Stressor-response (SR) functions quantify ecological responses to natural environmental variation or anthropogenic stressors. They are also core drivers of cumulative effects (CE) models, which are ...increasingly recognized as essential management tools to grapple with the diffuse footprint of human impacts. Here, we provide a process framework for the identification, development, and integration of SR functions into CE models, and highlight their consequential properties, behaviour, criteria for selecting appropriate stressors and responses, and general approaches for deriving them. Management objectives (and causal effect pathways) will determine the ultimate stressor and target response variables of interest (i.e., individual growth/survival, population size, community structure, ecosystem processes), but data availability will constrain whether proxies need to be used for the target stressor or response variables. Available data and confidence in underlying mechanisms will determine whether empirical or mechanistic (theoretical) SR functions are optimal. Uncertainty in underlying SR functions is often the primary source of error in CE modelling, and monitoring outcomes through adaptive management to iteratively refine parameterization of SR functions is a key element of model application. Dealing with stressor interactions is an additional challenge, and in the absence of known or suspected interaction mechanisms, controlling main effects should remain the primary focus. Indicators of suspected interaction presence (i.e., much larger or smaller responses to stressor reduction than expected during monitoring) should be confirmed through adaptive management cycles or targeted stressor manipulations. Where possible, management decisions should selectively take advantage of interactions to strategically mitigate stressor impacts (i.e., by using antagonisms to suppress stressor impacts, and by using synergisms to efficiently reduce them).
Display omitted
•Cumulative effects (CE) modelling is a priority for conservation and management.•Stressor-response (SR) functions are core drivers that modulate the severity of CE.•We review how to derive and integrate SR functions into CE models.•We expand an existing CE process framework to include SR function attributes.•This framework is intended to accelerate the adaptive management process.
Advisory Editor profile: Eva Enders Docker, Margaret F.; Enders, Eva C.
Environmental biology of fishes,
10/2023, Letnik:
106, Številka:
10
Journal Article
Animal metabolic rate is variable and may be affected by endogenous and exogenous factors, but such relationships remain poorly understood in many primitive fishes, including members of the family ...Acipenseridae (sturgeons). Using juvenile lake sturgeon (Acipenser fulvescens), the objective of this study was to test four hypotheses: 1) A. fulvescens exhibits a circadian rhythm influencing metabolic rate and behaviour; 2) A. fulvescens has the capacity to regulate metabolic rate when exposed to environmental hypoxia; 3) measurements of forced maximum metabolic rate (MMR(F)) are repeatable in individual fish; and 4) MMR(F) correlates positively with spontaneous maximum metabolic rate (MMR(S)). Metabolic rates were measured using intermittent flow respirometry, and a standard chase protocol was employed to elicit MMR(F). Trials lasting 24 h were used to measure standard metabolic rate (SMR) and MMR(S). Repeatability and correlations between MMR(F) and MMR(S) were analyzed using residual body mass corrected values. Results revealed that A. fulvescens exhibit a circadian rhythm in metabolic rate, with metabolism peaking at dawn. SMR was unaffected by hypoxia (30% air saturation (O(2sat))), demonstrating oxygen regulation. In contrast, MMR(F) was affected by hypoxia and decreased across the range from 100% O(2sat) to 70% O(2sat). MMR(F) was repeatable in individual fish, and MMR(F) correlated positively with MMR(S), but the relationships between MMR(F) and MMR(S) were only revealed in fish exposed to hypoxia or 24 h constant light (i.e. environmental stressor). Our study provides evidence that the physiology of A. fulvescens is influenced by a circadian rhythm and suggests that A. fulvescens is an oxygen regulator, like most teleost fish. Finally, metabolic repeatability and positive correlations between MMR(F) and MMR(S) support the conjecture that MMR(F) represents a measure of organism performance that could be a target of natural selection.
Metabolic costs are central to individual energy budgets, making estimates of metabolic rate vital to understanding how an organism interacts with its environment as well as the role of species in ...their ecosystem. Despite the ecological and commercial importance of fishes, there are currently no widely adopted means of measuring field metabolic rate in fishes. The lack of recognized methods is in part due to the logistical difficulties of measuring metabolic rates in free swimming fishes. However, further development and refinement of techniques applicable for field-based studies on free swimming animals would greatly enhance the capacity to study fish under environmentally relevant conditions. In an effort to foster discussion in this area, from field ecologists to biochemists alike, we review aspects of energy metabolism and give details on approaches that have been used to estimate energetic parameters in fishes. In some cases, the techniques have been applied to field conditions; while in others, the methods have been primarily used on laboratory held fishes but should be applicable, with validation, to fishes in their natural environment. Limitations, experimental considerations and caveats of these measurements and the study of metabolism in wild fishes in general are also discussed. Potential novel approaches to FMR estimates are also presented for consideration. The innovation of methods for measuring field metabolic rate in free-ranging wild fish would revolutionize the study of physiological ecology.
We assessed the metabolic response of juvenile Atlantic salmon (Salmo salar; JAS) originating from two rivers with different natural thermal regimes to different acclimation temperature (15 or 20 °C) ...and diel temperature fluctuation (constant: ±0.5 °C; fluctuating: ±2.5 °C). Diel temperature fluctuation (15 ± 2.5 °C) near the thermal optimum (16 °C) for the species did not influence standard metabolic rate (SMR) compared with JAS acclimated to a constant temperature of 15 °C. Diel temperature fluctuation at 20 ± 2.5 °C increased SMR of JAS from the warmer river by 33.7% compared with the same fish acclimated to a constant temperature of 20 °C. SMR of JAS from the cooler river held at fluctuating conditions had SMR that were 8% lower than SMR at constant conditions. The results suggest that the mean temperature to which JAS is exposed may affect their responses to diel temperature fluctuation and that this response may vary between populations originating from rivers with different natural thermal regimes. Results were used to develop the first empirical SMR model for JAS subjected to diel temperature fluctuation using fish mass (3–36 g wet) and temperature (12.5–22.5 °C) as explanatory variables.
The current understanding of the effects of turbulence on the swimming performance of fish is primarily derived from laboratory experiments under pressurised flow swim tunnels and open‐channel flow ...facilities. These studies have produced valuable information on the swimming mechanics and behaviour of fish in turbulent flow. However, laboratory studies have limited representation of the flows fish experience in nature. The flow structure in rivers is imparted primarily by the highly heterogeneous nonuniform bed, and the flow is generally much more complex than in laboratory experiments. The goal of the current work is to direct future laboratory and field studies to adopt a common framework that will shape the integration of both approaches. This article outlines four characteristics of turbulent flow, which we suggest should be evaluated when generalising results from fish turbulent studies in both the laboratory and the field. The framework is based on four turbulence characteristics that are summarised under the acronym IPOS: intensity, periodicity, orientation and scale.
Within Salmonidae, spawning and rearing in brackish water is rare; however, brackish-water resident lake trout (
Salvelinus namaycush
) have recently been documented in the Arctic. Additionally, ...early rearing in brackish-water environments increased the fish’s ability to ionoregulate in elevated salinities. Here, we examined the impact of a freshwater (FWR, 0 ppt) or brackish-water (BWR, 5 ppt) rearing environment on salinity preference in lake trout using a dynamic choice experiment. We observed significant differences in salinity preference between our treatments suggesting the importance of early environment in shaping salinity preference. Contrary to our predictions, FWR lake trout selected higher salinity (17.3 ppt) compared to BWR fish (4.8 ppt). Four of the seven FWR fish had preferred salinities near 30 ppt, which is considered physiologically challenging and potentially lethal for lake trout based on direct transfer experiments. Thus, heightened FWR salinity preference might not be a true preference but rather due to a reduced ability to sense differences in salinity, and a result of chance as mean preferred salinity was near half that of the upper and lower thresholds, and variance was larger. Selection of lower salinity by BWR fish suggests that the ability to sense and select different salinities is present in lake trout as a species and appears to be linked to difference in early rearing at elevated salinities.
The physiology and behaviour of fish are strongly affected by ambient water temperature. Physiological traits related to metabolism, such as aerobic scope (AS), can be measured across temperature ...gradients, and the resulting performance curve reflects the thermal niche that fish can occupy. We measured AS of westslope cutthroat trout (Oncorhynchus clarkii lewisi) at 5,10,15, 20, and 22degreesC and compared temperature preference (T.sub.pref) of the species with non-native brook trout (Salvelinusfontinalis), brown trout (Salmo trutta), and rainbow trout (Oncorhynchus mykiss). Intermittent-flow respirometry experiments demonstrated that metabolic performance of westslope cutthroat trout was optimal at ~15degreesC and decreased substantially beyond this temperature, until lethal temperatures at ~25degreesC. Adjusted T.sub.pref across species were comparatively high, ranging from 17.8 to 19.9degreesC, with the highest T.sub.pref observed for westslope cutthroat trout. Results suggest that although westslope cutthroat trout is considered a cold-water species, they do not prefer or perform as well in cold water (less than or equal to10degreesC) and thus can occupy a warmer thermal niche than previously thought. The metabolic performance curve (AS) can be used to develop species-specific thermal criteria to delineate important thermal habitats and guide conservation and recovery actions for westslope cutthroat trout.
Understanding how metabolic costs change in relation to increasing temperature under future climate changes is important to predict how ectotherms will be affected across the globe. In fish, whole ...body respiration is traditionally used to estimate aerobic performance via an organism’s minimum and maximum oxygen consumption rates. However, mitochondria play a crucial role in the aerobic cascade and may be a useful surrogate of aerobic performance. To test whether whole body oxygen consumption and mitochondrial capacity are correlated, we estimated whole body metabolic and mitochondrial respiration rates (using permeabilized red muscle fibres) in brook trout ( Salvelinus fontinalis (Mitchill, 1814)) at 10, 15, and 20 °C. Standard metabolic rate increased with acclimation temperature, while maximum rates were less sensitive. All mitochondrial respiration rates increased with acclimation temperature, suggesting that red muscle mitochondrial preparations may correlate to the minimal metabolic demands in this species. When expressed as relative rates of electron flow, the red muscle fibres showed no effect of temperature on mitochondrial coupling efficiency. However, there was a pattern of declining capacity to augment respiration via complex II with increasing temperature with a concomitant increase in the capacity of the phosphorylating system relative to maximal rates of mitochondrial electron flow.
Acoustic telemetry studies have frequently prioritized linear configurations of hydrophone receivers, such as perpendicular from shorelines or across rivers, to detect the presence of tagged aquatic ...animals. This approach introduces unknown bias when receivers are stationed for convenience at geographic bottlenecks (e.g. at the mouth of an embayment or between islands) as opposed to deployments following a statistical sampling design.
We evaluated two‐dimensional acoustic receiver arrays (grids: receivers spread uniformly across space) as an alternative approach to provide estimates of survival, movement and habitat use. Performance of variably spaced receiver grids (5–25 km spacing) was evaluated by simulating (1) animal tracks as correlated random walks (speed: 0.1–0.9 m/s; turning angle SD: 5–30°); (2) variable tag transmission intervals along each track (nominal delay: 15–300 s); and (3) probability of detection of each transmission based on logistic detection range curves (mid‐point: 200–1,500 m). From simulations, we quantified (i) time between successive detections on any receiver (detection time), (ii) time between successive detections on different receivers (transit time), and (iii) distance between successive detections on different receivers (transit distance).
In the most restrictive detection range scenario (200 m), the 95th percentile of transit time was 3.2 days at 5 km, 5.7 days at 7 km and 15.2 days at 25 km grid spacing; for the 1,500 m detection range scenario, it was 0.1 days at 5 km, 0.5 days at 7 km and 10.8 days at 25 km. These values represented upper bounds on the expected maximum time that an animal could go undetected. Comparison of the simulations with pilot studies on three fishes (walleye Sander vitreus, common carp Cyprinus carpio and channel catfish Ictalurus punctatus) from two independent large lake ecosystems (lakes Erie and Winnipeg) revealed shorter detection and transit times than what simulations predicted.
By spreading effort uniformly across space, grids can improve understanding of fish migration over the commonly employed receiver line approach, but at increased time cost for maintaining grids.
PDF
