The Effects of Rearing Density on Growth, Fin Erosion, Survival, and Migration Behavior of Hatchery Winter Steelhead

Abstract

Juvenile winter steelhead Oncorhynchus mykiss at Eagle Creek National Fish Hatchery in Estacada, Oregon, were reared for three brood years (2004–2006) at raceway densities of 7,500 (214 fish/m3), 15,000 (429 fish/m3), and 22,500 fish (643 fish/m3) to determine the effects of rearing density on growth, fin erosion, survival, adult yield, and migration behavior. Coded wire tags were used to evaluate adult survival, and fish were radio‐tagged to monitor migration times from the hatchery to the mouth of Eagle Creek following volitional release from the hatchery. We found rearing density had a significant effect (P < 0.05) on steelhead growth, fin erosion, and adult survival. Winter steelhead reared in low‐density raceways (13.6 kg/m3 at release) were significantly larger at release, larger at return, had significantly better dorsal fin condition, and had significantly greater smolt‐to‐adult survival rates than did those reared in medium (23.4 kg/m3) and high (35.2 kg/m3) density raceways. No significant relationship between smolt size at release and migration timing was detected; however, the effect of rearing density on fish migration was noticeable in brood year 2004. In that year (2004), smolts from the medium‐ and high‐density groups took from 6 to15 d longer to out‐migrate than those from the low‐density group.

Endangered species managing endangered species: Polyculture of piscivorous Colorado Pikeminnow (Ptychocheilus lucius) with production Bonytail (Gila elegans) to control recruitment and increase growth rates

“…Although several studies have evaluated aquaculture techniques (i.e., cage culture, diet improvement, polyculture and thermal regimes) to facilitate Bonytail growth (Henne et al, ; Kappenman et al, ; Sowka & Brunkow, ), the effect of uncontrolled recruitment on growth rates of production fish has not been evaluated. The use of biological controls has been shown to greatly reduce densities (Kavanagh & Olson, ; Ward & Slaney, ; Ward et al, ; Westers, ), and, indeed, our results demonstrated Colorado Pikeminnow to be effective at reducing total biomass. The outcome of this effect was an increase in adult Bonytail growth rates (ΔTL, Δg, %BW and SGR), suggesting polyculture of these two species can improve conservation measures (i.e., augmentation) implemented to aid Bonytail recovery.…”

“…Fish & Wildlife Service); however, in hatchery ponds they are precocious, with individuals reproducing as early as Age‐2 (Hamman, ). Contradictory to positive outcomes associated with natural recruitment within a hatchery system (i.e., increased production), recruitment can have negative impacts on various factors related to overcrowding (Kavanagh & Olson, ; Tatara, Riley, & Scheurer, ; Westers, ). Using polyculture techniques, integrating fish as biological controls, has been shown to effectively control unwanted biota (i.e., non‐native species, pathogen transmitting vectors) and positively effect factors related to fish and the hatchery environment (Chaichana & Jongphadungkiet, ; Frenkel & Goren, ; Lemmens, Mergeay, Vanhove, Meester, & Declerck, ).…”

“…Fish reared in high densities can have higher mortality rates and increased susceptibility to disease relative to fish reared in low densities (Kavanagh & Olson, ; Tatara et al, ; Westers, ). Our results showed no effect of Colorado Pikeminnow on survivorship of adult Bonytail, with high survival rates observed in both control and treatments (Tables and ).…”

Growth, Condition, and Trophic Relations of Stocked Trout in Southern Appalachian Mountain Streams

“…), rearing fish in ponds rather than raceways (Zydlewski et al. ), and decreasing densities in hatcheries (Kavanagh and Olsen ) can improve the physical condition, growth, and survival of hatchery‐reared salmonids. However, the benefits of such actions must outweigh the costs of production and warrant further research in hatchery‐supported southern Appalachian Mountain trout streams.…”

“…Our findings of decreased feeding and the lack of isotopic incorporation may be particularly useful in guiding hatchery and stocking procedures. For instance, enhancing instream structure in hatcheries (Brockmark et al 2007), rearing fish in ponds rather than raceways (Zydlewski et al 2003), and decreasing densities in hatcheries (Kavanagh and Olsen 2014) can improve the physical condition, growth, and survival of hatcheryreared salmonids. However, the benefits of such actions must outweigh the costs of production and warrant further research in hatchery-supported southern Appalachian Mountain trout streams.…”