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 <4.5 respectively.     

In situ toxicity tests of fishes in acid waters

Toxicity of waters within the North Branch of the Moose River to various life stages of lake trout (Salvelinus namaycush), brook trout (Salvelinus fontinalis), creek chub (Semotilus atromaculatus), and blacknose dace (Rhinichthys atratulus) were examined in situ. Study sites were selected that were expected to range from toxic to favourable water quality. For example, pH varied from 4.25 to 7.17, inorganic monomeric Al ranged from ND (< 0.01 mg/l) to 0.40 mg/l, and Ca, from 0.41 to 4.27 mg/l.Toxicity tests were conducted at times when the life stages would naturally occur in these waters and were continued until a range of mortality was observed at the various sites. These experiments suggested that the extent of the drainage system that is toxic to fish increases during snowmelt and major runoff events. Summer base flow water quality was generally the least toxic.Critical life stages were upon hatching and as early feeding fry. In general, young of the year fish were the most tolerant life stage tested. Yearling and adult fish, however, were very sensitive. Blacknose dace were the most sensitive fish of the four species tested, and brook trout were the most tolerant.Hydrogen ion (H⁺) concentration was the most toxic variable in the majority of tests. Inorganic monomeric Al was the most toxic in several, and the combination of H⁺ and Al seemed to cause increased toxicity in many instances. A three-variable model employing hours of exposure, H⁺ concentration, and inorganic monomeric Al predicted mortality quite well. A simple two-variable model using H⁺ and color was nearly as good (R² from 0.49 to 0.94).Documented differences in toxicity among sites and species agreed with observed patterns of fish distribution. These in situ results indicated that laboratory estimates of safe levels of pH and concentrations of Al can result in mortality of fishes in surface waters subject to acidification.     

Brown trout and food web interactions in a Minnesota stream

1. We examined indirect, community‐level interactions in a stream that contained non‐native brown trout (Salmo trutta Linnaeus), native brook trout (Salvelinus fontinalis Mitchill) and native slimy sculpin (Cottus cognatus Richardson). Our objectives were to examine benthic invertebrate composition and prey selection of fishes (measured by total invertebrate dry mass, dry mass of individual invertebrate taxa and relative proportion of invertebrate taxa in the benthos and diet) among treatments (no fish, juvenile brook trout alone, juvenile brown trout alone, sculpin with brook trout and sculpin with brown trout). 2. We assigned treatments to 1 m² enclosures/exclosures placed in riffles in Valley Creek, Minnesota, and conducted six experimental trials. We used three designs of fish densities (addition of trout to a constant number of sculpin with unequal numbers of trout and sculpin; addition of trout to a constant number of sculpin with equal numbers of trout and sculpin; and replacement of half the sculpin with an equal number of trout) to investigate the relative strength of interspecific versus intraspecific interactions. 3. Presence of fish (all three species, alone or in combined‐species treatments) was not associated with changes in total dry mass of benthic invertebrates or shifts in relative abundance of benthic invertebrate taxa, regardless of fish density design. 4. Brook trout and sculpin diets did not change when each species was alone compared with treatments of both species together. Likewise, we did not find evidence for shifts in brown trout or sculpin diets when each species was alone or together. 5. We suggest that native brook trout and non‐native brown trout fill similar niches in Valley Creek. We did not find evidence that either species had an effect on stream communities, potentially due to high invertebrate productivity in Valley Creek.     

Cyprinid assemblages,and the physical and chemical characteristics of small northern Ontario lakes

Synopsis The cyprinid species, and physical and chemical characteristics were recorded from 58 small lakes in the Algoma district of northern Ontario. A group of typical stream-dwelling lithophilous species, which included common shiner, Notropis cornutus, creek chub, Semotilus atromaculatus, and blacknose dace, Rhinichthys atratulus, tended to occupy lakes of larger than average drainage areas. Phoxinus spp., pearl dace, Semotilus margarita, and fathead minnow, Pimephales promelas, occurred commonly in lakes with small drainage areas, and the average drainage area of lakes they occupied was near or below the overall average. Lakes without stream cyprinids were discriminated from lakes with them on a combination of chemical variables, including pH, alkalinity and calcium, which indicated that they were more susceptible to anthropogenic acidification.     

Deception Divergence and Sexual Selection

The hypothesis that blacknose dace Rhinichthys atratulus discriminate between piscivorous creek chub Semotilus atromaculatus and nonpiscivorous common suckers Catostomus commersoni was tested in a seminatural, artificial stream. Dace avoided the nonpredatory suckers less than they did the predatory chub, which they avoided during both day and night. However, dace significantly avoided the nonpredator at night. Further, experienced and inexperienced dace avoided the nonpredator similarly, suggesting that they had not learned to discriminate predator from nonpredator in their natural habitat. These results are consistent with two hypotheses (1) that individuals varied in ability to discriminate predatory from nonpredatory fishes, and (2) that the predator was more active than the nonpredator, thereby “frightening” the dace more. At temperatures of < 6°C the nonpredator was inactive and dace no longer avoided it at night, but continued to avoid the active chub, suggesting that movement constituted part of the avoidance-releasing stimulus. Because dace avoided nonpredators, they may waste time in natural streams avoiding harmless fish. It is suggested that the dace cannot afford the risk of a mistaken identity, which may be high in the stream environment, and selection favors those that avoid all large, moving fish.     

Diel activity patterns of the fish community in a temperate stream

The diel activity patterns of fishes in a temperate New Brunswick stream were studied during the summer over 5 years. Young‐of‐the year Atlantic salmon Salmo salar and blacknose dace Rhinichthys atratulus were more active during the day than at night, whereas lake chub Couesius plumbeus, brook trout Salvelinus fontinalis and adult white suckers Catostomus commersonii were more active at night than during the day. Because fishes were as likely to be nocturnal as diurnal, the data suggest that more night‐time sampling is needed to provide an unbiased view of fish community structure in temperate streams.     

Ontogenetic changes in diel activity,food habits and spatial distribution of juvenile and adult creek chub,Semotilus atromaculatus

Synopsis Juvenile creek chub, Semotilus atromaculatus, differed ecologically from adults. They were essentially diurnal, fed on small prey (adult diptera and aquatic adult coleoptera) and were found mainly in shallow littoral water (0.8 m depth) of a Québec oligotrophic lake. In contrast, adults were principally nocturnal, fed on larger prey (Gammaridae, diptera larvae, diptera pupae and ephemeroptera larvae) and were found in deeper water (1.2, 2.0 and 2.9 m depth). The overlap in diet between juvenile and adult fish was 10 percent. We found that predation by brook charr, Salvelinus fontinalis, upon creek chub was low, as only 5 chart stomachs of the 302 examined contained a total of 16 juvenile chub and none contained adult chub. Laboratory observations revealed that under low light intensity (0.17 lux) adult creek chub fed as efficiently as under high light intensity (22 lux). Several possible hypotheses to explain the evolution of the two different strategies exhibed by adult and juvenile creek chub are discussed.     

Urbanization drives contemporary evolution in stream fish

Human activities reduce biodiversity but may also drive diversification by modifying selection. Urbanization alters stream hydrology by increasing peak water velocities, which should in turn alter selection on the body morphology of aquatic species. Here, we show how urbanization can generate evolutionary divergence in the body morphology of two species of stream fish, western blacknose dace (Rhinichthys obtusus) and creek chub (Semotilus atromaculatus). We predicted that fish should evolve more streamlined body shapes within urbanized streams. We found that in urban streams, dace consistently exhibited more streamlined bodies while chub consistently showed deeper bodies. Comparing modern creek chub populations with historical museum collections spanning 50 years, we found that creek chub (1) rapidly became deeper bodied in streams that experienced increasing urbanization over time, (2) had already achieved deepened bodies 50 years ago in streams that were then already urban (and showed no additional deepening over time), and (3) remained relatively shallow bodied in streams that stayed rural over time. By raising creek chub from five populations under common conditions in the laboratory, we found that morphological differences largely reflected genetically based differences, not velocity–induced phenotypic plasticity. We suggest that urbanization can drive rapid, adaptive evolutionary responses to disturbance, and that these responses may vary unpredictably in different species.     

What predicts the use by brook trout (Salvelinus fontinalis) of terrestrial invertebrate subsidies in headwater streams?

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Diet and annual production of two boreal river fishes following clearcut logging

Synopsis Diet and annual production of two cyprinid fishes in the Piscataquis River, Maine, were investigated before and after extensive deforestation of the surrounding watershed. Observed patterns were evaluated relative to post-logging changes in the benthic macroinvertebrate community, and to differences in ecomorphology between the two fishes. Prey selection was generally density-dependent for both predator species throughout the study, but significant exceptions to density-dependence were observed for several aquatic insect lifemode groups (e.g., swimmers, climbers, burrowers). This apparent preference/avoidance for certain prey taxa by fish predators could be adequately explained by differential availability (vulnerability) among prey taxa. Compared to the year before logging, significant post-logging changes in diet composition and gut fullness were observed for both blacknose dace,Rhinichthys atratulus, and creek chub,Semotilus atromaculatus, concomitant with post-logging changes in the availability of benthic prey. Annual production of blacknose dace was significantly lower (52.7 vs. 37.7 kg ha^–1 y^–1) in the year following logging. In contrast, annual production of creek chub increased significantly after logging, from 8.6 to 17.4 kg ha^–1 y^–1. Because post-logging changes in the physical environment were probably not sufficient to directly affect fish populations, we hypothesize that blacknose dace were morphologically constrained to feed on a declining aquatic prey resource, with a resultant decline in production. In contrast, the generalist creek chub switched to a non-aquatic prey resource (terrestrial arthropods) and no decline in production was observed for that species.     

The influence of predatory fish on mayfly drift: extrapolating from experiments to nature

1. A knowledge of how individual behaviour affects populations in nature is needed to understand many ecologically important processes, such as the dispersal of larval insects in streams. The influence of chemical cues from drift‐feeding fish on the drift dispersal of mayflies has been documented in small experimental channels (i.e. < 3 m), but their influence on dispersal in natural systems (e.g. 30 m stream reaches) is unclear. 2. Using surveys in 10 Rocky Mountain streams in Western Colorado we examined whether the effects of predatory brook trout (Salvelinus fontinalis) on mayfly drift, that were apparent in stream‐side channels, could also be detected in natural streams. 3. In channel experiments, the drift of Baetis bicaudatus (Baetidae) was more responsive to variation in the concentration of chemical cues from brook trout than that of another mayfly, Epeorus deceptivus (Heptageniidae). The rate of brook trout predation on drifting mayflies of both species in a 2‐m long observation tank was higher during the day (60–75%) but still measurable at night (5–10%). Epeorus individuals released into the water column were more vulnerable to trout predation by both day and night than were Baetis larvae treated similarly. 4. Drift of all mayfly taxa in five fishless streams was aperiodic, whereas their drift was nocturnal in five trout streams. The propensity of mayflies to drift was decreased during the day and increased during the night in trout streams compared with fishless streams. In contrast to the channel experiments, fish biomass and density did not alter the nocturnal nature nor magnitude of mayfly drift in natural streams. 5. In combination, these results indicate that mayflies respond to subtle differences in concentration of fish cues in experimental channels. However, temporal and spatial variation in fish cues available to mayflies in natural streams may have obscured our ability to detect responses at larger scales.     

Food partitioning between coexisting Atlantic salmon and brook trout in the Sainte‐Marguerite River ecosystem, Quebec

Food resource partitioning between similar‐sized, sympatric Atlantic salmon Salmo salar and brook trout Salvelinus fontinalis was examined as a possible mechanism enabling their coexistence in a stream (Allaire) of the Sainte‐Marguerite River ecosystem, Quebec, Canada. Fish stomach contents and invertebrate drift were collected concurrently during three diel cycles in August to September 1996. The food and feeding habits of an allopatric brook trout population in a nearby stream (Epinette) were studied for comparison. The diel feeding rhythms of the two coexisting fish species were similar. The composition of their diet, however, showed significant differences. Atlantic salmon predominantly (60–90%) fed on aquatic insects, mainly Ephemeroptera (35–60% of the diet). The brook trout mostly (50–80%) fed upon the allochthonous terrestrial insects (mainly adults of Coleoptera, Hymenoptera and Diptera) which comprised 5–40% of the stream drift. The allopatric brook trout fed opportunistically on the more abundant aquatic insects and terrestrial insects rarely formed 25% of its diet. The allopatric trout fed nearly twice as much as the sympatric brook trout during a day. The results suggest that the differences in feeding by brook trout in the two streams (with and without Atlantic salmon) are the result of inter‐specific interaction with Atlantic salmon and are not related to the differences in food availability between the two streams. Food resource partitioning between Atlantic salmon and brook trout may be viewed as an adaptive response resulting in a greater exploitation of available resources and coexistence.     

Nested species subsets, gaps, and discrepancy

Chemical cues from fish can alter the behaviour of stream invertebrates in experimental tanks but their effect in natural streams has received little attention. By adding brook trout (Salvelinus fontinalis) odour to a trout stream in the Rocky Mountains of Colorado, USA, we tested whether changes in the concentration of chemical cues from visually feeding predatory fish would alter the drift of mayfly nymphs (Ephemeroptera). Stream water was piped from stream-side tanks with (odour) and without (control) three brook trout to two locations in the stream 3.5 m upstream of drift nets at six replicate sites. Five-minute drift samples were collected downstream from odour and control pipes before, during and after the release of water from the tanks into the stream during both the day and night. Almost all drift occurred at night and consisted predominantly of Baetis bicaudatus nymphs. The odour manipulation had no measurable effect on Baetis drift during the day but statistical power was low. During the night, however, the drift of large (>0.65 mm head capsule width, HCW) Baetis nymphs decreased significantly during the odour addition compared to control drift. In contrast, the drift of small nymphs (≤0.65 mm HCW) increased both during and after the odour addition in comparison to control drift. Since the stream contains brook trout (0.04–0.18 m⁻²), and water from the stream (presumably containing fish odour) altered the behaviour of fishless-stream Baetis nymphs in another experiment, we conclude that the changes in Baetis drift density were a response to an increase in the concentration of fish odour in the stream. Furthermore, we were able to detect the effect within 5 min. of odour addition, indicating that mayfly behavioural response to trout odour was rapid. These results suggest that mayflies can distinguish different concentrations of trout odour in natural streams and that the response is size-specific, according to the relative risk of predation of large and small Baetis. Received: 12 May 1998 / Accepted: 23 October 1998     

Seasonal and Diel Utilisation of Inshore Microhabitats by Larvae and Juveniles of Leuciscus Cephalus and Leuciscus Leuciscus

From July 1995 to January 1996, we examined the seasonal variations of the diel dynamics of habitat use by young-of-the-year cyprinid fishes (chub Leuciscus cephalus and dace L. leuciscus) in a lotic stream (River Ourthe, Southern Belgium). Inshore bays and neighbouring habitats (riparian shelters, entrance of the bay and shallow riffles) were sampled every three hours from 6:00 to 22:00 h, using DC electrofishing with prepositioned frames. In early summer, chub larvae moved exclusively in between the middle of the bay and riparian shelters inside the bay. Juvenile dace and, later in the season, juvenile chub showed diel dynamics of which the amplitude was dependent on temperature and illumination: they moved into the bay in the morning, gathered in greater numbers at mid-day (up to 586 chub and 387 dace m^-2), then progressively left the bay and entered neighbouring riffles in the late afternoon or evening. Small fish immigrated earlier into the bay and emigrated later than fish of larger size. By late September, most dace had left the bays, but returned there when water temperatures were <7°C. During autumn and winter, juvenile dace and chub of all sizes occupied exclusively inshore shelters with submerged riparian macrophytes or fallen tree leaves (corresponding densities of 0.7, 9.5 and 15.8 dace m^-2, and of 6.8, 20.2 and 94.2 chub m^-2). These results support the idea that young-of-the-year dace and chub shift from a restricted use of inshore shallow bays to a diel dynamics with alternate inshore-offshore movements at the time when they become juveniles, although the precise timings of these movements are still influenced by fish size and water temperature afterwards. The significance of these dynamics is discussed within a context of trade-off between the use of food resources and avoidance of predators.     

Importance of terrestrial subsidies for native brook trout in Appalachian intermittent streams

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Cytogenetic identification of genomic elements of brook trout (Salvelinus fontinalis) in the karyotype of Arctic char (Salvelinus alpinus) from the aquaculture broodstock

Growing interest of Arctic char (Salvelinus alpinus) aquaculture in Europe, and the fact that it can easily hybridize with brook trout (Salvelinus fontinalis) resulting in fertile progeny, led us to investigate fish from the farmed stocks. Chromosomes of sampled Arctic char were examined using conventional and molecular cytogenetic (FISH) techniques in order to determine possible contamination of genomic elements of brook trout. Investigated fish possessed karyotypes composed of 80–82 chromosomes and up to three chromosome fragments. Using staining methods and FISH approach enabled identification of the brook trout chromosomes in the eight out of twenty‐two examined Arctic char. Specific location of AT‐, GC‐ positive and NOR sites observed on chromosomes as well as chromosome fragments in the karyotypes of several individuals points on past chromosomal rearrangements in fish from examined broodstock. Based on our results, it may be assumed that individuals with the brook trout genomic elements, although phenotypically identified as Arctic chars, were hybrids. Our results highlights that special care should be taken to protect gene pools of brook trout and Arctic char in farms where both species are cultured.     

Difference in response by two cyprinid species to predatory threat from the nocturnal catfish Silurus asotus

Response to predators may not be identical between different prey species with different life histories and body sizes, particularly when the threat of predation is not great. To clarify this hypothesis, we introduced two prey species (10 Japanese dace, Tribolodon hakonensis, and 10 pale chub, Zacco platypus) into each experimental pond (in total, 8 ponds×4 trials) in which benthic algae had been allowed to grow. The presence or absence of Far Eastern catfish, Silurus asotus, and a refuge for prey fish was used to produce four treatments. The presence of catfish and/or a refuge did not affect either the feeding behavior or growth rate of Japanese dace. In contrast, when catfish were present and no refuge was available, the incidence of bottom feeding for pale chub greatly decreased. Pale chub growth rate was low when catfish were present and a refuge was available, indicating that pale chub spent more of their time in the refuge and lost opportunities of acquiring food. Japanese dace can reach a threshold size at which the prey are safe from predation, but pale chub cannot, and this may explain the differences in response to predators of the two species.     

Genetic variation,inheritance, and quaternary structure of malic enzyme in brook trout (Salvelinus fontinalis)

Electrophoretic variation is described for malic enzyme (ME) for the first time in brook trout (Salvelinus fontinalis). Since the quaternary structure of ME was not clear from examination of banding patterns in brook trout alone, ME phenotypes in rainbow trout (Salmo gairdneri) × brook trout hybrids as well as in esocid species demonstrated that ME is tetrameric. A model of two duplicated loci is proposed to account for the observed variation. One locus (ME-2) is fixed and one locus (ME-1) is variable with three electrophoretically distinct alleles; the protein products of ME-1 are reduced in activity relative to the protein products of ME-2. Joint segregation was examined between ME-1 and ten other biochemical loci in brook trout, and between ME-1, ME-2, and nine other biochemical loci in a splake—lake trout (Salvelinus namaycush) × brook trout hybrid—backcross. All pairwise examinations showed random assortment except ME-2 with an isocitrate dehydrogenase locus (IDH-3), which showed complete linkage in the splake backcross. This may be due to a chromosomal aberration.Authorized for publication as Paper No. 5599 in the Journal Series of The Pennsylvania Agricultural Experiment Station, University Park, Pennsylvania, in cooperation with the Benner Spring Fish Research Station, The Pennsylvania Fish Commission, Bellefonte, Pennsylvania. M.S. was supported by an NSF Graduate Fellowship.     

Seasonal movements and residency of small-bodied fish in a north temperate urban watershed demonstrate connectivity between a stream and stormwater drain

Despite their often physical connection, neighbouring stormwater drains and urban streams are typically managed quite differently; with drains mostly regarded as poor fish habitat. The goal of this study was to evaluate the interconnectedness of an urban stream (Watts Creek) and adjoining earthen surface stormwater drain (Kizell Drain) from the perspective of fish residency and movements over an entire year. Using a stationary passive integrated transponder (PIT) array, we quantified and compared the direction of movements among Watts Creek, Kizell Drain, and the area downstream of their confluence (herein termed Main) for four common stream fishes. We also determined the residency time (percentage of total time in days) within each of these reaches by combining data from the array and recaptured (with electrofishing and identified with hand-held PIT reader) or portably detected (with mobile PIT reader) fish. While the movements of creek chub (Semotilus atromaculatus) and central mudminnow (Umbra limi) varied across seasons, creek chub resided significantly longer in Watts, while central mudminnow spent more time in Kizell and Main. Longnose dace (Rhinichthys cataractae) moved into and resided most often within Watts. The movements and residency time for white sucker (Catostomus commersonii) did not vary among the reaches. We conclude there is a high degree of connectivity between Watts Creek and Kizell Drain and that, with the exception of longnose dace, the three other species utilize the habitat available in Kizell. This study demonstrates the biological potential of earthen stormwater drains and as a result we recommend these systems be managed as a functional component of urban watersheds.     

Fish-Community Response To Protective Liming in Thrush Lake, Minnesota

A protective limestone treatment was applied to an acid-sensitive lake in northeastern Minnesota as part of the Acid Precipitation Mitigation Program. This 6–year study evaluated the impact of that treatment on lakes in the upper Midwest that experience episodes of acid stress but have not lost basic species integrity and community structure. Several changes in the fish community can be directly or indirectly attributed to the addition of 4.6 tonnes of calcium carbonate early in the third year of the study. An almost 30–fold increase in the population of Pimephales promelas(fathead minnow) a year after liming, based on mark-recapture estimates from trap netting and snorkeling, was attributed to a pH increase and a three-fold increase in the calcium concentration of the epilimnion. After the initial increase, the abundance of fathead minnows declined in subsequent years, as did the elevated pH and calcium concentrations. The Salvelimis fontinalis(brook trout) population also increased in the lake following application of limestone, but this was due in part to closing the lake to fishing. An increase in survival of stocked brook trout to age 1+ and an increase in growth of older brook trout after liming were attributed to the increased forage that the fathead minnows provided. Fathead minnows may have also reduced predation pressure on young brook trout by older brook trout. This study demonstrated that liming of a slightly acidic lake did not adversely affect the integrity of the fish community, and in fact may have increased the abundance and biomass of the forage fish community and indirectly increased the survival, abundance, and growth of brook trout.