel?

Speaker: John Simmonds FRS (Marine Lab Aberdeen)

During the last five years it has become increasingly apparent that there has been underreporting of landings of NE Atlantic Mackerel. The stock which occupies an area along the shelf break from Portugal to Norway is currently fished by 14 European nations, in national and international waters. In 2005 regulatory authorities in UK and Ireland have investigated vessel landings and processing factory records. The results from UK indicate that landings in to UK have exceeded reported landings and the additional quantities found in this single country amount to between 8-10% of the total quota allocated to all countries. NEAFC, (North Eastern Atlantic Fisheries Commission) the management body for this stock has asked ICES to evaluate the extent of estimates of unaccounted mortality in fisheries for NEA mackerel to provide estimates of historic Spawning Stock Biomass and Fishing Mortality that would be compatible with these estimates of unaccounted mortality. Annual age structured data from the fishery, five triennial egg surveys and 19 years of tag and recovery data on total mortality at age have been used in a WINBUGS based population model, to try to estimate total mortality and fishing mortality for this stock. The model is a development of the population model currently used for the annual assessments. The estimates of unknown removals from the stock are presented and the sensitivity of these to the different models are explored. These results are presented in the context of Bayesian P values and DIC criteria. The influence of different sources of data are discussed to see if further work might be justified. The form of final conclusions are discussed.