This study examines the key factors influencing the survival of pink and chum salmon eggs and alevins in spawning beds, with a focus on research conducted by the U.S. Bureau of Commercial Fisheries in Sashin Creek, Little Port Walter, Alaska.
In investigations conducted at Indian Creek, Twelvemile Creek, and Harris River in southeastern Alaska, McNeil observed the disappearance of eggs and alevins from the spawning grounds during periods of high streamflow. The loss of eggs and alevins during intense freshets often exceeded 50 percent, and on one occasion, it surpassed 90 percent. Unlike many other spawning streams for pink and chum salmon, Sashin Creek benefits from lakes within its watershed that store water during freshets, resulting in relatively stable streamflow. The discharge of Sashin Creek rarely exceeds 17m³ per second (600 cfs), approximately 60 times the minimum flow.
As a result, the removal of eggs and alevins by high streamflow may be less severe in Sashin Creek. However, it is evident that high streamflow contributes to the disappearance of eggs from the upper segment of the Sashin Creek spawning ground during autumn, even without mechanical disturbance of the bed. discovered suspended eggs near the streambed's surface by agitating the overlying water within a 0.2 m² circular screen. Testing multiple random points per segment of the spawning ground in September 1965, McNeil collected 19 times more eggs from the coarse bed materials of the upper segment than from the fine bed materials of the lower segment. This finding indicates that eggs can be dislodged from coarse bed materials by turbulent water, as well as being susceptible to predation.
In years with substantial runs, both the upper and lower segments of the Sashin Creek spawning ground are extensively utilized by pink and chum salmon spawners. However, fry production per square meter of spawning ground has consistently been at least twice as high in the upper segment compared to the lower segment. When the runs are small, pink and chum salmon tend to spawn in the lower segment and often disregard the upper segment (Merrell, 1962; McNeil, 1968). Consequently, in situations with few spawners, those present tend to concentrate where water flow conditions and oxygen supply are less favorable for eggs and alevins. This behavior helps them avoid an area where their eggs are more vulnerable to predation.
This study examines the key factors influencing the survival of pink and chum salmon eggs and alevins in spawning beds, with a focus on research conducted by the U.S. Bureau of Commercial Fisheries in Sashin Creek, Little Port Walter, Alaska.
In investigations conducted at Indian Creek, Twelvemile Creek, and Harris River in southeastern Alaska, McNeil observed the disappearance of eggs and alevins from the spawning grounds during periods of high streamflow. The loss of eggs and alevins during intense freshets often exceeded 50 percent, and on one occasion, it surpassed 90 percent. Unlike many other spawning streams for pink and chum salmon, Sashin Creek benefits from lakes within its watershed that store water during freshets, resulting in relatively stable streamflow. The discharge of Sashin Creek rarely exceeds 17m³ per second (600 cfs), approximately 60 times the minimum flow. As a result, the removal of eggs and alevins by high streamflow may be less severe in Sashin Creek. However, it is evident that high streamflow contributes to the disappearance of eggs from the upper segment of the Sashin Creek spawning ground during autumn, even without mechanical disturbance of the bed. discovered suspended eggs near the streambed's surface by agitating the overlying water within a 0.2 m² circular screen. Testing multiple random points per segment of the spawning ground in September 1965, McNeil collected 19 times more eggs from the coarse bed materials of the upper segment than from the fine bed materials of the lower segment. This finding indicates that eggs can be dislodged from coarse bed materials by turbulent water, as well as being susceptible to predation.
In years with substantial runs, both the upper and lower segments of the Sashin Creek spawning ground are extensively utilized by pink and chum salmon spawners. However, fry production per square meter of spawning ground has consistently been at least twice as high in the upper segment compared to the lower segment. When the runs are small, pink and chum salmon tend to spawn in the lower segment and often disregard the upper segment (Merrell, 1962; McNeil, 1968). Consequently, in situations with few spawners, those present tend to concentrate where water flow conditions and oxygen supply are less favorable for eggs and alevins. This behavior helps them avoid an area where their eggs are more vulnerable to predation.