Seasonal foraging and piscivory by sympatric wild and hatchery-reared steelhead from an integrated hatchery program

Simpson, William G.; Kennedy, Benjamen M.; Ostrand, Kenneth G.

doi:10.1007/s10641-009-9542-z

Cited by 7 publications

(8 citation statements)

References 42 publications

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“…Regardless, the ecological implications of hatchery fish in the three Hood Canal streams will come primarily from fish greater than 200 mm, which were also more abundant than small residuals in each of the three streams. The incidence of predation by steelhead smolts and Proportion of population N=100 for each of three raceways (1-3) of age-1 smolts and each of two raceways (4 and 5) of S2 smolts summer residuals on juvenile salmon is typically very low (Sharpe et al 2008;Simpson et al 2009), but in rare cases can be a substantial source of mortality for juvenile salmon (Naman and Sharpe 2011). Interference competition between hatchery and wild juvenile salmonids is strongly determined by relative body size, and intraspecific competition appears to be more intense than interspecific competition (Tatara and Berejikian 2011).…”

Section: Body Size Maturity and Residualismmentioning

confidence: 99%

Development of natural growth regimes for hatchery-reared steelhead to reduce residualism, fitness loss, and negative ecological interactions

et al. 2011

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Wild steelhead (Oncorhynchus mykiss) typically spend two or more years in freshwater before migrating to sea, but hatchery steelhead are almost ubiquitously released as yearlings. Their large size at release coupled with life history pathways that include both male and female maturation in freshwater present ecological risks different from those posed by hatchery populations of Pacific salmon. Yearling hatchery reared steelhead that fail to attain minimum thresholds for smoltification or exceed thresholds for male maturation tend to 'residualize' (i.e., remain in freshwater). Residuals pose ecological risks including size-biased interference competition and predation on juvenile salmon and trout. Three hatchery populations of steelhead in Hood Canal, WA were reared under growth regimes designed to produce a more natural age at smoltification (age-2) to aid in rebuilding their respective natural populations. Mean smolt sizes and size variability at age-2 were within the range of wild smolts for two of the three populations. The third population reared at a different facility under similar temperatures exhibited high growth rate variability and high male maturation rates (20% of all released fish). Experimentally comparing age-1 and age-2 smolt programs will help identify optimal rearing strategies to reduce the genetic risk of domestication selection and reduce residualism rates and associated negative ecological effects on natural populations. Investigations of Winthrop National Fish Hatchery summer-run steelhead will measure a) selection on correlated behavioral traits ('behavioral syndromes'), b) degree of smoltification, c) changes in hormones that regulate gonad growth at key developmental stages, and d) conduct extensive post-release monitoring of fish reared under each growth regime.

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Section: Body Size Maturity and Residualismmentioning

confidence: 99%

Development of natural growth regimes for hatchery-reared steelhead to reduce residualism, fitness loss, and negative ecological interactions

et al. 2011

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“…Simpson et al (2009) found that hatchery steelhead smolts released in mid-April consumed significantly more subyearling salmonids than those released in May. For potential prey species like wild steelhead that emerge from spawning gravels in April and May, reducing the spatial overlap of predator and prey may be the most effective way to reduce the predation rate.…”

Section: Managing the Predation Ratementioning

confidence: 99%

“…Other than the research performed by Hawkins and Tipping (1999) and Simpson et al (2009), all of the documents were contract reports or other forms of grey literature and had not been published at the time of this review. Two of the studies examined predation by yearling coho salmon (Oncorhynchus kisutch), while twelve examined predation by hatchery steelhead (O. mykiss).…”

Section: Literature Reviewmentioning

confidence: 99%

“…Residualism of yearling hatchery smolts occurs when the smolts fail to migrate by early or mid-June of the same calendar year in which the smolts were released (Viola and Schuck 1995;Simpson et al 2009). Releasing hatchery fish that are ready to smolt upon release can reduce the number of subyearlings consumed.…”

Section: Managing the Predator Populationmentioning

confidence: 99%

“…Fritts and Pearsons 2004;Naughton et al 2004). Only two peer-reviewed studies, one by Hawkins and Tipping (1999) and another by Simpson et al (2009), addressed predation by hatchery yearling salmonids on wild subyearling salmonids. However, there are a variety of contract reports and technical memoranda on the subject.…”

Section: Introductionmentioning

confidence: 99%

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Predation by hatchery yearling salmonids on wild subyearling salmonids in the freshwater environment: A review of studies, two case histories, and implications for management

Naman

Sharpe

2011

Environ Biol Fish

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We conducted a literature review on predation by hatchery yearling salmonids on wild subyearling salmonids in the western United States. The review included 14 studies from the Pacific Northwest and California. In most instances, predation by hatchery yearling salmonids on wild subyearling salmonids occurred at low levels. However, when multiple factors contributing to the incidence of predation were met, localized areas of heavy predation were noted. Total prey consumed ranged from 456 to 111 000 subyearlings for the few studies in which enough information was gathered to make the estimate. We examined two of these studies in more detail: one detecting relatively low predation in four western Washington rivers and one detecting relatively high predation in the Trinity River in northern California. In the case of the rivers in western Washington, over 70% of wild subyearlings had migrated by the time hatchery steelhead were planted and those remaining had grown large enough to reduce their vulnerability to predation. In the case of the Trinity River, less than 20% of wild subyearlings had migrated by the time hatchery steelhead were planted and most were small enough to remain highly vulnerable to predation. We found that managers can effectively minimize the predation rate of hatchery yearling salmonids by reducing the spatial or temporal overlap of predator and prey. Unknown is the extent to which low predation rates, which likely occur in most places hatchery yearlings are released, might still negatively impact prey populations that are at low abundance because of other anthropogenic factors.

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Size and Distribution of Parr Produced from Natural‐ and Hatchery‐Origin Steelhead Spawning Naturally in a Small Pacific Northwest Coastal Stream

et al. 2022

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Recent studies suggest that steelhead Oncorhynchus mykiss produced from local hatchery‐origin (HOR) adults have lower lifetime fitness than their natural‐origin (NOR) counterparts. To increase our understanding of this pattern, we compared age‐1 parr size and distribution produced by a local integrated population of HOR and NOR adults spawning naturally across a range of environmental conditions. Across 8 years, we used genetic parentage assignments and field measurements of parr in conjunction with creek temperature and flow data to find small, nonbiologically significant differences in size between parr of different parent origins. This suggests that parr produced by HOR adults are acquiring enough resources to grow at a rate similar to that of parr produced by NOR adults. In contrast to origin, we found strong positive associations between mean size of parr and annual mean water temperature and summer flow. Additionally, the distribution of parr was similar and HOR‐produced parr were not skewed relative to the location of the hatchery. Parr occupying the full extent of accessible and suitable habitat might be a positive outcome for hatchery programs seeking to supplement an existing population or replace an extirpated population. However, these results also imply that HOR fish could be competing with NOR fish for food and space, which might be less desirable if the goal of the hatchery program is harvest and not supplementation. Our results highlight the importance of clearly articulated goals for the hatchery program, as the observed pattern could be deemed a benefit or a risk depending on the hatchery's purpose. Lastly, projections for higher water temperatures and reduced summer flows, when considered in the context of the correlations we observed for size of parr, imply that coastal steelhead populations could start experiencing negative climate impacts with respect to steelhead parr growth metrics during the summer in the next few decades.

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Seasonal foraging and piscivory by sympatric wild and hatchery-reared steelhead from an integrated hatchery program

Cited by 7 publications

References 42 publications

Development of natural growth regimes for hatchery-reared steelhead to reduce residualism, fitness loss, and negative ecological interactions

Development of natural growth regimes for hatchery-reared steelhead to reduce residualism, fitness loss, and negative ecological interactions

Predation by hatchery yearling salmonids on wild subyearling salmonids in the freshwater environment: A review of studies, two case histories, and implications for management

Size and Distribution of Parr Produced from Natural‐ and Hatchery‐Origin Steelhead Spawning Naturally in a Small Pacific Northwest Coastal Stream

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