Catostomus Catostomus Research Articles

Novel mitochondrial DNA primers for identification of population trends in longnose suckers (Catostomus catostomus) and multispecies identification

The understudied longnose sucker has received no attention by the International Union for Conservation of Nature wherein almost 55 % of fish in this family have been classified as threatened, endangered, extinct, or experiencing population declines. Understanding population trends of the ecologically diverse longnose sucker is critical for preservation of this unique species, as it hybridizes readily with congenerics. Here we describe three novel pairs of mitochondrial DNA (mtDNA) primers with which we amplified genes from four species: longnose and white suckers, round whitefish, and slimy sculpin. Nucleotide substitutions ranged from 10 to 111 between individual longnose suckers and among various species. Hybridization may be occurring, as a morphologically identified longnose sucker contained white sucker mtDNA. Species level identification using these primers within a larger scope of landscape studies is possible as these species belong to three orders, showing the utility of these primers on a variety of taxa.

Development of 17 novel microsatellite markers for the longnose sucker (Catostomus catostomus) and successful cross-specific amplification of 14 previously developed markers from congeneric species

The longnose sucker (Catostomus catostomus) is a widely distributed catostomid, found throughout Canada and much of the northern United States. Although it is a species with significant ecological importance, it has been the focus of only a few studies. Here we describe 17 novel microsatellite loci, and the use of 14 previously described markers from congeneric species formerly untested on longnose sucker. Of the 31 described markers, 19 were polymorphic exhibiting between 2 and 20 alleles. Observed and expected heterozygosities ranged from 0.13 to 0.91, and 0.23 to 0.95 respectively. There was no evidence of null alleles or of deviation from Hardy–Weinberg equilibrium for any locus, and no locus pairs exhibited evidence of linkage disequilibrium.

Spatial distribution of pelagic fish larvae in the northern main basin of Lake Huron

Larval fish occurrence in inshore and offshore zones in the northern main basin of Lake Huron was assessed during 2007 as part of a larger ecological examination of Lake Huron foodwebs and habitats. Day and night collections using neuston and conical nets at inshore (1.5–15 m depths) and offshore (37 and 91 m depths) locations at De Tour and Hammond Bay to assess the abundance, phenology, and spatial distribution of pelagic ichthyoplankton during spring and early summer were made. In general, densities of larval fishes were higher at De Tour than Hammond Bay during daytime neuston net collections, with the exception of Longnose Sucker, which were only collected at Hammond Bay. Lake Whitefish, Burbot, and Rainbow Smelt dominated inshore catches in early spring with Cisco, Deepwater Sculpin, Emerald Shiner, Bloater, Slimy Sculpin, Ninespine Stickleback, and Yellow Perch larvae also collected. Nighttime nearshore and offshore sampling revealed that Rainbow Smelt and Burbot larvae were present in relatively high abundances compared to inshore densities. Concentrations of larvae of deepwater demersal fishes such as Lake Whitefish and Deepwater Sculpin suggest that inshore zones in northern Lake Huron are important nursery habitats emphasizing a critical production and recruitment linkage between inshore and deepwater zones.

Absence of mercury effects on fish populations of boreal reservoirs despite 3 to 6 fold increases in mercury concentrations

At the La Grande hydroelectric complex located in northern Quebec, Canada, mercury concentrations were measured in over 25 000 fish as part of an ongoing environmental effects monitoring program. Five fish species were monitored over a 30-year period: the non-piscivorous lake whitefish (Coregonus clupeaformis) and longnose sucker (Catostomus catostomus) and the piscivorous northern pike (Esox lucius), walleye (Sander vitreus) and lake trout (Salvelinus namaycush). Total mercury concentrations were measured by standard cold vapour atomic absorption spectrophotometry. Fish population characteristics, such as fishing yields, growth rates and condition factors were also monitored over a 20-year period. In reservoirs, mercury concentrations in all species increased rapidly after impoundment, peaking after 5 to 9 years in non-piscivorous fishes, and after 9 to 11 years in piscivorous species, at levels 3 to 6 times those measured in surrounding natural lakes, then significantly and gradually declined. Concentrations in most species have returned to levels typical of natural lakes, 10 to 30 years after flooding. Despite such increases, the monitored fish showed no mercury-related ill effects at the population level. For most species, increases were observed in fishing yields (by factors ranging from 2 to over 20), in growth rates and in condition factors (for more than a decade). The fishing yield increase was highest for northern pike of the Robert-Bourassa Reservoir, for which the highest average mercury concentrations were measured (3.28 µg g -1 (ww) for 700-mm fish). The biological boom usually observed after reservoir impoundment, resulting from increased nutrients, may have prevented potential mercury-related ill effects.

Comparisons of Precision and Bias with Two Age Interpretation Techniques for Opercular Bones of Longnose Sucker, a Long‐Lived Northern Fish

AbstractTwo preparations of opercular bones for estimating age of longnose suckers Catastomus catastomus revealed that annuli were obscured by dense bone and undetected when the whole operculum technique was used. By thin‐sectioning the opercula, we removed the dense bone, revealing previously obscured annuli. Using opercula collected from older fish in Labrador, Canada, we found that the dense bone overgrowth led to an overall age bias of 1 year. When samples were broken into groups based on sectioned ages, however, there were minimal differences in age between the two techniques for fish age 6 and younger and a 2‐year age difference for fish estimated to be age 10 and older. To compare precision in locating annuli between the two techniques, we calculated coefficient of variation values among independent determinations. Both techniques demonstrated low variance, however, age determinations had greater variation with thin‐sectioning than with whole opercula interpretations. Therefore, we conclude that care must be taken when making annulus determinations from thin‐sectioning. Due to the presence of dense bone overgrowth, associated with the whole operculum technique, we conclude a combination of both techniques would provide the most thorough procedure for interpreting opercular age for such long‐lived fish (30–50 years).Received November 23, 2011; accepted April 5, 2012

The influence of land use and potamodromous fish on ecosystem function in Lake Superior tributaries

Allochthonous nutrients and carbon are recognized as dominant controls on biogeochemistry of low-order streams. In some systems, potamodromous fish may provide a complementary source of material as they deliver lake-derived materials to spawning streams. This study examines nutrient and carbon inputs from terrestrial ecosystems and migratory fishes to streams in undeveloped watersheds in northern Michigan, USA. We compared watershed and riparian area, slope, and landcover to nutrient concentrations at 26 sites, as well as whole-stream metabolism at 5 sites. Despite low levels of agricultural land use (0–3%), agriculture had the largest influence on stream chemistry as indicated by higher dissolved organic carbon (DOC), ammonium, silica, and chloride concentrations at the watershed level, and increased DOC and chloride at the riparian level. Ecosystem respiration and net primary production increased with watershed and riparian area, and the proportion of managed forest. To quantify inputs from fish, we monitored the spawning migrations of white ( Catostomus commersonii) and longnose ( C. catostomus) suckers at one site, and measured nutrients and stream metabolism above and below an impassable dam. Nutrient concentrations were uniformly low and did not increase during the fish migration; however, temporal shifts in stream metabolism during sucker migration suggest that fish influenced respiration, presumably by providing high-quality carbon and bioavailable nutrients. We conclude that both watershed land use and fish migrations provide important sources of allochthonous material to these oligotrophic streams. Recognizing the bi-directional nature of allochthonous inputs is important for understanding controls on ecosystem functioning in low-order streams.

Longitudinal variation and habitat associations of small fishes in the Bighorn River, Wyoming: influences of river regulation and introduced fishes

We assessed variation in longitudinal distributions of native and introduced fishes and their occurrences in different habitat types downstream from Boysen Dam in the Bighorn River, Wyoming. The closure of Boysen Dam in 1952 and construction of three downstream water diversion dams have led to channel changes in the Bighorn River causing reductions in the numbers and areas of side channels, backwaters, and riffles. Eleven native and five introduced fish species were collected by seining during 2005. Fish samples were dominated by sand shiner (Notropis stramineus), flathead chub (Platygobio gracilis), and longnose sucker (Catostomus catostomus). Introduced fish species included common carp (Cyprinus carpio), emerald shiner (Notropis atherinoides), plains killifish (Fundulus flavis), yellow perch (Perca flavescens), and sand shiner. Differences in relative abundances of fishes among habitat types were observed. Fathead minnow (Pimephales promelas), longnose sucker, white sucker (Catostomus commersoni), plains killifish, and sauger (Sander canadensis) were found almost exclusively in backwaters, and channel catfish (Ictalurus punctatus) was collected almost exclusively in side channels. Changes from the pre-European fish community are occurring in association with invasions of introduced fish species and losses of side channels, backwaters, and riffles.

Seasonal Movements of Native and Introduced Catostomids in the Big Sandy River, Wyoming

During 2006–2007, we studied movements of native bluehead suckers (Catostomus discobolus) and flannelmouth suckers (C. latipinnis), and non-native white suckers (C. commersonii) and longnose suckers (C. catostomus) in the Big Sandy River, Wyoming. Radiotransmitters were surgically implanted into 20–22 fish of each species in September and October 2006. Movements of all four species in autumn and winter were short with most fish remaining ≤2 km from locations where they were captured initially. Bluehead suckers and flannelmouth suckers began movements downstream in mid-to-late April and returned upstream to locations ≤2 km from their original locations by early summer. White suckers did not make substantial movements during spring, whereas longnose suckers made movements upstream during mid-June and returned downstream by early July. During their estimated spawning periods, longnose suckers used upstream portions, bluehead suckers and white suckers used middle portions, and flannelmouth suckers used downstream portions of the study area.

Ecological consequences of invasive lake trout on river otters in Yellowstone National Park

The introduction of lake trout ( Salvelinus namaycush) to Yellowstone Lake in Yellowstone National Park has contributed to a significant decline in the endangered Yellowstone cutthroat trout ( Oncorhynchus clarki bouvieri), leading to concern over the persistence of this subspecies but also to piscivorous predators in this community. We assessed the impact of lake trout on a key piscivore, the river otter ( Lontra canadensis) in two lakes in Yellowstone National Park. Yellowstone Lake continues to support a native cutthroat trout population, although the recent introduction of lake trout has dramatically impacted the cutthroat trout population. Nearby Lewis Lake has an entirely introduced fish fauna of lake trout, brown trout ( Salmo trutta), and Utah chub ( Gilia atraria) but lacks cutthroat trout. Analysis of otter scat from Yellowstone Lake implicated trout (lake or cutthroat trout) as a major prey item (57% of scat), whereas stable isotopes identified longnose suckers ( Catostomus catostomus) as the primary prey there (58% of diet). By contrast, scat from Lewis Lake implicated minnows, presumably Utah chub, as the primary prey for otters occupying that lake (86%), while stable isotopes implicated brown trout (64%) over both lake trout and Utah chub (36% combined). Our data establish the importance of alternative prey to otters and suggest that lake trout-induced reductions in cutthroat trout may not be catastrophic for otter populations here. These data do not necessarily exonerate lake trout, as their impact on other species, most notably grizzly bears ( Ursus arctos) and piscivorous birds, has been documented to be substantial, and further data on the nutritional value of alternate prey are required to confirm or refute a working hypothesis that otter populations will continue to thrive in the face of the lake trout invasion.

Use of Stable Carbon and Nitrogen Isotopes to Trace Natural and Anthropogenic Inputs into Riverine Systems in the Athabasca Oil Sands Region

Abstract Stable isotopes of carbon and nitrogen in fish were examined as a potential tracer of exposure to oil sands constituents in naturally eroded environments and in areas of anthropogenic activity (municipal and industrial effluent discharges; oil sands surface mining) within the Athabasca River drainage basin of northern Alberta, Canada. Longnose sucker (Catostomus catostomus), trout-perch (Percopsis omiscomaycus), and slimy sculpin (Cottus cognatus) showed changes in δ13C values with the river gradient. Site-specific differences in the δ13C values of fish were more pronounced for the small-bodied fish species in the lower reaches of a tributary (slimy sculpin) and immediately downstream of tributary inputs along the Athabasca River (trout-perch), where potential exposure to the oil sands constituents is elevated. There were also species and site-specific trends for δ15N values. Site-specific trends attributed to municipal or industrial effluent discharge or tributary inputs may prove to be a useful tool for defining residency on the oil sands deposit. This study has provided baseline data of isotope values for fish species which are currently used (longnose sucker) or may be used in future environmental effects monitoring programs. Defining residency and exposure to the oil sands deposit is critical to establishing exposure-response relationships, particularly since there are new expansions to oil sands mining operations.

Nearshore Habitat and Fish Community Associations of Coaster Brook Trout in Isle Royale, Lake Superior

AbstractWe characterized the nearshore habitat and fish community composition of approximately 300 km of shoreline within and adjacent to the major embayments of Isle Royale, Lake Superior. Sampling yielded 17 species, of which 12 were widespread and represented a common element of the Lake Superior fish community, including cisco Coregonus artedi, lake whitefish C. clupeaformis, round whitefish Prosopium cylindraceum, lake trout Salvelinus namaycush, rainbow smelt Osmerus mordax, lake chub Couesius plumbeus, longnose sucker Catostomus catostomus, white sucker C. commersonii, trout‐perch Percopsis omiscomaycus, ninespine stickleback Pungitius pungitius, burbot Lota lota, and slimy sculpin Cottus cognatus. The presence of brook trout S. fontinalis in an embayment was associated with the common species of the Isle Royale nearshore fish community, particularly cisco, longnose sucker, and round whitefish. However, brook trout were present in only five embayments and were common only in Tobin Harbor. Most Isle Royale embayments had broadly overlapping ranges of nearshore habitats. Within embayments, fish were distributed along a habitat gradient from less‐protected rocky habitat near the mouth to highly protected habitat with mixed and finer substrates at the head. Embayments with brook trout had greater mean protection from the open lake, greater variation in depth, greater mean cover, and higher mean frequencies of large substrates (cobble, boulder, and bedrock). Within those embayments, brook trout were associated with habitat patches with higher mean frequencies of small substrates (particularly sand and coarse gravel). Within Tobin Harbor, brook trout were associated with midembayment habitat and species assemblages, especially those locations with a mixture of sand, gravel, and cobble substrates, an absence of bedrock, and the presence of round whitefish, white sucker, and trout‐perch. Comparison of embayments with the model, Tobin Harbor, showed that six embayments without brook trout had very similar arrays of habitat. However, four embayments with brook trout had relatively different arrays of habitat from Tobin Harbor. These results suggest that there is potential for further recovery of brook trout populations across Isle Royale nearshore habitats.

Arsenic concentration and speciation in five freshwater fish species from Back Bay near Yellowknife, NT, CANADA

The concentration of total arsenic and five different arsenic species [As(III), As(V), monomethylarsonic acid (MMA), dimethylarsenic acid (DMA), and arsenobetaine (AsB)], were measured in the muscle, liver and gastrointestinal tract (GIT) of five different fish species [lake whitefish (Coregonus clupeaformis), walleye (Stizostedion vitreum), northern pike (Esox lucius), white sucker (Catostomus commersoni) and longnose sucker (Catostomus catostomus)] from Back Bay, Great Slave Lake, near the city of Yellowknife, NT, Canada. The total concentration (dry weight) of arsenic in muscle ranged from 0.57 to 1.15 mg/kg, in the liver from 0.42 to 2.52 mg/kg and in the GIT from 1.48 to 8.92 mg/kg. Among fish species, C. commersoni had significantly higher total arsenic concentrations in the GIT than S. vitreum, E. lucius and C. clupeaformis, and higher total arsenic concentrations in the liver than C. clupeaformis. The mean concentration of As(III) and As(V) in the muscle of all fish ranged from < or =0.01 to 0.05 mg/kg and < or =0.01 to 0.02 mg/kg, respectively, and together comprised < or =7.5% of the total arsenic measured in muscle. The concentrations of MMA were below detection in the muscle of all five fish species. However, AsB and DMA were measured in all fish species and nearly all fish tissues. The concentrations of AsB ranged from 0.01 to 0.13 mg/kg and the concentrations of DMA ranged from <0.02 to 0.45 mg/kg. The majority (>50%) of organic arsenic in almost all of the tissues from fish caught in Back Bay was not directly identified. Evidence from the literature suggests that most of these other organic arsenic species were likely trimethylated arsenic compounds, however, further analytical work would need to be performed to verify this hypothesis.

Hearing in eight species of northern Canadian freshwater fishes

The hearing thresholds of eight fish species from northern Canada were measured using auditory evoked potential techniques. The species with the best hearing was the lake chub Couesius plumbeus, followed by the longnose sucker Catastomus catastomus, both which had relatively sensitive hearing over the frequency range tested from 100 to 1600 Hz. The remaining species (troutperch Percopsis omiscomaycus, nine‐spined stickleback Pungitius pungitius, pike Esox lucius, spoonhead sculpin Cottus ricei, burbot Lota lota and broad whitefish Coregonus nasus) all showed most sensitivity to low frequencies (&lt;400 Hz) and had relatively insensitive high frequency hearing. The two species with the best hearing are otophysan fishes with connections between the swimbladder and inner ear. The spoonhead sculpin lacks a swimbladder, while the other non‐otophysan species have swimbladders, but no specialized connection to the inner ear. These results can be used to predict the potential impact of anthropogenic noise, such as seismic air gun blasts, on hearing in these species. The species with the most sensitive hearing (lake chub and longnose sucker) are most likely to be affected by activities such as seismic air gun surveys.

Environmental Contaminants in Fish and Their Associated Risk to Piscivorous Wildlife in the Yukon River Basin, Alaska

Organochlorine chemical residues and elemental contaminants were measured in northern pike (Esox lucius), longnose sucker (Catostomus catostomus), and burbot (Lota lota) from 10 sites in the Yukon River Basin (YRB) during 2002. Contaminant concentrations were compared to historical YRB data and to toxicity thresholds for fish and piscivorous wildlife from the scientific literature. A risk analysis was conducted to screen for potential hazards to piscivorous wildlife for contaminants that exceeded literature-based toxicity thresholds. Concentrations of total DDT (sum of p,p'-homologs; 1.09-13.6 ng/g), total chlordane (0.67-7.5 ng/g), dieldrin (<0.16-0.6 ng/g), toxaphene (<11-34 ng/g), total PCBs (<20-87 ng/g), TCDD-EQ (<or=1.7 pg/g), arsenic (0.03-1.95 microg/g), cadmium (<0.02-0.12 microg/g), copper (0.41-1.49 microg/g), and lead (<0.21-0.27 microg/g) did not exceed toxicity thresholds for growth and reproduction in YRB fish. Concentrations of mercury (0.08-0.65 microg/g), selenium (0.23-0.85 microg/g), and zinc (11-56 microg/g) exceeded toxicity thresholds in one or more samples and were included in the risk analysis for piscivorous wildlife. No effect hazard concentrations (NEHCs) and low effect hazard concentrations (LEHCs), derived from literature-based toxicity reference values and avian and mammalian life history parameters, were calculated for mercury, selenium, and zinc. Mercury concentrations in YRB fish exceeded the NEHCs for all bird and small mammal models, which indicated that mercury concentrations in fish may represent a risk to piscivorous wildlife throughout the YRB. Low risk to piscivorous wildlife was associated with selenium and zinc concentrations in YRB fish. Selenium and zinc concentrations exceeded the NEHCs and LEHCs for only the small bird model. These results indicate that mercury should continue to be monitored and assessed in Alaskan fish and wildlife.

RIVER OTTERS IN YELLOWSTONE LAKE DEPEND ON A DECLINING CUTTHROAT TROUT POPULATION

Introduced lake trout (Salvelinus namaycush) threaten the native cutthroat trout (Oncorhynchus clarki bouvieri) population in Yellowstone Lake, Yellowstone National Park, Wyoming. A reduction in availability of cutthroat trout may affect fish predators negatively, especially during spawning season. In this study we examined the importance of spawning cutthroat trout to a fish specialist—the North American river otter (Lontra canadensis). We measured scent-marking rates at 87 otter latrine sites on Yellowstone Lake and its tributary streams throughout the cutthroat trout spawning period and identified prey in scats collected at these sites. Based on fecal deposition rates, otters were more active on spawning streams and less active on Yellowstone Lake during the height of cutthroat trout spawning, with a return to elevated activity on the lake after spawning had ended. Cutthroat trout appeared to be the most common prey item in otter scats throughout the study, based on 515 samples identified to the family level and 110 samples analyzed to the species level. Overall, trout occurred in 72% and longnose suckers (Catostomus catostomus) in 43% of otter feces. Suckers were more prevalent than trout in otter scats only on tributary streams, toward the end of cutthroat trout spawning. Introduced lake trout, which inhabit deep water and are largely inaccessible to otters, occurred in less than 5% of otter scats. River otters in the Yellowstone Lake ecosystem appear to be relatively restricted in their diet and are heavily dependent on cutthroat trout. Our findings suggest that continued declines in the cutthroat trout population could negatively impact otters, potentially disrupting their role in linking aquatic and terrestrial ecosystems in and around Yellowstone Lake.

How Many River Otters Inhabit Yellowstone Lake? An Assessment with Fecal and Hair DNA Analyses

River otters (Lontra canadensis) in Yellowstone Lake are different from most other otter populations in that they are heavily dependent on one prey species - Yellowstone cutthroat trout (Oncorhynchus clarki bouvieri; Crait and Ben-David 2006, Crait et al. 2006). Our 2002-2003 studies in Yellowstone Lake showed that cutthroat trout were the most common prey item in otter scats throughout the summer. Overall, trout occurred in 72% and longnose suckers (Catostomus catostomus) in 43% of otter feces, based on 515 samples identified to the family-level and 110 samples analyzed to the species-level. Suckers were more prevalent than trout in otter scats only on tributary streams, towards the end of the cutthroat trout spawning season. Introduced lake trout (Salvelinus namaycush), which inhabit deep water and are largely inaccessible to otters, occurred in less than 5% of otter scats. In addition, based on fecal deposition rates, we established that otters were more active on spawning streams and less active along the Yellowstone Lake shoreline during the height of the cutthroat trout spawning season, with a return to elevated activity on the lake after spawning had ended (Crait and Ben-David 2006). Therefore, because of the lack of a suitable alternative prey, it is likely that a decline in cutthroat trout (Koel et al. 2005) will translate into a decline in the abundance of otters in this system. Indeed, our 2002-2003 survey indicates the number of river otter latrine sites in the Yellowstone Lake ecosystem is lower than expected based on similar surveys in the Rocky Mountain region (Crait and Ben-David unpublished data).

Application of Multi-stable Isotope (13C, 15N, 34S, 37Cl) Assays to Assess Spatial Separation of Fish (Longnose Sucker Catostomus catostomus) in an Area Receiving Complex Effluents

Abstract Incorporation of stable isotope analysis (SIA) into routine environmental effects monitoring programs of receiving waters may enable determination of the spatial extent of biotic exposure and discrimination among sources of complex effluents. To evaluate this hypothesis, longnose sucker (Catostomus catostomus) were collected from four sites along the Athabasca River, Alberta (upstream reference site, two sites downstream of effluents from two pulp and paper mills, and a site downstream of effluent from a municipal sewage treatment plant). Stable isotopes of carbon, nitrogen, sulfur and chlorine were analyzed in bone, gonad, liver and white muscle tissues of the fish. In general, most sites and tissues differed according to δ13C, δ15N and δ34S values. Also, an interaction between site and tissue was observed for δ15N values. A better insight into the usefulness of stable isotopes was obtained through the use of multivariate discriminant function analysis. δ15N and δ34S signatures of gonad and liver tissues of males were most effective at classifying fish according to site (~70% for both tissues). For all tissues except bone, fish from the upstream reference site were most separable from all others, especially females. δ37Cl values for female gonads and male livers were related to sites downstream of the pulp and paper mills. Future research should routinely include SIA of fish tissues, but also of effluents, receiving waters and food web components to better resolve links between specific effluents and fish exposure.

Oxidative Stress and Sex Steroid Levels in Fish Following Short-Term Exposure to Pulp-Mill Effluents

This study investigates the relationship between oxidative stress and reproductive dysfunction in wild white sucker (Catostomus commersoni) with short-term exposures to pulp-mill effluent. Hepatic oxidative damage, as quantified using 2-thiobarbituric acid-reactive substances (TBARS), was often increased with effluent exposure within 4–8 d, but responses varied by species, sex, and effluent. Fatty acyl-coenzyme A (CoA) oxidase (FAO) and ethoxyresorufin O-deethylase (EROD) activities were also significantly induced between 4 and 8 d of exposure. There were marked species differences in oxidative stress, as TBARS, FAO, and EROD responses in white sucker differed dramatically from those of longnose sucker (Catostomus catostomus) exposed under identical conditions. Exposure for 8 d to pulp-mill effluent delayed ovulation in white sucker, and these delays were independent of changes in circulating testosterone and 17α,20β-dihydroxy-4-pregnen-3-one titers. Evaluations of the effects of pulp mill effluent on in vivo plasma steroid levels and in vitro steroidogenic capacities were compromised due to caging stress. In vivo preexposure to pulp-mill effluent did not reduce in vitro ovarian follicle steroidogenic capacities when exposed to additional reactive oxygen species (ROS) generators. Endocrine and oxidative stress parameters may be interrelated, as the in vivo administration of ferric nitrilotriacetate (Fe3+NTA) significantly reduced circulating sex steroids. Administration of a superactive GnRH analog containing a dopamine inhibitor significantly increased TBARS within 24 h, indicating endocrine status is capable of modifying oxidative stress responses. This study provides new knowledge regarding the onset of oxidative stress and changes in reproductive endpoints in fish following pulp-mill effluent exposure. The authors gratefully acknowledge the technical assistance of P. Boutot, C. Chisholm, S. Currie, K. Daynes, M. Edwards, M. Gray, E. LeBlanc, L. Luxon, C. Portt, D. Stevens, and G. Tetreault. We thank D. Roy of the Atlantic Salmon Federation for the loan of fish tanks. We thank the anonymous reviewers for their constructive comments, which greatly strengthened the article. This work was supported by Canadian Network of Toxicology Centers (CNTC), Department of Fisheries and Oceans (DFO), Environment Canada, and Natural Sciences and Engineering Research Council (NSERC) of Canada grants to G. Van Der Kraak. K. D. Oakes received financial support from CNTC, DFO, NSERC, and the Ontario Graduate Scholarship program.

Oxidative stress responses in longnose sucker ( Catostomus catostomus) exposed to pulp and paper mill and municipal sewage effluents

While recent evidence indicates that the generation of reactive oxygen species (ROS) and associated oxidative damage are frequently observed in fish populations with exposure to pulp and paper mill effluents, the potential for ROS generation from municipal sewage effluents has not been addressed. This study investigates the utility of measures of oxidative stress in delineating the effects of both pulp and paper mill and municipal sewage discharges. Longnose sucker ( Catostomus catostomus) were collected below three pulp and paper mill and two municipal sewage effluent discharges over a 3-year period within the Wapiti and Athabasca River systems in northern Alberta. Biochemical responses in longnose sucker varied between the two rivers systems, with more pronounced changes occurring within the Wapiti River. Of the suite of biochemical parameters examined, fatty acyl-CoA oxidase (FAO) activity was the most sensitive indicator of pulp and paper mill exposure, but was only infrequently induced with exposure to municipal sewage effluent. Hepatic and gonadal 2-thiobarbituric acid reactive substances, lipid hydroperoxides, and hepatic free iron were less consistently elevated with exposure to pulp and paper mill effluent than FAO activity, and were also only infrequently altered with sewage effluent exposure. Hepatic ascorbic acid, liver somatic index, and condition factor were consistently altered with exposure to both sewage and pulp and paper mill effluents. While specific biochemical and organismal responses varied with effluents and time, the collective suite of oxidative stress endpoints proved to be useful tools in identifying relative influences of municipal sewage and pulp and paper mill effluent on fish populations in adjacent receiving waters.

Relationships between Bald Eagle Productivity and Dynamics of Fish Populations and Fisheries in the Wisconsin Waters of Lake Superior, 1983–1999

Bald eagle ( Haliaeetus leucocephalus) abundance declined in the 1950s and 1960s along the Wisconsin waters of Lake Superior, and were nearly absent along Wisconsin's Lake Superior shoreline. The population began to increase again between 1980 and 1983, and since then bald eagles nesting on islands along Wisconsin's Lake Superior shoreline (i.e., Apostle Islands) reproduced at a lower rate than have those nesting along the mainland shoreline of the lake and inland. Recent research indicated that bioaccumulation of toxic chemicals in the aquatic food chain no longer limits bald eagle reproduction there, and that productivity at island nests was lower than at mainland nests and inland nests as the result of low food availability. Management agencies have sought models that accurately predict productivity and explain ecological relationships, but no satisfactory models had previously been developed. Modeling was conducted here to determine which factors best explained productivity variability. The Ricker stock-recruitment model derived from only the bivariate breeding pair and productivity data explained only 1% of the variability in productivity data. The functional relationship that explained the greatest amount of productivity variation (83%) included the number of breeding pairs, burbot ( Lota lota) biomass, longnose sucker ( Catostomus catostomus) biomass, and commercial harvest of nontarget fishes. Model results were interpreted to mean that productivity was positively affected by populations of burbot and longnose sucker, which are important prey items, and by commercial fishermen feeding nontarget fish to bald eagles. Harvest of nontarget fishes by tribal fishermen and burbot and longnose sucker populations have not tended to change during the entire study period, although the burbot population has declined since 1991. Therefore, bald eagle productivity is not predicted to increase unless burbot, longnose sucker, or other preferred prey of bald eagles increases in the Apostle Islands.