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Factors of ecologic succession in oligotrophic fish communities of the Laurentian Great Lakes

Oligotrophic fish communities of the Great Lakes have undergone successive disruptions since the mid-1800s. Major contributing factors have been intensive selective fisheries, extreme modification of the drainage, invasion of marine species, and progressive physical–chemical changes of the lake environments. Lake Ontario was the first to be affected as its basin was settled and industrialized earliest, and it was the first to be connected by canals to the mid-Atlantic where the alewife ( Alosa pseudoharengus ) and sea lamprey ( Petromyzon marinus ) which ultimately became established in the Great Lakes were abundant. Oligotrophic fish communities were successively disrupted in Lakes Erie, Huron, Michigan, and Superior as the affects of population growth, industrialization, and marine invaders spread upward in the Laurentian drainage.The degree and sequence of response of families offish and species within families differed for each factor, but the sequence of change among families and species has been the same in response to each factor as it affected various lakes at different times. The ultimate result of the disruption of fish communities has been a reduction of productivity of oligotrophic species that ranges from extreme in Lake Ontario to moderate in Lake Superior, and which has reached a state of instability and rapid change in the upper three Great Lakes by the rnid-1900s similar to the situation in Lake Ontario in the mid-1800s. Since oligotrophic species (primarily salmonines, coregonines, and deepwater cottids) are the only kinds of fish that fully occupied the entire volume of the deepwater Great Lakes (Ontario, Huron, Michigan, and Superior), the fish biomass of these lakes has been reduced as various species declined or disappeared. In Lake Erie, which is shallow, and in the shallow bays of the deep lakes, oligotrophic species were replaced by mesotrophic species, primarily percids, which have successively increased and declined. All oligotrophic species are greatly reduced or extinct in lakes Ontario and Erie, and are in various stages of decline in lakes Huron, Michigan, and Superior, from greatest to least, respectively. The percids appear to be near the end of their sequence of succession in lakes Erie, Ontario, and Huron (primarily Saginaw Bay) where only the yellow perch ( Perca flavescens ) remains abundant. The yellow perch appears to be on the brink of decline in Lake Erie, which has been more severely influenced by water quality change than the other lakes.

Journal of the Fisheries Research Board of Canada↗

Experimental infection of the endangered bonytail chub (Gila elegans) with the Asian fish tapeworm (Bothriocephalus acheilognathi): impacts on survival, growth, and condition

Bothriocephalus acheilognathi Yamaguti, 1934, a tapeworm known to be pathogenic to some fish species, has become established in the endangered humpback chub (Gila cypha Miller, 1964) in Grand Canyon, USA, following the tapeworm’s introduction into the Colorado River system. The potential impact of this tapeworm on humpback chub was studied by exposing the closely related bonytail chub (Gila elegans Baird and Girard, 1853) to the parasite under a range of conditions that included potential stressors of humpback chub in their natal waters, such as abrupt temperature change and a limited food base. Survival of infected fish under low food rations was considerably lower than that of control fish, and mortality of infected fish began 20 days earlier. Growth of infected fish was significantly reduced, and negative changes in health condition indices were found. No significant negative impacts were revealed from the synergistic effects between temperature shock and infection. Bothriocephalus acheilognathi does present a potential threat to humpback chub in Grand Canyon and should be considered, along with conventional concerns involving altered flow regimes and predation, when management decisions are made concerning conservation of this endangered species.

Arizona↗

Agricultural sources of contaminants of emerging concern and adverse health effects on freshwater fish

Agricultural contaminants of emerging concern (CECs) are generally thought of as certain classes of chemicals associated with animal feeding and production facilities. Veterinary pharmaceuticals used in animal food production systems represent one of the largest groups of CECs. In our review, we discuss the extensive increase in use of antibiotics in animal feeding operations (AFOs) around the world. AFOs are a major consumer of antibiotics and other veterinary pharmaceuticals and over the past decade there has been growing information on the occurrence, release, and fate of CECs from animal food production operations, including the application of pharmaceutical-containing manure to agricultural fields and releases from waste lagoons. Concentrations of CECs in surface and ground water in proximity to AFOs correspond to their presence in the AFO wastes. In many cases, the environmental concentrations of agriculturally-derived CECs are below toxicity thresholds. Hormones and hormone replacement compounds are a notable exception, where chemical concentrations near AFOs can exceed concentrations known to cause adverse effects on endocrine-related functions in fish. In addition, some agricultural pesticides, once thought to be safe to non-target organisms, have demonstrated endocrine-related effects that may pose threats to fish populations in agricultural regions. That is, we have pesticides with emerging concerns, thus, the concern is emerging and not necessarily the chemical. In this light, one must consider certain agricultural pesticides to be included in the list of CECs. Even though agricultural pesticides are routinely evaluated in regulatory testing schemes which have been used for decades, the potential hazards of some pesticides have only recently been emerging. Emerging concerns of pesticides in fish include interference with hormone signaling pathways; additive (or more than additive) effects from pesticide mixtures; and adverse population-level effects at concentrations below predicted toxicity thresholds. Consequently, there is a need to evaluate the environmental concerns related to pesticide exposures to fish populations based on current biological and toxicological techniques. This presentation reviews some of the agricultural chemicals that have emerged as contaminants of concern and potentially threaten fish populations in agricultural watersheds.

Conference Paper↗

Comparison of individual and pooled sampling methods for detecting bacterial pathogens of fish

Examination of finfish populations for viral and bacterial pathogens is an important component of fish disease control programs worldwide. Two methods are commonly used for collecting tissue samples for bacteriological culture, the currently accepted standards for detection of bacterial fish pathogens. The method specified in the Office International des Epizooties Manual of Diagnostic Tests for Aquatic Animals permits combining renal and splenic tissues from as many as 5 fish into pooled samples. The American Fisheries Society (AFS) Blue Book/US Fish and Wildlife Service (USFWS) Inspection Manual specifies the use of a bacteriological loop for collecting samples from the kidney of individual fish. An alternative would be to more fully utilize the pooled samples taken for virology. If implemented, this approach would provide substantial savings in labor and materials. To compare the relative performance of the AFS/USFWS method and this alternative approach, cultures of Yersinia ruckeri were used to establish low-level infections in groups of rainbow trout (Oncorhynchus mykiss) that were sampled by both methods. Yersinia ruckeri was cultured from 22 of 37 groups by at least 1 method. The loop method yielded 18 positive groups, with 1 group positive in the loop samples but negative in the pooled samples. The pooled samples produced 21 positive groups, with 4 groups positive in the pooled samples but negative in the loop samples. There was statistically significant agreement (Spearman coefficient 0.80, P < 0.001) in the relative ability of the 2 sampling methods to permit detection of low-level bacterial infections of rainbow trout.

Journal of Veterinary Diagnostic Investigation↗

Status of native stream fishes within selected protected areas of Niobrara River in western Nebraska

Lotic systems within the Great Plains are characterized by highly fluctuating conditions through both space and time. Fishes inhabiting these systems have adopted specific life-history strategies to survive in such environments; however, anthropogenic disturbance to prairie streams has resulted in declines and extirpation of many native stream fishes. Terrestrial protected areas (i.e., parks and reserves) are designated to support native flora and fauna and, it is assumed, to provide protection to native fishes. We assessed the presence and relative abundance of stream fish populations within protected areas along the Niobrara River in western Nebraska based on data collected during 1979, 1989, 2008, and 2011. The spatial extent of protection, landscape changes resulting in degraded physiochemical parameters, and introduced species may reduce the effectiveness of these terrestrial protected areas in protecting native fishes in Great Plains stream environments.

Great Plains Research↗

Broad scale community-level larval fish survey of southern Lake Erie

The early-life history stages of fish are sensitive to environmental change and therefore can indicate habitat quality as well as help predict recruitment of resident and transient fishes. In 2019, as part of the Lake Erie Cooperative Science and Monitoring Initiative, we conducted a lake-wide assessment of the ichthyoplankton community in U.S. nearshore waters and international offshore waters. The goal of this work was to characterize the larval fish community across the lake and assess species composition, phenology, and distribution of larvae. Ichthyoplankton were sampled weekly using bongo nets at ports beginning at the Detroit River and along the southern shore of Lake Erie to Dunkirk, NY, and less frequently in the Niagara River and offshore areas. Larval fish were present from March 26 through August 29, 2019. The first taxon to emerge was Lake Whitefish in all basins, followed by Walleye, Yellow Perch, and catostomids, depending on port. Mean total density peaked in mid-June due to high catches of Gizzard Shad, Morone spp., and Freshwater Drum in the western basin. Few fish were collected in the offshore sites. Taxa richness, diversity, and larval density were higher in the western basin and lower in the central and eastern basins, generally following the productivity gradient. This was the first study to provide a comprehensive community assessment of the ichthyoplankton community of Lake Erie and can provide a baseline to assess future change, especially in community composition or phenology, of larvae which are likely to respond to climate and habitat change.

Lake Erie↗

Effects of fish populations on Pacific Loon (Gavia pacifica) and Yellow-billed Loon (G. adamsii) lake occupancy and chick production in northern Alaska

Predator populations are vulnerable to changes in prey distribution or availability. With warming temperatures, lake ecosystems in the Arctic are predicted to change in terms of hydrologic flow, water levels, and connectivity with other lakes. We surveyed lakes in northern Alaska to understand how shifts in the distribution or availability of fish may affect the occupancy and breeding success of Pacific ( Gavia pacifica ) and Yellow-billed Loons ( G. adamsii ). We then modeled the influence of the presence and abundance of five fish species and the physical characteristics of lakes (e.g., hydrologic connectivity) on loon lake occupancy and chick production. The presence of Alaska blackfish ( Dallia pectoralis ) had a positive influence on Pacific Loon occupancy and chick production, which suggests that small-bodied fish species provide important prey for loon chicks. No characteristics of fish species abundance affected Yellow-billed Loon lake occupancy. Instead, Yellow-billed Loon occupancy was influenced by the physical characteristics of lakes that contribute to persistent fish populations, such as the size of the lake and the proportion of the lake that remained unfrozen over winter. Neither of these variables, however, influenced chick production. The probability of an unoccupied territory becoming occupied in a subsequent year by Yellow-billed Loons was low, and no loon chicks were successfully raised in territories that were previously unoccupied. In contrast, unoccupied territories had a much higher probability of becoming occupied by Pacific Loons, which suggests that Yellow-billed Loons have strict habitat requirements and suitable breeding lakes may be limited. Territories that were occupied had high probabilities of remaining occupied for both loon species.

Alaska↗

Extinction rates in North American freshwater fishes, 1900-2010

Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). In the twentieth century, freshwater fishes had the highest extinction rate worldwide among vertebrates. The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050.

BioScience↗

An evaluation of three fish surveys in the San Francisco Estuary, 1995–2015

Resource managers rely on long-term monitoring surveys conducted in the San Francisco Estuary to evaluate the status and trends of resident fish populations in this important region. These surveys are potentially confounded because of the incomplete detection of individuals and species, the magnitude of which is often related to the same factors that affect fish populations. We used multistate occupancy estimators to evaluate the distribution, abundance, and detection probability of four fish species collected during 1995–2015 with three long-term surveys. Detection probabilities varied positively with fish abundance and negatively with Secchi depth. Detection varied among species and was greatest for the 20-mm Survey and least for the midwater trawl used for the midwater trawl used in the San Francisco Bay Study. Incomplete detection resulted in underestimates of occupancy and abundance across species and surveys and were greatest for the Bay Study. However, trends in occupancy and abundance of the study period appeared to be unbiased. Fish occupancy and abundance were generally related to salinity or specific conductance, day-of-the year, and water temperature, but the nature of the relations varied among surveys and species. There also was strong spatial and temporal dependence in species-specific occupancy and abundance that changed through time and were unrelated to the covariates considered. Our results suggest that managers consider incorporating methods for estimating detection and adjusting data to ensure data quality. Additionally, the strong spatio-temporal patterns in the monitoring data suggest that existing protocols may need to be modified to ensure that data and inferences reflect system-wide changes rather than changes at a specific set of non-randomly selected locations.

California↗

Tagging experiments with lake trout, whitefish, and other species of fish from Lake Michigan

A total of 2,902 Lake Michigan fish was tagged and released, 48.8 per cent of which were lake trout and 85 per cent lake trout, lake herring, and whitefish. A total of 388 fish or 13.4 per cent was recaptured. The percentages of returns indicated a tremendous fishing intensity for lake trout, whitefish, and sturgeon. About 81 per cent of the recaptured fish were retaken within a radius of 25 miles from the port of tagging (Port Washington, Wisconsin). Lake trout, rainbow trout, and sturgeon were found to be extensive travelers; lake herring, whitefish, chubs, pilots, and perhaps perch did not migrate so extensively. Lake trout, herring, and whitefish tended to move in a northerly direction, perch in a southerly, and rainbow trout in all easterly, toward the Michigan shore. Sturgeon apparently roam all over the lake. Fifty-three per cent of the recovered lake trout were recaptured within one year of release, 73 per cent within 25 miles from Port Washington. It required three years for the trout to become fairly well scattered throughout the lake. With the attainment of adulthood lake trout moved in all directions from the port of release, although nearly 50 per cent of the adults were retaken within 25 miles from this port. Fish moved across state boundaries. Data are given on the growth and estimated age of the tagged lake trout, rainbow trout, whitefish, and sturgeon. The minimum size limits of lake trout and whitefish on the Great Lakes are economically unsound&ndash;they are too low&ndash;because they permit the capture of these species at a time of most rapid increase in weight.

Transactions of the American Fisheries Society↗

Fish abundance and population stability in a reservoir tailwater and an unregulated headwater stream

Fish abundance and population stability were compared in the tailwater and in an unregulated tributary of Barren River Lake, a flood control reservoir in south central Kentucky. Fish abundance was greater in the tailwater near the dam and was dominated by three species common in the reservoir: gizzard shad ( Dorosoma cepedianum ), bluegills ( Lepomis macrochirus ), and white crappies ( Pomoxis annularis ). Three riverine suckers were less abundant in the tailwater than in the unregulated stream: northern hog suckers ( Hypentelium nigricans ), black redhorse ( Moxostoma duquesnei ), and golden redhorse ( Moxostoma erythrurum ). The fish populations in the tailwater, particularly common carp ( Cyprinus carpio ), northern hog suckers, black redhorse, and golden redhorse, were less stable than those in the unregulated stream. Population stability is defined as the extent to which fish remain in a stream section. This study suggests that the occurrence of reservoir species in the tailwater was the result of fish passage from the reservoir during high discharges in fall and winter. Reservoir operations (altered flow, low summer water temperature, and poor summer water quality) probably were responsible for the unstable populations of common carp and riverine suckers in the tailwater.

Kentucky↗

Use of diagnostic bones to identify and estimate original lengths of ingested prey fishes

We examined and measured cleithra, dentaries, opercles, and pharyngeal arches – bones found to persist during digestion of most prey fish – to identify 24 prey fish species and back-calculate their original fork length. Eighteen of the 24 species examined could be easily distinguished; however, for certain congenerics, identification was neither consistent nor reliable for all bones within the size ranges examined. Relations between bone length and fish length were linear for 14 species for which the sample sizes were adequate ( N > 30); coefficients of determination ( r 2 ) ranged from 0.79 to 0.99. Diagnostic characteristics and measurements of these bones provided reliable identification of genera and species and estimates of original fork lengths of partly digested prey fish from three predators. This method, compared with that of examining only prey fish in a measurable condition, greatly increased the amount of dietary information available from gut analysis.

Transactions of the American Fisheries Society↗

Interaction between native and nonnative fish of the upper Muddy River, Nevada

I investigated interactions between native and nonnative fishes in the upper Muddy River system to add insight into (1) the mechanism causing the decline of the Moapa dace Moapa coriacea after the introduction of the shortfin molly Poecilia mexicana , (2) the reason Moapa White River springfish Crenichthys bailevi moapae were less affected by the introduction, and (3) the reason interactions between natives is relatively benign. I investigated the hypothesis that the shortfin molly caused the decline of the Moapa dace through competition or predation on larvae, pressures not experienced by the Moapa White River springfish. Relative interspecific competition was analyzed by contrasting the ranges of spatial and dietary overlap among larval, juvenile, and adult life stages. There appeared to be moderate to low spatial overlap between the various life stages of native and nonnative fishes. Overlap in diet was highest between adult Moapa White River springfish and shortfin mollies. Laboratory experiments suggested that shortfin mollies prey vigorously upon fish larvae. In terms of spatial habitat use, Moapa White River springfish larvae were less available to adult shortfin mollies for consumption than were Moapa dace larvae. When predation on larvae is the mechanism by which nonnative fish reduce native forms, aggressiveness of the predator and the degree to which the predator overlaps in habitat with the prey may influence the degree to which a native fish population is affected.

Transactions of the American Fisheries Society↗

Fish assemblages and environmental variables associated with hard-rock mining in the Coeur d'Alene River basin, Idaho

As part of the U.S. Geological Survey's National Water Quality Assessment Program, fish assemblages, environmental variables, and associated mine densities were evaluated at 18 test and reference sites during the summer of 2000 in the Coeur d'Alene and St. Regis river basins in Idaho and Montana. Multimetric and multivariate analyses were used to examine patterns in fish assemblages and the associated environmental variables representing a gradient of mining intensity. The concentrations of cadmium (Cd), lead (Pb), and zinc (Zn) in water and streambed sediment found at test sites in watersheds where production mine densities were at least 0.2 mines/km 2 (in a 500-m stream buffer) were significantly higher than the concentrations found at reference sites. Many of these metal concentrations exceeded Ambient Water Quality Criteria (AWQC) and the Canadian Probable Effect Level guidelines for streambed sediment. Regression analysis identified significant relationships between the production mine densities and the sum of Cd, Pb, and Zn concentrations in water and streambed sediment (r 2 = 0.69 and 0.66, respectively; P < 0.01). Zinc was identified as the primary metal contaminant in both water and streambed sediment. Eighteen fish species in the families Salmonidae, Cottidae, Cyprinidae, Catostomidae, Centrarchidae, and Ictaluridae were collected. Principal components analysis of 11 fish metrics identified two distinct groups of sites corresponding to the reference and test sites, predominantly on the basis of the inverse relationship between percent cottids and percent salmonids (r = -0.64; P < 0.05). Streams located downstream from the areas of intensive hard-rock mining in the Coeur d'Alene River basin contained fewer native fish and lower abundances as a result of metal enrichment, not physical habitat degradation. Typically, salmonids were the predominant species at test sites where Zn concentrations exceeded the acute AWQC. Cottids were absent at these sites, which suggests that they are more severely affected by elevated metals than are salmonids.

Idaho↗

Detection of Aeromonas salmonicida the mucus of salmonid fishes

Mucus of salmonids was evaluated as a source for nonlethal detection of the pathogen Aeromonas salmonicida in fish. The bacterium was readily isolated from mucus on dilution plates when Coomassie Brilliant Blue agar was the primary plating medium. Kidney samples from the fish that served as sources of mucus were similarly processed. Infection was detected in 56% of mucus samples from lake trout Salvelinus namaycush that were undergoing an epizootic of furunculosis, but only 6% of the kidneys from these fish were positive for the pathogen. Only 1% of asymptomatic brown trout Salmo trutta sampled at another fish hatchery had A. salmonicida in their mucus, and none had a kidney infection. Combined results from the examination of two pools of Atlantic salmon Salmo salar reared at a third hatchery indicated that 37% of these fish had mucus infections caused by A. salmonicida , but only 4% of the kidneys were infected.

Journal of Aquatic Animal Health↗

Differences in detection of Aeromonas salmonicida in covertly infected salmonid fishes by the stress-inducible furunculosis test and culture-based assays

Accurate detection of Aeromonas salmonicida subsp. salmonicida (the cause of furunculosis disease) in covertly infected salmonids is difficult and is a cause of concern for those involved in fish health inspection and resource management programs. In this study, we examined populations of brook trout Salvelinus fontinalis , Atlantic salmon Salmo salar , and lake trout Salvelinus namaycush that previously sustained natural episodes of furunculosis. Consequently, the sampled fish were presumed to harbor latent infections. Mucus, gill, liver, kidney, heart, spleen, and intestine samples ( N = 100 fish per group sampled) were processed and examined by (1) direct dilution counts and (2) quadrant streaking after a 48‐h pre‐enrichment in trypticase soy broth (TSB). Another subsample of fish from each group was then subjected to stress‐inducible furunculosis tests. Stress tests detected A. salmonicida in three of four groups of fish that were examined whereas the pathogen was detected in only two of the groups analyzed with culture‐based assays. Although pre‐enrichment in TSB enhanced detection within internal sampling sites including the liver, heart, spleen, and kidney, enrichment did not enhance detection from mucus, gill, or intestinal samples.

Journal of Aquatic Animal Health↗

Utility of splenic macrophage aggregates as an indicator of fish exposure to degraded environments

The utility of splenic macrophage aggregates (MAs) as an indicator of fish exposure to degraded environments was evaluated in several species of estuarine fishes as part of the Environmental Protection Agency's Environmental Monitoring and Assessment Program–Estuaries (EMAP-E). Using image analysis, we measured the number and mean size of MAs per square millimeter on tissue sections of spleen from 983 fishes representing seven species from 266 stations scattered across coastal estuaries of the Gulf of Mexico. At 16 stations, at least one fish exhibited a high density of MAs (>40 MAs/mm 2 ). Densities of MAs that exceeded 40/mm 2 correlated with exposure to either hypoxic conditions or sediment contamination. Fisher's exact test showed that the observed frequencies of joint occurrence between high numbers of MAs and both high sediment contaminants and low dissolved oxygen were significantly greater than the expected background frequencies. For all 16 sites where MAs were greater than 40/mm 2 , sediments displayed at least one contaminant at a concentration in the highest 5% of those observed for all Gulf of Mexico stations. Additionally, comparison of subjective visual analyses with the image analysis measurements showed a strong correlation, indicating that similar analyses can be performed without computer image analysis. This study demonstrates that splenic MAs are effective biotic indicators for discriminating between fish exposed to degraded and nondegraded environments.

Alabama, Florida, Louisiana, Mississippi, Texas↗

Effects of an agricultural drainwater bypass on fishes inhabiting the Grassland Water District and the lower San Joaquin River, California

The Grassland Bypass Project, which began operation in September 1996, was conceived as a means of diverting brackish selenium-contaminated agricultural drainwater away from canals and sloughs needed for transporting irrigation water to wetlands within the Grassland Water District (the Grasslands), Merced County, California. The seleniferous drainwater is now routed into the San Luis Drain for conveyance to North Mud Slough and eventual disposal in the San Joaquin River. The purpose of this study was to determine the extent to which the Grassland Bypass Project has affected fishes in sloughs and other surface waters within and downstream from the Grasslands. During September-October 1997, 9,795 fish representing 25 species were captured at 13 sampling sites. Although several species exhibited restricted spatial distributions, association analysis and cluster analysis failed to identify more than one fish species assemblage inhabiting the various sites. However, seleniferous drainwater from the San Luis Drain has influenced selenium concentrations in whole fish within North Mud Slough and the San Joaquin River. The highest concentrations of selenium (12-23 ??g/g, dry weight basis) were measured in green sunfish Lepomis cyanellus from the San Luis Drain where seleniferous drainwater is most concentrated, whereas the second highest concentrations occurred in green sunfish (7.6-17 ??g/g) and bluegills Lepomis macrochirus (14-18 ??g/g) from North Mud Slough immediately downstream from the drain. Although there was some variation, fish in the San Joaquin River generally contained higher body burdens of selenium when captured immediately below the mouth of North Mud Slough (3.1-4.8 ??g/g for green sunfish, 3.7-5.0 ??g/g for bluegills) than when captured upstream from the mouth (0.67-3.3 ??g/g for green sunfish, 0.59-3.7 ??g/g for bluegills). Waterborne selenium was the single most important predictor of selenium concentrations in green sunfish and bluegills, as judged by results from multiple-regression analyses. Among bluegills, water temperature also contributed to the prediction of selenium body burdens.

California↗