ICHTHYOPLANKTON OF THE SEA OF MARMARA

In this paper, ichthyoplankton studies in the Sea of Marmara are evaluated and summarized. The chronological records of ichthyoplankton studies were listed, whilst temporal and spatial variations in fish egg and larvae biodiversity were discussed. The ecological role of fish eggs and larvae as an indicator were shown. The first study dealt with ichthyoplankton in the Sea of Marmara, as well as in Turkiye was carried out in 1957. In total, eggs and/ or larvae of 76 fish species belonging to 32 families were identified in the Marmara Sea from 1993 to 2022. The biodiversity of fish eggs and larvae appears to increase around the southwestern part of the Marmara Sea. In the ichthyoplankton, the European sprat Sprattus sprattus and the anchovy Engraulis encrasicolus are the most abundant species in the winter and summer periods, respectively. The inflow intensity and the direction of the upper current layer from the Black Sea represent a significant constraint on spatial variation. Pollution, global warming, acidification, and excessive, illegal fishing and recent mucilage events are threats causing ecological changes in the ichthyoplankton in the Sea of Marmara. The decrease in the stocks of migratory fish such as mackerel and bluefish in recent years, the breaking of the food chain due to overfishing of sprat before mucilage, and the gradual decrease in the egg and larval biomass of sardines provide essential evidence in this regard. Although many valuable studies have been conducted, continuous systematic monitoring studies should be undertaken from specific fixed stations reflecting spawning seasons and spawning areas to understand the impact of environmental variations on fish stocks, to develop sound advice to fisheries management authorities.