No abstract

Qualitative composition and abundance of both ichthyoplankton and small forms of zooplankton were evaluated by field studies in the northern (the Crimea near Sevastopol) and southern (Sinop region and TEEZ) Black Sea during the summers 2000 and 2001. A tendency of increasing the species richness, abundance of fish eggs and larvae as well as zooplankton (which is the food for fish larvae) was observed over a period of Mnemiopsis leidyi and Beroe ovata co-existence. The eggs and larvae of the Mediterranean migrants—bonito and bluefish appeared again in the coastal waters near Sevastopol, which testified to favourable conditions for the spawning and nutrition of these fish species and their larvae. Aborigen copepod Oithona nana was found in the Crimean coastal waters although earlier in the 1990s it had completely vanished. Although rare in the 1990s copepods Centropages ponticus and Paracalanus parvus appeared in inshore waters as well as Pontellids species. Observed increases in species number and abundance of both ichthyoplankton and small zooplankton (≤500 μm), which promoted survival and development of fish larvae, were attributed to reduced predatory impact of Mnemiopsis on prey zooplankton after the arrival of Beroe in the late 1990s. However, the influence of Mnemiopsis continued to be significant during the short period of its peak occurrence in late summer. When this period coincided with the appearance of fish larvae, a negative impact on their survival could be predicted due to a low concentration of food items for larvae feeding.

In the present study, seasonality and composition of phytoplankton and zooplankton were comparatively studied at two stations (one inshore and one offshore) off Sinop, in southern Black A total 76 genera including 149 species and varieties were identified, of which 46% were dinoflagellates and 34% were diatoms in phytoplankton. Abundance of the genera Emiliana (in January-May 1999), Pseudosolenia and Ceratium (in MarchOctober 2000) were higher than that of the other genera in almost every sampling period. Increased dinoflagellate to diatom ratio reflects more fertile conditions in the southern Black Sea.Abundance and biomass of the total fodder zooplankton the highest values were recorded in February 1999; March 2000. Cladocera and Appendicularia abundance and biomass values were higher in 1999 than 2000. Noctiluca scintillans was the most abundant of zooplankton group with a share of 43% (maximum: 416,925 ind.m-2 in May) in 1999. The second abundant group was Copepoda with 42% (172,981 ind.m-2 in February).Copepods with 78% of abundance and 73% of biomass (maximum: 372,330 ind.m-2 and 15,253 mg.m-2 in March) were the dominant group in 2000. They were followed by the dinoflagellate Noctiluca scintillans with 4.8% (maximum: 24,500 ind.m-2 in June).

Karadeniz'de hamsi (Engraulis encrasicolus) popülasyon dinamiği üzerine yapılmış çalışmaların (1985-2015) balıkçılık yönetimi açısından değerlendirilmesi Evaluation of anchovy (Engraulis encrasicolus) population dynamics studies (1985-2015) in terms of fisheries management in the Black Sea