Dirk A. Algera

Understanding the individual to implement the ecosystem approach to fisheries management

Variation of physiological and behavioural traits among individuals within a population is an important factor for ecosystem function, and correspondingly, ecosystem approaches to fisheries management (EAFM). Here, we review instances of individual level variation in fishes with practical guidance for EAFM.

Stress, nutrition and parental care in a teleost fish: Exploring mechanisms with supplemental feeding and cortisol manipulation

ABSTRACT Parental care is an essential life-history component of reproduction for many animal species, and it entails a suite of behavioural and physiological investments to enhance offspring survival. These investments can incur costs to the parent, reducing their energetic and physiological condition, future reproductive capabilities and survival. In fishes, relatively few studies have focused on how these physiological costs are mediated. Male smallmouth bass provide parental care for developing offspring until the brood reaches independence. During this energetically demanding life stage, males cease active foraging as they vigorously defend their offspring. Experimental manipulation of cortisol levels (via implantation) and food (via supplemental feeding) in parental males was used to investigate the fitness consequences of parental care. Improving the nutritional condition of nest-guarding males increased their reproductive success by reducing premature nest abandonment. However, supplemental feeding and cortisol treatment had no effect on parental care behaviours. Cortisol treatment reduced plasma lymphocyte numbers, but increased neutrophil and monocyte concentrations, indicating a shift in immune function. Supplemental feeding improved the physiological condition of parental fish by reducing the accumulation of oxidative injury. Specifically, supplemental feeding reduced the formation of 8-hydroxy-2′-deoxyguanosine (8-OHdG) on DNA nucleotides. Increasing the nutritional condition of parental fish can reduce the physiological cost associated with intensive parental activity and improve overall reproductive success, illustrating the importance of nutritional condition as a key modulator of parental fitness. Summary: Stress and nutritional condition are key modulators of physiological condition and reproductive success in a parental teleost fish.

Parental Care in a Stressful World: Experimentally Elevated Cortisol and Brood Size Manipulation Influence Nest Success Probability and Nest-Tending Behavior in a Wild Teleost Fish*

Parental care is an advantageous reproductive behavior, as the fitness of the caregiver is increased through improving the chances of its offspring’s survival. Parental care occurs in a variety of teleost fishes. The body size of parental fish and the size of their brood can affect nest abandonment decisions, where compared with smaller fish with smaller broods, larger fish with larger broods typically invest more energy into reproductive events because they have less future reproductive potential. Although essential for basal metabolism and body maintenance functions, when glucocorticoid hormones (e.g., cortisol) are chronically elevated, as can occur during stress, fish may experience impairments in behavior and immune function, leading to compromised health and condition. Anthropogenic stressors during parental care can lead to elevated stress, therefore making it necessary to understand how stress influences an already-challenging period. Using smallmouth bass as a model, a gradient of body sizes, and experimentally manipulated brood size (i.e., reducing large broods and supplementing small broods) and cortisol levels (i.e., elevated via slow-release intraperitoneal cocoa butter implants containing cortisol versus controls), we tested the hypothesis that the reproductive success and parental care behaviors (i.e., aggression, nest tending) of nest-guarding male smallmouth bass are influenced by parental body size, brood size, and cortisol level. Overall, there was a relationship between cortisol treatment and nest success in which larger fish exhibited lower success when cortisol levels were elevated. Brood size had a significant effect on fish-tending behavior, independent of cortisol level and body size. Lending partial support to our hypothesis, the results of this study indicate that the reproductive success of guarding male smallmouth bass is influenced by cortisol level and that tending behavior is affected by brood size.

Consequences of Different Types of Littoral Zone Light Pollution on the Parental Care Behaviour of a Freshwater Teleost Fish

Ecological light pollution occurs when artificial lights disrupt the natural regimes of individual organisms or their ecosystems. Increasing development of shoreline habitats leads to increased light pollution (e.g., from cottages, docks, automobile traffic), which could impact the ecology of littoral zones of lakes and rivers. Smallmouth bass (Micropterus dolomieu) engage in sole paternal care, guarding their nest continually, day and night, to protect their developing offspring. Any alterations to their behaviour—either directly because of the response to light or indirectly due to changes in nest predator activity and associated response of the bass—could lead to increased energetic demands for fish that have a fixed energy budget and ultimately reduce reproductive success. To examine this issue, tri-axial accelerometer biologgers were externally attached to nesting smallmouth bass during the egg stage to determine whether light pollution (i.e., dock lights with low levels of continuous light and spotlights with high intensity irregular light simulating automobile traffic) altered behaviour of nesting males relative to control fish. Our study revealed that both types of light pollution increased overall bass activity level compared with the control group. The intermittent light treatment group had the highest activity and exhibited large fluctuations between night and day activity levels. Fish in the continual light treatment group displayed statistically higher activity than the control fish but showed limited fluctuations between day and night activity levels. Our results suggest that continuous or intermittent light sources, common in shoreline habitats that have been developed, have the potential to alter the behaviour and thus energy use of nest-guarding fish. This study contributes to the growing body of literature on the ecological consequences of light pollution in aquatic ecosystems.

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.

An experimental test of in-season homing mechanisms used by nest-guarding male Largemouth Bass following displacement.

Through manipulations of sensory functions, researchers have evaluated the various mechanisms by which migratory fish, particularly in lotic systems, locate natal spawning grounds. Comparatively less work has occurred on the ways by which fish in lentic systems locate spawning sites, and more specifically, the ways by which displaced fish in these systems locate their broods post spawning. The primary goal of this research was to determine the sensory mechanisms used by nesting, male Largemouth Bass to navigate back to their brood following displacement. This was accomplished by comparing the ability of visually impaired, olfactory impaired and geomagnetically impaired individuals to return to their nests after a 200 m displacement, relative to control males. All treatments were designed to be temporary and harmless. We analyzed the data using a generalized linear mixed model, and found that the probability of an olfactory impaired individual returning to his nest within a given time interval was significantly lower than the probability of a geomagnetically impaired individual returning. Overall, it appears as though olfaction is the most important sensory mechanism used for homing in Largemouth Bass.

Cortisol treatment affects locomotor activity and swimming behaviour of male smallmouth bass engaged in paternal care: A field study using acceleration biologgers

Paternal care, where the male provides sole care for the developing brood, is a common form of reproductive investment among teleost fish and ubiquitous in the Centrarchidae family. Throughout the parental care period, nesting males expend energy in a variety of swimming behaviours, including routine and burst swimming, vigilantly monitoring the nest area and protecting the brood from predators. Parental care is an energetically demanding period, which is presumably made even more difficult if fish are exposed to additional challenges such as those arising from human disturbance, resulting in activation of the hypothalamic-pituitary-interrenal axis (i.e., elevation of cortisol). To study this situation, we examined the effects of experimental manipulation of the stress hormone cortisol on locomotor activity and behaviour of nest guarding male smallmouth bass (Micropterus dolomieu). We exogenously elevated circulating cortisol levels (via intracoelomic implants) and attached tri-axial accelerometers to wild smallmouth bass for three days. During the recovery period (i.e., ≤4h post-release), cortisol-treated fish exhibited significantly reduced locomotor activity and performed significantly less burst and routine swimming relative to control fish, indicating cortisol uptake was rapid, as were the associated behavioural responses. Post-recovery (i.e., >4h post-release), fish with high cortisol exhibited lower locomotor activity and reduced routine swimming relative to controls. Fish were less active and reduced routine and burst swimming at night compared to daylight hours, an effect independent of cortisol treatment. Collectively, our results suggest that cortisol treatment (as a proxy for anthropogenic disturbance and stress) contributed to altered behaviour, and consequently cortisol-treated males decreased parental investment in their brood, which could have potential fitness implications.

What are the consequences of fish entrainment and impingement associated with hydroelectric dams on fish productivity? A systematic review protocol

BackgroundThis systematic review will address the need for a better understanding of the impacts of fish entrainment and impingement associated with hydroelectric dams on fish productivity in freshwater temperate environments. As the number of dams continues to increase worldwide, so too has concerns for their effects on fish populations. Fish injury and mortality at hydroelectric facilities may have serious consequences for fish populations, which are generally the result of three main sources: (1) fish passage through hydroelectric facilities (i.e., turbines, spillways, sluiceways, and other passage routes) during downstream migration for migratory fish; (2) the entrainment of resident fish; and (3) the impingement of fish (migratory or resident) against screens/trash racks. Most studies on the impacts of entrainment and impingement at hydroelectric facilities on fish have primarily focused on: (1) how fish injury and mortality occurs; and (2) evaluations of the effectiveness of various management strategies used to mitigate harm during downstream passage. Given the contributions of migratory and resident adults and juveniles to fish production, a necessary extension is to evaluate the impacts of fish injury and mortality from hydropower dam entrainment and impingement on fish productivity. Therefore, to ensure the sustainability of fishes dependent on our freshwater ecosystems, a better understanding of the impacts of fish entrainment and impingement associated with hydroelectric dams on fish productivity is needed.MethodsThis systematic review will search for, compile, summarize and synthesize evidence on the impacts of fish entrainment and impingement associated with hydroelectric dams on fish productivity in freshwater temperate environments. Considered studies will include (but not be limited to): (1) those that report a metric related to mortality and injury as an indication of the effect on fish productivity; (2) the change in a metric related to mortality and injury relative to an appropriate control; and (3) articles that scale-up the evaluation to include some estimate of a change in a component of fish productivity (e.g., articles that include an estimate of fish loss from the population due to entrainment/impingement by comparing a metric related to mortality or injury to an estimate of population size or biomass). Only studies where the causal relationship between intervention and outcome is made clear to allow for the effects of entrainment and impingement to be isolated from other potential impacts of hydroelectric power production (e.g., barriers to migration and/or habitat degradation), will be included. The review will use public search engines and specialist websites, and will include both primary and grey literature. Potential effect modifiers will be identified to obtain a better understanding of the factors that are associated with variation in effects among studies, given differences in: (1) site-specific factors (e.g., turbine type, size, power output); (2) methodologies and study designs used to assess impacts; and (3) biological factors (e.g., fish life history stage, body size and morphology). Study quality will be assessed to allow for critical evaluation, including study design, confounding factors and statistical analysis. Data will be compiled into a narrative synthesis and a meta-analysis will be conducted where data availability and quality allow.