Comparison of Hatching Performances and Yolk Sac Absorptions of Black Sea Trout (Salmo trutta labrax Pallas, 1811), Brook Trout (Salvelinus fontinalis Mitchill, 1814) and Their Hybrid

The aims of this study were to determine hatching performance, body and yolk weight at hatching, the growth rate during the yolk absorption and yolk conversion efficiency of Black Sea trout, brook trout and their hybrid larvae, and to compare the relationships between length, total wet weight, dry yolk body weights of alevins and degree-days. The Black Sea trout egg has shorter incubation duration than brook trout and their hybrid. Survival from fertilization to swim-up of brook trout, Black Sea trout, and hybrid were 45.8%, 54.3% and 30.7%, respectively. Length, total wet weight, dry larva weights, and dry yolk weights of brook trout, Black Sea trout and hybrid exhibited a linear relationship with degree-days; dry yolk weight decreased, while length, total wet weight and dry body weight increased with degree-days. The linear regression parameters excluding length slope were significantly different. Length and weight increase as well as growth rates, daily yolk sac consumption and yolk sac efficiency values were calculated as 0.21 mm/day, 0.63 mg/day, 0.30 mg/day, and 0.61 for brook trout; 0.19 mm/day, 0.87 mg/day, 0.60 mg/day, and 0.76 for Black Sea trout, and 0.20 mm/day, 0.45 mg/day, 0.28 mg/day, and 0.46 for hybrid, respectively.