Comparison of Subyearling Fall Chinook Salmon's Use of Riprap Revetments and Unaltered Habitats in Lake Wallula of the Columbia River

Abstract

Subyearling fall chinook salmon's Oncorhynchus tshawytscha use of unaltered and riprap habitats in Lake Wallula of the Columbia River was determined with point abundance data collected by electrofishing in May 1994 and 1995. We documented the presence or absence of subyearlings at 277 sample sites and collected physical habitat information at each site. Based on logistic regression, we found that the probability of fish presence was greater in unaltered shoreline habitats than in riprap habitats. Substrate size was the most important factor in determining fish presence, with dominant substrates larger than 256 mm having the lowest probability of fish presence. Water velocity, also included in our model due to its biological importance, was not a significant factor affecting presence or absence (P = 0.1102). The correct prediction rate of fish presence or absence in our sample sites using cross validation was 67%. Our model showed that substrate was the most important factor determining subyearling habitat use, but the model did not include other habitat variables known to be important to subyearlings in more diverse systems. We suggest that resource managers consider alternative methods of bank stabilization that are compatible with the habitat requirements of the fish that use them.

Ecology of freshwater shore zones

“…There are exceptions to these patterns, of course. Juvenile Chinook salmon were more likely to be found over gravel bottoms than in structurally complex riprap in a western reservoir (Garland et al 2002), consistent with the observation that added artificial structure rarely enhances local densities of salmonids in lakes (Bolding et al 2004).…”

Juvenile Chinook Salmon Mortality in a Snake River Reservoir: Smallmouth Bass Predation Revisited

“…We generally collected more Smallmouth Bass in riprap habitat of the CON reach, which provided more cover (Munther ; Todd and Rabeni ), but this type of habitat is not preferred by juvenile Chinook Salmon (Garland et al. ). In contrast, we often observed higher Smallmouth Bass abundance in sandy natural habitat in the SRTZ reach that was likely used by Smallmouth Bass for spawning.…”

Seaward migrating subyearling chinook salmon avoid overhead cover

“…overhanging riparian vegetation, undercut banks, or man‐made structures such as docks and piers) for proximity to the littoral zone. Indeed, it appears that although as fry, chinook salmon rear along the shallow river margins (Garland et al ., 2002; Tiffan et al ., 2002), as smolts they move offshore to migrate after an initial period of dispersal along the shoreline (Connor et al ., 2003). This avoidance of near‐bank areas may reduce predator vulnerability and enhance migration efficiency.…”