Notropis Rubellus Research Articles

Stage‐specific abiotic and biotic associations of the imperilled Silver ShinerNotropis photogenisin an urban drainage

AbstractStage‐specific abiotic and biotic associations are often poorly described for imperilled freshwater fishes, including Silver Shiner (Notropis photogenis; Threatened), which may limit species protection and recovery efforts. Here, we used fish and habitat sampling data from an urban drainage in southern Ontario, Canada to quantify abiotic and biotic associations for juvenile and adult Silver Shiner, while considering the potential effects of imperfect detection on sampled fishes. Detection probability of Silver Shiner was high (>0.80) across life‐stages, but occupancy models for adults and juveniles included different covariates. The top‐selected occupancy model (lowest Akaike's Information Criterion [AICc]) for adults included a positive effect of site depth, whereas sampling year was included in the top‐selected occupancy model for juveniles. A redundancy analysis suggested unique stage‐specific biotic associations; a positive association was observed between the abundance of adult Silver Shiner and Rosyface Shiner (Notropis rubellus), whereas positive associations were observed between juvenile Silver Shiner and the abundance of Fathead Minnow (Pimephales promelas) and Smallmouth Bass (Micropterus dolomieu). Overall, the results of this study advance the knowledge of stage‐specific abiotic and biotic associations of Silver Shiner, and the probability of species detection, which will inform future monitoring and protection of the species in Canada. More broadly, continued efforts are needed to quantify early life‐stage habitat requirements for informing the recovery of imperilled freshwater species.

Characterizing species co-occurrence patterns of imperfectly detected stream fishes to inform species reintroduction efforts.

Species reintroduction efforts can improve the recovery of imperiled species, but successful implementation of this conservation strategy requires a thorough understanding of the abiotic and biotic factors influencing species viability. Species interactions are especially understudied, in particular by omitting the effect of imperfect detection on negative, neutral, or positive associations within a community. Using repeat surveys from 5 southern Ontario, Canada, Great Lakes tributaries, we quantified species co-occurrence patterns with the eastern sand darter (ESD) (Ammocrypta pellucida), listed as federally threatened, and characterized how imperfect detection during sampling can influence inference regarding these relationships. We used a probabilistic framework that included 3 approaches of increasing complexity: probabilistic co-occurrence analysis ignoring imperfect detection; single-species occupancy models with subsequent co-occurrence analysis; and 2-species occupancy models. We then used our occupancy models to predict suitable sites for potential future reintroduction efforts while considering the influence of negative species interactions. Based on the observed data, ESD showed several positive associations with co-occurring species; however, species associations differed when imperfect detection was considered. Specifically, a negative association between ESD and rosyface shiner (Notropis rubellus) was observed only after accounting for imperfect detection in the Grand River. Alternatively, positive associations in the Grand River between ESD and northern hogsucker (Hypentelium nigricans) and silver shiner (Notropis photogenis) were observed regardless of whether imperfect detection was accounted for. Our models predicted several potential reintroduction sites for ESD in formerly occupied watersheds with high levels of certainty. Overall, our results demonstrate the importance of investigating imperfect detection and species co-occurrence when planning reintroduction efforts.

Biogeography and Distribution of the Cryptic Species Rosyface ShinerNotropis rubellusand Carmine ShinerNotropis percobromusin Illinois

Conservation and management of cryptic species is particularly challenging since it can be difficult to determine their exact distributions. Knowledge of species distribution is required to recognize management units based on taxonomy and whether there are any pertinent biogeographic patterns that could be relevant to the development of a management plan. Such a situation exists in Illinois with the Rosyface Shiner Notropis rubellus and Carmine Shiner Notropis percobromus. There are no reliable anatomical characters to distinguish between the two species. Instead, they are distinguished by genetic data. Samples were obtained for these two species from across the state from each major watershed in which they are found. Based on cytochrome b sequence variation the two species can be distinguished by 44 species-distinct differences. Notropis percobromus is restricted to the Rock River watershed and nearby Mississippi River tributaries in northwest Illinois. Notropis rubellus is found in the Illinois River ba...

Fish assemblage and habitat factors associated with the distribution of Topeka shiner (Notropis topeka) in Kansas streams

Topeka shiners (Notropis topeka) were historically abundant throughout many Great Plains streams but their abundance and distribution declined and the species was listed as federally endangered in 1999. However, few studies have examined how Topeka shiner populations are linked to biotic and abiotic factors. Thus, the objectives of this study were to identify trends in Topeka shiner distribution from 1995 to 2008 and determine which fish assemblage and habitat factors were most associated with Topeka shiner distribution in Kansas streams. Fish and in-stream habitat metrics were collected from 34 sites in northeast Kansas in 1995, 2003, and 2008. Stepwise discriminant function analyses (DFA) were used to determine if fish assemblage percent composition and in-stream and landscape habitat factors could be used to differentiate among years and between sites with and without Topeka shiners. Higher percent composition of rosyface shiner (Notropis rubellus) was generally indicative of sites with Topeka shiners whereas higher relative abundance of central stoneroller (Campostoma anomalum) and largemouth bass (Micropterus salmoides) were associated with sites without Topeka shiners. Sites with Topeka shiners also tended to have more gravel substrate and greater mean stream length, whereas sites without Topeka shiners generally had higher proportional impoundment area and proportional urban land area. These findings suggest that anthropogenic alteration of habitat in and around streams with Topeka shiners may facilitate their declines and establishment of non-native or generalist fishes. Our results may help managers identify habitats with the greatest need for protection or restoration and may help protect Topeka shiner populations from further population declines.

Isolation and characterization of 10 polymorphic microsatellite markers for the Ouachita Highlands endemic Notropis suttkusi (Teleostei: Cyprinidae)

Human pressures primarily associated with urbanization, forestry practices, over-mining of groundwater, and reservoir construction threaten the exceptional aquatic endemism of the Ouachita Highlands of southeastern Oklahoma and southwestern Arkansas, USA. At present, there is a need for hypervariable markers useful for understanding population structure and historical demography, thereby helping to provide a framework for conservation efforts. In this paper we describe 10 microsatellite markers for Notropis suttkusi (rocky shiner), a species endemic to the Ouachita Highlands. We characterize these markers on 40 individuals from Blue River in Oklahoma. The loci yielded 3–23 alleles per locus, with mean observed and expected heterozygosites of 0.679 and 0.729, respectively. The availability of these markers will facilitate studies of the conservation genetics of N. suttkusi and should be useful for other members of the Notropis rubellus complex.

The Utility of Molecular Hypotheses for Uncovering Morphological Diversity in the Notropis rubellus Species Complex (Cypriniformes: Cyprinidae)

When molecular phylogeography results in the discovery of hidden diversity, this diversity is often labeled as cryptic. Few studies have gone back to the morphology to determine whether or not this molecular diversity is in fact detectable at the morphological level. The Notropis rubellus species complex has a widespread distribution in freshwater streams of eastern North America. Recent molecular studies have identified up to seven allopatric clades, suggesting that there may be morphologically cryptic diversity within the group. This study uses traditional meristics and geometric morphometric methods to test molecular hypotheses of cryptic diversity within the species complex. Meristic data and a principal component analysis of geometric morphometric data supported the cryptic hypothesis. Canonical variates analyses (CVA), however, were able to detect statistically significant, clade-specific morphological variation, suggesting that in this case, cryptic diversity was an artifact of the detection method. CVA thus provided a useful tool for identifying subtle or complex shape variation. However, morphological variation within the N. rubellus species complex was undetectable without a pre-existing molecular hypothesis.

Ecological niche conservatism in North American freshwater fishes

There are many hypotheses of relationships, and also of speciation processes, in North American freshwater fishes, although, to date, there have been no direct tests of whether there is evidence of ecological niche conservatism. In the present study, ecological niche modeling is used to look for evidence of ecological niche conservatism in six clades of freshwater fishes: the starheaded topminnows, sand darters, black basses, Notropis rubellus species group, Notropis longirostris species group, and the Hybopsis amblops species group. This is achieved by evaluating the reciprocal predictivity of distributional predictions based on ecological niche models developed for each individual taxon in a clade under the assumption that high reciprical predictivity between sister species can be taken as evidence of niche conservatism. Omission percentages, total and average commission, and the area under the curve in a receiver operating characteristic analysis, where calculated, are used to evaluate predictive ability. Occurrence data for each species were subset into a training and independent validation data set where possible. Across all clades and species, models predicted the validation data for a given species well. Ecological niche conservatism was found generally across the starheaded topminnows, the sand darters, and the N. longirostris species group. There was some inter-predictivity within the N. rubellus group, but almost no inter-predictivity within the black basses, indicating a lack of conservatism. These results demonstrate that ecological niches generally act as stable constraints on freshwater fish distributions in North America.

Recovering cryptic diversity and ancient drainage patterns in eastern North America: Historical biogeography of the Notropis rubellus species group (Teleostei: Cypriniformes)

The Central Highlands of North America contain a strikingly diverse assemblage of temperate freshwater fishes and have long been a focus of biogeographic studies. The rosyface shiner complex, Notropis rubellus and related species, is a member of this fauna exhibiting a disjunct highlands distribution occurring in the unglaciated regions of the Central Highlands and glaciated regions of the Central Lowlands. Until recently, N. rubellus was considered a single, widespread species exhibiting geographic variation in morphological characters. However, several studies have revealed that N. rubellus is a multi-species complex with closely related species endemic to drainages within each highland region. We examined genetic variation of the N. rubellus complex using a complete mtDNA cytochrome b gene sequence data set and combined mtDNA and published allozyme data sets. Parsimony and Bayesian analyses of the mitochondrial data set and parsimony analyses of a combined mitochondrial and allozyme data sets were largely consistent. Results of these analyses revealed ancient cryptic diversity within the N. rubellus complex that existed prior to the onset of Pleistocene glaciations. We identified seven strongly supported clades within the N. rubellus complex. Four clades are diagnosed as separate species ( N. percobromus, N. rubellus, N. micropteryx and N. suttkusi) and three clades may represent undescribed forms. Relationships among these groups and their biogeographical patterns provided significant inferences on ichthyofaunal distributions in southeastern North America. These include the timing of the origin of the diversity, ancient drainage patterns and barriers to dispersal in the Central Highlands. The observation of increased diversity in N. rubellus suggests there may be greater diversity within other taxa with a similar distribution.

Redescription of Rhabdochona cotti (Nematoda, Rhabdochonidae) from Cottus caeruleomentum (Teleostei, Cottidae) in Maryland, USA, with remarks on the taxonomy of North American Rhabdochona spp.

AbstractThe nematode Rhabdochona cotti Gustafson, 1949 is redescribed from specimens collected from the intestine of the blue ridge sculpin Cottus caeruleomentum (a new host record), a recently described fish species, from Little Fishing Creek in Maryland, USA. The measurements of these specimens, collected in November 2005, are generally smaller than those reported in the original description of R. cotti, this being probably associated with the nematode’s seasonal maturation cycle or the different host species. As revealed by SEM, the deirids of R. cotti are simple (not bifurcate), in which this species differs from almost all North American congeners. Of these, simple deirids, filamented eggs and a rounded tail tip in females occur only in Rhabdochona longleyi, but it distinctly differs from R. cotti in the smaller number of anterior prostomal teeth (6 vs. 14). Rhabdochona rotundicaudatum is considered a junior synonym of Rhabdochona cascadilla; numerous specimens of the latter were collected from Semotilus atromaculatus, Luxilus cornutus and Notropis rubellus from the type locality (Eramosa River, Ontario, Canada) (unpublished). Rhabdochona paxmani and Rhabdochona salmonis are synonymized with Rhabdochona kisutchi, whereas Rhabdochona californiensis is considered a junior synonym of R. cascadilla. The need of a taxonomic revision of North American species of Rhabdochona is stressed.

Morphological Variation and Systematics of the Notropis rubellus Complex in Kentucky and Tennessee

Samples of the Notropis rubellus complex were collected from 33 localities in Kentucky and Tennessee during the late spring and early summer of 1998–2001. Based on nuptial coloration, scale and fin-ray counts, and body shape, two taxa were diagnosed and recognized as species in the study area. Notropis rubellus (Agassiz) occupies upland streams of the Ohio River basin upstream of the mouth of the Green River and in the Cumberland River drainage above Cumberland Falls. Notropis micropteryx (Cope) occurs in upland streams of the Cumberland River drainage downstream of Cumberland Falls and the Tennessee River and Green River drainages. This species differs from N. rubellus in having modally fewer circumferential scales (23–24 vs. 25–26), modally fewer scales below the lateral line (three vs. four), and less red on the dorsum of the head of nuptial males. Green River populations exhibit more mean scales below the lateral line and slightly more intense red than other N. micropteryx populations. Support for recognition of these taxa as evolutionary species includes zoogeographic evidence in addition to the array of morphological characters.

Phylogenetic Relationships of Cyprinid Fishes in SubgenusNotropisInferred from Nucleotide Sequences of the Mitochondrially Encoded CytochromebGene

Cytochrome b sequences (1140 bp) from 16 species considered to be members of subgenus Notropis and several outgroup taxa were analyzed phylogenetically. Phylogenetic analysis of cytochrome b was sensitive to sampling of outgroup taxa, probably resulting from substitutional rate heterogeneity among outgroups. Maximum-likelihood analysis was more robust to these effects as compared to maximum parsimony. Both maximum parsimony and maximum-likelihood analysis supported removal of Notropis candidus and Notropis shumardi from subgenus Notropis. Monophyly of the 14 remaining species was supported by the maximum likelihood analysis. Regardless of the method of analysis or use of outgroup taxa, phylogenetic analysis of cytochrome b indicated strong support for the following hypothesis of relationships: ((Notropis rubellus, Notropis suttkusi), (Notropis amoenus, Notropis stilbius, ((Notropis atherinoides, Notropis oxyrhynchus), (Notropis amabilis, Notropis jemezanus)))). This phylogenetic hypothesis implies that morphological characters associated with increased olfaction were derived independently among members of subgenus Notropis, perhaps in response to life in more turbid habitats.

Diplostomatid Eye Flukes in Young-of-the-Year and Forage Fishes in the St. Lawrence River, Quebec

Sixteen species of young-of-the year and forage fishes (alewife Alosa pseudoharengus, northern pike Esox lucius, common carp Cyprinus carpio, emerald shiner Notropis atherinoides, rosyface shiner Notropis rubellus, white sucker Catostomus commersoni, silver redhorse Moxostoma anisurum, brown bullhead Ameirurus nebulosus, trout-perch Percopsis omiscomaycus, rock bass Ambloplitis rupestris, pumpkinseed Lepomis gibbosus, smallmouth bass Micropterus dolomieu, largemouth bass Micropterus salmoides, black crappie Pomoxis nigromaculatus, johnny darter Etheostoma nigrum, and logperch Percina caprodes) collected from five sites in the St. Lawrence River in 1997–1998 were examined for eye flukes. Twelve species were infected with metacercariae of Diplostomum spp. Benthic fishes, including brown bullhead and white sucker possessed the heaviest infections. Where spatial comparisons were possible, no geographic difference in infection levels of Diplostomum spp. metacercariae was observed. Monthly or seasonal differences in mean abundance, mean intensity, and prevalence of Diplostomum spp. metacercariae were observed for emerald shiners between May and June 1998, for white suckers between July and September 1997, and for brown bullhead between July and August 1997. Diplostomum spp. metacercariae were found largely in the vitreous humor of brown bullheads. In all other species, the vast majority of parasites were found in the lens. Other diplostomatid metacercariae (Tylodelphys spp., Neascus spp.) occurred infrequently and only in the vitreous humor. These results demonstrate that most of the fish species examined from the St. Lawrence River become infected with metacercariae of Diplostomum spp. during their first years of life. Recruitment of metacercariae appears to occur during spring–early summer and late summer, matching observations made in other systems in Europe and North America.

Notropis suttkusi, a New Cyprinid from the Ouachita Uplands of Oklahoma and Arkansas, with Comments on the Status of Ozarkian Populations of N. rubellus

A new species of cyprinid, Notropis suttkusi, the rocky shiner, is described from tributaries of the Red River draining the Ouachita Uplands in Oklahoma and Arkansas. The geographic range of N. suttkusi extends from the Blue River in Oklahoma eastward to the Cossatot River in Arkansas. It is found primarily in the upper portions of these rivers, and prefers clear water flowing over gravel and rubble substrates. The rocky shiner is compared to populations of the rosyface shiner, Notropis rubellus, from the adjacent Ozark Uplands and east of the Mississippi River, from which it can be distinguished by its deeper and more robust body form; shorter snout and upper jaw; denser pigmentation on scales, lips, and gular region; finer tubercles on the snout; greater extent of lateral band; and more deeply decurved lateral line. A brief discussion of the confusing taxonomic history involving N. atherinoides, N. oligaspis, N. percobromus, and N. rubellus is presented.

New Distributional Records of the Rosyface Shiner and Slender Madtom in Kansas

A new distributional record in Geary County for the slender madtom (Noturus exilis) was documented by Layher and Wood (1986). That record consisted of one specimen (KU 21086) captured on 18 May 1984 from East Branch Humboldt Creek. A second specimen (KU 21424) was taken on 22 April 1986 by Layher and Wood from Davis Creek, Geary County, E 1/2 Sec. 2, T13S, R6E. This collection contained five other species: central stoneroller, Campostoma anomalum, (1 specimen; KU 21417); common shiner, Notropis cornutus (1 specimen; KU 21418); southern redbelly dace, Phoxinus erythrogaster (3 specimens; KU 21422); creek chub, Semotilus atromaculatus (1 specimen; KU 21423); and orangethroat darter, Etheostoma spectabile (1 specimen; KU 21425). The collection from Davis Creek also included three specimens of the rosyface shiner (Notropis rubellus) (KU 21420), and one hybrid, N. rubellus x N. cornutus (KU 21419). These represent the first record of the rosyface shiner in Geary County. Another collection on 22 April 1986, from Dry Creek in Sec. 17, T16S, R7E, Geary County, also contained rosyface shiners (2 specimens; KU 21413). Other fishes in that collection were the topeka shiner, Notropis topeka (1 specimen; KU 21414); redfin shiner, Notropis umbratilis (1 specimen; KU 21415); and orangethroat darter (1 specimen; KU 21416). Collections from numerous other streams in Geary County during the same week did not include either the rosyface shiner or the slender madtom. Previous stream surveys by the Kansas Fish and Game Commission, chiefly in the 1970's, provided no evidence of the occurrence of either species in Geary County (Layher and Brunson, 1986). The rosyface shiner and slender madtom normally inhabit permanently flowing, clear, upland streams with alternating pools and limestone riffles. In the Kansas River basin, both species are most abundant in Flint Hills streams, especially those of the Mill Creek drainage in Wabaunsee County (Metcalf, 1965; Cross, 1967). The Geary County sites are farther west in the Kansas River basin than any localities previously known for either species, but are within the Flint Hills upland; populations of both may long have

The Zoogeography of the Fishes of the Youghiogheny River System, Pennsylvania, Maryland and West Virginia

A total of 266 fish collections were made at 172 stations in the Youghiogheny River drainage, the largest tributary to the Monongahela River. Collections were made using seines, electrofishing gear, gill nets and trap nets. A comprehensive literature review yielded 99 species of fishes reported from the Youghiogheny River system. Six species collected during this survey (Amia calva, Carassius auratus, Ericymba buccata, Notropis rubellus, Ictalurus catus and Fundulus diaphanus) established new distributional records for the system, increasing the total to 105 species. Of this total, 78 species were verified either by our collections (57 species), museum records (10) or stocking records (11), whereas 27 could not be verified. Of the 27 unverified species, 21 are expected to occur and six are considered misidentifications or erroneous records. An additional 24 species are expected to have occurred historically in the Youghiogheny or have the potential to do so based on their distribution in the Monongahela or Allegheny rivers. Of the 78 species of fishes confirmed to have occurred in the Youghiogheny River, 57 were collected during this survey, 11 were unsuccessful introductions and nine have probably been extirpated. One species, Esox masquinongy, is considered extant, but was not collected during this study. The ichthyofauna of the Youghiogheny River system was largely derived from Teays River by dispersal up the newly formed Ohio River after the onset of Pleistocene glaciation. Two species, Clinostomus elongatus and Catostomus catostomus, dispersed into the Youghiogheny from the N during the Pleistocene. Rhinichthys atratulus atratulus dispersed into the Youghiogheny from Potomac River via stream capture. Several species, (Jampostoma a. anomalum, Ericymba buccata, Nocomis micropogon, Notropis spilopterus and Etheostoma b. blennioides, may have used Youghiogheny-Potomac stream captures as a dispersal route eastward into the Atlantic slope.

Egg, Larval and Juvenile Development of Longnose Dace, Rhinichthys cataractae, and River Chub, Nocomis micropogon, with Notes on Their Hybridization

Artificially spawned eggs of longnose dace and naturally spawned eggs of river chub were incubated at 21 ? 3 C through hatching and the larvae reared through the juvenile phase. Development was similar in each species but rates differed. Opercles, mouth, heart and blood circulation developed earlier in longnose dace; fin ray and scale development occurred at a faster rate in river chub. Mean total length of longnose dace at hatching ranged from 4.5 to 5.9 mm and differed significantly between two streams: the smaller larvae hatched from significantly smaller eggs produced by smaller females. No significant differences were found in egg size or mean hatching length in river chub which hatched at a mean total length of 5.9 mm. Larval development was complete at 110 days in longnose dace and 57 days in river chub. Collections in river chub nests contained eggs of longnose dace, river chub, common shiner, creek chub and rosyface shiner in various combinations. Longnose dace and river chub eggs occurred together in each stream sampled and hybrid longnose dace x river chub have been reported from three of the five streams sampled. The use of river chub nests by longnose dace for spawning may be due to a lack of spawning habitat for dace elsewhere in the stream or to a preference for stone nests and may be a primary cause for hybridization between longnose dace and river chub.

Significance of Hypochlorous Acid in Free Residual Chlorine to the Avoidance Response of Spotted Bass (Micropterus punctulatus) and Rosyface Shiner (Notropis rubellus)

The spotted bass (Micropterus punctulatus) and rosyface shiner (Notropis rubellus), when exposed to successively doubling doses of total residual chlorine (TRC) from 0.025 to 0.80 mg/ℓ, generally avoided higher concentrations when acclimated and tested at five temperatures from 6 to 30 °C. Both species avoided 0.05 mg/ℓ TRC when acclimated and tested at 6 °C and avoided 0.20 mg/ℓ TRC at 24 and 30 °C. Variations in avoidance of the free residual chlorine (FRC) ranged from 0.017 to 0.091 mg/ℓ (0.05 to 0.20 mg/ℓ TRC) between 6 and 30 °C. After the initial avoidance response, the rosyface shiner continued to avoid the remaining higher residual levels, while spotted bass showed less avoidance or none at all. The same behavioral responses occurred when each species was exposed to a single concentration (0.05 or 0.10 mg/ℓ TRC) for three successive 10-min observations.The avoidance response was most closely associated with the calculated hypochlorous acid (HOCl) fraction of the TRC, which declined (relative to the percent of TRC) as the pH and acclimation temperature increased. Avoidance to HOCl occurred between 0.012 mg/ℓ (6 °C) and 0.031 mg/ℓ (30 °C) when TRC was between 0.05 and 0.20 mg/ℓ, respectively. Avoidances did not occur at the 12 and 18 °C acclimation temperatures until the HOCl content comprising the 0.10 and 0.20 mg/ℓ TRC doses surpassed the initial HOCl threshold level (0.012–0.014 mg/ℓ) calculated for 0.05 mg/ℓ TRC at 6 °C. The HOCl content may be the most important constituent within the TRC to influence the avoidance response of fish in unpolluted aquatic systems. Key words: avoidance response, hypochlorous acid, free residual chlorine, Micropterus punctulatus, Notropis rubellus

A FIELD EVALUATION OF THE EFFECTS OF HEATED DISCHARGES ON FISH DISTRIBUTION1

ABSTRACT. Studies were conducted to determine the distribution of fish in the New and East Rivers in relation to thermal discharges from Appalachian Power Company's fossil fuel plant at Glen Lyn, Virginia. Over 15,300 specimens representing 41 species were collected with seines, electrogear and rotenone at six sampling locations from February, 1973 to October 1973. Sampling frequency was designed to evaluate the effects of ambient temperature upon preferred temperature. Diversity indices were calculated for each location. There was a slight decrease in the diversity indices for those stations located in the thermal discharge. Condition coefficients calculated for Notropis albeolus Jordan, Notropis rubellus Aqasaiz, Notropis spilopterus Cope, Ictalurus punctatus Rafinesque, and Etheostoma blennioides Rafuesque were found to be significantly (p =.05) lower in the thermal discharge for all species tested except E. blennioides. Temperatures were plotted against frequency of capture to determine a particular species temperature selection from field data and indicated that: (1) Some species avoided high temperatures (i.e., Curnpostoma anomalum Rafuesque). (2) Some species were attracted to high temperatures (i.e., Ictalurus punctatus). (3) Some species distribution was not effected by temperatures (i.e., Notropis spilopterus).

Natural Hybridization of Cyprinid Fishes in Little Patuxent River, Maryland

Three natural combinations of cyprinid hybrids were found in the Little Patuxent River, Maryland in the vicinity of the Fall Line. They resulted from the spawning ofNotropis cornutus, Notropis rubellus andClinostomus funduloides over the nests ofNocomis micropogon. The hybridN. rubellus ×C. funduloides was an unreported hybrid combination. It was rare; its characteristics were intermediate between the parental species. The hybridN. cornutus ×N. rubellus was common whileN. cornutus ×C. funduloides occurred rarely. The particular ecology, including the high stream gradient and generally sandy bottom with boulders and bedrock, appeared to contribute to the hybridization. The rarity of hybrids involvingC. funduloides is attributed to the greater genetic isolation. There appeared to be no relationship between the frequency of hybridization and the distance between the precise positions of the parental species as they spawned over theNocomis nest.

Systematics of the Cyprinid Fish Notropis amoenus, with Comments on the Subgenus Notropis

Notropis amoenus (Abbott) is redescribed and a detailed synonymy presented. Comments are made regarding its nomenclature, type-specimens, and habitat. Sixteen meristic and 10 morphometric characters show no regular pattern of geographic variation and no subspecies are recognized. The most variable meristic character is predorsal scale size; specimens with small, irregularly-arranged predorsal scales become progressively more frequent in northern populations. Mandible and snout lengths are generally shorter in northern populations, complicating the separation of N. amoenus from the closely related Notropis atherinoides Rafinesque. Sexual dimorphism in N. amoenus is weakly developed and confined chiefly to tuberculation differences, which are described. Breeding individuals show no chromatic coloration. N. amoenus is compared with similar and related species. It is specifically distinct from and distantly related to Notropis rubellus (Agassiz), a sympatric and often confused species. Notropis photogenis (Cope) differs from N. amoenus in possessing nine pelvic fin rays, an extremely rare feature in the genus. N. atherinoides is the closest relative of N. amoenus; distinguishing characters are scale counts, head proportions, and trophic modifications. The two species are largely allopatric, but their ranges overlap or come into proximity in New York. The ranges of N. amoenus and central and southeastern New York N. atherinoides are plotted, and their postglacial zoogeography discussed. The dispersal of both species has been influenced by man. N. amoenus is assigned to the subgenus Notropis Rafinesque, and problems within this group are discussed. The subgenus is divisible into two sections on the basis of breeding coloration and pectoral fin tuberculation. The N. rubellus group exhibits chromatic breeding colors. The first ray of the pectoral fin is nontuberculate and following rays bear a single file of large tubercles, a single tubercle occupying each ray segment. This group has no close relative among species currently assigned to the subgenus, and may be related to some species currently classified in the subgenus Hydrophlox Jordan and Brayton. The N. atherinoides group (which includes N. amoenus) and species commonly classified near it are characterized by the absence of chromatic breeding colors. The first ray of the pectoral fin is tuberculate and the following rays bear small tubercles arranged bi- or multiserially, with