Mortality of Landlocked Fall Chinook Salmon Broodstock After Electrofishing or Ascending a Fish Ladder
Published on: 2019-05-17
Landlocked fall Chinook salmon (Oncorhynchus tshawytscha) broodstock can be obtained either passively after broodfish ascend a fish ladder, or actively through electrofishing. This study examined the mortality of broodstock Chinook salmon obtained by either method in Lake Oahe, South Dakota, USA in 2017. Overall, 10% of the 594 salmon that ascended the ladder died prior to spawning, which was significantly less than the 19% of the 344 salmon that died after electrofishing. More importantly, only 4% of the female broodstock that ascended the ladder died, which was also significantly less than the 12% mortality of females that were electrofished. Mortality of the ladder-run males was also significantly lower than that of males obtained by electrofishing. The salmon broodstock that ascended the ladder survived for a slightly longer duration. These results strongly suggest a negative effect of electrofishing on landlocked fall Chinook salmon broodstock survival. The use of electrofishing to obtain landlocked Chinook salmon broodstock is only recommended if the number of fish ascending a fish ladder cannot provide the desired number of broodstock.