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Phaedra Budy - One of the best experts on this subject based on the ideXlab platform.
flow management and fish density regulate salmonid recruitment and adult size in tailwaters across western north americaEcological Applications, 2015Co-Authors: Kimberly L Dibble, Charles B Yackulic, Theodore A Kennedy, Phaedra BudyAbstract:
Rainbow and brown Trout have been intentionally introduced into tailwaters downriver of dams globally and provide billions of dollars in economic benefits. At the same time, recruitment and maximum length of Trout populations in tailwaters often fluctuate erratically, which negatively affects the value of fisheries. Large recruitment events may increase dispersal downriver where other fish species may be a priority (e.g., endangered species). There is an urgent need to understand the drivers of Trout population dynamics in tailwaters, in particular the role of flow management. Here, we evaluate how flow, fish density, and other physical factors of the river influence recruitment and mean adult length in tailwaters across western North America, using data from 29 dams spanning 1-19 years. Rainbow Trout recruitment was negatively correlated with high annual, summer, and spring flow and dam latitude, and positively correlated with high winter flow, subadult brown Trout catch, and reservoir storage capacity. Brown Trout recruitment was negatively correlated with high water velocity and daily fluctuations in flow (i.e., hydropeaking) and positively correlated with adult rainbow Trout catch. Among these many drivers, rainbow Trout recruitment was primarily correlated with high winter flow combined with low spring flow, whereas brown Trout recruitment was most related to high water velocity. The mean lengths of adult rainbow and brown Trout were influenced by similar flow and catch metrics. Length in both species was positively correlated with high annual flow but declined in tailwaters with high daily fluctuations in flow, high catch rates of conspecifics, and when large cohorts recruited to adult size. Whereas brown Trout did not respond to the proportion of water allocated between seasons, rainbow Trout length increased in rivers that released more water during winter than in spring. Rainbow Trout length was primarily related to high catch rates of conspecifics, whereas brown Trout length was mainly related to large cohorts recruiting to the adult size class. Species-specific responses to flow management are likely attributable to differences in seasonal timing of key life history events such as spawning, egg hatching, and fry emergence.
North American Journal of Fisheries Management, 2015Co-Authors: Konrad Hafen, Phaedra BudyAbstract:
AbstractThe popularity of reservoirs to support sport fisheries has led to the stocking of species that did not co-evolve, creating novel reservoir fish communities. In Utah, the Bear Lake strain of Bonneville Cutthroat Trout Oncorhynchus clarkii utah and tiger Trout (female Brown Trout Salmo trutta × male Brook Trout Salvelinus fontinalis) are being more frequently added to a traditional stocking regimen consisting primarily of Rainbow Trout O. mykiss. Interactions between these three predatory species are not well understood, and studies evaluating community interactions have raised concern for an overall decrease of Trout condition. To evaluate the potential for negative interactions among these species, we tested aggression in laboratory aquaria using three-species and pairwise combinations at three densities. Treatments were replicated before and after feeding. During the three-species trials Rainbow Trout initiated 24.8 times more aggressive interactions than Cutthroat Trout and 10.2 times more aggr...
an experimental evaluation of competitive and thermal effects on brown Trout salmo trutta and bonneville cutthroat Trout oncorhynchus clarkii utah performance along an altitudinal gradientCanadian Journal of Fisheries and Aquatic Sciences, 2005Co-Authors: Peter A Mchugh, Phaedra BudyAbstract:
Temperature-mediated competition (i.e., dominance shifts between species depending on temperature) may explain the segregation of salmonid species along altitudinal stream gradients. We evaluated this hypothesis for exotic brown Trout (Salmo trutta) and native Bonneville cutthroat Trout (Oncorhynchus clarkii utah) by rearing them in experi- mental sympatry and allopatry using enclosures constructed at six sites spaced along a 45-km segment of a mountain stream. For both species, we compared condition and growth between allopatric and sympatric treatment groups. We found that brown Trout negatively affected cutthroat Trout performance, whereas cutthroat Trout failed to impart an effect in the reverse direction, regardless of temperature. Thus, we documented asymmetric competition between these species but found little evidence indicating that its outcome was influenced by temperature. Brown Trout - cutthroat Trout seg- regation is therefore unlikely to be due to temperature-mediated competition. Instead, brown Trout may have displaced cutthroat Trout from downstream areas through competition or other mechanisms, while abiotic factors preclude their (brown Trout) invasion of upper elevations. Given the magnitude of effect observed in our study, we recommend that brown Trout receive greater consideration in cutthroat Trout conservation.
David A. Beauchamp - One of the best experts on this subject based on the ideXlab platform.
lake Trout salvelinus namaycush suppression for bull Trout salvelinus confluentus recovery in flathead lake montana north americaHydrobiologia, 2016Co-Authors: Michael J Hansen, Barry S Hansen, David A. BeauchampAbstract:
Non-native lake Trout Salvelinus namaycush displaced native bull Trout Salvelinus confluentus in Flathead Lake, Montana, USA, after 1984, when Mysis diluviana became abundant following its introduction in upstream lakes in 1968–1976. We developed a simulation model to determine the fishing mortality rate on lake Trout that would enable bull Trout recovery. Model simulations indicated that suppression of adult lake Trout by 75% from current abundance would reduce predation on bull Trout by 90%. Current removals of lake Trout through incentivized fishing contests has not been sufficient to suppress lake Trout abundance estimated by mark-recapture or indexed by stratified-random gill netting. In contrast, size structure, body condition, mortality, and maturity are changing consistent with a density-dependent reduction in lake Trout abundance. Population modeling indicated total fishing effort would need to increase 3-fold to reduce adult lake Trout population density by 75%. We conclude that increased fishing effort would suppress lake Trout population density and predation on juvenile bull Trout, and thereby enable higher abundance of adult bull Trout in Flathead Lake and its tributaries.
Ecological Applications, 2003Co-Authors: James R. Ruzycki, David A. Beauchamp, Daniel L. YuleAbstract:
The establishment of a reproducing population of nonnative lake Trout (Salvelinus namaycush) poses a serious threat to the integrity of the Yellowstone Lake ecosystem, particularly to the indigenous cutthroat Trout (Oncorhynchus clarki bouvieri). We used standard fisheries techniques to quantify the population-level impact resulting from this introduction, while the U.S. National Park Service (NPS) developed a program to control their numbers. Lake Trout diets, thermal history, growth, and size structure were incorporated into a bioenergetics model to estimate the predatory impact of introduced lake Trout and to evaluate the effectiveness of the NPS lake Trout control program. Population size structures were estimated from catches of fish in gill nets that were corrected for mesh size selectivity. Lake Trout abundance was estimated using virtual population (cohort) analysis, and cutthroat Trout abundance was estimated using hydroacoustics. Juvenile cutthroat Trout were highly vulnerable to predation, and ...
Greg Andrusak - One of the best experts on this subject based on the ideXlab platform.
the fishing and natural mortality of large piscivorous bull Trout and rainbow Trout in kootenay lake british columbia 2008 2013PeerJ, 2017Co-Authors: Joseph L Thorley, Greg AndrusakAbstract:
BACKGROUND Estimates of fishing and natural mortality are important for understanding, and ultimately managing, commercial and recreational fisheries. High reward tags with fixed station acoustic telemetry provides a promising approach to monitoring mortality rates in large lake recreational fisheries. Kootenay Lake is a large lake which supports an important recreational fishery for large Bull Trout and Rainbow Trout. METHODS Between 2008 and 2013, 88 large (≥500 mm) Bull Trout and 149 large (≥500 mm) Rainbow Trout were marked with an acoustic transmitter and/or high reward ($100) anchor tags in Kootenay Lake. The subsequent detections and angler recaptures were analysed using a Bayesian individual state-space Cormack-Jolly-Seber (CJS) survival model with indicator variable selection. RESULTS The final CJS survival model estimated that the annual interval probability of being recaptured by an angler was 0.17 (95% CRI [0.11-0.23]) for Bull Trout and 0.14 (95% CRI [0.09-0.19]) for Rainbow Trout. The annual interval survival probability for Bull Trout was estimated to have declined from 0.91 (95% CRI [0.76-0.97]) in 2009 to just 0.46 (95% CRI [0.24-0.76]) in 2013. Rainbow Trout survival was most strongly affected by spawning. The annual interval survival probability was 0.77 (95% CRI [0.68-0.85]) for a non-spawning Rainbow Trout compared to 0.41 (95% CRI [0.30-0.53]) for a spawner. The probability of spawning increased with the fork length for both species and decreased over the course of the study for Rainbow Trout. DISCUSSION Fishing mortality was relatively low and constant while natural mortality was relatively high and variable. The results indicate that angler effort is not the primary driver of short-term population fluctations in the Rainbow Trout abundance. Variation in the probability of Rainbow Trout spawning suggests that the spring escapement at the outflow of Trout Lake may be a less reliable index of abundance than previously assumed. Multi-species stock assessment models need to account for the fact that large Bull Trout are more abundant than large Rainbow Trout in Kootenay Lake.
the fishing and natural mortality of large piscivorous bull Trout and rainbow Trout in kootenay lake british columbia 2008 2013bioRxiv, 2016Co-Authors: Joseph L Thorley, Greg AndrusakAbstract:
Background. Estimates of fishing and natural mortality are important for understanding, and ultimately managing, commercial and recreational fisheries. High reward tags with fixed station acoustic telemetry provides a promising approach to monitoring mortality rates in large lake recreational fisheries. Kootenay Lake is a large lake which supports an important recreational fishery for large Bull Trout and Rainbow Trout. Methods. Between 2008 and 2013, 88 large (≥ 500 mm) Bull Trout and 149 large (≥ 500 mm) Rainbow Trout were marked with an acoustic transmitter and/or high reward ($100) anchor tags in Kootenay Lake. The subsequent detections and angler recaptures were analysed using a Bayesian individual state-space Cormack-Jolly-Seber (CJS) survival model with indicator variable selection. Results. The final CJS survival model estimated that the annual interval probability of being recaptured by an angler was 0.17 (95% CRI 0.11 - 0.23) for Bull Trout and 0.14 (95% CRI 0.09 - 0.19) for Rainbow Trout. The annual interval survival probability for Bull Trout was estimated to have declined from 0.91 (95% CRI 0.77 - 0.97) in 2009 to just 0.45 (95% CRI 0.24 - 0.73) in 2013. Rainbow Trout survival was most strongly affected by spawning. The annual interval survival probability was 0.77 (95% CRI 0.68 - 0.85) for a non-spawning Rainbow Trout compared to 0.42 (95% CRI 0.31 - 0.54) for a spawner. The probability of spawning increased with the fork length for both species and decreased over the course of the study for Rainbow Trout. Discussion. Fishing mortality was relatively low and constant while natural mortality was relatively high and variable. The results are consistent with Kokanee abundance as opposed to angler effort as the primary driver of short-term population fluctations in Rainbow Trout abundance. Multi-species stock assessment models need to account for the fact that large Bull Trout are more abundant than large Rainbow Trout in Kootenay Lake.
Kurt D. Fausch - One of the best experts on this subject based on the ideXlab platform.
when eradication is not an option modeling strategies for electrofishing suppression of nonnative brook Trout to foster persistence of sympatric native cutthroat Trout in small streamsNorth American Journal of Fisheries Management, 2008Co-Authors: Douglas P. Peterson, Kurt D. Fausch, James Watmough, Richard A CunjakAbstract:
Abstract Subspecies of inland cutthroat Trout Oncorhynchus clarkii occupy a fraction of their historic ranges, and displacement by nonnative brook Trout Salvelinus fontinalis is among the greatest threats to existing populations in small, headwater streams. Electrofishing is often used to suppress brook Trout and enhance cutthroat Trout populations, but these efforts are labor intensive and costly. To help managers more effectively plan and implement brook Trout control programs, we used survival estimates from a field experiment to construct matrix population models for both species and linked the models by making the vital rates of young cutthroat Trout a function of brook Trout density to represent the effect of invasion. We then explored the response of cutthroat Trout populations (growth rate [λ] and probability of persistence for 50 years) to brook Trout suppression across various levels of electrofishing frequency, sampling intensity, capture efficiency, and brook Trout immigration rate. Cutthroat ...
Ecological Applications, 2004Co-Authors: Douglas P. Peterson, Kurt D. Fausch, Gary C. WhiteAbstract:
Invasion by nonnative brook Trout (Salvelinus fontinalis) often results in replacement of cutthroat Trout (Oncorhynchus clarki) in the inland western United States, but the underlying mechanisms are not well understood. We conducted a four-year removal experiment to test for population-level mechanisms (i.e., changes in recruitment, survival, emigration, and immigration) promoting invasion success of brook Trout and causing decline of native Colorado River cutthroat Trout (O. c. pleuriticus). We chose 700–1200 m segments of four small mountain streams where brook Trout had recently invaded cutthroat Trout populations, two each at mid elevation (2500–2700 m) and high elevation (3150–3250 m), and annually removed brook Trout from two streams (treatments), but not the other two (controls). We used depletion electrofishing, two-way fish weirs, and mark–recapture methods to estimate abundance, movement, and survival of Trout. At mid elevation, age-0 and age-1 cutthroat Trout survived at 13 times and two times ...
upstream movement by nonnative brook Trout salvelinus fontinalis promotes invasion of native cutthroat Trout oncorhynchus clarki habitatCanadian Journal of Fisheries and Aquatic Sciences, 2003Co-Authors: Douglas P. Peterson, Kurt D. FauschAbstract:
To understand how immigration and emigration influence the processes by which invading nonnative brook Trout (Salvelinus fontinalis) displace native cutthroat Trout (Oncorhynchus clarki), we studied Trout movement in long segments of three mountain streams in Colorado during 1999–2001. Over 3500 Trout were captured and marked at weirs and during electrofishing, both within and downstream of stream segments. Nearly 80% of brook Trout captured at weirs were moving upstream, whereas almost 65% of cutthroat Trout were moving downstream. Brook Trout movements peaked in early summer and again in fall. Brook Trout immigration rates from downstream source populations were high, and in one stream, invaders repopulated a segment where they were removed within 8 months. Immigrant brook Trout were typically mature adults in similar body condition to the general population. Brook Trout immigrated from a range of distances, with local movement within 250 m more frequently detected, but fish also moved from many distanc...
Ecology of Freshwater Fish, 1992Co-Authors: Stephen C Riley, Kurt D. Fausch, Charles GowanAbstract:
We studied the movement of brook Trout (Salvelinus fontinalis) in four small streams in northern Colorado using mark-recapture methods and weirs. The recapture rates of marked adult Trout were low for all streams, and large numbers of unmarked adult Trout, apparently immigrants, were found each year. Significantly more Trout, immigrated into sections that were experimentally modified by installing low log dams, which increased depth, pool volume and the amount of overhead cover. The number of immigrant and resident Trout was significantly related to the amount of cover in the sections. Resident Trout were larger than immigrants in all streams in the last year of sampling. Most mobile brook Trout moved upstream during summer on the two streams where weirs were operated, and upstream migrants were significantly larger than downstream migrants on both streams. We suggest that a high degree of movement may be an adaptive response by brook Trout to the heterogeneous nature of small mountain streams.
Michael Moller Hansen - One of the best experts on this subject based on the ideXlab platform.
stocking impact and migration pattern in an anadromous brown Trout salmo trutta complex where have all the stocked spawning sea Trout goneMolecular Ecology, 2004Co-Authors: Daniel E Ruzzante, Dorte Meldrup, Michael Moller Hansen, Kaare M EbertAbstract:
We examined polymorphism at seven microsatellite loci among sea Trout (Salmo trutta) (n = 846) collected from three areas in the Limfjord (Denmark). We then assessed their potential population source by comparing, using a mixed stock analysis (MSA) Bayesian framework, their genetic composition to that of brown Trout collected from 32 tributaries pooled into nine geographical regions (n = 3801) and two hatcheries (n = 222) used for stocking. For each of the three regional sea Trout groups (western, central and eastern Limfjord, n = 91, n = 426, n = 329, respectively), MSA was conducted with (i) all individuals in the group, (ii) with the subset of spawning sea Trout only and (iii) with the subset of foraging, nonspawning individuals only, a subset that consisted primarily of sea Trout caught during their first year at sea. For all three regional sea Trout groups, a higher proportion of individuals (regardless of whether they were foraging or spawning) appear to have originated from the rivers that drain locally, than from the rivers that drain in other parts of the Limfjord. This suggests (1) that sea Trout, at least during their first year at sea, undertake limited migrations within the Limfjord system and (2) that sea Trout on their spawning run were caught close to their natal rivers. The proportion of sea Trout of hatchery origin varied widely among all three Limfjord areas and broadly reflected regional stocking histories, with high proportions of sea Trout of domestic origin in the east (39.3%), where stocking with domestic Trout was practised intensely at the time of sampling, and in the west (57.2%), where a programme of coastal stocking of post smolts took place over several years in the early 1990s. In contrast, in the central Limfjord, where stocking with domestic Trout was largely abandoned in the early 1990s, the proportion of sea Trout of domestic origin was only 8.5%. Interestingly, for all three regional sea Trout groups, virtually no sea Trout of hatchery origin were found among the spawning individuals, which were on average larger than the nonspawning sea Trout. These results suggest that stocked domestic brown Trout that become anadromous experience high mortality at sea and are therefore largely absent among the larger, spawning individuals. We conclude that sea Trout of domestic origin exhibit much reduced ability to reproduce and are unlikely to contribute significantly to the local gene pool largely because of a relatively high mortality at sea before the onset of maturity.
estimating the long term effects of stocking domesticated Trout into wild brown Trout salmo trutta populations an approach using microsatellite dna analysis of historical and contemporary samplesMolecular Ecology, 2002Co-Authors: Michael Moller HansenAbstract:
Indigenous salmonid fish gene pools are affected by domesticated conspecifics, derived from aquaculture escapes and deliberate releases. Variability was examined at nine microsatellite loci in order to assess the long-term impact of stocking domesticated Trout in two brown Trout populations. The study was based on analysis of two historical samples (1945-56), represented by old scale collections, and seven contemporary samples (1986-2000). In one population historical and contemporary samples were remarkably genetically similar despite more than a decade of intense stocking. Estimation of admixture proportions showed a small genetic contribution from domesticated Trout (approximately 6%), and individual admixture analysis demonstrated a majority of nonadmixed individuals. The expected genetic contribution by domesticated Trout was 64%, assessed from the number of stocked Trout and assuming equal survival and reproductive performance of wild and domesticated Trout. This demonstrates poor performance and low fitness of domesticated Trout in the wild. In another population there was a strong genetic contribution from domesticated Trout (between 57% and 88% in different samples), both in samples from a broodstock thought to represent the indigenous population and in a sample of wild spawners. Survival of domesticated Trout and admixture with indigenous fish in the broodstock and subsequent stocking into the river, combined with a low population size of native Trout relative to the number of stocked Trout, could explain the observed introgression. Few nonadmixed individuals remained in the introgressed population, and I discuss how individual admixture analysis can be used to identify and conserve nonintrogressed remains of the population.
microsatellite and mitochondrial dna polymorphism reveals life history dependent interbreeding between hatchery and wild brown Trout salmo trutta lMolecular Ecology, 2000Co-Authors: Michael Moller Hansen, Daniel E Ruzzante, Einar Eg Nielsen, Karenlise Dons MensbergAbstract:
The effects of stocking hatchery Trout into wild populations were studied in a Danish river, using microsatellite and mitochondrial DNA (mtDNA) markers. Baseline samples were taken from hatchery Trout and wild Trout assumed to be unaffected by previous stocking. Also, samples were taken from resident and sea Trout from a stocked section of the river. Genetic differentiation between the hatchery strain and the local wild population was modest (microsatellite FST = 0.06). Using assignment tests, more than 90% of individuals from the baseline samples were classified correctly. Assignment tests involving samples from the stocked river section suggested that the contribution by hatchery Trout was low among sea Trout (< 7%), but high (46%) among resident Trout. Hybrid index analysis and a high percentage of mtDNA haplotypes specific to indigenous Trout observed among resident Trout that were assigned to the hatchery strain suggested that interbreeding took place between hatchery and wild Trout. The latter result also indicated that male hatchery Trout contributed more to interbreeding than females. We suggest that stronger selection acts against stocked hatchery Trout that become anadromous compared to hatchery Trout that become resident. As most resident Trout are males this could also explain why gene flow from hatchery to wild Trout appeared to be male biased. The results show that even despite modest differentiation at neutral loci domesticated Trout may still perform worse than local populations and it is important to be aware of differential survival and reproductive success both between life-history types and between sexes.