Spawning of sardine, Sardina pilchardus (WALBAUM, 1792), in the Adriatic under upwelling conditions

Abstract

      Data on numbers of eggs and larval stages of sardine in the plankton were  collected from the eastern half of the northern, middle and a part of southern Adriatic in March-April, 1982. Temperature, salinity, chlorophyll a quantity and numbers of phytoplankton were sampled simultaneously as well as the quantity of micro, meso and macrozooplankton.

      Spatial distribution of the number of sardine eggs pro­duced under a square metre per day showed that two spawning centres may be clearly distinguished in the Adriatic - one in the middle and other in the northern Adriatic.

      The analysis of temperature and salinity data showed that two upwelling zones were formed during the period of our study. Higher quantities of phyto and zooplankton were recorded at the boundaries of upwelling zones. Spawning centres were located also at the edges of these zones. This is indicative of the fact that during a period of the spawning season when the data were collected, the upwelling zones offered most favourable conditions for sardine reproduction.

      Data on survival of sardine plankton stages are also presented as well as a preliminary scheme of their tran­sport by currents.