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At least 199 records · Page 11Linked to original sources
USGS2018

Are hatchery-reared Rainbow Trout and Brown Trout effective predators on juvenile native fish?

Hatchery‐reared Rainbow Trout Oncorhynchus mykiss and Brown Trout Salmo trutta are typically fed exclusively on commercially prepared pelleted feeds and have no experience catching or consuming live fish at the time of stocking. Despite this lack of predation experience, it is commonly assumed that stocked Rainbow Trout and Brown Trout will adversely impact native fish populations by preying upon juvenile native fish. We evaluated the relative predation effectiveness of wild‐caught Rainbow Trout (210–389 mm TL) and Brown Trout (185–313 mm TL) compared with hatchery‐reared Rainbow Trout (198–321 mm TL) and Brown Trout (196–290 mm TL). We used Bonytail Gila elegans (60–85 mm TL), Humpback Chub Gila cypha (24–59 mm TL), and Roundtail Chub Gila robusta (40–65 mm TL) as prey in overnight predation trials conducted in the laboratory from 2013 to 2016. After 14 d in a captive setting, wild Rainbow Trout and Brown Trout consumed >70% of prey in trials with no cover, while hatchery‐reared fish consumed <30% of prey. In addition, we evaluated if the predation ability of hatchery fish would improve over time by feeding them Fathead Minnows Pimephales promelas , rather than pelleted feed, for up to 30 d. Predation success of Rainbow Trout and Brown Trout increased by an average of 28% and 21%, respectively, after 14 d of eating exclusively fish. Rainbow Trout tested after 30 d of eating fish increased in their ability to catch and eat small prey by an average of 29%. The predation effectiveness of hatchery‐reared fish appears to improve with experience eating live fish. Although stocking Rainbow Trout and Brown Trout does increase the number of predators present in natural systems, the relative predation threat posed by hatchery‐reared fish may be less than that of wild fish, especially in locations where stocked fish do not persist. Lack of experience in catching fish and the effects of captive rearing practices and environments on both physiology and behavior all likely contribute to reduced predation effectiveness of hatchery Rainbow Trout and Brown Trout.

North American Journal of Fisheries Management↗
USGS2012

New insights into gill ionocyte and ion transporter function in euryhaline and diadromous fish

Teleost fishes are able to acclimatize to seawater by secreting excess NaCl by means of specialized “ionocytes” in the gill epithelium. Antibodies against Na + /K + -ATPase (NKA) have been used since 1996 as a marker for identifying branchial ionocytes. Immunohistochemistry of NKA by itself and in combination with Na + /K + /2Cl − cotransporter and CFTR Cl − channel provided convincing evidence that ionocytes are functional during seawater acclimation, and also revealed morphological variations in ionocytes among teleost species. Recent development of antibodies to freshwater- and seawater-specific isoforms of the NKA alpha-subunit has allowed functional distinction of ion absorptive and secretory ionocytes in Atlantic salmon. Cutaneous ionocytes of tilapia embryos serve as a model for branchial ionocytes, allowing identification of 4 types: two involved in ion uptake, one responsible for salt secretion and one with unknown function. Combining molecular genetics, advanced imaging techniques and immunohistochemistry will rapidly advance our understanding of both the unity and diversity of ionocyte function and regulation in fish osmoregulation.

Respiratory Physiology and Neurobiology↗
USGS2009

Ecological Requirements for Pallid Sturgeon Reproduction and Recruitment in the Lower Missouri River: A Research Synthesis 2005-08

This report provides a synthesis of results obtained between 2005 and 2008 from the Comprehensive Sturgeon Research Program, an interagency collaboration between the U.S. Geological Survey, Nebraska Game and Parks Commission, U.S. Fish and Wildlife Service, and the U.S. Army Corps of Engineers' Missouri River Recovery - Integrated Science Program. The goal of the Comprehensive Sturgeon Research Program is to improve fundamental understanding of reproductive ecology of the pallid sturgeon with the intent that improved understanding will inform river and species management decisions. Specific objectives include: *Determining movement, habitat-use, and reproductive behavior of pallid sturgeon; *Understanding reproductive physiology of pallid sturgeon and relations to environmental conditions; *Determining origin, transport, and fate of drifting pallid sturgeon larvae, and evaluating bottlenecks for recruitment of early life stages; *Quantifying availability and dynamics of aquatic habitats needed by pallid sturgeon for all life stages; and *Managing databases, integrating understanding, and publishing relevant information into the public domain. Management actions to increase reproductive success and survival of pallid sturgeon in the Lower Missouri River have been focused on flow regime, channel morphology, and propagation. Integration of 2005-08 Comprehensive Sturgeon Research Program research provides insight into linkages among flow regime, re-engineered channel morphology, and pallid sturgeon reproduction and survival. The research approach of the Comprehensive Sturgeon Research Program integrates opportunistic field studies, field-based experiments, and controlled laboratory studies. The field study plan is designed to explore the role of flow regime and associated environmental cues using two complementary approaches. An upstream-downstream approach compares sturgeon reproductive behavior between an upstream section of the Lower Missouri River with highly altered flow regime to a downstream section that maintains much of its pre-regulation flow variability. The upstream section also has the potential for an experimental approach to compare reproductive behavior in years with pulsed flow modifications ('spring rises') to years without. The reproductive cycle of the female sturgeon requires several years to progress through gonadal development, oocyte maturation, and spawning. Converging lines of evidence support the hypothesis that maturation and readiness to spawn in female sturgeon is cued many months before spawning. Information on reproductive readiness of shovelnose sturgeon indicates that sturgeon at different locations along the Lower Missouri River between St. Louis and Gavins Point Dam are all responding to the same early cue. Although not a perfect surrogate, the more abundant shovelnose sturgeon is morphologically, physiologically, and genetically similar to pallid sturgeon, and thereby provides a useful comparative model for the rarer species. Day length is the likely candidate to define a temporal spawning window. Within the spawning window, one or more additional, short-term, and specific cues may serve to signal ovulation and release of gametes. Of three potential spawning cues - water temperature, water discharge, and day of year - water temperature is the most likely proximate cue because of the fundamental physiological role temperature plays in sturgeon embryo development and survival, and the sensitivity of many fish hormones to temperature change. It also is possible that neither temperature nor discharge is cueing spawning; instead, reproductive behavior may result from the biological clock advancing an individual fish's readiness to spawn day after day through the spawning period until the right moment, independent of local environmental conditions. Separation of the individual effects of discharge events, water temperature, and other possible factors, such as proximity to male

Scientific Investigations Report↗
USGS2003

Physiological characteristics of wild Atlantic salmon post-smolts during estuarine and coastal migration

Changes were measured in some of the major physiological variables associated with seawater adaptability, growth and energetics in wild Atlantic salmon Salmo salar smolts and post-smolts migrating from the river and through the estuary, fjord and coastal areas in the River Orkla and the Trondheimsfjord, Norway during late May to early June. Gill Na+,K+-ATPase activity increased to levels of 12-16 ??mol ADP mg protein-1 h -1 in post-smolts caught in higher salinity zones, probably representing long-term levels of Atlantic salmon post-smolts in oceanic conditions. Muscle moisture was regulated within narrow limits (77.7-78.7%) in fish from all zones during both years, suggesting that post-smolts adapt to marine conditions without any long-term disturbance of hydro-mineral balance. Lipid and glycogen content showed a general trend towards depletion from the river, through the fjord and into the ocean. There was, however, no significant change in protein content. The present results confirm that smolts are naturally 'energy deficient' during downstream migration, and suggest that post-smolts also mobilize energy reserves during their early marine phase, while protein is allocated for somatic growth. Plasma growth hormone (GH) levels increased transiently during passage through the estuary and fjord, with lower levels observed in post-smolts caught off-shore, i.e. in fish which were feeding on marine prey and had adapted to the marine environment. These physiological changes may confer substantial selective advantages during the critical early marine phase of anadromous salmonids, and hence are adaptive for long-term survival in sea water. ?? 2003 The Fisheries Society of the British Isles.

Journal of Fish Biology↗
USGS2017

Migration trends of Sockeye Salmon at the northern edge of their distribution

Climate change is affecting arctic and subarctic ecosystems, and anadromous fish such as Pacific salmon Oncorhynchus spp. are particularly susceptible due to the physiological challenge of spawning migrations. Predicting how migratory timing will change under Arctic warming scenarios requires an understanding of how environmental factors drive salmon migrations. Multiple mechanisms exist by which environmental conditions may influence migrating salmon, including altered migration cues from the ocean and natal river. We explored relationships between interannual variability and annual migration timing (2003–2014) of Sockeye Salmon O. nerka in a subarctic watershed with environmental conditions at broad, intermediate, and local spatial scales. Low numbers of Sockeye Salmon have returned to this high-latitude watershed in recent years, and run size has been a dominant influence on the migration duration and the midpoint date of the run. The duration of the migration upriver varied by as much as 25 d across years, and shorter run durations were associated with smaller run sizes. The duration of the migration was also extended with warmer sea surface temperatures in the staging area and lower values of the North Pacific Index. The midpoint date of the total run was earlier when the run size was larger, whereas the midpoint date was delayed during years in which river temperatures warmed earlier in the season. Documenting factors related to the migration of Sockeye Salmon near the northern limit of their range provides insights into the determinants of salmon migrations and suggests processes that could be important for determining future changes in arctic and subarctic ecosystems.

Alaska↗
USGS1976

Physiological response to hooking stress in hatchery and wild rainbow trout (Salmo gairdneri)

This study evaluated the physiological response of rainbow trout to hooking stress after being played under standardized conditions (0&ndash;5 min) and estimated the time needed for recovery (to 72 h). Plasma osmolality and chloride measurements were used to evaluate osmoregulatory disturbances and gill ion-exchange function, and plasma glucose was used as an index of the generalized nonspecific physiological stress response. Hooking stress caused more severe blood chemistry differences in hatchery fish than in wild trout. Also, hooking stress imposed a greater stress on larger than on smaller hatchery rainbow trout. Higher water temperatures aggravated the delayed hyperglycemia and hyperchloremia in both hatchery and wild trout but only about 3 days were needed for recovery at 4, 10, or 20 C.

Transactions of the American Fisheries Society↗
USGS2014

In vitro immune functions in thiamine-replete and -depleted lake trout ( Salvelinus namaycush )

In this study we examined the impacts of in vivo thiamine deficiency on lake trout leukocyte function measured in vitro. When compared outside the context of individual-specific thiamine concentrations no significant differences were observed in leukocyte bactericidal activity or in concanavalin A (Con A), and phytohemagglutinin-P (PHA-P) stimulated leukocyte proliferation. Placing immune functions into context with the ratio of in vivo liver thiamine monophosphate (TMP – biologically inactive form) to thiamine pyrophosphate (TPP – biologically active form) proved to be the best indicator of thiamine depletion impacts as determined using regression modeling. These observed relationships indicated differential effects on the immune measures with bactericidal activity exhibiting an inverse relationship with TMP to TPP ratios, Con A stimulated mitogenesis exhibiting a positive relationship with TMP to TPP ratios and PHA-P stimulated mitogenesis exhibiting no significant relationships. In addition, these relationships showed considerable complexity which included the consistent observation of a thiamine-replete subgroup with characteristics similar to those seen in the leukocytes from thiamine-depleted fish. When considered together, our observations indicate that lake trout leukocytes experience cell-type specific impacts as well as an altered physiologic environment when confronted with a thiamine-limited state.

Fish & Shellfish Immunology↗
USGS2003

Effect of swimming activity on relative weight and body composition of juvenile rainbow trout

Fisheries managers often assess body condition using relative weight (Wr) because it provides a comparative measure of fish plumpness among individuals and populations. However, it is not known whether the morphological information that Wr summarizes reflects physiological measures, such as relative lipid reserves, in rainbow trout Oncorhynchus mykiss. The purpose of this study was to determine whether swimming activity affects either the Wr or proximate body composition of juvenile (total length, 170-260 mm) rainbow trout. When rainbow trout from a hatchery were fed ad libitum for 147 d, inactive (no current) and active (15 cm/s current velocity) fish did not differ in Wr However, inactive rainbow trout maintained relatively constant lipid levels, whereas active fish declined in lipid content. Relative weight may provide a comparable measure of body form, but it is not an accurate index of lipid content between active and inactive rainbow trout fed an excess ration. For assessing the physiological condition of rainbow trout, measurement of proximate body composition appears to be more accurate than indices based on length and weight.

North American Journal of Fisheries Management↗
USGS2022

Backpack electrofishing does not contribute to external signs of gas bubble trauma in sculpins

We exposed prickly sculpin Cottus asper and reticulate sculpin Cottus perplexus to electroshock and sham treatments in a controlled laboratory setting to determine if backpack electrofishing contributed to or exacerbated external signs of gas bubble trauma (GBT) in fish exposed to elevated total dissolved gas (TDG) levels. Fish were exposed to 115, 120 and 125% TDG (measured as percent of saturation) for various amounts of time (24–144 h) then subjected to a 5-s electroshock or sham treatment of no electroshock. Fish were examined to determine the incidence of GBT pre- and post-treatment, and all aspects (i.e., dorsal, ventral, left and right sides) of each fish were photographed. Across all TDG levels in all trials, no sculpin showed any change in GBT incidence following treatment. Analysis of GBT signs evident in photographs of 68 fish found no evidence of change in mean pre- and post-treatment gas bubble sizes in fish in any TDG trial, nor were any new gas bubbles found following treatment. We are aware of no physiological mechanism by which backpack electrofishing can cause GBT in sculpin, and as such, we believe using this gear should not increase GBT incidence rates in sculpin.

Aquaculture, Fish and Fisheries↗
USGS2021

Use of non-lethal endpoints to establish water quality requirements and optima of the endangered Topeka shiner (Notropis topeka)

Water quality standards based on sub-lethal effects and performance optima for aquatic organisms, rather than onset of mortality, are more ecologically relevant for management of species of conservation concern. We investigated the effects of hypoxia, temperature (with acclimation), nitrogenous chemical compounds, and chloride on Topeka shiners ( Notropis topeka ) by monitoring behavioral responses to a reduction in oxygen and, using swimming speed, determining thermal optima and onset of effect for concentrations of nitrogenous compounds and chloride. We found ASR 50 (i.e., dissolved oxygen concentrations where 50% of fish use aquatic surface respiration) to be 1.65 mg/L and ASR 90 to be 1.08 mg/L of dissolved oxygen. Optimum temperatures for the species ranged from 17.7 to 28.0 °C, while predicted 100% mortality ranged from 33.7 to 40.3 °C, depending on the temperature at which fish were acclimated prior to experiments. Ammonia and sodium chloride reduced swimming speed at concentrations below known LC 50 values, while nitrite concentrations did not correspond with swimming speed, but rather, post-experiment mortality. This provides insight into where Topeka shiners can not only persist, but also thrive. Although swimming speed may not be a suitable metric for determining the effects of all contaminants, our focus on optima and sub-lethal effects over tolerance allows selections of the most suitable reintroduction site matching the species’ physiological profile.

Environmental Biology of Fishes↗
USGS2022

Metabolic costs associated with seawater acclimation in a euryhaline teleost, the fourspine stickleback (Apeltes quadracus)

The cost of osmoregulation in teleosts has been debated for decades, with estimates ranging from one to 30 % of routine metabolic rate. The variation in the energy budget appears to be greater for euryhaline fish due to their ability to withstand dynamic salinity levels. In this study, a time course of metabolic and physiological responses of the euryhaline fourspine stickleback ( Apeltes quadracus ) acclimated to freshwater (FW) and then exposed to seawater (SW) was examined. There was 18% mortality in the first 3 days following exposure to SW, with no mortalities in the FW control group. Gill Na + /K + -ATPase (NKA) activity, an index of osmoregulatory capacity, increased 2.6-fold in SW fish peaking on days 7 and 14. Gill citrate synthase activity, an index of aerobic capacity, was 50–62% greater in SW than FW fish and peaked on day 7. Tissue water content was significantly lower in the SW fish on day 1 only, returning to FW levels by day 3. Routine metabolic rate was decreased within 24 h of SW exposure and was maintained slightly (8–22%) but significantly lower in SW compared to FW water controls throughout the 2-week experiment. These results indicate that elevated salinity resulted in increased SW osmoregulatory and aerobic capacity in the gill, but with a reduced whole animal metabolic rate to this euryhaline species.

Comparative Biochemistry and Physiology Part B: Bi↗
USGS2013

The effects of salinity exposure on multiple life stages of a common freshwater mussel, Elliptio complanata

There is growing concern over the effects of increased salinization on freshwater organisms, which are largely unknown for unionid mussels. Adult and larval Elliptio complanata were exposed to low-level salt concentrations to determine the effects on mussel survival, physiology, and reproduction. Adults were exposed to salt concentrations of 0 parts per thousand (ppt), 2 ppt, 4 ppt, and 6 ppt NaCl and monitored over 7 d for mortality. Treatment groups exposed to 6 ppt and 4 ppt experienced 50% mortality at day 3 and day 4, respectively, with complete mortality by day 7. No mortality was observed in the other treatments. Adults were also exposed to sublethal salinity levels of 1 ppt and 2 ppt NaCl for 4 wk to determine physiological consequences of prolonged salinity exposure. Mussels exposed to 1 ppt and 2 ppt experienced reduced metabolic rates within the first 24 h of exposure that recovered to control levels in the 1-ppt treatment within 7 d. Metabolic recovery did not occur in the 2-ppt treatment by the end of 28 d. Glochidia exposed to 3-ppt NaCl during attachment to their host fish suffered a reduction in attachment success and metamorphosis, resulting in a 10-fold reduction in the number of juveniles produced per host fish. The present study demonstrates that low levels of salt can have a dramatic effect on the reproduction, physiology, and survival of freshwater mussels

Environmental Toxicology and Chemistry↗
USGS2020

A weight-of-evidence approach for defining thermal sensitivity in a federally endangered species

1. Managing for threatened and endangered species under changing environmental conditions is a challenge faced by resource managers worldwide. Lack of basic knowledge of the biology and habitat requirements of these species can contribute to this difficulty, but is confounded by the limitations of working with rare (i.e. few individuals) species or unrefined methods for evaluating stress. 2. A weight of evidence approach was used to evaluate the thermal biology of the federally endangered dwarf wedgemussel ( Alasmidonta heterodon ), utilizing cumulative results from multiple experimental assessments, co-occurring species, and their host fish to begin defining thermal limits and optimal conditions for the species. 3. Results suggest that dwarf wedgemussel and its host fish are thermally sensitive species compared to other Atlantic-slope mussels, with lower critical thermal maximum and selection of reduced temperatures during choice experiments. 4. Physiological studies resulted in lack of statistical significance primarily due to low power which was a function of sample size, one unavoidable problem when studying rare species. Given these limitations, thermal choice and CTM may be more useful endpoints than physiological processes such as clearance and respiration rates when dealing with sample size limitations. 5. These results suggest that management strategies that avoid exposing dwarf wedgemussel and its thermally sensitive host fish to extreme temperatures could be important for species conservation.

New Jersey, Pennsylvania↗
USGS2019

Comparisons of stereological and other approaches for quantifying macrophage aggregates in piscine spleens

Macrophage aggregates (MA s) are focal accumulations of pigmented macrophages in the spleen and other tissues of fish. A central role of MA s is the clearance and destruction of degenerating cells and recycling of some cellular components. Macrophage aggregates also respond to chemical contaminants and infectious agents and may play a role in the adaptive immune response. Tissue damage or physiological stress can result in increased MA accumulation. As a result, MA s may be sensitive biomarkers of environmental stress in fish. Abundance of MA s in tissues has been reported in a variety of ways—most commonly as density, mean size, and relative area—but the utility of these estimates has not been compared. In this study, four different types of splenic MA abundance estimates (abundance score, density, relative area, and total volume) were compared in two fish populations (Striped Bass Morone saxatilis and White Perch M. americana ) with a wide range in ages. Stereological estimates of total volume indicated an increase in MA abundance with spleen volume, which generally corresponded to fish age, and with splenic infections (mycobacteria or trematode parasites). Abundance scores were generally limited in the ability to detect changes in MA abundance by these factors, whereas density estimates were greatly influenced by changes in spleen volume. In some instances, densities declined while the total volume of MA s and spleen volume increased. Experimentally induced acute stress resulted in a decrease in spleen volume and an increase in MA density, although the total volume of MA s remained unchanged. Relative area estimates accounted for the size and number of MA s but not for changes in organ volume. Total volume is an absolute measure of MA abundance irrespective of changes in organ volume or patterns of accumulation and may provide an improved means of quantifying MA s in the spleens of fish.

Maryland↗
USGS2015

Causes of mortality in green turtles from Hawaii and the insular Pacific exclusive of fibropapillomatosis

Fibropapillomatosis (FP) comprises a majority of green turtle stranding in Hawaii; however, green turtles in the Pacific are also susceptible to non-FP related causes of death. We present here necropsy findings from 230 free-ranging green turtles originating from Hawaii, the Mariana archipelago, Palmyra Atoll, American Samoa, and Johnston Atoll that died from non-FP related causes. Most turtles died from fishing-induced or boat strike trauma followed by infectious/inflammatory diseases, nutritional problems (mainly cachexia), and an array of physiologic problems. Infectious/inflammatory problems included bacterial diseases of the lungs, eyes, liver or intestines, spirorchid fluke infection, or polyarthritis of unknown origin. Likelihood of a successful diagnosis of cause of death was a function of post-mortem decomposition. Fibropapillomatosis was not seen in turtles submitted from outside Hawaii. The preponderance of anthropogenic causes of mortality offers some management opportunities to mitigate causes of death in these animals by, for example, implementing measures to decrease boating and fishing interactions.

Diseases of Aquatic Organisms↗
USGS1990

Whole body and tissue blood volumes of two strains of rainbow trout ( Oncorhynchus mykiss )

1. Estimates of apparent packed cell, plasma and total blood volumes for the whole body and for 13 selected tissues were compared between Kamloops and Wytheville strains of rainbow trout ( Oncorhynchus mykiss ) by the simultaneous injection of two vascular tracers, radiolabeled trout erythrocytes ( 51 Cr-RBC) and radioiodated bovine serum albumin ( 125 I-BSA). 2. Whole body total blood volume, plasma volume and packed cell volume were slightly, but not significantly greater in the Wytheville trout, whereas, the apparent plasma volumes and total blood volumes in 4 of 13 tissues were significantly greater in the Kamloops strain. 3. Differences were most pronounced in highly perfused organs, such as the liver and kidney and in organs of digestion such as the stomach and intestines. 4. Differences in blood volumes between the two strains may be related to the greater permeability of the vascular membranes in the Kamloops strain fish.

Comparative Biochemistry and Physiology, Part A: M↗
USGS1971

Na+, K+-activated-ATPase inhibition in rainbow trout: A site for organochlorine pesticide toxicity?

1. The Na + , K + -activated, Mg 2+ -dependent-ATPase enzyme system in a heavy microsomal fraction of rainbow trout ( Salmo gairdneri ) brain was inhibited in vitro by chlorinated hydrocarbon pesticides. 2. T 50 (concentration at 50 per cent inhibition) values for dicofol, endosulfan and DDT were 5 × 10 −6 , 3 × 10 −5 and 1 × 10 −4 M respectively. Similar inhibition by these pesticides occurred in kidney and gill ATPase preparations. 3. An unexpected finding was a failure of the classic inhibitor, ouabain, to block the Na + , K + -activated component of ATPase activity in the gill. 4. It is suggested that inhibition of ATPase activity may be a causal factor in the toxic effects of organochlorine pesticides in fishes.

Comparative Biochemistry and Physiology, Part B: C↗