Shorthead Redhorse Research Articles

Mitochondrial DNA Barcoding Reveals First Documented Evidence of Golden Redhorse (Moxostoma erythrurum) in the Susquehanna River, Pennsylvania

Moxostoma macrolepidotum (Shorthead Redhorse) is a common fish species found throughout Pennsylvania's Susquehanna River basin. It is the only member of Moxostoma known to inhabit this river basin. Yet, when we compared 467 nucleotides of the mtDNA COI gene from Shorthead Redhorse (n = 4) directly upstream of Curwensville Reservoir (Susquehanna River, Curwensville, PA), we found that they appeared more similar to M. erythrurum (Golden Redhorse) from the Mississippi River basin than the native congener. In contrast, putative Shorthead Redhorse (n = 8) from other areas of the Susquehanna River were identified as Shorthead Redhorse using the same molecular marker. These findings provide the first evidence that Golden Redhorse now inhabit portions of the Susquehanna River in Pennsylvania.

Spatial trends and temporal declines in tissue metals/metalloids in the context of wild fish health at the St. Clair River Area of Concern

The St. Clair River, which flows from Lake Huron to Lake St Clair, receives discharges and emissions from numerous petroleum refineries, petrochemical facilities, and other sources. We used a multi-factor ANOVA to test for spatial and temporal changes in concentrations of trace metals/metalloids in homogenates of fish from Lake Huron (reference site) and two river sites - an industrialized region (Stag Island) and downstream Walpole Island/Chenal Écarte. In 2002/2003 and in 2014, we sampled 20 adult fish of each sex of the following species: shorthead redhorse (Moxostoma macrolepidotum), yellow perch (Perca flavescens); we added emerald shiner (Notropis atherinoides; unsexed) in 2014. There was a temporal decline of most metals/metalloids in shorthead redhorse at the river sites. Linear Discriminant Analysis separated the 2014 shorthead redhorse by site. Emerald shiners had higher concentrations of metals/metalloids, apart from mercury, than the other species; those concentrations were highest at Chenal Écarte, which warrants further research. Tissue concentrations of mercury, which declined temporally at Stag Island and Walpole Island, were above the protective guidance for wildlife consumers at all sites, but were lower than predicted to affect fish health. Apart from increased liver size (ANCOVA) in shorthead redhorse at Walpole Island (2014), the health variables in the riverine fish were stable or differed slightly from reference, which indicated good health and reproductive potential. In shorthead redhorse, tissue metals correlated inconsistently with health indices. Further research could ascertain if temporal declines in metals/metalloids in riverine SHRH are benefits of remediation actions or fluctuations with other causes.

Effects of the husky oil spill on gut microbiota of native fishes in the North Saskatchewan River, Canada

In July 2016, a Husky Energy pipeline spilled 225,000 L of diluted heavy crude oil, with a portion of the oil entering the North Saskatchewan River near Maidstone, SK, Canada. This event provided a unique opportunity to assess potential effects of a crude oil constituent (namely polycyclic aromatic hydrocarbons, PAHs) on a possible sensitive indicator of freshwater ecosystem health, the gut microbiota of native fishes. In summer 2017, goldeye (Hiodon alosoides), walleye (Sander vitreus), northern pike (Esox lucius), and shorthead redhorse (Moxostoma macrolepidotum) were collected at six locations upstream and downstream of the spill. Muscle and bile were collected from individual fish for quantification of PAHs and intestinal contents were collected for characterization of the microbial community of the gut. Results suggested that host species is a significant determinant of gut microbiota, with significant differences among the species across sites. Concentrations of PAHs in dorsal muscle were significantly correlated with gut community compositions of walleye, but not of the other fishes. Concentrations of PAHs in muscle were also correlated with abundances of several families of bacteria among fishes. This study represents one of the first to investigate the response of the gut microbiome of wild fishes to chemical stressors.

Seasonal selection of habitat by Spotted Bass and Shorthead Redhorse in a regulated river in the Midwest, USA

AbstractRiverine fish populations depend on habitats supporting their resource and life history needs. Dynamic streamflow caused by river regulation or natural events influences the distribution of downstream habitat characteristics. Through studying habitat selection, we can identify the most utilized and valuable habitats for the success of native fishes. We determined seasonal habitat selection of two common, native fish species on the Osage River downstream of Bagnell Dam, a hydroelectric dam in central Missouri, from April 2016 to June 2017 using radio telemetry. Spotted Bass (Micropterus punctulatus) are nest‐guarders, sight feeders, and habitat generalists, whereas Shorthead Redhorse (Moxostoma macrolepidotum) are fluvial dependent, migratory, and benthic feeders. Bayesian discrete choice analyses determined that both species selected particular water depth, velocity, and presence of submerged cover in some or all seasons, even as available habitat changed. Spotted Bass selected water depths <4.0 m near submerged cover during all seasons, low velocity during spring and summer, and near‐bank habitat in all seasons except spring. Shorthead Redhorse used fast flowing habitat during spring, 0.4–1.1 m/s velocity during summer, and low velocity in fall and winter (0.1–0.5 m/s). Shorthead Redhorse used submerged cover in all seasons except summer and selected specific ranges of depth within spring (2.4–4.4 m), summer (3.3–6.7 m), and winter (1.1–2.3 m). Our findings suggest that maintaining habitats with cover and diverse water depths and velocities, particularly both low and high velocity habitats during spring, may promote resilience by providing beneficial habitats for native fishes.

Tissue contaminants and wild fish health in the St. Clair River Area of Concern – Part 2: Spatial trends and temporal declines in organics

We explored tissue concentrations of polychlorinated biphenyls (PCBs), chlorinated pesticides, and relevant organochlorines and fish health in the following adult wild fish in the St. Clair River Area of Concern (Ontario, Canada): shorthead redhorse (Moxostoma macrolepidotum), yellow perch (Perca flavescens), and emerald shiner (Notropis atherinoides). We collected adult fish from sites within the river's industrial zone (Stag Island), a downstream site adjacent to Walpole Island (Chenal Écarte), and an upstream reference site in Lake Huron in 2002/2003 and 2014. We tested for trends in tissue concentrations of organic contaminants across sites and over time; we assessed the potential effects of contaminants on morphological indicators of fish health across sites by year. Over the 12-year period, the tissue concentrations of most PCBs declined at the river sites, except for some non-legacy PCBs (PCB11 and 185), which increased in yellow perch at Stag Island, a new observation for fish in the St. Clair River AOC. There was little difference between the concentrations of calculated toxic equivalents (TEQs) of the Lake Huron and the St. Clair River fish in 2014, except for emerald shiners from Stag Island which had elevated ΣPCB and TEQs. Each fish species at all sites exceeded the Canadian tissue residue guideline for PCBs for the protection of mammalian wildlife consumers of aquatic biota, but fish-derived TEQs indicated little potential health risk to fish. Over time, hexachlorobutadiene and hexachlorobenzene concentrations increased in some fish at Stag Island by about 8- and 4-fold, respectively, whereas they decreased at other sampling locations. Principal Component Analysis followed by Linear Discriminant Analysis of the 2014 SHRH data suggested that although the fish separated by site, tissue concentrations of PCB and organochlorine contaminants did not have consistent relationships to the morphological health indicators, including egg production in females, which implied the absence of causative relationships.

Seasonality of a Floodplain Subsidy to the Fish Community of a Large Temperate River

This study examines the temporal and spatial variability of the floodplain trophic contribution to the fish community of Lake Saint-Pierre, a large (≈ 300 km2), shallow (≈ 3 m) widening of the St. Lawrence River (Quebec, Canada). We hypothesized that floodplain contribution to fish diet would be maximal during the early growing period following the seasonal flood and at sites located closest to the floodplain. Carbon stable isotope ratios (δ13C) of invertebrates and 35 fish species were analyzed at the beginning and at the end of two growing seasons, at increasing distances from the floodplain. Floodplain contribution, in the form of exported aquatic invertebrates, was estimated at the fish community (littoral versus main river), species and individual fish level, using a stable isotopic mixing model and a linear mixed model selection. As hypothesized, fish captured in the early part of the growing season near the floodplain benefitted from the largest floodplain contribution, which decreased during the late growing season. In addition, floodplain contribution differed among fish species, being higher in small or immature littoral species (northern pike, yellow perch, blackchin and golden shiners) than for larger taxa inhabiting the main river channel (shorthead redhorse, white sucker and channel catfish). Our study revealed that floodplain production during the early growing season represents a key food resource to a large portion of the riverine food web, thus highlighting the essential role of the floodplain in human-altered temperate rivers.

Large‐bodied fish assemblage characteristics in large rivers across Ontario

AbstractLarge‐bodied fish assemblages were assessed in large rivers across Ontario. The objectives of this study were to (i) determine if there were relationships in large‐bodied fish species within rivers; (ii) determine what factors explain the variability in the abundance of large‐bodied fish within rivers across Ontario; and (iii) assessed variation in large‐bodied fish biodiversity among these river. Standardized index netting was conducted at 22 sites across 12 major rivers and sampled 3889 fish representing 26 species. Species associations were evident based on correspondence analysis. Walleye, Common White Sucker, Northern Pike and Lake Whitefish formed one group; Silver Redhorse, Shorthead Redhorse and Lake Sturgeon (adult and juvenile) formed another; Burbot, Longnose Sucker and Sauger were closely associated; and Cisco, Yellow Perch, Rock Bass, Smallmouth Bass and Brown Bullhead grouped. Canonical correspondence analysis was conducted to link species abundance patterns to environmental conditions. Walleye, Common White Sucker, Lake Whitefish and Smallmouth Bass were ubiquitous. Northern Pike abundance was negatively correlated with river discharge and longitude. Burbot, Sauger and Longnose Sucker abundance were positively correlated with deep rivers and discharge. Whereas Cisco, Yellow Perch and Rock Bass abundance were greater in wider rivers with lower discharge. Lake Sturgeon (adult and juvenile), Silver Redhorse and Shorthead Redhorse abundance were greater in narrow, longer rivers. Juvenile Lake Sturgeon abundance was positively correlated with longitude and river discharge. Mean species diversity and richness of large‐bodied fish among all sites was 1.58 (0.36 SD) and 7.7 (2.6 SD). Species diversity was not significantly related to any of the variables used in the Generalized Linear Model; however, species richness was significantly related to maximum depth. This study demonstrated subtle differences in environmental variables affecting large‐bodied fish at the landscape scale rather than those observed at the river scale.

Habitat use and population characteristics of potentially spawning shovelnose sturgeonScaphirhynchus platorynchus(Rafinesque, 1820), blue sucker (Cycleptus elongatus(Lesueur, 1817), and associated species in the lower Wisconsin River, USA

Summary The goal of this study was to compare the possible locations, timing, and characteristics of potentially spawning shovelnose sturgeon (Scaphirhynchus platorynchus), blue sucker (Cycleptus elongatus), and associated species during the spring of 2007–2015 in the 149-km-long lower Wisconsin River, Wisconsin, USA, a large, shallow, sand-dominated Mississippi River tributary. A 5-km index station of two pairs of rocky shoals surrounded by sandy areas was electrofished for shovelnose sturgeon and blue sucker in a standardized fashion a total of 40 times from late March through mid-June, the presumed spawning period. On one date in 2008 and two dates in 2012, all rocky shoals and adjacent sandy areas in the lowermost 149 km of the river were also electrofished for both species. Shovelnose sturgeon and blue sucker appeared to spawn in the limited rocky areas of the river along with at least four other species: mooneye (Hiodon tergisus), quillback (Carpiodes cyprinus), smallmouth buffalo (Ictiobus bubalus), and shorthead redhorse (Moxostoma macrolepidotum), usually at depths of 0.8–2.0 m and surface velocities of 0.4–1.0 m/s. However, apparently spawning shovelnose sturgeon were found only on mid-channel cobble and coarse gravel shoals within a single 7-km segment that included the 5-km index station, whereas apparently spawning blue suckers were encountered on these same shoals but also more widely throughout the river on eroding bluff shorelines of bedrock and boulder and on artificial boulder wing dams and shoreline rip-rap. Both species showed evidence of homing to the same mid-channel shoal complexes across years. Blue sucker tended to concentrate on the shoals earlier in the spring than shovelnose sturgeon, usually from late April through mid-May at water temperatures of 8.0–15.5°C along with quillback and shorthead redhorse. In comparison, shovelnose sturgeon usually concentrated on the shoals from mid-May through early June at 13.5–21.8°C along with mooneye and smallmouth buffalo. Based on recaptures of tagged fish, at least some shovelnose sturgeon and blue sucker returned to the shoals at one-year intervals, although there was evidence that female blue sucker may have been more likely to return at two-year intervals. Most shovelnose sturgeon could not be reliably sexed based on external characteristics. Spawning shovelnose sturgeon ranged from 487 to 788 mm fork length, 500–2400 g weight, and 5–20 years of age, whereas spawning blue sucker ranged from 495 to 822 mm total length, 900–5100 g weight, and 5–34 years of age, although age estimates were uncertain. Females were significantly larger than males for both species although there was overlap. Growth in length was negligible for tagged and recaptured presumably spawning shovelnose sturgeon and low (3.5 mm/y) for blue sucker, suggesting that nearly all growth may have occurred prior to maturity and that fish may have matured at a wide range of sizes.

Fishway approach behaviour and passage of three redhorse species (Moxostoma anisurum, M. carinatum, and M. macrolepidotum) in the Richelieu River, Quebec

Fishways are increasingly constructed to maintain longitudinal connectivity for fish in numerous river systems where migrations are interrupted by anthropogenic barriers, although there is a paucity of information on the biological effectiveness of fishways for most species. We evaluated fishway approach behaviour, and quantified attraction and passage efficiency of three catostomid species (silver redhorse Moxostoma anisurum, river redhorse M. carinatum and shorthead redhorse M. macrolepidotum) that undertake annual obligate spawning migrations through the Vianney-Legendre vertical slot fishway at the St. Ours Dam, in the Richelieu River, Quebec, Canada. Use of PIT tagging alone enabled quantification of attraction and passage efficiency and these were; 51, 17 and 50 % for attraction efficiency and passage efficiencies were 88, 50, and 69 % for silver, river, and shorthead redhorse, respectively. Silver redhorse had significantly shorter entrance delay and passage duration times than shorthead redhorse. Attraction efficiency was different among release locations for silver redhorse, and passage efficiency increased with size for shorthead redhorse. For all species, failure to ascend the fishway was most likely to occur before the second turning basin (before the 32 m mark) in the fishway (84 % of failures). Silver redhorse had significantly lower passage failure rates than river and shorthead redhorse. Activity patterns in the three species during fishway passage were different; crepuscular activity patterns were observed in shorthead and river redhorse, whereas silver redhorse activity peaked between 23:00 and 02:00 then decreased through the remainder of the day. To further evaluate fishway approach behaviour we fitted an additional sample of each species with external radio tags, although nearly all radio tagged individuals (n = 119) rapidly moved downstream upon release immediately post-tagging. Subsequently, our results were confounded by the behavioural impairments associated with external radio tagging and fallback. These results demonstrate the value of multispecies fishway evaluations and highlight the variation among individual species fishway performance within a single genus.

Influence of Environmental Variables on Catostomid Spawning Phenology in a Warmwater River

Abstract Associations between environmental variables and reproductive condition of six catostomid (family Catostomidae) species were evaluated in the Baraboo River, Wisconsin. Electrofishing and hoop net surveys conducted from Mar. to Jun. of 2001 and 2002 revealed white sucker (Catostomus commersoni) reached spawning condition first, followed by quillback (Carpiodes cyprinus) in both years. These two species were followed by the overlapping spawning times of spotted sucker (Minytrema melanops), golden redhorse (Moxostoma erythrurum), shorthead redhorse (M. macrolepidotum), and silver redhorse (M. anisurum). The first axis of a principal component analysis (PCA; based on six environmental variables) explaining 47% of the variation in the environmental variables represented water temperature, flow, and day of the year. The second axis explaining an additional 26% of variation depicted the magnitude of shorter-term changes in water temperature and flow. The best-fitting multinomial logit model to explain v...

Comparative Physiology and Relative Swimming Performance of Three Redhorse (Moxostomaspp.) Species: Associations with Fishway Passage Success

Our understanding of biological criteria to inform fish passage design is limited, partially due to the lack of understanding of biological motivators, cues, and constraints, as well as a lack of biological performance evaluations of structures once they are built. The Vianney-Legendre vertical slot fishway on the Richelieu River, Quebec, Canada, passes large numbers of migrating redhorse (Moxostoma spp.) upriver to spawning grounds each year. We evaluated the physiological capacity and relative swimming ability of three redhorse species (Moxostoma anisurum, Moxostoma carinatum, Moxostoma macrolepidotum; silver, river, and shorthead redhorse, respectively) to determine how these biotic factors relate to variation in fishway passage success and duration. Shorthead redhorse had higher maximum metabolic rates and were faster swimmers than silver and river redhorse at their species-specific peak migration temperatures. Blood lactate and glucose concentrations recovered more quickly for river redhorse than for silver and shorthead redhorse, and river redhorse placed second in terms of metabolic recovery and swim speed. Interestingly, fish sampled from the top of the fishway had nearly identical lactate, glucose, and pH values compared to control fish. Using passive integrated transponders in 2010 and 2012, we observed that passage success and duration were highly variable among redhorse species and were not consistent among years, suggesting that other factors such as water temperature and river flows may modulate passage success. Clearly, additional research is needed to understand how organismal performance, environmental conditions, and other factors (including abundance of conspecifics and other comigrants) interact with fishway features to dictate which fish will be successful and to inform research of future fishways. Our research suggests that there may be an opportunity for a rapid assessment approach where fish chased to exhaustion to determine maximal values of physiological disturbance are compared to fish sampled from the top of the fishway, which could reveal which species (or sizes of fish) are approaching or exceeding their physiological capacity during passage.

Ontogeny of Larval and Juvenile Black Redhorse (Moxostoma duquesnei)

Adult Black Redhorse (Moxostoma duquesnei) were seined from the Grand River, Ontario and artificially spawned in May 2007 and May 2008. Eggs hatched after 9–16 days at a mean temperature of 20°C, and after 11–25 days at a mean temperature of 17°C. Eggs did not develop fully at temperatures <11°C. Eggs and development of larvae between 9 and 24 mm TL, and juveniles up to 35 mm TL are described. Ontogeny of larval and juvenile Black Redhorse was compared to that of Greater Redhorse (Moxostoma valenciennesi), River Redhorse (Moxostoma carinatum), Golden Redhorse (Moxostoma erythrurum), Shorthead Redhorse (Moxostoma macrolepidotum), Copper Redhorse (Moxostoma hubbsi), and Spotted Sucker (Minytrema melanops). There was significant overlap between most meristic variables compared. However, the majority of Black Redhorse in this study (up to 18 mm TL) generally had higher myomere counts that were different from most other redhorse species. These data, in combination with knowledge of variation in congeneric dist...

Comparison of Detection Efficiency among Three Sizes of Half‐Duplex Passive Integrated Transponders Using Manual Tracking and Fixed Antenna Arrays

AbstractWe compared detection efficiency for three lengths (12, 23 and 32 mm) of half‐duplex (HDX) passive integrated transponder (PIT) tags for both manual tracking and fixed array applications. In a stream we used a wand‐type manual tracking antenna and determined that detection efficiency was considerably influenced by tag size (i.e., 20% for 12 mm, 43% for 23 mm, and 81% for 32 mm) and water depth. Vertical and horizontal read range also varied among tag sizes (lower for smaller tags) and orientation (12‐mm and 23‐mm tags oriented perpendicularly failed to read in the horizontal test). Using a fixed PIT array, we also compared the detection efficiency of the same three sizes of PIT tags in Shorthead Redhorse Moxostoma macrolepidotum released into a fishway. Again, detection efficiency increased with tag size: 12 mm = 55.8 ± 9.2% (mean ± SE), 23 mm = 91.0 ± 1.8%, and 32 mm = 97.0 ± 1.5%. When using PIT telemetry on smaller fish species and/or life stages, we suggest that researchers consider the tag size, as the diminished detection efficiency of 12‐mm tags could introduce a bias and impede the ability to address some research questions.Received July 11, 2012; accepted September 20, 2012

HETEROGENEITY IN LEVELS OF SERUM NEUTRALIZING ANTIBODIES AGAINST VIRAL HEMORRHAGIC SEPTICEMIA VIRUS GENOTYPE IVB AMONG FISH SPECIES IN LAKE ST. CLAIR, MICHIGAN, USA

The presence of neutralizing antibodies against viral hemorrhagic septicemia virus (VHSV-IVb) was investigated in sera of 13 fish species collected from Lake St. Clair, Michigan, USA, a VHSV-endemic water body. We tested 297 sera collected May 2004-June of 2010, using a complement-dependent 50% plaque neutralization test (50% PNT). Neutralizing antibodies were detected in 23% (67/297) of the samples. The highest overall antibody prevalence (85%, 34/40) and mean positive antibody titer (12,113 ± 11,699 SD) were detected in muskellunge (Esox masquinongy). Antibodies were also detected in 50% (15/30) of sampled northern pike (E. lucius), 25% (15/61) of freshwater drum (Aplodinotus grunniens), and 7% (3/41) of smallmouth bass (Micropterus dolomieu). All sera from channel catfish (Ictalurus punctatus), lake sturgeon (Acipenser fulvescens), quillback (Carpiodes cyprinus), rock bass (Ambloplites rupestris), shorthead redhorse (Moxostoma macrolepidotum), silver redhorse (M. anisurum), walleye (Sander vitreus), white perch (Morone americana), and yellow perch (Perca flavescens) were negative. Antibodies in one or more fish species were detected in all sampling years (2004, 2006, 2007, 2009, and 2010), whereas in parallel sampling periods, VHS virus was detected only in 2006 and 2009. Our results suggest the continued presence of VHSV-IVb in the Lake St. Clair ecosystem, and underscore the importance of assessing immune responses of fish populations to determine prior virus exposure.

MULTISPECIES FISH PASSAGE BEHAVIOUR IN A VERTICAL SLOT FISHWAY ON THE RICHELIEU RIVER, QUEBEC, CANADA

ABSTRACTA shift from target species to ecosystem restoration has generated interest in developing fishways that are capable of passing entire fish communities. Although a number of multispecies fishways now exist in North America, evaluations of these fishways are lacking. We used a passive integrated transponder antenna array to quantify passage success and passage duration of fish using a vertical slot fishway (85 m in length, 2.65 m elevation rise, 12 regular pools and 2 turning basins) at a low head dam on the Richelieu River in Quebec, Canada. Fourteen of the 18 tagged species re‐ascended the fishway, and passage efficiency was highly variable among species (range 25%–100%); however, it was &gt;50% for five of the species well represented in this study (n &gt; 10) (Atlantic salmon, channel catfish, smallmouth bass, walleye and white sucker). Passage duration was likewise highly variable both among and within species (e.g. 1.0–452.9 h for smallmouth bass, 2.4–237.5 h for shorthead redhorse). Although this fishway design was not uniformly successful in passing fish of all species, this study does reveal the species that have problems with ascent and provides an estimate on the time spent in the fishway that is an important component of passage delay. Such information could be used to inform future design refinements to facilitate passage of the entire assemblage with minimal delay. Copyright © 2012 John Wiley &amp; Sons, Ltd.

Trophic ecology and gill raker morphology of seven catostomid species in Iowa rivers

Summary Understanding the trophic ecology of closely-related species is important for providing insight on inter-specific competition and resource partitioning. Although catostomids often dominate fish assemblages in lotic systems, little research has been conducted on their ecology. This study was developed to provide information on the trophic ecology of catostomids in several Iowa rivers. Food habits, diet overlap, and gill raker morphology were examined for highfin carpsucker Carpiodes velifer, quillback C. cyprinus, river carpsucker C. carpio, golden redhorse Moxostoma erythrurum, shorthead redhorse M. macrolepidotum, silver redhorse M. anisurum, and northern hogsucker Hypentelium nigricans sampled from four Iowa rivers (2009). Diet overlap among all species was calculated with Morista’s index (C). Food habit niche width was quantified with Levin’s index (B) and similarity in gill raker morphology was compared with analysis of covariance. Values from Morista’s index suggested significant overlap in the diets of highfin carpsucker and river carpsucker (C = 0.81), quillback and river carpsucker (C = 0.66), and shorthead redhorse and silver redhorse (C = 0.67). Levin’s index indicated that golden redhorse (B = 0.32), quillback (B = 0.53), and river carpsucker (B = 0.41) had the most generalized feeding strategies as their food niche widths were substantially wider than the other species. Gill raker length and spacing were positively correlated with the standard length of the fish for all species (gill raker length: r2 = 0.67–0.88, P ≤ 0.01; gill raker spacing: r2 = 0.63–0.73, P ≤ 0.01). Slopes of regression of gill raker length and spacing to standard lengths were significantly (P ≤ 0.05) different among species, indicating that rates of change in gill raker morphology with body length varied among species. Differences in gill raker morphology likely allow catostomids to partition resources and reduce competitive interactions.

POPULATION DEMOGRAPHICS OF CATOSTOMIDS IN LARGE RIVER ECOSYSTEMS: EFFECTS OF DISCHARGE AND TEMPERATURE ON RECRUITMENT DYNAMICS AND GROWTH

ABSTRACTCatostomids are among the most widespread and ecologically important groups of fishes in North America, particularly in large river systems. Despite their importance, little information is available on their population demographics and even less is known about factors influencing their population dynamics. The objectives of this study were to describe annual mortality, recruitment variation, and growth of eight catostomid species, and to evaluate the effects of discharge and temperature on year‐class strength and growth in Iowa rivers. Catostomids were sampled from 3‐km reaches in four nonwadable rivers during June–August 2009. Northern hogsucker, Hypentelium nigricans, golden redhorse, Moxostoma erythrurum, and shorthead redhorse, M. macrolepidotum, typically lived 6–8 years, had very stable recruitment, and had high total annual mortality (i.e., 40–60%). Golden redhorse exhibited the fastest growth of all species. Growth of northern hogsucker and shorthead redhorse was intermediate to the other catostomids. Highfin carpsucker, Carpiodes velifer, quillback, Carpiodes cyprinus, and white sucker, Catostomus commersonii, had high growth rates, low mortality (i.e., 25–30%), and relatively stable recruitment. River carpsucker, Carpiodes carpio, and silver redhorse, M. anisurum, had higher maximum ages (up to age 11), slower growth, lower total annual mortality (20–25%), and higher recruitment variability than the other species. Neither discharge nor temperature was strongly related to recruitment of catostomids. In contrast, several interesting patterns were observed with regard to growth. Species (e.g., carpsuckers, Carpiodes spp.) that typically consume prey items most common in fine substrates (e.g., chironomids) had higher growth rates in reaches dominated by sand and silt substrate. Species (e.g., northern hogsucker) that consume prey associated with large substrates (e.g., plecopterans) had much faster growth in reaches with a high proportion of rocky substrates. Temperature was weakly related to growth of catostomids; however, discharge explained a substantial amount of the variation in growth of nearly all species. Results of this study provide important information on the autecology of catostomids that can be used for comparison among species and systems. These data also suggest that connection of rivers with their floodplain is an important feature for catostomids in temperate river systems. Published in 2011 by John Wiley &amp; Sons, Ltd.

A method to estimate sediment ingestion by fish

A method is proposed to use naturally occurring radionuclides of the 238U decay series as mass balance tracers to estimate sediment ingestion by benthic fish. The mass balance tracer method can take two forms: one that does not account for tracers that would be ingested in invertebrate food items (simple mass balance tracer method) and one that does (adjusted mass balance tracer method). The contents of the gastrointestinal (GI) tracts from 17 Shorthead Redhorse Suckers ( Moxostoma macrolepidotum) were analyzed using the proposed method to determine the proportion of sediment in the fish gut. The proportion of sediment in the GI tract samples was also determined using a method developed by Beyer et al. (1994), where the percent soil in wildlife is estimated from the acid insoluble residue (AIR) content of their scat and an assumed level of digestibility of their food (AIR method). The mean mass of sediment in the GI tracts of the 17 fish sampled, calculated using the simple mass balance tracer method, was observed to be 1.14 g (standard deviation 0.99 g) or approximately 46% (standard deviation 16%) of the dry weight of total GI tract contents. A mean of 0.97 g (standard deviation 0.85 g), or approximately 38% (standard deviation 13%) of the dry weight of total GI tract contents, was observed when the mass of sediment in the GI tract was calculated using the adjusted mass balance tracer method. When using the AIR method, the mean percentage of sediment in the GI tracts was observed to be 30% (standard deviation 16%). The findings in this study support the assertion that direct ingestion of sediment by benthic fish may be an important pathway for contaminants in aquatic food webs.

Leeches (Annelida: Hirudinida) Parasitizing Fish of Lake St. Clair, Michigan, U.S.A.

Abstract In order to identify leech species prevalent in Lake St. Clair, Michigan, U.S.A,. and understand their effect on fish hosts, fish were collected during May 2006 and 2007 from Anchor Bay, Lake St. Clair in the Laurentian Great Lakes Basin. Throughout the study, 2,117 fish from 21 species were examined for the presence of leeches. Overall, 1,064 leeches were collected from 165 individual fish and identified morphologically. Hosts included the channel catfish, freshwater drum, northern pike, northern shorthead redhorse sucker, quillback sucker, rock bass, smallmouth bass, walleye, and yellow perch. Leeches attached to hosts had a prevalence of 7.79%, with a mean intensity of 6.45 leeches/infected fish and an abundance of 0.50 leeches/examined fish. Collected leeches were identified as Actinobdella pediculata (Glossiphonidae), Placobdella montifera (Glossiphonidae), and Myzobdella lugubris (Piscicolidae), which was the most commonly occurring species. The freshwater drum had the highest prevalence, m...

Morphology and Taxonomic Status of Two Little-Known Nematode Species Parasitizing North American Fishes

Examination of some freshwater and brackishwater (estuarine) fishes in South Carolina in October 2009 yielded, in addition to other parasites, 2 little-known nematode species identified as Dichelyne fastigatus Chandler, 1935 (Cucullanidae), from the red drum, Sciaenops ocellatus (Linnaeus), from an estuary, and Rhabdochona ovifilamenta Weller, 1938 (Rhabdochonidae), from the shorthead redhorse, Moxostoma macrolepidotum (Lesueur), from Lake Moultrie. Light and scanning electron microscopy (the latter used for the first time for these species) made it possible to describe several important, but previously unreported, taxonomic features in D. fastigatus, such as the location of the excretory pore and deirids, the shape of deirids and a gubernaculum, the shape and size of eggs, the presence of precloacal ventral oblique muscle bands, and 11 pairs of caudal papillae and a pair of phasmids. It distinctly differs from the most similar Dichelyne cotylophora (Ward and Magath, 1917), a parasite of North American freshwater percids, in the number and arrangement of postanal papillae and by a markedly elevated cloacal region. Records of Dichelyne lintoni Barreto, 1922, from S. ocellatus probably concern D. fastigatus. Examination of R. ovifilamenta revealed a high degree of morphologic and biometric variability in this species. Based on our analysis, Rhabdochona laurentiana Lyster, 1940 , Rhabdochona milleri Choquette, 1951, and Rhabdochona catostomi Kayton, Kritsky, and Tobias, 1979, are synonymized with R. ovifilamenta Weller, 1938, typically a parasite of North American catostomids.