Environmental Influences on Landlocked Fall Chinook Salmon Reproductive Characteristics

Abstract

From 1988 to 1998, we evaluated relationships among several environmental and biological variables and the fecundity, egg size, and embryo survival to the eyed stage of landlocked fall chinook salmon Oncorhynchus tshawytscha from Lake Oahe, South Dakota. The environmental variables recorded in Lake Oahe included monthly and total yearly inflows and outflows, end-of-month elevations, yearly mean end-of-month elevations, and 13°C and 15°C habitat volumes. Biological variables included gill-net catch per unit effort (CPUE) of lake herring Coregonus artedi, rainbow smelt Osmerus mordax, and chinook salmon (for age-0, age-1 and older, and all fish); chinook salmon age-1 mean relative weight; and rainbow smelt abundance in both the 13°C and 15°C habitat volumes. Chinook salmon fecundity was significantly related to rainbow smelt CPUE (r = 0.841) and chinook salmon CPUE (r = 0.853). Fecundity was also significantly related to mean relative weight of age-1 and older salmon collected in gill nets the year before spawning (r = 0.892). Embryo survival to the eyed stage was significantly related to May inflows (m³) into Lake Oahe during the year of spawning (r = 0.662) and to October inflows in the year before spawning (r = 0.674). Egg size was significantly related to reservoir elevations (reservoir volumes) in March, April, and May from the year before spawning (r = 0.774, 0.794, and 0.765, respectively). The relationships observed may be indicative of dietary influences, particularly rainbow smelt productivity and availability, on chinook salmon reproduction. Hatchery personnel can use the regression equations to predict the number of female chinook salmon that need to be spawned and the number of eggs to be incubated to meet the production requests of fisheries managers.