Fontinalis Mitchill Research Articles

Behavioural diversification in brook charr: adaptive responses to local conditions

Summary Recently emerged brook charr (Salvelinus fontinalis Mitchill) foraging in still‐water pools along the sides of streams exhibit conspicuous variation in foraging behaviour. Some charr are sedentary and eat crustaceans from the lower portion of the water column. Others are mobile and eat insects from the upper portion of the water column. This study examines whether this behavioural diversification represents potentially adaptive responses made by individuals to local environmental conditions. Four models were constructed to predict how the ratio of mobile to sedentary charr was expected to change with pool morphometry, and how the location and orientation of mobile and sedentary charr were expected to differ within pools. The models assumed the charr forage competitively, but each model differed in assumptions regarding which features of pool morphometry determine the availability of the two main prey types. A spatial constraint hypothesis also was considered. Findings from this study support the hypothesis that the divergent foraging tactics represent adaptive adjustments made by individual charr in response to competition for spatially separated food sources. Variation in the numbers of sedentary and mobile charr across pools, and spatial distributions of the charr and their crustacean and insect prey within pools, were most consistent with a model assuming that the availability of insect prey, and hence the number of mobile charr, was determined by the pool surface area while the availability of crustacean prey, and hence the number of sedentary charr, was determined by the pool perimeter. Parallels between this pool system and polymorphic fish populations in larger lake systems identifies a potential link between the adaptive decision making of individuals and the spatial and phenotypic divergence of populations in response to spatial heterogeneity in food resources.

FRESHWATER FISHES OF ACADIA NATIONAL PARK, MOUNT DESERT ISLAND, MAINE

A list of freshwater fishes is presented for Acadia National Park, Mount Desert Island, Maine, based on past survey records, published and unpublished reports, and recent comprehensive surveys within or bordering Park boundaries conducted in 1998 and 1999. Overall, 31 species of fishes have been recorded in freshwaters of the Park or those bordering Park boundaries; 28 of these are still present. Of those, 15 species are likely native to Mount Desert Island, and the indigenous status of one fish species is unknown. The most widely distributed species in lakes and ponds is the golden shiner, Notemigonus crysoleucas Mitchill (83% of ponds), while the most widely-distributed species in brooks is the brook trout, Salvelinus fontinalis Mitchill (56%).

The parasite fauna of brook trout, Salvelinus fontinalis (Mitchill), in relation to lake morphometrics and the introduction of creek chub, Semotilus atromaculatus (Mitchill)

:Creek chub, Semotilus atromaculatus (Mitchill), has been introduced in several brook trout, Salvelinus fontinalis (Mitchill), lakes of the Laurentian Shield, Québec, Canada. The objectives of this study were to determine (i) if creek chub parasites colonized the lakes of the Laurentian Shield, (ii) if parasites were exchanged between the two fish species, (iii) the effect of the diet shift of brook trout in the presence of creek chub on its parasite fauna, and (iv) the importance of lake mean depth as a factor responsible for parasite community structure in brook trout. Eleven parasite species were identified from creek chub and fourteen from brook trout. Eight of the eleven parasite species found in creek chub colonized the lakes with creek chub. Two creek chub parasite species were exchanged with brook trout and two brook trout parasite species were exchanged with creek chub. The mean number of brook trout parasites acquired by feeding on benthic intermediate hosts was significantly higher in allopatric brook trout populations than in sympatric creek chub and brook trout populations. Larval stages of most parasite species occurred in low abundance or were absent from brook trout found in deep lakes, indicating that bird and mammal definitive hosts were not common in those lakes. A cluster analysis also showed that lakes with similar fish communities tended to clump together, suggesting that fish community structure clearly influences parasite community structure in brook trout. Brook trout parasite community structure was affected by parasite exchange, by diet shift of brook trout when living in sympatry with creek chub and by inter-lake variation due to depth and other factors.

Enchanted Pond's Resident White Suckers

During a September 1995 gill netting survey conducted on Enchanted Pond, a deep oligotrophic lake located in Somerset County, Maine, a sample of 228 white suckers (Catostomus commersoni Lacepede) was captured. All the fish were relatively small (between 45 and 247 mm). Other surveys on Enchanted Pond between 1979 and 1994 captured 81 white suckers, all less than 270 mm in length. It seemed likely that the white sucker population in Enchanted Pond was comprised of either stunted individuals, or of dwarf or pygmy forms. Stunting is caused by competition for limited food resources when a species is at high densities. When fish densities become very large, individual fish growth tends to lag and the size distribution of the population is uniform and relatively small compared to other populations in the region. If the density of a stunted population is reduced the fish grow normally. Dwarf or pygmy forms of a species are genetically distinct from normal forms and represent a diversi? fication in life-history often related to trophic ecology (Taylor and Bentzen 1993). Fish in these populations are also small relative to other populations in the region, however, individuals are not capable of normal growth. Enchanted Pond has a surface area of 133.5 hectares, a maximum depth of 56 meters, and a mean depth of 21m. Fish currently inhabiting En? chanted Pond include white sucker, brook trout (Salvelinus fontinalis Mitchill), lake chub (Couesius plumbeus Agassiz), and blacknose dace (Rhinichthys atratulus Hermann) (Anonymous 1979). Artie charr {Salvelinus alpinus oquassa L.) were introduced in 1991. The gill net survey used nylon and monofilament nets with meshes ranging from 16 to 64 mm stretch measure, 2m high and either 60m or 120m long. The nets were set on bottom from 24m to 56m deep and fished for five to twenty hours. Of the 228 white suckers captured, 50 fish were randomly selected and extended total length was recorded. Sex and maturity were recorded for six of these fish. Saccular otoliths, right pectoral fins, and scales were removed from an additional 20 randomly selected fish and placed in paper envelopes to dry. Length, weight, sex, and maturity were recorded on the envelopes. After comparing annuli on the three structures, pectoral fin rays were chosen as the hard structure to be used in determining age (Fig. 1). Beamish (1973), Beamish and Harvey (1969), and Quinn and Ross (1982) found fin rays to be the most reliable structure for aging suckers. Fish were aged according to methods similar to those described by Scidmore and Glass (1953). Direct age validation and confirmation of true annulus

Influences of Predatory Fish on the Drift Dispersal and Local Density of Stream Insects

Researchers have recently suggested that frequent prey dispersal into and out of an area can swamp the local effect on predation. Where prey are mobile, the extent of prey movement can therefore explain variation in the apparent effect of predators on local prey density. I compared the effect of the dominant predator in a temperate stream (brook charr, Salvelinus fontinalis Mitchill) on five insect prey taxa (mayflies: Ephemeroptera), to test the prediction that the extinct of density reduction should be less for prey taxa dispersing more frequently. The propensity of the mayflies to disperse by drifting downstream in the water column was measured in unmanipulated areas of the stream. Relative propensity to drift of the five mayflies was, from greatest to least: Baetis, Paraleptophlebia, Ephemerella, Eurylophella, Stenonema. I then tested effects of charr on the mayflies by manipulating charr density in fenced 35—m sections of the stream. Charr densities were adjusted to zero, medium, and high levels relative to natural densities. Rates of predation by charr in stream sections did not vary among the five mayfly taxa. Charr caused a large reduction in the density of Baetis, had a smaller effect on Paraleptophlebia, but had no detectable effect on the density of the other mayflies. Drift dispersal into the stream sections did not differ among charr densities. Effects of charr on prey densities could thus have been caused by direct predation or by increases in emigration from areas containing charr. Charr caused increased drift dispersal of Baetis and of Paraleptophlebia, but had no influence on drift of the other three mayflies. The reduction in density of Baetis by charr was due more to the charr—induced increase in drifting of Baetis than to direct predation on Baetis. The hypothesis that frequent prey dispersal swamps the effects of predators assumes that predators influence prey density primarily by consuming prey. In this system charr also influenced prey densities by causing increases in prey drift rates, affecting the mayflies that drifted most frequently. For this reason, the mayflies drifting less frequently were not, as predicted, the ones most strongly affected by charr. Variation in the effect of predators on prey density may thus be partially explained by both (1) changes in prey dispersal not related to predators, as proposed in the initial hypothesis, and (2) influences of predators on prey dispersal.

Cortisol, glucose and hematocrit changes during acute stress, cohort sampling, and the diel cycle in diploid and triploid brook trout (Salvelinus fontinalis Mitchill)

In this study, groups of diploid (control) and triploid brook trout were subjected to a 5 min acute handling/confinement stress. Blood samples were collected from equal numbers of diploid and triploid fish at regular predetermined intervals, beginning prior to confinement and continuing for up to 3h after confinement. These blood samples were used for the measurement of hematocrit and plasma cortisol and glucose concentrations. The effects of cohort sampling and the diel cycle on these variables were also analysed. Except for minor differences, both groups responded similarly to the acute stress, with short-term elevations in plasma cortisol and hematocrit levels, and a more sustained increase in plasma glucose levels. No significant differences were found between diploid and triploid fish in their reactions to cohort sampling. However, the act of removing an individual from a tank caused significant changes in plasma cortisol levels in cohorts remaining in that tank (p < 0.001). Significant diel effects were observed for both ploidy groups in plasma cortisol (p < 0.05) but not in plasma glucose or hematocrit.

Congruence in Control-Region Sequence and Restriction-Site Variation in Mitochondrial DNA of Brook Charr (Salvelinus Fontinalis Mitchill)

We compared the congruence in genetic variation and phylogenetic relationships among mitochondrial DNA (mtDNA) haplotypes detected with restriction-fragment-length polymorphisms (RFLPs) and sequence analysis in the brook charr, Sulvelinus fontinalis Mitchill. This was accomplished by analyzing variation both at 172 restriction sites subsampling 903 bp over the entire mitochondrial genome and in the sequence of a 300-bp segment of the control region among the same 33 individuals. The sequence and RFLP analyses were highly congruent both in terms of mtDNA variants detected per number of nucleotides sampled and in assessing phylogenetic relationships among haplotypes. Therefore, variation observed in a small segment of the control region was representative of that existing over the entire genome. The major difference between both approaches was in the number of mutational changes observed per nucleotide in the sequence analysis. This number was approximately twice as high as that in the RFLP analysis. Nevertheless, the level of variation observed in the control region of charr was less than expected a priori on the basis of previous observations in other vertebrates. Lower mutation rates may be related to an unusually low transition : transversion ratio ( 8 : 3 ) for mtDNA intraspecific variation in vertebrates. The combined restriction-site and sequence data resolved at least three distinct phylogenetic groupings in S. fontinalis. However, and despite the high-resolution level of the study (> 1,200 bp screened, or 7% of the mitochondrial genome), some major branching patterns in gene tree topology remained unresolved, which stresses the importance of recognizing large standard errors associated with sequence variability when phylogeny is reconstructed.

Exploration and rehabilitation of hydraulic habitats in streams using principles of fluvial behaviour

SUMMARY The combination of elements from geomorphology, open‐channel hydraulics, and hydraulic habitat requirements of stream fish forms the basis for an ecologically sound ‘soft engineering’ of river channels. Interpreting and mapping the hydraulic geometry of streams and locally varied flow conditions can be accomplished with plane table surveys and customized field‐data sheets. This information can serve to manage hydraulic habitats preferred by fish. The use of fluvial characteristics to design preferred hydraulic habitats is illustrated in two examples: (i) a walleye (Stizostedion vitreum vitreum Mitchill) spawning rehabilitation project undertaken in a stream channelized as a lowland drainage canal, and (ii) a trout (Salvelinus fontinalis Mitchill and Oncorhynchus mykiss Walbaum) habitat‐enhancement project to create additional holding and resting areas for adult fish in a stream paved with glacially deposited boulders modified by a road crossing. In both examples the ‘soft engineering’ of the river channels enhanced the hydraulic fish habitat.

Association between initial weight and weight gain in brook trout, Salvelinus fontinalis Mitchill, and brown trout, Salmo trutta L.

. 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.

Description of myxosporean presporogonic phases in the kidney of brook trout, Salvelinus fontinalis(Mitchill), in Nova Scotia, Canada

Description of myxosporean presporogonic phases in the kidney of brook trout, Salvelinus fontinalis(Mitchill), in Nova Scotia, Canada

Fish species associations in riffle habitat of streams of varying size and acidity in New Brunswick and Nova Scotia

Factors related to stream size and alkalinity were most influential in determining fish species associations in three catchments of New Brunswick (NB) and Nova Scotia (NS) Canada, as determined by discriminant function analysis of TWINSPAN stream site classification.In the circumneutral Saint Croix (NB) catchment, the creek chub, Semotilus atromaculatus (Mitchill), brook trout, Salvelinus fontinalis (Mitchill), blacknose dace, Rhinichthys atratulus (Hermann), Atlantic salmon, Salmo salar Linnaeus, eel, Anguilla rostrata (Lesueur) and fallfish. Semotilus corporalis (Mitchill) dominated stream sites of progressively greater discharge and higher median mid‐summer temperature. In the acidic Gold (NS) system, the brook trout, Atlantic salmon, and eel exhibited a distribution pattern in relation to stream size and temperature similar to that for the Saint Croix, with the eel relatively more abundant in the Gold at large stream sites. The creek chub was excluded from the smallest tributaries by low pH. The ranges of blacknose dace and fallfish do not extend to southwestern Nova Scotia. In the Medway (NS) system (slightly more acidic than the Gold), the relative abundance of Atlantic salmon is reduced, and that of eel increased as compared with the Gold and Saint Croix systems. The lower limiting mid‐summer pH levels for creek chub, salmon, brook trout, and eel are 5.2, 5.0, 4.7 and &lt;4.5 respectively.

Diel onshore–offshore migrations in northern redbelly dace, Phoxinus eos (Cope), in relation to prey distribution in a small oligotrophic lake

Northern redbelly dace, Phoxinus eos (Cope), exhibit diel onshore–offshore migrations in a small oligotrophic Quebec lake. The fish swim in shoals in the littoral zone during the day, migrate to the pelagic zone at sunset, where the shoals break up into single fish, and then go back to the littoral zone at sunrise. Dace eat mainly two cladocerans, Daphnia and Holopedium. Zooplankton sampling indicated that Daphnia were significantly more abundant in the pelagic zone than in the littoral zone, and Holopedium were rarely found in the littoral zone. Dace showed a significant preference for a dense cover habitat over a sparse cover habitat in the littoral zone during the day. Our results support the hypothesis that dace migrate to the pelagic zone at sunset to increase their feeding efficiency on zooplankton. The foraging benefits of remaining in the offshore zone may be offset by increased risk of predation by brook charr, Salvelinus fontinalis (Mitchill), during the daylight hours, thus resulting in diel onshore–offshore migrations.

Phyllodistomum umblae (Fabricius) (Digenea, Gorgoderidae) from British Columbia salmonids: a description based on light and scanning electron microscopy

Specimens of Phyllodistomum umblae (Fabricius, 1780) from Oncorhynchus nerka (Walbaum) from the Nautley River, British Columbia, and Salmo gairdneri Richardson from the Stuart River, British Columbia, are described and figured using light microscopy and scanning electron microscopy. Particular emphasis is placed on describing the numbers, types, and arrangement of papillae as seen with scanning electron microscopy. No significant differences were observed between the present Canadian material from O. nerka and S. gairdneri and specimens of P. umblae described from Norway, Sweden, and the U.S.S.R. Thus, P. umblae has a holarctic distribution in salmonids. Phyllodistomum limnosa Sandeman and Pippy, 1967, described from Salmo salar L. and Salvelinus fontinalis (Mitchill) from Newfoundland, is regarded as a synonym of P. umblae. Phyllodistomum lachancei Choquztte, 1947, described from S. fontinalis in Quebec, probably is also a synonym of P. umblae, but a more detailed scanning electron microscope study of the papillae in P. lachancei is required for confirmation.

The effect of locomotor activity on the growth of brook charr, Salvelinus fontinalis Mitchill

Yearling hatchery-reared brook charr, Salvelinus fontinalis Mitchill, were trained during a 20-day period at different water velocities: 0.00, 0.85, 1.72, and 2.50 body lengths/s (bl/s). Our results indicate that growth (wet weight), food conversion efficiency, and the deposition of lipids on the digestive tract were maximized at 0.85 bl/s. The individual growth (wet weight) was also more homogeneous at this water speed. The storage of lipids in the white muscles was significantly lower in still water (0.00 bl/s) while the increase in length, the increase in the dry weight of the carcass (whole fish less internal organs), and the relative water content of the muscle showed no significant differences between the tested water velocities. Behavioural observations indicated that the frequency of agonistic behaviours between individuals was important in still water, but decreased significantly in the presence of a water current.

Neutralization of acidic brook-water using a shell-sand filter or sea-water: Effects on eggs, alevins and smolts of salmonids

A shell-sand filter and additions of sea-water were used to neutralize acidic brook-water used for culturing Atlantic salmon ( Salmo salar L.), Arctic char ( Salvelinus alpinus L.) and brook trout ( Salvelinus fontinalis Mitchill). Passage of the acidic water through the shell-sand filter increased the pH from 4.8–5.3 to 6.4–7.4; addition of 3% (v/v) sea-water (32‰) increased the pH to 5.6–6.4. The pH levels resulting from the sea-water additions were less stable than those obtained with the shell-sand filter. The sea-water additions reduced the concentrations of labile aluminium in the hatchery channels by 0–50%. Passage through the shell-sand filter generally resulted in even greater reductions in labile aluminium, as expected from the higher pH. Cumulative mortalities through to the end of the alevin stage in untreated brook-water were 23, 40 and 25% for salmon, char and brook trout respectively. Sea-water additions reduced the mortality rate to 1, 15 and 10%, whereas passage through the shell-sand filter reduced it to 1, 6 and 9%, for salmon, char and brook trout respectively. Treated water from the channel outlets was led into small fish tanks containing Atlantic salmon smolts. The mortality rate was 100% after 6 days in the acidic brook-water whereas no smolts died in the shell-sand filter and sea-water treated water. During this experiment, the mortality rate of alevins was low (1%), illustrating the higher sensitivity of salmon smolts compared with the younger life stages.

Mechanisms responsible for the niche shift of brook charr, Salvelinus fontinalis Mitchill, when living sympatrically with creek chub, Semotilus atromaculatus Mitchill

When brook charr, Salvelinus fontinalis Mitchill, are in allopatry in oligotrophic Québec lakes, they feed largely on macrobenthic invertebrates. However, when brook charr cooccur with creek chub, Semotilus atromaculatus Mitchill, they feed largely on zooplankton. In the present study, laboratory experiments showed that creek chub were more effective than brook charr in searching for hidden, patchily distributed prey. The searching efficiency of an individual chub feeding in a group was improved through social facilitation. In contrast, the high level of intraspecific aggression observed in brook charr prevents the formation of such feeding groups. In the laboratory, brook charr were able to displace creek chub from the food source because of interspecific aggression. Data are presented showing that chub are morphologically better adapted than charr to feed on benthos (subterminal orientation of the mouth and protrusible premaxillae), while the charr are better adapted than chub to feed on zooplankton (gill raker structure). Differences in feeding behaviour, morphology, and relative abundance between these species appear to be important in the observed niche shift of brook charr in nature.

Exercise training in skeletal muscle of brook trout (Salvelinus fontinalis).

1. The differentiation of myotomal muscles in the brook trout (Salvelinus fontinalis Mitchill) has been investigated using p-phenylene diamine stained semi-thin sections and cytochemical and quantitative determinations of enzyme activities. 2. Evidence is presented that the range of fibre size in white muscle represents stages in growth rather than distinct fibre types. 3. Electromyography shows that both red and white muscles are recruited for sustained swimming. The threshold swimming speed for recruitment of white fibres is around 1.8 body length/s (L/s). 4. White muscle citrate synthetase and cytochorome oxidase activities are 25-35% that of red muscle. Hexokinase, phosphorylase and phosphofructokinase activities are 2, 4 and 2 times higher in white than red muscles. It is considered that the aerobic capacity of white muscle is sufficient to support sustained swimming, and that blood glucose could be an important fuel source. 5. Endurance exercise training has been investigated in fish swimming, continuously, for 21 days at 3 L/s. This training regime restricts spontaneous high-speed swimming activity and resulted in a general decline of white muscle glycolytic enzyme activities. Red fibres underwent hypertrophy relative to non-exercised controls (530 +/- 64 microns2 non-exercised, 901 +/- 63 microns2 trained). Aerobic enzyme activities in red muscle and the fraction of fibre volume occupied by mitochondria (30.2 +/- 0.8%) did not change in response to the training programme, but glycolytic enzyme activities were elevated. 3-OH Acyl CoA dehydrogenase activities increased in both red and white muscles indicating an enhanced capacity for fatty acid catabolism with training. 6. Plasma and muscle lactate levels were not statistically different between tank-rested and trained fish swimming a 3 L/s. 7. Adaptations of fish muscle to endurance training are discussed and compared with results for other vertebrates.

Blood Acid-Base Balance in Brook Trout (Salvelinus Fontinalis)*

ABSTRACT A nomogram is presented which allows the rapid assessment of acid-base status in brook trout (Salvelinus fontinalis Mitchill) at 18°C. Due to a of 3·5–4·3 mmHg in the respirometer water, the fish from which data were obtained for determination of zero base excess values were suffering from slight respiratory acidosis. Trauma of surgery and anaesthetization as well as confinement in the respirometer might also have generated a slight metabolic acidosis. Base excess values for trout with a chronically implanted dorsal aortic cannula ranged from −3 to + 3m-equiv/l. Blood buffer values of d[HCO3−]/dpH = 7·50±4·42 slykes and were found. Mean plasma protein concentration was 3·6± 0·8 g/100 ml plasma and the buffering power of plasma was approximately 40% that of whole blood. Plasma proteins are more important blood buffers in fish than in humans.

Acid-Base Balance and Gas Exchange in Brook Trout (Salvelinus Fontinalis) Exposed to Acidic Environments

ABSTRACT Brook trout (Salvelinus fontinalis Mitchill) with a chronically implanted dorsal aortic cannula were exposed to acidic environments. During exposure, trout developed severe metabolic acidosis as shown by decreases in standard plasma bicarbonate levels as well as negative base excess values. Reduced oxygen consumption seen in acidotic trout resulted from decreased gill oxygen transfer and reduced available blood oxygen capacity.

Relative tolerance of some salmonids to acid waters

Experiments have been performed to study the tolerance of different species of salmonids to acid waters (pH 4.4–5.5). Brown trout (Salmo trutta L.), brook trout (Sahelinus fontinalis Mitchill), rai...