ANALYSIS OF LENGTH FREQUENCY SAMPLES WITH RELATIVE ABUNDANCE DATA FOR THE GULF OF MAINE NORTHERN SHRIMP (PANDALUS-BOREALIS) BY THE MULTIFAN METHOD

We present an extension of the MULTIFAN method for simultaneously analyzing several length frequency data sets from length frequency data collected by research trawl surveys. The assumption that the research trawl samples the animals in a regular fashion allows the proportions at age in the samples to be parameterized in terms of relative year class strengths and the age-dependent selectivity of the sampling procedure. When available, relative abundance data can be incorporated into the analysis and permit the estimation of mortality. The method is applied to Gulf of Maine northern shrimp (Pandalus borealis) data. The parameter estimates obtained agree substantially with those previously obtained using a more detailed knowledge of the species' biology.