Snorkeling as an Alternative to Depletion Electrofishing for Estimating Abundance and Length-Class Frequencies of Trout in Small Streams

Mullner, Scott A.; Hubert, Wayne A.; Wesche, Thomas A.

doi:10.1577/1548-8675(1998)018<0947:saaatd>2.0.co;2

Cited by 63 publications

(58 citation statements)

References 20 publications

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“…The South Fork (SF) Calawah and mainstem Calawah River flow westward for 33.8 and either too small to sample with a boat-mounted electrofisher, or too large to sample with a backpack electrofisher (Cunjack et al 1988, Zubick and Fraley 1988, Thurow and Schill 1996, Mullner et al 1998, Joyce and Hubert 2003. To reduce potential observational bias between multiple divers, a single experienced diver sampled all sites (Hankin and Reeves 1988).…”

Section: Study Areamentioning

confidence: 99%

Polymorphic mountain whitefish (Prosopium williamsoni) in a coastal riverscape: size class assemblages, distribution, and habitat associations

Starr

Torgersen

2014

Ecology of Freshwater Fish

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Polymorphic mountain whitefish (Prosopium williamsoni) in a coastal riverscape:Size class assemblages, distribution, and habitat associations James Chamberlain StarrChair of Supervisory Committee: Affiliate Assistant Professor Christian E. Torgersen School of Environmental and Forest SciencesFluvial mountain whitefish (Prosopium williamsoni) offer a rare example of trophic polymorphism among stream dwelling salmonids in temperate North American river systems.Trophic polymorphism is a form of resource-based phenotypic diversification that occurs when exploitation of under-utilized resources necessitates specific morphological characteristics.Studies of trophic polymorphism in the species are few, focusing on diet, foraging behavior, genetic variation, and snout morphology. Pinocchio whitefish develop an elongated snout used to overturn substrate while foraging for benthic invertebrates, whereas normal whitefish have an even sloping head shape and feed primarily on drifting prey. I hypothesized that (1) morphotypes would be associated with distinctly different habitat features based on known feeding behavior and diet, and (2) these differences in habitat association would segregate morphotypes at channel unit and reach scales. In this study, I first compared the spatial distributions of morphotypes and size classes. I then assessed the assemblage structure of morphotypes and size classes and their relationships with aquatic habitat. Finally, I quantified the associations between specific morphotypes and longitudinal variation in aquatic habitat. Spatially continuous sampling was conducted over a broad extent (29 km) in the Calawah River, WA (USA). Whitefish were enumerated via snorkeling in three size classes: small (10-29 cm), medium (30-49 cm), and large (≥ 50 cm). Spatial distributions were compared among size classes of morphotypes by relating cumulative abundance to distance upstream. Assemblage structure and relationships with aquatic habitat were assessed with non-metric multidimensional scaling (NMS). Unit-scale differences between morphotypes in pool and non-pool habitats were quantified with Wilcoxon rank sum tests. Associations between specific morphotypes and habitat were quantified at the 1-km reach scale with generalized additive models (GAMs) using thin-plate regression splines. Large size classes of both morphotypes were distributed downstream of small and medium size classes, and normal whitefish were distributed downstream of pinocchio whitefish. Normal whitefish size classes were associated with higher gradient and depth, whereas pinocchio whitefish size classes were positively associated with pool area, distance upstream, and depth. Normal whitefish relative density did not differ between habitat types at the unit scale (p = 0.34, W = 3085), but pinocchio whitefish were more dense in pool habitat than in non-pool habitat (p < 0.0001, W = 1084). Reach-scale GAMs indicated that normal whitefish were associated with larger substrate size in downstream reaches (R 2 = 0.64), and pinocchio wh...

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Section: Study Areamentioning

confidence: 99%

Polymorphic mountain whitefish (Prosopium williamsoni) in a coastal riverscape: size class assemblages, distribution, and habitat associations

Starr

Torgersen

2014

Ecology of Freshwater Fish

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“…Stream fishes have long been observed and counted by divers with mask and snorkel (Cunjak et al, 1988;Mullner et al, 1998;Roni and Fayram, 2000). However, only recently have spatially continuous distributions of fish abundance and species composition been mapped by visual surveys.…”

Section: Field Measurementmentioning

confidence: 99%

Spatial Identification of Tributary Impacts in River Networks

Torgersen

Gresswell

Bateman

et al. 2008

River Confluences, Tributaries and the Fluvial Network

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“…Small-mesh seines and electrofishing are widely used in surveys of stream fishes (e.g., Anderson et al 1995;Walser and Bart 1999;Oronato et al 2000;Rinne et al 2005) because they are generally assumed to provide reliable estimates of relative fish abundance and have low equipment and labor costs (Pierce et al 1990). In streams with good water clarity, visual methods provide a cost-effective and non-destructive alternative to seining and electrofishing (Mullner et al 1998), especially for threatened and endangered species that require minimal handling and habitat disturbance.…”

Section: Introductionmentioning

confidence: 99%

“…Visual methods have been used extensively to monitor marine fish populations (Bortone et al 2000) and are gaining popularity among researchers studying population size and age distribution, habitat selection, and competitive interactions in freshwater fishes (e.g., Fausch and White 1981;Schill and Griffith 1984;Moyle and Baltz 1985;Greenberg 1988;Hankin and Reeves 1988;Grossman and Ratajczak 1998;Mullner et al 1998). Visual surveys can provide precise indices of fish abundance (Northcote and Wilkie 1963;Schill and Griffith 1984;Hankin and Reeves 1988;Heggenes et al 1990;Rodgers et al 1992;Mullner et al 1998).…”

Section: Introductionmentioning

confidence: 99%

“…Visual surveys can provide precise indices of fish abundance (Northcote and Wilkie 1963;Schill and Griffith 1984;Hankin and Reeves 1988;Heggenes et al 1990;Rodgers et al 1992;Mullner et al 1998). Finally, visual surveys provide more detailed information about microhabitat use than seining, electrofishing, or other intrusive methods that alter fish behavior (Brosse et al 2001;Peterson et al 2004).…”

Section: Introductionmentioning

confidence: 99%

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Comparison of visual survey and seining methods for estimating abundance of an endangered, benthic stream fish

et al. 2007

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We compared visual survey and seining methods for estimating abundance of endangered Okaloosa darters, Etheostoma okaloosae, in 12 replicate stream reaches during August 2001. For each 20-m stream reach, two divers systematically located and marked the position of darters and then a second crew of three to five people came through with a small-mesh seine and exhaustively sampled the same area. Visual surveys required little extra time to complete. Visual counts (24.2 ± 12.0; mean ± one SD) considerably exceeded seine captures (7.4 ± 4.8), and counts from the two methods were uncorrelated. Visual surveys, but not seines, detected the presence of Okaloosa darters at one site with low population densities. In 2003, we performed a depletion removal study in 10 replicate stream reaches to assess the accuracy of the visual survey method. Visual surveys detected 59% of Okaloosa darters present, and visual counts and removal estimates were positively correlated. Taken together, our comparisons indicate that visual surveys more accurately and precisely estimate abundance of Okaloosa darters than seining and more reliably detect presence at low population densities. We recommend evaluation of visual survey methods when designing programs to monitor abundance of benthic fishes in clear streams, especially for threatened and endangered species that may be sensitive to handling and habitat disturbance.

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Snorkeling as an Alternative to Depletion Electrofishing for Estimating Abundance and Length-Class Frequencies of Trout in Small Streams

Cited by 63 publications

References 20 publications

Polymorphic mountain whitefish (Prosopium williamsoni) in a coastal riverscape: size class assemblages, distribution, and habitat associations

Polymorphic mountain whitefish (Prosopium williamsoni) in a coastal riverscape: size class assemblages, distribution, and habitat associations

Spatial Identification of Tributary Impacts in River Networks

Comparison of visual survey and seining methods for estimating abundance of an endangered, benthic stream fish

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