Clinostomus Funduloides Research Articles

Thermal tolerance of cyprinids along an urban-rural gradient: Plasticity, repeatability and effects of swimming and temperature shock.

Urbanization changes the thermal profile of streams in much the same way that climate change is predicted to with higher temperatures, more varied flow and rapid temperature pulses with precipitation events. Whether exceptional tolerance to these altered thermal conditions is a pre-requisite for a fish species to inhabit urban streams or if urbanization has changed the thermal physiology of those fish species that persist in urban streams is unknown, but could help predict the outcome of future climate disruption. To test whether residence in urban streams is associated with altered thermal tolerance, we compared thermal tolerance (CTMax) and phenotypic plasticity of thermal tolerance (ΔCTMax/Δ acclimation temperature) in five populations of an urban-tolerant cyprinid, the blacknose dace (Rhinichthys atratulus), from multiple watersheds along an urban/rural gradient. Thermal tolerance of these stream fish was tested while swimming at 10cm*s-1 but also in static water and after thermal shocks of 4°-6°C simulating precipitation events. To test whether blacknose dace as a species has unusual thermal tolerance or thermal plasticity, we also compared two blacknose dace populations with two co-resident, co-familiars (creek chub (Semotilus atromaculatus) and rosyside dace (Clinostomus funduloides), that don't persist in urban streams at three different acclimation temperatures. Thermal tolerance of blacknose dace, as measured by a critical thermal maximum test (CTMax), was independent of size and activity level, i.e. individuals had identical thermal tolerance whether swimming or resting and CTMax was significantly repeatable across two levels of activity. Although there was some variance among populations, blacknose dace from streams of varied urbanization generally exhibited comparable thermal tolerances, ability to acclimate to different temperatures and were unaffected by thermal shocks. Rosyside dace had significantly lower thermal tolerance than the other two species but plasticity of thermal tolerance was uniform across the three cyprinid species. Our conclusions are that exceptional thermal tolerance or ability to thermally acclimate are not pre-requisite characters for a given cyprinid species to survive in urban streams, nor has thermal tolerance undergone directional selection in this urban environment.

DNA Barcoding Elucidates Cyprinid Reproductive Interactions in a Southwest Virginia Stream

AbstractChubs Nocomis spp. (Cyprinidae) in freshwater streams build conspicuous gravel mounds upon which they and other nest‐associative cyprinids spawn. Our understanding of such interactions is incomplete and hindered by the inability to observe all interactions directly and to identify the larvae that emerge from the mounds based on morphological traits. We used visual surveys and DNA barcoding to identify cyprinids that were associated with the nests of spawning chub in Catawba Creek, a small tributary of the James River in southwestern Virginia. All individual fish on nests were identified to species and categorized as spawning or feeding. Eggs were subsequently removed from the nests and hatched in captivity, and DNA was extracted from the larvae. The DNA sequences for region 3 of the mitochondrial cytochrome‐c oxidase I gene in individual larvae were amplified, and the resulting sequences were compared to entries in GenBank by using the Basic Local Alignment Search Tool for nucleotide data. Of the 75 larval fish that were assayed, 56 (75%) were genetically identified. Species‐level identification of the larval cyprinids was straightforward except with regard to Nocomis, for which cryptic taxonomy is currently unresolved. Four cyprinid species were identified among the larvae sampled from Nocomis nests; of those species, the Central Stoneroller Campostoma anomalum and Rosyside Dace Clinostomus funduloides had not been previously witnessed to spawn on chub nests. Central Stonerollers had been observed to perform activities that were more indicative of nest predation than spawning; hence, the presence of their eggs on Nocomis nests suggests that the activity of Central Stonerollers is not entirely antagonistic.Received June 2, 2016; accepted September 19, 2016 Published online December 2, 2016

Long‐term persistence, density dependence and effects of climate change on rosyside dace (Cyprinidae)

SummaryWe used long‐term population data for rosyside dace (Clinostomus funduloides), a numerically dominant member of a stochastically organised fish assemblage, to evaluate the relative importance of density‐dependent and density‐independent processes to population persistence.We also evaluated the potential impacts of global climate change (GCC) on this species and predicted how directional environmental changes will affect dace.We sampled two 30 m permanent sites in spring and autumn in the Coweeta catchment for rosyside dace density using three‐pass electrofishing between 1984 and 1995, and a single 100 m site from 1991 to 2003.Habitat availability and flow variation data for this 20‐year period demonstrated that two droughts (1985–1988 and 1999–2002) produced smaller wetted areas, lower mean, maximum and minimum flows, fewer high flow events and greater amounts of depositional substrata in the sites.Droughts produced significant increases in abundance, and significant decreases in standard length and mass of rosyside dace. Increases in abundance were mainly due to increased survival/immigration of young‐of‐the‐year (YOY).Model selection analysis using multiple single and multivariable models indicated that density dependence in various forms possessed substantial explanatory power with respect to long‐term variation in the per‐capita rate of increase (r) in all sites and seasons. Density‐dependent effects onrwere stronger in autumn than spring, whereas negative density‐independent models (flow variation) had the greatest explanatory power in spring.Results for growth data were similar to those for rosyside dace density and confirm density dependence likely through intraspecific competition for food or foraging sites leading to reduced growth at higher densities.These data support the hypothesis that species may persist in stochastic animal assemblages via strong intraspecific density dependence. Greater flow variability or increased high flows produced by GCC may destabilise this population leading to reduced compensation and possibly eventual extinction.

Biotic interactions and habitat drive positive co‐occurrence between facilitating and beneficiary stream fishes

AbstractAimThe role of biotic interactions in determining species distributions is difficult to decouple from abiotic factors. Most research to date has focused on negative biotic interactions, but the importance of positive interactions such as mutualism and facilitation at large scales is less understood. We used a two‐species occupancy modelling approach to decouple the relative effects of abiotic factors and biotic interactions between a habitat‐modifying North American stream fish (Nocomis leptocephalus) and two of its nearly‐obligate beneficiary species (Chrosomus oreas and Clinostomus funduloides).LocationSixty‐one sites on tributaries to the New River basin in the Appalachian mountains of the eastern United States.MethodsWe sampled fishes using backpack electrofishing in the summers of 2012–2014. We gathered 10 habitat covariates from the National Hydrography Dataset and from instream measurements. We reduced dimensionality in habitat variables, corrected them for spatial autocorrelation and selected two eigenvectors as habitat covariates. We then used an information‐theoretic approach to compare two‐species occupancy models representing hypotheses specifying the importance of only habitat, only biotic interactions, or combinations of both.ResultsThe best model for each species combination specified the importance of biotic interactions. For both associate species, probabilities that associates would occur in the absence of their host were considerably lower than probabilities of co‐occurrence. Species interaction factors indicated positive patterns of co‐occurrence between hosts and associates. Models suggested that habitat variables mediated host‐associate interactions for C. oreas but not for C. funduloides.Main conclusionsThis study provides some of the first large‐scale quantitative evidence of positive co‐occurrence among vertebrates, and demonstrates the importance of abiotic context for mediating interspecific interactions. Two‐species occupancy modelling may be superior to traditional co‐occurrence analyses for parsing out the relative importance of biotic interactions and habitat variables for determining species distributions. However, experiments and small‐scale behavioural observations will also be necessary to confirm mechanisms.

Fish growth, physiological stress, and tissue condition in response to rate of temperature change during cool or warm diel thermal cycles

The effect of the rate of temperature change on fish was studied by exposing a variety of North American fish species to diel temperature cycles containing rates of change of 0.8, 1.1, 2.2, or 4.4 °C·h−1. During a simulated cool season (3.9–11.7 °C), bluntnose minnow (Pimephales notatus), spotfin shiner (Cyprinella spiloptera), and white sucker (Catostomus commersonii), but not smallmouth bass (Micropterus dolomieu), gained mass in response to 0.8, 1.1, or 2.2 °C·h−1but not constant mean temperature. White sucker did not grow under 4.4 °C·h−1, which was slower than expected based upon bioenergetics models. Physiological indicators of acute stress (day 1 cortisol), chronic stress (day 44 cortisol and triglycerides), and histomorphological measures suggested no effect of treatment. During a simulated warm season (20.0–27.8 °C), growth by channel catfish (Ictalurus punctatus), rosyside dace (Clinostomus funduloides), smallmouth bass, and spotfin shiner was not altered by any rate of temperature change; however, walleye (Sander vitreus) and white sucker grew slower than expected under 4.4 °C·h−1. Physiological indicators of acute stress (day 1 cortisol), chronic stress (day 29 cortisol and triglycerides), and histomorphological measures suggested no effect of treatment. Chronic exposure to temperature change of 4.4 °C·h−1may not induce an acute or chronic stress response but may slightly impair growth for some species.

Input matching and patch use by native and invasive minnows

AbstractWhen members of a population choose patches that maximise individual net energy gain without interference, they are input matching, a strategy derived from the ideal free distribution (IFD) that results in equal rewards across all patches. We investigated the input matching abilities of yellowfin shiner, a recent invader, and rosyside dace, a common native minnow, found in Coweeta Creek, North Carolina, USA. To test the species' relative input matching abilities, we varied food abundance within the range found in the natural habitat in a two‐patch laboratory stream to document the distribution of foragers when food densities differed in the ratio of 2:1. We then applied simple IFD model predictions to determine whether the observed distribution of foragers was best described by (i) the IFD, (ii) differing competitive abilities or (iii) the ideal despotic distribution and/or other unequal competitor models, and to ascertain whether the invader demonstrated a superior ability to track resource distributions. Yellowfin shiner was more likely to move between patches, which resulted in increased ability to match the distribution of food when prey abundance increased. The distribution of rosyside dace between patches did not change in response to increased food abundance. Despite a considerable range of competitive abilities within intraspecific groups, the ‘equal competitors’ IFD was as good at predicting fish distributions as ‘unequal competitor’ models. The ability to track local resource availability in highly variable environments facilitates maximising energy intake and likely promoted the establishment of yellowfin shiner in a southern Appalachian stream.

Isolation and characterization of microsatellite loci in the redside dace, Clinostomus elongatus

We isolated and characterized eight polymorphic microsatellite loci for redside dace (Clinostomus elongatus), a colorful North American cyprinid that is threatened or endangered throughout most of its range. The number of alleles per locus ranged from three to eighteen, with observed heterozygosity ranging from 0.31–0.92. Cross-amplification revealed that these markers will also be useful for examining closely related and more distantly related species, including the rosyside dace (Clinostomus funduloides), Lahontan redside shiner (Richardsonius egregius), hornyhead chub (Nocomis biguttatus), and central stoneroller (Campostoma anomalum). These microsatellite loci will provide a valuable set of tools for examining fine and coarse scale population structure, exploring reproductive success, and testing outcomes of proposed conservation initiatives (e.g. captive breeding and translocation of wild individuals) for redside dace.

Turbidity, velocity and interspecific interactions affect foraging behaviour of rosyside dace (Clinostomus funduloides) and yellowfin shiners (Notropis lutippinis)

Abstract – Fish diversity is strongly affected by habitat degradation (e.g., increased turbidity) and invasive species. We examined the effects of turbidity, velocity, length, dominance and intra‐ and interspecific competition on focal point depth, movement rate, dominance and aggression rate in native rosyside dace (Clinostomus funduloides) and invasive yellowfin shiners (Notropis lutipinnis) in a southern Appalachian stream (NC, USA). We compared results for intra‐ and interspecific groups of fishes at two densities (two and four fishes), three turbidity levels (10, 20 and 30 nephelometric turbidity units), and two velocities (12, 18 cm·s−1). Dominance was significantly correlated with length in intraspecific groups of both species, and dominant fish held more profitable foraging positions about 75% of the time. Yellowfin shiners were dominant more often than rosyside dace in interspecific trials. Akaike’s Information Criterion indicated that models containing turbidity, velocity, species and intraspecific competition, explained the greatest amount of information in focal point depth data. By contrast, movement and aggression rates were best explained by models based on dominance and velocity. Finally, aggression rate was best explained by models containing fish length and turbidity. These results indicate that habitat degradation, intra‐ and interspecific interactions influence the foraging behaviour and future success of these species in the Little Tennessee River drainage.

The effects of turbidity and an invasive species on foraging success of rosyside dace (Clinostomus funduloides)

Summary1. Habitat degradation and biological invasions are important threats to fish diversity worldwide. We experimentally examined the effects of turbidity, velocity and intra‐ and interspecific competition on prey capture location, reactive distance and prey capture success of native rosyside dace (Clinostomus funduloides) and invasive yellowfin shiners (Notropis lutipinnis) in Coweeta Creek, North Carolina, U.S.A.2. Increased turbidity and velocity produced significant decreases in the number of prey captured forward of the fish’s location. It is possible that this represents an increase in the amount of energy expended per prey captured.3. We used Akaike’s Information Criterion (AIC) to evaluate competing explanatory models for reactive distance (10 generalised linear models, GLM) and prey capture success (9 generalised linear mixed models, GLMM).4. Reactive distance decreased by 12% with an increase from 2 to 4 conspecifics, whereas a 10 NTU increase in turbidity reduced reactive distance by 9%. Capture success was affected by velocity, dominance and competition, and varied among species. A 6 cm s−1 increase in velocity produced a 28% decline in capture probability; however, dominant fish were 3.2 times more likely to capture a prey item than non‐dominant fish. Yellowfin shiners only were 0.62 times as likely to capture a prey item as rosyside dace. Both intra‐ and interspecific competition reduced capture probability, and fish in high density intraspecific or interspecific trials were 0.46 times and 0.44 times as likely to capture prey, respectively, as fish in two fish intraspecific trials.5. These results suggest behavioural variables are as important as physical factors in determining reactive distance and capture probability by these minnows.

Top-down Effect of Fish Predation in Virginia Headwater Streams

We completed laboratory-feeding studies that demonstrated preference of the headwater stream fishes Gambusia holbrooki (Mosquitofish) and Clinostomus funduloides (Rosyside Dace) for smaller Gammarus pseudolimnaeus (amphipods) over larger ones. We also submerged oak leaf-litter bags in sections of streams with and without these fish predators. After three weeks, the mean number ± s.e. of amphipods per litter bag in streams with fish was significantly lower (289 ± 50 vs. 978 ± 122) and the average size of amphipods was significantly larger (13.9 ± 0.1 mg vs. 8.1 ± 0.1 mg), relative to streams without fish. The quantity and quality of leaf litter, however, were not significantly different. Top-down predation may have altered the population structure of stream-dwelling amphipods, but did not change leaf decomposition over the time of the study.

Turbidity Affects Foraging Success of Drift‐Feeding Rosyside Dace

AbstractThe effects of suspended sediment on nongame fishes are not well understood. We examined the effects of suspended sediment (i.e., turbidity) on reactive distance and prey capture success at spring–autumn (12°C) and summer (18°C) temperatures for rosyside dace Clinostomus funduloides in an artificial stream. Experimental turbidities ranged from 0 to 56 nephelometric turbidity units (NTUs) at the two temperatures, and sample sizes for each turbidity–temperature combination ranged from 5 to 10 fish. All fish were tested at a single, randomly selected turbidity. Nonlinear regression (dosage–response curves) detected a negative relationship between turbidity and reactive distance at both spring–autumn (R2 = 0.96) and summer (R2 = 0.90) temperatures. Turbidity also had a strong negative effect on capture success at both spring–autumn (R2 = 0.88) and summer (R2 = 0.70) temperatures. Two‐way analysis of variance showed that turbidity and temperature were significant in all models (P < 0.0001) and that there were no significant interactions. The median effective concentrations (EC50s, i.e., the concentrations required to elicit a response equal to 50% of the maximum response observed) for reactive distance regressions were 9.9 NTUs in spring and autumn and 9.2 NTUs in summer. Data from moderately impacted streams in the region indicate that these streams possess turbidities that exceed the EC50s approximately 50% of the time. These results suggest that turbidity negatively affects the foraging behavior of rosyside dace at even low to intermediate levels (>9 NTUs) and that these effects may vary seasonally.

Response of Fish Assemblages to Winter in Two Adjacent Warmwater Streams

Fish assemblages of small temperate streams are strongly influenced by harsh winter conditions, which are tolerated by year-round resident species and avoided by seasonal migrants. We tested effects of season and longitudinal position on total biomass, species abundances and body condition of fish in two neighboring streams (Plum Run, Brintons Run) in southeast Pennsylvania, USA. In each stream we sampled four pools in a downstream reach in close proximity to a larger (6th order) stream and four pools in a more isolated upstream reach during fall, winter and spring. Total biomass depended strongly on pool volume, with which other habitat variables (area, maximum depth, extent of undercut bank) were also correlated. Downstream pools of Plum Run (mean volume 18.1 m3, link magnitude 5) had 21 fish species, including 6 species of Centrarchidae that largely vacated the pools in winter. The assemblage in upstream pools of Plum Run and in both upstream and downstream pools of Brintons Run (mean volumes 5.6 m3, 5.7 m3 and 4.4 m3, respectively; all link magnitude 2), consisted of 7 to 11 species. These pools were dominated by Cyprinidae, generally lacked centrarchids and showed little seasonal variation. Three year-round resident cyprinids [Semotilus atromaculatus (Creek chub), Rhinichthys atratulus (Blacknose dace) and Clinostomus funduloides (Rosyside dace)] and the winter emigrant Catastomus commersonii (White sucker) were the most abundant species in the two streams. Body condition of all four species declined substantially in winter; effects of longitudinal position (upstream vs. downstream) on body condition were less pronounced and varied among species. Abundances of the three resident cyprinids were all negatively correlated with the abundances of large, potentially predatory, centrarchids. Occupation of downstream pools in the larger stream by the centrarchids during fall and spring, but emigration from the study area during winter, further modified the effects of winter on the fish assemblage.

Behavioural interactions between native smokey dace and introduced yellowfin shiner: implications from habitat selection theory for an ongoing invasion

The occupation of adjacent, non‐overlapping positions along environmental gradients by closely related and ecologically similar species has drawn considerable attention from ecologists over the past decades. Condition‐specific competition, wherein competitive superiority varies with the abiotic environmental gradient, has been proposed as the major structuring force behind such distributions. These concepts, however, are generally applied to explain the contemporary distribution of organisms that share an evolutionary history. Our aim was to apply these concepts to the naive interactions between native and introduced fishes. In 1990 yellowfin shiner (Notropis lutipinnis) were introduced into the headwaters of the Little Tennessee River of western North Carolina, U.S.A. where it exhibits microhabitat preferences that overlap significantly with those of a threatened native minnow, the smokey dace (Clinostomus funduloides raneyi). Previous research has established that these drift‐feeding minnows: (1) differ in their average ability to intercept drifting prey as a function of water velocity; (2) generally occupy focal‐point velocities that maximize the rate of prey capture; and, (3) occasionally defend the forward positions in foraging aggregations that form in high quality patches. We present the results of a series of experiments designed to: (1) evaluate the role of aggression in the establishment and maintenance of preferred foraging positions in drift‐feeding minnows; (2) test the effects of prey availability, group size, and velocity on dominance rank, spatial position in groups, and feeding rates of individuals; and, (3) evaluate the potential for condition‐specific competition to establish competitive refugia for the native within the natural heterogeneity of mountain streams.

Intraspecific aggression in rosyside dace, a drift‐feeding stream cyprinid

Individual rosyside dace Clinostomus funduloides in a semi‐natural, artificial stream displayed substantial differences in their aggressiveness and could be classified as: (1) non‐aggressive (NA, 18 of 30 rosyside dace), (2) moderately aggressive (MA, 9 of 30) and (3) highly aggressive (HA, 3 of 30). Rosyside dace groups, however, did not exhibit linear dominance hierarchies and fish size was only weakly correlated with the number of aggressive acts performed per individual. Small rosyside dace (<56 mm LF) were always non‐aggressive, but larger fish were present in all three aggression classes. The difference in size between the contestants was significantly, although not very strongly, correlated with the probability of winning an agonistic interaction (r 2=0·39). Aggressive rosyside dace may have ultimately gained higher fitness than less aggressive ones. HA individuals occupied the upstream‐most position within foraging groups significantly more often than other rosyside dace. This location should be the most profitable one because its occupant will be the first to encounter prey. HA rosyside dace also occupied significantly higher focal velocities that were closer to energetic optima than MA and NA ones. They also had greater foraging rates and were less solitary than less aggressive fish, but these differences only were significant at the P=0·066 and P=0·081 level, respectively. Finally, HA fish performed significantly more aggressive acts and feedings backwards than other individuals. Despite these differences, the effects of intraspecific aggression in rosyside dace appeared less substantial than those that have been observed in stream salmonids.

Downstream changes in the composition of the parasite community of fishes in an Appalachian stream.

The spatial distribution of 6 parasite species (Myxobolus sp., Dactylogyrus sp., Sterliadochona ephemeridarum, Plagioporus sinitsini, Allopodocotyle chiliticorum, Allocreadium lucyae) was studied in 5 species of fishes (Oncorhynchus mykiss, Clinostomus funduloides, Notropis chiliticus, Rhinichthys atratulus, Semotilus atromaculatus) in Basin Creek, an Appalachian stream in North Carolina. Nonmetric multidimensional scaling and vector fitting were used to determine if the proximity of sampling sites was related to community similarity. Position along Basin Creek was significantly related to parasite community structure. Breaks in parasite community composition were imposed by waterfalls at upstream areas of Basin Creek that restricted distributions of C. funduloides, N. chiliticus, and S. atromaculatus and at the downstream limit of the study area by a break in the distribution of S. ephemeridarum coincident with the existence of a dam but were independent of suitable piscine host distributions. These discontinuities in parasite community composition imply that the relationship between proximity of sites and community similarity is predictive because distance between sites is related to the probability that fish at different sampling sites recruit parasites from different species pools. This relationship is not the same for all component communities.

Plagioporus sinitsini (Digenea : Opecoelidae): a one-host life cycle.

Adult Plagioporus sinitsini occur within daughter sporocysts voided with the feces of prosobranch snails Elimia symmetrica in Basin Creek, North Carolina. These worms produced eggs containing active miracidia while still in the snail. Adults in snails and adults in rosyside dace, Clinostomus funduloides, collected from the same stream were indistinguishable morphometrically. Adults in snails develop from cotylocercous cercariae sequestered in daughter sporocysts that pass through the metacercaria stage. These observations, and previous study in Michigan, suggest that the life cycle of P. sinitsini has 3 potential pathways, i.e., a 3-host life cycle involving molluscan, arthropod, and piscine hosts, a 2-host life cycle involving only molluscan and piscine hosts, and a 1-host life cycle involving only the snail host. The truncated life cycles do not appear to be the result of paedomorphosis.

The effects of rainbow trout (Oncorhynchus mykiss) on the use of spatial resources and behavior of rosyside dace (Clinostomus funduloides)

Rainbow trout (Oncorhynchus mykiss) and rosyside dace (Clinostomusfitn- duloides) exhibit substantial overlap in microhabitat use in Coweeta Creek, North Carolina, USA. We conducted a replicated experiment in an artificial stream to assess the effects of both the presence of rainbow trout and dace density on: 1) microhabitat use, 2) agonistic behavior, 3) social behavior and 4) feeding rates of dace. Our results demonstrated that microhabitat use of dace was highly variable both among competi- tion treatments within a replicate and for the same competition treatment among repli- cates. Moreover, the pattern of the differences between competition treatments was not consistent among replicates. As a result, we detected a significant effect of experi- mental replicate on dace microhabitat use but no significant competition effect. Trout had little effect on the behavior of dace and intraspecific aggression was much more common than interspecific aggression. There were strong inter-individual differences in the agonistic behavior of dace, and 94 of the IT7 aggressive displacements ob- served were initiated by one or two highly aggressive individuals per replicate. We detected few significant acclimation or time of day effects. The significant differences in microhabitat use and behavior observed within replicates appeared to be a conse- quence of differential initial settlement patterns of dace or the presence of one or two highly aggressive dace in treatments. Hence, we do not believe that interspecific com- petition with rainbow trout has a strong effect on microhabitat use by dace in Co- weeta Creek.

Effects of habitat availability on dispersion of a stream cyprinid

We analyzed temporal changes in the dispersion of the rosyside dace,Clinostomus funduloides, (family Cyprinidae) in a headwater stream, to assess the role of habitat availability in promoting fish aggregation. The dace foraged alone and in groups of up to about 25 individuals, and dispersion varied significantly among monthly censuses conducted from May through December. In two of three study pools, dace aggregated during July, October and/or December, but spread out during other months, especially during September when dispersion did not differ significantly from random. Dispersion was not significantly correlated with the total amount of suitable habitat available to foraging dace, but during summer, corresponded to the availability of depositional areas adjacent to rapid currents. Foragers aggregated in eddies or depositional areas during high stream discharge in July, and shifted out of depositional areas when current velocities declined from July to September. During late autumn, however, aggregations formed independently of changes in habitat conditions, and dace dispersion did not vary significantly among months in a third pool. The study suggests that dace dispersion cannot be predicted from the overall availability of suitable habitat as estimated from point measurements of depth and velocity; both the occurrence of a specific habitat feature (i.e., eddies adjacent to high velocity currents) and seasonal differences in behavior more strongly influenced the spatial distribution of foragers.

An Energetic Model of Microhabitat Use for Rainbow Trout and Rosyside Dace

We constructed an energetic model to determine the optimal focal point current velocity (i.e. microhabitat) for rainbow trout (Oncorhynchus mykiss) and rosyside dace (Clinostomus funduloides) in Coweeta Creek, a fifth—order stream in North Carolina, USA. Energetic costs were evaluated by quantifying the metabolic expenditure associated with swimming at a given velocity. We estimated bebefits by measuring potential energetic gains of feeding at a given velocity. This included estimates of the ability of the fish to capture prey at different current velocities as well as etimates of the frequency and the energy content of drifting prey at various velocities. We derived separate models for small (53—70 mm SL [standard length]) and medium (71—125 mm SL) trout, and medium (47—52 mm SL) and large (53—70 mm SL) dace for all seasons, deriving net energy gain as a function of current velocity. We predicted fishes would occupy velocities at which net energy gain was maximized. Predicted velocities were compared with those utilized by fishes inhabiting Coweeta Creek. Optimal velocities predicted by energetic models ranged from 7.7 to 22.1 cm/s, and closely matched actual velocity use (average deviation = 2.6 cm/s). Prey capture success appeared to be the most important component in the models. Consequently, we constructed models based solely upon aspects of capture success; the average deviation from veolocity use with these models was only 1.8 cm/s. Thus, the ability of dace and trout to capture prey at varying velocities appears to be the dominant factor affecting microhabitat selection in these species.

Reproductive timing in three southern Appalachian stream fishes

AbstractWe quantified the reproductive biology of mottled sculpin (Cottus bairdi), rosyside dace (Clinostomus funduloides) and longnose dace (Rhinichthus cataractae) in Coweeta Creek, North Carolina, USA, a fifth order stream. These species are abundant in coldwater streams through out the southern Appalachian mountains, the southernmost limit of their range. We collected fishes from Coweeta Creek every second month (between July 1984 and January 1986) and quantified the seasonal reproductive cycles of females, using both histological techniques and the relative gonadal index (RGI). Both techniques indicated that I) C. bairdi reproduced between March and May, 2) CI. funduloides spawned between May and August and 3) R. cataractae were reproductively active between June and July. These conclusions were supported by the following: 1) the presence of reproductive coloration, 2) gravid females, 3) courtship displays, 4) the presence of nest‐guarding C. bairdi males and 5) the timing of young‐of‐the‐year recruitment. The reproductive characteristics of these 3 species were correlated with different environmental variables. The mean monthly RGI values for both C. bairdi and R. cataractae were inversely correlated with both maximum and minimum daily water temperatures. The mean RGI values for C. bairdi also were negatively correlated with photoperiod, whereas the values for R. cataractae and CI. funduloides were positively correlated with the change in daily photo period.