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USGS1989

Assessment of smolt condition for travel time analysis. Annual report 1988

Estimates of migration rates and travel times of juvenile salmonids within index reaches of the Columbia River basin are collected through the Smolt Monitoring Program for use by the Fish Passage Center. With increased reliance upon travel time estimates in 1988 by the Fish Passage Center, this study was implemented to monitor the biological attributes of juvenile chinook salmon Oncorhynchus tshawytscha and steelhead trout 0.- mykiss used for the travel time estimates, The physiological ability of fish to respond to stress was assessed by measuring levels of plasma cortisol, glucose, and chloride before and after a stress-challenge test. Most mid-Columbia and Snake river groups responded normally to the stress challenge exhibiting an increase in plasma glucose and cortisol and a slight decrease in chloride. Fish trucked to release sites were more stressed than those released directly from the hatchery, but most still responded to the stress challenge test normally. An abnormal or extreme stress response occurred when there were deviations from preferred protocol, disease problems at hatcheries, or when fish were trucked over long periods (7h). The development of smoltification was evaluated by measuring gill Na+K+-ATPase, plasma thyroxine, purines, and body morphology. Most groups were similar at the hatcheries but differed as the migration to McNary Dam proceeded. Gill ATPase activity increased 2-3 fold during the first 20 days of migration, after which it changed little. Fish with longer in-river travel times appeared to be more smolted than those which were in the river for a shorter period of time. The prevalence of bacterial kidney disease (BKD) in spring chinook salmon was evaluated using the enzyme linked immunosorbent assay (ELISA) and fluorescent antibody technique (FAT). Prevalence of BKD in groups tested using the ELISA method was as high as 99% at some downstream locations. A review of indices is presented as a guide, to the development of an index of smolt condition and preliminary data are presented. An index could be used as a tool to synthesize information on fish condition to assist with management and evaluation of the Water Budget.

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↗

USGS2024

River herring influence perch morphology, physiology, and life history

Anadromous fishes play important roles in nutrient dynamics for freshwater ecosystems; however, the trophic pathways have been less documented for iteroparous species like river herring ( Alosa pseudoharengus and A. aestivalis ) compared to semelparous species like Pacific salmon ( Oncorhynchus spp.). Given recent increases in restoration activities to improve connectivity, an understanding of how anadromous river herring influence the morphology, physiology, and life history of predatory fishes can help predict restoration responses. We aimed to quantify the trophic influence of juvenile anadromous river herring on predatory white perch ( Morone americana ) and yellow perch ( Perca flavescens ) using a combination of stable isotopes, growth rates, and condition indices. We sampled six lakes in coastal Massachusetts—three lakes with anadromous river herring and three similar lakes without river herring. Bayesian mixing models of δ 13 C and δ 15 N indicated white perch consumed juvenile river herring in higher proportions (69–75%) compared to co-occurring prey fishes (11–16%). Lakes with juvenile river herring contained perch with significantly higher condition values, higher immature growth rates (age 1 and 2), lower mature growth rates (> age 3), significantly smaller mature lengths, and lower mortality rates compared to perch in lakes without river herring. These divergent life history traits of perch in response to consumption of juvenile river herring are consistent with observations in other predatory fishes. Direct links between river herring and predator condition, growth, and life history trajectories suggest broad influences on ecosystem structure across trophic levels through physiological, morphometric, and life history modifications.

Massachusetts↗

USGS2004

Oxidative stress in juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum)

Juvenile chinook salmon, Oncorhynchus tshawytscha (Walbaum), were held in 8-11??C freshwater, starved for 3 days and subjected to a low-water stressor to determine the relationship between the general stress response and oxidative stress. Lipid peroxidation (LPO) levels (lipid hydroperoxides) were measured in kidney, liver and brain samples taken at the beginning of the experiment (0-h unstressed controls) and at 6, 24 and 48 h after application of a continuous low-water stressor. Tissue samples were also taken at 48 h from fish that had not been exposed to the stressor (48-h unstressed controls). Exposure to the low-water stressor affected LPO in kidney and brain tissues. In kidney, LPO decreased 6 h after imposition of the stressor; similar but less pronounced decreases also occurred in the liver and brain. At 48 h, LPO increased (in comparison with 6-h stressed tissues) in the kidney and brain. In comparison with 48-h unstressed controls, LPO levels were higher in the kidney and brain of stressed fish. Although preliminary, results suggest that stress can cause oxidative tissue damage in juvenile chinook salmon. Measures of oxidative stress have shown similar responses to stress in mammals; however, further research is needed to determine the extent of the stress-oxidative stress relationship and the underlying physiological mechanisms in fish.

Aquaculture Research↗

USGS1988

Preliminary results of the Department of the Interior's irrigation drainage studies

The Department of the Interior, in 1986, began irrigation drainage studies in nine areas in seven Western states to determine whether irrigation drainage has caused or has the potential to cause harmful effects on human health, fish, and wildlife, or might reduce the suitability of water for beneficial uses. Results of the seven studies completed in 1987 are presented and are compared to baselines, standards, criteria, and other guidelines helpful for assessing the potential of observed constituent concentrations in water, bottom sediment, and biota to result in physiological harm to fish, wildlife, or humans. Selenium is the constituent most commonly found at elevated concentrations in water, bottom sediment, and biota in the study areas. Additional study results are discussed.

Conference Paper↗

USGS2022

Thermal performance of the electron transport system Complex III in seven Alabama fishes

Management of fish populations for conservation in thermally variable systems requires an understanding of the fish's underlying physiology and responses to thermal stress. Physiological research at the organismal level provides information on the overall effects of stressors such as extreme temperature fluctuations. While experiments with whole organisms provide information as to the overall effects of temperature fluctuations, biochemical assays of thermal stress provide direct results of exposure that are both sensitive and specific. Electron transport system (ETS; Complex III) assays quantify a rate-limiting step of respiratory enzymes. Parameters that can be estimated via this approach include optimum thermal temperature ( T opt ) and optimal breadth of thermal performance ( T breadth ), which can both be related to organismal-level temperature thresholds. We exposed enzymes of seven fish species (native fish chosen to represent a typical community in Alabama streams) to temperatures in the range 11–44°C. The resultant enzymatic thermal performance curves showed that T opt , the lower temperature for enzyme optimal thermal performance ( T low ), the upper temperature for enzyme optimal thermal performance ( T up ), and T breadth differed among species. Relationships between enzymatic activity and temperature for all fish followed a pattern of steadily increasing enzyme activity to T opt before gradually decreasing with increasing temperature. A comparison of our enzyme optimum and upper-temperature limit results versus published critical thermal maxima values supports that ETS Complex III assays may be useful for assessing organismal-level thermal tolerance.

JEZ-A: Ecological and Integrative Physiology↗

USGS2008

Physiological response of some economically important freshwater salmonids to catch-and-release fishing

Catch-and-release fishing regulations are widely used by fishery resource managers to maintain both the quantity and quality of sport fish populations. We evaluated blood chemistry disturbances in wild brook trout Salvelinus fontinalis, brown trout Salmo trutta, cutthroat trout Oncorhynchus clarkii, and Arctic grayling Thymallus arcticus that had been hooked and played for 1-5 min in waters of the intermountain western United States. A hatchery stock of brown trout was included for comparison. To assess time needed for recovery, additional test groups were played for 5 min and then released into net-pens, where they were held for up to 72 h. The osmoregulatory and metabolic disturbances associated with catch-and-release fishing under the conditions we tested were minimal and judged to be well within normal physiological tolerance limits. In fish that were held for recovery, the blood chemistry alterations that did occur appeared to be related to stress from confinement in the net-pens. Our results confirm the results of previous studies, showing that prerelease air exposure and handling cause more physiological stress than does either hooking per se or playing time. Fishery managers must be aware of the differences in the perceptions, attitudes, and values of different societal groups, some of which feel that catch-and-release fishing should be banned because it is cruel to the animals. On the basis of brain anatomy, it seems highly unlikely that fish experience pain in the same manner as humans experience it, because fish lack a neocortex, the brain structure that enables the sensation of pain in higher vertebrates. However, independent of the neurobiological argument, our results indicate that under conditions similar to those tested, fish subjected to catch and release are neither suffering nor particularly stressed. Improved education programs about the relatively benign physiological effects of catch-and-release fishing as a fishery management practice would be beneficial to anglers and the nonfishing public alike.

North American Journal of Fisheries Management↗

USGS2009

The effects of aquaculture production noise on the growth, condition factor, feed conversion, and survival of rainbow trout, Oncorhynchus mykiss

Intensive aquaculture systems, particularly recirculating systems, utilize equipment such as aerators, air and water pumps, blowers, and filtration systems that inadvertently increase noise levels in fish culture tanks. Sound levels and frequencies measured within intensive aquaculture systems are within the range of fish hearing, but species-specific effects of aquaculture production noise are not well defined. Field and laboratory studies have shown that fish behavior and physiology can be negatively impacted by intense sound. Therefore, chronic exposure to aquaculture production noise could cause increased stress, reduced growth rates and feed conversion efficiency, and decreased survival. The objective of this study was to provide an in-depth evaluation of the long term effects of aquaculture production noise on the growth, condition factor, feed conversion efficiency, and survival of cultured rainbow trout, Oncorhynchus mykiss. Rainbow trout were cultured in replicated tanks using two sound treatments: 117??dB re 1????Pa RMS which represented sound levels lower than those recorded in an intensive recycle system and 149??dB re 1????Pa RMS, representing sound levels near the upper limits known to occur in recycle systems. To begin the study mean fish weights in the 117 and 149??dB tanks were 40 and 39??g, respectively. After five months of exposure no significant differences were identified between treatments for mean weight, length, specific growth rates, condition factor, feed conversion, or survival (n = 4). Mean final weights for the 117 and 149??dB treatments were 641 ?? 3 and 631 ?? 10??g, respectively. Overall specific growth rates were equal, i.e. 1.84 ?? 0.00 and 1.84 ?? 0.01%/day. Analysis of growth rates of individually tagged rainbow trout indicated that fish from the 149??dB tanks grew slower during the first month of noise exposure (p < 0.05); however, fish acclimated to the noise thereafter. This study further suggests that rainbow trout growth and survival are unlikely to be affected over the long term by noise levels common to intensive aquaculture systems. ?? 2008 Elsevier B.V.

Aquaculture↗

USGS2020

Effects of temperature on hatching rate and early development of alligator gar and spotted gar in a laboratory setting

Water temperature influences both morphological and physiological development in fishes. However, the effects of water temperature on the early development of Alligator Gar Atractosteus spatula and Spotted Gar Lepisosteus oculatus are not well understood. Both gar species were collected from natural environments and spawned in a hatchery setting. After spawning, fertilized embryos were collected and transferred to the Oklahoma Fishery Research Laboratory, where the embryos (50–72 embryos/treatment) were placed into one of five water temperature treatments (15.5, 20.0, 23.8, 27.5, and 32.2°C) and observed over time to estimate the time to hatch and the time to reach the free-swimming stage. Both species showed an inverse relationship between temperature and the timing of hatch and advancement to free-swimming fingerlings for all treatments. In addition, Alligator Gar embryos did not develop at the coldest water temperature tested, and Alligator Gar juveniles held at the warmest temperature tested were observed with developmental abnormalities, potentially affecting their survival. The same temperature extremes had no comparable negative effect on Spotted Gar. The results of this study are useful for understanding early life history dynamics of these two species in their natural environments and can also be used by hatchery managers who are seeking to optimize their production protocols.

North American Journal of Fisheries Management↗

USGS1989

Irrigation-induced contamination--How real a problem

The U.S. Department of the Interior has embarked on a series of reconnaissance‐level investigations throughout the western states to identify, evaluate, and respond to irrigation‐induced water quality problems. A series of water, sediment, and biological samples are being analyzed for 17 inorganic constituents and a number of pesticides. 19 studies in 13 states have been undertaken. Seven have been completed to date. Results of the seven studies that have been completed are presented and compared to baselines, standards, criteria, and other guidelines helpful for assessing the potential of observed constituent concentrations in water, bottom sediment, and biota, to result in physiological harm to fish, wildlife, or humans. These initial results indicate that a new environmental problem of major proportions does not exist, but that some localized problems of significant magnitude do exist and should be addressed.

Journal on Irrigation Drainage Engineering↗

USGS2013

Limitation and facilitation of one of the world's most invasive fish: an intercontinental comparison

Purposeful species introductions offer opportunities to inform our understanding of both invasion success and conservation hurdles. We evaluated factors determining the energetic limitations of brown trout (Salmo trutta) in both their native and introduced ranges. Our focus was on brown trout because they are nearly globally distributed, considered one of the world's worst invaders, yet imperiled in much of their native habitat. We synthesized and compared data describing temperature regime, diet, growth, and maximum body size across multiple spatial and temporal scales, from country (both exotic and native habitats) and major geographic area (MGA) to rivers and years within MGA. Using these data as inputs, we next used bioenergetic efficiency (BioEff), a relative scalar representing a realized percentage of maximum possible consumption (0–100%) as our primary response variable and a multi-scale, nested, mixed statistical model (GLIMMIX) to evaluate variation among and within spatial scales and as a function of density and elevation. MGA and year (the residual) explained the greatest proportion of variance in BioEff. Temperature varied widely among MGA and was a strong driver of variation in BioEff. We observed surprisingly little variation in the diet of brown trout, except the overwhelming influence of the switch to piscivory observed only in exotic MGA. We observed only a weak signal of density-dependent effects on BioEff; however, BioEff remained <50% at densities >2.5 fish/m2. The trajectory of BioEff across the life span of the fish elucidated the substantial variation in performance among MGAs; the maximum body size attained by brown trout was consistently below 400 mm in native habitat but reached 600 mm outside their native range, where brown trout grew rapidly, feeding in part on naive prey fishes. The integrative, physiological approach, in combination with the intercontinental and comparative nature of our study, allowed us to overcome challenges associated with context-dependent variation in determining invasion success. Overall our results indicate “growth plasticity across the life span” was important for facilitating invasion, and should be added to lists of factors characterizing successful invaders.

Ecology↗

USGS2025

Not just corticosterone: Further characterization of the endocrine response of Kemp’s ridley sea turtles (Lepidochelys kempii) reveals elevated plasma aldosterone concentrations during field capture events

To develop safe and effective management policies, it is important to understand the physiologic effects of fishing interactions and scientific research methods on endangered marine species. In the present study, validated assays for plasma corticosterone, free thyroxine (fT4), and aldosterone were used to assess the endocrine status of 61 presumed healthy, wild Kemp's ridley sea turtles ( Lepidochelys kempii ) that were captured for separate ecological studies using two capture methods (trawl net n = 40; manual capture n = 21). Plasma hormone concentrations were also assessed in relation to eight clinical plasma biochemical analytes. Corticosterone and aldosterone concentrations were moderately high after capture, with significantly higher concentrations in turtles captured by trawl net vs. manual capture. Free thyroxine concentrations were within previously published ranges for healthy individuals of this species. Clinical biochemical data revealed moderately elevated potassium and lactate concentrations in many individuals, with significantly greater lactate concentrations in trawl-captured turtles. Aldosterone concentrations were positively correlated with corticosterone. The results of the present study indicate that Kemp's ridley sea turtles have robust adrenocortical activity immediately after capture, resulting in high plasma concentrations of corticosterone and aldosterone. Researchers who use such methods to access sea turtles can consider these results in planning careful and efficient field studies.

Florida, Louisiana, Mississippi↗

USGS2016

Osmoregulatory physiology and rapid evolution of salinity tolerance in threespine stickleback recently introduced to fresh water

Background: Post-Pleistocene diversification of threespine stickleback in fresh water offers a valuable opportunity to study how changes in environmental salinity shape physiological evolution in fish. In Alaska, the presence of both ancestral oceanic populations and derived landlocked populations, including recent lake introductions, allows us to examine rates and direction of evolution of osmoregulation following halohabitat transition. Hypotheses: Strong selection for enhanced freshwater tolerance will improve survival of recently lake-introduced stickleback in ion-poor conditions compared with their oceanic ancestors. Trade-offs between osmoregulation in fresh water and seawater will allow members of the ancestral population to survive better in response to seawater challenge, as mediated by upregulating salt-secreting transporters in the gill. Poorer hypo-osmoregulatory performance of derived fish will be marked by higher levels of taurine and other organic osmolytes. Methods: We reared clutches at a common salinity from an anadromous and a descendant population, Scout Lake, which has been landlocked for only two generations. We challenged 6-week-old juveniles with extreme low and high salinity treatments and sampled fish over 10 days to investigate putative molecular mechanisms underlying differences in halotolerance. We measured whole-body organic osmolyte content as well as gill Na + /K + -ATPase (NKA) activity and Na + /K + /2Cl − cotransporter (NKCC) protein abundance. Other juveniles from these populations and also from Cheney Lake, a fourth-generation landlocked descendant, were gradually salt-acclimated to determine maximum halotolerance limits. Results: Scout Lake stickleback exhibited 67% higher survival in fresh water than the ancestral anadromous population, but individuals from both groups exhibited similar seawater tolerance. Likewise, the gradual salinity threshold for each population was equivalent (71 ppt). Gill NKA activity and NKCC abundance were both higher in seawater-challenged fish, but did not differ between populations. Sticklebacks from both populations responded to acute salinity stress by transiently increasing osmolyte levels in seawater and decreasing them in fresh water. Conclusion: Enhanced freshwater tolerance has evolved rapidly in recently landlocked stickleback compared with their anadromous ancestors (0.569 haldanes), but the former have retained ancestral seawater-osmoregulatory function.

Evolutionary Ecology Research↗

USGS1989

Effect of rearing density on poststocking survival of lake trout in Lake Ontario

Six paired lots of yearling lake trout ( Salvelinus namaycush ) reared at densities of 41,000 and 51,000 fish per raceway during their last 9 months in the hatchery were stocked in Lake Ontario. Poststocking survival of the high-density (HD) and low-density (LD) fish was not different for the 1982 year-class. However, for the 1983 year-class, mean survival was significantly different between HD and LD fish ( P < 0.01). Mean survival of HD fish was only 76% that of LD fish ( P < 0.01), and most of the mortality attributable to rearing conditions had apparently occurred within 2 months after stocking. Mean size at stocking was not different for HD and LD fish of the 1982 year-class, but for the 1983 year-class, the LD fish were 6% longer and 22% heavier than the HD fish. Mean lengths and weights of LD and HD fish were not different in samples collected in Lake Ontario at age 2 and older. Size at stocking was not likely the factor that caused the difference in survival. Rather, the rearing conditions (probably water exchange rate in relation to number of fish in the raceway) that resulted in slower growth of the HD fish of the 1983 year-class also caused them to be poorer physiologically than the LD fish. The number of yearling lake trout per rearing unit that will result in maximum contribution to populations in the Great Lakes after stocking may be lower than the rearing densities customarily used at some hatcheries.

Progressive Fish-Culturist↗

USGS2014

Physiological and ecological effects of increasing temperature on fish production in lakes of Arctic Alaska

Lake ecosystems in the Arctic are changing rapidly due to climate warming. Lakes are sensitive integrators of climate-induced changes and prominent features across the Arctic landscape, especially in lowland permafrost regions such as the Arctic Coastal Plain of Alaska. Despite many studies on the implications of climate warming, how fish populations will respond to lake changes is uncertain for Arctic ecosystems. Least Cisco (Coregonus sardinella) is a bellwether for Arctic lakes as an important consumer and prey resource. To explore the consequences of climate warming, we used a bioenergetics model to simulate changes in Least Cisco production under future climate scenarios for lakes on the Arctic Coastal Plain. First, we used current temperatures to fit Least Cisco consumption to observed annual growth. We then estimated growth, holding food availability, and then feeding rate constant, for future projections of temperature. Projected warmer water temperatures resulted in reduced Least Cisco production, especially for larger size classes, when food availability was held constant. While holding feeding rate constant, production of Least Cisco increased under all future scenarios with progressively more growth in warmer temperatures. Higher variability occurred with longer projections of time mirroring the expanding uncertainty in climate predictions further into the future. In addition to direct temperature effects on Least Cisco growth, we also considered changes in lake ice phenology and prey resources for Least Cisco. A shorter period of ice cover resulted in increased production, similar to warming temperatures. Altering prey quality had a larger effect on fish production in summer than winter and increased relative growth of younger rather than older age classes of Least Cisco. Overall, we predicted increased production of Least Cisco due to climate warming in lakes of Arctic Alaska. Understanding the implications of increased production of Least Cisco to the entire food web will be necessary to predict ecosystem responses in lakes of the Arctic.

Alaska↗

USGS2018

Influence of baffles on upstream passage of brook trout and brown trout in an experimental box culvert

There is much to learn about improving baffle designs to increase successful fish passage through culverts. A fish’s motivation to attempt entry into the culvert is essential. Upon entry, successful passage will largely depend on the physiological ability of the fish to navigate the entire culvert length. In this study, the motivation of brook trout ( Salvelinus fontinalis (Mitchill, 1814)) and brown trout ( Salmo trutta Linnaeus, 1758) to attempt ascent of an experimental flume, which mimics a roadway culvert left bare (smooth) or fitted with either spoiler or weir baffles, is assessed. Performance, measured as maximum distance of ascent within the flume, is also quantified. The bare flume was the most motivating for brook trout, and the weirs were most motivating for brown trout. As a rule, brown trout showed less motivation to stage attempts than brook trout, except within the weir baffle treatments. Performance was greatest in the weirs for smaller trout and in the spoiler baffles for larger trout. Our findings suggest that baffle form influences passage rates at road crossings in ways previously unknown and further stresses the importance of considering fish motivation and performance together when assessing the efficacy of baffle forms.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS1994

Effects of multiple acute stressors on the predator avoidance ability and physiology of juvenile Chinook salmon

Northern squaw fish Ptychocheilus oregonensis are the predominant predators of juvenile Pacific salmonids Oncorhynchus spp. in the Columbia River, and their predation rates are greatest just below dams. Because juvenile salmonids are commonly subjected to multiple stressors at dams in the course of their seaward migration, high predation rates below dams may be due in part to an increase in the vulnerability of stressed fish. I conducted laboratory experiments to examine the predator avoidance ability and physiological stress responses of juvenile chinook salmon O. tshawytscha subjected to treatments (stressors) designed to simulate routine hatchery practices (multiple handlings) or dam passage (multiple agitations). Both stressors resulted in lethargic behavior in the fish, and agitation also caused disorieniation and occasional injury. When equal numbers of stressed and unstressed fish were exposed to northern squawfish for up to 1 h, significantly more stressed fish were eaten, but this effect was not evident during longer exposures. The lack of differential predation in trials lasting up to 24 h can be explained by the rapid development of schooling behavior in the prey, but other possibilities exist, such as changing ratios of stressed and unstressed prey over time. Concentrations of plasma cortisol, glucose, and lactate in fish subjected to multiple stressors were similar and sometimes cumulative, returned to prestress levels within 6-24 h, and correlated poorly with predator avoidance ability. My results suggest that juvenile salmonids are capable of avoiding predators within 1 h after being subjected to multiple acute stressors even though physiological homeostasis may be altered for up to 24 h. Therefore, because juvenile salmonids typically reside in lailrace areas for only a short time after dam passage, measures aimed at reducing physical stress or protecting them as they migrate through dam tailraces may help alleviate the relatively intense predation in these areas.

Transactions of the American Fisheries Society↗

USGS2019

Phylogeny and foraging mode correspond with thiaminase activity in freshwater fishes: Potential links to environmental factors

Knowledge of the dietary components of fish species is important for understanding their growth, survival, and recruitment. Deficiency in thiamine (vitamin B1) leading to reproductive failure and physiological illness among freshwater fishes has been attributed to thiaminase activity in fish in the Great Lakes and the New York Finger Lakes, but the causes of variation in thiaminase activity among freshwater fishes is unclear. We characterized thiaminase activity in 29 species of freshwater fishes across 7 ray-finned and 1 jawless family. All fish were further categorized by phylogeny, trophic category (trophic level and feeding mode), and native or non-native status to evaluate how ecological processes correspond with thiaminase activity. Thiaminase activity varied significantly across species, families, trophic factors, phylogenetic groups, and sites. Teleosts that were more recently derived had higher thiaminase activity than more basal species. Thiaminase activity was also higher among herbivores than omnivores or carnivores. This trend was clearest in the Cyprinidae family, which had the greatest range in thiaminase activity and a wide range in trophic-level position and trophic categories (herbivores, omnivores, and carnivores). Variation in average thiaminase activity of Spotfin Shiners (Cyprinella spiloptera) among sites within a watershed was correlated with anthropogenic and natural components of land cover. Our study contributes much-needed quantitative ecological information related to thiaminase activity in a suite of fish species that vary in evolutionary history, trophic level, and foraging modes. However, more studies are needed to identify interacting causes of thiaminase variation and examine the implications of these findings on the overall health of aquatic populations and freshwater ecosystems.

Freshwater Science↗