Reproduction and stock evaluation for recovery
The traditional stock-recruitment models assume that spawning stock biomass is proportional to reproductive potential, which implies that the survival chances of progeny does not change with age or size of the parents. However, the reproductive potential of a population is a measure of the capacity of the population to produce viable eggs and larvae in a given year. This concept goes beyond the simple estimation of spawning stock biomass.
Recent studies indicate that, for a given population, larger individuals have different reproductive attributes than smaller fish. Moreover, a population consisting solely of the smaller fish is seldom able to compensate the loss of reproductive potential associated with the disappearance of the larger individuals due to fishing. As a response to this change in perception, it is now important to consider reproductive potential in relation to population demographics in cod and hake recovery plans. The present very low number of spawning fish strengthens this view.
New and existing methods will be developed and evaluated to reduce the cost and improve the accuracy of estimating realised fecundity, previous spawning activity and reproductive potential. The preferred methodology will be applied to samples of cod and Northern hake collected across a large part of their distribution in European shelf edge waters. These results will provide the first comprehensive data set on reproductive potential of these species in relation to biological reference points and stock demography.
The overall objective is to measure the reproductive potential of cod and Northern hake throughout their latitudinal range, applying enhanced methods developed during the project, to simulate complex stock dynamics using the revised biological reference points and fisheries interactions on management options for stock recovery.
Development of more cost-effective and precise methods to estimate reproductive potential.
Assessment of reproductive potential over the latitudinal range of cod and Northern hake in relation to the environment.
Application of simulation models to assess complex stock dynamics fisheries and management procedures.
Determine the sensitivity of previous fishery independent spawning biomass assessment to inclusion of experimentally determined estimates of atretic follicle stage duration.
Assess the cost benefit of a fisheries independent hake survey
Scientist responsible for the project
Marine Environment Director OLE ARVE MISUND
Nordnesgaten 50 Box 1870
Norway - NO
Phone: +47 55238497
Fax: +47 55238584
||INSTITUTO OF MARINE RESEARCH
||01 October 2002
||4 234 752 €
|Total EC contribution
||1 000 000 €
|Web address of the project