Snake River Sockeye Salmon Habitat and Limnological Research : 2008 Annual Progress Report.

Kohler, Andre E.; Griswold, Robert G.; Taki, Doug

doi:10.2172/965259

Cited by 1 publication

(15 citation statements)

References 6 publications

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“…Densities of O. nerka varied considerably among lakes and years, driven by reintroduction efforts (stocking of Sockeye Salmon adults, embryos, and parr; Table 2) and natural variation in kokanee abundance (Figure 3) (Eaton et al 2020;Johnson et al 2020). Inverse relationships between O. nerka abundance (or density) and zooplankton biomass have been widely reported for Sockeye Salmon (Foerster 1944;Goodlad et al 1974;Koenings and Kyle 1997;Wood et al 1999) and kokanee (Rieman and Myers 1992), evidence that O. nerka grazing commonly regulates zooplankton populations.…”

Section: Discussionmentioning

confidence: 94%

“…We operated smolt traps annually at the outlet streams of Pettit and Alturas lakes, and the IDFG operated a smolt trap in Redfish Lake Creek below the outlet of Redfish Lake to capture out‐migrating smolts during April–June (Eaton et al. 2020; Johnson et al. 2020).…”

Section: Methodsmentioning

confidence: 99%

“…Smolt trapping.-We operated smolt traps annually at the outlet streams of Pettit and Alturas lakes, and the IDFG operated a smolt trap in Redfish Lake Creek below the outlet of Redfish Lake to capture out-migrating smolts during April-June (Eaton et al 2020;Johnson et al 2020). We used mark-recapture techniques to estimate trap efficiencies and smolt abundance from each lake (see Venditti et al 2017).…”

Section: Methodsmentioning

confidence: 99%

“…We identified (natural or hatchery), enumerated, measured (fork length; mm), and weighed (AE0.1 g) captured Sockeye Salmon smolts. We collected scales across size-classes to infer age at size (Eaton et al 2020;Johnson et al 2020). We based fish age on emergence date, (e.g., embryos hatch during spring [May 1], rear inlake as age 0+ during the summer and fall, then outmigrate as age-1 smolt the following spring).…”

Section: Methodsmentioning

confidence: 99%

“…Three O. nerka ecotypes (anadromous and residual Sockeye Salmon and kokanee) are present in the Sawtooth Valley lakes, although the relative proportions and stocking and management histories vary among lakes (Eaton et al 2020;Johnson et al 2020). In this paper, when unable to distinguish among the various ecotypes, we use the collective term "O.…”

Section: Study Areamentioning

confidence: 99%

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Density Dependence in Three Snake River Sockeye Salmon Nursery Lakes in Central Idaho

Griswold¹,

Kohler

Tardy

et al. 2022

N American J Fish Manag

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Snake River Sockeye Salmon Oncorhynchus nerka, listed as an endangered species in 1991, currently inhabit three nursery lakes (Redfish, Pettit, and Alturas lakes) in the Sawtooth Valley, Idaho. Conspecific kokanee (lacustrine Sockeye Salmon) are also present in the lakes. Snake River Sockeye Salmon recovery efforts, initially focused on genetic conservation, are now attempting to rebuild naturally spawning populations using hatchery supplementation. However, in Sockeye Salmon nursery lakes, density dependence is frequently observed when elevated O. nerka abundance leads to declines in zooplankton biomass, body size, and shifts in community composition. In turn, these changes lead to reductions in juvenile O. nerka growth rates, survival, and adult returns. We examined a long‐term data set of O. nerka population metrics and associated zooplankton community metrics. We found evidence of density dependence within and among nursery lakes. We detected differences in zooplankton biomass, lengths of preferred zooplankton prey (Daphnia spp. and cyclopoid copepods), parr growth rates, and age‐1 smolt size among the three lakes. We found negative relationships between O. nerka density and zooplankton biomass and size. We identified positive relationships between zooplankton biomass and two response variables: smolt size at migration and growth rates of hatchery parr. The relationships were generally similar among lakes. Variable outcomes were a result of differences in O. nerka density (or zooplankton biomass), controlled primarily by the relative proportion of spawning and rearing habitat in each lake. Understanding unique lake habitats, ecological interactions, and the role of density dependence is germane to management of Snake River Sockeye Salmon populations.

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