Presence Of Rainbow Trout Research Articles

Evaluating the effects of selective passage of migratory Westslope Cutthroat Trout on nonnative admixture

AbstractObjectiveHybridization with nonnative Rainbow Trout Oncorhynchus mykiss is a primary threat to the persistence of Westslope Cutthroat Trout O. clarkii lewisi. Managers concerned with conserving migratory populations of Westslope Cutthroat Trout in the presence of Rainbow Trout often face the predicament of tolerating the spread of hybridization, intentionally isolating Westslope Cutthroat Trout populations, or suppressing Rainbow Trout source populations.MethodsSelective passage of migratory Westslope Cutthroat Trout above existing barriers is a management approach with the potential to limit hybridization, while minimizing the population impacts of barriers in populations with preexisting low levels of hybridization. We took a before‐after–control‐impact approach to evaluate a phenotype‐based selective passage management program for migratory Westslope Cutthroat Trout in the Jocko River, Montana.ResultOf the 364 genotyped individuals selectively passed upstream of a barrier, 82% had a proportion of Rainbow Trout admixture < 0.01 and 98% had < 0.10. Over 14 years (2005–2019), there was no significant increase in hybridization at sites (n = 12) upstream of the barrier, but metrics increased within some of our control (no barrier, n = 8) sites. This increase was greatest at a site just downstream from the barrier, suggesting that blocked fish might have spawned opportunistically in this adjacent tributary.ConclusionWe demonstrate that phenotypic traits were useful in implementing a selective Westslope Cutthroat Trout passage program that allowed managers to promote the migratory life history without increasing nonnative admixture in this watershed.

Aquatic macroinvertebrates from littoral vegetated lakes in arid Patagonia: The influence of fish introduction on community structure

Abstract Wetlands in arid regions are characterized by their great heterogeneity, often including endemic species that contribute to regional aquatic biodiversity. In the Patagonian steppe, most lakes are naturally fishless and sustain a rich aquatic biodiversity, including endemics; however, many of these lakes have been stocked with Oncorhynchus mykiss (rainbow trout) during recent decades. The introduction of predatory fish into aquatic ecosystems naturally devoid of these organisms can produce profound alterations in the structure of the original communities and in the configuration of their biotic assemblages. Aquatic invertebrates play important roles in both the structure and functioning of freshwater ecosystems, including their contribution to global biodiversity and their cascading effects across ecosystem boundaries. The aim of this study was to assess the effect of introduced non‐native fish on the pleustonic macroinvertebrate assemblage. Samples were taken from 10 shallow Patagonian lakes (five fishless and five stocked with fish) in two consecutive warm periods. Lakes with fish had higher conductivity and phosphate values. Higher inter‐annual differences were also observed in lakes with fish for phytoplanktonic chlorophyll a, nitrate, phosphate, conductivity, and water temperature. The community structure (relative abundance of different taxa, species composition, and diversity index) was affected by the presence of rainbow trout, with the differences mainly driven by the relative abundance of Ostracoda, Hyalella, Chironomidae, and Haliplus species. This approach can be used to assess the required conservation actions in shallow Patagonian steppe lakes, which have been listed as priority areas for waterbird conservation. Specifically, this study provides a baseline for monitoring future trends of the macroinvertebrate communities and for evaluating conservation and management efforts over time.

The presence of rainbow trout reduces drift of aquatic insects in Yungas streams (Tucumán, Argentina)

The drift or transport of individuals downstream is an important phenomenon of rivers and streams, since most aquatic organisms participate in it at some period of their life cycle. This work describes the assemblage of macroinvertebrate drift from ten sites in eight mountain streams of Tucumán, and evaluates the effect of the presence of rainbow trout (Oncorhynchus mykiss Walbaum), an exotic fish and visual predator, on this fraction of the community. Thirty-one (31) families of drifting aquatic invertebrates were identified, mainly immature insects and to a lesser extent water mites (Acari: Hydrachnidia), oligochaetes (Annelida: Oligochaeta) and nematodes (Nematoda). The richness and diversity of the sites with trout did not differ from the others, except when comparing lower and upper reaches of a same stream. Samples from rivers without trout or with low density of trout did not show significant changes in drift density of macroinvertebrates. In contrast, in rivers with high trout densities, a notable decrease in insect taxa was observed (those with large sized individuals): Baetidae (Ephemeroptera), Gripopterygidae (Plecoptera) and Leptoceridae (Trichoptera). On the contrary, the density of small Diptera, water mites, oligochets and nematodes increased in trout-streams

Competitive effects between rainbow trout and Atlantic salmon in natural and artificial streams

AbstractCompetition with non‐native species may impede the restoration of native species, but differences in competitive abilities among intraspecific native populations may make some populations more suitable for reintroduction than others. Here, juvenile Atlantic salmon (Salmo salar) from two allopatric populations (LaHave and Sebago) being used for reintroduction into Lake Ontario were placed into two natural stream sites differing in the presence of ecologically similar rainbow trout (Oncorhynchus mykiss). We assessed the effects of competition in the natural streams on fitness‐related traits and habitat use of the Atlantic salmon. We then compared these effects to those observed in artificial streams from a previous study. Atlantic salmon in natural streams had reduced fitness‐related traits that were associated with suboptimal microhabitats in the presence of rainbow trout, but utilised optimal microhabitats in their absence. In the presence of rainbow trout, the two Atlantic salmon populations exhibited comparable recapture proportions to each other, but the individuals from the Sebago population had better performance (body size and condition) than those from the LaHave population. Responses of both Atlantic salmon populations to competition with rainbow trout were generally similar in both direction and magnitude when compared to results from the artificial stream study. The combined results suggest that native species restoration efforts should be focused on candidate populations that are ecologically suitable to reintroduction environments, as well as on suitable habitats that do not contain exotic competitors. Moreover, this study highlights the value of controlled experiments in artificial environments for predicting fitness‐related performance in natural environments.

Invasive rainbow trout affect habitat use, feeding efficiency, and spatial organization of warpaint shiners

Rainbow trout have been introduced to six of the seven continents and currently are widely stocked for sport fishing. Despite their broad distribution, outside of New Zealand, little is known about the effects of rainbow trout on native species, especially fishes. We conducted experiments in an artificial stream to assess hypotheses that stocked rainbow trout significantly affected: (1) mesohabitat use, (2) foraging success, (3) social behavior, and (4) spatial organization of warpaint shiners (Luxilus coccogenis) a common native minnow found in southern Appalachian streams, with similar patterns of microhabitat use to rainbow trout. We replicated experiments at high and low natural densities (two and five warpaint shiners) and spring/fall (12 °C) and summer (17 °C) temperatures. Treatments included: (1) a control (five warpaint shiners), (2) trout (five warpaint shiners and one rainbow trout), (3) large fish control (five warpaint shiners and one river chub) and (4) density control (six warpaint shiners). The presence of rainbow trout produced a shift by warpaint shiners from pool mesohabitats to shallower, higher velocity habitats with more variable substrata, as well as reduced prey capture success, feeding efficiency, and distance from the front of the tank (i.e., warpaint shiners moved closer to food release points), and increased the distance to the additional fish (i.e., avoidance of the rainbow trout). Negative effects on foraging behaviors were stronger in 12 °C treatments. In a realistic stream flume the presence of rainbow trout produced effects that likely influenced individual fitness of warpaint shiners. The potential effects of stocking rainbow trout on native non-game fishes, such as warpaint shiners should be assessed when implementing or evaluating stocking programs.

Impacts of Exotic Rainbow Trout on Habitat Use by Native Juvenile Salmonid Species at an Early Invasive Stage

AbstractThe detrimental impact of introduced Rainbow Trout Oncorhynchus mykiss on native communities has been well documented around the world. Previous studies have focused on streams where the invasion has been successful and the species is fully established. In eastern Quebec, the invasion of Rainbow Trout is an ongoing process and, for now, there are few established populations. The presence of two native salmonids in these rivers, Atlantic Salmon Salmo salar and Brook Trout Salvelinus fontinalis, implies a risk of competition for habitat, despite the relatively low density of the Rainbow Trout populations, as all three species are known to use similar resources. In order to evaluate the strength of the interaction between the invading fish and the native species, we sampled nine rivers (five with Rainbow Trout and four free of Rainbow Trout) and characterized the habitat used by the three salmonids at the juvenile stage. River‐scale analysis revealed that in invaded rivers, Rainbow Trout were associated with habitats characterized by closer proximity to the shoreline and by increasing shoreline cover. Estimates of habitat niche overlap integrating depth, water velocity, and substrate size revealed that niche overlap between Brook Trout and Atlantic Salmon significantly increased in the presence of Rainbow Trout. Furthermore, the two indigenous species preferred full cover in the absence of Rainbow Trout but in the presence of Rainbow Trout, which also preferred full cover, the indigenous species moved to more open habitats. Rainbow Trout showed a high growth rate, despite a size disadvantage at the beginning of the growing season, as compared with Atlantic Salmon and Brook Trout. It thus appears that even at an early stage of invasion, when its density is still low, Rainbow Trout significantly impact native salmonids.

Primer registro de Saprolegnia sp. en una población de anfibios en Colombia.

<p><strong> </strong></p> <p><strong>Objective: </strong><strong>Most </strong>research related to the decline of amphibians has been focused on the detection of the pathogenic fungus <em>Batrachochytrium dendrobatidis</em>. This fungus is the main pathogen detected around the world. However, research has shown the presence of another fungus, <em>Saprolegnia ferax</em>, as a cause of mortality in amphibians in North America. Our study suggests a possible interspecific transmission caused by the presence of rainbow trout; thus, amphibian declines may not be attributable only to the presence of a single pathogen, but to other organisms and factors. <strong>Materials and methods: </strong>Our study revealed the presence of <em>Saprolegnia</em> sp. in the Andean frog <em>Atelopus mittermeieri</em> using the imprinting technique with lactophenol blue staining, which allowed the typical structures of this fungus to be observed. <strong>Results:</strong> The importance of this discovery is the presence of two pathogenic fungi, <em>B. dendrobatidis </em>and <em>Saprolegnia</em>, which affecting simultaneously a population of amphibians. This finding brings attention to the eventual presence of other microorganisms that might be involved individually or collectively in the decline of amphibian species. <strong>Conclusions:</strong> This record suggests a possible transmission between rainbow trout (<em>Oncorhynchus mykiss</em>), an introduced species in the highlands of Colombia, which shares the same habitats with different species of amphibians in the Sanctuary of Flora and Fauna Guanentá in the upper river Fonce in the mid Cordillera Oriental of Colombia.</p> <p><strong>Key words: </strong>decline, Amphibians,<em> Saprolegnia</em>, Fishes, <em>Atelopus</em>, Colombia.</p> <p> </p> <p><strong> </strong></p><br />

Abiotic variables accounting for presence of the exotic rainbow trout (Oncorhynchus mykiss) in Eastern Quebec Rivers

Key-words: invasion success, abiotic filter, geomorphological variables, climatic variables, logistic regression modelling Rainbow trout is an exotic fish species that has been introduced in Quebec (Canada) since 1893–1894. Despite spatially-restricted stocking for recreational fishing, the species has spread throughout the Saint Lawrence River. In this study, the relationship between rainbow trout occurrence (presence or absence) and abiotic variables (river geomorphology and climate) was examined for 91 coastal rivers throughout Eastern Quebec in order to determine which variables promote or impede the ongoing invasion process. Results revealed that rainbow trout presence in Eastern Quebec was primarily determined by geomorphological parameters. The invader’s presence was strongly related to the presence of tributaries (especially larger ones). To a lesser extent, the presence of rainbow trout was positively related to warm spring and summer temperatures and negatively related to the peak flood date occurring during the egg deposition period (May). This study proposes a parsimonious modelling approach to identify which environmental parameters favour the spreading of an invader, even when a limited dataset is available due to the incomplete invasion process.

Temperature-dependent Effects of Rainbow Trout on Growth of Atlantic Salmon Parr

Temperature may influence interactions between species by regulating energy balances of individuals. We conducted a laboratory study to determine whether temperature influenced the effects exerted by large rainbow trout on the growth of Atlantic salmon parr. Bioenergetic models were used to predict maintenance rations so that food resources were limiting over a range of temperatures; equal biomasses of rainbow trout were substituted for Atlantic salmon to evaluate the relative effect of interspecific interactions on Atlantic salmon growth. In the presence of rainbow trout, salmon growth increased as temperatures increased from 15°C to 25°C; no such temperature effect occurred for salmon maintained alone. Growth differences between salmon maintained with and without trout were highly significant at 25°C but not at 15°C. We conclude that the presence of trout depressed salmon growth at 15°C but not at higher temperatures, most likely a result of differences in thermal optima between these two species. Field data show that the proportion of stocked Atlantic salmon to wild rainbow trout coexisting in natural streams is a function of mean summer temperature. As stream temperatures increased, Atlantic salmon became increasingly favored over rainbow trout, but with a concomitant decrease in total salmonine biomass. We suggest that Atlantic salmon restoration programs focus more attention on relatively warm streams in watersheds where interactions with naturalized rainbow trout may occur.

Characteristics of Smallmouth Bass (Micropterus dolomieu) and Shadow Bass (Ambloplites ariommus) Populations in an Ozark Stream before and after Rainbow Trout Introduction

ABSTRACT We evaluated characteristics of smallmouth bass (Micropterus dolomieu) and shadow bass (Ambloplites ariommus) populations in a small, northeastern Oklahoma Ozark stream from February 2000 to March 2003 to evaluate potential effects of rainbow trout (Oncorhynchus mykiss) introduction on these species. We experimentally stocked rainbow trout into the stream from November 2000 to March 2001 and November 2001 to March 2002. Mark-recapture and telemetry data showed patterns of limited movement among pool habitats by both bass species, and presence of rainbow trout in Brush Creek did not appear to influence movement patterns. We documented recruitment by smallmouth and shadow bass during our study, indicating that rainbow trout introduction did not inhibit spawning. Mean relative weight (W,r) of smallmouth bass ranged from 77—80, and we did not detect differences in relative weight among pre-stocking, the first year of stocking, and the second year of stocking. It appears that important population characteristics of these two species in our study stream were not negatively impacted by rainbow trout introduction.

No Net Loss of Brook Trout Distribution in Areas of Sympatry with Rainbow Trout in Tennessee Streams

Lowest distributional elevations for brook trout Salvelinus fontinalis in 25 streams in east Tennessee were determined during 1991–1995 to evaluate changes related to encroachment and possible replacement by rainbow trout Oncorhynchus mykiss since surveys conducted during 1978–1984. No efforts to remove rainbow trout or enhance brook trout populations were made in these streams during the 7–16-year intervals between surveys. Compared with the earlier surveys, brook trout distributions receded (lower elevation increased) in nine streams (36%), advanced (lower elevation decreased) in eight streams (32%), and did not change in eight streams (32%). The average total change in stream length occupied by brook trout was a 109-m downstream increase (SE = 82) with a mean annual increase of 8 m (SE = 6). Neither average total change nor annual change was significant (P > 0.19). Additionally, the highest elevations at which rainbow trout were present (determined in 10 streams) increased in four streams but decreased in six. The average total change in stream length occupied by rainbow trout was a 158-m decrease in elevation (SE = 151) with a mean annual change of −14 m (SE = 13). Neither average total change nor mean annual change was significant (P > 0.30). We concluded that rainbow trout were not affecting the downstream limit of most brook trout populations where the two species occurred sympatrically in Tennessee. Further, after examining published data from Great Smoky Mountains National Park, we found no evidence that the downstream limits of brook trout distribution in most streams were affected by the presence of rainbow trout between the 1950s and 1970s. These data support an emerging theory that the distributional limits of brook trout and rainbow trout in sympatry in the southern Appalachian Mountains will ebb and flow upstream and downstream over time.

The effects of rainbow trout (Oncorhynchus mykiss) on the use of spatial resources and behavior of rosyside dace (Clinostomus funduloides)

Rainbow trout (Oncorhynchus mykiss) and rosyside dace (Clinostomusfitn- duloides) exhibit substantial overlap in microhabitat use in Coweeta Creek, North Carolina, USA. We conducted a replicated experiment in an artificial stream to assess the effects of both the presence of rainbow trout and dace density on: 1) microhabitat use, 2) agonistic behavior, 3) social behavior and 4) feeding rates of dace. Our results demonstrated that microhabitat use of dace was highly variable both among competi- tion treatments within a replicate and for the same competition treatment among repli- cates. Moreover, the pattern of the differences between competition treatments was not consistent among replicates. As a result, we detected a significant effect of experi- mental replicate on dace microhabitat use but no significant competition effect. Trout had little effect on the behavior of dace and intraspecific aggression was much more common than interspecific aggression. There were strong inter-individual differences in the agonistic behavior of dace, and 94 of the IT7 aggressive displacements ob- served were initiated by one or two highly aggressive individuals per replicate. We detected few significant acclimation or time of day effects. The significant differences in microhabitat use and behavior observed within replicates appeared to be a conse- quence of differential initial settlement patterns of dace or the presence of one or two highly aggressive dace in treatments. Hence, we do not believe that interspecific com- petition with rainbow trout has a strong effect on microhabitat use by dace in Co- weeta Creek.

Notes: Effects of Rainbow Trout Predation on Little Colorado Spinedace

Abstract We tested the effect of predation by rainbow trout Oncorhynchus mykiss on the behavior and spatial distribution of Little Colorado spinedace Lepidomeda vittata, a native cyprinid that occurs in disjunct populations in northern Arizona. Field experiments demonstrated high predation on Little Colorado spinedace even in the presence of natural refuges and abundant macroinvertebrate prey. Little Colorado spinedace showed almost no predator avoidance in the presence of rainbow trout, which implies limited interaction with large nonnative predators through evolutionary time. Results suggest that rainbow trout may have a significant influence on the habitat use, behavior, and geographic distribution of Little Colorado spinedace, and may be responsible, in part, for the disjunct geographic distribution of this threatened native fish species.

Microhabitat Selection by Brook and Rainbow Trout in a Southern Appalachian Stream

Abstract The decreased range of native brook trout Salvelinus fontinalis in the Great Smoky Mountains National Park has been attributed to competition with introduced rainbow trout Oncorhynchus mykiss. To determine whether brook trout were displaced from preferred sites in the presence of rainbow trout, we made underwater observations of microhabitat use to characterize positions of individual fishes in a section of Palmer Creek, North Carolina, where both species occur. We then reduced rainbow trout numbers by about 80% by electrofishing and repeated our underwater observations on the remaining brook trout to determine whether the species underwent changes in microhabitat use. We found differences in characteristics of focal points selected by the two species. Focal points of age-0 brook trout were similar to those of rainbow trout for distance to overhead cover. After rainbow trout were reduced, age-0 brook trout shifted to positions significantly farther from overhead cover. Brook trout age 1 or older ...

Distribution of the Stonefly Nymph Paragnetina media (Plecoptera:Perlidae): Influence of Prey, Predators, Current Speed, and Substrate Composition

Effects of prey distribution, presence of a predator, current speed, and substrate composition on distribution of the predaceous stonefly nymph Paragnetina media (Walker) were examined in a large laboratory stream. Distribution of prey (Hydropsyche sparna, H. bronta) did not affect distribution of well-fed or non-fed (48 h) nymphs. However, P. media distribution was significantly influenced by independent and interactive effects of current speed (0.33–0.41 m∙s−1) and substrate composition (53.0–110.0 mm in diameter). In the presence of rainbow trout (Salmo gairdneri), P. media selected more specifically for larger substrate on which risk of predation was less than on smaller size classes. Lighting condition had no effect on substrate selection. Laboratory findings were consistent with distribution of P. media observed in the Credit River, Ontario, during midsummer, late fall, and early spring.

Efficacy of specific antibody against agglutinating Aeromonas salmonicida strains on infectivity and vaccination with inactivated protease

AbstractEfficacy of specific antibody on serum resistance and adhesion was investigated using a pathogenic strain of Aeromonas salmonicida A‐7301 (which was autoagglutinative, haemagglutinative and protease production positive), a protease‐deficient, non‐pathogenic mutant NTG‐1 induced from A‐7301 (autoagglutinative and haemagglutinative), and a non‐pathogenic strain GH‐7501 (non‐agglutinative, non‐haemagglutinative and protease positive). A‐7301 could grow and produce protease extracellularly in the presence of rainbow trout anti‐A‐7301 serum, resulting in a considerable reduction of the antibody titre. NTG‐1 similarly grew, but the titre scarcely decreased. GH‐7501 could not survive in this medium. A‐7301 and NTG‐1 possessed a high capacity to adhere to the surface of fish monolayer cell cultures, whereas GH‐7501 lacked the capacity. The capacity for adhesion was not inhibited by the antibody. Although live NTG‐1 cells were ineffective as a live vaccine, sockeye salmon receiving protease fraction (obtained from extracellular products of A‐7301 by DEAE‐cellulose column chromatography) inactivated with normal serum, suffered only a low mortality when challenged with A‐7301. Thus, although the antibody specific to autoagglutinating cells showed no effects on serum resistance and adhesion, which are involved in the infectivity of this pathogen, the possibility of protease as an effective protective antigen was demonstrated.