An incidental catch model for porbeagle assessment and status evaluation

Fisheries landings and associated biological data collection for porbeagle shark (Lamna nasus) declined substantially following CITES Appendix II trade restrictions in 2013 due to changes in fleet behavior. This document describes a new stock assessment method that can be used when length-frequency data and CPUE series are not available or reliable for index changes in abundance. The Incidental Catch Model (ICM) is based on the same general premise as datapoor, length-based assessments, in that it uses life history information and equilibrium assumptions to derive a theoretical age-structured population in the absence of fishing. In the ICM, the effect of historical fishing pressure on productivity is taken into account prior to evaluating fishery removals and abundance relative to reference points. The Northwest Atlantic stock was used to demonstrate the method, which can be adapted to assess stocks in the Northeast and South Atlantic by changing life history inputs and the removals series.