Effects of Delay in Water Addition or Rinsing on Fertilization Rates of Chinook Salmon, Coho Salmon, Atlantic Salmon, and Rainbow Trout Eggs

Four species of salmonids were examined for changes in fertilization rate associated with delays in the addition of water to eggs (activation) or in rinsing eggs after water addition. Rainbow trout (Oncorhynchus mykiss) showed no effects of delayed water addition, but both chinook salmon (O. tshawytscha) and Atlantic salmon (Salmo salar) showed significant declines in fertilization rate when water addition was delayed between 1 and 16 h. Watering delays of 1–60 min after addition of milt did not affect fertilization rate for any of the tested species, but coho salmon (O. kisutch) showed low fertilization rates when water was added with milt (time 0). Delays in rinsing of up to 16 h did not affect fertilization rate for rainbow trout, chinook salmon, or coho salmon: the experiments were not performed with Atlantic salmon. Milt volume had no effect on fertilization rate for wild coho or chinook salmon in either experiment. Hatchery males of rainbow trout and Atlantic salmon yielded low milt volumes; for these two species, low milt concentrations decreased fertilization rates significantly. The timing of water addition does not appear to be critical during hatchery procedures, at least within the first hour after milt and eggs are combined. A time delay of 1 h in rinsing eggs after water addition will not affect fertilization rates, but care should be made to keep eggs cool and in the dark. Attention should be given to milt concentrations; although high volumes of milt did not affect fertilzation rate, low concentrations did have an effect in some species.