Publication Abstract

A reanalysis of North Sea plaice spawning stock biomass from 1948 to 2004 using the annual egg production method.

Damme, C.J.G. van, Bolle, L.J., Fox, C.J. Fossum, P., Kraus, G., Munk, P., Rohlf, N., Witthames, P.R. and Dickey-Collas, M.

There is uncertainty about the quality of current VPA-based stock assessment for North Sea plaice. This is partly caused by the impact of discarding of unwanted catch and failure to account for spatial dynamics of the stock. It is difficult to develop robust stock assessment methods which account for these factors. Biomass estimates from the Annual Egg Production (AEP) Method are compared to current catch-at-age based stock assessments to validate the current and historic perception of exploitation. The AEP method also allows us to investigate the dynamics of the spatial components of plaice in the North Sea. Importantly, we show for fecundity down regulation and changes in sex ratio. Estimates from both methods are similar in trend and absolute biomass. On the Dogger back there has been a dramatic decline from the 1940s to 2004, and in the Southern Bight the stock appears to increase from the 1980s to 2004, but not yet up to the biomass of the 1940s. There appears to be no major change in timing of spawning of North Sea plaice, throughout the period of high exploitation. We conclude that the AEP method is a useful way to hindcast spatial dynamics of heavily exploited flatfish stocks.

Reference

Damme, C.J.G. van, Bolle, L.J., Fox, C.J. Fossum, P., Kraus, G., Munk, P., Rohlf, N., Witthames, P.R. and Dickey-Collas, M. (2009) A reanalysis of North Sea plaice spawning stock biomass from 1948 to 2004 using the annual egg production method. ICES Journal of Marine Science  66(9):1911-2011