Fertilisation and sperm competition dynamics in salmon

Fishes have evolved an enormous range of mating patterns and sperm competition is important in the majority of these. Detailed mechanisms of fertilization and sperm competition dynamics at the gamete level are poorly understood. We have been using salmon models to conduct in vitro fertilization trials that: (1) allow us experimental control, (2) eliminate confounding effects from the whole organism, and (3) enable detailed measures of sperm form and function in the natural fertilization medium to which gametes are adapted. Using both Atlantic and sockeye salmon, we present results on experiments exploring: (1) the importance of relative sperm number, size, % motility, longevity, and velocity for fertilization and sperm competition success, (2) the importance of natural variation in egg size for 'fertilizability' under sperm limited conditions and (3) the influence of ovarian fluid in fertilization dynamics.