Publication Abstract

Managing the exploitaion of migratorysalmonids.

E.C.E. Potter, J.C. Maclean, R.J.Wyatt and R.N.B. Campbell

The control of exploitation in fisheries forAtlantic salmon (Salmo salar L.) and trout (S. trutta L.) has both biological and socio-economic objectives,the former relating to the protection of the productive capacity and diversity of theresource and the latter to issues such as the allocation of any harvestable surplus todifferent user groups. In fulfilling the biological aims, managers can restrict catches or fishing effort to ensurethat sufficient fish from each population are permitted to spawn; they may alsoconsider options for increasing the production of the stock, such as habitat improvementor stocking. Biological reference points (e.g. limits and targets) are increasingly beingused to provide an objective measure of the status of stocks and determine the possibleneed for management actions, although a range of other stock indicators may be required tofully protect the diversity of our stocks. This is consistent with the application of aprecautionary approach to salmon fishery management as adopted by the North AtlanticSalmon Conservation Organisation (NASCO). NASCO has agreed that a limit reference point(or conservation limit) for Atlantic salmon should be set at the spawning stock size thatwill give maximum sustainable yield (S_MSY).Fisheries should therefore be managedto ensure that there is a high probability that these limits are exceeded, and actualescapement should usually be higher than these thresholds. NASCO has proposed that stocksshould be maintained above their conservation limits by setting higher, and thus moreprecautionary, management targets, although alternative approaches are possible. ICES andNASCO have favoured a fixed escapement strategy for the management of salmon fisheries,although in practice, this strategy is being implemented in a variety of ways. In manyfisheries, approaches more akin to `floor policies' or `proportional threshold harvesting^'are being employed although the merits of different strategies for the management ofcommercial and recreational salmon fisheries have yet to be fully explored. Scientistsstill have some way to go in fully incorporating uncertainty into their management advice,but the objective must be to utilise the bestinformation available to them, regardless of its imperfections, in developing managementoptions and to account explicitly in their advice for the various sources ofuncertainty both in the current state of scientific knowledge and in our ability tocontrol fisheries. These management approaches have mainly been developed for themanagement of Atlantic salmon, but there would clearly be merits in developing similarapproaches to protect production of both migratory and non-migratory trout stocks.

Reference:

E.C.E. Potter, J.C. Maclean, R.J.Wyatt and R.N.B. Campbell. 2003. Managing the exploitaionof migratory salmonids. Fisheries Research, 62 (2): 127-142.