Application of Some Index Methods to Georges Bank Yellowtail Flounder

Simple graphical and empirical methods are used to examine the relationships between relative abundance and estimated catch of Georges Bank Yellowtail Flounder for three different synoptic surveys over the period 1963 to 2013. All three surveys reveal similar trends in abundance and relative fishing mortality. Kalman filtered estimates appear to be a useful way of summarizing trends and have strong similarities to model based estimates. Measures of relative fishing mortality increased steadily up through 1994, fell sharply in 1995 and have declined since then. Relative biomass increased rapidly for about 8 to 10 years after the decline in F, but has since declined, despite continued reductions in relative F. The simple model results suggest a change in underlying relationship between abundance and exploitation. While aggregated data used in this analysis are insufficient to identify the underlying cause, the large changes suggest that any model will have diagnostic problems unless an underlying mechanism for the change is incorporated into the model. 2014 TRAC Transboundary Resource Assessment Committee Reference Document 2014/ NMFS (National Marine Fisheries Service) NEFSC (Northeast Fisheries Science Center) Submitted Public Domain 1861