White Sucker Catostomus Commersonii Research Articles

Environment Affects Sucker Catch Rate, Size Structure, Species Composition, and Precision in Boat Electrofishing Samples

Abstract Catostomidae (catostomids) are suckers of the order Cypriniformes, and the majority of species are native to North America; however, species in this group are understudied and rarely managed. The popularity in bowfishing and gigging for suckers in the United States has increased concerns related to overfishing. Little information exists about the relative gear effectiveness for sampling catostomids. We sought to evaluate the relative effectiveness of boat electrofishing for sampling Black Redhorse Moxostoma duquesnei, Golden Redhorse M. erythrurum, Northern Hogsucker Hypentelium nigricans, White Sucker Catostomus commersonii, and Spotted Sucker Minytrema melanops populations in Lake Eucha, Oklahoma. We used an information theoretic approach to determine the abiotic variables related to sucker catch per effort (C/f). Our analysis indicated that sucker C/f was highest during the night and decreased with increasing water temperature. Sucker size structure was significantly different between daytime and nighttime samples; however, effect size estimates for size structure comparisons indicated that size distributions exhibited moderate overlap. Distributional comparisons indicated that daytime and nighttime samples were similar for fish greater than 180 mm in total length. Effect size estimates also indicated little association between the proportion of each species captured and time of day or water temperature. Night electrofishing in reservoirs at water temperatures from 16 to 25°C yielded the most precise C/f estimates, with the highest numbers of suckers collected at water temperatures from 6 to 15°C. Further study of the relationship between abiotic variables and catostomid catchability using various gears will be beneficial to agencies interested in these populations.

Coarse woody habitat use by local fish species and structural integrity of enhancements over time in a shallow northern boreal lake assessed in a Bayesian modelling approach

Abstract The introduction of coarse woody habitat has been a widely adopted management practice for restoring and enhancing freshwater aquatic ecosystems. Although responses of aquatic fish and invertebrate communities have largely been documented for lotic systems, benefits for lentic ecosystems have been mostly unevaluated. We tested the responses of fish populations to coarse woody habitat structures through a Bayesian modelling approach in a northern boreal lake in Alberta, Canada by enhancing a stretch of littoral zone with low structural complexity through introduction of coarse wood bundles and whole tree structures. The study site was split into three treatments, a Spaced treatment (structures 30 m apart), a Clustered treatment (structures 15 m apart) and an unaltered area (Control). Catch per unit effort and catch per unit area data were collected over 2 years and posterior model predictions showed an increase in habitat use of the enhanced areas by spottail shiner—Notropis hudsonius; northern pike—Esox lucius; white sucker—Catostomus commersonii; brook stickleback—Culaea inconstans. No probable effect on overall fish condition, measured in Relative Weight, was linked to the enhancements. Across the 2‐year study, wood bundles degraded faster compared to the whole tree drops, coinciding with levelling off catch per unit effort and catch per unit area predictions near wood bundles, although catch predictions increased near the whole tree structures. Structural degradation set in as early as 1 week post‐construction for wood bundles and was mostly related to anchoring aspects. Results from our study provide evidence for the benefits provided by coarse woody habitat within northern boreal lake systems. They furthermore highlight the short‐lived nature of wood bundles built with biodegradable substances. Methodologically our results offer evidence on the feasibility and utility of predictive modelling frameworks in addressing pseudoreplication and providing informative value for ecological studies.

Attraction, Entrance, and Passage Efficiency of Arctic Grayling, Trout, and Suckers at Denil Fishways in the Big Hole River Basin, Montana

AbstractThe Big Hole River basin in southwestern Montana supports the only indigenous, self‐sustaining fluvial population of Arctic Grayling Thymallus arcticus in the conterminous United States, but the basin is fragmented by numerous low‐head irrigation diversion dams. Denil fishways at 63 diversion dams provide Arctic Grayling and other fishes opportunities for year‐round access to critical habitats; however, their efficiency has not been evaluated. We quantified attraction, entrance, and passage for hatchery‐reared Arctic Grayling, wild trout (Brook Trout Salvelinus fontinalis and Brown Trout Salmo trutta), and wild suckers (White Sucker Catostomus commersonii and Longnose Sucker C. catostomus) during 14 field trials conducted at six Denil fishways over a representative range of fishway slopes and hydraulic conditions using passive integrated transponder telemetry. Attraction (60.4–84.3%) and entrance (44.3–78.6%) efficiencies were variable across test conditions and reduced overall fishway efficiencies (19.1–55.8%). In contrast, upon entry, passage efficiencies were high (96.2–97.0%) for all taxa across all test conditions. Attraction of hatchery‐reared Arctic Grayling increased with upstream depth (a surrogate for fishway discharge) and attraction flow, but attraction of wild fish was less affected by these conditions. Entrance of Arctic Grayling, Brook Trout, and Brown Trout decreased with upstream depth and fishway slope, especially when plunging entrance conditions associated with shallow downstream depths were present. However, entrance of Arctic Grayling and both trout species increased with downstream depth, and submerged fishway entrances demonstrated promise for increasing entrance efficiency at fishways with high discharges and steep slopes. We demonstrate that comprehensive evaluations of fishway efficiency components can identify specific solutions that improve fishway efficiency; application of these engineering solutions at individual fishways (as needed) could improve their efficiency and further enhance aquatic connectivity for fishes in the Big Hole River basin and elsewhere.

It's complicated: Heterogeneous patterns of genetic structure in five fish species from a fragmented river suggest multiple processes can drive differentiation.

Fragmentation of river systems by dams can have substantial genetic impacts on fish populations. However, genetic structure can exist naturally at small scales through processes other than isolation by physical barriers. We sampled individuals from five native fish species with varying life histories above and below a dam in the lower Boardman River, Michigan, USA, and used RADseq to investigate processes influencing genetic structure in this system. Species assessed were white sucker Catostomus commersonii, yellow perch Perca flavescens, walleye Sander vitreus, smallmouth bass Micropterus dolomieu, and rock bass Ambloplites rupestris. We detected significant differentiation within each species, but patterns of population structure varied substantially. Interestingly, genetic structure did not appear to be solely the result of fragmentation by the dam. While genetic structure in yellow perch and walleye generally coincided with “above dam” and “below dam” sampling locations, samples from our other three species did not. Specifically, samples from rock bass, smallmouth bass, and, to a much lesser extent, white sucker, aligned with a putative Great Lakes (GL) group that contained mostly individuals sampled below the dam and a putative Boardman River (BR) group that contained individuals sampled both above and below the dam, with some evidence of admixture among groups. We hypothesize that the GL and BR groups formed prior to dam construction and our samples largely represent a mixed stock that was sampled sympatrically outside of the spawning season. Support for this hypothesis is especially strong in smallmouth bass, where GL fish were 151 mm smaller than BR fish on average, suggesting a potential ontogenetic habitat shift of young GL fish into the lower river for feeding and/or refuge. Our study illuminates the complex dynamics shaping genetic structure in fragmented river systems and indicates that conclusions drawn for a single species cannot be generalized.

Environmental factors influencing annual sucker (Catostomus sp.) migration into a Great Lakes tributary

Fish migration in rivers is a growing area of concern as mounting anthropogenic influences, particularly fragmentation from dams and barriers, constitute major threats to global river species diversity. Barriers can impede the movement of fishes between areas critical to the completion of their lifecycle, affecting both population and ecosystem viability. In response, fish passage solutions have been identified as a critical need to maintain fisheries viability in the Laurentian Great Lakes, and around the world. Pivotal to the success of these fish passage solutions is a more complete understanding of the movement phenology and environmental cues that instigate migration. We used a dual-frequency identification sonar (DIDSON) to evaluate environmental triggers of river entry during spring and summer for three size classes of migratory fishes in the Boardman River, a Lake Michigan tributary. Our results indicate that medium size fish (>30 cm and < 50 cm), primarily composed of white sucker Catostomus commersonii and longnose sucker Catostomus catostomus were 21% more likely to enter the river at sunset and 25% less likely at midnight in comparison to midday. Entry rates of medium fish increased 6% for every 1 °C increase in river temperature, 4% for every 1 m3/s increase in river discharge from the day prior, and were reduced by 1% for every 10 cm increase in lake level. Understanding these processes in the tributaries of the Great Lakes is important to inform the fish passage solutions currently being developed for the Boardman River, and to inform management regulations for Great Lakes migratory fishes.

Are Muskellunge Affecting Fish Communities in Waters Where They Have Been Introduced? A Re‐examination of Minnesota’s Stocked Muskellunge Waters

AbstractMuskellunge Esox masquinongy are large piscivores stocked into numerous lakes in North America, but the potential effects of these stockings remains poorly understood. To investigate potential fish community changes associated with Muskellunge stocking, we contrasted catch per unit effort (CPUE) for seven fish species commonly found in Minnesota, along with mean weight for two predator species, before and after Muskellunge introduction in 36 lakes with that of paired reference lakes. Because of the known importance of Cisco Coregonus artedi as prey for Muskellunge, we also examined these data by separating the lakes into those with and without Cisco. Across all 36 lakes, we observed several significant differences between stocked and reference lakes. Yellow Perch Perca flavescent CPUE in gill nets were significantly higher after Muskellunge were introduced, as was mean weight for Northern Pike Esox lucius. Gill‐net CPUE for Northern Pike and White Sucker Catostomus commersonii were both lower following Muskellunge introduction. When subsets of lakes with and without Cisco were considered, results for the 21 lakes without Cisco were similar to the results of the entire set of lakes. In the 15 lakes with Cisco, the only significant result was lower Northern Pike CPUE after Muskellunge stocking. Our results are evidence that the introduction and management of Muskellunge in these lakes has not adversely affected game fish populations.

Suitability of surgically implanted 8‐mm passive integrated transponder tags for small‐bodied fishes

Innovative tools that benefit conservation are critical as freshwater fishes are lost at unprecedented rates. Mark-recapture methods can characterize population demographics and life-history traits of diverse fishes, but suitable techniques for tagging for individual recognition of small-bodied fishes are rare. Passive integrated transponder (PIT) tag technology may facilitate the tagging of small fishes and early life stages of larger species. However, relatively little research has evaluated the suitability of these small (8.4 × 1.4 mm) tags for many groups of small fishes. Tag loss (retention and survival) and growth of individuals implanted with PIT tags relative to control and sham treatments were compared for eight fishes of differing morphologies. Additionally, the utility of cyanoacrylate to improve tag retention was tested on a subset of taxa. Fish of each species were equally divided and randomly assigned to one of three treatment groups (handled [control], surgical incision [sham], or surgical incision and PIT tag implantation [PIT]). During the 42-d study period, mortalities and expelled tags were counted daily and growth was measured weekly. Researchers can generally expect little tag loss and uncompromised growth rates for a variety of small-bodied fishes; however, initial fish length was related to the magnitude of physiological effects for some taxa (i.e., blacknose dace Rhinichthys atratulus, johnny darter Etheostoma nigrum, juvenile white sucker Catostomus commersonii). Relatively poor survival (<80%) was observed for two benthic species: johnny darter and blacknose dace, often when incision wounds became inflamed before healing. Prevalent tag loss for johnny darter, tadpole madtom Noturus gyrinus, and a dorsal-laterally compressed cyprinid can be reduced by closing the wounds with cyanoacrylate, but with substantially increased mortality rates. This research demonstrates the broad applicability of PIT tagging technology for ecological studies of small-bodied fishes and alleviates many concerns when surgically implanting tags into several fishes.

Effects of White Sucker Removal and Stocking on Growth of Fishes in Northern Lakes

AbstractContinued management interest in using White Sucker Catostomus commersonii population manipulations to improve the growth of Northern Pike Esox lucius and potentially competing panfish species provided an opportunity to evaluate White Sucker removal and supplementation in Michigan lakes. Overabundant White Suckers from one lake were transferred into two lakes where higher populations were desired, with fish growth responses being evaluated in each lake and in a control lake pretransfer and at 5 years posttransfer. Criteria for project success were (1) continued low abundance of White Suckers in the removal lake and increased abundance in the recipient lakes; (2) positive growth response of panfish species to White Sucker removals; and (3) positive growth response of Northern Pike to White Sucker additions. After 5 years, White Sucker population abundance and recruitment patterns showed continued survival of stocked adults but little recruitment in stocked lakes and the fish species examined showed no clear positive growth responses to White Sucker manipulations. Fishery managers should carefully consider the costs and benefits of using White Sucker manipulations as a management tool.

First record of the non-indigenous parasitic copepod Neoergasilus japonicus (Harada, 1930) in the Lake Ontario Watershed: Oneida Lake, New York

Four specimens of the Asiatic parasitic copepod Neoergasilus japonicus (Harada, 1930) were collected from Oneida Lake, New York in September 2018; one specimen was from a white sucker Catostomus commersonii, another from a green sunfish Lepomis cyanellus, and two from a bluegill Lepomis macrochirus. The four adult female specimens were found attached to the base of the gills of their respective hosts along with other ergasilid species. The average total length of the adult female N. japonicus specimens we found was 0.609 mm. These detections represent the first known occurrence of this non-native species in the state of New York, extends the easternmost distribution of this parasite over 400 miles, and now includes the Lake Ontario watershed for the first time. It is commonly believed that the international aquaculture industry and aquarium fish trade are the most likely vectors of dispersal for N. japonicus. Monitoring the spread of non-indigenous aquatic species is an important step towards the development of management plans and mitigation efforts with regards to the anthropogenic causes of dispersal, and fish parasites are no exception.

Novel Feed from Invasive Species is Beneficial to Walleye Aquaculture

AbstractCarnivorous fishes, such as the Walleye Sander vitreus, are nutritionally demanding for fish meal. A promising alternative to marine‐origin fish meal, the supply of which has been stagnant in recent decades, is fish meal derived from undesirable freshwater species, such as the White Sucker Catostomus commersonii. To evaluate the relative value of such ingredients, we examined the growth performance of Walleye juveniles. Two dietary treatments were tested: an experimental (EXP) diet that was manufactured using White Sucker as fish meal in comparison with a commercial (COM) diet, EWOS Micro (EWOS Canada, Ltd.). Dietary lipid content was 15.1% and 16.8% for EXP and COM diets, respectively. The protein content was 50.4% and 57.6% for EXP and COM diets, respectively. The energy content was 5,098.76 ± 9.23 cal/g (mean ± SD) for the EXP diet and 5,134.47 ± 10.95 cal/g for the COM diet. Starting at 27 d posthatch, Walleye juveniles (initial weight [mean ± SD] = 0.03 ± 0.008 g; initial length = 15.7 ± 1.5 mm) were reared for 6 weeks in three replicate tanks for each treatment. Condition factor (0.83), final weight (1.12 ± 0.3 g), and weight gain (1.09 ± 0.06 g) were higher in fish that were fed the EXP diet. Similarly, the energetic lipid content of fish in the EXP treatment group (mean ± SD = 5.01 ± 0.45 g/kg) was also higher than that of fish fed the COM diet (3.30 ± 0.53 g/kg). Although the polar lipid content (membrane lipids) was similar in fish from the two treatments, the nutritional ratio for COM juveniles was over 1.5 for arachidonic acid and docosahexaenoic acid, indicating selective incorporation by juveniles and suggesting a potential dietary imbalance of these fatty acids. Furthermore, the higher observed selective incorporation of oleic acid in juveniles fed the EXP diet suggested that a higher value of this fatty acid in the EXP feed could have increased Walleye growth performance. Threonine was the main essential amino acid (AA; &gt;18.5% of total AAs), while serine and glycine contributed the highest percentages of the nonessential AAs (&gt;31% and 8.5% of total AAs, respectively). All three AAs, often considered limiting ingredients, are important to support growth and are involved in metabolic processes in some fish species. Our results demonstrate that feed pellets made with White Sucker fish meal improved growth in Walleye juveniles and can serve as a suitable and probably lower‐cost regional alternative to marine fish meal in feeds for carnivorous fishes.

Influence of river plumes on the distribution and composition of nearshore Lake Michigan fishes

Abstract River plumes form in coastal areas where tributaries mix with their receiving waters. Plume waters are enriched with terrestrial-derived nutrients from their watersheds creating hotspots of biological productivity. The biological importance of plumes scales with the size and persistence of the plume; therefore, large, persistent plumes are more important than small, transient plumes. To date, most studies of plumes have focused on assimilation of terrestrial-derived energy by aquatic species or lower-level food web effects, primarily in marine systems. Few studies have described fish communities near plume habitats and compared them to non-plume areas, especially for the numerous small plumes in the Laurentian Great Lakes. Here we demonstrate that small plumes in the main basin of Lake Michigan enhance local primary productivity and influence distribution and abundance of nearshore Great Lakes fishes. We found that plume fish communities were relatively depauperate and did not support higher biological diversity of fishes compared to non-plume areas. However, individual species including rainbow smelt Osmerus mordax, spottail shiner Notropis hudsonius, and white sucker Catostomus commersonii were more abundant around plumes. Our results demonstrate that small plumes in the main basin of Lake Michigan support highly localized hotspots of biological productivity and fish abundance, primarily within 2 km of river mouths.

Indicators of exposure to estrogenic compounds at Great Lakes Areas of Concern: species and site comparisons

Adverse effects resulting from potential exposure of wild fishes to estrogenic endocrine disruptors were assessed at seven United States Great Lakes Areas of Concern using biomarkers ranging from organismal (gonadosomatic indices) to tissue/plasma (histology, plasma vitellogenin) and molecular (hepatic gene transcripts) levels. Biomonitoring was conducted on pelagic, top predator species, largemouth Micropterus salmoides and smallmouth M. dolomieu bass and benthic, omnivorous white sucker Catostomus commersonii. Seasonal (spring and fall) comparisons were conducted at select sites. Intersex (testicular oocytes), plasma vitellogenin, and hepatic vitellogenin transcripts were commonly observed in bass species. Testicular oocyte severity was positively, although weakly, correlated with plasma vitellogenin, hepatic transcripts of vitellogenin, estrogen receptor α, and estrogen receptor β2, while negatively correlated with androgen receptor β and phosphoenolpyruvate carboxykinase. No testicular oocytes were observed in white sucker; however, plasma vitellogenin and hepatic vitellogenin transcripts were commonly detected in the males. The results demonstrate the importance of utilizing multiple endpoints to assess exposure to estrogenic compounds as well as the importance of choosing sensitive species.

Ratio of Mercury Concentration to PCB Concentration Varies with Sex of White Sucker (Catostomus commersonii)

The whole-fish total mercury (Hg) concentrations were determined in 25 mature female and 26 mature male white suckers (Catostomus commersonii) caught during their spawning run in the Kewaunee River, a tributary to Lake Michigan. The age of each fish was estimated using thin-sectioned otoliths, and total length (TL) and weight were determined for each fish. When adjusted for the effect of age, males were found to be 7% higher in Hg concentration than females. Nearly all (about 98%) of the Hg found in the white suckers was determined to be methylmercury. In an earlier study on the same 51 white suckers from the Kewaunee River spawning run, males were found to be 18% higher than females in polychlorinated biphenyl (PCB) concentration. We determined that the ratio of Hg concentration to PCB concentration in females was significantly higher than that in males. Thus, sex significantly interacted with contaminant type (Hg or PCBs) in determining contaminant concentrations. The most plausible explanation for this interaction was that males eliminated Hg at a faster rate than females, most likely due to the boosting of the Hg-elimination rate by certain androgens such as testosterone and 11-ketotestosterone. Hg concentrations in the white suckers were well below federal guidelines for fish consumption.

A death in the family: Sea lamprey (Petromyzon marinus) avoidance of confamilial alarm cues diminishes with phylogenetic distance.

Alarm signals released after predator attack function as reliable public information revealing areas of high risk. The utility of this information can extend beyond species boundaries, benefiting heterospecifics capable of recognizing and responding appropriately to the signal. Nonmutually exclusive hypotheses explaining the acquisition of heterospecific reactivity to cues suggest it could be conserved phylogenetically following its evolution in a common ancestor (a species‐level effect) and/or learned during periods of shared risk (a population‐level effect; e.g., shared predators). Using a laboratory‐based space‐use behavioral assay, we tested the response of sea lamprey (Petromyzon marinus) to the damage‐released alarm cues of five confamilial (sympatric and allopatric) species and two distantly related out‐groups: a sympatric teleost (white sucker Catostomus commersonii) and an allopatric agnathan (Atlantic hagfish Myxine glutinosa). We found that sea lamprey differed in their response to conspecific and heterospecific odors; exhibiting progressively weaker avoidance of cues derived from more phylogenetically distant confamilials regardless of current overlap in distribution. Odors from out‐groups elicited no response. These findings suggest that a damage‐released alarm cue is at least partially conserved within the Petromyzontidae and that sea lamprey perceives predator attacks directed to closely related taxa. These findings are consistent with similar observations from gastropod, amphibian and bony fish taxa, and we discuss this in an eco‐evo context to provide a plausible explanation for the acquisition and maintenance of the response in sea lamprey.

Modeling White Sucker (Catostomus commersonii) populations to assess commercial harvest influence on age structure

Commercial harvest of White Suckers Catostomus commersonii for bait in the American Lobster Homarus americanus industry is minimally regulated in Maine and there are concerns as to the influence of increasing harvest. We built a population model using parameters (i.e. age-specific mortality, age at maturity, and size-specific fecundity) from literature and field studies to investigate the theoretical effects of harvest mortality on age structure. Because stock-recruitment relations are poorly characterized for this species, we explored the influence of both Beverton-Holt and Ricker recruitment processes. Our base model closely resembled the empirical age structures reported from three unfished lakes in Maine, with four percent of fish in the modeled spawning run being age-10 or older. We assessed the additive effects of harvest mortality on age structure using the full range of possible mortalities. As expected, increased harvest mortality in the model resulted in a decline and disappearance of older age-classes such that few fish greater than age-10 remained in the population under a realistic harvest mortality scenario. This age-truncation was qualitatively comparable to data from aggregate age distributions reported from three commercially harvested lakes in Maine. Because the loss of older fish may compromise population viability, this model is a valuable guidance tool for managers to craft regulation of this growing fishery.

Energy Density and Dry Matter Content in Fish: New Observations and an Evaluation of Some Empirical Models

AbstractEnergy density (ED) is an indicator of fish nutritional status, physiological status, and fitness. Estimates of ED of predators and prey are also needed for bioenergetics modeling, but direct measurements of ED are difficult to obtain. Hence, investigators often borrow published values from the same species or related species. Alternatively, models have been developed that predict ED from dry matter content (DM). The scarcity of published ED values makes data borrowing and the generality of predictive modeling difficult to evaluate. We report new ED measurements derived from bomb calorimetry for six freshwater fish species (Arctic Char Salvelinus alpinus, Brown Trout Salmo trutta, kokanee Oncorhynchus nerka, Lake Trout Salvelinus namaycush, Rainbow Trout O. mykiss, and White Sucker Catostomus commersonii) and compared them to previously published data. We used our data to validate existing ED:DM models and to fit new ones. We also quantified bias that could result from borrowing inappropriate ED values for bioenergetics modeling. We collected a range of fish sizes from two reservoirs of differing productivity and measured whole‐body ED (wet‐mass basis) and DM. Our data substantially increase the range of ED data for Arctic Char, kokanee, and White Suckers. Two multispecies ED:DM models predicted the ED of our samples accurately (mean root mean square error [RMSE] &lt; 500 J/g), even at the extremes for the range of prediction where data used for model development were limited. Taxon‐specific models performed less well (mean RMSE = 775 J/g), and some appeared highly biased (RMSE 956−1,900 J/g). Bioenergetics model simulations showed that Lake Trout prey consumption could be overestimated by as much as 22% when using borrowed EDs for Lake Trout and their prey, but prey consumption estimates fell within ±2% of observed when ED was predicted from DM. When direct measures of ED are unattainable, measurement of DM and prediction of ED from one of the published multispecies models offer a practical and accurate method for bioenergetics modeling and other studies requiring information on fish energy content.

Tumours in white suckers from Lake Michigan tributaries: pathology and prevalence.

The prevalence and histopathology of neoplastic lesions were assessed in white sucker Catostomus commersonii captured at two Lake Michigan Areas of Concern (AOCs), the Sheboygan River and Milwaukee Estuary. Findings were compared to those observed at two non-AOC sites, the Root and Kewaunee rivers. At each site, approximately 200 adult suckers were collected during their spawning migration. Raised skin lesions were observed at all sites and included discrete white spots, mucoid plaques on the body surface and fins and large papillomatous lesions on lips andbody. Microscopically, hyperplasia, papilloma and squamous cell carcinoma were documented. Liver neoplasms were also observed at all sites and included both hepatocellular and biliary tumours. Based on land use, the Kewaunee River was the site least impacted by human activities previously associated with fish tumours and had significantly fewer liver neoplasms when compared to the other sites. The proportion of white suckers with liver tumours followed the same patterns as the proportion of urban land use in the watershed: the Milwaukee Estuary had the highest prevalence, followed by the Root, Sheboygan and Kewaunee rivers. The overall skin neoplasm (papilloma and carcinoma) prevalence did not follow the same pattern, although the percentage of white suckers with squamous cell carcinoma exhibited a similar relationship to land use. Testicular tumours (seminoma) were observed at both AOC sites but not at the non-AOC sites. Both skin and liver tumours were significantly and positively associated with age but not sex.

Habituation of adult sea lamprey repeatedly exposed to damage-released alarm and predator cues

Predation is an unforgiving selective pressure affecting the life history, morphology and behaviour of prey organisms. Selection should favour organisms that have the ability to correctly assess the information content of alarm cues. This study investigated whether adult sea lamprey Petromyzon marinus habituate to conspecific damage-released alarm cues (fresh and decayed sea lamprey extract), a heterospecific damage-released alarm cue (white sucker Catostomus commersonii extract), predator cues (Northern water snake Nerodia sipedon washing, human saliva and 2-phenylethylamine hydrochloride (PEA HCl)) and a conspecific damage-released alarm cue and predator cue combination (fresh sea lamprey extract and human saliva) after they were pre-exposed 4 times or 8 times, respectively, to a given stimulus the previous night. Consistent with our prediction, adult sea lamprey maintained an avoidance response to conspecific damage-released alarm cues (fresh and decayed sea lamprey extract), a predator cue presented at high relative concentration (PEA HCl) and a conspecific damage-released alarm cue and predator cue combination (fresh sea lamprey extract plus human saliva), irrespective of previous exposure level. As expected, adult sea lamprey habituated to a sympatric heterospecific damage-released alarm cue (white sucker extract) and a predator cue presented at lower relative concentration (human saliva). Adult sea lamprey did not show any avoidance of the Northern water snake washing and the Amazon sailfin catfish extract (heterospecific control). This study suggests that conspecific damage-released alarm cues and PEA HCl present the best options as natural repellents in an integrated management program aimed at controlling the abundance of sea lamprey in the Laurentian Great Lakes.

Stress in the neighborhood: Tissue glucocorticoids relative to stream quality for five species of fish

Anthropogenic alterations to terrestrial habitat (e.g., urbanization, deforestation, agriculture) can have a variety of negative effects on watercourses that flow through disturbed landscapes. Currently, the relationship between stream habitat quality and fish condition remains poorly understood. The use of physiological metrics such as glucocorticoids (GCs) provides a useful tool for quantifying these effects by relating the health of resident fishes to stream quality. To date, however, most studies that measure GC levels tend to focus on a single, large-bodied species, rather than evaluating how GCs may be influenced differently between species in a community. In this study, we measured cortisol, the glucocorticoid found in fishes, from fish tissues to quantify effects of habitat degradation on the glucocorticoid function of five species of juvenile and small-bodied stream fish which differ ecologically and phylogenetically. Largemouth bass Micropterus salmoides, brown bullhead Ameiurus nebulosus, white sucker Catostomus commersonii, pumpkinseed Lepomis gibbosus, and logperch Percina caprodes were sampled from a reference and a degraded stream. Upon capture, fish were either euthanized immediately, to quantify baseline stress parameters, or following a standardized stressor, to quantify GC responsiveness. As a result of stream degradation largemouth bass possessed altered baseline GC concentrations and brown bullhead and logperch had altered GC responses to a stressor. White sucker and pumpkinseed did not demonstrate any alteration in baseline or post-stress GC concentrations. Together, our results show that different species residing in identical habitats can demonstrate a variety of responses to environmental stress, highlighting the variation in physiological ability to cope under poor environmental conditions, as well as the difficulty of predicting GC dynamics in wild animals. Understanding the relationships between GC function, habitat quality, and population-level processes will increase the ability of researchers and managers to predict how fish communities and aquatic ecosystems will be shaped by anthropogenic environmental change.

Pathogenesis of spring viremia of carp virus in emerald shiner Notropis atherinoides Rafinesque, fathead minnow Pimephales promelas Rafinesque and white sucker Catostomus commersonii (Lacepede).

Spring viremia of carp (SVC) is a reportable disease to the World Organization of Animal Health (OIE) as it is known to cause significant international economic impact. In Canada, the first and only isolation of SVC virus (SVCV) was in 2006, from common carp Cyprinus carpio L., at Hamilton Harbour, Lake Ontario. The susceptibility of fathead minnow Pimephales promelas Rafinesque, emerald shiner Notropis atherinoides Rafinesque and white sucker Catostomus commersonii (Lacepede) to intraperitoneal injection of the Canadian isolate (HHOcarp06) was evaluated using experimental infection, virus isolation, quantitative reverse transcription polymerase chain reaction (qRT-PCR), histopathology and immunohistochemistry (IHC). Emerald shiner and fathead minnow were most susceptible with 43 and 53% cumulative mortality, respectively, compared with koi at 33%. Quantitative RT-PCR demonstrated that koi had high viral loads throughout the experiment. At 34days post-infection, SVCV was detected from sampled emerald shiner and white sucker in very low titre and was not detected from fathead minnow. Koi, fathead minnow and emerald shiner had gross lesions typical of SVC disease. The histopathological picture was mostly dominated by necrotic changes in kidney, spleen, liver, pancreas and intestine. IHC further confirmed SVCV infection, and staining was largely correlated with histological lesions.