COASTAL ECOLOGY SOUTHEAST OF MARGARITA ISLAND, VENEZUELA (APRIL 2012 - MAY 2014).

Abstract

Venezuela, until 2005 Southeast of Margarita Island was an important area in sardine fishing Sardinella aurita but catches declined sharply even until 2013; therefore, pelagic environmental conditions were studied and compared with those obtained in years when there were abundant sardine catches. For 26 months (April/2012 to May/2014) in three fixed stations sampling (every two weeks for 14 months and monthly 12 months) at depths of 1 and 20 m, horizontal hauls (10-15 m depth) for 20 minutes were made in order to study hydrography, nutrients, primary production, chlorophylls, and abundance of mesozooplankton. In 2012 and 2013 it was verified that the local aquatic fertility remained low compared to 2003-2004. In 2014 some fertility recovery was denoted by increased nutrients (nitrite and nitrate); chlorophylls a and b notably increased to 3.79 and 1.81 mg/m3 respectively and primary production to 497.97 mgC/m3/day. The average density of zooplankton ranged between 131.21 and 192.49 ind/m3, thesediment volumes 0.13-0.14 mL/m3 and dry weights between 0.62 and 0.95 mg/m3; the density of sardine eggs varied between 2.12 and 8.57/m3 and their representation in the plankton ranged between 1.88 and 6.24%, these values are much lower compared to those found in years with heavy sardine catches (2002- 2004).