Effect of spawning time on egg quality, larval morphometrics and survival of Northern pike Esox lucius
This study deals with the evaluation of egg and larval qualities for the Northern pike Esox lucius Linnaeus, 1758 according to two dates during a spawning season, on March 16 (ST1) and 23 (ST2). A higher hatching rate (97% for ST1 vs 80% for ST2) associated to a stronger resistance to starvation (21.0 days for ST1 vs 19.1 days for ST2) and a better survival rate (72% for ST1 vs 59% for ST2) were found to characterize larvae hatched from eggs spawned earlier. Moreover, a significant female effect was observed for the egg weight, the fertilization rate, the initial total length, the final weight and the resistance to starvation, where some homogenei- ties were found between eggs and offspring of different females from the two spawning times. Our results suggest the existence of an early organization of pike larval quality, which gives rise to two groups of larvae with different characteristics. Late season individuals were of a large size and a fast growth while early season ones were smaller but survived longer and resisted better to unsuitable feeding conditions. This particularity is likely to be related to a special metabolic ability allowing pike larvae hatched earlier on the spring season to decrease energetic costs in order to survive longer in the absence of adequate food.