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A lineage of the Mountain Sucker species complex (Pantosteus jordani) exists as a genetically and morphologically distinct taxon restricted to the Missouri River basin. This species is thought to be declining throughout its range and is assumed to be extirpated from the southern portion of its distribution. We developed a quantitative PCR‐based environmental DNA assay for P. jordani to help define and monitor its current range. The assay is both specific to P. jordani and sensitive to low amounts of DNA, with a detection limit of 10 DNA copies per reaction. In vitro experiments involved testing DNA from twenty tissue samples, collected from the Missouri River basin in Montana and Wyoming. The assay efficiently detected DNA of all P. jordani samples and did not amplify DNA of any closely related nontarget species. Additionally, 29 environmental DNA samples were taken in 19 waterbodies within P. jordani range and its presence or absence was determined prior to sampling at six of 29 sites. All sites where P. jordani was known absent produced negative results, and all sites where it was known present were confirmed with environmental DNA detections. The new assay was able to detect P. jordani at ten sites which were not previously known to contain individuals, demonstrating that this tool has the potential to rapidly expand the current understanding of this taxon's distribution.

Identification of introduced species can be important to understanding ecological systems and meeting conservation and management goals, but the process can be surprisingly challenging. The Klamath smallscale sucker C. rimiculus seems likely to be native to the Smith River because the drainage separates two basins believed to be within the fish's native range, the Rogue and Klamath rivers. Further, C. rimiculus is broadly distributed in the Smith River and the indigenous Dee-ni' People of the Smith River have a unique word for sucker. However, a historical survey of fishes that described C. rimiculus from the Rogue and Klamath rivers did not include C. rimiculus among the fishes of the Smith River. To determine if the genetic structure of the Smith River C. rimiculus reflects expectations for a native sucker population, we examined variation in microsatellite and mitochondrial genetic markers from the Smith River and surrounding drainages. The genetic analyses revealed a pattern consistent with extreme founder effects in Smith River C. rimiculus, as would be expected from a single introduction of six or fewer effective individuals. The sharing of a high-frequency haplotype between the Smith River and Klamath rivers that is not detected in the Rogue River suggests the Klamath River as the likely source for the introduction. Our findings highlight that local-scale introductions can be easily overlooked because the newly established populations can appear to be parts of contiguous natural distributions. This article is protected by copyright. All rights reserved.

Serial impoundment of major rivers leads to alterations of natural flow dynamics and disrupts longitudinal connectivity. Catostomid fishes (suckers, family Catostomidae) are typically found in riverine or backwater habitats yet are able to persist in impounded river systems. To the detriment of conservation, there is limited information about distribution of catostomid fishes in impounded rivers. We examined the longitudinal distribution of catostomid fishes over 23 reservoirs of the Tennessee River reservoir cascade, encompassing approximately 1600 km. Our goal was to develop a basin-scale perspective to guide conservation efforts. Catostomid species composition and assemblage structure changed longitudinally along the reservoir cascade. Catostomid species biodiversity was greatest in reservoirs lower in the cascade. Assemblage composition shifted from dominance by spotted sucker Minytrema melanops and buffalos Ictiobus spp. in the lower reservoirs to carpsuckers Carpiodes spp. midway through the cascade and redhorses Moxostoma spp. in the upper reservoirs. Most species did not extend the length of the cascade, and some species were rare, found in low numbers and in few reservoirs. The observed gradients in catostomid assemblages suggest the need for basin-scale conservation measures focusing on three broad areas: (1) conservation and management of the up-lake riverine reaches of the lower reservoirs, (2) maintenance of the access to quality habitat in tributaries to the upper reservoirs and (3) reintroductions into currently unoccupied habitat within species' historic distributions. Copyright © 2017 John Wiley & Sons, Ltd.

An understanding of how fish communities differ among river basin, watershed, and stream reach spatial scales and the factors that influence these differences can help in the design of effective conservation programs and the development of reference models that appropriately represent biota under relatively undisturbed conditions. We assessed the heterogeneity among fish assemblages in first- to fourth-order stream sites from four river basins (Savannah, Chattahoochee, Cape Fear, and Pee Dee rivers) within the Sand Hills ecoregion of the southeastern USA and compared it with the heterogeneity associated with watershed and stream reach spatial scales. Fifty-five species of fish representing 15 families were collected by electrofishing, with the most speciose families being Cyprinidae, Centrarchidae, Percidae, Ictaluridae, and Catostomidae. Constrained ordination identified clearly demarcated species assemblages among river basins as well as subbasin environmental variables that affected fish specie...

Summary 1. Local assemblage structure, from a deterministic perspective, is presumably dictated by the regional species pool as well as regulated by local factors. We examined the relationships of the regional species pool and local hydrological characteristics to local species richness of North American freshwater fishes using data sets collected during the National Water Quality Assessment program conducted by the United States Geological Survey. 2. We predicted that local species richness is ultimately constrained by the composition of the regional species pool and further associated with local hydrological factors. Moreover, we predicted that variation in local species richness within major families can be explained by different combinations of hydrological characteristics that represent lineage-specific responses to the environment. 3. Daily discharge and regional and local species richness data were assembled from 41 stream localities across the United States. Multiple stepwise regressions were conducted to predict local species richness, based on regional species richness, mean discharge and hydrological characteristics quantified by nine variables characterising flow variability. Species richness at each site was calculated for the entire assemblage as well as within the four most species-rich families in the data set (Catostomidae, Centrarchidae, Cyprinidae and Percidae). 4. Local species richness was best predicted by a combination of regional species richness and discharge magnitude when all species were considered. Regional species richness was a significant explanatory variable of local species richness for three of four families (Catostomidae, Centrarchidae, Cyprinidae), but not for Percidae. Local richness in Centrarchidae and Cyprinidae was positively correlated with temporal flow variability as well as high and low flow duration, respectively, while richness in Catostomidae and Percidae tended to be associated with discharge volume. In addition, local species richness for three of the four major families was positively correlated with species richness of the other families in the assemblage, potentially suggesting the influence of local habitat quality and heterogeneity. 5. Results suggest the importance of the combined influences of the regional species pool and local hydrological characteristics on local richness in freshwater fishes, with variation in richness within each family predicted by different characteristics of flow regimes.

Although the gill-arch osteology of Cypriniformes has been well studied, comparable works on gill-arch musculature are scarce. The focus of previous studies has been on Cyprinidae while other families have received little or no attention. Consequently, generalizations for Cypriniformes have been made from the musculature of cyprinid gill-arches. This study describes the gill-arch musculature of a catostomid, the quillback Carpiodes cyprinus, and demonstrates that there are striking differences in the overall gill-arch musculature of catostomids in comparison to cyprinids, especially in the dorsal gill-arch region. Of the 23 muscles found in the dorsal gill-arch region of cyprinids, only 13 were present in C. cyprinus. Muscles that are absent include adductores 1–5, levator internus 4, levator ceratobranchialis 5 accessorius, retractor ceratobranchialis 5 externus, retractor ceratobranchialis 5 internus, and the retractor ceratobranchialis 5 transversus. In the ventral gill-arch region, the rectus communis is absent. The derived scrolling shape of the dorsal gill-arch skeleton associated with food processing is likely related to the change in musculature. J. Morphol., 2012. © 2012 Wiley Periodicals, Inc.

Robust redhorse (Moxostoma robustum) and notchlip redhorse (M. collapsum) are two species of redhorses that reside in the lower Oconee River, Georgia. Robust redhorse is listed as a state endangered species in Georgia and North Carolina, and attempts to investigate factors affecting its reproductive success have met with limited success. Therefore, catch of robust redhorse young were combined with catch of notchlip redhorse to increase sample size. These congeners with similar spawning repertoire were assumed to respond similarly to environmental conditions. River discharge during spawning and rearing seasons may affect abundance of both redhorses in the lower Oconee River. An information-theoretic approach was used to evaluate the relative support of models relating abundance of age 0 redhorses to monthly discharge statistics that represented magnitude, timing, duration, variability and frequency of river discharge events for April through June 1995–2006. The best-approximating model indicated a negative relationship between the abundance of redhorses and mean maximum river discharge and the number of high pulses during June as well as a positive relationship with intermediate duration of low flows during April–June. This model is 9.6 times more plausible than the next best-fitting model, which revealed a negative relationship between the abundance of redhorses and mean maximum river discharge during May and the number of high pulses during June as well as a positive relationship between abundance and intermediate duration of low flows during April–June. Management implications from the results indicate low-stable flows for at least a 2-week period during spawning and rearing may increase reproductive success of robust and notchlip redhorses. Copyright © 2012 John Wiley & Sons, Ltd.

Catostomids 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 & Sons, Ltd.

Aim We evaluated variation in fish assemblages on the basis of taxonomic composition and functional groups based on Pleistocene glacial boundaries in the Ohio River basin. We tested for the influence of habitat and hydrology on fish assemblage variation. Location Ohio River basin of North America, including the states of Ohio, Indiana and Illinois. Methods Fish collection sites were identified as Wisconsinan, pre-Wisconsinan or unglaciated regions. Multivariate analyses, multi-response permutation procedures, discriminant analysis and indicator species analyses were used to test whether taxonomic and functional assemblages were distinct among regions with varying glacial histories. Principal components analysis was used to identify habitat and water quality, as well as hydrological gradients that could be discerned by glacial region. Results We identified significant differences in both taxonomic and functional fish assemblage structure and habitat variation among regions that had different glaciation histories. The largest differences in taxonomic and functionally based fish communities were for unglaciated and pre-Wisconsinan regions, while unglaciated and Wisconsinan regions were most similar. We correctly classified study regions in 71% and 60% of sites using taxonomy and functional analyses, respectively. Wisconsinan sites were characterized by Cyprinidae and Catostomidae assemblages with high abundances of tolerant fishes that tended to occur in habitats with reduced current velocity. Pre-Wisconsinan sites were characterized by Cyprinidae, Catostomidae, Centrarchidae and Percidae families with increased abundances of intolerant fishes that tended to occur in habitats with coarser substrates and increased water velocity in streams of varying size. Unglaciated sites were characterized by Cyprinidae and Percidae families and were not closely associated with any habitat-based functional group. Habitat in the unglaciated and pre-Wisconsinan sites was significantly different from that in the Wisconsinan sites, which were characterized by increased channel structure and reduced stream size. Main conclusions Pleistocene glaciation events formed a lasting template of predictable regional differences in stream habitat and in the corresponding taxonomic and functional fish assemblage structures. While many factors impact the distribution of fishes, these results suggest that historical influences such as glaciation may be used to further explain the underlying mechanisms of spatial variation in fish assemblages.

Kreitzer JD, Belk MC, Gonzalez DB, Tuckfield RC, Shiozawa DK, Rasmussen JE. Ontogenetic diet shift in the June sucker Chasmistes liorus (Cypriniformes, Catostomidae) in the early juvenile stage. Ecology of Freshwater Fish 2010: 19: 433–438. © 2010 John Wiley & Sons A/S Abstract – Ontogenetic diet shifts are common in fishes and often occur during early life stages. The larval and early juvenile period is critical in the life cycle of the endangered June sucker, Chasmistes liorus (Teleostei: Catostomidae). High larval and juvenile mortality leads to low recruitment to the breeding population and hence a declining natural population. To understand diet composition and dynamics in June sucker at early life stages, diet was quantified and compared to available food items in the natural environment during the early juvenile stage. Rotifers (Brachionus sp.) were the primary diet item at week 10, but by week 12 a small cyclopoid copepod (Microcyclops rubellus) became predominant. Availability of diet items varied little across the experimental period. The increase in size of young suckers may explain this rapid dietary shift, but there are some inconsistencies with the size selection argument. This diet shift represents an important nutritional change that should be considered in development of diets for young June sucker and in assessing suitability of nursery habitats.

Stream fish managers often use fish sample data to inform management decisions affecting fish populations. Fish sample data, however, can be biased by the same factors affecting fish populations. To minimize the effect of sample biases on decision making, biologists need information on the effectiveness of fish sampling methods. We evaluated single-pass backpack electrofishing and seining combined with electrofishing by following a dual-gear, mark–recapture approach in 61 blocknetted sample units within first- to third-order streams. We also estimated fish movement out of unblocked units during sampling. Capture efficiency and fish abundances were modeled for 50 fish species by use of conditional multinomial capture–recapture models. The best-approximating models indicated that capture efficiencies were generally low and differed among species groups based on family or genus. Efficiencies of single-pass electrofishing and seining combined with electrofishing were greatest for Catostomidae and low...

Skeletal elements of the gill arches of adult cypriniform fishes vary widely in number, size, and shape and are important characters in morphologically based phylogenetic studies. Understanding the developmental basis for this variation is thus phylogenetically significant but also important in relation to the many developmental genetic and molecularly based studies of the early developing and hence experimentally tractable gill arches in the zebrafish, a cyprinid cypriniform. We describe the sequence of the chondrification and ossification of the pharyngeal arches and associated dermal bones from Catostomus commersonii (Catostomidae, Cypriniformes) and make selected comparisons to other similarly described pharyngeal arches. We noted shared spatial trends in arch development including the formation of ventral cartilages before dorsal and anterior cartilages before posterior. Qualitatively variable gill arch elements in Cypriniformes including pharyngobranchial 1, pharyngobranchial 4, and the sublingual are the last such elements to chondrify in C. commersonii. We show that the sublingual bone in C. commersonii has two cartilaginous precursors that fuse and ossify to form the single bone in adults. This indicates homology of the sublingual in catostomids to the two sublingual bones in the adults of cobitids and balitorids. Intriguing patterns of fusion and segmentation of the cartilages in the pharyngeal arches were discovered. These include the individuation of the basihyal and anterior copula through segmentation of a single cartilage rod, fusion of cartilaginous basibranchials 4 and 5, and fusion of hypobranchial 4 with ceratobranchial 4. Such “fluidity” in cartilage patterning may be widespread in fishes and requires further comparative developmental studies. J. Morphol., 2009. © 2008 Wiley-Liss, Inc.

An important issue surrounding biomonitoring in large rivers is the minimum sampling effort required to collect an adequate number of fish for accurate and precise determinations of biotic condition. During the summer of 2002, we sampled 15 randomly selected large-river sites in southern Idaho to evaluate the effects of sampling effort on an index of biotic integrity (IBI). Boat electrofishing was used to collect sample populations of fish in river reaches representing 40 and 100 times the mean channel width (MCW; wetted channel) at base flow. Minimum sampling effort was assessed by comparing the relation between reach length sampled and change in IBI score. Thirty-two species of fish in the families Catostomidae, Centrarchidae, Cottidae, Cyprinidae, Ictaluridae, Percidae, and Salmonidae were collected. Of these, 12 alien species were collected at 80% (12 of 15) of the sample sites; alien species represented about 38% of all species (N = 32) collected during the study. A total of 60% (9 of 15) of...

The genetic variation, phylogeny and biogeography of catostomid fishes were investigated based on mitochondrial cytochrome b and nuclear 18S-ITS1-5.8S DNA sequences. The pair-wise genetic distance of cytochrome b for 17 catostomids varied considerably, from 1.00% (Chasmistes brevirostris and Deltistes luxatus) to23, 3%(Cycleptus elongatus and Moxostoma anisurum). The size of the 18S-ITS1-5.8S sequence ranged from 315 bp (Moxostoma robustum) to 575 bp (Ictiobus cyprinellus). The 18S-5.8S region was conservative and the length of ITS1 regions was found to vary considerably among the seven catostomids. It is interesting that the primitive I. cyprinellus and Myxocyprinus asiaticus had longer ITS1 regions than suckers from the Catostominae. Based on the nucleotide substitution model, the nuclear 18S-5.8S gene had a faster evolution rate than the mitochondrial cytochrome b gene. In a phylogenetic analysis, 17 catostomids from 14 genera representing three subfamilies were not distinctly divergent. Nevertheless, three major genetically divergent clades were identified. Clade I (95% bootstrap) included general Catostomus, Thoburnia, Xyrauchen, Chasmistes and Deltistes. Clade II (94% bootstrap) included Hypentelium, Moxostoma and Scartomyzon. Clade III (77% bootstrap) was a monophyletic Ictiobinae containing I. cyprinellus and Carpiodes carpio. The biogeography of old world catostomids followed a disperse event, and the speciation of the extant catostomids was a vicariance event. The earliest catostomid evolved in Asia from one branch of ostariophysans in the early Tertiary. Before the Eocene, catostomids belonging to the genus Amyzon had a wide, trans-Pacific distribution over Asia and North America. Later, oceanic ingression and the Tertiary glacial event forced catostomids to evolve on both mainlands, respectively. The present disjunct distribution pattern of catostomids was presumably due to competitive pressure from cyprinids, geographical events, their Late Cenozoic radiation in North America and glacial events. The divergence time based on the mitochondrial and nuclear DNA sequences suggests that catostomids began to diverge in the early or mid-Miocene, which agrees with the fossil evidence.

Spawning aggregations of five species of catostomids were observed on the two mid-channel gravel bars of the Savannah River, Georgia and South Carolina, in 2004 and 2005 to assess the degree of spatial and temporal overlap in the use of this habitat and determine the habitat preferences leading to segregation. Spawning catostomids showed a considerable amount of temporal overlap in their use of these mid-channel gravel bars. The observed temporal overlap was consistent between 2004 and 2005 and corresponded to temperatures at which species were present. The distribution of catostomids was not uniform at the upstream gravel bar. Carpsuckers Carpiodes sp., spotted sucker Minytrema melanops and robust redhorse Moxostoma robustum both demonstrated some spatial overlap with notchlip redhorse Moxostoma collapsum; however, their overall distributions were different from one another. Northern hogsucker Hypentelium nigricans was present across the gravel bars, apparently as an egg predator. Spawning catostomids segregated based on flow, depth, slope and substratum size. Whether due to limited habitat availability or changes in the timing of reproduction due to altered cues, temporal and spatial overlap occurs between spawning catostomids despite the apparent partitioning of available spawning habitat. It is unclear, however, if this overlap results in excessive mortality in the early life-history stages of these species. Results suggest spatial overlap among catostomid species was minimized due to species spawning in areas within a narrow range of conditions. Intraspecific interactions such as nest site superimposition or disturbance may be a concern.

Cypriniformes (which includes the minnows, carps, loaches, algae-eaters, stone loaches, and suckers) is a morphologically diverse and incredibly speciose order of teleosts. It has been suggested that a number of evolutionary innovations, key to improved hearing and feeding, have played an important role in cypriniform fishes' success. One such innovation, the Weberian apparatus, is a novel assemblage of vertebral elements and modified ribs that relay and amplify sound pressure changes from the gas bladder to the inner ear. The Weberian apparatus unites Cypriniformes with other major orders into an extremely species-rich group of fishes, the Otophysi. Together, otophysan fishes comprise one of the largest groups of fishes in the world, as well as the majority of freshwater fishes. Here we present a detailed comparison of the Weberian apparatus in a number of cypriniform families using cleared and stained specimens. We present data regarding inter- and intrafamilial morphological variation within Cypriniformes. With few, but evolutionarily important, exceptions we find that diagnostic features of the Weberian apparatus characterize each family. Interspecific variation within each of the families Balitoridae, Gyrinocheilidae, and Catostomidae is only slight, whereas variation among subfamilies within Cyprinidae and Cobitidae is far more significant. This comparative study identifies a number of distinct morphologies, some of which appear highly correlated with ecological niche. For example, inhabiting swift-moving waters appears to be a key factor in the encapsulation of the anterior gas bladder in some cobitids, balitorids, and gobionin cyprinids. J. Morphol., 2007. © 2007 Wiley-Liss, Inc.

The Native Fishes Work Group, formed in 1991, developed and implemented a protocol to enhance the dwindling razorback sucker population in Lake Mohave, Arizona-Nevada. This large, genetically diverse population is severely reduced in size as a result of recruitment failure associated with predation on larvae. To circumvent this problem, wild larvae are captured, reared in protective custody until they are large enough to escape predation, and then released back into the lake. We present results of a monitoring program designed to assess the effectiveness of the sampling design in transmitting the high genetic diversity found in wild adults. Variation in a fragment from the mitochondrial DNA gene cytochrome b was examined by analysis of single-stranded polymorphisms and direct sequencing. Samples were characterized from three life history stages. Characterization of wild adults verified previous results that identified considerable diversity and provided baseline data. Samples of larvae from several temporal collections from throughout the spawning season and four geographical areas were characterized for 7 years (1997–2003) to assess the transmission of genetic variation from wild adults to larvae. Several analyses identified significant differences among temporal collections, resulting from sampling errors associated with finite number of females spawning at a given time and place. Comparisons among areas and years failed to identify significant variation, indicating that pooled collections for each year possess the same levels and patterns of genetic variation. Examination of repatriates representing 11 years (1992–2002) also failed to identify significant differences among cohorts; however, some sample sizes were small and the AMOVA may lack sufficient power to detect differences. Contrasts of wild adults, larvae, and repatriates identified statistically significant differences among collections within these three groups; however, levels of variation are small and not biologically meaningful. More importantly, this analysis failed to detect significant differences among adults, larvae, and repatriates indicating that the program has been achieving its goal of transmitting variation from adults through the larvae and into the repatriate population. The reproductive capability of repatriates has not been examined, so it is unknown if the program will maintain genetic variation found in the original adult population. This will be most easily achieved by periodic monitoring of genetic variation in larval samples. If levels of variation become reduced in repatriates, levels and patterns of diversity in larvae are also expected to become reduced, and deviations in estimates of genetic diversity may become larger and more frequent. If this is the case, intervention may be necessary to ensure that certain individuals are not over-represented in the repatriate population.

Catostomidae represent an important family of freshwater fishes mainly distributed in North America, but also found in Eurasia. This paper describes the development of microsatellite DNA markers for a highly threatened member of this family, the Copper redhorse (Moxostoma hubbsi), as well as cross-catostomids amplifications. 168 tetra-nucleotide loci were screened to develop 21 polymorphic markers, with an average number of 8.5 alleles per locus and observed heterozygosity ranging between 0.52 and 1.00. Successful amplification was obtained for 12 other members of the family at between seven to 19 loci, with between two to 18 loci being polymorphic per species.

The pulsed, high-velocity water flow characteristic of water-flow patterns downstream from hydropower-generating dams has been implicated in the declining abundance of both aquatic insects and fishes in dam-regulated rivers. This study examined the effects of 0, 4, and 12 h per day of pulsed, high-velocity water flow on the egg mortality, hatch length, final length, and survival of larval robust redhorse Moxostoma robustum, a presumedly extinct species that was rediscovered in the 1990s, and V-lip redhorse M. collapsum (previously synonomized with the silver redhorse M. anisurum) over a 3–5 week period in three separate experiments. Twelve 38.0-L aquaria (four per treatment) were modified to simulate pulsed, high-velocity water flow (>35 cm/s) and stable, low-velocity water flow (

The flannelmouth sucker Catostomus latipinnis is one of the few native fish that persists in the lower Colorado River basin. Little is known about the effects of hypolimnetic releases of cold, swift water from Colorado River dams on flannelmouth sucker populations. We conducted fatigue velocity tests on age-0 flannelmouth suckers in the laboratory to evaluate the effects of water temperature and fish size on swimming ability. Fish of 25-114 mm total length (TL) were subjected to incremental increases in water velocity until the upper limit of their swimming ability was reached. Swimming tests were conducted at 10, 14, and 20°C. Swimming ability increased with fish length and was directly related to water temperature at all fish sizes. A decrease in water temperature from 20°C to 10°C resulted in an average decrease in swimming ability of 40%. Mean swimming ability of wild-caught flannelmouth suckers was 7 cm/s higher than that of captive-reared flannelmouth suckers of similar size at 20°C and 14°...

In this paper, we summarize aspects of the life history of mountain suckers Catostomus platyrhynchus in Lost Creek Reservoir, Utah, and compare our findings with populations in two Montana streams as reported in the only detailed life history paper on the mountain sucker previously published. Mountain suckers in Lost Creek Reservoir, Utah, grew faster than did populations in Flathead Creek and East Gallatin River, Montana, reaching a mean total length (TL) of 64 mm at the end of their first growing season and 193 mm by the end of their sixth season. They migrated from the reservoir and spawned in Lost Creek from late May until the end of June when water temperature was 9-11°C. The shortest mature male was 115 mm TL; the shortest mature female was 143 mm. Fecundity was correlated to female total length (1,163 eggs for a 130-mm fish to 2,730 eggs for a 180-mm fish) and weight (1,327 eggs for a 26-g fish to 2,900 eggs for a 75-g fish). Fecundity was greater for fish from Lost Creek Reservoir than fo...

A study was conducted with endangered the razorback sucker (Xyrauchen texanus) to determine if environmental exposure to selenium in flooded bottomland sites affected survival, growth, and egg-hatching success. Adults were stocked at three sites adjacent to the Colorado River near Grand Junction, Colorado, in July 1996: hatchery ponds at Horsethief Canyon State Wildlife Area (referred to here as Horsethief; the reference site), a diked tertiary channel at Adobe Creek, and North Pond at Walter Walker State Wildlife Area (WWSWA). Fish were collected in April 1997 and spawned. After two spawnings adults from the three sites were held at Horsethief for an 86-day selenium depuration period. Selenium concentrations at Horsethief were 1.4–3.0 μg/L in water, 0.8–0.9 μg/g in sediment, 4.5 μg/g in muscle plug, and 6.0 μg/g in eggs; at Adobe Creek

Testosterone induced papillomata in 85% (11/13) of initially non-papillomatous white suckers Catostomus commersoni and increased papillomata growth in 100% (16/16) of initially papillomatous suckers. 17β-oestradiol induced papillomata in 83% (10/12) of initially non-papillomatous suckers and increased papillomata growth in 100% (16/16) of initially papillomatous suckers. Less than 29% (4/14) of white suckers injected with tamoxifen developed papillomata, while complete papillomata regression was observed in 71% (10/14) of initially papillomatous suckers. In control groups 59% (27/46) of suckers either retained or developed papillomata and 27% (6/24) of suckers exhibited tumour regression. Protein kinase C (PKC) activity was significantly depressed and ornithine decarboxylase (ODC) activity was significantly elevated in steroid-treated papillomata v. normal lip epidermis. ODC activity was significantly depressed in tamoxifen-injected, regressing papillomata. There were no significant differences in plasma oestrogen and testosterone levels between papillomatous and non-papillomatous female fish from a site contaminated with persistent organic chemicals and an uncontaminated reference site. Similarly, no significant differences in testosterone and 11-ketotestosterone levels were observed between papillomatous and non-papillomatous male fish.

Tapeworms in the genus Ligula are cosmopolitan parasites whose plerocercoid stages are found worldwide in fishes of the families Cyprinidae and Catostomidae. Examination of chiselmouth Acrocheilus alutaceus, northern pikeminnow Ptychocheilus oregonensis, and bridgelip sucker Catostomus columbianus revealed the presence of Ligula in the lower Crooked River system of central Oregon. This represents the first report of Ligula intestinalis in two of these host species: chiselmouth and bridgelip sucker. Although most hosts appeared healthy, large external lesions were noted on some bridgelip suckers in close association with a Ligula plerocercoid. The largest plerocercoid recovered was 101.5 cm relaxed length and may represent the longest plerocercoid of Ligula reported from North America.

Utah Lake, Utah, U.S.A. harbours an endemic catostomid fish, the June sucker Chasmistes liorus, that is recognized as being endangered. Since 1981, post-1935 representatives of the June sucker have generally been considered to be examples of a self-propagating hybrid. Utah Lake has contained another endemic catostomid, the webug sucker Chasmistes fecundus that was regarded as a true species until 1981 when it was judged to be an extirpated sterile hybrid. Since then, fisheries biologists have not attempted to identify it. This review makes a comparative examination of the published descriptions of the internal and external anatomy of these two species, plus the third catostomid of Utah Lake, the Utah sucker Catostomus ardens. The Utah sucker purportedly crossed with a form of the June sucker that has supposedly since been expunged, to produce hybrids. On the basis of comparative morphology and the consideration of temporal changes in the habitat and piscifauna of Utah Lake, the authenticity of supposed hybridism in the webug sucker, and in the contemporary June sucker, is analysed. The conclusion is reached that there is insufficient evidence to deem these taxa hybrids, or the webug sucker, extinct.

Herein we describe the development of microsatellite markers for five Catostomid species: Catostomus snyderi , Catostomus rimiculus , Chasmistes brevirostris , Deltistes luxatus , and Catostomus occidentalis . A total of 89 primer pairs were developed from enriched (CA) n and (GATA) n libraries created from the D. luxatus genome. The successful amplification of 82 polymorphic loci across three Catostomid genera indicates that the microsatellite markers described in this study will be broadly applicable.

Flannelmouth sucker, Catostomus latipinnis, a fish endemic to the Colorado River basin in the western United States, appears to experience poor recruitment to adult size in the Colorado River, downstream of Glen Canyon Dam. Lack or impermanence of rearing areas for young-of-year (YOY) fish is hypothesized to be the problem. Knowing the importance of tributary mouths as rearing areas in other river systems, we studied use of the mouth of the Paria River, a tributary of the Colorado River, by YOY flannelmouth suckers, and the availability of rearing area in the mouth at different flow levels in the Colorado River in 1996 and 1997. We also examined the relationship between flash floods in the Paria River and catch-per-unit-effort (CPUE) of YOY in the Paria River between 1991 and 1996. Maximum mean daily discharge in the Paria River was inversely correlated with CPUE of YOY flannelmouth suckers (Spearman Rho=−0.9856, p=0.0003) during their critical rearing period (15 March–30 June). Thus, it appears that YOY flannelmouth suckers rear longer in the Paria River in years when flash flooding is minimal. Recruitment of YOY flannelmouth suckers at the Paria River may also be improved by enhancing pool formation during spring and summer rearing seasons. YOY flannelmouth sucker was captured in a pool created by high Colorado River flows (≥336 m3/s) that inundated the mouth of the Paria River during spring and summer, 1996. In 1997, high flows (about 550–750 m3/s) in the Colorado River during winter and spring initially inundated the Paria River and formed a pool in the mouth. However, these high flows eventually caused 0.5–1.0 m of suspended sediment from the incoming Paria River to deposit in the mouth. Thus, despite higher flows than 1996, the slackwater area formed only occasionally in 1997. Differences in pool formation between 1996 and 1997 demonstrate that pool formation cannot be inferred solely from Colorado River flows. Copyright © 2001 John Wiley & Sons, Ltd.

The distribution of estuarine and freshwater fish species caught during the Swedish-Russian Expedition Tundra Ecology-94' is presented. Thirteen sites along the Russian part of the Arctic Sea coast were sampled and a total of 21 fish species of the families Salmonidae, Coregonidae, Thymallidae, Osmeridae, Cyprinidae, Catostomidae, Balitoridae, Gadidae, Gasterosteidae, Percidae, Cottidae, Pleuronectidae were recorded. Some records were new to particular basins.

Analyses of biomarkers in fish were used to evaluate exposures among locations and across time. Two types of references were used for comparison, an upstream reference sample remote from known point sources and regional exposure criteria derived from a baseline of fish from reference sites throughout Ohio, USA. Liver, bile, and blood were sampled from white suckers (Catostomus commersoni) and common carp (Cyprinus carpio) collected during 1993 and 1996 in the Ottawa River near Lima, Ohio. Levels of exposure were measured for petroleum by naphthalene-type metabolites, combustion by-products by benzo[a]pyrene-type metabolites, coplanar organic compounds by ethoxyresorufin-O-deethylase (EROD) activity, and urea by blood urea nitroger (BUN) levels. The four biomarkers analyzed proved effective in determining differences between reference and polluted sampling sites, between geographically close (

A methodology was developed for deriving quantitative exposure criteria useful for comparing a site or a watershed to a reference condition and for defining the occurrence of extreme exposures. The prototype method used indicators of exposures to oil contamination and combustion by-products, naphthalene (NAPH)-type and benzo[a]pyrene (BaP)-type biliary metabolites from white suckers (Catostomus commersoni). The fish were collected from first- to third-order streams in the Regional Environmental Monitoring Assessment Program (REMAP) study of the Eastern Corn Belt Plains ecoregion at randomly selected sites and from third- or higher-order streams in conjunction with the Ohio Environmental Protection Agency (OEPA) Biomonitoring Program, which sampled sites of concern and reference sites selected by ecologists. The polycyclic aromatic hydrocarbon metabolites were measured using fixed-wavelength fluorescence with excitation/emission pairs at 290/335 nm for NAPH-type and 380/430 nm for BaP-type metabolites. Exposure criteria values were selected for each type of metabolite for both the REMAP study and the OEPA reference sites following the recommendations of the International Federation of Clinical Chemistry. Exposure criteria derived for each metabolite were not significantly different for REMAP and OEPA reference sites. More than one half of the OEPA nonreference sites were found to be contaminated, exceeding criteria values for both types of metabolites. This method for finding meaningful exposure criteria can be used to develop criteria of exposure to other contaminants for other wildlife and other ecosystems.

The robust redhorse Moxostoma robustum occurs in an 85-km stretch of the Oconee River, Georgia, downstream of a hydropower dam. The population consists primarily of older individuals and recruitment in recent years has been minimal. Operation of the hydropower dam may have affected recruitment negatively by displacing newly hatched larvae downstream and away from nursery habitats. Our null hypothesis was that larval robust redhorse can tolerate water velocities that occur in the Oconee River during peak river discharge related to hydropower generation. We measured swimming speeds for three size-classes of larvae (means: 13.1, 16.2, and 20.4 mm total length) and modeled low-velocity habitat (i.e., as defined by larval swimming speeds) in the Oconee River. We used logistic regression to calculate prolonged swimming speeds (i.e., water velocity at which 50% of fish failed to swim for 1 h) for each size-class and to predict the proportion of larvae in the water column that could maintain their positi...

We conducted two 90 day chronic toxicity studies with two endangered fish, razorback sucker and bonytail. Swim-up larvae were exposed in a reconstituted water simulating the middle Green River. The toxicant mixture simulated the environmental ratio and concentrations of inorganics reported in a Department of the Interior study for the mouth of Ashley Creek on the Green River, and was composed of nine elements. The mixture was tested at 1X, 2X, 4X, 8X, and 16X where X was the measured environmental concentration (2 μg/L arsenic, 630 μg/L boron, 10 μg/L copper, 5 μg/L molybdenum, 51 μg/L selenate, 8 μg/L selenite, 33 μg/L uranium, 2 μg/L vanadium, and 20 μg/L zinc). Razorback sucker had reduced survival after 60 days exposure to the inorganic mixture at 8X, whereas growth was reduced after 30 and 60 days at 2X and after 90 days at 4X. Bonytail had reduced survival after 30 days exposure at 16X, whereas growth was reduced after 30, 60, and 90 days at 8X. Swimming performance of razorback sucker and bonytail were reduced after 60 and 90 days of exposure at 8X. Whole-body residues of copper, selenium, and zinc increased in a concentration-response manner and seemed to be regulated at 90 days of exposure at 4X and lower treatments for razorback sucker, and at 8X and lower for bonytail. Adverse effects occurred in fish with whole-body residues of copper, selenium, and zinc similar to those causing similar effects in other fish species. Comparison of adverse effect concentrations with measured environmental concentrations showed a high hazard to the two endangered fish. Irrigation activities may be a contributing factor to the decline of these endangered fishes in the middle Green River. ©2000 John Wiley & Sons, Inc. Environ Toxicol 15: 48–64, 2000

Cycleptus meridionalis is a new species recently distinguished from blue sucker C. elongatus. It occurs in large rivers draining to the northern Gulf of Mexico chiefly through Alabama and Mississippi. Collections over a 12-month period from the Pearl and Pascagoula rivers, Mississippi, were taken to document the new species' life history characteristics. Female C. meridionalis had significantly greater wet weight (WW, kg) per given total length (TL, mm) (WW = 4.228−13 TL4.588) than males (WW = 2.000−9 TL3.237). Aged opercular bones indicated that one annulus formed during September–October at the beginning of the reproductive season. Fish ages in the sample ranged from 6 to 31 years for females and from 4 to 33 years for males. Longevity of C. meridionalis is markedly greater than previous scale aging of C. elongatus had suggested. Male C. meridionalis as small as 327 mm TL (age 4) and females as small as 444 mm TL (age 11) had visibly developed gonads; mean gonadosomatic index was elevated in bo...

The decline of native fishes in North America is principally a result of altered habitats, and the impact of mainstream dams has accounted for many of the habitat changes. Diminished turbidity, and introduced nonnative predators were investigated as possible reasons for the decline of endangered razorback suckers Xyrauchen texanus in the Colorado River. In laboratory tests, young razorback suckers selected clear water over two water samples with higher concentrations of suspended sediment. In clear water, however, young razorback suckers were extremely susceptible to predation; native Colorado squawfish Ptychocheilus lucius consumed 90% of test razorback suckers, and nonnative green sunfish Lepomis cyanellus consumed 99.6%. As turbidity increased, razorback sucker predator avoidance improved and differences in predator success disappeared. Winter–spring spawning by razorback suckers in Lake Mohave, along with the extreme susceptibility of larvae to predation in clear water, may account for total ...

Aim I examine the relationship between geographical range size and three variables (body size, an index of habitat breadth, and an index of local abundance) within a phylogenetic framework in North American species of suckers and sunfishes. Location North America Methods Regressions after independent contrasts of geographical range size, body size, habitat breadth, and local abundance. Results Species with large range sizes tend to be larger-bodied, be more locally abundant, and have higher habitat breadths. Character reconstructions support the prediction that variables associated with rarity (small geographical range size, low local abundance, low niche breadth, and large body size) evolve in unison, although large body size was associated with the opposite traits in these taxa. Gaston & Blackburn (1996a) suggested using visual identification of the lower boundary of the geographical range-body size relationship to identify extinction-prone species; this resulted in thirteen species that are potentially extinction-prone. Main conclusions Similar evolutionary mechanisms appear to operate on body size and other variables related to rarity, even in distantly related taxa.

To further evaluate the suitability of small fish species for sentinel monitoring, a comparison was made between the responses of trout-perch (Percopsis omiscomaycus) and the larger white sucker (Catostomus commersoni) under similar conditions of pulp mill effluent exposure and mobility. Fish were collected upstream and downstream of a thermomechanical pulp mill on the Kapuskasing River, Ontario, Canada, where the presence of a hydro dam restricts the movement of fish between reference and exposure areas. Trout-perch collected downstream of the mill were shorter, lighter, and younger than upstream fish, whereas exposed white sucker were longer, heavier, and, for male sucker, older than reference fish. Only male trout-perch showed induced hepatic mixed function oxygenase activity (7-ethoxyresorufin-O-deethylase). Both forskolin-stimulated in vitro production of 17 β-estradiol in trout-perch and plasma concentrations of 17 β-estradiol in sucker were significantly depressed in exposed fish. The inconsistency in responses between species made it difficult to determine how the opposing responses were related and which species was most sensitive to instream conditions. Despite the discrepancies, use of an interpretation framework indicated that both species identified similar potential problems (e.g., size-selective mortality and recruitment problems), suggesting that either species could be used as a sentinel species at this site.

We investigated longitudinal distributions, nearshore movements, and drift of larval native fishes (humpback chub Gila cypha, speckled dace Rhinichthys osculus, bluehead sucker Catostomus discobolus, and flannelmouth sucker Catostomus latipinnis) in the Little Colorado River, a tributary to the regulated Colorado River in Grand Canyon, Arizona, to determine spawning sites, larval dispersal patterns, and amount of drift into the mainstem Colorado River. Larval distributions and drift indicated native fishes spawned throughout the terminal 14.2 km of the Little Colorado River. In addition, distribution, drift, and trap data suggest an active component to dispersal for all four native species. Drift of larval native fish was greater near shore than midchannel, and except for speckled dace larvae, which were prone to drift at night, larval native fish did not exhibit diel periodicity in drift. During a 46-d period in 1993, we estimated that over 370,000 native fish larvae drifted out of the Little Co...

A comparison of the sampling effectiveness of a backpack electroshocker and small-mesh seine was conducted on the upper Cahaba River in the Valley and Ridge physiographic province of north-central Alabama. Each of 15 sites was sampled once during fall 1995 (20 September–23 October), spring 1996 (2 May–20 June), and fall 1996 (20 September–16 October). Sampling was conducted with both gears on the same day, and the same amount of sampling time was allocated to each gear. Samples were segregated into seven groups (Cyprinidae, Catostomidae, Percidae, Centrarchidae [further subdivided into sunfish-crappie and bass categories], and other families as a group), and comparisons of the percent relative abundance (PRA) of groups were made between gears at each sampling station. The PRAs of the groups differed significantly between gears at all 15 stations. Cyprinid PRAs were consistently higher in seine collections, whereas percids, sunfish-crappie, and bass PRAs were higher in electroshocker collections. ...

Fish assemblages and environmental variables were evaluated from 37 least-disturbed, 1st- through 6th-order streams and springs in the upper Snake River basin, western USA. Data were collected as part of the efforts by the U.S. Geological Survey National Water Quality Assessment Program and the Idaho State University Stream Ecology Center to characterize aquatic biota and associated habitats in least-disturbed coldwater streams. Geographically, the basin comprises four ecoregions. Environmental variables constituting various spatial scales, from watershed characteristics to instream habitat measures, were used to examine distribution patterns in fish assemblages. Nineteen fish species in the families Salmonidae, Cottidae, Cyprinidae, and Catostomidae were collected. Multivariate analyses showed high overlap in stream fish assemblages among the ecoregions. Major environmental factors determining species distributions in the basin were stream gradient, watershed size, conductivity, and percentage o...

Acute toxicity tests were conducted for 96 h with larval Colorado squawfish (Ptychocheilus lucius) and razorback sucker (Xyrauchen texanus) in a reconstituted water quality simulating the San Juan River near Shiprock, New Mexico, to determine biological effect concentrations. Tests were conducted with arsenate, copper, selenate, selenite, zinc, and five mixtures of seven to nine inorganics simulating environmental mixtures reported for sites along the San Juan River (Ojo Amarillo Canyon, Gallegos Canyon, Hogback East Drain, Mancos River, and McElmo Creek). Razorback suckers were significantly more sensitive to arsenate, selenate, selenite, Hogback East Drain mixture, and Ojo Amarillo Canyon mixture than were Colorado squawfish. For both species, the Gallegos Canyon mixture had synergistic toxicity, the Mancos River and McElmo Creek mixtures had additive toxicity, and the Ojo Amarillo Canyon mixture had antagonistic toxicity. The Hogback East Drain mixture had additive toxicity to Colorado squawfish, but synergistic toxicity to razorback suckers. The major toxic component in the five mixtures was copper. Comparison of biological effect concentrations (i.e., 96-h LC 50 ) with environmental water concentrations from the San Juan River resulted in a ratio of

An epidemiological study was conducted to evaluate whether the density of pigmented macrophage aggregates (PMAs) and the prevalences of preneoplastic and neoplastic lesions increased in fish captured downstream from a bleached-kraft pulp mill, causing induction of cytochrome P4501A enzymes (CYP1A). White suckers (Catostomus commersoni) sampled 10 and 95 km downstream from a bleached-kraft pulp mill in the St. Maurice River, Quebec, Canada, exhibited higher densities of PMAs relative to age in liver, spleen, and kidney than fish sampled 10 km upstream. White suckers were also sampled at three sites in the Gatineau River, Quebec, Canada, a reference river with a similar upstream/downstream ecological gradient but no pulp mill. In the Gatineau, density of PMAs was lower in the liver of fish sampled at the most downstream site, and there was no difference among sites in spleen and kidney. Higher growth rates have been documented at downstream sites of both rivers and thus cannot explain the increased density of PMAs observed at downstream sites of the St. Maurice River only. Density of PMAs did not differ between sexes or between fish with or without grossly visible parasites or granulomatous histological lesions. Although we cannot exclude the involvement of unknown infectious agents, density of PMAs appears to be a useful marker of bleached-kraft mill effluent (BKME) toxicity. Several known toxic effects of BKME could contribute to this response, including increased rates of lipid peroxidation associated with induced CYP1A and toxic hemolysis. Further field and laboratory studies are needed to evaluate whether the association between BKME exposure, induction of CYP1A, and increased density of PMA is consistent. Preneoplastic lesions were not observed in fish captured downstream of the pulp mill in the St. Maurice River, and only one case of biliary carcinoma was observed, at the most contaminated site.

The razorback sucker (Xyrauchen texanus) is a large, long-lived catostomid fish endemic to the Colorado River drainage of western North America, endangered because of recruitment failure. Efforts to preserve the species have emphasized artificial propagation and reintroduction. Given the importance of maintaining genetic diversity in such a program, we examined mitochondrial DNA diversity in a source population (Lake Mohave, Arizona-Nevada) and three hatchery-produced year classes (1987, 1989, 1990). The source contained considerable variation, indicated by high haplotype diversity (ĥ = 0.97) and a large number of unique haplotypes (17 in 25 individuals). Diversity also was high in the 1987 (ĥ = 0.89, 6 haplotypes in 10 individuals) and 1989 hatchery-produced year classes (ĥ = 0.91, 7 in 11), but significantly lower in the 1990 year class (ĥ = 0.71, 4 in 10). Low diversity in the last class was likely because of differences among females in fecundity, viability of progeny, or both. Because natural populations have collapsed throughout the species’ range, we must identify methods that preserve the most diversity. We examined three potential alternatives: standard hatchery propagation, natural spawning in predator-free environments, and protective custody of larvae collected from the lake with reintroduction after growth to a size likely to survive. The last is the preferred alternative and should be pursued as the most cost-effective option for preserving genetic diversity in the razorback sucker. Xyrauchen texanus es un pez catostomido longevo endemico al drenaje del rio Colorado en el oeste de Norte America, que se encuentra en peligro debido a fracasos en el recrutamiento. Los esfuerzos para preservar la especie han enfatizado la propagacion artificial y la reintroduccion. Dada la importancia que tiene el mantenimiento de la diversidad genetica en tales programas, hemos examinado la diversidad del ADN mitocondrial en una poblacion fuente (lago Mohave, Arizona-Nevada) y en tres clases anuales producidas en estaciones de crianza (1987, 1989, 1990). La fuente tuvo una considerable variacion genetica evidenciada por una alta diversidad haplotipica (h = 0.97) y un gran numero de haplotipos unicos (17 en 25 individuos). La diversidad tambien fue alta en las clases anuales producidas en las estaciones de cria de 1987 (h = 0.89, 6 haplotipos en 10 individuos) y 1989 (h = 0.91, 7 en 11) pero significativamente menor en la clase de 1990 (h = 0.71, 4 en 10). La baja diversidad en la ultima clase era esperada debido a diferencias en la fecundidad entre las hembras, la viabilidad de la progenie, o ambas. Dado que las poblaciones naturales se han colapsado a lo largo y ancho del area de distribucion, debemos identificar metodos que preserven la mayoria de la diversidad. Nosotros examinamos tres alernativas: la propagacion estandard de las estaciones de cria, la reproduccion natural en ambientes libres desde predadores y la custodia protectora de larvas recolectadas del lago reintroduccion con, una vez que las mismas alcancen una talla con alta supervivencia. La ultima opcion es la preferible y deberia ser puesta en efecto como la opcion mas eficiente para preservar la diversidad genetica en Xyrauchen texanus.

The razorback sucker, Xyrauchen texanus, in the middle Green River (U.S.A.) has been described as a static population consisting of old individuals that will eventually disappear through attrition. Capture data between 1980 and 1992 indicated a constant length frequency despite a slow but positive growth rate of individual fish. Abundance and survival estimates indicated that the population of razorback sucker in the middle Green River is precariously low but dynamic. Although high variation existed among survival estimates, no significant decrease in the population between 1982 and 1992 could be detected. The low level of recruitment occurring in the razorback sucker population of the middle Green River was related to high-flow years, indicating that floodplain habitats may be necessary for survival of the species. La probacion de Xyrauchen texanus en el rio “Middle Green” (EEUU) ha sido descrita como estatica consistiendo en individuos viejos que eventaulmente van a desaparecer por atricion. Los datos de captura entre 1980 y 1992 indicaron una frecuencia de tallas constante a pesar de una tasa de crecimiento individual lenta pero positiva para los peces. Las estimaciones de abundancia y supervivencia indicaron que la poblacion de Xyrauchen texanus del rio “Middle Green” es precariamente baja pero dinamica. Si bien existio una alta variacion entre las estimaciones de supervivencia, no se puedo detectar un decremento poblacional significativo entre 1982 y 1992. Los bajos niveles de reclutamiento que ocurren en la poblacion de Xyrauchen texanus fue relacionada con anos de grandes caudales lo que indica que los habitats de las planicies de inundacion son necesarios para la supervivencia de la especie.

We compared marking success for larval and juvenile fishes immersed in alizarin red S (ARS) to that of fish immersed in alizarin complexone (AC). Postlarval and juvenile central stonerollers Campostoma anomalum and southern redbelly dace Phoxinus erythrogaster and larval white suckers Catostomus commersoni were immersed in ARS or AC at concentrations of 50–400 mg/L for 6–24 h. Both chemicals imparted a violet-red mark, visible in the whole otoliths under a bright-field light source. Immersion in ARS at 200–300 mg/L for 12 or 24 h resulted in optimal marking success (100%) and minimal mortalities (0–3%). Marking success and mortalities were similar for ARS and AC in comparable treatments. Alizarin red S marks were retained for at least 160 d.

The objective of this study was to determine if the prevalences of lesions and parasites were different in white suckers (Catostomus commersoni) living upstream and downstream from a bleached-kraft pulp mill in the St. Maurice River, Quebec, Canada. Fish were sampled from two downstream and one upstream sites and were examined internally and externally. Fish living downstream from the mill had more abundant visceral fat, a higher prevalence of deformed fin rays, and a higher prevalence of black livers than fish caught upstream. They were also more frequently infested by intestinal parasites and less frequently infested by larvae of the nematode Eustrongylides in the mesentery. These changes could not be associated specifically to exposure to the pulp mill effluent since they were either explained by among-site differences in fish length or by an upstream-downstream ecological gradient other than the effluent gradient. This ecological gradient was demonstrated by comparison with a reference river, the Gatineau, that had similar physical characteristics but no pulp mill.

The abundance, growth, spatial distribution, and feeding habits of five allopatric brook charr, Salvelinus fontinalis, populations (young-of-the-year, 0+ juveniles; YOY) were compared with five other populations living sympatrically with white sucker, Catostomus commersoni. The study was made in oligotrophic lakes of the Laurentian Shield (Quebec, Canada) during three sampling periods in 1989 (July, August and September). The abundance of YOY charr was significantly higher in allopatric than in sympatric populations (45·3 ± 3·8 vs 3·4 ± 3·8 fish/lake caught in 1773 m2 of gillnets; P

Induction of hepatic ethoxyresorufin-O-deethylase (EROD) activity and accumulation of chlorophenolic compounds typical of bleached-kraft mill effluent (BKME) in fish sampled downstream of a pulp mill on the St. Maurice River, Quebec, Canada, provided evidence of chemical exposure to BKME. In comparison, fish sampled over the same distances and in similar habitats in a noncontaminated reference river, the Gatineau River, demonstrated low EROD activity and contamination levels. Accelerated growth of white suckers occurred between 2 and 10 years of age in both rivers at downstream stations relative to upstream stations, suggesting the existence of gradients of nutrient enrichment independent of BKME contamination. The impact of BKME exposure was expressed as reduced investment in reproduction, as revealed by greater length at maturity, reduced gonad size, and more variable fecundity. These effects were not obvious in simple upstream-downstream comparisons, but became evident when fish from the uncontaminated Gatineau River showed increased gonadal development and reduced age and size at maturity in response to enhanced growth rates.