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1.
Abstract. Loma salmonae (Putz, Hoffman and Dunbar, 1965), Morrison & Sprague, 1981, in the rainbow trout, Salmo gairdneri Richardson, was studied with the electron microscope. It is morphologically very similar to L. morhua Morrison and Sprague, 1981, in the Atlantic cod, Gadus morhua L., having only minor differences. Loma sp. Morrison and Sprague, 1981, in the brook trout, Salvelinus fontinalis (Mitchill), is more like L. salmonae than the other species of Loma , but was deemed to be distinct. It was named L. fontinalis sp. nov.  相似文献   

2.
Plan Vianney lake, situated in the Oisans massif (French Alps) at an altitude of 2250 m, has a fish fauna composed of brook trout, Salvelinus fontinalis (Mitchell), and Artic charr, Salvelinus alpinus (L.). The present study examines the feeding behaviour of S. fontinalis in 1993–94 but also gives some data on S. alpinus . The brook trout represented 80% of the fish fauna of the lake. Dietary analysis showed that this species is an opportunistic feeder and revealed similarities in the trophic niches of S. fontinalis and S. alpinus and a low level of potentially available food resources. The annual growth of S. fontinalis was short and the growth rate was slow compared with other populations. Under these extreme conditions, female fish required several summers to replenish their reserves of energy and were only in condition to spawn once every 2 or 3 years. Although the fecundity of the population was low, it was sufficient to maintain the species in the lake which is not exploited.  相似文献   

3.
Abstract. Laboratory-raised Cryptobia -susceptible brook charr, Salvelinus fontinalis (Mitchill), and rainbow trout, Oncorhynchus mykiss (Walbaum), were vaccinated intraperitoneally with a live Cryptobia salmositica vaccine (250000 parasites per fish), and 4 weeks later were challenged with the pathogen (250000 parasites per fish). Unvaccinated and infected brook charr had high parasitaemias but no clinical signs of disease, while unvaccinated and infected rainbow trout had anaemia and general oedema. Vaccinated and challenged fish had very low parasitaemias compared to unvaccinated and infected brook charr and rainbow trout. Complement fixing antibodies were detected in vaccinated and challenged fish 2 weeks after challenge. Unvaccinated and infected brook charr had consistently higher litres of complement fixing antibody than unvaccinated and infected rainbow trout. Parasitaemias were lower in all fish in which titres of complement fixing antibody were high. In a second experiment, brook charr inoculated intraperitoneally or intramuscularly with 100000 C. salmositica per fish had high parasitaemias but no anaemia or other clinical signs. The results show that susceptible brook charr do not suffer from cryptobiosis and may serve as reservoir hosts for C. salmositica in areas where the disease is prevalent. Vaccination to reduce the parasitaemia when fish become infected may be a control strategy in these areas.  相似文献   

4.
Abstract  This study investigated the effects of low summer discharge on habitat, prey use and prey availability for age 1 brook trout, Salvelinus fontinalis (Mitchill), in two small streams in Massachusetts, USA. Stream discharge declined substantially from June to August, with corresponding decreases in microhabitat depth and velocity; but fish habitat preferences were consistent throughout the summer, with fish selecting deep, low current velocity locations. Invertebrate drift rate, drift density and trout stomach fullness were significantly greater in June than August samples. Diets were dominated by aquatic-derived prey (chironomid larvae and adult blackflies) in June, but terrestrial invertebrates were the most frequent diet items in August. Consistent occupancy of low-velocity, deep microhabitats with low invertebrate flux rates indicated that, despite variation in habitat and prey conditions, trout adopted a habitat-use strategy of minimising risks and energy costs rather than maximising forage gain. This observation is consistent with, and provides a potential explanation for, the low summer growth rates of brook trout observed in small streams.  相似文献   

5.
Macneale KH, Sanderson BL, Courbois J-YP, Kiffney PM. Effects of non-native brook trout ( Salvelinus fontinalis ) on threatened juvenile Chinook salmon ( Oncorhynchus tshawytscha ) in an Idaho stream.
Ecology of Freshwater Fish 2010: 19: 139–152. © 2009 John Wiley & Sons A/S
Abstract –  Non-native fishes have been implicated in the decline of native species, yet the mechanisms responsible are rarely apparent. To examine how non-native brook trout may affect threatened juvenile Chinook salmon, we compared feeding behaviours and aggressive encounters between these sympatric fish in Summit Creek, Idaho. Snorkelers observed 278 focal fish and examined diets from 27 fish in late summer 2003. Differences in feeding behaviours and diets suggest that there was minimal current competition for prey, although individual Chinook feeding activity declined as their encounter rate with other fish increased. While difference in size between fish generally determined the outcome of encounters (larger fish 'winning'), it was surprising that in some interspecific encounters aggressive Chinook displaced slightly larger brook trout (≤20 mm longer). We suggest that in late summer, frequent intraspecific interactions may be more important than interspecific interactions in potentially limiting Chinook growth in Summit Creek and perhaps in other oligotrophic streams where they co-occur.  相似文献   

6.
Abstract. Aeromonas salmonicida , the aetiologic agent of furunculosis, causes high mortality in cultured salmonids. Experiments were conducted to determine the therapeutic and prophylactic efficacy of passive immunization against furunculosis in brook trout, Salvelinus fontinalis (Mitchill), infected by immersion. Rabbit hyperimmune serum was produced against a virulent strain of A. salmonicida and an aliquot of this serum was absorbed with cells of a non-virulent strain of A. salmonicida. Immunoglobulins from aliquots of the absorbed and non-absorbed serum were purified using affinity chromatography. Each serum or immunoglobulin preparation was tested in passive immunization experiments. Brook trout were infected by immersion in a suspension of virulent A. salmonicida , and passively immunized by intraperitoneal injection at the time of experimental infection, or at various periods after experimental infection. Passive immunization of brook trout against furunculosis was therapeutically efficacious when effected either at zero, 24 or 48h post-infection, but not at 72 or 96h. Purified rabbit immunoglobulins specific to virulent A. salmonicida were as protective as the initial rabbit hyperimmune serum in protecting brook trout against furunculosis. To determine the prophylactic efficacy of this treatment, the groups of fish passively immunized at the time of the experimental infection were challenged a second time at either 14, 35, 41 or 56 days after passive immunization. Brook trout were protected against a second experimental bath challenge with virulent A. salmonicida for a period of 35–41 days.  相似文献   

7.
Abstract Seasonal habitat use by over-yearling and under-yearling brook trout, Salvelinus fontinalis (Mitchill), was examined in a second-order stream in north-central Pennsylvania, USA. The habitat occupied by brook trout and available habitat were determined in a 0.5-km stream reach during the spring, summer and autumn of 1989 and the spring and summer of 1990. Cover, depth, substrate and velocity were quantified from over 2000 observations of individual brook trout. Habitat used by under-yearling brook trout was more uniform between seasons and years than that used by over-yearling brook trout. Over-yearling brook trout occupied areas with more cover and greater depth than did under-yearling brook trout, suggesting ontogenetic shifts in these variables. Differences for velocity and substrate were not as great as those for cover and depth. The selection of areas with low water velocities governed trout habitat use in spring, whereas cover and depth were the most important habitat variables in summer and autumn. Principal component analysis showed that available habitat and trout habitat centroids diverged most in spring, indicating that habitat selection by brook trout may be greatest at this time.  相似文献   

8.
Laboratory and in‐stream enclosure experiments were used to determine whether rainbow trout Oncorhynchus mykiss influence survival of longnose dace Rhinichthys cataractae. In the laboratory, adult rainbow trout preyed on longnose dace in 42% of trials and juvenile rainbow trout did not prey on longnose dace during the first 6 h after rainbow trout introduction. Survival of longnose dace did not differ in the presence of adult rainbow trout previously exposed to active prey and those not previously exposed to active prey ( = 0.28, P = 0.60). In field enclosures, the number of longnose dace decreased at a faster rate in the presence of rainbow trout relative to controls within the first 72 h, but did not differ between moderate and high densities of rainbow trout (F2,258.9 = 3.73, P = 0.03). Additionally, longnose dace were found in 7% of rainbow trout stomachs after 72 h in enclosures. Rainbow trout acclimated to the stream for longer periods had a greater initial influence on the number of longnose dace remaining in enclosures relative to those acclimated for shorter periods regardless of rainbow trout density treatment (F4,148.5 = 2.50, P = 0.04). More research is needed to determine how predation rates will change in natural environments, under differing amounts of habitat and food resources and in the context of whole assemblages. However, if rainbow trout are introduced into the habitat of longnose dace, some predation on longnose dace is expected, even when rainbow trout have no previous experience with active prey.  相似文献   

9.
Brook trout are the one of the only Salvelinus species native to eastern North America and range from Canada to Georgia. Very little is known, however, about the ecology of the southern form of this species. We quantified microhabitat use of southern brook trout in Ball Creek NC, a third‐order stream, during six seasonal samples (summer 2010, autumn 2010, spring 2011, summer 2011, autumn 2011 and spring 2012). In general, trout preferentially occupied deeper microhabitats with lower mean velocities and higher amounts of erosional substrata than were randomly available. Older trout (1+ and 2+) occupied deeper microhabitats with lower mean velocities than yearling trout. These microhabitats typically represent ‘plunge pools’. Southern brook trout also occupied focal point velocities that were statistically indistinguishable from optimal velocities calculated for rainbow trout in the same system and thus may chose microhabitats that maximise net energy gain. Southern brook trout are found in isolated populations, and management strategies should focus on the preservation of plunge pool habitat for conservation of this subspecies.  相似文献   

10.
Three small Newfoundland lakes were fished to estimate the population sizes of Atlantic salmon, Salmo salar L., parr and brook trout, Salvelinus fontinalis (Mitchill), and to study within-lake movements of the species. The whole shoreline of the lakes was seined, the catches in different sections were recorded separately and the fish were given different marks. Estimates for the lakes derived from different subareas were constantly lower than the estimate derived by using the data from the whole shoreline. If estimates of the different sub-areas were extrapolated according to their proportion of the shoreline, they were positively biased, and showed higher variance. Significant correlations between the movement rates and the accuracy of sub-area population estimates and recapture rates were found. Validation of the assumption of random mixing of marked and unmarked fish, when a spatially stratified sampling is carried out, is emphasized.  相似文献   

11.
We monitored water chemistry and populations of brook trout (Salvelinus fontinalis) and mottled sculpins (Cottus bairdi) in 5 streams and some tributaries to determine how the severity of acidic episodes (low pH and high Al) influenced density and distribution of these species. Among streams, Linn Run had the lowest pH (4.8) and highest concentrations of total dissolved Al (>400 μg-l?1) during periods of high discharge. Densities of brook trout and mottled sculpins were low in Linn Run, but high in tributaries, where pH (6.5) and Al (30 μg-l?1) remained well below lethal levels. Among the other streams, brook trout density was highest where the acidic episodes were least severe and the density of age-0 brook trout was lowest when precipitation during the early months of the year was above normal. Immigration of brook trout from downstream areas maintained populations in the stream segments subjected to severe episodes. Mottled sculpins were not found in streams with severe episodes.  相似文献   

12.
Ontario supports a vast fisheries resource with an abundance of lakes, rivers and streams. A landscape approach to management informed by a broad‐scale monitoring programme has been initiated to assess the status of fisheries within lakes. However, not all species are assessed by this programme, and there is no provincial monitoring of species inhabiting rivers and streams. As such, changes in the status of a species such as brook trout, Salvelinus fontinalis (Mitchill), could be entirely missed. Brook trout is a highly valued and sought after species by anglers within the province, but there are concerns the species is declining. Given the paucity of broad, empirical data, the status and trends of brook trout across the province have been based on expert opinion at multiple local scales. In 2016, a online questionnaire was sent to brook trout experts to determine status, stressors, management approaches and assess risks (magnitude and probability) to lake and river/stream populations in different geographic areas of Ontario. A Bayesian network was used to analyse responses and develop a risk assessment based on expert opinion for brook trout at multiple scales within the province.  相似文献   

13.
Abstract –  We studied the impact of two exotic salmonid species (brook trout, Salvelinus fontinalis and rainbow trout, Oncorhynchus mykiss ) on native brown trout ( Salmo trutta fario ) habitat, growth and survival. Habitat selection and vertical distribution between young-of-the-year of the three species were examined in a stream aquarium under different sympatric and allopatric combinations. In addition, similar species combinations were introduced in a Pyrenean mountain stream (southwest France) in order to extend laboratory results to growth and apparent survival. Both laboratory and field results indicated that rainbow trout significantly affected native brown trout habitat selection and apparent survival. On the contrary, brown trout habitat, growth and apparent survival were hardly affected by brook trout. These results support the idea that rainbow trout negatively influence native brown trout, and that competition could influence the outcome of fish biological invasions in freshwater ecosystems.  相似文献   

14.
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15.
Dam removals allow fish to access habitats that may provide ecological benefits and risks, but the extent of fish movements through former dam sites has not been thoroughly evaluated for many species. We installed stationary PIT antennas in 2016 and 2017 to evaluate movements and survival of brook trout Salvelinus fontinalis in the West Branch of the Wolf River (WBWR) in central Wisconsin following removal of two dams and channel modifications designed to promote fish movement. These changes provided access to lacustrine habitats that might provide suitable winter habitat or act as ecological sinks. We used multistate models to estimate transition probabilities between river sections, to determine whether brook trout: (a) moved between multiple river sections and (b) entered lacustrine habitats as seasonal refuges, but eventually returned to lotic habitat. We also used a Cormack-Jolly-Seber model to evaluate whether apparent survival of brook trout in the WBWR was comparable to other populations. Few fish moved among river sections or used lacustrine habitat (<5% of tagged fish); most brook trout remained in sections where they were initially tagged, potentially due to quality habitat located throughout the river. Like other studies, brook trout in the WBWR appear to experience high mortality based on low number of detections, few physical recaptures and an estimated eight-month apparent survival rate of 0.27. In scenarios where fish can already access suitable habitat, removal of dams may not result in substantial increases in fish movement and colonisation of newly accessible habitat may not occur immediately.  相似文献   

16.
The early humoral responses of rainbow trout, Oncorhynchus mykiss (Walbaum), and brook trout, Salvelinus fontinalis (Mitchill), with sterile inflammation induced by intraperitoneal Lipogen Triple vaccination were compared to determine if genetic differences in susceptibility to furunculosis in salmonids correlated with different acute phase responses to vaccination. Similar severe acute sterile peritonitis occurred in response to Lipogen Triple in both species. Both species also had a rapid transient reduction in plasma iron concentration at 3 days. Moderate hypoferraemia persisted to day 14 in brook trout, but returned to normal by day 7 in rainbow trout. Plasma zinc decreased sharply 3 days after vaccination in rainbow trout and returned nearly to control levels by day 10; however, plasma zinc did not change in brook trout. Two-dimensional sodium dodecyl sulphate polyacrylamide electrophoresis of plasma proteins revealed that increased amounts of a 48-kDa protein group coincided with the hypoferraemic response in rainbow trout. In addition, a modest elevation in a 16-kDa protein group also occurred in rainbow trout. These studies demonstrated the rapid changes in plasma iron in both species and mild elevation of two putative acute phase plasma proteins associated with vaccine-induced inflammation in rainbow trout.  相似文献   

17.
Non‐native trout are currently stocked to support recreational fisheries in headwater streams throughout Nebraska. The influence of non‐native trout introductions on native fish populations and their role in structuring fish assemblages in these systems is unknown. The objectives of this study were to determine (i) if the size structure or relative abundance of native fish differs in the presence and absence of non‐native trout, (ii) if native fish‐assemblage structure differs in the presence and absence of non‐native trout and (iii) if native fish‐assemblage structure differs across a gradient in abundances of non‐native trout. Longnose dace Rhinichthys cataractae were larger in the presence of brown trout Salmo trutta and smaller in the presence of rainbow trout Oncorhynchus mykiss compared to sites without trout. There was also a greater proportion of larger white suckers Catostomus commersonii in the presence of brown trout. Creek chub Semotilus atromaculatus and fathead minnow Pimephales promelas size structures were similar in the presence and absence of trout. Relative abundances of longnose dace, white sucker, creek chub and fathead minnow were similar in the presence and absence of trout, but there was greater distinction in native fish‐assemblage structure between sites with trout compared to sites without trout as trout abundances increased. These results suggest increased risk to native fish assemblages in sites with high abundances of trout. However, more research is needed to determine the role of non‐native trout in structuring native fish assemblages in streams, and the mechanisms through which introduced trout may influence native fish populations.  相似文献   

18.
Abstract. Individual weighings of samples of brook trout, Salvelinus fontinalis Mitchill, and brown trout, Salmo trutta L., al the initiation and termination of their growth period, enabled estimating the association of weight gain on initial weight. In both cases the regressions were positive and the correlations significant. Variation in initial weight among tested individuals and groups is expected to bias growth estimates of these groups in programmes of genetic testing, as a result of this association. Obviating this bias requires an adequate correcting technique, involving the estimation of an environmentally generated correction factor. Phenotypic regression coefficients, as estimated in this investigation, cannot serve as correction factors, but may be regarded as maximum estimates.  相似文献   

19.
Abstract. These studies were done to determine the prevalence of infection, over time, of progeny from a population of 1988 year class brook trout, Salvelinus fontinalis (Mitchill), that was asymptomatically infected with Renibacterium salmoninarum , the causative agent of bacterial kidney disease. This population and its progeny from the 1991 and 1992 spawnings were monitored for approximately 3 years for prevalence of R. salmoninarum and development of bacterial kidney disease. Ovarian fluid samples from the 1991 and 1992 spawnings, and from a 1993 spawning of the 1991 progeny, were analysed for R. salmoninarum by enzyme linked immunosorbent assay (ELISA) and the membrane filtration fluorescent antibody technique. Kidney and spleen tissues of the 1988 year class were assayed by ELISA following the 1992 spawning. The progeny of the 1991 and 1992 spawnings were followed for increased prevalence of R. salmoninarum by the ELISA. Kidney tissues were assayed and sampling began once the fish were large enough. Each population of progeny was sampled quarterly for one year. Overall, the progeny displayed decreasing prevalence of R. salmoninarum and all ovarian fluids of the 1991 progeny (in 1993) were negative. Brood fish and progeny remained asymptomatic during the course of the study.  相似文献   

20.
Abstract – We examined the reproductive characteristics of 38 female longnose dace ( Rhinichthys cataractae ) from one of the southernmost populations of this species during two sampling periods in 1999 (ES=March 1999, LS=June 1999). Our data indicated that ES fish had not spawned, whereas LS fish had begun spawning. The smallest mature female captured was 56 mm SL (age 1+). Mean potential fecundity differed significantly between ES (mean±1 SD=1832±572 oocytes) and LS (mean±1 SD=775±415 oocytes) specimens. Potential fecundity was positively correlated with both standard length and somatic mass for both ES and LS specimens. Oocyte diameter frequency histograms indicated that ES specimens possessed two modes of oocytes, whereas LS fish contained two or three modes. Female longnose dace appeared to spawn more than once during a reproductive season. Oocyte number varied substantially both among individuals within periods and between periods. The number of Mode II oocytes in ES fish was positively correlated with both length and somatic mass. Female longnose dace appeared potentially capable of spawning 6+ clutches per year. GSI values for longnose dace ranged from a high of 21.4% (LS specimen) to 2.4% (ES specimen). Regression analysis demonstrated that there was no evidence of differential reproductive effort between longnose dace of different size in this population.  相似文献   

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