Seasonal changes of some population parameters and stomach content of gelatinous organisms in sinop coasts of The Black Sea

The present study was carried out at the Sinop coast of the Black Sea between January 2008 and December 2008. Seasonal distribution, monthly abundance, biomass value and some population parameters of Aurelia aurita, Mnemiopsis sp., Beroe ovata and Pleubrachia pileus and stomach content of A. aurita, Mnemiopsis sp. and B. ovata were determinated during the study.The main feeding groups of A. aurita and Mnemiopsis sp. were determinated Copepoda (41.7% ve 31.7%) and Mollusca (21.2% ve 29.6%). Frequency and quantitative rate of fish eggs and larvae of A. aurita were calculated in the stomach content as 0.8% and 2.1%, respectively. These values were determined for Mnemiopsis sp. 1% and 0.9%, respectively. On the other hand B. ovata has been identified not feed with zooplankton.In the vertical and horizontal tows, the amount of gelatinous organism was no significant statistically among stations (p> 0.05: Anova). Seasonal differences have been observed in biomass and abundance of species depend on the seasons. Average abundance and biomass of gelatinous organism were determined in the vertical and horizontal tows as 16.30n/m2 and 79.90g/m2; 0.13n/m3 and 1.56 g/m3, respectively.Maximum gelatinous organism abundance and biomass were calculated in vertical tows as 56 n/m2 (August) and 360 g/m2 (April) respectively. In horizontal tows maximum abundance and biomass values were determined in March 1.72 n/m3 and 21.96 g/m3, respectively.In the study, length and weight of total 2317 specimens (1025 A. aurita, 980 Mnemiopsis sp., 99 P. pileus and 213 B. ovata) were measured. Average length and weight of species were calculated as 7.6 ? 0.1203 cm, 3.2 ? 0.060 cm, 0.8 ? 0.0173 cm, 3.5 ? 0.0956 cm; 32.3 ? 1.1661 g 7.3 ? 0.250 g, 0.7 ? 0.0178 g, 4.4 ? 0.3355 g respectively.Maximum and minimum length and weight of A. aurita, P. pileus, B. ovata and Mnemiopsis sp. were determined as 28 cm, 1 cm; 2.1, 0.2 cm; 9.5, 0.7 and 10.8, 0.2 cm, 1.5 g; 0.2 g, 270 g; 0.2 g, 34 g;0.5 g and 63 g; 0.1 g, respectively.Length-weight relationship equation were found as W=0.2895L2.1653 forA. aurita, W=0.0757L0.7642 for P. pileus, W=0.2508L2.1311 for B. ovata and W=0.7905L1.6406 for Mnemiopsis sp.As result four gelatinous organisms has different monthly and seasonally density and distribution. In terms of stomach content, zooplankton, fish eggs and larvae were found as feeding preferences of organisms. These species also are shareholders in the diet of adult pelagic fish and fish eggs and larvae feed to cause adverse effects on fish stocks and affected of Black Sea fisheries are thought.