Artificial fertilization in turbot, Scophthalmus maximus (L.):: different methods and determination of the optimal sperm-egg ratio

With the aim of improving artificial fertilization (AF) in turbot, Scophthalmus maximus (L.), a series of fertilization experiments was carried out under dry conditions and different wet conditions (eggs/sea water: 2V/V and V/V). Another series of fertilization experiments was carried out with different quantities of sperm pool to determine the optimal ratio of spermatozoa to eggs for each AF method. Sperm pool from two males and eggs from spawns with a viability rate of > 70% were used. The sperm pool's density (0.4-5.18 x 10(9) sperm mL(-1)) and motility (1-5) had been assessed previously. Significantly different fertilization rates were found when comparing 2V/V and V/V wet conditions. Significantly higher fertilization rates were found in dry fertilization when the sperm-egg ratio was > 9000 spermatozoa per egg and, under wet condition V/V, at 3000-4000 spermatozoa per egg.