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At least 19 recordsLinked to original sources

Coelomic disorders of fishes

Dropsy is a commonly applied term for coelomic distention due to ascites, or the effusion and collection of fluid freely throughout the coelomic cavity. Dropsy, or ascites, is generally a sign of another ongoing disease process, oftentimes one that is multisystemic and impacting coelomic organs and tissues. Dropsy may be caused by a variety of potential etiological agents, both infectious and noninfectious. Stressors such as rapid change in water temperature may predispose fish to bacterial diseases associated with dropsy. Clinically affected fish display coelomic distension of varying degrees of severity. Generally considered a disease syndrome similar to dropsy, affecting specifically Malawi cichlids, a popular group of ornamental fish among aquarium hobbyists. Water belly occurs among salt water pen-reared salmonid fish, including Atlantic salmon, Chinook salmon and rainbow trout. Dietary changes such as reduction of the feeding rate have been reported to improve the condition among affected fish.

Book chapter

Ammonia and aquatic ecosystems – A review of global sources, biogeochemical cycling, and effects on fish

The purpose of this review is to better understand the full life cycle and influence of ammonia from an aquatic biology perspective. While ammonia has toxic properties in water and air, it also plays a central role in the biogeochemical nitrogen (N) cycle and regulates mechanisms of normal and abnormal fish physiology. Additionally, as the second most synthesized chemical on Earth, ammonia contributes economic value to many sectors, particularly fertilizers, energy storage, explosives, refrigerants, and plastics. But, with so many uses, industrial N 2 -fixation effectively doubles natural reactive N concentrations in the environment. The consequence is global, with excess fixed nitrogen driving degradation of soils, water, and air; intensifying eutrophication, biodiversity loss, and climate change; and creating health risks for humans, wildlife, and fisheries. Thus, the need for ammonia research in aquatic systems is growing. In response, we prepared this review to better understand the complexities and connectedness of environmental ammonia. Even the term “ammonia” has multiple meanings. So, we have clarified the nomenclature, identified units of measurement, and summarized methods to measure ammonia in water. We then discuss ammonia in the context of the N-cycle, review its role in fish physiology and mechanisms of toxicity, and integrate the effects of human N-fixation, which continuously expands ammonia's sources and uses. Ammonia is being developed as a carbon-free energy carrier with potential to increase reactive nitrogen in the environment. With this in mind, we review the global impacts of excess reactive nitrogen and consider the current monitoring and regulatory frameworks for ammonia. The presented synthesis illustrates the complex and interactive dynamics of ammonia as a plant nutrient, energy molecule, feedstock, waste product, contaminant, N-cycle participant, regulator of animal physiology, toxicant, and agent of environmental change. Few molecules are as influential as ammonia in the management and resilience of Earth's resources.

Science of the Total Environment

Sex effect on polychlorinated biphenyl concentrations in fish: a synthesis

Polychlorinated biphenyls (PCBs) accumulate in fish primarily via food intake, and therefore, PCBs serve as a chemical tracer for food consumption. Sex differences in PCB concentrations of fish have been attributed to the following three mechanisms: (i) females losing a substantial portion of their PCB body burden during spawning and consequently their PCB concentration is considerably reduced immediately after spawning; (ii) sex differences in habitat utilization leading to sex differences in the PCB concentrations of the prey; and (iii) sex differences in gross growth efficiency, which is defined as growth divided by the amount of food consumption needed to achieve that growth. Based on my analyses and synthesis, mechanisms (i) and (ii) operate in relatively few fish populations, but can lead to mature males having PCB concentrations two to three times higher than mature female PCB concentrations. In contrast, mechanism (iii) operates in all fish populations, but typically, mechanism (iii) results in relatively modest sex differences, with mature males only between 15 and 35% higher in PCB concentration than mature females. In summary, the study of sex differences in PCB concentrations of fish has led to insights into fish behaviour and fish physiology.

Fish and Fisheries

Climate change effects on North American fish and fisheries to inform adaptation strategies

Climate change is a global persistent threat to fish and fish habitats throughout North America. Climate-induced modification of environmental regimes, including changes in streamflow, water temperature, salinity, storm surges, and habitat connectivity can change fish physiology, disrupt spawning cues, cause fish extinctions and invasions, and alter fish community structure. Reducing greenhouse emissions remains the primary mechanism to slow the pace of climate change, but local and regional management agencies and stakeholders have developed an arsenal of adaptation strategies to help partially mitigate the effects of climate change on fish. We summarize common stressors posed by climate change in North America, including (1) increased water temperature, (2) changes in precipitation, (3) sea level rise, and (4) ocean acidification, and present potential adaptation strategies that fishery professionals may apply to help vulnerable fish and fisheries cope with a changing climate. Although our adaptation strategies are primarily from North America, they have broader geographic applicability to fish and aquatic biota in other jurisdictions. These strategies provide opportunities for managers to mitigate the effects of climate change on fish and fish habitat while needed global policies to reduce greenhouse gas emissions emerge, which may offer more lasting solutions.

Fisheries Magazine

Molecular responses differ between sensitive silver carp and tolerant bighead carp and bigmouth buffalo exposed to rotenone

Some species of fish are more tolerant of rotenone, a commonly used non-specific piscicide, than others. This species-specific tolerance to rotenone has been thought to be associated with the uptake and the efficiency at which the chemical is detoxified. However, rotenone stimulates oxidative stress and superoxides, which are also toxic. Understanding the modes in which fish physiologically respond to rotenone is important in developing improved protocols for its application in controlling aquatic nuisance species. Using a molecular approach, we investigated the physiological and molecular mechanisms of rotenone resistance. Species-specific responses were observed when rotenone-sensitive silver, Hypophthalmichthys molitrix, and both rotenone-resistant bighead carp, Hypophthalmichthys nobilis, and bigmouth buffalo, Ictiobus cyprinellus, were exposed to rotenone. Rotenone levels in plasma were highest 90 min after exposure in both silver carp and bigmouth buffalo, but bigmouth buffalo tolerated over twice the burden (ng mL -1 g -1 ) than silver carp. Expression of genes related with detoxification ( cyp1a and gst ) increased in silver carp, but either decreased or remained the same in bighead carp. Genes linked with oxidative stress in the cytosol ( gpx , cat and sod1 ) and hsp70 increased only in silver carp after a 6-h exposure. Expression of genes associated with oxidative stress in the mitochondria ( sod2 and ucp2 ) differed between silver carp and bighead carp. Expression of sod2 changed minimally in bighead carp, but expression of ucp2 linearly increased to nearly 85-fold of the level prior to exposure. Expression of sod2 and ucp2 did not change until 6 h in silver carp. Use of sod1 and sod2 to combat oxidative stress results in hydrogen peroxide production, while use of ucp2 produces nitric oxide, a chemical known to inhibit apoptosis. We conclude that the mechanism at which a fish handles oxidative stress plays an important role in the tolerance to rotenone.

Fish Physiology and Biochemistry

The concept of stress in fish

The general physiological response of fish to threatening situations, as with all vertebrates, is referred to as stress . A stress response is initiated almost immediately following the perception of a stressor. Mildly stressful situations can have beneficial or positive effects (eustress), while higher severities induce adaptive responses but also can have maladaptive or negative consequences (distress). The stress response is initiated and controlled by two hormonal systems , those leading to the production of corticosteroids (mainly cortisol) and catecholamines (such as adrenaline and noradrenaline and their precursor dopamine). Together these regulate the secondary stress response factors that alter the distribution of necessary resources such as energy sources and oxygen to vital areas of the body, as well as compromise hydromineral imbalance and the immune system. If fish can resist death due to a stressor, they recover to a similar or somewhat similar homeostatic norm. Long-term consequences of repeated or prolonged exposures to stress are maladaptive by negatively affecting other necessary life functions (growth, development, disease resistance, behavior, and reproduction), in large part because of the energetic cost associated with mounting the stress response (allostatic load). There is considerable variation in how fish respond to a stressor because of genetic differences among different taxa and also within stocks and species. Variations within the stress response are introduced by the environmental history of the fish, present ambient environmental conditions, and the fish's present physiological condition. Currently, fish physiology has progressed to the point where we can easily recognize when fish are stressed, but we cannot always recognize when fish are unstressed because the lack of clinical signs of stress does not always correspond to fish being unstressed. In other words, we need to be aware of the possibility of false negatives regarding clinical signs of stress. In addition, we cannot use clinical data to precisely or accurately infer severity of a stressor.

Fish Physiology

Electrofishing mark-recapture and depletion methodologies evoke behavioral and physiological changes in cutthroat trout

We examined the behavioral and physiological responses of wild and hatchery-reared cutthroat trout Oncorhynchus clarki subjected to a single electroshock, electroshock plus marking, and multiple electroshocks in natural and artificial streams. In a natural stream, cutthroat trout released after capture by electrofishing and marking showed distinct behavioral changes: fish immediately sought cover, remained relatively inactive, did not feed, and were easily approached by a diver. An average of 3–4 h was required for 50% of the fish to return to a seemingly normal mode of behavior, although responses varied widely among collection sites. Using the depletion method, we observed little change in normal behavior offish remaining in the stream section (i.e., uncaptured fish) after successive passes with electrofishing gear. In an artificial stream, hatchery-reared and wild cutthroat trout immediately decreased their rates of feeding and aggression after they were electroshocked and marked. Hatchery fish generally recovered in 2–3 h; wild fish required at least 24 h to recover. Analysis of feeding and aggression data by hierarchical rank revealed no distinct recovery trends among hatchery fish of different ranks; among wild cutthroat trout, however, socially dominant fish seemed to recover faster than intermediate and subordinate fish. Physiological indicators of stress (plasma cortisol and blood lactic acid) increased significantly in cutthroat trout subjected to electroshock plus marking or single or multiple electroshocks. As judged by the magnitude of the greatest change in cortisol and lactate, multiple electroshocks elicited the most severe stress response; however, plasma concentrations of both substances had returned to unstressed control levels by 6 h after treatment. It was evident that electrofishing and the procedures involved with estimating fish population size elicited a general stress response that was manifested not only physiologically but also behaviorally. These responses may affect the accuracy of population size estimates by violating key assumptions of the methods, especially the assumption of equal catchability offish.

Transactions of the American Fisheries Society

The effects of electroshock on immune function and disease progression in juvenile spring chinook salmon

Although much is known about the effects of electroshock on fish physiology, consequences to the immune system and disease progression have not received attention. Our objectives were to determine the effects of electroshock on selected immune function in juvenile spring chinook salmon Oncorhynchus tshawytscha, the mechanism of any observed alteration, and the effects of electroshock on disease progression. We found that the ability of anterior kidney leukocytes to generate antibody-producing cells (APC) was suppressed 3 h after a pulsed-DC electroshock (300 V, 50 Hz, 8 ms pulse width) but recovered within 24 h. This response was similar in timing and magnitude to that of fish subjected to an acute handling stress. The mechanism of suppression is hypothesized to be via an elevation of plasma cortisol concentrations in response to stress. Other monitored immune functions, skin mucous lysozyme levels, and respiratory burst activity were not affected by exposure to electroshock. The progression of a Renibacterium salmoninarum (RS) infection may have been altered after exposure to an electroshock. The electroshock did not affect infection severity or the number of mortalities, but may have accelerated the time to death. The limited duration of APC suppression and lack of effects on lysozyme and respiratory burst, as well as infection severity and mortality levels in RS-infected fish, led us to conclude that electrofishing under the conditions we tested is a safe procedure in regards to immunity and disease.

Transactions of the American Fisheries Society

Comparison of hydraulics and particle removal efficiencies in a mixed cell raceway and Burrows pond rearing system

We compared the hydrodynamics of replicate experimental mixed cell and replicate standard Burrows pond rearing systems at the Dworshak National Fish Hatchery, ID, in an effort to identify methods for improved solids removal. We measured and compared the hydraulic residence time, particle removal efficiency, and measures of velocity using several tools. Computational fluid dynamics was used first to characterize hydraulics in the proposed retrofit that included removal of the traditional Burrows pond dividing wall and establishment of four counter rotating cells with appropriate drains and inlet water jets. Hydraulic residence time was subsequently established in the four full scale test tanks using measures of conductivity of a salt tracer introduced into the systems both with and without fish present. Vertical and horizontal velocities were also measured with acoustic Doppler velocimetry in transects across each of the rearing systems. Finally, we introduced ABS sinking beads that simulated fish solids then followed the kinetics of their removal via the drains to establish relative purge rates. The mixed cell raceway provided higher mean velocities and a more uniform velocity distribution than did the Burrows pond. Vectors revealed well-defined, counter-rotating cells in the mixed cell raceway, and were likely contributing factors in achieving a relatively high particle removal efficiency-88.6% versus 8.0% during the test period. We speculate retrofits of rearing ponds to mixed cell systems will improve both the rearing environments for the fish and solids removal, improving the efficiency and bio-security of fish culture. We recommend further testing in hatchery production trials to evaluate fish physiology and growth.

Idaho

Drivers and uncertainties of forecasted range shifts for warm-water fishes under climate and land cover change

Land cover is an important determinant of aquatic habitat and is projected to shift with climate changes, yet climate-driven land cover changes are rarely factored into climate assessments. To quantify impacts and uncertainty of coupled climate and land cover change on warm-water fish species’ distributions, we used an ensemble model approach to project distributions of 14 species. For each species, current range projections were compared to 27 scenario-based projections and aggregated to visualize uncertainty. Multiple regression and model selection techniques were used to identify drivers of range change. Novel, or no-analogue, climates were assessed to evaluate transferability of models. Changes in total probability of occurrence ranged widely across species, from a 63% increase to a 65% decrease. Distributional gains and losses were largely driven by temperature and flow variables and underscore the importance of habitat heterogeneity and connectivity to facilitate adaptation to changing conditions. Finally, novel climate conditions were driven by mean annual maximum temperature, which stresses the importance of understanding the role of temperature on fish physiology and the role of temperature-mitigating management practices.

Canadian Journal of Fisheries and Aquatic Sciences

Evaluating acid-aluminum stress in streams of the Northeastern U.S. at watershed, fish community and physiological scales

In spite of overall improvements in air and water quality, biological stress from low pH and high concentrations of inorganic aluminum continue to impact fish and fish habitat in northeastern North America, with independent and interactive effects on individuals, populations and communities. Integrative indicators can therefore be useful in monitoring both impact and recovery across multiple scales. Using coupled water chemistry (pH, conductivity, and base cation and inorganic aluminum concentration), geographic (site elevation and watershed area) and biological (fish diversity, fish abundance, gill aluminum concentration and gill physiology) data, we developed an integrated indicator of acid aluminum stress across the White and Green mountains in central New England, USA. As has been established in a number of previous studies, preliminary analysis clearly indicated that across all sites, inorganic aluminum concentration was consistently greatest during the spring season. Structural Equation modelling (SEM) revealed that toxic conditions (concurrent low pH and high concentrations of inorganic aluminum) were well summarized with an integrated toxicity score, related to both base cation concentrations and elevation, with sites at higher elevations more likely to experience toxic conditions as well as low base cation concentrations. As hypothesized, fish diversity and abundance were negatively related to toxicity score. In spite of considerable variation among individuals, gill aluminum was positively related to toxicity score for both Atlantic salmon and brook trout. Observed elevated gill aluminum levels associated with reduced gill metabolic activity in Atlantic salmon smolts from impacted systems likely result in impaired osmoregulatory function and seawater tolerance. Overall, our results suggest that the integrated toxicity score metric is strongly associated with a syndrome of physiological stress, reduced abundance, and low species diversity for stream fishes in New England and can likely serve as a reliable indicator of continued impairment or recovery of acid-aluminum vulnerable systems in this ecoregion.

New Hampshire, Vermont

Fish gut microbiota analysis differentiates physiology and behavior of invasive Asian carp and indigenous American fish

Gut microbiota of invasive Asian silver carp (SVCP) and indigenous planktivorous gizzard shad (GZSD) in Mississippi river basin were compared using 16S rRNA gene pyrosequencing. Analysis of more than 440 000 quality-filtered sequences obtained from the foregut and hindgut of GZSD and SVCP revealed high microbial diversity in these samples. GZSD hindgut (GZSD_H) samples (n=23) with >7000 operational taxonomy units (OTUs) exhibited the highest alpha-diversity indices followed by SVCP foregut (n=15), GZSD foregut (n=9) and SVCP hindgut (SVCP_H) (n=24). UniFrac distance-based non-metric multidimensional scaling (NMDS) analysis showed that the microbiota of GZSD_H and SVCP_H were clearly separated into two clusters: samples in the GZSD cluster were observed to vary by sampling location and samples in the SVCP cluster by sampling date. NMDS further revealed distinct microbial community between foregut to hindgut for individual GZSD and SVCP. Cyanobacteria, Proteobacteria, Actinobacteria and Bacteroidetes were detected as the predominant phyla regardless of fish or gut type. The high abundance of Cyanobacteria observed was possibly supported by their role as the fish’s major food source. Furthermore, unique and shared OTUs and OTUs in each gut type were identified, three OTUs from the order Bacteroidales, the genus Bacillariophyta and the genus Clostridium were found significantly more abundant in GZSD_H (14.9–22.8%) than in SVCP_H (0.13–4.1%) samples. These differences were presumably caused by the differences in the type of food sources including bacteria ingested, the gut morphology and digestion, and the physiological behavior between GZSD and SVCP.

International Society for Microbial Ecology

Warmer temperatures interact with salinity to weaken physiological facilitation to stress in freshwater fishes

Management of stressors requires an understanding of how multiple stressors interact, how different species respond to those interactions and the underlying mechanisms driving observed patterns in species' responses. Salinization and rising temperatures are two pertinent stressors predicted to intensify in freshwater ecosystems, posing concern for how susceptible organisms achieve and maintain homeostasis (i.e. allostasis). Here, glucocorticoid hormones (e.g. cortisol), responsible for mobilizing energy (e.g. glucose) to relevant physiological processes for the duration of stressors, are liable to vary in response to the duration and severity of salinization and temperature rises. With field and laboratory studies, we evaluated how both salinity and temperature influence basal and stress-reactive cortisol and glucose levels in age 1+ mottled sculpin ( Cottus bairdii ), mountain sucker ( Catostomus platyrhynchus ) and Colorado River cutthroat trout ( Oncorhynchus clarki pleuriticus ). We found that temperature generally had the greatest effect on cortisol and glucose concentrations and the effect of salinity was often temperature dependent. We also found that when individuals were chronically exposed to higher salinities, baseline concentrations of cortisol and glucose usually declined as salinity increased. Reductions in baseline concentrations facilitated stronger stress reactivity for cortisol and glucose when exposed to additional stressors, which weakened as temperatures increased. Controlled temperatures near the species' thermal maxima became the overriding factor regulating fish physiology, resulting in inhibitory responses. With projected increases in freshwater salinization and temperatures, efforts to reduce the negative effects of increasing temperatures (i.e. increased refuge habitats and riparian cover) could moderate the inhibitory effects of temperature-dependent effects of salinization for freshwater fishes.

Wyoming

Effects of dissolved carbon dioxide on the physiology and behavior of fish artificial streams

A new technology for treating waters contaminated with acid mine drainage involves the dissolution of limestone particles using carbon dioxide at pressures above ambient. Because of the fish health risks associated with episodes of high carbon dioxide levels in treated waters, we subjected three species of fish, brook trout ( Salvelinus fontinalis ), slimy sculpin ( Cottus cognatus ), and blacknose dace ( Rhinichthys atratulus ), to 24 h exposures of elevated dissolved carbon dioxide (CO 2 ) at three levels, ranging from 1.0 (low) to 6.3 (high)%, under laboratory conditions. We measured blood physiological variables as well as behavior, including feeding responses, before, during, and after exposure. Physiological responses differed by species, but all species had elevated hematocrits after 1 h of exposure. Brook trout hematocrits were higher at medium and high levels of CO 2 than in a control group (0.0% CO 2 ) after 24 h of exposure. Slimy sculpin hematocrits were higher in medium- and high-level exposure groups than in controls after 1 h, but not after 24 h, of exposure. Blacknose dace hematocrits were higher in all three exposure groups than in controls after 1 h but only in medium-level exposure groups after 24 h. Brook trout plasma glucose was significantly higher in medium- and high-level exposure groups after 1 h, and in the high-level group after 24 h, than in controls. Slimy sculpin plasma glucose was not significantly different in elevated CO 2 exposure groups from that of controls throughout exposure. Branchial ventilation was significantly greater in all species at elevated CO 2 during exposure, indicating stress; however, no difference was observed between treatment and control groups of blacknose dace after 24 h, indicating acclimation. Pectoral fin beats and cough rates were not consistently related to CO 2 exposure throughout the study. Brook trout had the longest lasting reaction to stress at lower levels of CO 2 among the three species tested. Many of the 11 observed behavioral variables, related to swimming, feeding, social, and illness factors, were affected by elevations of dissolved CO 2 . Two to seven behavioral variables (18–64% of those measured) were affected by treatment level of dissolved CO 2 with a trend by species for the number of variables affected: brook trout>blacknose dace>slimy sculpin. However, behavioral sensitivity to treatment level was greatest in blacknose dace. Recovery to pre-treatment activity rates for most behavior patterns (including feeding) was observed 24 h after cessation of exposure in all three species. Recovery was independent of treatment level, was most rapid in blacknose dace, and was slowest in brook trout. Overall, slimy sculpin was least affected behaviorally by elevated CO 2 . Although all three species showed stress response and changes in behavior at moderate levels of CO 2 (≥2%), brook trout and blacknose dace showed evidence of ability to avoid harmful CO 2 levels by swimming out of affected waters, whereas the slimy sculpin showed minimal behavioral changes despite remaining in place during exposure. Thus, predation risk and other sources of mortality seem minimal in the event of technological malfunction at a stream treatment site involving the use of CO 2 under pressure.

Environmental Toxicology

Use of automated monitoring to assess behavioral toxicology in fish: Linking behavior and physiology

We measured locomotory behaviors (distance traveled, speed, tortuosity of path, and rate of change in direction) with computer-assisted analysis in 30 day posthatch rainbow trout (Oncorhynchus mykiss) exposed to pesticides. We also examined cholinesterase inhibition as a potential endpoint linking physiology and behavior. Sublethal exposure to chemicals often causes changes in swimming behavior, reflecting alterations in sensory and motor systems. Swimming behavior also integrates functions of the nervous system. Rarely are the connections between physiology and behavior made. Although behavior is often suggested as a sensitive, early indicator of toxicity, behavioral toxicology has not been used to its full potential because conventional methods of behavioral assessment have relied on manual techniques, which are often time-consuming and difficult to quantify. This has severely limited the application and utility of behavioral procedures. Swimming behavior is particularly amenable to computerized assessment and automated monitoring. Locomotory responses are sensitive to toxicants and can be easily measured. We briefly discuss the use of behavior in toxicology and automated techniques used in behavioral toxicology. We also describe the system we used to determine locomotory behaviors of fish, and present data demonstrating the system's effectiveness in measuring alterations in response to chemical challenges. Lastly, we correlate behavioral and physiological endpoints.

Conference Paper

A comparison of mercury burdens between St. Marks National Wildlife Refuge and St. Andrew Bay, Florida: Evaluation of fish body burdens and physiological responses in largemouth bass, spotted seatrout, striped mullet, and sunfish

Musculature from the dorsal region of 130 largemouth bass (Micropterus salmoides), 140 sunfish (Lepomis sp.), 41 spotted seatrout (Cynoscion nebulosus) and 67 striped mullet (Mugil cephalus) were collected from five estuarine and five freshwater sites within the St. Marks National Wildlife Refuge and two estuarine and two freshwater sites from St. Andrew Bay, Florida, United States of America. Musculature was analyzed for total mercury content, sagittal otoliths were removed for age determination and physiological responses were measured. Largemouth bass and sunfish from the refuge had higher mercury concentrations in musculature than those from the bay. Male spotted seatrout, male striped mullet, male and female sunfish and female largemouth bass had mercury burdens positively correlated with length. The majority of all four species of fish from both study areas contained mercury levels below 1.5 part per million, the limit for safe consumption recommended the Florida Department of Health. In comparison, a significant percentage of largemouth bass and sunfish from several sampled sites, most notably Otter Lake and Lake Renfroe within St. Marks National Wildlife Refuge, had mercury levels consistent with the health department's guidelines of 'limited consumption' or 'no consumption guidelines.'

Open-File Report