Effect of population structure, sampling strategy and sample size on theestimates of selection parameters for shrimp (Crangon crangon) trawls

摘要

In selectivity experiments with shrimp trawls, very high numbers of animals in the catches of single hauls are a common feature and therefore, sub-sampling is inevitable. In order to find an acceptable balance between work-load and accuracy in the estimation of the selection parameters, it is important to have a sensible idea on the minimum numbers of shrimps to be measured in each catch fraction (cover, discards and landings). The present theoretical study tries to answer this question by means of computer simulations of different sampling strategies and sample sizes applied to catches with known size compositions.