Publication Abstract

A mark-recapture approach to estimating population density from continuous trapping data: application to edible crabs, Cancer pagurus, on the east coast of England

A mark recapture approach to estimating population density from continuous trapping data: application to edible crabs

M.C. Bell, D.R. Eaton, R.C.A. Bannister and J.T. Addison

We develop a mark- recapture approach to estimating population density from continuous trapping data. The method incorporates flexibility to allow for sampling difficulties encountered in real field experiments, such as unequal sampling intervals and incomplete sampling of the gear. A short-term mark-recapture experiment is described, aimed at estimating density of edible crabs, Cancer pagurus, on an offshore bank on the Englishg east coast. More than 3,000 crabs were marked with paint and sampled using baited traps of standard commercial design. We apply ythe mark-recapture model to estimate probabilities of capture and fidelity to the experimental capture area, and therby estimate the size of the local population from the total catch data. A local population of 4,800 crabs is estimated to exist in a capture area of 2.3km2, giving an extimated density of 2,100 crabs. km-2. Bootstrapping is used to show that temporal variation is much more importannt than spatial variation as a component of uncertainty in density estimates. Experimental catch data are used to draw inferences about the relationship between trap soak time and effective fishing effort. Problems of interpretation of density estimates at the population level are discussed.

Reference:

M.C. Bell, D.R. Eaton, R.C.A. Bannister and J.T. Addison (2003) A mark recapture approach to estimating population density from continuous trapping data: application to edible crabs. Fisheries Research, (1-3)65: 361-378

M.C. Bell*, D.R. Eaton*, R.C.A. Bannister* and J.T. Addison*

Fisheries Research, (1-3)65: 361-378