engleski

Distribution of anchovy eggs stages during the day along the eastern Adriatic Sea

The aim of the research was to define the spatiotemporal distribution of anchovy eggs which should bring us closer in defining the area of anchovy spawning. Scientific survey was done with research vessel “Bios Dva” along the eastern Adriatic Sea from 24 June - 13 July 2019. Ichthyoplankton samples (n=60) were collected using a WP2 sampler (mouth opening, 0.255 m2 ; mesh size, 0.2 mm) from 7 AM to 20 PM. Standard vertical plankton tows were made to a depth of 100 m or to 5 m above the seabed in marine areas with less than 100 m depth. Plankton samples were immediately filtered and preserved in 96% ethanol. In the laboratory, under the binocular microscope, anchovy eggs from the ichthyoplankton samples were isolated, staged and counted. Their abundance was standardized to numbers per square metre. Out of 60 collected ichthyoplankton samples, the presence of anchovy eggs was noted in 47 stations, while their abundance per station varied from 3.92 to 188.24 eggs/m2 . Average time of anchovy egg incubation from fertilization to hatching (Do), due to measured sea temperatures at depth of 5 m (24.6±1.67°C), on the eastern side of the Adriatic was Do=1.28±0.17 days. Distribution of anchovy eggs by the hour of capture was bimodal, revealing that majority of anchovy eggs were obtained in samples collected from 9-10 AM (21.5%) and 17-18 PM (17.5%). In each ichthyoplankton sample containing anchovy eggs, they were usually in several different stages. So, according to analysed data, it seems that anchovy egg stages from I- IV were found before and the stages from V-IX (with exception of stages VIII and X) after the midday.

small pelagic, early life stages, eastern Mediterranean

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