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The extent and availability of suitable habitat is a fundamental factor limiting the abundance of natural populations. In many stream ecosystems, habitat degradation has reduced habitat quality by removing critical habitat features such as pools. We hypothesized that adding pool habitat to streams would increase habitat quality for salmonid fish and improve population productivity. In this study, we used instream structures to add pool habitat to four headwater streams and estimated changes to habitat quality for cutthroat trout (Oncorhynchus clarkii) across two seasons using a bioenergetic model. Fish populations were monitored over 5 years to evaluate how treatments influenced fish abundance and growth. We found that the proportion of suitable habitat was higher in treatment sections and in artificially created pool habitats. Abundance of young- of-the- year trout was higher in treatment reaches in comparison to controls and the growth of trout across all size classes sampled was higher in treatment reaches. Our results indicate that increasing pool habitat improves habitat quality resulting in increased densities of cutthroat trout and higher fish growth. Key words: bioenergetics, cutthroat trout, growth, habitat quality, instream structures, Introduction The availability of suitable habitat is a primary factor limiting the distribution and abundance of natural populations (Travis and Dytham 1999; Holbrook et al. 2000; Bjprneraas et al. 2012). [...]

Objective: Hybridization between native and nonnative fishes represents a global threat to biodiversity. Understanding how hybridization changes in response to management actions is critical to evaluating the efficacy of conservation efforts. Methods: We quantified changes in levels of hybridization between Yellowstone Cutthroat Trout Oncorhynchus virginalis bouvieri and Rainbow Trout Oncorhynchus mykiss in the South Fork Snake River watershed, where a multipronged approach has been implemented to protect the evolutionary distinctiveness of one of the last remaining large‐river populations of Yellowstone Cutthroat Trout. Result: Over a 20‐year period, we observed an increase in the number of sample reaches without hybrids in the South Fork Snake River watershed; however, contrasting patterns were noted in main‐stem and tributary reaches. Through time, hybrid abundance increased at main‐stem reaches of the South Fork Snake River below Palisades Dam but decreased in tributaries. Efforts to reduce hybridization in spawning tributaries, including both suppression and selective passage weirs, were effective at preventing the expansion of hybridization in resident and migratory populations. Multimodel inference was used to understand factors affecting levels of hybridization, and year, sampling reach, and the interaction thereof was identified as the best‐fit model but explained only a small percentage of the overall variation, suggesting that other factors not captured in our model were driving patterns in hybridization. Conclusion: Changes in hybridization in the South Fork Snake River watershed are likely the result of multiple processes, namely management actions to reduce Rainbow Trout and hybrids in tributaries, as well as demographic changes in Rainbow Trout in the main‐stem river below Palisades Dam. Our results suggest that Yellowstone Cutthroat Trout populations in the South Fork Snake River watershed have not experienced widespread interspecific hybridization with Rainbow Trout but that proactive management will be necessary to ensure long‐term conservation. Impact statementOver the past 20 years, hybridization between introduced Rainbow Trout and native Yellowstone Cutthroat Trout in the South Fork Snake River watershed has declined in spawning tributaries because of management actions but increased in select main‐stem river reaches because of Rainbow Trout population growth. [ABSTRACT FROM AUTHOR]

The cutthroat trout (Oncorhynchus clarkii (Richardson, 1836)) is one of the most widely distributed species of freshwater fish in western North America. Occupying a diverse range of habitats, they exhibit significant phenotypic variability that is often recognized by intraspecific taxonomy. Recent molecular phylogenies have described phylogenetic diversification across cutthroat trout populations, but no study has provided a range-wide morphological comparison of taxonomic divisions. In this study, we used linear- and geometric-based morphometrics to determine if phylogenetic and subspecies divisions correspond to morphological variation in cutthroat trout, using replicate populations from throughout the geographic range of the species. Our data indicate significant morphological divergence of intraspecific categories in some, but not all, cutthroat trout subspecies. We also compare morphological distance measures with distance measures of mtDNA sequence divergence. DNA sequence divergence was positively correlated with morphological distance measures, indicating that morphologically more similar subspecies have lower sequence divergence in comparison to morphologically distant subspecies. Given these results, integrating both approaches to describing intraspecific variation may be necessary for developing a comprehensive conservation plan in wide-ranging species. Key words: phenotype, diversity, morphology, native distribution, intraspecific variation, cutthroat trout, Oncorhynchus clarkii. La truite fardée (Oncorhynchus clarkii (Richardson, 1836)) est une des espèces de poissons d'eau douce les plus largement réparties dans l'ouest de l'Amérique du Nord. L'espèce, qui occupe une grande variété d'habitats, présente une variabilité phénotypique considérable souvent soulignée par une taxonomie intraspécifique. Des phylogénies moléculaires récentes ont décrit une diversification phylogénétique parmi les populations de truites fardées, mais aucune étude n'aprésenté une comparaison morphologique des divisions taxonomiques pour l'ensemble de l'aire de répartition. Nous avons utilisé des paramètres morphométriques linéaires et basés sur la géométrie pour déterminer si des divisions phylogénétiques et de sous-espèces correspondent à des variations morphologiques parmi les truites fardées, en utilisant des populations répétées provenant de l'ensemble de l'aire de répartition géographique de l'espèce. Nos données indiquent une divergence morphologique significative de catégories intraspécifiques au sein de certaines sous-espèces de truite fardée, mais pas toutes. Nous comparons également des mesures de distance morphologique à des mesures de distance de la divergence de séquences d'ADNmt. La divergence de séquences d'ADN est positivement corrélée aux mesures de distance morphologique, ce qui indique que des sous-espèces morphologiquement semblables présentent une moins grande divergence séquentielle que des sous-espèces morphologiquement distantes. À la lumière de ces résultats, l'intégration des deux approches de description des variations intraspécifiques pourrait être nécessaire à l'élaboration d'un plan de conservation exhaustif pour les espèces à grande aire de répartition. [Traduit par la Rédaction] Mots-clés: phénotype, diversité, morphologie, aire de répartition indigène, variation intraspécifique, truite fardée, Oncorhynchus clarkii., Introduction Widely distributed species often exhibit significant phenotypic variation across their geographic range (Mayr 1963). Intraspecific variability can represent substantial levels of diversity, allowing different populations to occupy a variety [...]

Management and conservation of freshwater habitat requires fine spatial resolution and watershed-scale and lifestage- specific methods due to complex linkages among land, climate, water uses, and aquatic organism necessities. In this study, we present a valley-scale microhabitat resolution, process-based bioenergetics approach that combines high-resolution topobathymetric LiDAR survey with two-dimensional hydrodynamic and bioenergetics modeling. We applied the model to investigate the role of lateral habitat, stream morphological complexity, water use, and temperature regimes on aquatic habitat quality distribution of juvenile Chinook salmon (Oncorhynchus tshawytscha) within the Lemhi River (eastern Idaho, USA). Modeling results showed two key aspects: (i) a reduction in diverted flows is not sufficient to improve habitat quality potentially because of a legacy of morphological simplification (directly due to straightening and wood removal and indirectly due to low in- channel flows) and (ii) morphological complexity and connectivity with side channels and margin areas, which are key and vital elements to support suitable habitats that meet or exceed energetic needs to sustain or promote growth of individuals and populations. La gestion et la conservation des habitats d'eau douce necessitent des methodes de haute resolution spatiale, a l'echelle du bassin versant et pouvant cibler des etapes precises du cycle biologique, en raison des liens complexes qui existent entre le paysage, le climat, les utilisations de l'eau et les exigences des organismes aquatiques. Nous presentons une approche bioenergetique basee sur les processus appliquee a l'ensemble d'une vallee et de resolution a l'echelle du microhabitat, qui combine le releve topobathymetrique par lidar de haute resolution a la modelisation bioenergetique et hydrodynamique en deux dimensions. Nous avons utilise le modele pour examiner le role des habitats lateraux, de la complexite morphologique du cours d'eau, de l'utilisation de l'eau et des regimes thermiques sur la repartition de la qualite de l'habitat des saumons chinooks (Oncorhynchus tshawytscha) juveniles dans la riviere Lemhi (est de l'Idaho, Etats-Unis). Les resultats de la modelisation font ressortir deux elements cles, a savoir (i) qu'une reduction des debits detournes ne suffit pas pour ameliorer la qualite de l'habitat, possiblement en raison de la simplification morphologique persistante (decoulant directement de la rectilinearisation et du retrait de bois et indirectement des faibles debits en chenal) et (ii) que la complexite morphologique et la connectivite avec les chenaux lateraux et les zones marginales sont des elements cles et d'importance vitale pour soutenir des habitats convenables qui repondent aux besoins energetiques necessaires a la croissance d'individus et de populations. [Traduit par la Redaction], Introduction As global human population rise continues, pressure on freshwater resources increases (Davis et al. 2015). An ever-changing climate scenario, coupled with human population growth and its impacts, has begun [...]

Nutrient supplementation in oligotrophic streams is proposed as a means of mitigating losses of marine-derived subsidies from declining or extirpated populations of anadromous fishes. One of the central predictions of nutrient addition is an increased production of fish through bottom-up increases in invertebrate abundance. Such changes in food availability may increase growth and production rates for stream fishes by increasing habitat quality. In this study we apply bioenergetic calculations to estimate changes to habitat quality based on predicted increases in net energy intake. We compared invertebrate drift abundance and estimated changes in energy availability in streams treated with salmon carcass analog versus untreated controls. Our results revealed a two- to threefold increase in invertebrate drift abundance following the addition of salmon carcass analog; however, this effect appeared to be short-term. Measures of the energetic profitability of stream habitat for salmonid fishes revealed small, yet significant, increases in net energy availability in streams that received analog additions, but only after controlling for differences in physical habitat features such as temperature and stream flow. L'ajout de nutriments dans les cours d'eau oligotrophes est propose comme moyen pour attenuer les pertes d'apports allochtones d'origine marine decoulant de la baisse ou de la disparition locale de populations de poissons anadromes. Une des consequences predites centrales de l'ajout de nutriments est une production accrue de poissons decoulant d'augmentations ascendantes de l'abondance des invertebres. De telles modifications de la disponibilite de nourriture pourraient accroitre les taux de croissance et de production pour les poissons de cours d'eau en rehaussant la qualite des habitats. Nous utilisons des calculs bioenergetiques pour estimer les modifications de la qualite de l'habitat a la lumiere des augmentations predites de l'apport energetique net. Nous comparons l'abondance des invertebres a la derive et estimons les variations de la disponibilite d'energie dans des cours d'eau traites avec un analogue de carcasses de saumon et des cours d'eau temoins non traites. Les resultats revelent des abondances d'invertebres a la derive de deux a trois fois plus grandes apres l'ajout d'analogue de carcasses de saumon; cet effet semble toutefois de courte duree. Les mesures de la profitabilite energetique des habitats de cours d'eau pour les salmonides revelent des hausses legeres, mais significatives de la disponibilite d'energie nette dans les cours d'eau ayant recu des ajouts d'analogue, mais seulement une fois que l'effet des variations des proprietes physiques de l'habitat, comme la temperature et le debit, a ete pris en compte. [Traduit par la Redaction], Introduction The availability of habitat that meets the minimum requirements to sustain individuals over time is arguably one of the most important factors limiting populations. Habitat alteration and fragmentation are [...]

In this study we examine how the stocking of rainbow trout (Oncorhynchus mykiss), as well as the presence of fish movement barriers, influences the probability of introgression with westslope cutthroat trout (Oncorhynchus clarkii lewisi). We measured the level of introgression in cutthroat trout sampled from 32 locations that occurred either above or below fish movement barriers along with the frequency and number of rainbow trout stocked in the watershed over a 43-year period. The occurrence and level of hybridization in cutthroat trout were not related to whether the site was above a movement barrier or not. In contrast, the level of introgression was related to the distance to the nearest stocking location, the number of stocking events within the nearest watershed, and the total number of rainbow trout stocked in that watershed. Our data indicate that westslope cutthroat trout located further from stocking have a lower risk of introgression with rainbow trout, but those isolated above movement barriers should not be considered free from introgression until a thorough genetic assessment of the location has been made. Nous examinons l'influence de l'ensemencement de truites arc-en-ciel (Oncorhynchus mykiss) et de la presence de barrieres au deplacement des poissons sur la probabilite d'introgression avec la truite fardee versant de l'ouest (Oncorhynchus clarkii lewisi). Nous avons mesure le degre d'introgression chez des truites fardees prelevees de 32 sites en amont et en aval de barrieres au deplacement des poissons, ainsi que la frequence et le nombre de truites arc-en-ciel ensemencees dans le bassin versant sur une periode de 43 ans. La presence de truites fardees et leur degre d'hybridation n'etaient pas relies a l'emplacement du site par rapport a une barriere au deplacement (amont ou aval). En revanche, le degre d'introgression etait relie a la distance par rapport au site d'ensemencement le plus proche, au nombre d'evenements d'ensemencement dans le bassin versant le plus proche et au nombre total de truites arc-en-ciel ensemencees dans ce bassin versant. Nos donnees indiquent que les truites fardees versant de l'ouest situees plus loin de sites d'ensemencement presentent un risque relativement faible d'introgression avec la truite arc-en-ciel, alors que celles qui sont isolees en amont de barrieres au deplacement ne devraient pas etre considerees comme etant exemptes d'introgression si l'emplacement ou elles se trouvent n'a pas fait l'objet d'une evaluation genetique exhaustive. [Traduit par la Redaction], Introduction The introduction of non-native and captive-bred species for recreational or conservation purposes has been common in species management programs (Naish et al. 2008; Laikre et al. 2010). While often [...]

We used a bioenergetic model to determine if cutthroat trout (Oncorhynchus clarkii bouvieri) abundance was related to net energy intake rates (NEI) and the proportion of suitable habitat and to evaluate potential changes in habitat quality due to climate change and stream fertilization efforts. We conducted monthly sampling of cutthroat trout, invertebrate drift, and physical habitat features in pool and riffle habitats. Fish in this study selected foraging positions that enabled them to maximize NEI, and most fish were capable of sustaining high growth rates from July to September. Mean NEI and the proportion of suitable habitat at sites were greater in pools relative to riffle habitats and declined from July to October, primarily due to a decline in temperature over the four months. Cutthroat trout biomass was significantly related to NEI and the proportion of suitable habitat at a site. Model simulations indicated that climate change might reduce habitat quality for small-bodied trout, while extending the growing season for larger fish. Increased food abundance provided only marginal changes to model outcomes, whereas reductions in food significantly reduced habitat quality. Resume: Un modele bioenergetique nous sert a determiner si l'abondance des truites fardees (Oncorhynchus clarkii bouvieri) est reliee aux taux d'apport net d'energie (NEI) et a la proportion d'habitat adequat, ainsi qu'a evaluer les changements potentiels de qualite de l'habitat dus au changement climatique et aux efforts de fertilisation des cours d'eau. Nous avons fait un echantillonnage mensuel des truites fardees, de la derive des invertebres et des caracteristiques physiques de l'habitat dans les habitats de fosses et de rapides. Dans notre etude, les poissons choisissent des points de recherche de nourriture qui leur permettent de maximiser leur NEI et la plupart des poissons reussissent a maintenir un taux eleve de croissance de juillet a septembre. Le NEI moyen et la proportion d'habitat adequat dans les sites sont plus eleves dans les habitats de fosses que dans les rapides et diminuent de juillet a octobre, principalement a cause du declin de la temperature au cours de ces quatre mois. Il y a une relation significative entre la biomasse des truites fardees et le NEI et la proportion d'habitat adequat dans le site. Des simulations du modele indiquent que le changement climatique risque de reduire la qualite de l'habitat pour les truites de petite taille, tout en allongeant la saison de croissance des poissons plus grands. Une augmentation de l'abondance de nourriture n'apporte que des changements mineurs aux resultats du modele, alors que des reductions de nourriture diminuent significativement la qualite de l'habitat. [Traduit par la Redaction], Introduction Ecologists have long been interested in the consequences of habitat selection for predicting the distribution and abundance of animals. For many populations, accessible habitat that meets the minimum requirements [...]

When nonnative species become established within new communities, competition may play a role in determining the persistence of ecologically similar native species. In western North America, many native cutthroat trout (Oncorhynchus clarkii) populations have been replaced by nonnative rainbow trout (Oncorhynchus mykiss). Superior competitive ability of rainbow trout and cutthroat-rainbow trout hybrids is often cited for this replacement; however, few studies have tested for mechanisms that might allow introduced rainbow trout to out-compete native trout species. Our previous work found individual-based differences in swimming and foraging ability among cutthroat trout, rainbow trout, and their hybrids. In this study, we tested for the presence and strength of competition between cohorts of cutthroat trout, rainbow trout, and their reciprocal hybrids. We assayed the growth rate of juvenile cutthroat trout in allopatry versus cutthroat trout when sympatric with rainbow trout and each hybrid cross. After controlling for size and density of trout, cutthroat trout cohorts in stream channels that contained hybrid genotypes experienced lower growth than cutthroat trout in allopatry. Averaged across heterospecific treatments, cutthroat trout growth was also lower than that of cutthroat trout cohorts in allopatry. Our study suggests that juvenile cutthroat trout experience a growth disadvantage when competing against cutthroat-rainbow hybrids. Lorsque des especes non indigenes se sont etablies dans de nouvelles communautes, la competition peut jouer un role dans la determination de la persistance des especes indigenes a ecologie semblable. Dans l'ouest de l'Amerique du Nord, plusieurs populations de la truite fardee (Oncorhynchus clarkii) indigene ont ete remplacees par la truite arc-en-ciel (Oncorhynchus mykiss) non indigene. Pour expliquer cette substitution, on evoque souvent la competitivite superieure des truites arc-en-ciel et des hybrides de la truite arc-en-ciel et de la truite fardee; cependant, peu d'etudes ont cherche a verifier les mecanismes qui pourraient permettre a la truite arc-en-ciel de gagner la competition avec les especes indigenes de truites. Notre recherche anterieure a revele des differences basees sur l'individu dans la capacite de nage et de recherche de nourriture entre la truite fardee, la truite arc-en-ciel et leurs hybrides. Dans le present travail, nous cherchons a demontrer la presence et la force de la competition entre les cohortes de truites fardees, de truites arc-en-ciel et de leurs hybrids reciproques. Nous avons mesure le taux de croissance de jeunes truites fardees en conditions d'allopatrie ainsi que dans des conditions de sympatrie avec la truite arc-en-ciel et avec chacun des croisements hybrides. Apres avoir tenu compte de la taille et de la densite des truites, nous observons que les cohortes de truites fardees dans les cours d'eau contenant des genotypes hybrides ont une croissance plus faible que les truites fardees en conditions d'allopatrie. En moyenne dans toutes les conditions experimentales heterospecifiques, la croissance des truites fardees est aussi plus faible que celles des cohortes de truites fardees en conditions d'allopatrie. Notre etude indique que les jeunes truites fardees subissent un desavantage dans leur croissance lorsqu'elles sont en competition avec des hybrides de la truite fardee et de la truite arc-enciel. [Traduit par la Redaction], Introduction The role of competition, predation, and abiotic factors in determining community structure has received much attention from ecologists (Hairston et al. 1960; Strong et al. 1986). In natural communities, [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.anbehav.2007.03.025 Byline: Steven M. Seiler, Ernest R. Keeley Abstract: 'Successful' introduced species are often thought to cause declines or extinctions of native species through competitive superiority. In western North America, introduced rainbow trout, Oncorhynchus mykiss, have completely replaced many native cutthroat trout, Oncorhynchus clarkii, populations; however, few studies have identified the mechanisms that may allow rainbow trout to outcompete cutthroat trout. We raised Yellowstone cutthroat trout, Oncorhynchus clarkii bouvieri, rainbow trout, and their first generation hybrids in a common environment and conducted pairwise contests to test for differences in aggression, ability to defend a feeding station, and amount of food captured between these species and their hybrids. We did not detect a difference in number of aggressive acts conducted between cutthroat, rainbow and hybrid trout; however, cutthroat trout had the lowest success in occupying the feeding station and captured a lower proportion of food than rainbow and hybrid trout. Furthermore, hybrid crosses and rainbow trout had highest success at holding the feeding station and capturing food items when competing against cutthroat trout. Our study suggests that juvenile Yellowstone cutthroat trout are less successful at maintaining profitable feeding territories and capturing food items when competing against rainbow trout and first generation hybrids. Author Affiliation: Department of Biological Sciences, Idaho State University, U.S.A. Article History: Received 12 December 2006; Revised 26 February 2007; Accepted 29 March 2007 Article Note: (miscellaneous) MS. number: A10646

Abstract: We hypothesized that body shape differences between Yellowstone cutthroat trout (Oncorhynchus clarkii bouvieri), rainbow trout (Oncorhynchus mykiss), and their hybrids may influence swimming ability and thus play an important [...]

Abstract Background For wide-ranging species, intraspecific variation can occur as a result of reproductive isolation from local adaptive differences or from physical barriers to movement. Cutthroat trout (Oncorhynchus clarkii), a widely distributed fish species from North America, has been divided into numerous putative subspecies largely based on its isolation in different watersheds. In this study, we examined mtDNA sequence variation of cutthroat trout to determine the major phylogenetic lineages of this polytypic species. We use these data as a means of testing whether geographic isolation by watershed boundaries can be a primary factor organizing intraspecific diversification. Results We collected cutthroat trout from locations spanning almost the entire geographic range of this species and included samples from all major subspecies of cutthroat trout. Based on our analyses, we reveal eight major lineages of cutthroat trout, six of which correspond to subspecific taxonomy commonly used to describe intraspecific variation in this species. The Bonneville cutthroat trout (O. c. utah) and Yellowstone cutthroat trout (O. c. bouvieri) did not form separate monophyletic lineages, but instead formed an intermixed clade. We also document the geographic distribution of a Great Basin lineage of cutthroat trout; a group typically defined as Bonneville cutthroat trout, but it appears more closely related to the Colorado River lineage of cutthroat trout. Conclusion Our study indicates that watershed boundaries can be an organizing factor isolating genetic diversity in fishes; however, historical connections between watersheds can also influence the template of isolation. Widely distributed species, like cutthroat trout, offer an opportunity to assess where historic watershed connections may have existed, and help explain the current distribution of biological diversity across a landscape.

Fights between convict cichlids over food reveal that animals larger in size and resourceful usually win contests, though their results cannot be predicted. The aggressive behavior in convict cichlids depends on value expectation asymmetries and hunger. The resource holding potential, the state of hunger and the reproductive condition of the individual also play an important role in deciding contests.

Prioritization of efforts to maintain biodiversity is an important component of conservation, but is more often applied to ecosystems or species than within species. We assessed distinctiveness among 27 populations of rainbow trout (Salmonidae: Oncorhynchus mykiss) from British Columbia, Canada, using microsatellite DNA variation (representing historical or contemporary demography) and morphology (representing adaptive variation). Standardized genetic scores, that is, the average deviation across individuals within populations from the overall genetic score generated by factorial correspondence analysis, ranged from 1.05 to 4.90 among populations. Similar standardized morphological scores, generated by principal components analysis, ranged from 1.19 to 5.35. There was little correlation between genetic and morphological distinctiveness across populations, although one population was genetically and morphologically the most distinctive. There was, however, a significant correlation ( r = 0.26, P = 0.008) between microsatellite ( FST) and morphological ( PST) divergence. We combined measures of allelic richness, genetic variation within, and divergence among, populations and morphological variation to provide a conservation ranking of populations. Our approach can be combined with other measures of biodiversity value (habitat, rarity, human uses, threat status) to rationalize the prioritization of populations, especially for widespread species where geographic isolation across distinct environments promotes intraspecific variability. [ABSTRACT FROM AUTHOR]