Fecundity and spawning mode of three introduced fish species in Lake Banyoles (Catalunya, Spain) in comparison with other localities

Analysis was conducted during 1991 into the fecundity and oocyte size distribution of pumpkinseed, roach and rudd in Lake Banyoles. We found that individual fecundities of these species in Lake Banyoles were lower in comparison with other localities. In roach, there was a moderately significant negative relationship between latitude and egg number. The temporal pattern of the pumpkinseed's oocyte size distribution suggests that it is a multispawner fish that spawns several batches of eggs from mid-May to mid-August. In contrast, roach and rudd seem to be monospawners fish that release only one batch of eggs before mid-May. The monospawning behaviour of rudd in Lake Banyoles is in contrast to the evidence from other waters. Variations in fecundity and spawning mode are discussed on the basis that they are due mainly to differences in local conditions.