Young fish distribution in backwaters and main-channel borders of the Kanawha River, West Virginia

Fish in the Kanawha River were collected with a 0^.5-m plankton net in main-channel borders and in open areas of backwaters and with a 1-m² enclosed dropbox in shallow backwater habitats. Larval emerald shiners, Notropis atherinoides , were twice as dense, and gizzard shad, Dorosoma cepedianum , 2^.5 times as dense in main-channel borders as in backwaters; larval Lepomis spp. were 20 times as dense in backwaters as in main-channel borders. Smaller Lepomis larvae used open-water backwater areas primarily; larger larvae migrated to vegetated backwater habitats later in the summer. Backwaters appear crucial for the maintenance of nest-building fish species in temperate rivers, just as floodplains are necessary for the maintenance of high species diversity in tropical rivers.     

Backwater areas as nursery habitats for fishes in pool 13 of the Upper Mississippi River

Samples of larval and juvenile fishes were collected at two depths weekly during spring and summer 1983 near the mouths of backwater areas in Pool 13 of the Upper Mississippi River. The study was conducted to determine the relative value of these habitats as nursery areas for fishes present and to note any interactions that might occur between the backwaters which are being rapidly lost to siltation, and the main channel. The larvae and juveniles collected represented 13 families divided into 27 lower taxa. Cyprinidae, Clupeidae, and Sciaenidae made up 90% of the total catch. Both larvae and juveniles were more abundant near the surface than near the bottom. Densities differed greatly among the three backwater areas studied. Larval fishes were grouped on the basis of their relative abundance in the backwaters or main channel. Overall, more larvae were captured in the backwaters than in main-channel habitats, indicating that backwaters were more productive. In the main channel, densities were greater downstream from the mouths of the backwaters than upstream-possibly indicating that (1) larval fish drifted out of the backwater areas, (2) water rich in nutrients or zooplankton that flowed into the main channel created productive downstream sites that were used as nursery areas, or (3) adult fishes selected downstream sites as spawning areas. Juvenile forms were more abundant in the backwater areas then in the main-channel habitats, some bottom-dwelling fishes excepted. The backwater areas were judged to be important nursery areas for larval and juvenile fishes, and seemed to benefit downstream main-channel sites. Any loss of these habitats would be detrimental to the Mississippi River as a whole.     

Relative abundance of macroinvertebrates found in habitats associated with backwater area confluences in Pool 13 of the Upper Mississippi River

Ephemeroptera showed the greatest diversity and Diptera (due mainly to Chaoboridae) the greatest absolute abundance among the macroinvertebrate taxa collected in and near three backwater areas of the Upper Mississippi River from 24 April to 24 August 1983. Of the 32 taxa identified, all were insect larvae, pupae, or adults except for one amphipod and one copepod. Three peaks in total abundance were observed — a major one in late July and August and smaller ones in May and June. These peaks corresponded to periods of high temperatures and low flows. When the macroinvertebrates were divided into groups, depending on whether they were found predominantly in the backwater areas, in the main channel, or in a combination of the two, total densities were greater in the backwater areas than in either of the main-channel habitats. In the two main-channel habitats, densities were slightly greater downstream than upstream from the confluences of the backwaters with the main channel, possibly indicating that macroinvertebrates were drifting out of the backwater areas or that nutrients and zooplankton were drifting out of the backwater areas, increasing productivity in downstream areas.     

Ligulosis associated with mortality in largescale suckers

Investigations of a fish kill at an irrigation reservoir in the Deschutes River basin, Oregon, documented at least 153 dead largescale suckers Catostomus macrocheilus , all heavily infected with large Ligula intestinalis (Cestoda). Moribund fish nearshore were similarly infected, with no evidence of secondary disease or infection. Morbidity and mortality in all cases was probably due to severe mechanical damage to internal host organs resulting from infection with multiple, large L. intestinalis . The pathology of L. intestinalis documented in largescale sucker in this study contrasts sharply with previous accounts and may represent a new and emerging disease for largescale suckers.     

Basin-scale Patterns in the Drift of Embryonic and Larval Fishes and Lamprey Ammocoetes in two Coastal Rivers

We studied the distribution and abundance of drifting embryonic and larval fishes and lampreys in the Smith and Van Duzen rivers of northern California, U.S.A. We collected seven fish species in four families and at least one lamprey species in the drift. All taxa drifted almost exclusively at night. Sculpins, Cottus aleuticus and C. asper, outnumbered all other taxa, comprising 63% of the catch in the Van Duzen River and 90% of the catch in the Smith River. We estimated that sculpin drift reached 3×10⁷ individualsh^–1 during the relatively high flow period from late winter through early summer. Most sculpin in these two rivers appeared to drift to the estuaries; we estimated 2.5×10⁹ sculpin embryos and larvae reached the Smith River estuary in 1995. In contrast to the sculpins, the patterns in the drift of other taxa suggest limited transport to the estuaries. Suckers, Catostomus occidentalis in the Van Duzen River, C. rimiculus in the Smith River, threespine stickleback, Gasterosteus aculeatus, and lamprey, Lampetra tridentata and possibly L. richardsoni, drifted at much lower rates and later in the year than sculpins. In the Van Duzen River, drift appeared to serve as a dispersal mechanism for only one of three introduced cyprinids. California roach, Lavinia symmetricus, drifted at low rates throughout the summer while we captured only seven Sacramento pikeminnow, Ptychocheilus grandis, and no speckled dace, Rhynichthys osculus. The information gathered on the drift of early life history phases is germane to both the conservation of native fishes and management of non-indigenous species in coastal rivers.     

Intersex and other reproductive disruption of fish in wastewater effluent dominated Colorado streams

Intersex white suckers (Catostomus commersoni) were collected in Boulder Creek and the South Platte River downstream of wastewater treatment plant (WWTP) effluent but not at reference sites. Eighty-three percent of the 60 white suckers collected downstream of the Boulder WWTP in spring and fall were female compared to 45% upstream (n=33). Only female (n=16) and intersex white suckers (n=4) were collected in the South Platte River downstream of the Denver WWTP in the spring. Gonad deformities and delayed follicular maturation were noted in some white suckers in Boulder Creek and the South Platte River downstream of the WWTP effluents. Asynchronous ovarian development was found in some female white suckers downstream of the WWTP effluents, but not upstream. The types and extent of sexual disruption differed in each river studied.     

Feeding ecology of larval and juvenile American shad (Alosa sapidissima) in a small pond

Release ponds are used as part of a multifacet effort to restore American shad ( Alosa sapidissima ) in the upper Susquehanna River basin. Little information exists, however, on the feeding ecology of young shad in small ponds. Consequently, we examined feeding ecology and prey selection of 299 larval and 299 juvenile American shad in a small pond during spring and summer. Larval shad mainly consumed copepods (37.7%) and cladocerans (37.4%) whereas juvenile shad ate chironomids (43.1%) and ostracods (28.4%). Larval and juvenile shad exhibited diel variation in diet composition and feeding periodicity. Food consumption by shad was minimal at night; feeding activity was highest during the day, peaking at 2000 h for both larvae and juveniles. Electivity values of shad larvae for prey taxa were highest for cladocerans (+0.27) and lowest for ostracods (−0.07). Electivity values of juvenile shad were highest for chironomids (+ 0.21) and ostracods (+ 0.09), and lowest for copepods (− 0.08) and baetids (− 0.14). Our data indicate differences in diet composition, prey preference and, to a lesser extent, feeding patterns between larval and juvenile American shad in small pond environments.     

Feeding and fate of wild larval razorback sucker

The razorback sucker (Xyrauchen texanus) is disappearing throughout its native range in the Colorado River basin of western North America. The largest remaining wild population in Lake Mohave, Arizona-Nevada, has shown no recruitment since the 1950s. Although annual spawning is successful and larvae are seasonally abundant, no juveniles have been collected in recent decades. To evaluate the potential role of food availability in determining fate of larvae, fish and zooplankton samples were taken in 1985 from the reservoir and an adjacent, isolated backwater in which larvae were naturally produced. Food availability and primary dietary constituents were similar in both habitats. Reservoir larvae selectedBosmina spp. (Cladocera) and apparently avoided Copepoda, while larvae from the backwater selectedBosmina, but avoided Rotifera. Larvae from both places showed evidence of selection for certain sizes of zooplankters, but preferred sizes differed between habitats. These differences were neither attributable to larval size nor zooplankton community structure. Nutritional factors such as type, number, or size of available foods do not explain disappearance of larval razorback suckers from Lake Mohave, since larvae survive to far greater ages and size in the backwater. Predation by introduced fishes appears a significant cause of larval mortality.     

Fish Communities of the Lower Fraser River (Canada) and a 21-year Contrast

Fish communities were sampled at 14 sites along the lower 120km of the Fraser River, British Columbia by beach seine four times in 1972–1973 and three times in 1993–1994. Of the 37 species collected, peamouth chub, largescale sucker, starry flounder, and northern squawfish were predominant in either density or biomass. Densities and biomass of most species and all fish combined were higher in 1993–1994. Strong rank correlations of species abundance or biomass indicated that the overall fish community structure was very similar in both periods. At smaller spatial scales (reaches of 2–3 sites) and shorter time scales (by season), less than half the comparisons showed any significant correlation indicating changes in community composition. Largescale sucker, one of the largest contributors to biomass in both periods, showed decreased abundance, i.e., lower density, lower biomass, and large differences in the size-frequency distribution, specifically very low representation of small size classes. Other species, especially small-bodied forms, generally increased in numbers. Despite large changes in the lower Fraser River ecosystem in the past 21 years, the overall fish community has shown remarkably little change over that interval.     

Effects of ambient Lake Mohave temperatures on development,oxygen consumption,and hatching success of the razorback sucker

Synopsis Spawning of razorback suckers,Xyrauchen texanus, in Lake Mohave occurred from 10–22°C and larvae were collected at water temperatures from 10–15°C in 1982 and 1983. In the laboratory, hatching success was similar from 12–20°C, but reduced hatching success was found at 10°C while none hatched a 8°C. Development rate and oxygen consumption were positively related to incubation temperature. Direct effects of ambient Lake Mohave water temperatures on hatching success of razorback sucker embryos are considered minimal. Historical spawning temperatures for the species are hypothesized based upon successful incubation temperatures and comparison to the white sucker,Catostomus commersoni.     

Winter movements and habitat use of riverine brown trout, white sucker and common carp in relation to flooding and ice break-up

Movement of radio-tagged riverine brown trout Salmo trutta , white sucker Catostomus commersoni and common carp Cyprinus carpio in the Grand River, Ontario, was minimal during the winter except during periods of high water discharge or the break-up of river ice. Ice break-up and flooding occur when southern air masses penetrate northwards in winter and as air temperatures increase in spring. Both white suckers and common carp moved the longest distances, generally in a downstream direction, during flooding and ice break-up. Brown trout moved less during these times. All three species had positive relationships between distance moved and water discharge. During periods of high water discharge and ice break-up, white suckers and common carp used backwater habitats more and main channel habitats less than during periods of low water discharge. During high flows, brown trout tended to use runs more and pools less. The break-up of river ice and accompanying flooding resulted in several fish being stranded on the floodplain. Backwater habitats appear to be important areas of refuge for riverine fishes during periods of flooding and ice break-up.     

Amplification and transport of an endemic fish disease by an introduced species

The introduction of American shad from the Atlantic to the Pacific coast of North America in the late 1800’s and the subsequent population expansion in the 1980’s resulted in the amplification of Ichthyophonus sp., a Mesomycetozoean parasite of wild marine fishes. Sequence analysis of the ribosomal DNA gene complex (small subunit and internal transcribed spacer regions) and Ichthyophonus epidemiological characteristics indicate a low probability that Ichthyophonus was co-introduced with American shad from the Atlantic; rather, Ichthyophonus was likely endemic to marine areas of the Pacific region and amplified by the expanding population of a highly susceptible host species. The migratory life history of shad resulted in the transport of amplified Ichthyophonus from its endemic region in the NE Pacific to the Columbia River watershed. An Ichthyophonus epizootic occurred among American shad in the Columbia River during 2007, when infection prevalence was 72%, and 57% of the infections were scored as moderate or heavy intensities. The epizootic occurred near the record peak of shad biomass in the Columbia River, and corresponded to an influx of 1,595 mt of infected shad tissues into the Columbia River. A high potential for parasite spillback and the establishment of a freshwater Ichthyophonus life cycle in the Columbia River results from currently elevated infection pressures, broad host range, plasticity in Ichthyophonus life history stages, and precedents for establishment of the parasite in other freshwater systems. The results raise questions regarding the risk for sympatric salmonids and the role of Ichthyophonus as a population-limiting factor affecting American shad in the Columbia River.     

Distribution and abundance of young fish in the St. Clair River and associated waters,Ontario

Fish larvae were sampled in 1986 in the St. Clair River, and adjacent waters. Species richness (9 taxa as larvae; 4 others as juveniles) and abundance was lowest in the river, where many larvae (e.g., burbot, rainbow smelt, and yellow perch) were in transit from Lake Huron. The most abundant, and localized, species was gizzard shad, which reached a peak mean density of 4600 larvae 100 m^-3 in an agricultural canal. Adjacent waters contribute greatly to the fish communities of the river and adjoining Lakes Huron and Erie, especially in terms of the number and quantity of forage species.     

Downstream movements of young-of-the-year fishes in Catamaran Brook and the Little Southwest Miramichi River, New Brunswick

Downstream movements of young-of-the-year fish in Catamaran Brook and the Little Southwest Miramichi River, New Brunswick, Canada were monitored by drift sampling during June and July of 1994, 1995 and 1996. Atlantic salmon Salmo salar , white sucker Catostomus commersoni , Cyprinidae, and sea lamprey Petromyzon marinus , were the most commonly captured taxa. All taxa moved downstream almost exclusively at night. Movement was greatest near midnight then declined towards dawn. Drift abundances peaked in mid-June for Atlantic salmon, late June for white sucker, and early July for Cyprinidae. Dates of peak movement were earlier in the Little Southwest Miramichi River than in Catamaran Brook for all taxa. Salmon fry captured in drift samplers were shorter than salmon fry captured by electrofishing near the sampling sites. Salmon fry captured in Catamaran Brook drift samplers were heavier at length than those captured in Little Southwest Miramichi River drift samplers. Results suggest that Catamaran Brook provides relatively better habitat for Atlantic salmon fry growth and relatively poorer habitat for larval white sucker growth than the Little Southwest Miramichi River.     

Home range of the Japanese fluvial sculpin, Cottus pollux, in relation to nocturnal activity patterns

Patterns of space use related to the activity of individual Japanese fluvial sculpins, Cottus pollux, were examined during the non-breeding season, in the upper reaches of the Inabe River, central Japan. Sculpins appeared more frequently at night than in daytime. Among 31 recaptured sculpins, 30 (96.8%) showed nocturnal activity patterns, there being no fish which exhibited an entirely diurnal activity pattern. Of 21 sculpins captured both in daytime and at night, the most common pattern of space use (n = 14, 66.7%) was that in which the nocturnal home range entirely encompassed the diurnal range. Overall, nocturnal home ranges were significantly larger than diurnal ranges. Active sculpins were rarely found on sand-associated substrata in daytime, but were seen more frequently on such substrata at night.     

Using spatial, seasonal, and diel drift patterns of larval Lost River suckers Deltistes luxatus (Cypriniformes: Catostomidae) and shortnose suckers Chasmistes brevirostris (Cypriniformes: Catostomidae) to help identify a site for a water withdrawal structure on the Williamson River, Oregon

A small irrigation diversion dam near Chiloquin, Oregon, was removed and replaced with a pump station to improve fish passage for Lost River suckers (Deltistes luxatus) and shortnose suckers (Chasmistes brevirostris) entering the Sprague River on their spawning migrations. During the developmental phase of the pump station, a need was identified to better understand the larval drift characteristics of these endangered catostomids in order to reduce entrainment into the irrigation system. The spatial, seasonal, and diel distribution of drifting larvae was measured during the 2004 spawning season at two proposed sites on the Williamson River where the pump station could be located. Larval drift for both species coincided with the irrigation season making them subject to entrainment into the irrigation system. Drift occurred almost exclusively at night with larvae entering the drift at sunset and exiting the drift at sunrise. Nighttime larval densities were concentrated near the surface and at midchannel at both sites. Densities were generally greater on the side of mid-channel with greater flow. During early morning sampling we detected a general shift in larval drift from surface to subsurface drift. We also observed an increase in larval densities towards the shore opposite from the proposed pump station at the upper site whereas larval densities remained high at midchannel at the lower site. During daytime sampling, the few larvae that were collected were distributed throughout the water column at both pump sites. This study found that larvae drifting during all time periods were generally distributed further across the cross section, deeper in the water column, and closer to where the proposed water withdrawal structure would be built at the downstream site when compared to the upstream site. Recommendations were provided to locate the withdrawal facility at the upstream site and operate it in a manner such that larval entrainment would likely be minimized.     

Invading species in the Eel River, California: successes, failures, and relationships with resident species

We examined invasions of non-native fishes into the Eel River, California. At least 16 species of fish have been introduced into the drainage which originally supported 12–14 fish species. Our study was prompted by the unauthorized introduction in 1979 of Sacramento squawfish, Ptychocheilus grandis, a large predatory cyprinid. From 1986 to 1990, we conducted growth and diet studies of squawfish, conducted intensive surveys of the distribution and habitat associations of both native and introduced species, and examined the nature of species-habitat and interspecies relationships. We found no evidence for increased growth or expanded feeding habits, compared to native populations, of Sacramento squawfish as they invaded the Eel River drainage. Ten of the introduced species were well established, with four species limited to a reservoir and six species established in streams. The success or failure of introductions of stream species appeared to be a function of the ability of a species to survive the fluctuating, highly seasonal, flow regime. The present mixture of native and exotic species has not formed stable fish assemblages but it seems likely that four habitat-associated assemblages will develop. The overall effect of the successful species introductions has been to assemble a group of species, with some exceptions, that are native to and occur together in many California streams. The assemblages now forming are similar to those found in other California streams. The assemblage characterized by squawfish and suckers is likely to be resistant to invasion, in the absence of human caused habitat modifications.     

Production and dispersion of freshwater,anadromous, and marine fish larvae in and around a river plume in subarctic Hudson Bay,Canada

From 1988 to 1990, fish larvae were sampled before, during, and after ice breakup within and outside the plume of the Great Whale River off Kuujjuarapik, southeastern Hudson Bay, Canada. Arctic cod (Boreogadus saida) and sand lance (Ammodytes spp.) were the most abundant larvae. Half of the larval fish taxa emerged before the ice broke up in the Bay. The highest densities of Arctic cod, sand lance, slender eelblenny, and gelatinous snailfish larvae were in salinities exceeding 25 practical salinity units (p.s.u.). Arctic shanny, sculpins, and capelin larvae were more abundant at salinities between 1 and 25 p.s.u.. Burbot and coregonid larvae were clearly associated with fresh or brackish waters even when caught in the Bay. The timing and extent of the Great Whale River freshet influenced the distribution of marine fish larvae in southeastern Hudson Bay and determined the moment when the larvae of anadromous and freshwater species entered the Bay.Contribution to the research programs of GIROQ (Groupe inter-universitaire de recherches océanographiques du Québec) and Institut Maurice Lamontagne (Department of Fisheries and Oceans, Canada)     

Secondary and tertiary stress responses to BKME exposure in the St. Maurice River fish populations

In the St-Maurice River, Canada, white suckers (Catostomus commersoni) collected at two stationslocated downstream of a bleached kraft mill effluent(BKME) outfall exhibited increased muscle lipidconcentrations relative to upstream reference fish.White suckers collected in a physicochemicallycomparable but uncontaminated river, also demonstratedan increasing trend of lipid accumulation withdistance downstream. The similar general trends inboth rivers may result from a river continuum in whichincreasing loads of nutrients with distance downstreamincrease the energy available to fish.However, the general trends differed in two respects.The gradient of lipid accumulation in the St. MauriceR. was irregular, suggesting a sharply increasednutrient input by BKME. Secondly, in the referenceGatineau river, increased lipid reserves wereaccompanied by increased growth and reproductiveeffort relative to body size. In contrast, increasedgrowth rates in the contaminated St. Maurice River wereaccompanied by a reduced reproductive effort relativeto body size. The failure to translate increasedenergy intake, as indicated by increased musclelipids, into increased reproductive effort suggestsone or more components of BKME have a toxic effect.Accelerated river enrichment contributed by thedischarge of the bleached kraft effluent combined withthe natural river continuum made it difficult toisolate the reproductive effects related to effluentexposure.     

Distribution and abundance of young fish in Chenal Ecarte and Chematogen Channel in the St. Clair River delta,Ontario

Samples of fish larvae collected in 1983, 1984, and 1986 in two distributary channels of the St. Clair River delta were characteristically rich in species (a total of 48) and low in abundance (generally less than a mean of 5 100 m^-3 of water filtered). Most species were residents of the delta; others apparently hatched in tributaries of the St. Clair River or in southern Lake Huron, and drifted into the delta. Highest species diversity was nearshore, although largest catches of larvae were of rainbow smelt, gizzard shad, and alewife, which were found mainly in mid-channel. Cyprinids (17 species) were better represented than other families.