Frontiers in Marine Science (Oct 2015)
Spatial distribution of sardine and anchovy early life stages along the eastern Adriatic Sea
Abstract
Despite long-term investigations of the Adriatic Sea in general and extensive research on sardine and anchovy as ecologically and economically important fish species, knowledge concerning their spawning ecology, precisely their possible spawning grounds, is still incomplete. Therefore, two scientific surveys (January, July 2012) were performed, as target species spawn during different periods of the year (sardine - October to April (Sinovčić et al., 2007) and anchovy - April to September (Zorica et al., 2013)). Throughout these surveys, standard vertical plankton tows were made during the daylight at 72 stations in January and 60 stations in July using a WP2 sampler (mouth opening, 0.255 m2; mesh size, 0.200 mm). WP2 net was put vertically down during the calm sea to a depth of 100 m or to 5 m above the seabed in relatively shallow marine area (less than 100 m). Plankton samples were preserved in 4% buffered formalin and transported to the laboratory where they were analysed. Throughout ichtyoplankton analysis of samples collected during the winter survey a total of 506 sardine eggs and 348 larvae were sorted out. The mean sardine egg and larval abundance in the analysed period at positive stations was 57.8 +/- 77.4 eggs/m2 and 29 +/- 25.85 larvae/m2, with peaks of 396 eggs/m2 and 108 larvae/m2 at positive sampling stations. Concerning the summer survey and anchovy early life stages from obtained samples 1489 anchovy eggs and 1036 larvae were isolated. Average abundance of anchovy eggs and larvae was 145.26 +/- 201.27eggs/m2 and 115.11+/- 162.32 larvae/m2, respectively. The highest values of mentioned parameters at positive stations were 800 eggs/m2 and 952 larvae/m2. According to obtained results and their processing within Ocean Data View (odv.awi.de), revile that both species during 2012 spawn above the whole continental shelf and the areas of higher early life stages abundance overlap.
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