Inland recreational fisheries contribute nutritional benefits and economic value but are vulnerable to climate change.

Inland recreational fishing is primarily considered a leisure-driven activity in freshwaters, yet its harvest can contribute to food systems. Here we estimate that the harvest from inland recreational fishing equates to just over one-tenth of all reported inland fisheries catch globally. The estimated total consumptive use value of inland recreational fish destined for human consumption may reach US$9.95 billion annually. We identify Austria, Canada, Germany and Slovakia as countries above the third quantile for nutrition, economic value and climate vulnerability. These results have important implications for populations dependent on inland recreational fishing for food. Our findings can inform climate adaptation planning for inland recreational fisheries, particularly those not currently managed as food fisheries.

Goals, challenges, and next steps in transdisciplinary fisheries research: perspectives and experiences from early-career researchers.

Fisheries are highly complex social-ecological systems that often face 'wicked' problems from unsustainable resource management to climate change. Addressing these challenges requires transdisciplinary approaches that integrate perspectives across scientific disciplines and knowledge systems. Despite widespread calls for transdisciplinary fisheries research (TFR), there are still limitations in personal and institutional capacity to conduct and support this work to the highest potential. The viewpoints of early career researchers (ECRs) in this field can illuminate challenges and promote systemic change within fisheries research. This paper presents the perspectives of ECRs from across the globe, gathered through a virtual workshop held during the 2021 World Fisheries Congress, on goals, challenges, and future potential for TFR. Big picture goals for TFR were guided by principles of co-production and included (i) integrating transdisciplinary thinking at all stages of the research process, (ii) ensuring that research is inclusive and equitable, (iii) co-creating knowledge that is credible, relevant, actionable, and impactful, and (iv) consistently communicating with partners. Institutional inertia, lack of recognition of the extra time and labour required for TFR, and lack of skill development opportunities were identified as three key barriers in conducting TFR. Several critical actions were identified to help ECRs, established researchers, and institutions reach these goals. We encourage ECRs to form peer-mentorship networks to guide each other along the way. We suggest that established researchers ensure consistent mentorship while also giving space to ECR voices. Actions for institutions include retooling education programs, developing and implementing new metrics of impact, and critically examining individualism and privilege in academia. We suggest that the opportunities and actions identified here, if widely embraced now, can enable research that addresses complex challenges facing fishery systems contributing to a healthier future for fish and humans alike.

Global dataset of species-specific inland recreational fisheries harvest for consumption.

Inland recreational fisheries, found in lakes, rivers, and other landlocked waters, are important to livelihoods, nutrition, leisure, and other societal ecosystem services worldwide. Although recreationally-caught fish are frequently harvested and consumed by fishers, their contribution to food and nutrition has not been adequately quantified due to lack of data, poor monitoring, and under-reporting, especially in developing countries. Beyond limited global harvest estimates, few have explored species-specific harvest patterns, although this variability has implications for fisheries management and food security. Given the continued growth of the recreational fishery sector, understanding inland recreational fish harvest and consumption rates represents a critical knowledge gap. Based on a comprehensive literature search and expert knowledge review, we quantified multiple aspects of global inland recreational fisheries for 81 countries spanning ~192 species. For each country, we assembled recreational fishing participation rate and estimated species-specific harvest and consumption rate. This dataset provides a foundation for future assessments, including understanding nutritional and economic contributions of inland recreational fisheries.

Aquatic foods to nourish nations.

Despite contributing to healthy diets for billions of people, aquatic foods are often undervalued as a nutritional solution because their diversity is often reduced to the protein and energy value of a single food type ('seafood' or 'fish')1-4. Here we create a cohesive model that unites terrestrial foods with nearly 3,000 taxa of aquatic foods to understand the future impact of aquatic foods on human nutrition. We project two plausible futures to 2030: a baseline scenario with moderate growth in aquatic animal-source food (AASF) production, and a high-production scenario with a 15-million-tonne increased supply of AASFs over the business-as-usual scenario in 2030, driven largely by investment and innovation in aquaculture production. By comparing changes in AASF consumption between the scenarios, we elucidate geographic and demographic vulnerabilities and estimate health impacts from diet-related causes. Globally, we find that a high-production scenario will decrease AASF prices by 26% and increase their consumption, thereby reducing the consumption of red and processed meats that can lead to diet-related non-communicable diseases5,6 while also preventing approximately 166 million cases of inadequate micronutrient intake. This finding provides a broad evidentiary basis for policy makers and development stakeholders to capitalize on the potential of aquatic foods to reduce food and nutrition insecurity and tackle malnutrition in all its forms.

Global assessment of marine and freshwater recreational fish reveals mismatch in climate change vulnerability and conservation effort.

Recreational fisheries contribute substantially to the sociocultural and economic well-being of coastal and riparian regions worldwide, but climate change threatens their sustainability. Fishery managers require information on how climate change will impact key recreational species; however, the absence of a global assessment hinders both directed and widespread conservation efforts. In this study, we present the first global climate change vulnerability assessment of recreationally targeted fish species from marine and freshwater environments (including diadromous fishes). We use climate change projections and data on species' physiological and ecological traits to quantify and map global climate vulnerability and analyze these patterns alongside the indices of socioeconomic value and conservation effort to determine where efforts are sufficient and where they might fall short. We found that over 20% of recreationally targeted fishes are vulnerable to climate change under a high emission scenario. Overall, marine fishes had the highest number of vulnerable species, concentrated in regions with sensitive habitat types (e.g., coral reefs). However, freshwater fishes had higher proportions of species at risk from climate change, with concentrations in northern Europe, Australia, and southern Africa. Mismatches in conservation effort and vulnerability were found within all regions and life-history groups. A key pattern was that current conservation effort focused primarily on marine fishes of high socioeconomic value rather than on the freshwater and diadromous fishes that were predicted to be proportionately more vulnerable. While several marine regions were notably lacking in protection (e.g., Caribbean Sea, Banda Sea), only 19% of vulnerable marine species were without conservation effort. By contrast, 72% of freshwater fishes and 33% of diadromous fishes had no measures in place, despite their high vulnerability and cultural value. The spatial and taxonomic analyses presented here provide guidance for the future conservation and management of recreational fisheries as climate change progresses.

Divergence in aerobic scope and thermal tolerance is related to local thermal regime in two populations of introduced Nile perch (Lates niloticus).

We tested whether thermal tolerance and aerobic performance differed between two populations of Nile perch (Lates niloticus) originating from the same source population six decades after their introduction into two lakes in the Lake Victoria basin in East Africa. We used short-term acclimation of juvenile fish to a range of temperatures from ambient to +6°C, and performed critical thermal maximum (CTmax ) and respirometry tests to measure upper thermal tolerance, resting and maximum metabolic rates, and aerobic scope (AS). Across acclimation temperatures, Nile perch from the cooler lake (Lake Nabugabo, Uganda) tended to have lower thermal tolerance (i.e., CTmax ) and lower aerobic performance (i.e., AS) than Nile perch from the warmer waters of Lake Victoria (Bugonga region, Uganda). Effects of temperature acclimation were more pronounced in the Lake Victoria population, with the Lake Nabugabo fish showing less thermal plasticity in most metabolic traits. Our results suggest phenotypic divergence in thermal tolerance between these two introduced populations in a direction consistent with an adaptive response to local thermal regimes.

Cardiac plasticity influences aerobic performance and thermal tolerance in a tropical, freshwater fish at elevated temperatures.

Fishes faced with novel thermal conditions often modify physiological functioning to compensate for elevated temperatures. This physiological plasticity (thermal acclimation) has been shown to improve metabolic performance and extend thermal limits in many species. Adjustments in cardiorespiratory function are often invoked as mechanisms underlying thermal plasticity because limitations in oxygen supply have been predicted to define thermal optima in fishes; however, few studies have explicitly linked cardiorespiratory plasticity to metabolic compensation. Here, we quantified thermal acclimation capacity in the commercially harvested Nile perch (Lates niloticus) of East Africa, and investigated mechanisms underlying observed changes. We reared juvenile Nile perch for 3 months under two temperature regimes, and then measured a series of metabolic traits (e.g. aerobic scope) and critical thermal maximum (CTmax) upon acute exposure to a range of experimental temperatures. We also measured morphological traits of heart ventricles, gills and brains to identify potential mechanisms for compensation. We found that long-term (3 month) exposure to elevated temperature induced compensation in upper thermal tolerance (CTmax) and metabolic performance (standard and maximum metabolic rate, and aerobic scope), and induced cardiac remodeling in Nile perch. Furthermore, variation in heart morphology influenced variations in metabolic function and thermal tolerance. These results indicate that plastic changes enacted over longer exposures lead to differences in metabolic flexibility when organisms are acutely exposed to temperature variation. Furthermore, we established functional links between cardiac plasticity, metabolic performance and thermal tolerance, providing evidence that plasticity in cardiac capacity may be one mechanism for coping with climate change.

Elevated temperature and acclimation time affect metabolic performance in the heavily exploited Nile perch of Lake Victoria.

Increasing water temperatures owing to anthropogenic climate change are predicted to negatively impact the aerobic metabolic performance of aquatic ectotherms. Specifically, it has been hypothesized that thermal increases result in reductions in aerobic scope (AS), which lead to decreases in energy available for essential fitness and performance functions. Consequences of warming are anticipated to be especially severe for warm-adapted tropical species as they are thought to have narrow thermal windows and limited plasticity for coping with elevated temperatures. In this study we test how predicted warming may affect the aerobic performance of Nile perch (Lates niloticus), a commercially harvested fish species in the Lake Victoria basin of East Africa. We measured critical thermal maxima (CTmax) and key metabolic variables such as AS and excess post-exercise oxygen consumption (EPOC) across a range of temperatures, and compared responses between acute (3-day) exposures and 3-week acclimations. CTmax increased with acclimation temperature; however, 3-week-acclimated fish had higher overall CTmax than acutely exposed individuals. Nile perch also showed the capacity to increase or maintain high AS even at temperatures well beyond their current range; however, acclimated Nile perch had lower AS compared with acutely exposed fish. These changes were accompanied by lower EPOC, suggesting that drops in AS may reflect improved energy utilization after acclimation, a finding that is supported by improvements in growth at high temperatures over the acclimation period. Overall, the results challenge predictions that tropical species have limited thermal plasticity, and that high temperatures will be detrimental because of limitations in AS.