No abstract

Black scorpion fish (Scorpaena porcus) is an important species for both artisanal and industrial fisheries in the Turkish Black Sea, with 306 tonnes landed in 2017. The diet composition of this species was investigated through the examination of their stomach contents. A total of 621 S. porcus (ranging from 12.79–765.5 g) were caught by trammel net in the south-eastern Black Sea (Turkish waters) from December 2015 to November 2016. The importance of prey items in the diet of S. porcus was assessed using the Index of Relative Importance (%IRI). Overall, the dominant species was the isopod Idotea balthica (52.8%IRI) followed by decapods (38.5%IRI) and teleosts (8.7%IRI). Seasonal variations in the diets were observed, with isopods predominant in autumn (>85%IRI), teleosts in winter (>77%IRI) and decapod crustaceans (>78%IRI) in spring and summer. The modified Costello's graphical analysis evinced a specialist feeding strategy for S. porcus during winter, spring and autumn while a shift to generalistic feeding strategy was exhibited in summer by a limited number of S. porcus individuals.

Summary This study aimed to parameterize the effects of body and meal sizes on the gastric evacuation (GE) of farmed Russian sturgeon (Acipenser gueldenstaedtii) fed on live food (whiting fish) or commercial pellets. The radiography technique was used to monitor the evacuation of food from the stomach into the intestine at postprandial time. Acipenser gueldenstaedtii of different body sizes (total length ranged 82–105 cm) were fed on meal sizes ranged from 23 to 72 g composed of either live food or commercial pellets (had a 20% of BaSO4 as a radiopaque material). The square root model was found to adequality describe the process of GE in A. gueldenstaedtii independently of meal type and size. The effects of fish size on GER was described by simple power model and can be summarized by dStdt=-ρLL1.84St·false(normalg·h-1false), where ρL was 0.000053 for live food and 0.000062 for commercial pellets (estimated from combined GE data), St is stomach contents (g), L is fish total length (cm) and t is time (h). The results of this study will provide a useful tool to estimate the stomach fullness of A. gueldenstaedtii at postprandial time t. Such information should assess the feeding strategy to minimize feed wastage and optimize the fish growth.

This study reports first estimation of length-weight relationships for nine Cyprinid species; Barbus niluferensis Turan, Kottelat and Ekmekçi, 2009 Anahtar Kelimeler: Cyprinidae, boy-ağırlık ilişkisi, yeni tür, iç su, Türkiye.

The effects of body and meals sizes on gastric evacuation (GE) of the endangered Siberian sturgeon (Acipenser baerii) were parameterized (at temperatures ranging from 16.8 to 17.6°C) using radiography technique. GE experiments were performed using different body sizes A. baerii ranged from 1.5 kg to 5 kg fed on meal sizes of 4.6 g to 47.6 g composed of either commercial pellets or live food (fish prey, whiting). The commercial pellets used in these experiments had barium sulphate at concentrations of 20%, while the same amount was injected into the body of live food for radiography technique monitoring. The course of GE in A. baerii was best described by the square root model independently of meal size. The effects of body mass and temperature on GE rates were described by power model and simple exponential model respectively. GE rates of A. baerii fed on live food could be summarized by dStitalicdt=-0.00169W0.40e0.080TSt (g/hr), while dStitalicdt=-0.00182W0.40e0.080TSt for commercial pellets, where St is the stomach contents mass (g), W is fish wet weight (cm), T is temperature (°C), and t is time (hr). These summarized models could estimate the time required for a meal to be evacuated from the stomach of A. baerii or determine the stomach fullness at postprandial time t. These results will assess the planning of feeding regime for A. baerii to avoid their overfeeding and underfeeding.