Environmental related age-specific natural mortality of a high-value species: The case of Mexican green abalone fishery

Abstract

The abalone fishery has historically been among the most relevant Mexican fisheries, it started more than a century ago. It is a small-scale, multi-species fishery that harvests five abalone species, of which Haliotis fulgens (Green abalone) has >75% participation in the total catch. Abalone fishery production reached its maximum ≈6000 mt in 1950. Currently, ≈150 mt were landed in 2019. Therefore, facing this decline, the management objective is focused on recovery. Since climate is one of the stock-forcing variables, stock assessment and harvest strategy should consider environmental information, such as the increase in ocean temperature resulting from global warming. In this vein, this study shows an age-specific natural mortality model for green abalone that includes the effect of sea surface temperature (SST) interannual variability. Natural mortality estimates were performed from a biometric database (n=36, 285) obtained during annual surveys made by the Mexican National Fisheries Institute (INAPESCA) in La Bocana region off the western coast of the Baja California Peninsula from 2000–2017. Three natural mortality estimations were parameterized: (i) Natural mortality (M) for all age groups; (ii) Age-specific mortality (Mi); and (iii) Age-specific mortality estimation with SST effect (Mθi). The estimations and function parameters are statistically significant (p < 0.001), and the goodness of fit is acceptable (e.g., R2=0 .91–0.93). The information criteria suggest that Mθi fit improvement justifies the model increased complexity. The results show that SST has an inverse effect on abalone survival. Quota-managed fisheries should consider environmental effects on population dynamics to avert declines and meet the stock recovery objective.