Research Document - 2010/015
Trends in Northwest Atlantic Fisheries Organization (NAFO) Subdivision 3Ps Cod (Gadus morhua) stock size based on a separable total mortality model and the Fisheries and Oceans Canada Research Vessel survey index
By N. Cadigan
Abstract
We describe a cohort model based on a separable total mortality assumption that can be fitted using only survey information. It is very similar to the SURBA model (see Needle 2008; Mesnil et al. 2009). The model produces relative estimates of stock size but absolute estimates of total mortality. We apply the model to the DFO RV survey age-based indices of abundance for 3Ps cod. This application was presented at the 2009 winter cod ZAP using data for 1983 to 2008, and the Fall 2009 3Ps RAP using data for 1983-2009. Both analyses indicated that there were substantial risks that SSB in the last assessment year (either 2008 for the ZAP or 2009 for the RAP) was below the limit reference point for 3Ps cod.
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