Survival Comparison of Spring Chinook Salmon Reared in a Production Hatchery under Optimum Conventional and Seminatural Conditions

Abstract

We found insufficient evidence to conclude that seminatural treatment (SNT; i.e., rearing in camouflage-painted raceways with surface and underwater structures and underwater feeders) of juvenile Chinook salmon Oncorhynchus tshawytscha resulted in higher survival indices than did optimum conventional treatment (OCT; i.e., rearing in concrete raceways with surface feeding) for the specific treatments and environmental conditions tested. We reared spring Chinook salmon from fry to smolt in paired raceways under the SNT and OCT rearing treatments for five consecutive years. For four to nine SNT and OCT raceway pairs annually, we used passive integrated transponder, coded wire, and visual implant elastomer tags to compare survival indices for juvenile fish from release at three different acclimation sites 340-400 km downstream to passage at McNary Dam on the Columbia River, and for adults from release to adult return to Roza Dam in the upper Yakima basin. The observed differences in juvenile and adult survival between the SNT and OCT fish were either statistically insignificant, conflicting in their statistical significance, or explained by significant differences in the presence of the causative agents of bacterial kidney disease in juvenile fish at release.

Structural Complexity Improves the Rearing Performance of Rainbow Trout in Circular Tanks

“…In comparison with circular tanks without rods, no additional tank cleaning or maintenance is required. Withintank manipulations, such as adding substrate to the tank bottom (Zydlewski et al 2003;Hyvärinen and Rodewald 2013;Näslund et al 2013) or putting structure such as woody debris, plants, or root wads into the rearing unit (Berejikian et al 1999(Berejikian et al , 2000Berejikian and Tezak 2005;Brockmark et al 2007;Fast et al 2008;Roberts et al 2011), can impede the self-cleaning circular flows, resulting in increased tank-cleaning labor. In addition to providing rearing performance benefits, the rod structures used in this study did not alter the self-cleaning circular flow of water through the tank at either velocity.…”

“…Some techniques, such as changes in tank coloration (Donnelly and Whorisky 1991), have improved survival without requiring additional labor during hatchery rearing. However, most studies attempting to increase structural complexity have used woody debris, stones, or other material in the rearing tanks (Brown et al 2003;Brockmark et al 2007) or a combination of intrusive and extrusive techniques (Maynard et al 1995;Berejikian et al 1999Berejikian et al , 2000Brown et al 2003;Fast et al 2008;Roberts et al 2011;Hyvärinen and Rodewald 2013;Näslund et al 2013), all of which make routine culture chores, such as tank cleaning, more difficult and time-consuming.…”

“…While studies examining structural complexity typically focus on poststocking performance (Berejikian et al 1999;Brockmark et al 2007;Fast et al 2008;Hyvärinen and Rodewald 2013), there is a paucity of information on the effects of such treatments on hatchery rearing performance. Brockmark et al (2007) indicated that Atlantic Salmon Salmo salar may grow faster in enhanced hatchery environments, and Berejikian et al (2000) reported similar observations with Steelhead Trout Oncorhynchus mykiss.…”

Effects of Passive Integrated Transponder Tags on Smolt‐to‐Adult Recruit Survival, Growth, and Behavior of Hatchery Spring Chinook Salmon

“…Beginning with the 1998 brood, improved tag technology and installation of detection equipment at the acclimation sites allowed the number of PIT-tagged fish released to be based on tag detections at raceway outlets. PIT tag detection efficiency at the acclimation sites after brood year 1997 was estimated to be greater than 99% (Fast et al 2008). The total numbers of PIT-tagged and NPT hatchery juveniles released by brood year are given in Table 1.…”

Use of Bottom Structure and Tank Cover during Rainbow Trout Rearing in Circular Tanks

“…For example, many studies have placed natural materials such as woody debris, plants, and root wads on the bottom of hatchery rearing tanks [2,[7][8][9][10][11], but those materials may interfere with the self-cleaning nature of circular rearing tanks by altering water flow patterns. This leads to more frequent tank cleanings because of an increase of food and feces trapped in structures [12].…”