Effects of four factors on the quality of male reproductive cycle in pikeperch Sander lucioperca

A multiplicity of factors could modulate the quality of gametogenesis in fish. In the present study, we used a fractional factorial design (24-1, resolution IV) experiment to determine the possible effects and interactions between three nutritional factors both before (initial fat store: high vs low initial fat index) and during an entire reproductive cycle (food type: pellets vs forage fish, feeding rate: ad libitum vs restricted) and photoperiodic condition (simulated natural vs natural photoperiod) on both male pikeperch condition at spawning and sperm quality. The initial fat store of males appeared to be the most influential factor on the quality of sperm, in terms of the concentration of spermatozoa and motility at 15 s, and also on the timing of spermiation: fish with high initial fat store were spermiating earlier during the spawning season. A significant interaction between the initial fat store and feeding rate during fall and winter was found on the variation of weight, i.e., pikeperch changed its feeding behaviour according to the modalities of these two factors. On the opposite, feeding rate, food type and photoperiodic conditions during the experiment appeared less important. Consequently, the use of males with high initial fat store before the starting of a reproductive cycle is strongly recommended.