Overlap of predator foraging and fishing over a cyclical annual biomass source in the South Caribbean

Abstract

Oceanic processes influence the abundance and distribution of species and ecosystems, contributing to primary productivity and trophic webs. Caribbean ecosystems present cyclical upwelling where Sardinella aurita predominates among pelagic species facilitating the aggregation of predators. In the South Caribbean, western coast of Aragua, Venezuela, between 2004 and 2010, the existence of a biomass source was suggested by the overlapping areas of activity of Tursiops truncatus, Stenella frontalis and fishermen. Therefore (2019–2020), 30 bimonthly transects were conducted in the aforementioned study area to record sightings of feeding species: whale sharks, seabirds, bottlenose dolphins and fishermen. This allowed the calculation of the area of their records and the determination of the overlapping zone confirming this biomass source (Kernel fixed 50 %=23.96 km²). Then a spatial and quantitative analysis of [Chlorophyll-a], sea surface temperature (SST) and precipitation between 2018 and 2020 was performed finding historical means of 0.21±0.07 mg/m³, 27.37±1.22 °C and 86.39±60 mm, respectively. This led to a review of the total fishing mass by group showing an extraordinarily high and ephemeral peak of sardine fishing with a consequent growth of tuna, billfish and tuna-like fisheries. This mesotrophic-oligotrophic zone supports an annual biodiversity cycle and is located north of Henri Pittier National Park, contributing scientific evidence in support of the expansion of the park as a marine protected area, offering protection to fishes and human well-being, as under Venezuelan law artisanal fishing would be permitted.