Evaluating the effect of dorsal muscle biopsies on adult Atlantic salmon growth and marine return rates

Atlantic cod individual spatial behaviour and stable isotope associations in a no-take marine reserve

Foraging is a behavioural process and, therefore, individual behaviour and diet are theorized to covary. However, few comparisons of individual behaviour type and diet exist in the wild. We tested whether behaviour type and diet covary in a protected population of Atlantic cod, Gadus morhua. Working in a no-take marine reserve, we could collect data on natural behavioural variation and diet choice with minimal anthropogenic disturbance. We inferred behaviour using acoustic telemetry and diet from stable isotope compositions (expressed as δ13 C and δ15 N values). We further investigated whether behaviour and diet could have survival costs. We found cod with shorter diel vertical migration distances fed at higher trophic levels. Cod δ13 C and δ15 N values scaled positively with body size. Neither behaviour nor diet predicted survival, indicating phenotypic diversity is maintained without survival costs for cod in a protected ecosystem. The links between diet and diel vertical migration highlight that future work is needed to understand whether the shifts in this behaviour during environmental change (e.g. fishing or climate), could lead to trophic cascades.

Nonlethal detection of PFAS bioaccumulation and biomagnification within fishes in an urban- and wastewater-dominant Great Lakes watershed

Per- and polyfluoroalkyl substances (PFAS) are synthetic endocrine disruptors that are particularly stable and pervasive due to strong carbon-fluorine bonds. They are known to bioaccumulate in protein-rich tissues of fish, and most cannot be eliminated with cooking. Despite studies linking PFAS to adverse health outcomes, there is a lack of international regulations of PFAS as a hazardous material. To investigate PFAS in an aquatic food web and the potential human health implications, we analyzed the concentrations of 40 PFAS from muscle biopsy and serum samples of fish representing different trophic levels along the Lake Huron - Lake Erie Corridor. In Summer (2021), walleye (Sander vitreus; WAE), yellow perch (Perca flavescens; YEP) and round gobies (Neogobius melanostomus; ROG) were collected for analysis from the Detroit River (contaminated site) and St. Clair River (reference site). Eight PFAS congeners were detected in muscle and 15 congeners in serum, leading to the novel detection in Great Lakes fish of 7:3 FTCA in muscle and PFHpS, PFNS, MeFOSAA, and EtFOSAA in serum. PFOS was detected in 100% of muscle and serum pools across all species at concentrations lower than those associated with fish toxicity. Muscle PFOS concentration in DR WAE fell under the 8 meals per month (>13 ng-19 ng) fish consumption advisory according to the State of Michigan. Log bioaccumulation factor was significantly different (p = 0.01) among species in DR, driven by higher log BAF for WAE (3.8 ± 0.1) compared to ROG (3.2± 0.02). Biomagnification factor greater than 1 for all species in both rivers indicates that PFOS is biomagnifying in SCR and DR food webs. Successful detection and quantification of PFAS in the muscle and serum of three fish species demonstrates the potential for using this nonlethal sampling method to monitor PFAS and better understand ecological and human health impacts of PFAS exposure.

Non-Lethal Sampling Supports Integrative Movement Research in Freshwater Fish

Freshwater ecosystems and fishes are enormous resources for human uses and biodiversity worldwide. However, anthropogenic climate change and factors such as dams and environmental contaminants threaten these freshwater systems. One way that researchers can address conservation issues in freshwater fishes is via integrative non-lethal movement research. We review different methods for studying movement, such as with acoustic telemetry. Methods for connecting movement and physiology are then reviewed, by using non-lethal tissue biopsies to assay environmental contaminants, isotope composition, protein metabolism, and gene expression. Methods for connecting movement and genetics are reviewed as well, such as by using population genetics or quantitative genetics and genome-wide association studies. We present further considerations for collecting molecular data, the ethical foundations of non-lethal sampling, integrative approaches to research, and management decisions. Ultimately, we argue that non-lethal sampling is effective for conducting integrative, movement-oriented research in freshwater fishes. This research has the potential for addressing critical issues in freshwater systems in the future.

Life-history strategies in salmonids: the role of physiology and its consequences

Salmonids are some of the most widely studied species of fish worldwide. They span freshwater rivers and lakes to fjords and oceans; they include short- and long-distance anadromous migrants, as well as partially migratory and non-migratory populations; and exhibit both semelparous and iteroparous reproduction. Salmonid life-history strategies represent some of the most diverse on the planet. For this reason, salmonids provide an especially interesting model to study the drivers of these different life-history pathways. Over the past few decades, numerous studies and reviews have been published, although most have focused on ultimate considerations where expected reproductive success of different developmental or life-history strategies are compared. Those that considered proximate causes generally focused on genetics or the environment, with less consideration of physiology. Our objective was therefore to review the existing literature on the role of physiology as a proximate driver for life-history strategies in salmonids. This link is necessary to explore since physiology is at the core of biological processes influencing energy acquisition and allocation. Energy acquisition and allocation processes, in turn, can affect life histories. We find that life-history strategies are driven by a range of physiological processes, ranging from metabolism and nutritional status to endocrinology. Our review revealed that the role of these physiological processes can vary across species and individuals depending on the life-history decision(s) to be made. In addition, while findings sometimes vary by species, results appear to be consistent in species with similar life cycles. We conclude that despite much work having been conducted on the topic, the study of physiology and its role in determining life-history strategies in salmonids remains somewhat unexplored, particularly for char and trout (excluding brown trout) species. Understanding these mechanistic links is necessary if we are to understand adequately how changing environments will impact salmonid populations.