Survey estimates of king crab (Paralithodes camtschaticus) abundance off Northern Norway using GLMs within a mixed generalized gamma-binomial model and Bayesian inference

• Published in: ICES Journal of Marine Science
• Main Authors: Hvingel, C., Kingsley, M. C. S., Sundet, J. H.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Oxford University Press (OUP) 2012
• Subjects: Ecology; Aquatic Science; Ecology, Evolution, Behavior and Systematics; Oceanography; Norway; Sundet; Northern Norway; Paralithodes camtschaticus
• Online Access: http://dx.doi.org/10.1093/icesjms/fss116; http://academic.oup.com/icesjms/article-pdf/69/8/1416/29144748/fss116.pdf

Abstract Hvingel, C., Kingsley, M.C.S., and Sundet, J.H. 2012. Survey estimates of king crab (Paralithodes camtschaticus) abundance off Northern Norway using GLMs within a mixed generalized gamma-binomial model and Bayesian inference. – ICES Journal of Marine Science, 69: . A trawl survey provides information on number and biomass of introduced king crab (Paralithodes camtschaticus) to the management of a fishery off the coast of Northern Norway; the annual catch quotas are largely set as a percentage of the survey estimate. A specially built sledge trawl was designed for the survey. It needs only small areas of trawlable bottom, performs well on a wide range of bottoms, and appears to have good catchability for benthic organisms. Many survey hauls catch no crabs and the non-zero catches have a highly skewed distribution. Data were therefore analysed with a compound model, in which separate predictors were fitted for the proportion of zero catches and for the catch size of the non-zero catches. The compound model was fitted by Bayesian methods using WinBUGS. The distribution of non-zero catches fitted well to a generalized gamma distribution, but with parameter values that made it approximate a lognormal distribution. Numbers of fishable crabs peaked in 2003, and total numbers in 2010 were about two-fifths of the 2003 maximum.