COMPARATIVE SUSTAINABILITY MECHANISMS OF TWO HAKE (MERLUCCIUS GAYI GAYI AND MERLUCCIUS AUSTRALIA) POPULATIONS SUBJECTED TO EXPLOITATION IN CHILE

摘要

Common (Merluccius gayi gayi Guichenot, 1848) and southern (Merluccius aus-tralis Hutton, 1872) hakes inhabit the central (32°-41°S) and the southern (41°-57°S) regions off the coast of Chile, respectively. Both species support important trawl and longline fisheries. The common hake fishery started in the 1940s, while the southern hake fishery began in 1970s. During the last 10 yrs the abundance of common hake has increased while that of the southern hake has decreased. At present, the common hake stock is fully exploited and the southern hake is overexploited. We review several biological, fishery, and environmental aspects that influence the historical abundance of each hake. Significant differences exist regarding natural mortality, growth rates, and reproductive and feeding dynamics. The timing of the spawning season is similar for both hakes and is synchronized with the increasing turbulence and upwelling. The resilience of each species to exploitation and environmental changes was analyzed relative to their stock-recruitment (S-R) relationships coupled to environmental variables. The common hake exhibits a Ricker-type S-R relationship with clear compensatory processes due to cannibalism, with significant deviations from this model explained by environmental changes The southern hake has an almost linear S-R relationship with little evidence of compensatory components. General additive models (GAM) show that El Nino/Southern Oscillation (ENSO) events have positive effects on the recruitment of both hake species. Benchmarks consisting of extinction parameters and F_(msy) were calculated based on S-R relationships and spawning per recruit analysis. Simulations of constant catch and constant exploitation were used to portray the differences in resilience of each species to exploitation relative to the benchmarks. Results indicate that abundance of the common hake is significantly more impacted by environmental conditions while the abundance of the southern hake is controlled by exploitation regimes under a rather low population response due to the almost total lack of compensatory mechanisms in the spawner-recruit relationship.