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At least 595 records · Page 33Linked to original sources

USGS1999

Water quality, physical habitat, and fish-community composition in streams in the Twin Cities metropolitan area, Minnesota, 1997-98

Water quality, physical habitat, and fish-community composition were characterized at 13 Twin Cities metropolitan area streams during low-flow conditions, September 1997. Fish communities were resampled during September 1998. Sites were selected based on a range of human population density. Nutrient concentrations were generally low, rarely exceeding concentrations found in agricultural streams or water-quality criteria. Seventeen pesticides and five pesticide metabolites were detected, with atrazine being the only pesticide detected at all 13 streams. Colony counts of fecal coliform bacteria ranged from 54 to greater than 11,000 colonies per 100 mL. Instream fish habitat was sparse with little woody debris and few boulders, cobble, or other suitable fish habitat. Thirty-eight species and one hybrid from 10 families were collected. Fish communities were characterized by high percentages of omnivores and tolerant species with few intolerant species. Index of Biotic Integrity scores were low, with most streams rating fair to very poor. Percent impervious surface was positively correlated with sodium and chloride concentrations and human population density, but was negatively correlated with fish species richness and diversity. Urban land use and human population density influence fish communities and water quality in Twin Cities metropolitan area streams. Other factors that may influence fish community composition include percent impervious cover, water chemistry, water temperature, geomorphology, substrate, instream habitat, and migration barriers.

Minnesota↗

USGS2019

Eradication of two non-native cichlid fishes in Miami, Florida (USA)

The proliferation of non-native fishes in Florida is a serious problem, and new species continue to be introduced to the state. Fishes in the Family Cichlidae have been especially successful colonizers of south Florida freshwater habitats. Herein we report a multi-agency effort to eradicate two non-native cichlid fishes in Miami, Florida (Bay Snook Petenia splendida and Blue Mbuna Labeotropheus fuelleborni). These fishes were removed before they were observed in the extensive, interconnected canal system through which they may have been able to expand throughout south Florida and access protected areas such as Everglades National Park. The study site, Pinecrest Gardens, is important because it contains remnant coastal cypress-strand habitat in an increasingly urbanized landscape that historically provided refuge to native amphidromous fishes and invertebrates. The project took considerable time (3.5 years), and we detail in this report how it evolved from a focus on isolating the non-native fishes and reducing their population sizes to an eradication. Gardens’ staff hydrologically isolated their ponds from nearby waterbodies by plugging a culvert with a solid gate. That provided the interagency team with more time to remove the potential threats. Compromises were made between fish management strategies and the Gardens’ priorities. Hurricane impacts helped shift priorities to more aggressive fish-management strategies. Cooperation among several federal and state agencies, as well as the Gardens, was key to the project’s success. We hope this effort may serve as a model for removing non-native species before they spread into ecosystems where eradication is not practical.

Florida↗

USGS2019

Evaluation of an acoustic fish deterrent system in shallow water application at the Emiquon Preserve, Lewistown, IL.

Expansion of non-native fish have caused ecological and economic damage and can negatively impact native fish populations. Current research on deterrent technologies for bighead Hypophthalmichthys nobilis and silver carp H. molitrix have primarily focused on reducing upstream movement in large river lock approaches. However, there is also interest in excluding carp from smaller-scale locations. A water control structure at Emiquon Preserve, Lewistown, Illinois, USA reconnected the Preserve’s wetland lakes to the Illinois River, and is a pinch point that site managers seek to deter immigration of non-native fishes without restricting native fish movement. One possible deterrent strategy that was evaluated within the water control structure in 2017 was the use of a 100 hp boat motor acoustic stimulus. Two underwater speakers were installed in each of two culverts to discourage fish movement though the water control structure. Fish passage was monitored using a series of passive integrated transponder (PIT) antennas in a confined study area. A combination of 176 fish consisting of seven different species (native and non-native) were implanted with PIT tags and relocated downstream of the water control structure. Over 2 days of periodic playback of the acoustic stimulus, 29% of tagged silver carp that were detected crossed though the active underwater speaker array. The acoustic treatment did not significantly reduce silver carp or native centrarchid passage through the culverts. However, numerous silver carp were observed jumping out of the acoustically active culvert at the onset of the stimulus. The acoustic stimulus, especially the frequencies to which silver carp are most sensitive to (< 2000 Hz), rapidly attenuated in the water control structure (water depth 0.55–0.38 m). Depth related attenuation observed in and around the water control structure may have reduced the efficacy of the acoustic fish deterrent system at this location.

Illinois↗

USGS2018

Comparison of a prepositioned areal electrofishing device and fixed underwater videography for sampling riverine fishes

Prepositioned areal electrofishing devices (PAEDs) are used to evaluate microhabitat use by fishes because they minimize fright biases associated with traditional electrofishing techniques (e.g., boat electrofishing). Similarly, fixed underwater videography (FUV) is commonly used to minimize the effect of observers on fish behavior. The specific objectives of this research were to evaluate estimates of taxonomic occurrence and diversity between PAEDs and FUV and determine an appropriate time interval between positioning and electrifying of a PAED to reduce effects of PAED positioning on fish occurrence. Video cameras were positioned instream at 28 locations on the Kootenai River, Idaho, prior to PAED deployment such that the entire immobilization zone of the PAED was captured on camera. Following a 4-min acclimation period, cameras recorded fish behavior approximately 15 min prior to and 20 min following PAED deployment. Electrical current was applied to the PAEDs for 20 s immediately following the FUV procedure, and immobilized fishes were collected and processed. Video footage was subsampled in the laboratory, and fishes in the video were identified and enumerated in 5-s or 20-s intervals. Fixed underwater videography sampled more taxa than PAEDs at any given site. However, fishes sampled with FUV were difficult to identify, and most individuals were classified as “unidentifiable.” Consequently, direct comparisons between FUV and PAEDs are limited. Our results indicate that PAEDs should remain undisturbed for a minimum of 12 min before the equipment is electrified. Both PAEDs and FUV provide an estimate of taxonomic occurrence, but logistical and financial constraints along with project objectives must be considered when selecting between these 2 gear types. Results from this study provide information on the effectiveness of each gear type as it relates to the characterization of riverine fish assemblages at a small spatial scale.

Western North American Naturalist↗

USGS2023

Evaluating the spatial and temporal distribution and ecology of Bighead and Silver Carp and native fishes of the lower Red River basin

We investigated the spatial and temporal distribution of Bighead Carp and Silver Carp (hereafter Carp) in the lower Red River basin of Arkansas. Our study objectives were: 1) determine the spatial and temporal extent of Bighead and Silver Carp in the Red River basin of Arkansas; 2) determine habitat associations of large river fish assemblages; and 3) summarize the demographics of Bighead and Silver Carp. We sampled 67 reaches in the lower Red River and its major tributaries for juvenile Carp and other small-bodied fishes (24 of the reaches were in the Arkansas portion of the Red River). We conducted repeated surveys in these reaches where the reaches were sampled 2-3 times over approximately 2 years representing 242 surveys (95 surveys in Arkansas). We completed adult Carp and native fish assemblage sampling across 61 reaches (22 reaches in Arkansas) where we also repeated surveys at these locations (245 total surveys, 100 surveys completed in Arkansas during the reporting period). We captured the most large-bodied fishes (including Carp) using gillnets and electrofishing, whereas fyke nets and seine hauls collected mainly smaller-bodied fishes. Hoop nets captured fewer fishes when compared to other gear types. We sampled 120,072 fishes, comprising 70 species and 41 genera, from the mainstem Red River in Arkansas. We used data associated with the entire catchment (including OK and TX data) to model the occupancy of adult fishes including both carp species. Carp tended to occupy reaches with the presence of slackwater habitat, that were deeper and narrower (lower habitat complexity), with higher discharge conditions, and were positively associated with chlorophyll-a concentrations. Adult and juvenile assemblage structure varied with reach scale attributes with notable differences among some taxonomically similar species. No carp under the age of 3 were sampled in the catchment. Bighead Carp and Silver Carp in the Red River catchment appear to live longer and grow larger than other populations. Silver Carp and Bighead Carp in the lower Red River had a theoretical maximum length (𝐿 ∞ ) of 920 and 1,348-mm TL, respectively. The oldest sampled Silver Carp and Bighead Carp were age 14 and 17, respectively. Bighead Carp growth was positively associated with warmer air temperatures and negatively associated with discharge variability. Similarly, Silver Carp growth was positively associated with warm air temperature and negatively associated with discharge variability. However, Silver Carp growth was also positively related to high discharge conditions and the variability of air temperature. Silver Carp annual mortality was relatively low and recruitment into the population appeared steady. It appears that Carp are likely coming from another catchment, have only limited or periodic successful reproduction in the study area, or spawn downriver in LA. Continued monitoring for reproductive success would be helpful. Moreover, if the goal is to greatly reduce or eliminate carp, then strategies that prevent further immigration before reproduction occurs or becomes more successful would be ideal. Targeted removal may then be useful for reducing numbers already in the catchment; however, there are also oxbow lakes that contain carp but appear only connected to the river during major floods (i.e., possible source locations).

Arkansas, Oklahoma, Texas↗

USGS2017

Sex difference in PCB concentrations of a catostomid fish

Unraveling the complexities associated with the relative differences in contaminant concentrations between the sexes of mature fish may provide insights into important behavioral and physiological differences between the sexes of not just fish but higher vertebrates as well. Whole-fish polychlorinated biphenyl (PCB) concentrations were determined in 25 mature female white suckers (Catostomus commersoni) and 26 mature male white suckers caught during their spawning run in the Kewaunee River, a tributary to Lake Michigan. Total length and weight were measured for each fish, and age of each fish was estimated from thin-sectioned otoliths. PCB concentration significantly increased with increasing total length, weight, and age. Consequently, three analysis of covariance (ANCOVA) models were fitted to the data to assess the effect of sex on white sucker PCB concentration. Based on model averaging, estimates of mean PCB concentrations in female and male white suckers were 185 and 219 ng/g, respectively. Thus, males were 18% greater in PCB concentration than females. We conclude that this difference between the sexes was most likely mainly driven by a higher rate of energy expenditure in males compared with females. Greater energy expenditure, owing to greater swimming activity and a higher resting metabolic rate , resulted in a higher rate of food consumption, which in turn led to a greater rate of PCB accumulation. Higher whole-fish PCB concentration in males compared with females has now been shown in nine different fish species. Our study represented the first documentation of this type of sex difference in a catostomid fish.

Kewaunee River, Lake Michigan↗

USGS2024

Coldwater fish in wadeable streams

Although we are consistent with the past edition of this volume regarding standard sampling techniques for wadeable, coldwater streams, this edition reflects recent literature, advances in calibrating numbers, and obtaining lengths of fish collected and provides additional clarity regarding effort. We also specify a minimum of two netters and one electrofisher operator for backpack electrofishing to allow capture of fish that “roll” downstream without surfacing (e.g., fish like sculpins, which lack swim bladders); however, as in the past edition, a minimum of one netter and one operator may be used on studies focused on fish with swim bladders, like salmonids (salmons and trouts). Finally, this chapter mentions specifically what factors should lead to standard adjustments to techniques to account for the range of habitat features typically encountered in headwater streams. Small, wadeable streams comprise most habitats available to fish in fluvial networks. Wadeable streams are generally less than 1 m deep, and fish can be sampled without the use of float craft. Cold waters are generally defined as having mean 7-d summer maximum water temperatures less than 20°C, providing habitat for coldwater fishes. Fish fauna of small, coldwater North American streams typically include salmonids, sculpins, minnows, sticklebacks, suckers, or lampreys (Hocutt and Wiley 1986). Standard sampling protocols provided herein apply most readily to salmonids because of their sport and commercial values (Johnson et al. 2007). Salmonids also have cultural values, are well studied and widely distributed, and act as predators, competitors, and prey (Lee et al. 1997). However, many of these methods can also be applied effectively to sample nonsalmonids. As interest in nonsalmonid species grows, further development and investigation of sampling methods for a broader diversity of species is expected (see section 8.5).

Book chapter↗

USGS2004

Distribution and abundance of pelagic fish in Lake Powell, Utah, and Lake Mead, Arizona-Nevada

Pelagic fish communities (waters with depths >20 m) of Lakes Powell and Mead were examined quarterly from 1995 to 1998 using vertical gill nets and a scientific echosounder. Nets captured a total of 449 fish consisting of striped bass (57%/45% [Lake Powell/Lake Mead]), threadfin shad (24%/50%), common carp (15%/4%), walleye (3%), channel catfish (2%), and rainbow trout (<1%). Each reservoir contained concentrations of pelagic species separated by expanses of habitat with few fish (<10 kg·ha⁻¹). Reservoirs experienced dramatic seasonal and annual fluctuations in pelagic biomass. Lake Powell's biomass peaked at the Colorado River at 709.7 (± 46.5) kg · ha⁻¹ and Lake Mead's reached 291.9 (± 58.2) kg · ha⁻¹ at Las Vegas Wash. These locations supported estimated fish densities of 124,668 fish · ha⁻¹ and 15,131 fish · ha⁻¹, respectively. Maximum reservoir biomass peaked in August 1996, with Lake Powell supporting 10,852,738 ± 5,195,556 kg (27.6 × 10⁻ fish) and Lake Mead 1,926,697 ± 892.994 kg (10.8 × 10⁻ fish). Biomass ebbed in May (1996 and 1997), when Lake Mead supported 65% (296,736 kg vs. 453,097 kg) and 62% (101,016 kg vs. 162,262 kg) of biomass levels found in Lake Powell.

Arizona, Nevada, Utah↗

USGS2005

A synthesis of ecological and fish-community changes in Lake Ontario, 1970-2000

We assessed stressors associated with ecological and fishcommunity changes in Lake Ontario since 1970, when the first symposium on Salmonid Communities in Oligotrophic Lakes (SCOL I) was held (J. Fish. Res. Board Can. 29: 613-616). Phosphorus controls implemented in the early 1970s were undeniably successful; lower food-web studies showed declines in algal abundance and epilimnetic zooplankton production and a shift in pelagic primary productivity toward smaller organisms. Stressors on the fish community prior to 1970 such as exploitation, sea lamprey ( Petromyzon marinus ) predation, and effects of nuisance populations of alewife ( Alosa pseudoharengus ) were largely ameliorated by the 1990s. The alewife became a pivotal species supporting a multi-million-dollar salmonid sport fishery, but alewife-induced thiamine deficiency continued to hamper restoration and sustainability of native lake trout ( Salvelinus namaycush ). Expanding salmonine populations dependent on alewife raised concerns about predator demand and prey supply, leading to reductions in salmonine stocking in the early 1990s. Relaxation of the predation impact by alewives and their shift to deeper water allowed recovery of native fishes such as threespine stickleback (Gasterosteus aculeatus) and emerald shiner ( Notropis atherinoides ). The return of the Lake Ontario ecosystem to historical conditions has been impeded by unplanned introductions. Establishment of Dreissena spp. led to increased water clarity and increased vectoring of lower trophic-level production to benthic habitats and contributed to the collapse of Diporeia spp. populations, behavioral modifications of key fish species, and the decline of native lake whitefish (Coregonus clupeaformis ). Despite reduced productivity, exotic-species introductions, and changes in the fish community, offshore Mysis relicta populations remained relatively stable. The effects of climate and climate change on the population abundance and dynamics of Lake Ontario fish were unknown at the time of SCOL I, but a temperature-time series begun in the late 1950s in the Kingston Basin has since provided evidence of climate warming and associated fish-community changes. We should expect ecological surprises in the coming decades that will challenge scientists and fishery managers especially as they face new exotic species, climate warming, and escalating stakeholder demands on the resource. Continuous long-term ecological studies were critical for interpreting changes in Lake Ontario's fish community over the past three decades and will be essential in the future for both scientific understanding and management of the fishery.

Technical Report↗

USGS2010

Mercury monitoring in fish using a non-lethal tissue biopsy method

The occurrence of mercury in fish is well-known and often occurs at levels that warrant restricted consumption by sensitive human populations. Because of this, local wildlife and health agencies have developed monitoring programs to identify the magnitude of fish contamination and changes through time. Monitoring mercury levels in fish typically requires killing fish for removal of a fillet. Recently, researchers have proposed the use of a non-lethal tissue biopsy plug method as a surrogate for analysis of the entire fillet. A non-lethal method is particularly desirable for sampling rare or endangered fish or highly valued fisheries. The Missouri Department of Conservation manages several fisheries where the public is sensitive to excessive fish removal, yet there is a desire for mercury information. One such example is the trophy smallmouth bass (Micropterus dolomieu) fishery in the Ozark’s Eleven Point River. Plug removal is not expected to affect fish survival in the shortterm. However, limited information is available on survival of fish for weeks or months after plug removal.

Missouri↗

USGS1990

Field manual for the investigation of fish kills

Preface Fish kills are graphic evidence of serious problems in a lake or stream. If the kill is related to the presence of toxic chemicals, there may be human health concerns, in addition to the obvious damage to the ecosystem and the fisheries resources. Depending on the cause of a fish kill, legal and economic ramifications may be involved. If the kill is cause by human or corporate actions, litigation is likely to follow, with possible court-awarded damages and assessed costs for cleanup and restoration. Federal and State agencies have expressed the need for a compendium of known and accepted methods and techniques that should be followed by anyone investigation a fish kill. This manual is an attempt to fill that need. It addresses the many facets involved in a fish kill investigation and provides instruction, guidance, examples, and sample forms that can be used. The U.S. Fish and Wildlife Service is pleased to provide this manual to help fisheries biologists and others prepare for a fish kill investigation. Research and Development (Region 8) has cooperated with the Division of Environmental Contaminants in Fish and Wildlife Enhancement to provide expertise and funds. We hope that the manual proves to be useful for interpreting evidence at the site of a fish kill, and corrective actions, and preparing for appearance as a court witness.

Resource Publication↗

USGS1982

Fish culture: an annotated bibliography of publications of the National Fisheries Center, Leetown, 1972-1980

This is an annotated bibliography of the publications authored or co-authored by the staff of the National Fisheries Center - Leetown (NFC-L) from 1972 through 1980. It includes publications from NFC-L staff at the Fish Farming Experimental Station, Stuttgart, AR; the Fish Genetics Laboratory, Beulah, WY; the Hagerman Field Station of the Tunison Laboratory of Fish Nutrition, Hagerman, ID; the National Fisheries Research and Development Laboratory, Marison, AL; and, the Tunison Laboratory of Fish Nutrition, Cortland, NY. It also includes publications from NFC-L staff at the Aquaculture Production/Demonstration Station, Fisheries Academy, Fish Genetics Station, National Fish Health Research Laboratory, and Technical Information Services, each located in Kearneysville, WV. Prior to 1977, each functioned as a separate entity within the U.S. Fish and Wildlife Service. In 1977, the administrative and program activities of these components were merged into the Natkonal Fisheries Center. This bibliography lists the publications issued by each of these entities both before and after becoming joined into the Center. Publications from these components prior to 1972 are documents in U.S. Bureau of Sport Fisheries and Wildlife, Resource Publication 120, Bibliography of Research Publications of the U.S. Bureau of Sport Fisheries and Wildlife, 1928-72 . Entries in this bibliography are arranged under broad subject categories, similar to those used in U.S. Fish and Wildlife Service, Sport Fishery Abstracts . Within these categories, the publications are then arranged alphabetically by author and sequentially by date of publication. They cover a wide range of scientific and technical disciplines applicable to the field of aquaculture. The annotations were submitted by each NFC-L component, and were modified to some extent for uniformity. An author index is included at the end of the bibliography.

Report↗

USGS2011

Overview on the effects of parasites on fish health

It is believed by many that parasites are only as important as the fish they infect. Parasites are ubiquitous, primarily surviving in a dynamic equilibrium with their host(s) and they are often overlooked in fish health assessments. Changes in the environment, both anthropogenic and environmental, can alter the parasite/host equilibrium and cause disease or mortality in fish. Therefore it is imperative that we have knowledge of both parasites and parasitic communities within a given population. When fish kills occur, it can often be associated with changes in parasite density and community composition. Often the damage associated with these fish is relative to the rate of infestation with the parasite; a fish that is lightly infected will show few signs of the parasite, while a heavily infected fish may become physiologically impaired and even die. Parasites can cause mechanical damage (fusion of gill lamellae, tissue replacement), physiological damage (cell proliferation, immunomodulation, detrimental behavioral responses, altered growth) and reproductive damage. As parasitism is the most common lifestyle on the planet, understanding its role in the environment may help researchers understand changes in a given fish population or stream ecosystem.

Conference Paper↗

USGS2014

Long Term Resource Monitoring Program procedures: fish monitoring

This manual constitutes the second revision of the U.S. Army Corps of Engineers’ Upper Mississippi River Restoration-Environmental Management Program (UMRR-EMP) Long Term Resource Monitoring Program (LTRMP) element Fish Procedures Manual. The original (1988) manual merged and expanded on ideas and recommendations related to Upper Mississippi River fish sampling presented in several early documents. The first revision to the manual was made in 1995 reflecting important protocol changes, such as the adoption of a stratified random sampling design. The 1995 procedures manual has been an important document through the years and has been cited in many reports and scientific manuscripts. The resulting data collected by the LTRMP fish component represent the largest dataset on fish within the Upper Mississippi River System (UMRS) with more than 44,000 collections of approximately 5.7 million fish. The goal of this revision of the procedures manual is to document changes in LTRMP fish sampling procedures since 1995. Refinements to sampling methods become necessary as monitoring programs mature. Possible refinements are identified through field experiences (e.g., sampling techniques and safety protocols), data analysis (e.g., planned and studied gear efficiencies and reallocations of effort), and technological advances (e.g., electronic data entry). Other changes may be required because of financial necessity (i.e., unplanned effort reductions). This version of the LTRMP fish monitoring manual describes the most current (2014) procedures of the LTRMP fish component.

Illinois;Iowa;Minnesota;Montana;Wisconsin↗

USGS2015

Assessment of general health of fishes collected at selected sites in the Great Lakes Basin In 2012

During the past decade, there has been a substantive increase in the detection of “emerging contaminants”, defined as a new substance, chemical, or metabolite in the environment; or a legacy substance with a newly expanded distribution, altered release, or a newly recognized effect (such as endocrine disruption). Emerging contaminants include substances such as biogenic hormones (human and animal), brominated flame retardants, pharmaceuticals, personal care products, plasticizers, current use pesticides, detergents, and nanoparticles. These contaminants are frequently not regulated or inadequately regulated by state or Federal water quality programs. Information about the toxicity of these substances to fish and wildlife resources is generally limited, compared to more highly regulated contaminants, and some classes have been shown to cause affects (for example feminization of male fish, immunomodulation) that are not evaluated via traditional toxicity testing protocols. As a result, these compounds may pose a substantial, but currently poorly documented threat to aquatic ecosystems. Failure to identify and understand the impacts of these emerging contaminants on fish and wildlife resources may result in deleterious impacts to Great Lakes resources that can result in adverse ecological, economic and recreational consequences. The U. S. Fish and Wildlife Service received funding through the Great Lakes Restoration Initiative (GLRI) for an Early Warning Program to detect and identify emerging contaminants and to evaluate the effects of these contaminants on fish and wildlife. The U.S. Geological Survey (WV Cooperative Fish and Wildlife Research Unit and National Fish Health Research Laboratory, Leetown Science Center) developed and implemented a biological effects monitoring protocol to assist in this program. Fish collections and measurements of biomarkers of exposure in Fall 2010 and Spring 2011 occurred at individual sites within select Areas of Concern (AOCs). They provided an assessment of the utility of the suite of biomarkers and also identified sites for more in-depth analyses. Selected areas are characterized as areas with known emerging contaminants, sensitive or listed species, areas downstream from municipal wastewater discharges or receiving waters for industrial facilities, and/or areas susceptible to agricultural or urban contamination, or harbors or ports. The results of the 2010- 2011 studies were summarized in Blazer et al. 2014 a, b, c; Braham et al. in review and Blazer et al. in review.

Great Lakes↗

USGS2014

The offshore benthic fish community

Lake Ontario’s offshore benthic fish community includes primarily slimy sculpin, lake whitefish, rainbow smelt, lake trout, burbot, and sea lamprey. Of these, lake trout have been the focus of an international restoration effort for more than three decades (Elrod et al. 1995; Lantry and Lantry 2008). The deepwater sculpin and three species of deepwater ciscoes (Coregonus spp.) that were historically important in the offshore benthic zone became rare or were extirpated by the 1960s (Christie 1973; Owens et al. 2003; Lantry et al. 2007b; Roth et al. 2013). Ecosystem changes continue to influence the offshore benthic fish community, including the effects of dreissenid mussels, the near disappearance of burrowing amphipods (Diporeia spp.) (Dermott et al. 2005; Watkins et al. 2007), and the increased abundance and expanded geographic distribution of round goby (see Nearshore Fish Community chapter) (Lantry et al. 2007b). The fish-community objectives for the offshore benthic fish community, as described by Stewart et al. (1999), are: The offshore benthic fish community will be composed of self-sustaining native fishes characterized by lake trout as the top predator, a population expansion of lake whitefish from northeastern waters to other areas of the lake, and rehabilitated native prey fishes.

New York↗

USGS2015

Status and trends of prey fish populations in Lake Michigan, 2014

The U.S. Geological Survey Great Lakes Science Center has conducted lake-wide surveys of the fish community in Lake Michigan each fall since 1973 using standard 12-m bottom trawls towed along contour at depths of 9 to 110 m at each of seven index transects. The resulting data on relative abundance, size and age structure, and condition of individual fishes are used to estimate various population parameters that are in turn used by state and tribal agencies in managing Lake Michigan fish stocks. All seven established index transects of the survey were completed in 2014. The survey provides relative abundance and biomass estimates between the 5-m and 114-m depth contours of the lake (herein, lake-wide) for prey fish populations, as well as burbot, yellow perch, and the introduced dreissenid mussels. Lake-wide biomass of alewives in 2014 was estimated at 1.6 kilotonnes (kt, 1 kt = 1000 metric tonnes), which was a record low and only 16% of the average biomass estimated since 2005. Moreover, the age distribution of alewives remained truncated with no alewife exceeding an age of 5. Record low biomass was also observed for nearly every other prey fish species: bloater (0.3 kt), rainbow smelt (0.02 kt), slimy sculpin (0.09 kt), deepwater sculpin (1.0 kt) and ninespine stickleback (0.004 kt). Round goby was the only prey fish species to avoid a record-low biomass estimate (2.04 kt); the 2014 estimate was 58% of the average lakewide biomass observed since 2006 when round gobies became relatively abundant in our catches. Burbot lake-wide biomass (0.5 kt in 2014) has remained below 3 kt since 2001. No age-0 yellow perch (i.e., < 100 mm) were captured during the survey, which is indicative of a poor year-class. Lake-wide biomass estimate of dreissenid mussels in 2014 was 23.9 kt, not different from 2013 (23.2 kt). Overall, the total lake-wide prey fish biomass estimate (sum of alewife, bloater, rainbow smelt, deepwater sculpin, slimy sculpin, round goby, and ninespine stickleback) in 2014 was only 5.1 kt, compared to the previous record-low prey fish biomass of 15.2 kt in 2012. In 2014, alewives and round gobies constituted 71% of this total, following a trend of dominance by these species since 2012.

Lake Michigan↗

USGS1960

Mycobacterium salmoniphilum sp. nov. from salmonoid fishes

The presence of mycobacteria in salmonoid fishes was first recorded by Earp, Ellis, and Ordal (1) in 1953. Acid-fast bacilli had previously been reported from other cold-blooded animals including fishes of fresh-water and marine origin; recent reviews have been presented by Vogel (2) and Parisot (3). The initiation of an intensive search for bacteria of this group revealed their widespread distribution in salmonoid fish populations. Acidfast bacilli have been demonstrated in livers and kidneys of salmon and trout in Washington, Oregon, and California, as well as from salmon taken in Alaskan waters. While the organisms are generally considered to be associated with fish of hatchery origin (4), they have also been found in young and adult fish from areas presumably supporting only wild populations. Wood and Ordal (4) indicate that the incidence of the tuberculosis-like infection is directly related to the length of time the fish are reared in the hatchery prior to release. This may result from a common hatchery practice of feeding viscera and carcasses from spawned-out adults to juvenile fish. Therefore, in many instances viable mycobacteria are present in the food of young fish.

American Review of Respiratory Disease↗