RESUMO
The Sardinella aurita fishery off northeastern Venezuela, region of seasonal wind-driven coastal-upwelling, accounts for 90% of the Caribbean Sea small pelagic catch. This law-protected artisanal fishery takes place up to ~10 km offshore. The spatial distribution, number of schools, and biomass of S. aurita were studied using eight hydro-acoustic surveys (1995-1998). The study included the analysis of satellite-derived sea surface temperature and chlorophyll-a. Surveys were grouped by strong, weak, and transitional upwelling seasons. Relationships between these observations were analyzed using Generalized Additive Models. Results show that during the primary upwelling season (January-May) sardines were widely distributed in upwelling plumes that extended up to 70 km offshore. In the other hand, during the weak upwelling season (September-October) higher sardine densities were found within 10 Km off the coastal upwelling foci. The number of small pelagic schools was directly correlated with small pelagic densities; however, regardless of the season, higher numbers of small pelagic schools were always closer to the shoreline, especially during warm conditions. These two behaviors increase the availability and catchability of sardines for the artisanal fishery during the warm season, regardless of the total stock size. Using this evidence, we pose the hypothesis that the collapse of the regional S. aurita fishery in 2005 was due to a combination of stressful habitat conditions sustained since 2004. These included bottom-up factors due to food scarcity caused by weak upwelling, combined with top-down stress due to overfishing, as sardines accumulated in narrow diminished upwelling plumes located close to the coast. The increased catchability within easily accessible upwelling foci led to the demise of this biological resource, which as of 2014 had not yet recovered. Environmental conditions affecting the sardine habitat needs to be taken into account for the management of this stock. For example, during years with weak upwelling, special measures should be taken during the warm season on the second half of the year to avoid further pressure on the stock.
Assuntos
Distribuição Animal/fisiologia , Biomassa , Pesqueiros , Peixes/fisiologia , Estações do Ano , Animais , Região do Caribe , EcossistemaRESUMO
Se describe la pesquería del cangrejo Callinectes sapidus del lago de Maracaibo y se realiza una evaluación del recurso por medio de modelos de dinámica de biomasa. Esta pesquería reviste singular importancia a nivel regional por el número de empleos generados en las fases de extracción y procesamiento, así como por las divisas generadas al exportarse alrededor del 95 por ciento de la producción. Las series de capturas y capturas por unidad de esfuerzo (CPUE) en kg/nasa cubren el período 1984-1997. En este lapso las capturas totales del recurso han variado entre un mínimo del orden de 2000 tm en 1996 y un máximo de aproximadamente 5400 tm en 1994, mientras que el esfuerzo de pesca se ha incrementado de manera constante al pasar de alrededor de 70000 nasas en 1984 a más de 270000 nasas en 1997. Este comportamiento de la pesquería ha ocasionado una disminución notable de la CPUE, al pasar de algo menos de 50 kg/nasa en 1985 a menos de 10 kg/nasa en 1996. El análisis de los datos por medio de los modelos de producción arroja una Captura Máxima Sostenible (CMS) del orden de 3800 tm, con un esfuerzo correspondiente de alrededor de 140000 nasas. Los límites de confianza al 95 por ciento de la CMS se ubicaron entre 3650 y 4100 tm para el modelo de error en procesos y entre 3400 y 4300 tm para el modelo de error en observaciones. Los niveles de captura y esfuerzo de pesca en años recientes son excesivamente elevados y deben reducirse para evitar la sobrepesca y recuperar los niveles de biomasa
