The Abundance and Distribution of the Early Life Stages of Sardine (Sardina pilchardus) in Central of the Aegean Sea (Sığacık Bay) and their Interactions with Certain Environmental Factors

Abstract

The study was carried out on a monthly basis at 16 stations between January 2017 and December 2017 in the Sigacik Bay, Izmir, Turkey. For ichthyoplankton sample collections, vertical (350 μm) plankton tows were carried out using a WP-2-type plankton net with a mouth area of 0.255 m2. Depth, temperature, oxygen, pH, salinity, zooplankton volume and chlorophyll-a values were detected at each research station in the study. The eggs and larvae of the sardine samples were obtained during the period between December and February, the maximum being in February (mean temperature 15.29 ± 0.57 °C). The mean abundance values of all sardine eggs and larvae in all stations were 78 individuals·10 m−2. The egg diameter values in sardines were in the range of 1.40–1.69 mm and the oil globule diameter values were in the range of 0.12–0.18 mm. The majority of sardine eggs and larvae were found at the depths of 25–75-m at the stations. The correlation between the abundance of sardine eggs and larvae and environmental variables was determined using the Principal Component Analysis (PCA). There was a positive correlation between sardine eggs and dissolved oxygen (r: 0.75) and a negative correlation between larvae and salinity (r:-0.75). It was concluded that sardine does not prefer Sigacik Bay as a spawning area. However, further ichthyoplanktonic studies considering the fluctuations of pilchard stocks in Sigacik Bay should be carried out for a longer period to better clarify the issue.