Volutid snails have been identified as a potential resource for artisanal fisheries in northern patagonic gulfs. We explored their availability in two gulfs of Chubut Province (Patagonia, Argentina) by means of SCUBA diving and baited traps. CPUE and biomass were estimated from visual counting densities. CPUE of all the volutes was 65.85 kgÁdiver -1 Áh -1 and 59.5 kgÁdiver -1 Áh -1 in San Matı´as (SMG) and San Jorge (SJG) Gulfs, respectively. Estimated biomass was 89.7 (±28.9) and 44.4 (±19.2) tons in SMG and SJG. The species Adelomelon ancilla and Odontocymbiola magellanica could supplement the potential clam fishery existent at SJG. In SMG Zidona followed by O. magellanica could be the main commercial target. We suggest minimum catch sizes of 16 cm for Z. dufresnei, 9 cm for O. magellanica, and 12 cm for A. ancilla. Protection of the egg capsules and females would help the protection of the resource. These measures could ensure the sustainability of a small-scale multispecific fishery.

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SUMMARY: Southern geoduck is the most long-lived bivalve species exploited in the South Atlantic and is harvested by divers in San Matías Gulf. Except preliminary data on growth and a gametogenic cycle study, there is no basic information that can be used to manage this resource in terms of population structure, harvesting, mortality and inter-population comparisons of growth. Our aim was to analyze the 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 allocation of the fleet's fishing effort, 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 the asymptotic size between El Sótano (109.4 mm) and Puerto Lobos (98.06 mm). The maximum age decreased from north to south. Natural mortality was estimated for each bed according to a catch curve (M = 0.105 -0.177 yr -1 ), with a method based on mean age (M = 0.212 -0.233 yr -1 ) and 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 that includes subdivision of the coastal zone, limited entry, harvest rate and individual vessel quotas.Keywords: geoduck, clams, fishery, ageing, population structure, growth, natural mortality. RESUMEN: Estructura poblacional, distribución y explotación de la almeja panopea del sur, PanoPea abbreviata, en el Golfo San Matías (Patagonia, Argentina). -La almeja panopea del sur es el bivalvo más longevo bajo explotación en el Atlántico Sur y es objeto de explotación artesanal mediante buceo en el Golfo San Matías. Salvo datos preliminares de crecimiento y un estudio del ciclo gametogénico, se carece de información relevante para el manejo del recurso como estructura poblacional, mortalidad y diferencias interpoblacionales de crecimiento. Los objetivos de este trabajo fueron analizar la distribución espacial de datos de relevamientos, la estructura poblacional, el crecimiento y la mortalidad en bancos situados a lo largo de un gradiente latitudinal a partir de determinación de edad mediante secciones delgadas de valvas. También se describe la distribución espacial del esfuerzo pesquero de la flota y sus fuentes de variabilidad a partir de datos colectados a bordo. Tres bancos de panopea fueron localizados y muestreados a lo largo de la costa: El Sótano, Punta Colorada y Puerto Lobos. La edad de los individuos osciló entre 2 y 86 años. El patrón de crecimiento mostró diferencia significativa entre la talla asintótica en El Sótano (109.4 mm) y Puerto Lobos (98.06 mm). La edad máxima evidenció una tendencia decreciente Norte -Sur. La mortalidad natural fue estimada en cada banco mediante curva de captura (M = 0.105 a 0.177 año -1 ), un método basado en...

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