Temporal and spatial changes of ichthyoplankton in Iskenderun Bay

The mesoscale spatio-temporal changes of ichthyoplankton assemblages arising from environmental variations were investigated in the present thesis. For this purpose, a total of twelve ichthyoplankton cruises were conducted at monthly intervals between November-2009 and October 2010. During the surveys, Bongo Net towed obliquely at 28 stations located throughout İskenderun Bay. Abiotic and biotic environmental variables were also measured at each stations. Four groups indicating different temporal ichthyoplankton assemblages were found in the study area: November-January, February-March, April-June and July-October; and the indicator species of these assemblages were Bregmaceros atlanticus, Gobius paganellus, Engraulis encrasicolus and Gobius niger, respectively. The species diversity exhibited temporal variations and reached the highest values in April-June assemblage, whereas the lowest values were observed in July-October. According to CCA results, temperature explained a greater amount of total temporal variation (30%) in ichthyoplankton assemblages while zooplankton biomasses (18%) was the secondary variable. Two main tendencies were observed within the scope of spatial analysis. Hence, the ichthyoplankton assemblages of the bay exhibited a horizontally homogenous structure during the cold period lasted between December and March. Besides, two different clusters termed as inshore and shelf assemblages were clearly identified during the warm period lasted between June and September. As a result of this study, ichthyoplankton assemblages were found to be depending on reproductive cycles of teleost fishes which were mainly driven by seasonal cycles of temperature and food items. Moreover, the spatial variations were primarily explained by the dynamics of water masses and food items.