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MSY objectives are being adopted as major fisheries management targets worldwide. However, in fisheries where discards account for an important share of the catches, the yield, effort, and biomass at MSY can be significantly different when accounting or not for discards and thus when, basing the yield estimations on landings or catches. Also whether accounting for a certain survival rate, of discards can lead to different MSY targets estimates. Hence, both decisions have important, implications on catch and effort reduction recommendations, and consequently on the quota, calculations for fisheries managed by quotas. Results from the Bay of Biscay nephrops fishery confirm, that the optimal exploitation level can vary significantly when optimising for catches or landings, and, by assuming a certain survival rate of the discards. By doing this, the present study also allows to, explore the basis to clarify the definition of MSY in fisheries where discarding takes place. [ABSTRACT FROM AUTHOR]

This article investigates the relationship between optimal gear selectivity and effort cost in the fishing industry. We first show that optimal selectivity depends negatively on the level of effort cost, but that this relationship is not continuous. Optimal selectivity switches when real effort cost goes beyond a certain level, and this switch induces a non-marginal reduction in the level of fishing effort. In the second part of this article, we show that the current level of real effort cost in the Nnephrops fishery of the Bay of Biscay is far below the switch point, which makes high selectivity optimal. The discrepancy between optimal and current selectivity may be explained by the state of the fishery management and also by the fact that selectivity is hardly observable with the type of gear presently used. [ABSTRACT FROM AUTHOR]