Kevin A. Meyer

Adaptation of redband trout in desert and montane environments

Natural populations that evolve under extreme climates are likely to diverge because of selection in local environments. To explore whether local adaptation has occurred in redband trout (Oncorhynchus mykiss gairdneri) occupying differing climate regimes, we used a limited genome scan approach to test for candidate markers under selection in populations occurring in desert and montane streams. An environmental approach to identifying outlier loci, spatial analysis method and linear regression of minor allele frequency with environmental variables revealed six candidate markers (P < 0.01). Putatively neutral markers identified high genetic differentiation among desert populations relative to montane sites, likely due to intermittent flows in desert streams. Additionally, populations exhibited a highly significant pattern of isolation by temperature (P < 0.0001) and those adapted to the same environment had similar allele frequencies across candidate markers, indicating selection for differing climates. These results imply that many genes are involved in the adaptation of redband trout to differing environments, and selection acts to reinforce localization. The potential to predict genetic adaptability of individuals and populations to changing environmental conditions may have profound implications for species that face extensive anthropogenic disturbances.

Reproductive demographics and factors that influence length at sexual maturity of Yellowstone cutthroat trout in Idaho

Abstract Length and age at sexual maturity for Yellowstone cutthroat trout Oncorhynchus clarki bouvieri vary across their historical range, but the factors that influence this variation are poorly understood. We collected 610 Yellowstone cutthroat trout from 11 populations across southeastern Idaho from streams and rivers with a variety of physical characteristics to determine length and age at sexual maturity and other reproductive demographics. The oldest Yellowstone cutthroat trout captured (age 10) was from the South Fork Snake River; most fish (90%) were between ages 2 and 4, and only three (<1%) were older than age 7 (all from the South Fork Snake River). Cutthroat trout from the South Fork Snake River did not mature until they were 300 mm long and 5 years of age, whereas cutthroat trout from other migratory and resident sites began maturing at ages 2–3 and lengths of 100–150 mm. Fish 100–250 mm long were much more likely to be mature if they were from sites with resident rather than migratory repro...

Evaluation of an Unsuccessful Brook Trout Electrofishing Removal Project in a Small Rocky Mountain Stream

In the western United States, exotic brook trout Salvelinus fontinalis frequently have a deleterious effect on native salmonids, and biologists often attempt to remove brook trout from streams by means of electrofishing. Although the success of such projects typically is low, few studies have assessed the underlying mechanisms of failure, especially in terms of compensatory responses. A multiagency watershed advisory group (WAG) conducted a 3-year removal project to reduce brook trout and enhance native salmonids in 7.8 km of a southwestern Idaho stream. We evaluated the costs and success of their project in suppressing brook trout and looked for brook trout compensatory responses, such as decreased natural mortality, increased growth, increased fecundity at length, and earlier maturation. The total number of brook trout removed was 1,401 in 1998, 1,241 in 1999, and 890 in 2000; removal constituted an estimated 88% of the total number of brook trout in the stream in 1999 and 79% in 2000. Although abundance of age-1 and older brook trout declined slightly during and after the removals, abundance of age-0 brook trout increased 789% in the entire stream 2 years after the removals ceased. Total annual survival rate for age-2 and older brook trout did not decrease during the removals, and the removals failed to produce an increase in the abundance of native redband trout Oncorhynchus mykiss gairdneri. Lack of a meaningful decline and unchanged total mortality for older brook trout during the removals suggest that a compensatory response occurred in the brook trout population via reduced natural mortality, which offset the removal of large numbers of brook trout. Although we applaud WAG personnel for their goal of enhancing native salmonids by suppressing brook trout via electrofishing removal, we conclude that their efforts were unsuccessful and suggest that similar future projects elsewhere over such large stream lengths would be costly, quixotic enterprises.

Status of Yellowstone Cutthroat Trout in Idaho

Abstract In this study, we electrofished 961 study sites to estimate the abundance of trout (in streams only) throughout the upper Snake River basin in Idaho (and portions of adjacent states) to determine the current status of Yellowstone cutthroat trout Oncorhynchus clarkii bouvierii and other nonnative salmonids and to assess introgressive hybridization between Yellowstone cutthroat trout and rainbow trout O. mykiss. Yellowstone cutthroat trout were the most widely distributed species of trout, followed by brook trout Salvelinus fontinalis, rainbow trout and rainbow trout × Yellowstone cutthroat trout hybrids, and brown trout Salmo trutta. Of the 457 sites that contained Yellowstone cutthroat trout, less than half also contained nonnative salmonids and only 88 contained rainbow trout and hybrids. In the 11 geographic management units (GMUs) for which sample size permitted abundance estimates, the number of 100-mm and larger trout was estimated to be about 2.2 ± 1.2 million (mean ± confidence interval); ...

Effects of Cobble–Boulder Substrate Configuration on Winter Residency of Juvenile Rainbow Trout

Abstract We assessed first winter habitat use by placing wild rainbow trout Oncorhynchus mykiss (52–155 mm total length) in wire-mesh enclosures with different cover treatments and at varying fish densities. Cobble–boulders substrates (20–40 cm diameter) were arranged in four different configurations: (1) no cobble–boulders, (2) cobble–boulders present but not touching, (3) cobble–boulders touching in a single layer, and (4) cobble–boulders touching and stacked in two layers. As the configuration of rock substrate was changed to create more concealment cover, the number of fish remaining in the enclosures after 96 h increased significantly, even though the quantity of rock substrate did not change. The initial stocking density of fish had no overall significant effect on the number of fish remaining in enclosures after 96 h. However, analysis of each cover × density treatment showed that when the substrate arrangement created little concealment cover, the number of fish remaining in the enclosures did not...

A Reward-Recovery Study to Estimate Tagged-Fish Reporting Rates by Idaho Anglers

Abstract From 2006 to 2009, we tagged and released 22,202 fish with T-bar anchor tags valued at US

Accuracy of Removal Electrofishing Estimates of Trout Abundance in Rocky Mountain Streams

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Environmental Factors Related to the Distribution, Abundance, and Life History Characteristics of Mountain Whitefish in Idaho

200 if returned. Our intent was to assess angler tag reporting rates in Idaho and to determine whether reporting rates declined over time or differed between species. A total of 4,643 tags were reported by anglers. Assuming a reporting rate of 100% for

Survival and Dispersal of Hatchery Triploid Rainbow Trout in an Idaho River

200 tags, weighted mean reporting rates were 54.2% for

Sex Ratio, Fecundity, and Models Predicting Length at Sexual Maturity of Redband Trout in Idaho Desert Streams

0 tags, 69.7% for