ICES Journal of Marine Science: Journal du Conseil Advance Access originally published online on March 4, 2009
ICES Journal of Marine Science: Journal du Conseil 2009 66(4):665-679; doi:10.1093/icesjms/fsp038
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Bayesian survey-based assessment of North Sea plaice (Pleuronectes platessa): extracting integrated signals from multiple surveys
1 Wageningen IMARES, Institute for Marine Resources and Ecosystem Studies, PO Box 68, 1970 AB IJmuiden, The Netherlands
2 Aquaculture and Fisheries Group, Wageningen University, PO Box 338, 6700 AH Wageningen, The Netherlands
3 Present address: Marine Institute, Rinville, Oranmore, Co. Galway, Ireland
Correspondence to A. D. Rijnsdorp: tel: +31 317 487191; fax: +31 317 487326; e-mail: adriaan.rijnsdorp{at}wur.nl.
Bogaards, J. A., Kraak, S. B. M., and Rijnsdorp, A. D. 2009. Bayesian survey-based assessment of North Sea plaice (Pleuronectes platessa): extracting integrated signals from multiple surveys. – ICES Journal of Marine Science, 66: 665–679.Dependence on a relatively small sample size is generally viewed as a big disadvantage for survey-based assessments. We propose an integrated catch-at-age model for research vessel data derived from multiple surveys, and illustrate its utility in estimating trends in North Sea plaice abundance and fishing mortality. Parameter estimates were obtained by Bayesian analysis, which allows for estimation of uncertainty in model parameters attributable to measurement error. Model results indicated constant fishing selectivity over the distribution area of the North Sea plaice stock, with decreased selectivity at older age. Whereas separate analyses of survey datasets suggested different biomass trends in the southeast than in the western and central North Sea, a combined analysis demonstrated that the observations in both subareas were compatible and that spawning-stock biomass has been increasing over the period 1996–2005. The annual proportion of fish that dispersed in a northwesterly direction was estimated to increase from about 10% at age 2 to 33% at age 5 and older. We also found higher fishing mortality rates than reported in ICES assessments, which could be the consequence of inadequate specification of catchability-at-age in this study or underestimated fishing mortality by the conventional ICES assessment, which relies on official landings figures.
Keywords: Bayesian statistics, plaice, population dynamics, state-space models, survey-based assessment
Received 16 May 2008; accepted 5 February 2009; advance access publication 4 March 2009.
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