Effects
of Four Density Levels on Tule Fall Chinook Salmon during Hatchery Rearing
and after Release
J.L. Banks, E.M. La
Motte -2002
North American Journal of Aquaculture, 64(1): 24–33
Abstract:
Tule fall chinook salmon Oncorhynchus tshawytscha
were reared in a hatchery with a semiclosed water recycle and reconditioning
system at a customary density of 364,000 fish per pond and at reduced
densities of 273,000, 182,000, and 91,000 fish per pond. Fingerlings from
four brood years were used to evaluate rearing density effects on growth and
mortality during rearing and on smolt survival and adult contribution after
release. During the rearing of each brood, about one-third of the original
population in each pond was released by random removal in March and a second
third was released in April. All remaining fish were released in May. An
inverse relationship was apparent between rearing density and fingerling
growth (R =
- 0.868).
Rearing losses were low (<1.4%) in all test groups and were not affected
by density. Decreased levels of rearing density produced only limited and
inconsistent increases in smolt survival rate (from 0.18% to 0.27%) after
release. This weakness in treatment effects was reflected in a nearly linear
relationship (R = 0.985) between decreased rearing density and decreased
adult contribution and return to the hatchery.
(Abernathy Fish Technology
Center, U.S. Fish and Wildlife Service, 1440 Abernathy Road, Longview,
Washington 98632, USA)