CONICET | Buscador de Institutos y Recursos Humanos

Abstract Southern geoduck is the most long-lived bivalve species under exploitation in the South Atlantic and supports diving harvest in San Matías Gulf. Except preliminary data on growth and a gametogenic cycle study, there is no basic information to manage this resource in terms of population structure, harvesting, mortality and inter-population comparisons of growth. Our aim was to analyze spatial distribution from survey data, population structure, growth and mortality of several beds along a latitudinal gradient based on age determination from thin sections of valves. We also described the spatial fishing effort allocation of the fleet, and its sources of variability from data collected on board. Three geoduck beds were located and sampled along the coast: El Sótano, Punta Colorada, and Puerto Lobos. Geoduck ages ranged between 2 and 86 years old. Growth patterns showed significant differences in asymptotic size between El Sótano (109.4 mm) and Puerto Lobos (98.06 mm). Maximum age showed a decreasing North - South trend. Natural mortality was estimated for each bed by catch curve (M = 0.105 0.177 yr -1), by a method based on mean age (M = 0.212 0.233 yr-1) and by a method based on maximum longevity recorded (M = 0.062 0.13 yr -1). Population features were integrated into the harvest analysis to generate a preliminary management proposal including subdivision of coastal zone, limited entry, harvest rate and individual vessel quotas.