Research Document - 2013/102
Recovery Potential Modelling of Anticosti Island Atlantic salmon (Salmo salar) metapopulation
By M. Brun and É. Prévost
Abstract
In 2010, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) designated the Anticosti Island (Designatable Unit 9) Atlantic salmon (Salmo salar) population as an endangered species in Canada. This document presents population modelling to determine population-based recovery targets and conduct long-term projections of population recovery in support of a recovery potential assessment (RPA). The modelling work was done in two parts. A first report in February 2012 was designed to assess changes from 1984 to 2011, the current situation and the recent trajectory of this metapopulation in terms of total adult abundance and its distribution in the 25 Anticosti Island salmon rivers. A second report was presented in December 2012 to assess the metapopulation's chances of recovery, when this will be achieved and exploitation rates that will not compromise the survival or recovery of the species. The final model also includes the most recent data available, i.e. 2012 data.
The review of the Anticosti Island metapopulation's trajectory from 1993 to 2011 confirmed the decrease in the number of adults indicated by COSEWIC (2011), with an average overall decrease of 43% (42.87% with a 90% Bayesian Credibility Interval, equal to [13.13; 62.47]) over that time period. However, the study of its trajectory for the last three generations (i.e. from 1997 to 2011) seems to show a trend reversal, despite the fact that the slope parameter from regression used was very close to 0 (0 value included in the 90% Bayesian Credibility Interval). Abundance estimates for recent years show an increase in numbers since 2006. The Anticosti Island Atlantic salmon metapopulation therefore appears to have increased since the COSEWIC study was presented. An average of 4000 adults was reported in 2011.
Despite this upward trend since 2006, adult returns to Anticosti Island decreased in 2011 and 2012. The model presented in this study—produced using data specific to the metapopulation—was used to estimate the conservation limit (CL), which is significantly lower than the CL currently used for management purposes and is based on data from the six Quebec control rivers (Fontaine and Caron 1999). Current recovery dynamics parameters indicate that the population is viable. The probability that the broodstock was over the CL varies between 0.95 and 1. Several productivity (variation in survival and rearing capacity) and sport fishing management scenarios were tested, and none indicated that sport fishing has an impact on the decreasing number of returning adults.
This document includes the two reports prepared by the consultant.
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