Spatial variability of Spanish sardine (Sardinella aurita) abundance as related to the upwelling cycle off the southeastern Caribbean Sea

PLoS One. 2017 Jun 27;12(6):e0179984. doi: 10.1371/journal.pone.0179984. eCollection 2017.

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.

MeSH terms

  • Animal Distribution / physiology*
  • Animals
  • Biomass*
  • Caribbean Region
  • Ecosystem
  • Fisheries*
  • Fishes / physiology*
  • Seasons*

Grants and funding

This research was carried out under the CARIACO Time-Series program, funded by: the National Science Foundation (NSF, USA, Grants OCE-0752139, OCE-9216626, OCE-9729284, OCE-9401537, OCE-9729697, OCE-9415790, OCE-9711318, OCE-0326268 and OCE-0963028), the National Aeronautics and Space Administration (NASA, USA, Grants NAG5-6448 and NAS5-97128), the Consejo Nacional de Investigaciones Cientificas y Tecnológicas (CONICIT, VENEZUELA, Grant 96280221), the Fondo Nacional de Investigaciones Científicas y Tecnológicas (FONACIT, Venezuela, Grant 2000001702 and 2011000353), and LOCTI (Grant CON-EDIMAR 23914). Acoustic surveys were funded by the Regional Technical Cooperation Fishing Programme VECEP (UE-VECEP ALA 92/43) between the European Union and Venezuela. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.