Distribution of Engraulis encrasicolus eggs and larvae in relation to coastal oceanographic conditions (a south-western Adriatic Sea case study)

The identification of European anchovy (Engraulis encrasicolus) spawning and nursery areas is a key step in the management of an essential resource for fisheries and pelagic trophic webs. Eggs and larvae collected in ichthyoplankton surveys (2012 - 2015) carried out in the south-western Adriatic Sea were examined to investigate the mechanisms that control their distribution. Egg and larval abundance varied through the years, the highest values being recorded in 2012 and the lowest in 2014, and their abundance correlated positively with the zooplankton biomass. Application of quotient analysis to identify their relationships with environmental and biological variables demonstrated egg preferences for depths between 91 - 120 m and avoidance of depths between 11 - 30 m and for high values of chlorophyll-a (> 0.52 mg m-3) and low values of zooplankton biomass (< 199 mg m-2). The habitat preferences and avoidances of larvae were characterized by a preference for depths between 11 - 60 m and for high zooplankton biomass values (> 1000 mg m-2) and by avoidance of depths > 150 m and of low biomass values (< 299 mg m-2). These correlations and quotient value analysis suggest that the distribution of eggs and larvae in the south-western Adriatic is principally driven by food availability and depth.