Distribution and abundance of early life stages of <i>Sardina pilchardus</i> in the Gulf of Tunis (Central Mediterranean Sea) in relation to environmental and biological factors

Abstract

Four seasonal surveys were carried out in the Gulf of Tunis between summer 2002 and spring 2003 to study the abundance and distribution of Sardina pilchardus eggs and larvae in relation to environmental parameters. In the Gulf of Tunis, Sardina pilchardus begins spawning in autumn (23 eggs/10 m²) and attains its peak in winter (257 eggs/10 m²) when the mean SST is lowest (13.4°C). Sardine reproduction seems to be triggered by the decrease in the SST. In winter, the main spawning areas were located to the south of Zembra Island and the north of Cape Bon. Larvae were more abundant in winter (38 larvae/10 m²), while lower densities were collected in autumn and spring (1 larva/10 m²). The highest abundance of larvae (288 larvae/10 m²) was recorded southwest of Zembra Island. Eggs and larvae were mainly concentrated in the relatively warmer and saltier waters with high zooplankton abundance and, inversely, with a low concentration of nitrate and chlorophyll a and a low diatom abundance.