The Abundance and Distribution of the Early Life Stages of Sardine ( Sardina pilchardus ) in Central of the Aegean Sea (
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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 Orçin Uygun 1
&
Belgin Hoşsucu 1
Received: 14 November 2019 / Revised: 16 April 2020 / # Springer Nature Switzerland AG 2020
Abstract The study was carried out on a monthly basis at 16 stations between January 2017 and December 2017 in the Sığacık 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 Sığacık Bay as a spawning area. However, further ichthyoplanktonic studies considering the fluctuations of pilchard stocks in Sığacık Bay should be carried out for a longer period to better clarify the issue. Keywords Sardine . Ichthyoplankton . Environmental factors . Aegean Sea
Introduction Sardina pilchardus (Walbaum, 1792), also known as sardine, is a fully pelagic fish and has an important place in the Mediterranean fisheries (Alvares et al. 2003). The worldwide sardine production was 1.281.39 tons in 2016 (FAO 2018). However, the total production of sardines for 2018 in the Turkish Seas was only 18 tons and the majority of the production was from the Aegean Sea (67.11%) (TÜİK 2019). Small pelagic fish such as sardines are preferred food sources for humans. They are also of great importance for their role in the pelagic food chain in marine ecosystems. This is associated with their effects on the energy transfer from lower to higher trophic
* Orçin Uygun [email protected] 1
Department of Hydrobiology, Faculty of Fisheries, Ege University, Izmir, Turkey
levels (Cury et al. 2000; Bănaru et al. 2013; Torri et al. 2018). Moreover, the determination of the distribution, abundance, spawning time and area of sardine eggs provide important data that can be used in the adult stock estimations using the Daily Egg Production Method (DEPM) (Parker 1980; Hunter and Lo 1993). The review of the ichthyoplankton studies in the Aegean Sea r
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