Evaluating age and length composition data for inference about selectivity shape

Age and length composition data for Georges Bank Yellowtail Flounder from three fisheries independent surveys and from the commercial catch at age were examined to determine whether there was sufficient information to infer selectivity shape outside of the VPA model application. Age and length composition supported the same conclusions about relative selectivity between the NMFS spring, NMFS fall, and DFO surveys. Specifically, the DFO survey appears to have dome-shaped selectivity, the NMFS spring survey has higher selectivity than the DFO survey at the oldest ages, and the NMFS fall survey has the greatest selectivity (over all 3 surveys) at the youngest ages. The NMFS fall survey does not always observe the oldest age (6), so the relative selectivity pattern was not as informative about this age class. The DFO survey had relative selectivity patterns that were most similar to the fishery. This would suggest that there might be some doming expected for the fishery selectivity. Two alternative VPA configurations were explored to determine if configurations with doming in the fishery could help resolve the severe retrospective pattern; the dome models reduced the retro slightly, but the magnitude was still very large. 2014 TRAC Transboundary Resource Assessment Committee Working Paper 2014/17 NMFS (National Marine Fisheries Service) NEFSC (Northeast Fisheries Science Center) Submitted Public Domain 1862