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Efforts to understand the effects of environmental estrogens on fish have shifted away from biochemical indica- tors towards population-level impacts. Ethynylestradiol (EE2) was added to a whole lake at environmentally relevant con- centrations for 3 consecutive years to examine links between vitellogenin (VTG) induction, histopathological impacts, and population decline in four species of fish. VTG induction and histopathological effects in tissues were most severe in fat- head minnow (Pimephales promelas) and pearl dace (Margariscus margarita). VTG was induced to a similar extent in lake trout (Salvelinus namaycush) but less so in white sucker (Catostomus commersonii). There were no histopathological effects in tissues of the two latter species. Population decline occurred in fathead minnows in the second year of EE2 addi- tions and there were some indications of population decline in pearl dace during the third year. White suckers were not af- fected but lake trout declined in year 3. Habitat selection probably altered EE2 exposure and the different effects in each species likely also reflect differing sensitivities. It appears that VTG induction is not sufficient to predict effects of xenoes- trogens on fish populations. However, stronger predictions can be made when VTG induction is assessed in conjunction with histopathological evidence of liver, kidney, and gonad tissue damage. Resume´ : Les efforts pour comprendre les effets des estrogenes de l'environnement sur les poissons se concentrent main- tenant sur les impacts au niveau des populations plutot que sur les indicateurs biochimiques. Nous avons ajoutede l'ethy- nylestradiol (EE2) aun lac entier ades concentrations pertinentes au niveau de l'environnement durant 3 annees consecutives afin d'examiner les liens entre l'induction de la vitellogenine (VTG), les impacts histopathologiques et le de ´- clin de la population chez quatre especes de poissons. L'induction de la VTG et les effets histopathologiques dans les tis- sus sont les plus importants chez la tete-de-boule (Pimephales promelas) et le mulet perle ´ (Margariscus margarita). L'induction de VTG est de niveau semblable chez le touladi (Salvelinus namaycush), mais moindre chez le meunier noir (Catastomus commersonii). Il n'y a pas d'effets histopathologiques dans les tissus de ces deux dernieres especes. Un declin demographique s'est produit chez la tete-de-boule durant la seconde annee des additions de EE2 et il y avait des signes de declin demographique chez le mulet perledurant la troisieme annee. Les meuniers noirs n'ont pas eteaffectes, mais les touladis ont diminuela troisieme annee. La selection des habitats modifie probablement l'exposition aEE2 et les effets distincts chez chaque espece refletent aussi vraisemblablement des sensibilites differentes. Il semble que l'induction de VTG ne suffise pas pour predire les effets des xenoestrogenes sur les populations de poissons. Il est, cependant, possible de faire de meilleures predictions lorsque l'induction de VTG est evaluee conjointement avec les signes histopathologiques de dommages dans les tissus du foie, des reins et des gonades. (Traduit par la Redaction)

We used microsatellite DNA markers to test whether fragmentation of the Trent River (Ontario, Canada) has reduced genetic diversity and increased genetic differentiation among populations of river redhorse ( Moxostoma carinatum ) and shorthead redhorse (Moxostoma macrolepidotum). Allelic richness of both species was significantly greater along the free-flowing Muskegon River (Michigan, USA) than along the fragmented Trent River. Contrary to expectations, there was no evidence of a fragment length effect on genetic diversity, recent population bottlenecks, or increased relatedness among individuals in fragmented populations. High levels of linkage disequilibrium indicate extinction–recolonization population dynamics along the Trent River. For both species, pairwise FSTtests identified weak but statistically significant population differentiation. In the Trent River, differentiation was significantly greater for river redhorse than for shorthead redhorse and, for both species, greater than in the Muskegon River. Moderate fragmentation effects likely reflect the permeability of the dam-lock system to redhorse movement. Differences between species indicate that as a result of smaller effective population sizes, habitat specialists and species at the periphery of their geographic range are more sensitive to river fragmentation.

We used data from a survey of 36 headwater lakes of the Canadian Shield to investigate the relationship between piscivory and growth, abundance, and longevity of white sucker (Catostomus commersoni) and yellow perch (Perca flavescens). The occurrence of northern pike (Esox lucius) and walleye (Sander vitreus) explained variations in the abundance of both white sucker and yellow perch, suggesting strong predation-induced mortality. The longevity of both species tended to be negatively related to increased piscivory. White sucker grew better and had a better condition in lakes with piscivores. Yellow perch showed only small among-lake differences in growth and condition. The superior competitive ability of white sucker over yellow perch could explain why yellow perch did not show improved growth or longevity where population densities were low in lakes with piscivores and white sucker. Furthermore, yellow perch growth was inversely related to the biomass of piscivorous fish in their first year of life. Stomach content data suggest that small yellow perch, which rely on zooplankton, might restrict their use of pelagic resources to reduce their predation risk by piscivores, thus reducing their growth. Our results show that the effects of piscivores can be species-specific and dependent on community structure.

We analyzed data from 79 watersheds in an undegraded U.S. ecoregion to identify key environmental factors that explained stream fish assemblage patterns and to evaluate the relative influence of environmental factors operating at different spatial scales. A few key factors from the watershed, reach, and riparian scale explained a significant amount of the variance in fish attributes. Three environment–fish associations were evident. Top carnivores and intolerant cold-water fishes were associated with relatively narrow, deep, high-gradient, cold streams with strong groundwater inputs. Tolerant cyprinids occurred in small streams with low groundwater input, low dissolved oxygen, and abundant macrophytes. A diverse assemblage (Cyprinidae, Catostomidae, Centrarchidae, Percidae) existed in warm, wide streams in watersheds dominated by lacustrine sand and gravel geology and abundant wetlands and lakes. Overall, reach-scale variables directly explained the most, watershed-scale variables less, and riparian-scale variables the least variation in fish attributes. Watershed and riparian variables had indirect connections with fishes through their direct influence on reach variables. In conjunction with findings from more degraded regions, we conclude that the relative influence of reach-scale variables on fishes are greatest in undegraded areas and that direct effects of watershed-scale variables are increasingly important as human modifications of the landscape increase.

The mitochondrial DNA control region of six cobitids and two catostomids was sequenced and compared with sequences of other cypriniforms to study their sequence variations. The extended termination associated sequence (ETAS) domain, central domain, and conserved sequence block (CSB) domain were partitioned and the ETAS sequence, CSB-D, CSB-E, ECSB-F, CSB1, CSB2, and CSB3 were identified. It is suggested that the "hairpin" TACAT-ATGTA is the key sequence of ETAS and GACATA is the symbol of CSB1. Phylogenetic analysis based on the CSB domain showed that all cyprinids evolved as one monophyletic group, while the non-cyprinid Cypriniformes could be another monophyly that is in accordance with the hypothesis proposed by Siebert. Further analysis of the phylogeny of the Cobitoidei was also conducted and it is tentatively suggested that their relationships are Catostomidae + (Gyrinocheilidae + (Botiinae + (Homalopteridae + (Cobitinae + Nemacheilinae)))).

The goal of this study was to evaluate the response of white sucker (Catostomus commersoni), brook trout (Salvelinus fontinalis), and other fish species to the mass removal of white sucker in five Québec (Canada) lakes. White sucker removal ranged from 14.2 kg·ha–1 to 31.3 kg·ha–1 3 years after mass removal. In four of the study lakes, the proportion of 2+ to 4+ white sucker increased following mass removal. Mean catch and biomass per unit of effort of 1+ brook trout increased significantly in the lakes where white sucker removal was highest. All white sucker populations experienced growth increases after mass removal, and improved brook trout growth was observed in lakes where the most intensive mass removal occurred. These growth increases led to higher mean length at maturity in white sucker females and decreases in mean age at maturity in white sucker males and brook trout males and females. Mean adjusted fecundity significantly increased in white sucker and brook trout in lakes where mass removal was most intense. The present study suggests that white sucker and brook trout exhibit compensatory responses following a reduction of intra- and inter-specific competition and that these responses are related to the intensity of mass removal.

Abundances of eye flukes (Diplostomum spp.) were compared between walleye (Stizostedion vitreum) and white suckers (Catostomus commersoni ) collected in late summer 1997 from Lake St. Louis and Lake St. Pierre, two expansions of the St. Lawrence River in Quebec, Canada. The white sucker, a benthic consumer, was more heavily in- fected than the walleye, a pelagic piscivore, in both lakes. Infection levels increased significantly with host age and size. For both species, abundance of Diplostomum spp. within each age group and length class was higher in fish from Lake St. Louis than in those from Lake St. Pierre. Walleye of all ages and white suckers ♢7 years old from Lake St. Louis were also larger at age than those of corresponding age from Lake St. Pierre. Therefore, walleye and white suck- ers from Lake St. Louis are probably different populations from those in Lake St. Pierre. The higher infection levels in Lake St. Louis are most likely due to the larger number of ring-billed gulls (Larus delawarensis), an important defini- tive host of Diplostomum spp., in colonies in close proximity to that lake; there are >75 000 pairs within 40 km of Lake St. Louis and 16 000 pairs within 40 km of Lake St. Pierre. No detrimental effects of infection with Diplostomum spp. could be detected on fish fork length, body mass, condition index, or gonadosomatic index. Walleye from shallow lentic waters in Lake St. Louis were larger and possessed heavier infections of Diplostomum spp. than those from deeper lotic waters. Walleye collected from a fixed trap near Quebec City in July 1997 were smaller but more heavily infected with Diplostomum spp. than those collected in October, which implies that different populations of fish may be present seasonally at this location. A visual index developed to measure the degree of opacity of the lens of fishes does not appear to be a reliable indicator of levels of infection with eye flukes. Experimental infection of laboratory- raised juvenile ring-billed gulls with metacercariae from the lenses of various fish species collected in the St. Lawrence River demonstrated that metacercariae were primarily Diplostomum indistinctum(84-92%), the remainder being Diplostomum huronense , and this pattern is consistent across host species and localities. 369 Resume : Nous avons compare l'abondance des douves de l'œil (Diplostomum spp.) chez le Dore jaune (Stizostedion vitreum) et le Meunier noir (Catostomus commersoni ), recoltes a la fin de l'ete 1997 dans le lac Saint-Louis et le lac Saint-Pierre, deux elargissements du fleuve Saint-Laurent au Quebec, Canada. Dans chacun des lacs, le Meunier noir, un poisson benthivore, etait plus fortement infecte que le Dore jaune, un predateur pelagique. La gravite des infections augmentait significativement avec la taille et l'âge du poisson hote. Chez les deaux especes, l'abondance de Diplo- stomum spp. dans chaque groupe d'âge et de taille etait plus elevee au lac Saint-Louis qu'au lac Saint-Pierre. Au lac Saint-Louis, chez les dores de tous âges et les meuniers de plus de 7 ans, la taille a un âge donne etait plus elevee que celles des poissons captures au lac Saint-Pierre. Ces resultats suggerent que les Dores jaunes et les Meuniers noirs du Lac Saint-Louis constituent des populations distinctes de celles du lac Saint-Pierre. Il est probable que la variation spa - tiale de la gravite des infections soit attribuable a la repartition des colonies du Goeland a bec cercle ( Larus delawa- rensis), un hote terminal important de Diplostomum spp., alors que plus de 75 000 paires ont ete denombrees dans un rayon de 40 km autour du lac Saint-Louis contre seulement 16 000 paires dans le cas du lac Saint-Pierre. Aucun im- pact negatif de l'infection par la douve de l'œil sur la sante des poissons n'a pu etre mis en evidence par l'examen de

The white sucker (Catostomus commersoni) is a widespread and often abundant North American species. This benthivore can play an important role in the ecology of both fish and benthic communities in lakes and streams. However, the feeding behaviour and ecology of the white sucker have received limited study beyond a description of gut contents from small samples of fish. In this study, the diet of white suckers was determined in relation to season and depth distribution of the fish, as well as to the abundance and type of zoobenthos sampled at the site of fish capture. Suckers fed predominantly on either zoobenthos or zooplankton, with some seasonal variation. They specialized on particular prey and also on the largest individuals within their "speciality," thus exhibiting both resource partitioning and size-selective predation. These findings demonstrate that white suckers can be extremely flexible in their use of resources as opposed to being simple generalist feeders. This attribute, plus their tolerance of a range of environmental conditions, partly explains the abundance of white suckers and their wide distribution in temperate lakes and streams.

The prevalence of lip neoplasms in populations of white sucker (Catostomus commersoni) was compared among five locations in the St. Lawrence River basin, Quebec, Canada. One site in the St. Lawrence River was monitored from May 15 to October 30 for two consecutive years (1994-1995) to study the seasonal variations in the prevalence of lip neoplasms. Other sites were sampled within a few days in October 1995 or May 1996. Lesions were found in fish from four of the five sites. The prevalence at each site varied from 0 to 41.6% and, as found in the Great Lakes, was highest in fish populations from urbanized/industrialized sites. Lip neoplams were detected almost only in fish >350 mm (total length). The prevalence was slightly higher in fish captured in the spring, but the low sample size did not permit statistical detection of this seasonal variation. There was a significant positive correlation (Spearman rs = 0.83) between fish length and the prevalence and size of lesions. The prevalence was similar between sexes, and the condition factor was significantly lower in fish with papillomas from one site only. In future studies, fish size and season of capture should be taken into account to compare the prevalence of lip neoplasms of white sucker from different sites.

We examined the effect of a dam on concentrations of metals (Mn, Cu, Cd, Zn, and Hg) in white sucker (Catostomus commersoni) and in northern pike (Esox lucius). Fish were caught upstream and downstream of the Moses-Saunders Power dam on the St. Lawrence River near Cornwall, Ontario, and Massena, New York. Upstream of the dam, Lake St. Lawrence is a 136-km2 reservoir resulting from the flooding of 90 km2 of agricultural land in 1958, and downstream is Lake St. Francis. In northern pike, no difference in the mean concentrations of metals was found between upstream and downstream fish. Hg concentrations increased with length in upstream and downstream pike, whereas Zn showed an inverse relationship with length downstream. For a particular length, Hg concentration was higher in downstream northern pike. On average, white sucker were five times more contaminated by Hg upstream than downstream. The levels of Mn and Cu were also found to be higher upstream. No bioaccumulation of metals was observed in white sucker. Based on the results obtained for the northern pike, after 37 years, it seems that the high metal concentrations observed in Lake St. Lawrence after the creation of the reservoir have now disappeared. We believe that the high level of contamination of the white suckers in this lake is linked with this species' habit of being in constant contact with the sediments, which could be locally highly contaminated.

A previous study on the effect of pulp and paper effluents on white sucker (Catostomus commersoni), conducted in 1991 and 1992, in both effluent-exposed and reference rivers showed that fish grew faster at downstream sites than at upstream sites. However, in contrast with fish from a reference river, fish exposed to effluent showed no decrease in age or size at first maturity or increase in gonad size or fecundity in response to greater growth. The objective of the present study, conducted in 1993, was to test if differences in measures of growth and sexual maturation between fish populations in exposed and reference rivers would vary from year to year and whether such variation would affect conclusions concerning the effects of pulp mill effluents. Although size at age, fecundity, and age at first maturity varied between the two studies, patterns of demographic responses to pulp mill effluents, relative to reference populations, remained the same, i.e., conclusions about effects of pulp mill effluents did not change despite variation in demographic variables between years and sites. This study reaffirmed the view that only by including the fish populations in a reference river could effects due to bleached kraft mill effluent be separated from effects due to nutrient gradients.

We sampled eggs and larvae of white sucker, Catostomus commersoni, on six spawning grounds to (i) determine the influence of water temperature and discharge on spawning and (ii) assess the reliability of four degree-day equations developed to predict the attainment of organogenesis, eyed egg, hatching, and swim-up phases. We estimated a threshold temperature for spawning of 13°C at four sites and 10°C at two colder sites. A delay of 2 or 3 days was observed between the threshold and the onset of spawning. On average, the degree-day equations predicted the attainment of the developmental phases with an accuracy of 1.6 days, except at the two colder sites, where developmental rates were faster than predicted. The lower spawning temperatures and faster developmental rates observed at the colder sites were interpreted as adaptations to the reduced growing season. Finally, at one site the drift of swim-up larvae occurred over a 6-day period even though spawning lasted 24 days; it was not possible to determine the exact duration of drift at the other sites. This synchronization could be an adaptation lowering the risk of predation on individual larvae, as all the larvae enter the lake within a few days.

I examined variation in egg characteristics among individual females of sympatrically spawning walleye (Stizostedion vitreum) and white sucker (Catostomus commersoni) from Lake Manitoba. White sucker produced eggs of greater dry mass and energy content than walleye. Walleye egg dry mass varied between years and was positively related to both female length and age. The relationship between white sucker egg dry mass and female length varied between years. Egg energy density did not vary with respect to female length in either species. Egg energy density varied between years for walleye but not white sucker. Hatching success of walleye eggs was positively related to female age and negatively related to female length adjusted for age. Length and dry mass of walleye larvae at hatch increased with egg dry mass. Results suggest that the quality of eggs produced by walleye and white sucker populations may vary with the size and age structure of the populations and among spawning years.

We performed laboratory incubations of white sucker (Catostomus commersoni) eggs to determine (i) the incubation time to organogenesis, eyed egg, hatching, and swim-up phases at eight different temperatures (8.5-21.2°C), and (ii) the best model to describe the relationship between these incubation times and temperature. Seven models (degree-day, power-law, B e lehrádek's equation, quadratic equation, first- and second-order exponentials, and a thermodynamic model) all gave comparable and highly significant fits to our data (R2 > 0.90). We thus compared the in situ and predicted incubation times by (i) the degree-day model, because of its simplicity, and (ii) the thermodynamic model, because of its theoretical foundation. The degree-day model was at least as accurate as the thermodynamic model (overall mean difference between predicted and observed incubation times of 1.4 ± 1.0 and 1.2 ± 1.2 days for the thermodynamic and degree-day models, respectively). Given its high accuracy and simplicity of use, we conclude that the degree-day model should be used to predict the incubation times of white sucker. We also observed a synchronization of hatching in situ that suggested an influence of photoperiod in addition to that of water temperature.

Pendant une periode atteignant une duree de 3 ans, on a mesure les concentrations de microcystine-LR (MC-LR) dans l'eau et le phytoplancton ainsi que chez les invertebres et chez deux especes de poissons de 4 lacs du centre de l'Alberta ou le gradient trophique de phosphore total epilimnetique allait de 15 a plus de 500 μg.L -1 . La HPLC du phytoplancton du lac oligomesotrophe n'a pas mis en evidence de MC-LR; la concentration de la toxine cellulaire etait inferieure a 150 ng.L -1 d'eau dans le lac eutrophe-hypereutrophe et elle atteignait 6000 et 11 000 ng.L -1 dans les deux hypereutrophes. Par ailleurs, on a note une forte correlation entre la concentration de MC-LR phytoplanctonique et l'abondance de la cyanobacterie Microcystis aeruginosa et la concentration de microcystine aqueuse, dosee avec une proteine-phosphatase (r = 0,83). On a aussi detecte de la MC-LR chez le zooplancton jusqu'a 67 μg.g -1 de biomasse) et observe une correlation entre les concentrations de MC-LR zooplanctonique et phytoplanctonique (r = 0,69). On a analyse neuf groupes de macroinvertebres, mais la MC-LR n'a ete detecte que chez les gasteropodes jusqu'a 120 μg.g -1 ). La MC-LR semble passer aux invertebres par le broutage. On n'en a pas detecte dans le foie du broche (Esox lucius) et du meunier noir (Catostomus commersoni) preleves dans l'un des lacs ou le phytoplancton est producteur de toxine. La bioconcentation de MC-LR dans les reseaux trophiques aquatiques semble survenir au niveau des consommateurs primaires et il y a probablement transfert de la toxine aux niveaux trophiques plus eleves.

We examined patterns in the spring drift of larval fishes in the Valley River, Manitoba. White sucker (Catostomus commersoni) and walleye (Stizostedion vitreum) were the most common species. The median date of larval drift for walleye was significantly earlier than for all other species. Capture rates of all species were significantly greater during the night than during the day. Larval abundance was positively related to river discharge in the 35 d preceding the median date of larval drift. Larval abundance was also positively related to mature female biomass in Dauphin Lake for walleye, but not for white sucker. Year-class strength of a cohort (catch per unit effort of 3- or 4-year-old fish) in Dauphin Lake was positively related to total larval drift of the same cohort (3 or 4 years earlier) in the Valley River for walleye, but not for white sucker. Our results suggest that the year-class strength of Dauphin Lake walleye is determined very early in the life history and that factors which enhance the natural production of walleye larvae will enhance walleye recruitment.

White sucker, Catostomus commersoni, were sampled from the Rivière des Prairies in the vicinity of Montréal and the upper reaches of the Ottawa River in La Verendrye Park (reference site). Rivière des Prairies fish had lower liver retinol (p ≤ 0.0001) and retinyl palmitate (p ≤ 0.0001) concentrations than fish from the reference site. Rivière des Prairies females and males contained only 9.3 and 30%, respectively, of the vitamin A stores detected in reference fish. Age was an important variable. Covariance analysis revealed that the the rate of retinyl palmitate storage with age was higher (p ≤ 0.0001) for sucker at the reference site. Retinaldehyde was the major retinoid in eggs; however, concentrations were not different between the two sites. The prevalence of malformations was 1.49% among Rivière des Prairies larvae, greater (p ≤ 0.002) than that of the reference group. Eye deformities (i.e., anophthalmia, synopsia) were 11.8 times more prevalent in the Rivière des Prairies larvae. Ethoxyresorufin-O-deethylase (EROD) was greater (p ≤ 0.0003) in the Rivière des Prairies fish. Liver EROD activity in adult females was positively correlated (R = 0.81; p ≤ 0.0004) with the prevalence of deformities of their progeny. Semiquantitative results showed that embryo mortality also tended to increase with EROD activity.

Comment on the origin(s) of a group of parasites requires an awareness of the paleogeology of the region and historical records – phylogenies of both hosts and their parasites. The paleogeology of the Nearctic Region is described briefly and 11 families of Nearctic freshwater fishes for which phylogenetic information is available are considered: Acipenseridae, Polyodontidae, Catostomidae, Ictaluridae, Fundulidae, Poeciliidae, Cyprinodontidae, Percidae, Centrarchidae, Moronidae, and Percopsidae. A previous hypothesis that the Nearctic ancyrocephalids are of mixed origins is supported and the phenomena of vicariance, dispersal, host-switching, and co-evolution are demonstrated.

Prespawning male white sucker (Catostomus commersoni), captured near Jackfish Bay, Lake Superior (exposed to bleached kraft pulp mill effluent (BKME)), and Mountain Bay (reference) were caged in the BKME receiving area for 2, 4, and 8 d. Initially, the hepatic 7-ethoxyresorufin-O-deethylase activity was similar in fish from both BKME and reference sites and, upon BKME exposure, increased 20-fold at both sites after 2 d. The H4IIE cell culture bioassay was used to measure 2,3,7,8-tetrachlorodibenzo-p-dioxin toxic equivalent concentration (TEC) in sucker liver extracts. H4IIE bioassay-derived TECs from Jackfish Bay sucker showed no significant treatment differences; combined TECs for all treatments averaged 51.1 pg∙g−1. Mountain Bay sucker liver TECs were initially significantly less (4.64 pg∙g−1) than the Jackfish Bay TECs but did show a significant, fivefold increase when fish were exposed to effluent. Mountain Bay and Jackfish Bay 8-d BKME-exposed fish showed no uptake of TECs calculated from directly measured polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs) during this exposure. The results suggest that PCDDs and PCDFs are not responsible for the mixed function oxidase induction observed. Handling stress caused rapid reduction of the plasma steroids testosterone and 11-ketotestosterone, confounding any possible BKME effect.

Laboratory-based bioassays were conducted to determine concentrations of sodium-sulfate type salinities that limit the hatching success of several fish species. Survival to hatching (SH) was significantly lower (P

White (Catostomus commersoni) and longnose (C. catostomus) suckers from the Gouin reservoir, Quebec, and a small upstream lake (Lac des Cinq Miles) spawned in the same stream. White suckers numerically dominated the runs in all years; however, abundances of both species decreased eightfold during a year when the reservoir level was lowered for maintenance. Return rates of individuals of both species tagged during the spawning run were poor in the following year, and only a few fish (

Ecology of the parasite fauna of two abundant nongame fish species, Catostomus catostomus (longnose sucker) and Catostomus commersoni (white sucker), from southwestern Lake Superior was examined. White sucker harbored a total of 17 parasite species compared with 8 species in longnose sucker. Echinorhynchus salmonis and Neoechinorhynchus crassus were the most abundant helminths in both sucker species. The only parasitic copepod found in this study, Ergasilus nerkae, was more prevalent in longnose sucker. In white sucker, Glaridacris catostomi, Capillaria catostomi, Ergasilus nerkae, Allocreadium lobatum, and Isoglaridacris bulbocirrus showed fluctuations in prevalence on a seasonal basis. Several helminth species showed a high degree of microhabitat overlap in the gut (e.g., A. lobatum, G. catostomi, and Echinorhynchus salmonis). Helminths that exhibited a higher mean intensity in certain sections of the intestinal tract included I. bulbocirrus in the anterior portion of the gut and Capillaria catostomi in the posterior region of the gut.

The discovery that released hormones (steroids and prostaglandins) and their metabolites function as potent pheromones in some fishes provides an opportunity to determine whether these chemically identified pheromones are species specific. As a first step in studying this complex issue, we used an extracellular electrophysiological recording technique (electro-olfactogram) to investigate the olfactory sensitivity of two sympatrically spawning catostomid species (white sucker, Catostomus commersoni, and longnose sucker, Catostomus catostomus; Cypriniformes: Catostomidae) to steroids and prostaglandins that might function as sex pheromones. Both species were acutely sensitive to F-series prostaglandins, particularly prostaglandin-F2α and its metabolite 15-ketoprostaglandin-F2α, but exhibited no olfactory responses to free or conjugated gonadal steroids. The data from tests of olfactory sensitivity to a range of gonadal steroids, though negative, provide preliminary evidence that maturational steroid hormones do not function as pheromones in catostomids as they do in other cypriniform fishes. We were unable to detect species differences in receptor-level olfactory sensitivity to hormones or hormone metabolites, although we cannot discount possible differences at other levels of the olfactory system.

At least 134 exotic and/or translocated fish species belonging to 34 families which were introduced to 29 of 33 European countries are documented. These include 35 species of Cyprinidae (introduced to 28 countries), 17 Salmonidae (28), 11 Coregonidae (12), 10 Cichlidae (8), six Centrarchidae (23), five Acipenseridae (8), four Ictaluridae (18), four Poeciliidae (11), four Percidae (9), four Mugilidae (1), three Catostomidae (6), three Gasterosteidae (5), two Anguillidae (3), two Atherinidae (2), two Clariidae (4), two Gobiidae (2), two Umbridae (6), two Pleuronectidae (1), two Thymallidae (3) and one species each of Anabantidae (1), Channidae (2), Clupeidae (1), Cobitidae 91), Eleotridae (1), Engraulidae (1), Esocidae (3), Mullidae (1), Osmeridae (1), Percichthyidae (1), Petromyzontidae (1), Polyodontidae (2), Siluridae (5), and Syngnathidae (1). True exotic species amount to 74 species/forms belonging to 21 families, of which 11 families are exotic for Europe. The remaining 60 species (21 families), are native in Europe and were translocated among various watersheds and/or countries. Most species were intentionally released since 1945 to enhance sport, commercial and subsistence fisheries, for fish farming and aquaculture, and for purposes such as mosquito, macrophytes and algal bloom control. Poor success was registered in most cases, along with adverse or unexpected effects on native fishes and their habitat.

Levels of dopamine, serotonin, and noradrenalin were measured in whole brains collected from white sucker (Catostomus commersoni) exposed to increased waterborne levels of copper and zinc associated with mining wastes. Few differences were detected between sites, and these findings are consistent with previous studies that failed to indicate chronic, direct effects of the metals on the white sucker populations. Levels of dopamine and serotonin were higher during postspawning periods than during prespawning or spawning. Noradrenalin levels showed parallel trends, although the differences were not significant owing to higher variability. Serotonin levels showed significant circadian variation at both sites, especially during the spawning season. Dopamine levels also showed circadian fluctuations, but only in females at one site. The results are discussed in relation to the potential use of whole brain amine levels as indicators of contaminant impact.

The activity of the erythrocyte enzyme δ-aminolevulinic acid dehydratase (ALA-D) was measured in 35 catostomids (black redhorse, Moxostoma duquesnei; golden redhorse, M. erythrurum; northern hogsucker, Hypentelium nigricans) collected from three sites on a stream contaminated with Pb-, Cd-, and Zn-rich mine tailings and from an uncontaminated site upstream. Enzyme activity was expressed in terms of hemoglobin (Hb), DNA, and protein concentrations; these variables can be determined in the laboratory on once-frozen blood samples. Concentrations of Pb and Zn in blood and of Pb in edible tissues were significantly higher, and ALA-D activity was significantly lower, at all three contaminated sites than upstream. At the most contaminated site, ALA-D activity was 62–67% lower than upstream. Lead concentrations in the edible tissues and in blood were positively correlated (r = 0.80), whereas ALA-D activity was negatively correlated with Pb in blood (r = −0.70) and in edible tissues (r = −0.59). Five statistically significant relations between Pb and Zn in blood and ALA-D activity were determined. The two models that explained the highest percentage (> 74%) of the total variance also included factors related to Hb concentration. All five significant models included negative coefficients for variables that represented Pb in blood and positive coefficients for Zn in blood. The ALA-D assay with results standardized to Hb concentration represents an expedient alternative to the more traditional hematocrit standardization, and the measurement of ALA-D activity by this method can be used to document exposure of fish to environmental Pb.

A 44-day accelerated storage test at −4 °C was used to evaluate the relative effects of sodium erythorbate, disodium EDTA, and sodium tripolyphosphate on the development of oxidative rancidity in samples of minced sucker. Sensory testing and 2-thiobarbituric acid values were used to evaluate the changes in the samples. Sodium erythorbate was found to inhibit the development of oxidative rancidity as determined chemically and to contribute to maintaining a higher flavor score in the sensory testing.

The occurrence, density, and age-class structure of endemic fish species were compared over a period of 24 months in three Nova Scotia streams of differing pH. The absence of acid-sensitive species and very low densities of fish characterized the stream with a pH range of 4.5–5.0. Fish densities were lower in the stream with a pH range of 4.7–5.4 than in the stream with a pH range of 5.6–6.3. Juvenile salmon and cyprinids were the most abundant species in the least acidic stream. Their densities were considerably lower in the stream with pH levels of 4.7–5.4, and the young age-classes of the cyprinid species were rare or absent. Both salmon and cyprinids were absent in the most acidic stream. In contrast, American eels were most abundant in the two streams with pH levels less than 5.5, and they accounted for an increasingly large proportion of the fish biomass at the lowest pH levels. White sucker was the most abundant species at the lowest pH levels, but its contribution to biomass was unimportant because of the absence of most age-classes older than 0+. Several other species found in the most acidic stream were not very abundant, and old age-classes were usually absent for most of these. The observed distributional patterns were considered to be mostly pH related.

During a study on the parasitofauna of white sucker (Catostomus commersoni) in Laurel Creek, Ontario, three philometrid nematodes were found. Gravid and subgravid females completing the life cycle occurred very infrequently (Philometroides huronensis: 4.3%, Philometroides nodulosa: 1.6%, Philometra kobuleji: 1.1%). In comparison, males and retarded females infected the eyeball and the peritoneum around the swim bladder very often (43.1 and 31.6% in total, respectively). Less frequently, developmental stages were found in the abdominal cavity. Specimens found in the eyeball were identified as belonging to P. nodulosa, while the swim bladder forms could belong to P. huronensis or to P. kobuleji. The eyeball and the peritoneum around the swim bladder are regarded as refuges for retarded forms, where they can survive for more than a year. No evidence was found of a direct cause of retardation.

Fish were surveyed for haematozoa from the central Columbia River, state of Washington, U.S.A., from 1968 to 1978. The 840 individuals examined represented 12 families and 34 species. Most infections occurred in sucker (Catostomidae) and sculpin (Cottidae). Nine species of fish were parasitized by one or two species of haematozoa. Intensities of all detected parasitemias were low, indicating no symptomatic damage to infected hosts.Trypanoplasma salmositica (Katz 1951) was recorded for the first time in white sturgeon (Acipenser transmontanus), largescale sucker (Catostomus macrocheilus), bridgelip sucker (C. columbianus), northern squawfish (Ptychocheilus oregonensis), and sculpin of the Cottus confusus/bairdi complex; it was also found again in prickly (C. asper) and piute (C. beldingi) sculpin. Haemogregarina catostomi Becker 1962 occurred in about 23% each of largescale and bridgelip sucker. Other haematozoa encountered were a haemogregarine in 1 of 23 steelhead (Salmo gairdneri), a haemogregarine in 3 of 92 sculpin (Cottus spp.), and a dactylosome in 1 of 10 American shad (Alosa sapidissima).The sequence of Haemogregarina catostomi occurrence in erythrocytes was the following: young gametocytes in the fall, mature gametocytes in winter, degenerative gametocytes in spring, and absence of infection in summer. The piscicolid leeches Myzobdella lugubris Leidy and Piscicola salmositica Meyer might transmit haematozoa among fish in the survey area.

The fright reaction was found in five species of North American Cyprinidae including the predaceous northern squawfish, and in two species of Catostomidae. The threshold for Cyprinidae is 1/1000 N ("normal") extract or lower, that for Catostomidae at least a 1/100 N extract. The cyprinid species reacted very strongly to extract from other Cyprinidae but less strongly to catostomid extract; catostomid species reacted strongly to extract from other Catostomidae but less strongly to cyprinid extract. Salmon extract did not produce any reaction in Cyprinidae or Catostomidae. The epidermis of all species studied contained alarm substance cells; the epidermis of the Catostomidæ was very similar to that of the Cyprinidae. There was a relationship between number and size of the alarm substance cells (histology) and the quantity of alarm substance in the fish skin (physiology). The ability to respond to the alarm substance first appeared in young redside shiners at an age of 42 days, in young zebrafish at an age of 32 days, when the fish were kept at 26 °C.

The muscle myogens of Catostomus catostomus exhibit polymorphism. Specimens from Great Slave Lake and Babine Lake were homozygous to pattern type A, whereas those from Lake Superior possessed patterns homozygous to A and B as well as the heterozygote AB. Those of C. commersoni, Moxostoma macrolepidotum, M. anisurum, and M. erythrurum were relatively uniform, showing only odd variants. The two specimens of Ictiobus bubalus examined displayed different patterns. Blood hemoglobin patterns of M. macrolepidotum existed in five, M. anisurum in two, and C. commersoni in three polymorphic forms. The number of specimens of I. bubalus, M. melanops, and Carpiodes cyprinus examined was insufficient to assess the existence of polymorphism. Muscle myogen electropherograms of the eight species investigated reflect overall family resemblances, distinctive generic groupings as well as phylogenetic relationships which compare favorably with those in existence. Intergradations might occur upon a more extensive coverage of this family and which might somewhat obscure this overall picture are discussed.

A hematological study was made based on 10 specimens each of the buffalofishes Ictiobus cyprinellus and I. bubalus (Catostomidae). Average results of analyses of selected blood characteristics of I. cyprinellus and I. bubalus, respectively, were: hemoglobin content, 7.8 and 8.5 g/100 ml; erythrocyte count, 1.08 and 1.28 millions/mm2; hematocrit, 34.6 and 32.9%; mean corpuscular hemoglobin, 67 and 64 μμg; and leucocyte count, 23916 and 29004 cells/mm3. Types of leucocytes noted were lymphocytes, neutrophils, "secretory granulocytes," eosinophils, and thrombocytes. No basophils were found. The secretory granulocyte is apparently derived from the neutrophil series. The status of the secretory granulocyte in buffalofishes is discussed with reference to pertinent literature.