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Salmon Salmo Salar (salmon + salmo_salar)
Kinds of Salmon Salmo Salar Terms modified by Salmon Salmo Salar Selected AbstractsDensity-dependent growth of young-of-the-year Atlantic salmon Salmo salar in Catamaran Brook, New BrunswickJOURNAL OF ANIMAL ECOLOGY, Issue 3 2005I. IMRE Summary 1While density-dependent mortality and emigration have been widely reported in stream salmonid populations, density-dependent growth is less frequently detected. A recent study suggests that density-dependent growth in stream salmonids occurs at low densities, whereas density-dependent mortality and emigration occur at high densities. 2To test the hypothesis that density-dependent growth occurs primarily at low rather than at high densities, we examined the relationship between average fork length and population density of young-of-the-year (YOY) Atlantic salmon at the end of the growing season using a 10-year data set collected on Catamaran Brook, New Brunswick. We tested whether (1) average body size decreases with increasing density; (2) the effect of density on average body size is greatest at low densities; (3) growth rate will decrease most rapidly at low effective densities [,(fork length)2]; (4) density-dependent growth is weaker over space than over time; and (5) the strength of density-dependent growth increases with the size of the habitat unit (i.e. spatial scale) when compared within years, but not between years. 3There was a strong negative relationship between the average body size and population density of YOY Atlantic salmon in the autumn, which was best described by a negative power curve. Similarly, a negative power curve provided the best fit to the relationship between average body size and effective density. Most of the variation in average body size was explained by YOY density, with year, location and the density of 1+ and 2+ salmon accounting for a minor proportion of the variation. 4The strength of density-dependent growth did not differ significantly between comparisons over space vs. time. Consistent with the last prediction, the strength of density-dependent growth increased with increasing spatial scale in the within-year, but not in the between-year comparisons. 5The effect of density on growth was strongest at low population densities, too low to expect interference competition. Stream salmonid populations may be regulated by two mechanisms: density-dependent growth via exploitative competition at low densities, perhaps mediated by predator-induced reductions in drift rate, and density-dependent mortality and emigration via interference competition at high densities. [source] Using quantitative real-time PCR to detect salmonid prey in scats of grey Halichoerus grypus and harbour Phoca vitulina seals in Scotland , an experimental and field studyJOURNAL OF APPLIED ECOLOGY, Issue 2 2008I. Matejusová Summary 1There is considerable debate over the impact of seal predation on salmonid populations in both the Atlantic and Pacific oceans. Conventional hard-part analysis of scats has suggested that salmonids represent a minor component of the diet of grey seals (Halichoerus grypus) and harbour seals (Phoca vitulina) in the UK. However, it is unclear whether this is an accurate reflection of the diet or due to methodological problems. To investigate this issue, we applied quantitative PCR (qPCR) to examine the presence of salmonids in the diet of seals in the Moray Firth, UK, during the summers of 2003 and 2005. 2Two qPCR assays were designed to detect Atlantic salmon Salmo salar and sea trout Salmo trutta DNA in field samples and experimentally spiked scats. The proportion of scats sampled in the field that were positive for salmonid DNA was low (ª10%). However, the DNA technique consistently resulted in more positive scats than when hard-part analysis was used. 3An experimental study using spiked scat material revealed a highly significant negative relationship between Ct values obtained from the Atlantic salmon qPCR assay and the proportion of Atlantic salmon material added to scats. The Ct value denotes the cycle number at which the increasing fluorescence signal of target DNA crosses a threshold value. Ct values from field-collected seal scats suggested they contained a very low concentration of salmonid remains (1,5%) based on an approximate calibration curve constructed from the experimental data. 4Synthesis and applications. The qPCR assay approach was shown to be highly efficient and consistent in detection of salmonids from seal scats, and to be more sensitive than conventional hard-parts analysis. Nevertheless, our results confirm previous studies indicating that salmonids are not common prey for seals in these Scottish estuaries. These studies support current management practice, which focuses on control of the small number of seals that move into key salmonid rivers, rather than targeting the larger groups of animals that haul-out in nearby estuaries. [source] The North Atlantic subpolar gyre and the marine migration of Atlantic salmon Salmo salar: the ,Merry-Go-Round' hypothesisJOURNAL OF FISH BIOLOGY, Issue 3 2010M. J. Dadswell One model for marine migration of Atlantic salmon Salmo salar proposes that North American and southern European stocks (<62° N) move directly to feeding grounds off west Greenland, then overwinter in the Labrador Sea, whereas northern European stocks (>62° N) utilize the Norwegian Sea. An alternate model proposes that both North American and European stocks migrate in the North Atlantic Subpolar Gyre (NASpG) where S. salar enter the NASpG on their respective sides of the Atlantic, and travel counterclockwise within the NASpG until returning to natal rivers. A review of data accumulated during the last 50 years suggests a gyre model is most probable. Freshwater parr metamorphose into smolts which have morphological, physiological and behavioural adaptations of epipelagic, marine fishes. Former high-seas fisheries were seasonally sequential and moved in the direction of NASpG currents, and catches were highest along the main axis of the NASpG. Marking and discrimination studies indicate mixed continental origin feeding aggregations on both sides of the Atlantic. Marked North American smolts were captured off Norway, the Faroe Islands, east and west Greenland, and adults tagged at the Faroes were recovered in Canadian rivers. Marked European smolts were recovered off Newfoundland and Labrador, west and east Greenland, and adults tagged in the Labrador Sea were captured in European rivers. High Caesium-137 (137Cs) levels in S. salar returning to a Quebec river suggested 62·3% had fed at or east of Iceland, whereas levels in 1 sea-winter (SW) Atlantic Canada returnees indicated 24·7% had fed east of the Faroes. Lower levels of 137Cs in returning 1SW Irish fish suggest much of their growth occurred in the western Atlantic. These data suggest marine migration of S. salar follows a gyre model and is similar to other open-ocean migrations of epipelagic fishes. [source] Retrospective growth analysis of Atlantic salmon Salmo salar and implications for abundance trendsJOURNAL OF FISH BIOLOGY, Issue 10 2010F. Hogan Scale archives of Atlantic salmon Salmo salar from Maine, U.S.A., were examined to determine whether ocean conditions affected the long-term trends in S. salar populations in the southern tier of the species' range in North America. To date, scale analyses of southern tier populations have been limited to hatchery fish; previous studies suggest that post-smolt growth does not influence recruitment, with the exception that winter growth may play a role in stock maturation rate. A time series of scales from the Machias and Narraguagus Rivers spanning the years 1946 to 1999 was analysed. Image analysis was used to measure intercirculi spacing, which provided proxy variables of growth rate. Post-smolt growth increment has increased since the early 1990s, as returns have decreased, suggesting that survival factors act on post-smolts independent of growth. The data support the hypothesis of a decoupling between freshwater size and early marine growth. Growth during the second sea winter was independent of post-smolt growth, suggesting that individuals are capable of significant compensatory growth. Southern tier North American stocks exhibit a similar pattern of independence between growth and survival as observed for northern tier North American stocks. These data support the inference that the recruitment of the North American and European subspecies is governed by fundamentally different mechanisms. [source] A review of the likely effects of climate change on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta, with particular reference to water temperature and flowJOURNAL OF FISH BIOLOGY, Issue 10 2009B. Jonsson The present paper reviews the effects of water temperature and flow on migrations, embryonic development, hatching, emergence, growth and life-history traits in light of the ongoing climate change with emphasis on anadromous Atlantic salmon Salmo salar and brown trout Salmo trutta. The expected climate change in the Atlantic is for milder and wetter winters, with more precipitation falling as rain and less as snow, decrease in ice-covered periods and frequent periods with extreme weather. Overall, thermal limits for salmonids are species specific. Scope for activity and growth and optimal temperature for growth increase with temperature to an optimal point before constrain by the oxygen content of the water. The optimal temperature for growth decreases with increasing fish size and varies little among populations within species, whereas the growth efficiency may be locally adapted to the temperature conditions of the home stream during the growth season. Indirectly, temperature influences age and size at smolting through its effect on growth. Time of spawning, egg hatching and emergence of the larvae vary with temperature and selective effects on time of first feeding. Traits such as age at first maturity, longevity and fecundity decrease with increasing temperature whilst egg size increases with temperature. Water flow influences the accessibility of rivers for returning adults and speed of both upstream and downstream migration. Extremes in water flow and temperature can decrease recruitment and survival. There is reason to expect a northward movement of the thermal niche of anadromous salmonids with decreased production and population extinction in the southern part of the distribution areas, migrations earlier in the season, later spawning, younger age at smolting and sexual maturity and increased disease susceptibility and mortality. Future research challenges are summarized at the end of the paper. [source] Different ocean and climate factors control the marine survival of wild and hatchery Atlantic salmon Salmo salar in the north-east Atlantic OceanJOURNAL OF FISH BIOLOGY, Issue 4 2008A. Peyronnet The influence of climate and ocean conditions on the marine survival of 1SW Irish Atlantic salmon Salmo salar was explored. Generalized additive models (GAM) explained c. 85% of the observed variations in survival and provided an insight into the mechanisms involved. A positive phase of the North Atlantic oscillation (NAO) and increasing sea surface temperatures (SST) were linked to a decrease in S. salar survival. The NAO in the winter before the smolts migration contributed to c. 70% of the deviance in marine survival of wild fish. The abundance of the copepod Calanus finmarchicus in the north-east Atlantic Ocean explained a further 25% of these variations in wild S. salar survival. By contrast, hatchery populations seem to be controlled by additional processes involving coastal SST. The marine recruitment of hatchery S. salar was largely explained (70% of the deviance) by SST close to the Irish coast in the spring before the year of the smolts migration. This study constitutes the first description of the processes controlling marine recruitment for these populations. [source] Size-independent growth in fishes: patterns, models and metricsJOURNAL OF FISH BIOLOGY, Issue 10 2008D. B. Sigourney A combination of a dynamic energy budget (DEB) model, field data on Atlantic salmon Salmo salar and brown trout Salmo trutta and laboratory data on Atlantic salmon was used to assess the underlying assumptions of three different metrics of growth including specific growth rate (G), standardized mass-specific growth rate (GS) and absolute growth rate in length (GL) in salmonids. Close agreement was found between predictions of the DEB model and the assumptions of linear growth in length and parabolic growth in mass. Field data comparing spring growth rates of age 1+ year and 2+ year Atlantic salmon demonstrated that in all years the larger age 2+ year fish exhibited a significantly lower G, but differences in growth in terms of GS and GL depended on the year examined. For brown trout, larger age 2+ year fish also consistently exhibited slower growth rates in terms of G but grew at similar rates as age 1+ year fish in terms of GS and GL. Laboratory results revealed that during the age 0+ year (autumn) the divergence in growth between future Atlantic salmon smolts and non-smolts was similar in terms of all three metrics with smolts displaying higher growth than non-smolts, however, both GS and GL indicated that smolts maintain relatively fast growth into the late autumn where G suggested that both smolts and non-smolts exhibit a sharp decrease in growth from October to November. During the spring, patterns of growth in length were significantly decoupled from patterns in growth in mass. Smolts maintained relatively fast growth though April in length but not in mass. These results suggest GS can be a useful alternative to G as a size-independent measure of growth rate in immature salmonids. In addition, during certain growth stanzas, GS may be highly correlated with GL. The decoupling of growth in mass from growth in length over ontogeny, however, may necessitate a combination of metrics to adequately describe variation in growth depending on ontogenetic stage particularly if life histories differ. [source] Factors affecting river entry of adult Atlantic salmon in a small riverJOURNAL OF FISH BIOLOGY, Issue 4 2007B. Jonsson In this study, effects of stock origin, fish size, water flow and temperature on time of river ascent of adult Atlantic salmon Salmo salar were tested. Brood stocks were collected in eight Norwegian rivers situated between 59 and 69° N. The fish were reared to smolts, individually tagged and released in the River Imsa, south-west Norway (59° N). Adults from all stocks approached the Norwegian coast concurrently, but Atlantic salmon ,70 cm in natural tip length entered coastal water slightly earlier during summer than smaller fish. Atlantic salmon <70 cm, however, ascended the river significantly earlier and at lower water flow and higher water temperature than larger fish. Although largest in size, the fish from the northern populations (62,69° N) ascended the River Imsa almost 1 month earlier than those from the south (59,60° N). They seemed less restricted by the environmental factors than the fish originating from the more southern rivers. There was no apparent trend among years in time of river ascent. Maximum ascent per day occurred at water discharges between 12·5 and 15 m3 s,1 and at water temperatures between 10 and 12·5° C. There was a significant positive correlation between water flow and river ascent during the first part of the upstream run from July to September with best correlation for September, when multiple regression analysis indicated that water temperature had an additional positive effect. Stock origin, fish size and water discharge were important variables influencing the upstream migration of Atlantic salmon in small rivers. [source] In vitro interactions between Neoparamoeba spp. and salmonid leucocytes; the effect of parasite sonicate on anterior kidney leucocyte functionJOURNAL OF FISH BIOLOGY, Issue 2006K. Gross Sonicated Neoparamoeba spp. (Nspp) did not affect the in vitro respiratory burst response of leucocytes isolated from Atlantic salmon Salmo salar, rainbow trout Oncorhynchus mykiss and chinook salmon Oncorhynchus tshawytscha anterior kidneys (P > 0·05). Atlantic salmon and chinook salmon leucocytes pre-incubated with the parasites, however, responded to phorbol myristate acetate (PMA) stimulation with a greater response compared to cells incubated with PMA on its own (P < 0·05). Sonicated Nspp was not chemo-attractive for anterior kidney leucocytes isolated from all three fish species. [source] Previously spawned Atlantic salmon ascend a large subarctic river earlier than their maiden counterpartsJOURNAL OF FISH BIOLOGY, Issue 4 2006E. Niemelä Spawning migration timing of maiden Atlantic salmon Salmo salar and previous spawners was analysed in the catches in 1989,2004 in the large subarctic River Teno in the northernmost parts of Finland and Norway. The hypothesis was that the migration timing of previous spawners and their maiden counterparts is similar, with the migration timing similar between sexes. In most cases, however, previous spawners were observed to migrate into the River Teno and its tributaries earlier than their maiden counterparts. The difference in run timing was especially evident between maiden one-sea-winter (1SW) Atlantic salmon and the corresponding group of previous spawners [1S1, 1 year at sea (1) followed by first spawning (S) and reconditioning period of 1 year (1) at sea and second spawning run] for both sexes in the River Teno and in its two tributaries. The same was also evident between 2SW maiden and 2S1 previous spawning female Atlantic salmon in the River Teno. Females showed earlier spawning migration than males both in previous spawners and maiden Atlantic salmon. Different maiden sea-age classes also showed differences in run timing as multi-sea-winter fish (2,4SW) ascended earlier than 1SW fish but the timing of 1S1 and 2S1 previous spawning females coincided. The results suggest that run timing of Atlantic salmon may not be strictly genetically fixed as previous spawners ascend earlier than they did on their first spawning migration as maiden fish, and indicated that the closeness of the reconditioning area of postspawners to the river of origin resulted in an early ascent. Run timing of different sea-age groups has major management implications if the populations are heavily exploited with numerous fishing methods in different periods of the fishing season, as in the River Teno system. [source] ,-Oxidation capacity in liver increases during parr-smolt transformation of Atlantic salmon fed vegetable oil and fish oilJOURNAL OF FISH BIOLOGY, Issue 2 2006I. Stubhaug Atlantic salmon Salmo salar were fed diets containing 100% fish oil (FO; capelin oil) or 100% vegetable oil (VO) from start of feeding until the fish reached the size of 2·5 kg. Samples were taken during the period of the parr-smolt transformation (October 2002 to February 2003). The VO diet consisted of a blend of 55% rapeseed oil, 30% palm oil and 15% linseed oil to maintain the sum of saturated, monounsaturated and polyunsaturated fatty acids between the two diets, although with differences in the individual chain length of fatty acids. Na+/K+ -ATPase activity in the gills, total ,-oxidation capacity in muscles and liver and total lipid, glycogen and dry matter content in the muscles were measured during the parr-smolt transformation and after seawater transfer. Na+/K+ -ATPase activity in gills increased prior to seawater transfer, showing an adaptation for seawater survival. Major changes in the lipid and glycogen content in the fillet and in ,-oxidation capacity were found in the tissues measured. ,-oxidation capacity increased significantly in liver and decreased in red muscle, prior to seawater transfer, giving liver an important role in energy production during this period. Results also indicated that feeding Atlantic salmon a diet where 100% of FO was replaced with VO did not have any negative effects on lipid metabolism during parr-smolt transformation. [source] Population structure in the Atlantic salmon: insights from 40 years of research into genetic protein variationJOURNAL OF FISH BIOLOGY, Issue 2005E. Verspoor Electrophoretic studies of proteins remain a primary source of insight into genetic diversity in many species including the Atlantic salmon Salmo salar, one of the most culturally and economically important fish species of the North Atlantic region. Since 1966, >350 scientific papers on protein variation have been published encompassing 25 000+ salmon from over 400 locations in >200 river systems across the species' distribution. Variation has been detected at 30% of the 110 protein loci screened, though most studies examine <40. The method has been applied largely to the investigation of population structure and differentiation, but work has also led to the systematic revision of the genus Salmo and remains the primary source of insight into hybridization in the wild with brown trout Salmo trutta. Spatial patterns of differentiation show temporal stability, both within and among river systems, and strongly support structuring of the species into river and tributary specific populations and the designation of European and North American populations as distinct sub-species. They also show widespread regional differentiation within both continents, beyond the marked subcontinental differences between Baltic Sea and Atlantic Ocean populations in Europe. Most of the differentiation probably reflects gene flow and founder events associated with colonization following the retreat of the glaciers from much of the species' modern range. However, variation at MEP-2* shows strong correlations with environmental temperature, both within and among rivers, and associations with phenotypic performance. This suggests selection is acting on the locus and provides compelling evidence for the local adaptation of populations. Protein studies have led to more population centred management of the species and have been exploited in the discrimination of regional stocks in mixed stock analysis in high seas fisheries, particularly in the Baltic Sea, and as markers for the assessment of stocking success. They have also advanced insight into how the genetic character of populations can be changed in cultivation and the potential impact of salmon aquaculture and stocking on wild populations. The method has been largely superseded by DNA based analyses, but the results remain highly relevant to Atlantic salmon management and conservation and are an irreplaceable data set for studying genetic stability of populations over time. [source] Evaluating the effect of clustering when monitoring the abundance of sea lice populations on farmed Atlantic salmonJOURNAL OF FISH BIOLOGY, Issue 3 2005C. W. Revie Using cluster random sampling theory and empirical estimates of the intra-class correlations for sea lice Lepeophtheirus salmonis abundances, methods on how best to sample Atlantic salmon Salmo salar from cages on farms were derived. Estimates of intra-class correlations for the abundance of the chalimus and mobile sea lice stages on Atlantic salmon in Scottish farms are given. These correlations were higher for mobile stages than for chalimus, and they had a substantive effect on increasing the number of cages and fish to be sampled for all sea lice stages. An important finding is that it is better to have a procedure that randomly samples a large number of cages using a small number of fish from each. This finding and the cluster random sampling approach have relevance to the monitoring of all marine species being farmed in cages or tanks. [source] Testing predictions of the critical period for survival concept using experiments with stocked Atlantic salmonJOURNAL OF FISH BIOLOGY, Issue 2004K. H. Nislow Two separate field experiments were performed in the U.S.A. and Norway with stocked Atlantic salmon Salmo salar. In the Norwegian experiment, the offspring of early-spawning fish which had larger eggs and emerged a few days before offspring of later spawning fish had consistently higher survival rates. In the U.S.A. experiment, stream sections with higher proportions of favourable foraging locations during the critical period (the transition from dependence on maternally-derived yolk reserves to independent feeding) had lower loss rates of fish stocked as unfed fry. These results provide support for the critical period concept (CPC) in Atlantic salmon, underscores the utility of a manipulative approach to achieve further advances in knowledge of Atlantic salmon ecology and provide additional guidance to management and restoration. A mechanistic, conceptual model for density dependence is presented to identify important knowledge gaps that remain to further evaluate the importance of the CPC for Atlantic salmon population regulation. [source] Effect of density on competition between wild and hatchery-reared Atlantic salmon for shelter in winterJOURNAL OF FISH BIOLOGY, Issue 2004J. E. Orpwood The effect of varying the density of hatchery-reared Atlantic salmon Salmo salar on the ability of single wild fish to occupy a shelter is assessed. Although there was strong density-dependence on sheltering overall, the ability of wild Atlantic salmon parr to occupy a shelter was not affected by the presence of hatchery-reared fish even when outnumbered by four to one. These findings illustrate a competitive asymmetry for shelter in favour of the wild fish at the densities tested. [source] Competition for shelter among over-wintering signal crayfish and juvenile Atlantic salmonJOURNAL OF FISH BIOLOGY, Issue 2 2004S. W. Griffiths Three separate effects on refuge use by signal crayfish Pacifastacus leniusculus and Atlantic salmon Salmo salar were examined: (1) the effect on Atlantic salmon of an addition of signal crayfish (doubling the total number of animals), (2) the effect on signal crayfish of an addition of Atlantic salmon and (3) intraspecific compared with interspecific competition, compared by holding total density of animals constant and varying the proportion of signal crayfish and Atlantic salmon in trials. Observations were made during winter, when both species are nocturnal. The proportion of Atlantic salmon sheltering was significantly lower in the presence than in the absence of signal crayfish when the interspecific treatment (Atlantic salmon plus signal crayfish) effected a doubling in density compared to the intraspecific treatment (Atlantic salmon alone). The proportion of signal crayfish sheltering was independent of the presence of Atlantic salmon. When total density was constant, the proportion of Atlantic salmon sheltering was significantly higher in intraspecific (52·8%) than interspecific trials (27·3%). Atlantic salmon out of shelter during the day in winter are believed to be very vulnerable to predators and the capacity for fish to share shelters with one another is known to be very low. Therefore, competition from crayfish for winter shelters may lead to detrimental effects on Atlantic salmon populations. [source] Predation on Atlantic salmon and sea trout during their first days as postsmoltsJOURNAL OF FISH BIOLOGY, Issue 3 2002C. Dieperink Radio-tagged smolts of Atlantic salmon Salmo salar and sea trout Salmo trutta were predated heavily by sea birds after crossing the saline limit in the estuary of the River Skjern, Denmark. Most predation took place within the first 9 h after estuarine entry. The field data do not contradict the hypothesis of maladaptive anti-predatory behaviour. [source] Genetic differences in physiology, growth hormone levels and migratory behaviour of Atlantic salmon smoltsJOURNAL OF FISH BIOLOGY, Issue 1 2001C. Nielsen Out of five strains of Atlantic salmon Salmo salar of 1+ years released upstream of a fyke net in the River Gudenaa in 1996, three, Lagan, Ätran and Corrib, migrated immediately, 50% of the recaptured fish reaching the net in 3,6 days. Burrishoole and Conon fish migrated with a 15,19 day delay. Smolt development in 1997 at the hatchery showed a spring surge in gill Na+, K+ -ATPase activity in all strains which was correlated with increased seawater tolerance. Differences in the timing of gill enzyme development matched the observed migration pattern well. Lagan, Ätran and Corrib strains reached high enzyme activity earlier than the Burrishoole and Conon strains, and strains with delayed enzyme development and migration showed a delayed regression of seawater tolerance compared with the early strains. Inter-strain differences in plasma growth hormone profiles could not be related to the observed patterns of Na+, K+ -ATPase and seawater tolerance development. The study gives evidence of genetic influence on the timing and intensity of smolting and subsequent migration in Atlantic salmon. [source] The pathology and seawater performance of farmed Atlantic salmon infected with glochidia of Margaritifera margaritiferaJOURNAL OF FISH BIOLOGY, Issue 4 2000J. W. Treasure The pathology of glochidial infection of the freshwater mussel Margaritifera margaritifera was examined in farmed Atlantic salmon Salmo salar in fresh water and for 150 days after transfer of salmon to sea water. Prevalence of infection in fresh water was 95%, mean abundance 134 per fish and mean infection intensity 140. Prevalence in sea water was 80,94% in the first 7 weeks after transfer but glochidia were absent, apart from remains, after 50 days in sea water. Glochidia on salmon in fresh water were associated with localized hyperplasia and fusion of secondary gill lamellae. Focally extensive epithelial hyperplasia and fusion of secondary lamellae were present 4,10 days after transfer to sea water. Twenty-three days after transfer, small nodules with a more discrete appearance were present suggesting partial resolution of tissue response; hyperplastic responses associated with glochidia were much reduced after 50 days. Plasma chloride in infected fish 10 days after transfer was 153 mmol. 1,1, significantly higher than fish without infection, suggesting poorer adaptation to sea water. No mortalities due to glochidial infection in sea water were recorded and there was no significant difference in mean weight between infected and control fish. [source] Critical habitat during the transition from maternal provisioning in freshwater fish, with emphasis on Atlantic salmon (Salmo salar) and brown trout (Salmo trutta)JOURNAL OF ZOOLOGY, Issue 4 2006J. D. Armstrong Abstract In freshwater fish, the transition from dependence on maternal yolk reserves to independent foraging can be an early critical period, with survival during this stage having a strong influence on population abundance and cohort strength. Information concerning Atlantic salmon Salmo salar and brown trout Salmo trutta as model species is reviewed to show how population dynamics are influenced by habitat use during the transitional stage and illustrate the role of maternal provisioning along with density-dependent and -independent factors. The allocation of resources in yolk and timing and position of spawning strongly influence the biotic and abiotic environments of juveniles and their subsequent performance. Vulnerability to predators, adverse environmental conditions and restricted conditions over which they can successfully forage result in specific habitat requirements for newly independent juveniles. The availability of slow-flowing habitats at stream margins during the first month of independence is crucial. Alteration of natural flow regimes and physical habitat structure, associated with a wide range of anthropogenic influences, can have significant deleterious effects on the availability of critical juvenile habitat. A model combining habitat structure and the relationship between density-dependent and -independent mortality is presented to explore the range of conditions under which the transitional period would have a strong influence on population abundance. This model provides a framework for establishing thresholds or optima for habitat availability that will favour sufficient recruitment out of the transitional stage. Using the modelling framework, managers can make informed decisions on the utility and cost effectiveness of fisheries and habitat management activities designed to increase juvenile survival during the transition to independence. A range of management options is outlined for improving habitat quality and increasing juvenile survival during the transitional period, including restoration of structural complexity, provision of suitable flow regimes, and tailoring stocking and reintroduction strategies to mimic natural dynamics. [source] Movement patterns and study area boundaries: influences on survival estimation in capture,mark,recapture studiesOIKOS, Issue 8 2008Gregg E. Horton The inability to account for the availability of individuals in the study area during capture,mark,recapture (CMR) studies and the resultant confounding of parameter estimates can make correct interpretation of CMR model parameter estimates difficult. Although important advances based on the Cormack,Jolly,Seber (CJS) model have resulted in estimators of true survival that work by unconfounding either death or recapture probability from availability for capture in the study area, these methods rely on the researcher's ability to select a method that is correctly matched to emigration patterns in the population. If incorrect assumptions regarding site fidelity (non-movement) are made, it may be difficult or impossible as well as costly to change the study design once the incorrect assumption is discovered. Subtleties in characteristics of movement (e.g. life history-dependent emigration, nomads vs territory holders) can lead to mixtures in the probability of being available for capture among members of the same population. The result of these mixtures may be only a partial unconfounding of emigration from other CMR model parameters. Biologically-based differences in individual movement can combine with constraints on study design to further complicate the problem. Because of the intricacies of movement and its interaction with other parameters in CMR models, quantification of and solutions to these problems are needed. Based on our work with stream-dwelling populations of Atlantic salmon Salmo salar, we used a simulation approach to evaluate existing CMR models under various mixtures of movement probabilities. The Barker joint data model provided unbiased estimates of true survival under all conditions tested. The CJS and robust design models provided similarly unbiased estimates of true survival but only when emigration information could be incorporated directly into individual encounter histories. For the robust design model, Markovian emigration (future availability for capture depends on an individual's current location) was a difficult emigration pattern to detect unless survival and especially recapture probability were high. Additionally, when local movement was high relative to study area boundaries and movement became more diffuse (e.g. a random walk), local movement and permanent emigration were difficult to distinguish and had consequences for correctly interpreting the survival parameter being estimated (apparent survival vs true survival). [source] Mitochondrial and peroxisomal ,-oxidation capacities in various tissues from Atlantic salmon Salmo salarAQUACULTURE NUTRITION, Issue 2 2000FrØyland In order to investigate the capacities of different tissues to oxidize fatty acids, total ,-oxidation (mitochondrial and peroxisomal) of [1,14C]palmitoyl-CoA was determined in liver and red- and white muscle from adult and juvenile Atlantic salmon Salmo salar. By including potassium cyanide (KCN) in the assay medium, it was possible to differentiate between mitochondrial and peroxisomal ,-oxidation capacities. Mitochondrial ,-oxidation dominated in all tissues except in livers from juvenile fish where the peroxisomal ,-oxidation dominated. In general, the red muscle possesses the highest fatty acid oxidation capacity, however, by taking into consideration the fact that white muscle occupies approximately 60% of the total body weight, this study demonstrates that the white muscle is an important tissue in the overall fatty acid catabolism. [source] Nutritive value of partially dehulled and extruded sunflower meal for post-smolt Atlantic salmon (Salmo salar L.) in sea waterAQUACULTURE RESEARCH, Issue 13 2006Navneet Gill Abstract This study determined the digestibility of protein in partially dehulled sunflower meal (SFM) and then, as the main goal, the nutritive value of high-temperature extruded (,149°C) partially dehulled SFM (SFMEX) for post-smolt Atlantic salmon Salmo salar in sea water. The digestibility study was conducted using the settling column approach (,Guelph system') for faeces collection as described by Hajen, Higgs, Beames and Dosanjh. In the nutritive value study, triplicate groups of 50 salmon (mean weight ,116 g) in 4000-L outdoor fibreglass tanks supplied with 25,40 L min,1, filtered, oxygenated (dissolved oxygen, 7.0,8.5 mg L,1), 11,12°C sea water (salinity, 29,31 g L,1), were fed twice daily to satiation one of five steam-pelleted dry diets that contained 422 g of digestible protein (DP) kg,1 and ,16.4 MJ of digestible energy (DE) kg,1 on a dry weight basis for 84 days. Low-temperature-dried anchovy meal (LT-AM) comprised 68.2% of the basal diet protein whereas in four test diets, SFMEX progressively replaced up to 33.0% of the DP provided by LT-AM in the basal diet (SFMEX,271 g kg,1 of dry matter). Sunflower meal had 87.9% DP. Diet treatment did not significantly affect specific growth rate (1.39,1.45% day,1), feed efficiency (1.19,1.26), percentage of dietary protein retained (45.8,47.5), gross energy utilization (46.5,49.4%), per cent survival (96.0,99.3) or terminal whole body and muscle proximate compositions. We conclude that SFMEX can comprise ,271 g kg,1 of the dry diet or ,22.7% of the digestible dietary protein of post-smolt Atlantic salmon in seawater without any adverse effects on their performance. [source] Fish movements: the introduction pathway for topmouth gudgeon Pseudorasbora parva and other non-native fishes in the UKAQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 3 2010G. H. Copp Abstract 1.The contamination of fish consignments (for stocking or aquaculture) is a major pathway by which non-native organisms, including fish, are introduced to new areas. One of the best examples of this is the topmouth gudgeon Pseudorasbora parva, which was accidentally imported into Romania and then throughout Europe in consignments of Asian carp species. 2.The introduction and spread of topmouth gudgeon in the UK has been linked to imports and movements of the ornamental variety (golden orfe) of ide Leuciscus idus. To examine this hypothesis, relationships between authorized movements of both native and non-native fish species (in particular ide) and the occurrence in England of topmouth gudgeon were tested at the 10×10,km scale. 3.Topmouth gudgeon occurrence in the wild was significantly correlated with the trajectories of movements of ornamental fish species (ide/orfe, sunbleak Leucaspius delineatus) as well as a few non-ornamental fish species (European catfish Silurus glanis, Atlantic salmon Salmo salar and grass carp Ctenopharyngodon idella). 4.These results highlight the mechanism by which non-native fish species disperse from the point of first introduction, and especially that movements of fish within the country represent an important mechanism for accidental introductions of non-native species. © Crown copyright 2010. Reproduced with the permission of Her Majesty's Stationery Office. Published by John Wiley & Sons, Ltd. [source] | |||||||||||||