Shellfish Committee Activities Report 1992

The Activities Report continues as an important summary of the work done by ICES countries in the shellfish field. There are unfortunately some gaps this year due mainly to pressure of work or institutional changes affecting some participants. but I hope these will be remedied in the future. In some countries funding for research is becoming tighter. but as an antidote it is all the more pleasurable to reward the increasing diversity of work emerging from other countries such as Spain.
Because of travel constraints it is not always possible for ICES workers to meet each year at the Statutory Meeting. I hope members of the Shellfish Committee will therefore use the Activities Report as a key to making informal contacts intersessionally.
Recent changes in some shellfish stocks highlight the fact that as with finfish we still have a very poor knowledge of the factors affecting recruitment. Thus. on the east coast of Canada and the USA, there has been a dramatic increase in the landings of the American lobster Homarus americanus, in almost all fishery districts. In some areas landings have reached the highest level this century. Fishing effort is high. even increasing, and this may have contributed, but there must clearly be some stock for the extra effort to exploit. and there is little doubt that a major recruitment pulse has occurred recently. Although we hypothesise that temperature and larval transport are likely key factors in determining recruit success, the precise cause of the pulse of lobster recruitment is unknown. In contrast. the last few years have seen a run of poor spatfalls of the cockle (Cerastoderma edule) and blue musseI (Mytilus edulis) in estuaries on the southern and western edges of the North Sea. Speculation centres round the level of spawning stock. the role of winter temperature. and possible effects of predators such as the shore crab. but again the mechanisms have not been worked out fully.
In the Channel, recruitment of the scallop. Pecten maximus, remains patchy and episodic. but the crustacean fisheries have recently benefited from good recruitment of Maja squinado (after some poor years) and of Palinurus elephas, whose juvenile abundance south west of Britain has been higher than for many years. Finally, in the southern North Sea, the brown shrimp, Crangon crangon, which has supported a combination of industrial fishing and consumption shrimp fishing for many many years, is now giving cause for some concern, since landings have begun to decrease in the last decade.
These are all examples where our ability to explain changes is handicapped by our poor knowledge of how environmental trends, fishing effort. intrinsic populations dynamics. and transport processes, interact to determine recruitment and abundance. I hope ICES shellfish workers will think carefully about the wide ranging programmes required to tackle some of these problems.