Behavioral inferences from the statistical distribution of commercial catch: patterns of targeting in the landings of the Dutch beam trawler fleet

The objective identification of targeting behavior in multispecies fisheries is critical to the development and evaluation of management measures. Here, we illustrate how the statistical distribution of commercial catches can provide information on species preference that is consistent with economic data but not a simple function of price. Using the Dutch beam trawl fishery from 1998 to 2003, we show that the distribution of the log10-transformed catch rates of preferred species exhibit greater negative skews than less preferred species. Furthermore, subsets of the fleet employing spatially distinct strategies generate the expected patterns in the skews of their catch distributions. A simple model is presented to illustrate a behavioral mechanism for variation in skews and identify circumstances where it could apply. As a result of this analysis we propose that (i) catch distributions should be examined by species when investigating targeting behavior and (ii) changes in error structure over time can be expected in comparisons of catch statistics such as those used to create abundance indices or estimate fishing power.