Bioenergetic consequences of repeated catch-and-release fisheries interactions on adult steelhead across a range of ecologically relevant water temperatures

The biological consequences of catch-and-release angling have been studied for decades, yet little is known about the compounding effects of repeated recreational fisheries recaptures on the physiology and behaviour of angled fish. Using heart rate biologgers and behavioural assays, this study investigated the physiological and behavioural consequences of multiple simulated angling events (i.e., repeated stressors) on female steelhead (Oncorhynchus mykiss), under current (6 °C) and future (11 °C) water temperature scenarios. While steelhead in the warmer water temperature scenario demonstrated alterations in cardiac function (e.g., increases in maximum heart rate and scope of heart rate) and evidence of behavioural impairments (e.g., decreases in chase activity and landing time) over the course of two simulated angling events, cold water treated fish had negligible change. Fish subjected to two simulated angling events under warm water temperature conditions tended to demonstrate an increase in recovery time and scope for heart rate, and a decrease in resting heart rate. A second experiment was conducted to test for sex-specific differences in the heart rate response of steelhead subjected to an increase in water temperature. Females demonstrated a higher scope for heart rate when compared to males during the event and during recovery. More work is needed to better understand the interaction between multiple angling events and recovery from these events at various water temperatures, and the biological basis for sex-specific differences in cardiac function and response to challenges. This study contributes to a growing body of evidence on the effects of repeated stressors on wild fish.

Ecology of Exercise in Wild Fish: Integrating Concepts of Individual Physiological Capacity, Behavior, and Fitness Through Diverse Case Studies

SYNOPSIS

Wild animals maximize fitness through certain behaviors (e.g., foraging, mating, predator avoidance) that incur metabolic costs and often require high levels of locomotor activity. Consequently, the ability of animals to achieve high fitness often relies on their physiological capacity for exercise (aerobic scope) and/or their ability to acquire and utilize energy judiciously. Here, we explore how environmental factors and physiological limitations influence exercise and metabolism in fish while foraging, migrating to spawning grounds, and providing parental care. We do so with three case studies that use a number of approaches to studying exercise in wild fish using biologging and biotelemetry platforms. Bonefish (Albula vulpes) selectively use shallow water tropical marine environments to forage when temperatures are near optimal for aerobic scope and exercise capacity. Bonefish energy expenditure at upper thermal extremes is maximal while activity levels diminish, likely caused by reduced aerobic scope. Pacific salmon (Oncorhynchus spp.) reproductive migrations frequently involve passage through hydraulically challenging areas, and their ability to successfully pass these regions is constrained by their physiological capacity for exercise. Aerobic scope and swim performance are correlated with migration difficulty among sockeye salmon (O. nerka) populations; however, depletion of endogenous energy stores can also limit migration success. In another example, male smallmouth bass (Micropterus dolomieu) allocate a significant amount of energy to nest-guarding behaviors to protect their developing brood. Smallmouth bass body size, endogenous energy reserves, and physiological state influence nest-guarding behaviors and reproductive success. We suggest that in some scenarios (e.g., bonefish foraging, Pacific salmon dam passage) metabolic capacity for exercise may be the strongest determinant of biological fitness, while in others (e.g., long distance salmon migration, smallmouth bass parental care) energy stores may be more important. Interactions among environmental and ecological factors, fish behavior, and fish physiology offer important avenues of mechanistic inquiry to explain ecological dynamics and demonstrate how exercise is fundamental to the ecology of fish.

Physiological stress response, reflex impairment and delayed mortality of white sturgeon Acipenser transmontanus exposed to simulated fisheries stressors

White sturgeon (Acipenser transmontanus) are the largest freshwater fish in North America and a species exposed to widespread fishing pressure. Despite the growing interest in recreational fishing for white sturgeon, little is known about the sublethal and lethal impacts of angling on released sturgeon. In summer (July 2014, mean water temperature 15.3°C) and winter (February 2015, mean water temperature 6.6°C), captive white sturgeon (n = 48) were exposed to a combination of exercise and air exposure as a method of simulating an angling event. After the stressor, sturgeon were assessed for a physiological stress response, and reflex impairments were quantified to determine overall fish vitality (i.e. capacity for survival). A physiological stress response occurred in all sturgeon exposed to a fishing-related stressor, with the magnitude of the response correlated with the duration of the stressor. Moreover, the stress from exercise was more pronounced in summer, leading to higher reflex impairment scores (mean ± SEM, 0.44 ± 0.07 and 0.25 ± 0.05 in summer and winter, respectively). Reflex impairment was also correlated with lactate concentrations (e.g. physiological stress measures related to exhaustive exercise; r = 0.53) and recovery time (r = 0.76). Two mortalities occurred >24 h after the cessation of treatment in the summer. Given that natural habitats for white sturgeon can reach much higher temperatures than those presented in our study, we caution the use of this mortality estimate for a summer season, because latent mortality could be much higher when temperatures exceed 16°C. This is the first experiment investigating the physiological disturbance and reflex impairment of capture and release at two temperatures on subadult/adult white sturgeon, and the results suggest that future research needs to examine the longer term and fitness consequences of extended play and air exposure times, because these are largely unknown for wild populations.

Is fishing selective for physiological and energetic characteristics in migratory adult sockeye salmon?

There is extensive evidence that fishing is often selective for specific phenotypic characteristics, and that selective harvest can thus result in genotypic change. To date, however, there are no studies that evaluate whether fishing is selective for certain physiological or energetic characteristics that may influence fish behaviour and thus vulnerability to capture. Here, adult sockeye salmon (Oncorhynchus nerka) were used as a model to test the null hypothesis that fishing is not selective for specific physiological or energetic traits. Fish were intercepted during their spawning migrations, implanted with a gastric radio transmitter, and biopsied (i.e., non-lethally sampled for blood, gill tissue and quantification of energetic status). In both 2003 and 2006, we tagged and biopsied 301 and 770 sockeye salmon, respectively, in the marine environment en route to their natal river system to spawn. In 2006 an additional 378 individuals were tagged and biopsied in freshwater. We found that 23 (7.6%) of the marine fish tagged in 2003, 78 (10.1%) of the marine fish tagged in 2006 and 57 (15.1%) of the freshwater fish tagged in 2006 were harvested by one of three fisheries sectors that operate in the coastal marine environment and the Fraser River (i.e. commercial, recreational or First Nations fisheries between the site of release and Hell's Gate in the Fraser River, approximately 250 km upriver and 465 km from the ocean tagging site). However, fisheries were not open continually or consistently in different locations and for different fisheries sectors necessitating a paired analytical approach. As such, for statistical analyses we paired individual fish that were harvested with another fish of the same genetic stock that was released on the same date and exhibited similar migration behaviour, except that they successfully evaded capture and reached natal spawning grounds. Using two-tailed Wilcoxon matched pairs signed-rank tests, we revealed that the physiological and energetic characteristics of harvested fish did not differ from those of the successful migrants despite evaluating a number of biochemical (e.g. plasma metabolites, cortisol, plasma ions, gill Na⁺/K⁺-ATPase) and energetic (e.g. gross somatic energy density) variables (P's all >0.10). However, for some analyses we suffered low statistical power and the study design had several shortcomings that could have made detection of differences difficult. We suggest that additional research explore the concept of fishing-induced selection for physiological characteristics because physiology is closely linked to three traits where fisheries-induced selection does occur (i.e. life-history, behaviour and morphology).

Modeling the potential impacts of climate change on Pacific salmon culture programs: an example at Winthrop National Fish Hatchery

Hatcheries have long been used in an attempt to mitigate for declines in wild stocks of Pacific salmon (Oncorhynchus spp.), though the conservation benefit of hatcheries is a topic of ongoing debate. Irrespective of conservation benefits, a fundamental question is whether hatcheries will be able to function as they have in the past given anticipated future climate conditions. To begin to answer this question, we developed a deterministic modeling framework to evaluate how climate change may affect hatcheries that rear Pacific salmon. The framework considers the physiological tolerances for each species, incorporates a temperature-driven growth model, and uses two metrics commonly monitored by hatchery managers to determine the impacts of changes in water temperature and availability on hatchery rearing conditions. As a case study, we applied the model to the US Fish and Wildlife Service's Winthrop National Fish Hatchery. We projected that hatchery environmental conditions remained within the general physiological tolerances for Chinook salmon in the 2040s (assuming A1B greenhouse gas emissions scenario), but that warmer water temperatures in summer accelerated juvenile salmon growth. Increased growth during summer coincided with periods when water availability should also be lower, thus increasing the likelihood of physiological stress in juvenile salmon. The identification of these climate sensitivities led to a consideration of potential mitigation strategies such as chilling water, altering rations, or modifying rearing cycles. The framework can be refined with new information, but in its present form, it provides a consistent, repeatable method to assess the vulnerability of hatcheries to predicted climate change.

Divergent immunity and energetic programs in the gills of migratory and resident Oncorhynchus mykiss

Divergent life history strategies occur in steelhead or rainbow trout Oncorhynchus mykiss, and many populations produce both migrant (anadromous fish that move to the ocean after rearing) and resident (do not migrate and remain in fresh water) individuals. Mechanisms leading to each type are only partially understood; while the general tendency of a population is heritable, individual tendency may be plastic, influenced by local environment. Steelhead hatchery programmes aim to mitigate losses in wild stocks by producing trout that will migrate to the ocean and not compete with wild trout for limited freshwater resources. To increase our understanding of gill function in these migratory or resident phenotypes, here we compare gill transcriptome profiles of hatchery-released fish either at the release site (residents) or five river kilometres downstream while still in full fresh water (migrants). To test whether any of these genes can be used as predictive markers for smoltification, we compared these genes between migrant-like and undifferentiated trout while still in the hatchery in a common environment (prerelease). Results confirmed the gradual process of smoltification, and the importance of energetics, gill remodelling and ion transport capacity for migrants. Additionally, residents overexpressed transcripts involved in antiviral defences, potentially for immune surveillance via dendritic cells in the gills. The best smoltification marker candidate was protein s100a4, expression of which was highly correlated with Na(+) , K(+) ATPase (NKA) activity and smolt-like morphology in pre- and postrelease trout gills.

The use of a real-time PCR primer/probe set to observe infectivity of Yersinia ruckeri in Chinook salmon, Oncorhynchus tshawytscha (Walbaum), and steelhead trout, Oncorhynchus mykiss (Walbaum)

Yersinia ruckeri is the causative agent of enteric redmouth disease (ERM), a common pathogen affecting aquaculture facilities and implicated in large losses of cultured fish. Fisheries scientists continue to gain a greater understanding of the disease and the pathogen by investigating methods of identification and pre- and post-infection treatment. In this study, a real-time PCR probe set for Y. ruckeri was developed to detect daily changes in the bacterial load during pathogen challenges. Two species of fish, Chinook salmon, Oncorhynchus tshawytscha, and steelhead trout, Oncorhynchus mykiss, were exposed to two strains of Y. ruckeri (Hag and SC) during bath challenges. A subset of fish was killed daily for 14 days, and the kidney tissue was biopsied to enumerate copies of pathogen DNA per gram of tissue. While Chinook exposed to either the Hag or SC strains exhibited similar pathogen loads, those exposed to the Hag strain displayed higher mortality (∼66%) than fish exposed to the SC strain (∼24% mortality). Steelhead exposed to the Hag strain exhibited a greater pathogen load and higher mortality (∼42%) than those exposed to the SC strain (<1% mortality). Steelhead challenged with either strain showed lower pathogen loads than Chinook. The study illustrates the efficacy of the probe set to enumerate Y. ruckeri bacterial growth in the kidneys of fish. Also, strains of Y. ruckeri display species-specific growth patterns that result in differential mortality and pathogen load.

Physiological condition differentially affects the behavior and survival of two populations of sockeye salmon during their freshwater spawning migration

Recently, a segment of the Adams-Shuswap sockeye salmon (Oncorhynchus nerka) population initiated freshwater migration several weeks earlier than historically recorded, resulting in high mortality rates. The comigrating Chilko population maintained their historic river entry timing and did not experience elevated mortality. To test the hypothesis that population-specific differences in physiological condition would differentially influence behavior and survival when exposed to fisheries capture stress, we physiologically sampled individuals from both populations at the onset of the freshwater phase of their reproductive migration and tracked the remainder of their migrations using radio telemetry. Adams-Shuswap individuals had slower migration rates and were less likely to reach natal subwatersheds relative to Chilko individuals. Metabolic and osmoregulatory impairment was related to mortality for Adams-Shuswap individuals but not for Chilko individuals. Similarly, physiological condition correlated with migration rate for Adams-Shuswap but not Chilko fish. Survival to natal subwatersheds was 1.9 times higher for Chilko relative to Adams-Shuswap, a result that did not emerge until individuals approached natal subwatersheds several days after the stressor was applied. We conclude that physiological condition differentially affects the behavior and survival of these two populations, which may be a consequence of the early-entry phenomenon by a segment of the Adams-Shuswap population.

Mechanisms influencing the timing and success of reproductive migration in a capital breeding semelparous fish species, the sockeye salmon

Two populations of homing sockeye salmon (Oncorhynchus nerka; Adams and Chilko) were intercepted in the marine approaches around the northern and southern ends of Vancouver Island (British Columbia, Canada) en route to a natal river. More than 500 salmon were nonlethally biopsied for blood plasma, gill filament tips, and gross somatic energy (GSE) and were released with either acoustic or radio transmitters. At the time of capture, GSE, body length, and circulating testosterone ([T]) differed between populations, differences that reflected known life-history variations. Within-population analyses showed that in Adams sockeye salmon, plasma glucose ([glu]), lactate ([lactate]), and ion concentrations were higher in the northern approach than in the southern approach, suggesting that the former was more stressful. GSE, [T], and gill Na(+),K(+)-ATPase activities also differed between the two locales, and each varied significantly with Julian date, suggesting seasonality. Despite these relative geographic differences, the timing of river entry and the ability to reach spawning areas were strongly correlated with energetic, reproductive, and osmoregulatory state. Salmon that delayed river entry and reached spawning areas had relatively high GSE and low [T] and gill ATPase. In contrast, salmon that entered the river directly but that ultimately failed to reach spawning areas had lower GSE and higher [T] and gill ATPase, and they also swam at significantly faster rates (failed fish approximately 20.0 km d(-1) vs. successful fish approximately 15.5 km d(-1)). Physiologically, salmon that did not enter the river at all but that presumably died in the marine environment exhibited high stress (plasma [glu] and [lactate]) and ionoregulatory measures (plasma [Na(+)], [Cl(-)], osmolality).

Causes and consequences of voluntary anorexia during the parental care period of wild male smallmouth bass (Micropterus dolomieu)

By definition, parental care behaviors increase offspring survival, and individual fitness, at some cost to the parent. In smallmouth bass (Micropterus dolomieu), parental males provide sole care for the developing brood that includes an increase in activity during brood defense and decreased foraging resulting in a decline in endogenous energy reserves. No mechanisms have been proposed for cessation of voluntary foraging, though regulation of appetite hormones such as ghrelin have been documented to affect feeding behavior in other fishes. We documented baseline fluctuations in plasma ghrelin concentrations across parental care. Plasma ghrelin concentrations were lowest during the early stages of parental care before increasing as the brood developed to independence. Additionally, we performed an intervention experiment whereby plasma ghrelin levels were artificially increased through an injection of rodent ghrelin at the onset of parental care. Despite measuring a significant increase in plasma ghrelin approximately 1 week after injection, we noted no differences in plasma-borne indicators of recent foraging activity indicating that voluntary anorexia is possibly reinforced by receptor insensitivity to appetite hormones. Finally, we assessed the ultimate consequences of foraging during parental care by feeding fish to satiation and measuring post-prandial changes in swimming performance and aggression. Fish fed to satiation showed significant decreases in burst swimming ability and aggressiveness towards potential brood predators. Voluntary anorexia during smallmouth bass parental care is an adaptive behavior that avoids potentially deleterious declines in swimming performance and aggression apparently through a modulation of production and reception of appetite hormones including ghrelin.

The effect of shoreline recreational angling activities on aquatic and riparian habitat within an urban environment: implications for conservation and management

There is growing concern that recreational shoreline angling activity may negatively impact littoral and riparian habitats independent of any direct or indirect influences of fish harvest or fishing mortality through mechanisms such as disturbance (e.g., trampling, erosion) and pollution (e.g., littering). We sampled a suite of aquatic and terrestrial variables (i.e., water quality, aquatic and terrestrial macrophytes, soil compaction, anthropogenic refuse) at 14 high shoreline angling-activity sites (identified by way of interviews with conservation officers and angling clubs) within an urban area (Ottawa, Canada). For each high angling-activity site, a nearby corresponding low angling-activity site was sampled for comparison. We found that the percentage of barren area and soil compaction were greater in areas of high angling activity compared with areas that experienced relatively low angling activity. In addition, terrestrial and aquatic macrophyte density, height, and diversity were lower at high angling-activity sites. Angling- and non-angling-related litter was present in large quantities at each of the high angling-activity sites, and comparatively little litter was found at low angling-activity sites. Collectively, these findings indicate that shoreline angling does alter the riparian environment, contributing to pollution and environmental degradation in areas of high angling intensity. With growing interest in providing urban angling opportunities and in response to increasing interest in developing protected areas and parks, a better understanding of the ecologic impacts of shoreline angling is necessary to address multiuser conflicts, to develop angler outreach and educational materials, and to optimize management of angling effort to maintain ecologic integrity of riparian and aquatic ecosystems.

Effect of water temperature on laboratory swimming performance and natural activity levels of adult largemouth bass

Although locomotory performance in vertebrates is related to fitness, most performance tests are conducted in a laboratory setting, or in a manner that forces the organism to move not of their own volition. Biotelemetry offers the possibility to measure voluntary activity in a natural setting and provides the opportunity to combine laboratory-derived data with field studies on wild fish. In this study, it was found that laboratory- and field-based measurements of swimming performance and voluntary activity resulted in similar general seasonal trends, though each measurement assessed a different swimming type. In the field, all swimming metrics were lower at cooler water temperatures and were lowest during early winter (mean daily activity = 0.016 BL/s; mean voluntary swimming activity = 0.04319 BL/s; maximum swimming speed = 0.17 BL/s). In the laboratory, fish acclimatized to 25.0, 14.0, and 7.5 °C decreased swimming performance (Ucrit) with water temperature (25.0 °C (2.17 BL/s); 14.0 °C (1.69 BL/s); 7.5 °C (1.17 BL/s). Although some species and tissues have been shown to exhibit different degrees of thermal adaptation, these results show that swimming, one of the most important functions in fish, is largely dependent on environmental temperature, at least in largemouth bass ( Micropterus salmoides (Lacepède, 1802)).

Paternal aggression towards a brood predator during parental care in wild smallmouth bass is not correlated with circulating testosterone and cortisol concentrations

Male smallmouth bass (Micropterus dolomieu) provide sole parental care including frequent aggressive actions towards conspecifics and potential brood predators. Failure to defend the brood through continual vigilance results in predation reducing the number of offspring and promoting abandonment by the nesting male. However, little is known about how biochemical and endocrine factors and brood size collectively influence paternal aggression. Behavioral assays were conducted during the egg stage of offspring development by placing a brood predator in a jar on the nest to quantify aggression (number of attacks on the potential brood predator in a minute). To determine the correlates of parental aggression, we temporarily removed fish from their nests and measured circulating levels of testosterone and indicators of the primary (plasma cortisol) and secondary stress response (plasma glucose, Cl(-), Na(+), K(+)) from non-lethal blood samples. While the male was removed from the nest, a snorkeler quantified the size of the brood. Brood size was positively correlated with male aggression. The only biochemical correlate of parental aggression was plasma glucose, which also had a positive relationship with brood size. When the effect of brood size was removed, no biochemical or endocrine factors were predictive of male aggression. Hence, brood value appeared to influence parental aggression independent of biochemical or endocrine status. While several-fold individual differences in aggression towards brood predators were noted, the role of androgens and glucocorticoids in mediating these behaviors is currently not well understood.

Long-term effects of surgically implanted telemetry tags on the nutritional physiology and condition of wild freshwater fish

Little is known about the long-term consequences of surgically implanted telemetry devices on wild fish, as they are rarely recaptured. We used wild largemouth bass Micropterus salmoides as a model to evaluate the long-term impacts of telemetry devices on fish physiology and nutritional condition in a closed freshwater lake where recapture rates were reasonably high. Between 2003 and 2005, 68 fish were surgically implanted with acoustic telemetry devices. Between 2005 and 2008, 17 of the tagged fish were recaptured after carrying a transmitter for 335 to 1402 d. Incision sites were examined, and individuals were non-lethally sampled for blood and measured prior to release. Plasma samples were analysed, and physiological measures of stress (glucose, Na+, Cl-, K+), tissue damage (aspartate aminotransferase), and nutritional status (Ca++, Mg+, phosphorus, total protein, triglycerides, cholesterol) were compared between fish carrying transmitters and temporally- and size-matched controls. Of the 17 recaptured fish, 3 retained at least 1 of the absorbable monofilament sutures and showed localised signs of inflammation and infection despite an elapsed time of 362 d post surgery. Five individuals showed signs of pressure necrosis at the incision site despite the fact that the transmitters averaged only 1.89% (range: 0.84 to 3.59%) of the body mass. There was no difference in any physiological parameter measured between the 2 groups, or within the telemetered fish, in relation to days since tagging or condition of the incision site. In summary, transmitter implantation was not correlated with any long-term change in any of the physiological parameters investigated. However, there is opportunity for additional research to optimise surgical techniques, guidelines on transmitter mass to body mass ratios, and choice of suture material to enhance the healing and long-term welfare of tagged fish.

Individual variation in migration speed of upriver-migrating sockeye salmon in the Fraser River in relation to their physiological and energetic status at marine approach

Little research has examined individual variation in migration speeds of Pacific salmon (Oncorhynchus spp.) in natural river systems or attempted to link migratory behavior with physiological and energetic status on a large spatial scale in the wild. As a model, we used three stocks of summer-run sockeye salmon (Oncorhynchus nerka) from the Fraser River watershed, British Columbia, to test the hypothesis that individual variation in migration speed is determined by a combination of environmental factors (i.e., water temperature), intrinsic biological differences (sex and population), and physiological and energetic condition. Before the freshwater portion of the migration, sockeye salmon (Quesnel, Chilcotin, and Nechako stock complexes) were captured in Johnstone Strait ( approximately 215 km from river entry), gastrically implanted with radio transmitters, and sampled for blood, gill tissue, and energetic status before release. Analyses focused solely on individuals that successfully reached natal subwatersheds. Migration speeds were assessed by an extensive radiotelemetry array. Individuals from the stock complex that migrated the longest distance (Nechako) traveled at speeds slower than those of other stock complexes. Females traveled slower than males. An elevated energetic status of fish in the ocean was negatively correlated with migration speed in most river segments. During the transition from the ocean to the river, migration speed was negatively correlated with mean maximum water temperature; however, for the majority of river segments, it was positively correlated with migration speed. Physiological status measured in the ocean did not explain among-individual variability in river migration speeds. Collectively, these findings suggest that there could be extensive variation in migration behavior among individuals, sexes, and populations and that physiological condition in the ocean explained little of this variation relative to in-river environmental conditions and energetic status. Interestingly, individual fish generally retained their rank in swimming speed across different segments, except when transiting a challenging canyon midway during the migration.

Physiological disturbance and recovery dynamics of bonefish (Albula vulpes), a tropical marine fish, in response to variable exercise and exposure to air

Current understanding of the stress response in fishes has largely come from studies of freshwater-adapted salmonids, with proportionately few comparative studies having examined marine fishes. The current study sought to quantify the magnitude of physiological disturbances, recovery dynamics, and post-exercise behaviour in bonefish (Albula vulpes; a tropical marine fish) exposed to several different exercise and air exposure regimens. Results showed that metabolic disturbances (lactate production, hyperglycemia) increased following exercise and exposure to air, and that the magnitude of metabolic disturbance was proportional to the duration of the stressful event. Fish required between 2-4 h to return to resting values. Exercise and exposure to air also resulted in significant increases in plasma Ca2+, Cl- and Na+, but the magnitude of these ionic changes did not vary with exercise or exposure to air duration and required over 4-h to return to baseline levels. Mortality following exercise was observed only for fish that had been exposed to air for 3 min and not in fish that had been exposed to air for 1 min. Together, results from this study provide a physiological basis for management strategies that can improve the post-release survival of bonefish that have been caught during a catch-and-release angling event.

Do Catch-and-Release guidelines from state and provincial fisheries agencies in North America conform to scientifically based best practices?

Many recreational anglers practice catch-and-release angling, where fish are returned to the water with the presumption that they will survive. However, not all fish survive, and those that do often experience sublethal consequences including injury and stress. There is compelling scientific evidence that angler behavior and gear choice can affect the success of catch-and-release as a management and conservation strategy. Because anglers often look to government natural resource agencies for guidance on how to handle and release fish properly, there is a need to assess whether their outreach materials are readily accessible and provide the necessary and correct information on the subject. Therefore, on-line catch-and-release guidelines developed by state and provincial natural resource agencies across North America were evaluated to determine whether their guidelines were consistent with the best available scientific information. This analysis revealed that there was immense variation in the depth and breadth of coverage among jurisdictions. Agency guidelines contradicted one another in several areas including air exposure, angling in deep water, venting trapped gases, and resuscitation. In many cases, the guidelines failed to provide sufficient direction to actually be of use to anglers or provide direction consistent with contemporary scientific literature. This analysis will assist with developing outreach materials that promote sustainable recreational fisheries and in maintaining the welfare status of individual fish.

Effects of a dietary Aspergillus oryzae extract containing α-amylase activity on performance and carcass characteristics of finishing beef cattle

Three experiments were conducted to examine the effects of an Aspergillus oryzae extract containing alpha-amylase activity on performance and carcass characteristics of finishing beef cattle. In Exp. 1, 120 crossbred steers were used in a randomized complete block design to evaluate the effects of roughage source (alfalfa hay vs. cottonseed hulls) and supplemental alpha-amylase at 950 dextrinizing units (DU)/kg of DM. Significant roughage source x alpha-amylase interactions (P < 0.05) were observed for performance. In steers fed cottonseed hulls, supplemental alpha-amylase increased ADG through d 28 and 112 and tended (P < 0.15) to increase ADG in all other periods. The increases in ADG were related to increased DMI and efficiency of gain during the initial 28-d period but were primarily related to increased DMI as the feeding period progressed. Supplemental alpha-amylase increased (P = 0.02) the LM area across both roughage sources. In Exp. 2, 96 crossbred heifers were used in a randomized complete block design with a 2 x 3 factorial arrangement of treatments to evaluate the effects of corn processing (dry cracked vs. high moisture) and supplemental alpha-amylase concentration (0, 580, or 1,160 DU/kg of DM). Alpha-amylase supplementation increased DMI (P = 0.05) and ADG (P = 0.03) during the initial 28 d on feed and carcass-adjusted ADG (P = 0.04) across corn processing methods. Longissimus muscle area was greatest (quadratic effect, P = 0.04), and yield grade was least (quadratic effect, P = 0.02) in heifers fed 580 DU of alpha-amylase/kg of DM across corn processing methods. In Exp. 3, 56 crossbred steers were used in a randomized complete block design to evaluate the effects of supplemental alpha-amylase (930 DU/kg of DM) on performance when DMI was restricted to yield a programmed ADG. Alpha-amylase supplementation did not affect performance when DMI was restricted. We conclude that dietary alpha-amylase supplementation of finishing beef diets may result in increased ADG through increased DMI under certain dietary conditions and that further research is warranted to explain its mode of action and interactions with dietary ingredients.

Long-term effects of low histidine intake on men

The purpose of this 85-day study was to investigate the long-term effects of histidine depletion on nitrogen utilization in young adult men. A low nitrogen (6.3 g/day), low histidine (10 mg/day) amino acid diet was fed to seven men for 8 weeks. Mean nitrogen balance became negative at the end of the 8-week period. Free histidine in postabsorptive plasma and 24-hour urine decreased significantly during the first 2 weeks of the depletion and remained low and constant for the remaining 6 weeks. Hemoglobin concentration decreased somewhat, and serum iron concentration increased significantly during histidine depletion. Lean body mass, urinary N'-methylhistidine and total creatinine did not change significantly. On addition of histidine to the low histidine diet for 2 weeks, nitrogen retention became positive, plasma and urinary histidine returned to initial values, serum iron fell, and hemoglobin concentration slowly increased. These parameters remained unchanged in two control men fed the same diet supplemented with histidine (1.05 g/day) for 8 weeks. The results suggest that histidine is indispensable for young men consuming a low nitrogen diet.

Effects of dietary histidine and arginine on nitrogen retention of men

Effects of dietary histidine and arginine on nitrogen retention were compared in six young men consuming for 1 week, each of six semipurified diets containing eight indispensable amino acids proportioned as in casein and 6.3 g nitrogen daily. Nonspecific nitrogen was either A) a mixture of six dispensable amino acids and arginine (diet 1) or arginine and histidine (diet 2) in casein proportions, or B) an isonitrogenous mixture of glycine and diammonium citrate alone (diet 3), with histidine (diet 4), arginine (diet 5), or histidine and arginine (diet 6). Nitrogen retention was significantly greater when the nonspecific nitrogen source was dispensable amino acids, arginine and histidine (diet 2) than when it was glycine and diammonium citrate (diet 3). mean balances were positive only when diets contained histidine (diets 2, 4, and 6). Histidine with arginine (diets 2 and 6) significantly improved nitrogen retention compared to arginine alone, but the balance, although positive, was not significantly improved when histidine was fed without arginine (diet 4). Urinary urea nitrogen confirmed these data. Indicators of erythrocyte status, plasma enzyme activities and proteins, and creatinine clearance were unaffected by diet. In summary, histidine supplementation of the low nitrogen diet improved total nitrogen utilization when arginine was present in the diet.

Effect of bile salts on hepatic phosphatidylcholine synthesis and transport into rat bile

The effect of transport of micelle-forming and non-micelle-forming conjugated bile salts on phosphatidylcholine synthesis and transport into bile was studied in the ex vivo perfused rat liver. Single additions of sodium taurocholate, a good micelle-forming conjugated bile salt, caused an increase in bile flow associated with increased phosphatidylcholine and taurocholate concentration. The specific activity of phosphatidylcholine with respect to incorporated [1,2-(14)C]choline and [(3)H]methyl of l-[Me-(3)H]methionine was not significantly altered by the increased transport of phosphatidylcholine. The data suggested that bile phosphatidylcholine is synthesized to a great extent, although not exclusively, by phosphorylcholine glyceride transferase. Single additions of the glycine conjugate of dehydrocholate, a poor micelle-forming bile salt, caused an increase in bile flow comparable to that seen with sodium taurocholate administration. However, the concentrations of phosphatidylcholine in bile decreased. Thin-layer and gas-liquid chromatographic analyses of bile secreted before and after glycodehydrocholate administration revealed no significant increase in bile salt secretion other than the administered glycodehydrocholate. Investigations utilizing radiochemically pure [(14)C]glycine dehydrocholate revealed that increased bile flow after [(14)C]-glycine dehydrocholate administration occurs concomitantly with the secretion of 75-95% of the administered [(14)C]glycine dehydrocholate as a single peak into bile. Thus the increased bile flow without increased phosphatidylcholine concentration noted after glycodehydrocholate administration is due to transport of an intact, nonmetabolized, conjugated bile salt with poor micelle-forming properties. The data indicate that the formation of a bile salt-phosphatidylcholine micelle is responsible for phosphatidylcholine transport into bile.