Reproductive strategy of the European perch, Perca fluviatilis Linnaeus, 1758 (Osteichthyes: Percidae) in the Anzali wetland, southwest Caspian Sea

Temporal variation in reproductive traits of geographically distributed fish is supposed to take place in response to the spatial and environmental variations. With regard to the wide distribution of the European perch in the northern hemisphere, important reproductive traits such as the initiation and duration of the spawning activity are likely to vary in different latitudinal gradients. In this study, reproductive biology of the European perch, Perca fluviatilis, is described, based on 324 specimens caught in the Anzali wetland (southwest Caspian Sea) between June 2008 and May 2009. The gonadosomatic index, oocyte frequency distribution and histological examination suggested a long vitellogenic process (October to February) and a short spawning season (January and February). The size-frequency distribution of the oocytes showed that this perch is a species with group-synchronous ovarian development. Ovarian development occurred only in one clutch of oocytes (700-900m oocyte diameter) with no indication of maturation of any subsequent clutch in the spawning season. The average of (realized) fecundity (+/- SD) was estimated to be 16177 +/- 5846 eggs in late vitellogenic stage, which was lower than the potential fecundity (17188 +/- 6917 eggs). Histological examination of the gonads revealed the existence of atretic oocytes in early vitellogenic stages (October and November). This investigation highlights the temporal variation in the initiation and duration of the reproductive activity of the European perch in this region compared to other geographical regions. The results emphasize the necessity of specific temporal management in fishing of European perch based on spatial differences in reproductive biology.