Abstract
Aquaculture production of Atlantic cod (Gadus morhua) is expected to increase dramatically over the next decade, particularly in Norway. There is growing concern over the environmental impact of farmed escapees, especially the consequences of genetic introgression with wild coastal cod. Given the fact that Norwegian coastal cod stocks are presently at a historical low, knowledge on how farmed escapees can impact these wild populations through genetic introgression is of paramount importance. The ability of cod escapees to interact with their wild counterparts will depend on a number of factors including gamete quality. In order to determine whether spawning success of farmed escapees can be correlated to differences in sperm competition we undertook a spawning study using farmed and wild cod from the same putative coastal population. Multiple cross fertilizations were performed under controlled conditions using eggs from both wild and farmed females fertilized using milt of equal quantities from a wild and farmed male. Male paternity of the offspring was determined by microsatellite DNA analysis. In addition, blood samples were taken for steroid hormone analysis. Sperm quality parameters, in terms of percentage motile sperm and sperm motility were evaluated by Computer Assisted Sperm Analysis (CASA). Spawning success, as determined from the male parentage of the offspring, was correlated to both sperm quality and other male reproductive parameters including plasma steroid levels and gonadosomatic index.