Abstract
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.
Highlights
The southern Caribbean Sea (Fig 1A) is an area of pronounced seasonal coastal upwelling [1, 2]
During the upwelling season (December to May) sardine-NASC was found dispersed throughout the Sea Surface Temperature (SST) range
The most evident coastal upwelling foci during September-October were seen along the Araya and Paria Peninsulas, and within the Gulf of Cariaco (Fig 3), and sardine-NASC was highest in those areas
Summary
The southern Caribbean Sea (Fig 1A) is an area of pronounced seasonal coastal upwelling [1, 2]. Within this upwelling system, the continental shelf off northeastern Venezuela (Fig 1B) is one of the most important fishing grounds in the Caribbean Sea [3, 4]. The continental shelf off northeastern Venezuela (Fig 1B) is one of the most important fishing grounds in the Caribbean Sea [3, 4] This relatively small shelf (Fig 1B) carries a Spanish sardine (Sardinella aurita) biomass of 0.6–1.3 million tons [5, 6, 7]. The artisanal nature of this fishery is protected by law [8, 9, 10]
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