Gastric evacuation in Siberian sturgeon (Acipenser baerii Brandt, 1869) and Russian sturgeon (Acipenser gueldenstaedtii Brant & Ratzeburg, 1833)

Siberian sturgeon (Acipenser baerii) and Russian sturgeon (Acipenser gueldenstaedtii) are species from Acipenseridae family. They have been listed as endangered species because of human activities, overfishing and climate change. Though they have been successfully maintained in captivity fed on artificial diets, but their production under aquaculture conditions still needs further studies to obtain their high yields. The aim of this study was to estimate the gastric evacuation (GE) in A. baerii and A. gueldenstaedtii for their proper feeding management. For this purpose, the effects of body and meal sizes on gastric excretion (GE) of Siberian sturgeon (A. baerii) and Russian sturgeon (A. gueldenstaedtii) fed live food (whiting fish) or commercial pellet feed were parameterized. Since they are endangered species, therefore, their GER were investigated by radiographic methods instead of dissection of fish to recover the stomach contents. 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. A. baerii ranged from 1.5 kg to 5 kg (total length ranged 76.1-104 cm) fed on meal sizes of 4.6 g to 47.6 g composed of either commercial pellets or live food (fish prey, whiting). Acipenser gueldenstaedtii of different body sizes (total length ranged 82 to 105 cm, wet weight 3-5.1 kg) were fed on meal sizes ranged from 23 to 72 g composed of either live food or commercial pellets. 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 exponential model respectively. The gastric evacuation of A. baerii can be summarized by by (dS_t)/dt=-0.00182W^0.40 〖 e〗^0.080T √(S_t ) (g h-1) fed commercial pellets and (dS_t)/dt=-0.00169W^0.40 〖 e〗^0.080T √(S_t )(g h-1) fed live food. 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 power model. The gastric evacuation of A. gueldenstaedtii can be summarized by (dS_t)/dt=-0.000062 L^1.84 √(S_t ) (g h-1) fed commercial pellets, and (dS_t)/dt=-0.000053 L^1.84 √(S_t ) (g h-1) fed on live food. The process of gastric evacuation in both fishes were best described by the square root model. In this study, we have made an attempt to model gastric emptying of A. baerii and A. gueldenstaedtii fed on commercial and live food. The results of this investigation should facilitate the aquaculture practice to design a feeding frequency for A. baerii and A. gueldenstaedtii to minimize the food waste.