Vulnerability and adaptability of Africa’s inland fisheries to climate change : an interdisciplinary approach to a multi-dimensional conservation challenge

This thesis takes a cross-disciplinary approach employing both quantitative and qualitative methodologies to integrate social and ecological data for a holistic understanding of the vulnerability of Africa’s freshwater fisheries to climate change. This thesis is comprised of three major sections: the first (Chapter 1) uses a meta-analytical approach to predict vulnerability of Africa’s exploited freshwater fishes based on species traits and predicted climate change exposure. The second section (Chapters 2 and 3) employs an experimental approach to test the ability of the Nile perch, a commercially harvested fish species in the Lake Victoria basin of East Africa, to physiologically adjust thermal tolerance limits to increased water temperatures. The final section, (Chapter 4), investigates how fishing-dependent communities adjust to climate-mediated changes in the ecosystem with the aim to determine vulnerability and resilience of stakeholder communities to projected changes in the fishery

An optimistic outlook on the use of evidence syntheses to inform environmental decision-making

Practitioners and policymakers working in environmental arenas make decisions that can have large impacts on ecosystems. Basing such decisions on high‐quality evidence about the effectiveness of different interventions can often maximize the success of policy and management. Accordingly, it is vital to understand how environmental professionals working at the science‐policy interface view and use different types of evidence, including evidence syntheses that collate and summarize available knowledge on a specific topic to save time for decision‐makers. We interviewed 84 senior environmental professionals in Canada working at the science‐policy interface to explore their confidence in, and use of, evidence syntheses within their organizations. Interviewees value evidence syntheses because they increase confidence in decision‐making, particularly for high‐profile or risky decisions. Despite this enthusiasm, the apparent lack of available syntheses for many environmental issues means that use can be limited and tends to be opportunistic. Our research suggests that if relevant, high quality evidence syntheses exist, they are likely to be used and embraced in decision‐making spheres. Therefore, efforts to increase capacity for conducting evidence syntheses within government agencies and/or funding such activities by external bodies have the potential to enable evidence‐based decision‐making.Additional co-authors: Karen E. Smokorowski, Steven M. Alexander, Steven J. Cook

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’)1,2,3,4. 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.Additional co-authors: Pierre Charlebois, Manuel Barange, Stefania Vannuccini, Ling Cao, Kristin M. Kleisner, Eric B. Rimm, Goodarz Danaei, Camille DeSisto, Heather Kelahan, Kathryn J. Fiorella, Edward H. Allison, Jessica Fanzo & Shakuntala H. Thilste

Movement and home range of introduced Nile perch (Lates niloticus) in Lake Nabugabo, Uganda: implications for ecological divergence and fisheries management.

Lake Victoria basin East Africa Home range and movement patterns Habitat selection Tropical inland fishery management a b s t r a c t Nile perch (Lates niloticus) was introduced to the Lake Victoria basin in the 1950s and 1960s and eventually became one of the most valuable commercial species of East Africa's inland fisheries. Intense fishinginduced mortality may be contributing to dramatic ecological change in this species (reductions in body size and catch rate) and reinforcing patterns of ecological divergence in some lakes in the region. We used radio telemetry to characterize Nile perch movement and home range size in Lake Nabugabo, Uganda and quantified patterns of habitat selection by Nile perch in the heavily-fished near-shore areas of this system. Nile perch exhibited high site tenacity with daily movement averaging ∼400 m/day and home range size averaging 0.83 km 2 . Body size and water temperature were both important predictors of Nile perch movement patterns. In the near-shore area of the lake, Nile perch selected regions characterized by low temperature and high oxygen conditions, and tended to prefer forest edge over wetland edge. The level of site tenacity exhibited by Nile perch suggests that ecological isolation between fish using forest and wetland ecotones may be higher than expected. These results also have important implications for development of territorial jurisdiction by Beach Management Units, the decentralized structure of fisheries management in the region

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

Increasing water temperatures due 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 to 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 due to limitations in AS

Data from: 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 quantify thermal acclimation capacity in the commercially harvested Nile perch (Lates niloticus) of East Africa, and investigate 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, AS) 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-months) exposure to elevated temperature induced compensation in upper thermal tolerance (CTmax) and metabolic performance (SMR, MMR and AS), 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 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

African fish species' traits related to climate change vulnerability

Collation of available data on African freshwater fish species traits gleaned from publicly available repositories (IUCN Red List, FishBase) including data on life history traits, distributions, habitat use, dietary preferences, spawning behaviour, migratory behaviour, estimates of population size, and estimates of environmental tolerances, among others. Also includes data on threats experienced, human uses, and climate change projections across each species' range as predicted by the IPCC 5th assessment report

Data from: Assessing the vulnerability of Africa's freshwater fishes to climate change: a continent-wide trait-based analysis

Climate change is a key driver of biodiversity loss across the globe, and freshwater fishes are predicted to be among the most vulnerable taxa. African freshwater ecosystems are home to one of the most unique and diverse ichthyo-faunas on the planet, and freshwater fish species provide essential livelihoods for millions of people living in riparian communities across the continent. Although nearly one sixth of African freshwater fishes have been designated as endangered or vulnerable to extinction by the IUCN Red List assessment, the effects of climate change on these species have not been explored on a continent-wide scale. In this study, we present the first trait-based climate change vulnerability assessment (CCVA) comprising the majority (85%) of Africa's currently described freshwater fishes. We assembled data relating to three dimensions of vulnerability including sensitivity, adaptive capacity, and exposure. In addition, we developed an index of ‘conservation value’ based on traditional conservation metrics including extinction risk, endemism, and provision of ecosystem services. We found that almost 40% of African freshwater fishes are vulnerable to climate change, mostly owing to the many species with highly specialized habitat and life-history requirements, and because of the numerous anthropogenic stressors they face. High proportions of species within the Nothobranchiidae and Cichlidae families were found to be vulnerable. Regions with high frequencies of vulnerable species included the African rift valley lakes, the Congo River drainage, and the coastal rivers of West Africa. Several important data deficiencies were identified relating to species' population sizes, genetic variability, and life history traits, and constitute priority research areas for the future. In addition, we highlighted some cases where traditional conservation approaches overlook species and regions that are predicted to be threatened by climate change

Overcoming the concrete conquest of aquatic ecosystems

In reflecting on the human domination of our planet in the Anthropocene, some have argued that concrete is among the most destructive materials created by humans. Here we explore this idea, specifically in the context of what we consider “the concrete conquest of aquatic ecosystems.” The ubiquitous use of concrete in transportation and building infrastructure has contributed to alterations in freshwater and coastal marine systems. Yet, in some cases, there are no appropriate alternative building materials such that concrete itself is confounded by its application. For example, as the foundation for most dams, concrete fragments rivers and channelizes streams, often creating unnatural systems, yet dams are necessary for hydropower generation and flood control with few alternative materials for construction. In riparian and coastal environments, concrete harbours and inland canal systems are often used to address erosion or reclaim areas for human development. Even when removed (e.g., dam removal, naturalization of shorelines), concrete dust is a major aquatic pollutant. Instances do exist, however, where concrete has been used to benefit aquatic ecosystems – such as the installation of fish passage facilities at barriers or the development of fish-friendly culverts – though even then, there is a movement towards nature-like fishways that avoid the use of harmful materials like concrete. There are also opportunities to achieve conservation gains in the development of seawalls that include more natural and complex features to benefit biota and allow for essential biogeochemical processes to occur in aquatic environments. There have been several innovations in recent years that increase the permeability of concrete, however these have limited application in an aquatic context (e.g., not relevant to dam construction or erosion control but may be relevant in stormwater management systems). We provide a brief overview of the history of concrete, discuss some of the direct and indirect effects of concrete on aquatic ecosystems, and encourage planners, engineers, developers, and regulators to work collaboratively to explore alternatives to concrete which benefit aquatic ecosystems and the services they offer. The status quo of concrete being the default construction material is failing aquatic ecosystems, so we recommend that efforts are made to explore alternative materials and if concrete must be used, to increase structural complexity to benefit biodiversity. •Concrete is among the most permanent human-created materials on Earth and its use appears to be increasing.•Concrete has played a major role in altering freshwater and coastal marine habitats through processes such as damming, channelization, and construction of seawalls.•Collectively, these activities have simplified habitats and reduced aquatic biodiversit.y•Concrete has, however, been used to benefit aquatic ecosystems (e.g., fishways, seawalls that have structural elements that support biodiversity.)•We encourage relevant parties to work collaboratively to explore alternatives to concrete which benefit aquatic ecosystems

Overturning stereotypes: The fuzzy boundary between recreational and subsistence inland fisheries

Inland recreational fisheries provide numerous socio-economic benefits to fishers, families and communities. Recreationally harvested fish are also frequently consumed and may provide affordable and sustainable but undervalued contributions to human nutrition. Quantifying the degree to which recreationally harvested fish contribute to food security and subsistence is impeded by lack of data on harvest and consumption and by the difficulty in differentiating among recreational and subsistence fisheries. Recreational harvest records tend to be limited to wealthy, food-secure countries and well-monitored fisheries with clear regulations or permitting systems. These records often neglect components of recreational harvest among food-insecure fishers who are potentially more likely to have consumption as a motivation. Here, we highlight the ‘fuzzy boundary’ that can exist between inland recreational and subsistence fisheries and argue that unreported consumption is likely to be a hidden contributor to food security in some populations. We draw on local case studies from around the world to highlight specific instances where recreationally harvested fish species contribute food and subsistence benefits to participating communities. We use these examples to highlight the diversity of ways that inland recreational fisheries contribute to human nutrition, knowledge gaps in understanding recreational fishing for food, and consequences of not accounting for them as food fisheries in policy and management. The aim of this paper is to draw the attention of resource managers and policy makers, create greater social awareness of the importance of recreational fisheries and bring to light this hidden contribution of inland fisheries to nutrition and subsistence.Fil: Nyboer, Elizabeth A.. Institute Of Environmental And Interdisciplinary Science; CanadáFil: Embke, Holly S.. United States Geological Survey; Estados Unidos. University of Wisconsin; Estados UnidosFil: Robertson, Ashley M.. George Mason University; Estados UnidosFil: Arlinghaus, Robert. Leibniz - Institute of Freshwater Ecology and Inland Fisheries; AlemaniaFil: Bower, Shannon. Infinity Social And Ecological Solutions; CanadáFil: Baigún, Claudio Rafael M.. Universidad Nacional de San Martín. Instituto de Investigación e Ingeniería Ambiental. - Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigación e Ingeniería Ambiental; ArgentinaFil: Beard, Douglas. United States Geological Survey; Estados UnidosFil: Cooke, Steven J.. Institute Of Environmental And Interdisciplinary Science; CanadáFil: Cowx, Ian G.. University of Hull; Reino UnidoFil: Koehn, John D.. Arthur Rylah Institute For Environmental Research; AustraliaFil: Lyach, Roman. Institute For Evaluations And Social Analyses; República ChecaFil: Milardi, Marco. Fisheries New Zealand; Nueva ZelandaFil: Potts, Warren. Rhodes University; SudáfricaFil: Lynch, Abigail J.. United States Geological Survey; Estados Unido