Linking lake whitefish (Coregonus clupeaformis) condition with male gamete quality and quantity

Sexual-selection theory predicts males will increase investment in ejaculates if there is an increase in the level of sperm competition. Production of ejaculates is energetically costly, so males in better condition should be able to produce ejaculates of higher quality than individuals in poorer condition. We examined how ejaculate investment (i.e., relative testes mass) and sperm quality (i.e., sperm swimming speed) in lake whitefish (Coregonus clupeaformis) were related to residual soma mass, fork length, and fish age using data collected from Lake Michigan and Bay of Quinte (Lake Ontario). Populations from both lakes had positive relationships between relative testes mass and residual soma mass. Fork length was the most important predictor of sperm swimming speed with larger males from both lakes tending to have faster swimming sperm than smaller fish. Testis asymmetry, which is a commonly observed phenomenon in other animals but which has only recently been reported in fishes, was found to occur in the majority of examined lake whitefish with the left testes typically larger than the right.