Research Document - 2014/106
Exploratory analysis of the NFT ADAPT SPA model for the west coast of Newfoundland herring stocks, 2000-2013
By François Grégoire, Linda Girard, Jean-Louis Beaulieu and Benoit Légaré
Abstract
In this study, exploratory Sequential Population Analysis (SPA) models were applied on the two Atlantic herring (Clupea harengus harengus L.) stocks of the west coast of Newfoundland (NAFO Division 4R). Calibration of these models was performed using an abundance index from four acoustic surveys conducted between 2009 and 2013. Several of the abundances at age predicted by the SPA were similar to the abundances estimated by the surveys. However, significant differences were observed for certain age groups. Residuals of the SPA models presented annual patterns and no convergence for younger ages due to the low number of surveys. The low number of surveys is also responsible for the retrospective patterns that were observed for all of the parameters estimated by the SPA. In light of these results, it was agreed to reject the SPA. However, it is recommended to continue the series of acoustic surveys in order to achieve as soon as possible full and rigorous analytical assessments and to update the limit reference points established in the early 2000s.
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