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Salmonid Fishes (salmonid + fish)
Selected AbstractsWhat can otolith examination tell us about the level of perturbations of Salmonid fish from the Kerguelen Islands?ECOLOGY OF FRESHWATER FISH, Issue 4 2008F. Morat Abstract,,, Otoliths preserve a continuous record of the life cycle from the natal through the adult stage. For that reason, the morphological and chemical characteristics of otoliths of two nonnative Salmonids, brown trout (Salmo trutta) and brook charr (Salvelinus fontinalis) from populations on the Kerguelen Islands were compared. Several approaches were used to study the relationships between otolith morphometry, crystal morph and chemical elemental composition. These salmonids sampled in Kerguelen are well differentiated in terms of species through their otolith shape. The results indicate that ecotypes and river populations can be reasonably well differentiated on the basis of otolith shape. The crystallisation study has revealed the presence of a particular form: the vaterite, present at a high rate: 45% of S. fontinalis and 18% from Salmo trutta fario. Moreover, vaterite and aragonite otoliths presented differences in chemical composition. [source] Genetic restoration of a stocked brown trout Salmo trutta population using microsatellite DNA analysis of historical and contemporary samplesJOURNAL OF APPLIED ECOLOGY, Issue 4 2006MICHAEL M. HANSEN Summary 1Gene flow from domesticated to wild populations is a major threat to wild salmonid fish. However, few studies have addressed how populations could be restored after admixture has occurred. We analysed the prospects for restoring the previously intensively stocked brown trout population of the Skjern River, Denmark, by identifying remaining non-admixed individuals to be used for supportive breeding. 2We analysed microsatellite DNA markers in historical (1940,50s) and contemporary (1992,2004) samples from the Skjern River system, from the strain of domesticated trout previously used for stocking, and from the neighbouring Storå River. We analysed admixture proportions to estimate the genetic contribution by domesticated trout. We identified non-admixed trout using assignment tests, and further analysed the possible sources of indigenous trout by estimating contemporary migration among populations. 3Genetic differentiation between the historical Storå and Skjern river populations was low (,ST = 0·004), suggesting considerable gene flow in the past. The contemporary Skjern and Storå river populations and a supportive breeding brood stock were strongly admixed, but some non-admixed individuals nevertheless remained in the wild-caught samples. In addition, two resident populations in isolated tributaries were found to be indigenous. The indigenous anadromous individuals from the Skjern River were unlikely to have been recruited from either the isolated tributary populations or the neighbouring Storå River and were presumably derived from unidentified spawning sites in the river system. 4All but one non-admixed anadromous Skjern River trout were females, which we ascribed to sampling bias. Moreover, all non-admixed fish were late-spawning (January,February) whereas the majority of all trout caught for the study were ripe by November,December. The difference in spawning time could be an important factor delaying complete admixture of domesticated and indigenous trout. 5Synthesis and applications. This study demonstrates the feasibility of restoring populations that have been admixed with exogenous individuals, by identifying non-admixed individuals using genetic markers. However, the results also highlight the problem that numbers of identified non-admixed individuals may be small, necessitating identification of nearby, closely related populations that can be incorporated into breeding programmes. [source] Real time PCR detection of Piscirickettsia salmonis from formalin-fixed paraffin-embedded tissuesJOURNAL OF FISH DISEASES, Issue 10 2008S Karatas Abstract Piscirickettsia salmonis is the causative agent of piscirickettsiosis, a transmissible disease of salmonid fish. Diagnosis of piscirickettsiosis has traditionally been based upon identification of typical pathological changes by histological investigation, with confirmation by immunohistochemistry on formalin-fixed, paraffin-embedded tissues. However, implementation of more rapid confirmatory techniques, preferably with higher levels of sensitivity and possibilities for quantification, is desirable. A real-time polymerase chain reaction (PCR) assay was designed for specific detection of P. salmonis and tested on samples extracted from formalin-fixed paraffin-embedded material. Construction of a PCR-target mimic allowed determination of detection limits, linearity of the real-time PCR and quantitative detection of P. salmonis. The present study demonstrates the capability of the described real time PCR assay for detection of P. salmonis from paraffin-embedded material with a high degree of sensitivity and specificity. Implementation of this assay constitutes an important development for a rapid and secure diagnosis of piscirickettsiosis. [source] Yersinia ruckeri infections in salmonid fishJOURNAL OF FISH DISEASES, Issue 5 2007E Tobback Abstract Yersinia ruckeri is the causative agent of yersiniosis or enteric redmouth disease leading to significant economic losses in salmonid aquaculture worldwide. Infection may result in a septicaemic condition with haemorrhages on the body surface and in the internal organs. Despite the significance of the disease, very little information is available on the pathogenesis, hampering the development of preventive measures to efficiently combat this bacterial agent. This review discusses the agent and the disease it causes. The possibility of the presence of similar virulence markers and/or pathogenic mechanisms between the Yersinia species which elicit disease in humans and Y. ruckeri is also examined. [source] Development of proliferative kidney disease in rainbow trout, Oncorhynchus mykiss (Walbaum), following short-term exposure to Tetracapsula bryosalmonae infected bryozoansJOURNAL OF FISH DISEASES, Issue 8 2002M Longshaw The initial site of infection in the fish host for Tetracapsula bryosalmonae, causative agent of proliferative kidney disease (PKD) is poorly understood. Following the recent recognition that freshwater bryozoans harbour the infective stages to salmonid fish, experimental transmission studies were undertaken to investigate (1) the route of entry of the parasite into the fish host and (2) the minimum exposure time required to induce clinical signs of PKD. In-situ hybridization (ISH) studies were carried out on naïve rainbow trout exposed to the naturally infected bryozoan Fredericella sultana for up to 90 min. The sporoplasm of T. bryosalmonae was detected entering the fish via mucous cells in the skin epithelium within the first minute of exposure. In addition, T. bryosalmonae cells were infrequently detected in the skeletal musculature of exposed experimental fish up to 72 h post-exposure. The route of migration through the fish to the kidney and spleen was not determined. All fish exposed to infected, disrupted bryozoans for 10, 30 and 90 min and maintained for up to 8 weeks developed clinical PKD. [source] Comparison of Small Subunit Ribosomal RNA Gene and Internal Transcribed Spacer Sequences Among Isolates of the Intranuclear Microsporidian Nucleospora salmonisTHE JOURNAL OF EUKARYOTIC MICROBIOLOGY, Issue 4 2000STEPHANE J. GRESOVIAC ABSTRACT. Nucleospora salmonis is an intranuclear microsporidian associated with a proliferative disorder of the lymphoid cells of captive salmonid fish in the northwestern and northeastern regions of North America, in France, and in Chile. Newer diagnostic approaches have used the polymerase chain reaction (PCR) to detect the parasite in fish tissues. The target sequences for these assays lie in the small subunit ribosomal RNA (ssu rRNA) gene or internal transcribed spacer (ITS) as determined from N. salmonis from chinook salmon (Oncorhynchus tshawytscha) from the Pacific Northwest of North America. The lack of sequence data on parasites from diverse geographic origins and hosts led us to compare several isolates of N. salmonis. There was a high degree of similarity in the ssu rDNA sequences (> 98%) among all the isolates of N. salmonis examined, regardless of host or geographic origin. The greatest sequence differences were found between isolates from the Pacific regions of America. Isolates from Chile shared sequences with one or both geographic groups from North America. A similar distribution of sequence types was observed when ITS-1 sequences of selected isolates were analyzed. Sequence data from two N. salmonis -like isolates from marine non-salmonid fish showed one closely related and the second less closely related to N. salmonis isolates from salmonid fish. These results provide evidence for a homogeneous group of aquatic members of the genus Nucleospora found among salmonid fish (N. salmonis) that can be detected using diagnostic PCR assays with ssu rDNA target sequences. The presence of parasites related to N. salmonis among marine fish suggests a potentially broad host and geographic distribution of members of the family Enterocytozoonidae. [source] Appraising riparian management effects on benthic macroinvertebrates in the Wye River systemAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue S1 2010Esther Clews Abstract 1.Agriculture, urbanization or forestry in river catchments can influence river organisms through diffuse effects on hydrology and hydrochemistry, or local effects on habitat character, bank erosion and sediment delivery. Riparian buffer zones are sometimes established to mitigate undesirable effects on salmonids, but consequences for organisms such as macroinvertebrates are less well known. 2.Riparian fencing and tree coppicing were carried out on upland tributaries of the Welsh River Wye (UK) from 1997 onwards with the aim of enhancing conditions for salmonid fish. The present study used routine, agency monitoring data to compare assemblages in three recently managed streams and five adjacent control streams. Data between 1995 and 2004 were used to assess treatment effects through time. 3.Post-treatment (2000,2004) assemblages were richer in recently managed streams than in controls, mostly due to apparent gains of taxa typical of channel margins and lowland, warmer conditions. However, results were equivocal because invertebrate families typical of lowland, more eutrophic conditions increased in occurrence in all reaches irrespective of treatment, while overall richness declined. 4.This study illustrates how routine monitoring data can reveal some effects of riparian land-use and management on stream biota. However, improved experimental design, ideally using a before,after control,intervention approach, would have allowed more effective assessment in this case study where confounding trends were so marked. We advocate using such approaches in future restoration studies to allow stronger inference and greater statistical power. The recent general decline in the richness of typical headwater organisms in the Wye system requires investigation. Copyright © 2010 John Wiley & Sons, Ltd. [source] Comparative phylogeography of salmonid fishes (Salmonidae) reveals late to post-Pleistocene exchange between three now-disjunct river basins in SiberiaDIVERSITY AND DISTRIBUTIONS, Issue 4 2003E. Froufe Abstract. We use a comparative phylogeographical framework to evaluate the hypothesis of hydrological exchange during the Pleistocene among the now disjunct Lena, Amur, and Enisei basins in Siberia, and to provide evidence on the causal mechanism of their present day faunal dissimilarities. Approximately 600 bases of the mitochondrial control region were sequenced in five distinct lineages among three genera of salmonid fishes, Hucho, Brachymystax and Thymallus. All three basins were fixed for divergent (2,5.4%) lineages of Thymallus whereas a single shared haplotype was present in all three basins for Hucho taimen (Pallas, 1773) and one shared haplotype between the Lena and Amur basins out of a total of five for blunt-snouted and one out of five for sharp-snouted Brachymystax lenok (Pallas, 1773). For both blunt- and sharp-snouted lenok the haplotypes found within each basin did not form clades, so no relationship between genotypes and geographical occurrence was found. Our data support relatively recent hydrological mixing of the major river drainage systems in eastern and far-eastern Siberia, congruent with the hypothesis of large-scale palaeo-hydrological exchange stemming from glacial advance, retreat and melting during Pleistocene climate fluctuations. Furthermore, these results in conjunction with a comparison of overall faunal composition suggest that environmental differences rather than historical contingency may be responsible for the faunal dissimilarities of the Amur, Lena, and Enisei river basins. [source] COMPARATIVE PHYLOGENETIC ANALYSIS OF THE EVOLUTION OF SEMELPARITY AND LIFE HISTORY IN SALMONID FISHESEVOLUTION, Issue 5 2002Bernard J. Crespi Abstract The selective pressures involved in the evolution of semelparity and its associated life-history traits are largely unknown. We used species-level analyses, independent contrasts, and reconstruction of ancestral states to study the evolution of body length, fecundity, egg weight, gonadosomatic index, and parity (semelparity vs. degree of iteroparity) in females of 12 species of salmonid fishes. According to both species-level analysis and independent contrasts analysis, body length was positively correlated with fecundity, egg weight, and gonadosomatic index, and semelparous species exhibited a significantly steeper slope for the regression of egg weight on body length than did iteroparous species. Percent repeat breeding (degree of iteroparity) was negatively correlated with gonadosomatic index using independent contrasts analysis. Semelparous species had significantly larger eggs by species-level analysis, and the egg weight contrast for the branch on which semelparity was inferred to have originated was significantly larger than the other egg weight contrasts, corresponding to a remarkable increase in egg weight. Reconstruction of ancestral states showed that egg weight and body length apparently increased with the origin of semelparity, but fecundity and gonadosomatic index remained more or less constant or decreased. Thus, the strong evolutionary linkages between body size, fecundity, and gonadosomatic index were broken during the transition from iteroparity to semelparity. These findings suggest that long-distance migrations, which increase adult mortality between breeding episodes, may have been necessary for the origin of semelparity in Pacific salmon, but that increased egg weight, leading to increased juvenile survivorship, was crucial in driving the transition. Our analyses support the life-history hypotheses that a lower degree of repeat breeding is linked to higher reproductive investment per breeding episode, and that semelparity evolves under a combination of relatively high juvenile survivorship and relatively low adult survivorship. [source] How well are velocity effects on ,13C signatures transmitted up the food web from algae to fish?FRESHWATER BIOLOGY, Issue 6 2010JOSEPH B. RASMUSSEN Summary 1. Benthic algae fractionate carbon isotopes less at low water velocities because of reduced boundary layer exchange, and this effect on ,13C is passed on to consumers via trophic transfer. This study examines the relationships between ,13C signatures of consumers (invertebrates and salmonid fishes) and water velocity in the Sainte Marguerite River, QC, Canada, and compares them to patterns for periphyton, both along the river main-stem and in a small tributary. 2. Relationships of ,13C signatures of herbivore/grazers and collector/gatherers with water velocity were strong and similar to those of periphyton, but relationships for filter-feeders were weak, probably reflecting the effect of spatial averaging of their food supply as a result of downstream transport. 3. Velocity effects on salmonid signatures were much weaker than those of lower trophic levels, being barely significant except in the small tributary where the fish were resident and isolated from the main river. In the river main-stem, even when reach standardised (reach mean subtracted from each data point), fish signatures were only weakly related to water velocity. 4. The fidelity with which velocity effects are transmitted to consumers from benthic algae is highly variable, and depends on a combination of consumer and resource movements, in addition to the trophic position of the consumer. [source] The role of trout in stream food webs: integrating evidence from field surveys and experimentsJOURNAL OF ANIMAL ECOLOGY, Issue 2 2006KRISTIAN MEISSNER Summary 1We evaluated the effects of brown trout on boreal stream food webs using field surveys and enclosure/exclosure experiments. Experimental results were related to prey preference of uncaged trout in the same stream, as well as to a survey of macroinvertebrate densities in streams with vs. without trout. Finally, we assessed the generality of our findings by examining salmonid predation on three groups of macroinvertebrate prey (chironomid midges, epibenthic grazers, invertebrate predators) in a meta-analysis. 2In a preliminary experiment, invertebrate predators showed a strong negative response to trout, whereas chironomids benefited from trout presence. In the main experiment, trout impact increased with prey size. Trout had the strongest effect on invertebrate predators and cased caddis larvae, whereas Baetis mayfly and chironomid larvae were unaffected. Trout impact on the largest prey seemed mainly consumptive, because prey emigration rates were low and independent of fish presence. Despite strong effects on macroinvertebrates, trout did not induce a trophic cascade on periphyton. Uncaged trout showed a strong preference for the largest prey items (predatory invertebrates and aerial prey), whereas Baetis mayflies and chironomids were avoided by trout. 3Densities of invertebrate predators were significantly higher in troutless streams. Baetis mayflies also were less abundant in trout streams, whereas densities of chironomids were positively, although non-significantly, related to trout presence. Meta-analysis showed a strong negative impact of trout on invertebrate predators, a negative but variable impact on mobile grazers (mainly mayfly larvae) and a slightly positive impact on chironomid larvae. 4Being size-selective predators, salmonid fishes have a strong impact on the largest prey types available, and this effect spans several domains of scale. Discrepancies between our experimental findings and those from the field survey and meta-analysis show, however, that for most lotic prey, small-scale experiments do not reflect fish impact reliably at stream-wide scales. 5Our findings suggest that small-scale experiments will be useful only if the experimental results are evaluated carefully against natural history information about the experimental system and interacting species across a wide array of spatial scales. [source] Fine-scale natal homing and localized movement as shaped by sex and spawning habitat in Chinook salmon: insights from spatial autocorrelation analysis of individual genotypesMOLECULAR ECOLOGY, Issue 14 2006H. M. NEVILLE Abstract Natal homing is a hallmark of the life history of salmonid fishes, but the spatial scale of homing within local, naturally reproducing salmon populations is still poorly understood. Accurate homing (paired with restricted movement) should lead to the existence of fine-scale genetic structuring due to the spatial clustering of related individuals on spawning grounds. Thus, we explored the spatial resolution of natal homing using genetic associations among individual Chinook salmon (Oncorhynchus tshawytscha) in an interconnected stream network. We also investigated the relationship between genetic patterns and two factors hypothesized to influence natal homing and localized movements at finer scales in this species, localized patterns in the distribution of spawning gravels and sex. Spatial autocorrelation analyses showed that spawning locations in both sub-basins of our study site were spatially clumped, but the upper sub-basin generally had a larger spatial extent and continuity of redd locations than the lower sub-basin, where the distribution of redds and associated habitat conditions were more patchy. Male genotypes were not autocorrelated at any spatial scale in either sub-basin. Female genotypes showed significant spatial autocorrelation and genetic patterns for females varied in the direction predicted between the two sub-basins, with much stronger autocorrelation in the sub-basin with less continuity in spawning gravels. The patterns observed here support predictions about differential constraints and breeding tactics between the two sexes and the potential for fine-scale habitat structure to influence the precision of natal homing and localized movements of individual Chinook salmon on their breeding grounds. [source] Genetic characterization of hybridization and introgression between anadromous rainbow trout (Oncorhynchus mykiss irideus) and coastal cutthroat trout (O. clarki clarki)MOLECULAR ECOLOGY, Issue 4 2001William P. Young Abstract Interspecific hybridization represents a dynamic evolutionary phenomenon and major conservation problem in salmonid fishes. In this study we used amplified fragment length polymorphisms (AFLP) and mitochondrial DNA (mtDNA) markers to describe the extent and characterize the pattern of hybridization and introgression between coastal rainbow trout (Oncorhynchus mykiss irideus) and coastal cutthroat trout (O. clarki clarki). Hybrid individuals were initially identified using principle coordinate analysis of 133 polymorphic AFLP markers. Subsequent analysis using 23 diagnostic AFLP markers revealed the presence of F1, rainbow trout backcross, cutthroat trout backcross and later-generation hybrids. mtDNA analysis demonstrated equal numbers of F1 hybrids with rainbow and cutthroat trout mtDNA indicating reciprocal mating of the parental types. In contrast, rainbow and cutthroat trout backcross hybrids always exhibited the mtDNA from the recurrent parent, indicating a male hybrid mating with a pure female. This study illustrates the usefulness of the AFLP technique for generating large numbers of species diagnostic markers. The pattern of hybridization raises many questions concerning the existence and action of reproductive isolating mechanisms between these two species. Our findings are consistent with the hypothesis that introgression between anadromous populations of coastal rainbow and coastal cutthroat trout is limited by an environment-dependent reduction in hybrid fitness. [source] Degeneration and regeneration of ultraviolet cone photoreceptors during development in rainbow troutTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 5 2006W. Ted Allison Abstract Ultraviolet-sensitive (UVS) cones disappear from the retina of salmonid fishes during a metamorphosis that prepares them for deeper/marine waters. UVS cones subsequently reappear in the retina near sexual maturation and the return migration to natal streams. Cellular mechanisms of this UVS cone ontogeny were investigated using electroretinograms, in situ hybridization, and immunohistochemistry against opsins during and after thyroid hormone (TH) treatments of rainbow trout (Oncorhynchus mykiss). Increasing TH levels led to UVS cone degeneration. Labeling demonstrated that UVS cone degeneration occurs via programmed cell death and caspase inhibitors can inhibit this death. After the cessation of TH treatment, UVS cones regenerated in the retina. Bromodeoxyuridine (BrdU) was applied after the termination of TH treatment and was detected in the nuclei of cells expressing UVS opsin. BrdU was found in UVS cones but not other cone types. The most parsimonious explanation for the data is that UVS cones degenerated and UVS cones were regenerated from intrinsic retinal progenitor cells. Regenerating UVS cones were functionally integrated such that they were able to elicit electrical responses from second-order neurons. This is the first report of cones regenerating during natural development. Both the death and regeneration of cones in retinae represent novel mechanisms for tuning visual systems to new visual tasks or environments. J. Comp. Neurol. 499:702,715, 2006. © 2006 Wiley-Liss, Inc. [source] | ||||||||||