Research Document - 2012/120
Exploratory analysis of the NFT ADAPT SPA model for the west coast of Newfoundland herring stocks, 2000-2011
By F. Grégoire and J.-L. Beaulieu
Abstract
Exploratory Sequential Population Analysis (SPA) models were applied to the fishery and stock dynamics data of the west coast of Newfoundland herring. Calibration of these models was performed using an abundance index from three acoustic surveys conducted between 2009 and 2011. Despite the small number of surveys, results similar to previous assessments were obtained for the years covered by the two models. However, adjustment problems were observed for some age groups due to the small number of surveys and possibly to age reading problems. The exploratory models suggest that the spawning biomasses have been decreasing since 2001 for the spring spawners and since 2006 for the fall spawners. The fishing mortalities would be decreasing since 2009 for the spring spawners and increasing since 2004 for the fall spawners. The next steps consist in continuing the acoustic survey series, rebuilding credible analytical assessments, and updating the limit reference points. These steps are essential in sight of the purse seine fishery certification.
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