Freshwater Fisheries Management Research Articles

Collaboration and engagement with decision-makers are needed to reduce evidence complacency in wildlife management.

There exists an extensive, diverse, and robust evidence base to support complex decisions that address the planetary biodiversity crisis. However, it is generally not sought or used by environmental decision-makers, who instead draw on intuition, experience, or opinion to inform important decisions. Thus, there is a need to examine evidence exchange processes in wildlife management to understand the multiple inputs to decisions. Here, we adopt a novel approach, fuzzy cognitive mapping (FCM), to examine perceptions of individuals from Indigenous and Western governments on the reliability of evidence which may influence freshwater fisheries management decisions in British Columbia, Canada. We facilitated four FCM workshops participants representing Indigenous or Western regulatory/governance groups of fisheries managers. Our results show that flows of evidence to decision-makers occur within a relatively closed governance network, constrained to the few well-connected decision-making organizations (i.e., wildlife management agencies) and their close partners. This implies that increased collaboration (i.e., knowledge co-production) and engagement (i.e., knowledge brokerage) with wildlife managers and decision-makers are needed to produce actionable evidence and increase evidence exchange.

Climate change, traditional ecological knowledge, and riverine biodiversity conservation: a case in Aklan, Central Philippines

AbstractWe framed climate change (CC) discourse through its disruptions to local culture and livelihood in a subsistence riverine fishing community in Central Philippines. Our main goal was contextualizing how local communities' traditional ecological knowledge (TEK) related to climate, fisheries, and taboos can strengthen freshwater fisheries management and biodiversity conservation. We adopted a mixed-method purposive sampling of the 126 fishing households in the Nabaoy River Watershed in the municipality of Malay in Aklan province. The high CC awareness was associated with the increasing frequency and intensity of extreme climatological events and erratic weather patterns. These CC-driven perturbations were primarily attributed to the ballooning human population and deforestation. These threats, in turn, were linked to the diminishing state of the Nabaoy River, heralded by the perceived marked decline of frog and dragonfly populations believed to be indicators of river health. Riverine biodiversity was also perceived as dwindling, with fish catch and their sizes shrinking. Furthermore, the observed fishing taboos guiding local informal (de facto) institutions corroborated formal (de jure) temporal and spatial fisheries management measures. Indeed, local communities have relevant long-term knowledge of management (e.g., TEK) and development-oriented structures and systems (e.g., informal institutions). These invaluable social capital assets are crucial in building resilient governance systems to address local conservation issues and concerns, particularly in data-deficient areas or lacking formal management contexts. Hence, formal management interventions should integrate TEK and the informal institution in which it is embedded and engage local TEK holders as partners in freshwater conservation efforts.

Managing Canadian freshwater fisheries: persistent challenges and emerging opportunities

Freshwater fisheries and biodiversity have substantial economic, socio-cultural, and ecological value, but face severe and mounting anthropogenic threats. Canada's freshwater fisheries are not exempt from this, and provide excellent opportunities to better understand these overlooked and undervalued systems. Using expert and chain-referral sampling, we surveyed practitioners from across Canada about the management of freshwater fisheries. We used a mixed methods approach to identify and describe in detail many important aspects of the above processes, including 10 persistent and innate challenges in (1) bureaucratic sprawl, (2) lack of priority, (3) scope, (4) competing interests, (5) political inconstancy, (6) socio-ecological complexity, (7) limited tools, (8) geographies and scale, (9) reactivity, and (10) intersectoral frictions. Many of these challenges defy conventional problem solving (e.g., advocacy, basic science), leading to chronic incapacity and triage management in some freshwater fisheries. We highlight opportunities to increase management capacity, using innovation where conventional solutions fall short (e.g., using novel technologies to increase management scope). Achieving sustainability in Canadian freshwater fisheries will require ingenuity and supportive contributions beyond those that currently exist.

Environmental DNA (eDNA) applications in freshwater fisheries management and conservation in Canada: overview of current challenges and opportunities

Environmental DNA (eDNA) monitoring methods have played a significant role in improving fisheries management decisions. Yet, their impact to date has been rather limited in Canada, where eDNA sampling and analyses are only beginning to be used to inform management and conservation decisions, practices, and policies. Studies investigating hurdles to the incorporation of eDNA evidence into fisheries management decisions generally focus on technical challenges (i.e., risks of false-positive and false-negative detections). We set out to identify challenges that eDNA researchers and conservation practitioners must overcome to fully unlock the benefits of eDNA sampling for fish management in the Canadian context. We discuss aspects of the broad and heterogeneous geography, preponderance of regions located far from densely populated areas, complex political landscape, and cultural diversity of Canada that may complicate the design of reliable eDNA monitoring tools or restrict their use if not adequately addressed. To advocate for the wider use of eDNA sampling, we outline a number of action items that would facilitate the broad adoption of eDNA sampling as a monitoring tool at the Canadian scale.

Technoscience and the modernization of freshwater fisheries assessment and management

Inland fisheries assessment and management are challenging given the inherent complexity of working in diverse habitats (e.g., rivers, lakes, wetlands) that are dynamic on organisms that are often cryptic and where fishers are often highly mobile. Yet, technoscience is offering new tools that have the potential to reimagine how inland fisheries are assessed and managed. So-called “technoscience” refers to instances in which science and technology unfurl together, offering novel ways of spurring and achieving meaningful change. This paper considers the role of technoscience and its potential for modernizing the assessment and management of inland fisheries. It first explores technoscience and its potential benefits, followed by presentation of a series of synopses that explore the application (both successes and challenges) of new technologies such as environmental DNA (eDNA), genomics, electronic tags, drones, phone apps, iEcology, and artificial intelligence to assessment and management. The paper also considers the challenges and barriers that exist in adopting new technologies. The paper concludes with a provocative assessment of the potential of technoscience to reform and modernize inland fisheries assessment and management. Although these tools are increasingly being embraced, there is a lack of platforms for aggregating these data streams and providing managers with actionable information in a timely manner. The ideas presented here should serve as a catalyst for beginning to work collectively and collaboratively towards fisheries assessment and management systems that harness the power of technology and serve to modernize inland fisheries management. Such transformation is urgently needed given the dynamic nature of environmental change, the evolving threat matrix facing inland waters, and the complex behavior of fishers. Quite simply, a dynamic world demands dynamic fisheries management; technoscience has made that within reach. • Assessing and managing freshwater fisheries is challenging. • Technoscience offers opportunities to reimagine fisheries assessment and management. • Methods to aggregate real-time data streams are needed to yield actionable knowledge. • Challenges and barriers exist in adoption of new technologies but they can be overcome. • Dynamic fisheries demand more dynamic real-time assessment & management.

Nutrient composition and microbial food safety of a locally-processed fish product in Cambodia

AbstractPrahoc is a traditional, fermented fish product in Cambodian diets. Fermented products like Prahoc may play a range of beneficial roles nutritionally, culturally, and financially. However, the use of freshwater fish and long-term storage may also pose food safety risks of parasites and microorganisms. We conducted a mixed-methods study of Prahoc to describe the complex risks and benefits of this food that included semi-structured interviews (prahoc-producing households, n = 22; small and medium enterprises n = 6), production observation, sample collection and analysis of nutrient composition and food safety parameters. Nutrient composition analysis showed that while Prahoc contributes small amounts of zinc, iron, and other key minerals to the diet, it is also very high in sodium (∼101,621 mg kg-1). Food safety analyses showed that while further tests are needed to resolve Listeria monocytogenes, Salmonella spp., and Vibrio risks, all samples were in compliance with the Cambodia Standards for Prahoc, and there was no evidence of parasites. Participants described Prahoc as playing an essential dietary and cultural role, and also making important contributions to household welfare, particularly within households and businesses that sold Prahoc. Despite the potential risks of microbial food safety and high sodium intake, Prahoc production offers benefits by adding value to fresh fish, reducing loss and waste, and preserving the harvest. However, Prahoc production depends on fish availability and is limited by declining access and high prices. Thus, freshwater fisheries management should take into account Prahoc production activities, an important value chain activity that contributes to the livelihoods of rural Cambodian communities.

Size spectrum model reveals importance of considering species interactions in a freshwater fisheries management context

AbstractInland fisheries have a significant cultural and economic value around the globe, providing dietary protein, income, and recreation. Consequently, methods for monitoring and managing these important fisheries are continually being refined. In marine systems, multispecies size spectrum models have been increasingly used to explore management scenarios of important fish stocks within an ecosystem‐based fisheries management framework; however, these models have not been applied as extensively in freshwater systems. In this study, we developed a multispecies size spectrum model for the fish community of Lake Nipissing, a large, productive lake in Ontario, Canada. To the best of our knowledge, this is the first fully calibrated multispecies size spectrum model for an inland fishery. Using this model, we explored the impacts of potential fishing regimes and management scenarios on fish community dynamics while taking species interactions into account. Specifically, we examined how changes in fishing mortality affect (1) species biomass, (2) community size structure, and (3) stock recovery times. We found that community dynamics following changes in fishing mortality were driven by complex interactions among species, including competition and predation. The greatest changes in biomass and community size structure were observed following changes in fishing mortality of top predators, with community size structure most strongly influenced by changes in the mortality of the largest species. Counter to predictions based on generation time, the smallest species in our model exhibited the longest time to recovery due to strong competition and predation. Our results demonstrate the importance of considering species interactions in the management of inland fisheries and highlight the potential of size spectrum model use in freshwater systems.

Interacting effects of density and temperature on fish growth rates in freshwater protected populations.

Despite the demonstrated benefits of marine protected areas, there has been relatively little dialogue about freshwater protected areas (FPAs) even though some have been established to protect freshwater species from recreational and commercial fishers. After populations recover from fishing pressure, abundances and densities of formerly fished species increase, and we should therefore expect changes in demographic traits compared to those in exploited populations. To test this, we used capture-mark-recapture data for 10 Galaxias maculatus populations across a density gradient mediated by different degrees of fishery closure. We examined the extent to which density-dependent (DD) and density-independent (DI) effects interact to affect specific growth rates in post-recruit populations. We found that population density, stream temperature and individual size interact to affect growth rates. When population densities were high, compensatory responses of far slower growth rates were strongest, indicating that DD growth is a key mechanism regulating post-recruit populations of G. maculatus. This study emphasizes the importance of understanding DD and DI processes, their interactions, function and effectiveness for freshwater fisheries management. For FPAs to be effective, the extent and quality of target species' habitats must serve as key criteria for protection to alleviate competition for limited resources that underpins DD processes.

Revisiting the challenge: perspectives on Canada’s freshwater fisheries policies three decades after the Pearse Report

A seminal report by Peter H. Pearse (1988; Rising to the Challenge: A New Policy for Canada’s Freshwater Fisheries, Canadian Wildlife Federation, Ottawa) outlined 62 policy recommendations focused on the management of Canada’s inland fisheries. Over three decades later, freshwater ecosystems and inland fisheries in Canada are still facing similar challenges with many emerging ones that could not have been foreseen. Here, we reflect on the contemporary relevance of the Pearse Report and propose recommendations that policy makers should consider. Broadly, our recommendations are: (1) manage fishes, fisheries, and habitat using a holistic co-management framework, with clearly defined fishery jurisdictions and partnerships with Indigenous governments; (2) engage in transparent, inclusive, and agile research to support decision-making; (3) facilitate knowledge co-production, involving interdisciplinary projects with diverse groups of actors and sectors including Indigenous Peoples, anglers, policy makers, scientists/researchers, governments, and the public; (4) embrace technological advances to support freshwater fisheries stock assessment and management; and (5) align policy and management activities in Canada with global initiatives related to increasing the sustainability of inland fisheries. We advocate for an updated comprehensive report such as the Pearse Report to ensure that we embrace robust, inclusive, and sustainable management strategies and policies for Canada’s inland fisheries for the next 30 years. It is time to again rise to the challenge.

Reconstructing Kenya’s total freshwater fisheries catches: 1950–2017

Most freshwater fisheries occur in developing countries, where freshwater fish underpin local food security and small-scale fisheries livelihoods. Comprehensive catch data are fundamental to support the sustainable management of freshwater fisheries. However, freshwater catch data reported by the Food and Agriculture Organization of the United Nations (FAO) on behalf of countries under-represent freshwater fisheries because they are dominated by fragmented and highly dispersed small-scale sectors, often with no designated landing sites. Kenya is an emerging economy with socioeconomically important freshwater fisheries and ongoing food security concerns. We undertook a reconstruction of freshwater fisheries catch data for Kenya for the period 1950–2017, aiming to improve the comprehensiveness of existing reported baseline data and to provide a more ecologically and spatially relevant time series dataset for research and management uses. We reconstructed catches for 16 major waterbodies in Kenya and found catches to be 32% higher than the data reported by the FAO on behalf of the country. The subsistence sector (small-scale, non-commercial, personal consumption) accounted for 71% of unreported catches, compared with 29% for artisanal sector catches (small-scale, commercial), suggesting that non-commercial catches for direct local consumption are substantially under-represented in nationally reported statistics and should receive greater attention to support sustainable food security in Kenya.

Na Vuku Makawa ni Qoli: Indigenous Fishing Knowledge (IFK) in Fiji and the Pacific

The time-tested Indigenous fishing knowledge (IFK) of Fiji and the Pacific Islands is seriously threatened due to the commercialization of fishing, breakdown of traditional communal leadership and oral knowledge transmission systems, modern education, and the movement of the younger generations to urban areas for work and/or study. Consequently, IFK, which has been orally transmitted for generations, has either been lost, not learned by the current generation, or remains undocumented. This study focuses on the critical need to conserve and include IFK as a basis for assessing the conservation status of ecologically and culturally keystone fisheries species as a basis for planning site-specific management of marine and freshwater fisheries in Fiji and the Pacific Islands. The study reviews studies of the last two and a half centuries on IFK from Fiji and elsewhere in the small oceanic islands of the Pacific, as a basis for the conservation, documentation and intergenerational transfer of this knowledge as the foundation for sustainable fisheries management. The study also reviews: the nature and conservation status of IFK, itself; and the conservation status of species considered to be of particular ecological and cultural importance; reasons for the loss of species/taxa and associated knowledge and practices; and actions that can be taken to address this loss.

A global perspective on the influence of the COVID-19 pandemic on freshwater fish biodiversity

The COVID-19 global pandemic and resulting effects on the economy and society (e.g., sheltering-in-place, alterations in transportation, changes in consumer behaviour, loss of employment) have yielded some benefits and risks to biodiversity. Here, we considered the ways the COVID-19 pandemic has influenced (or may influence) freshwater fish biodiversity (e.g., richness, abundance). In many cases, we could only consider potential impacts using documented examples (often from the media) of likely changes, because anecdotal observations are still emerging and data-driven studies are yet to be completed or even undertaken. We evaluated the potential for the pandemic to either mitigate or amplify widely acknowledged, pre-existing threats to freshwater fish biodiversity (i.e., invasive species, pollution, fragmentation, flow alteration, habitat loss and alteration, climate change, exploitation). Indeed, we identified examples spanning the extremes of positive and negative outcomes for almost all known threats. We also considered the pandemic's impact on freshwater fisheries demand, assessment, research, compliance monitoring, and management interventions (e.g., restoration), with disruptions being experienced in all domains. Importantly, we provide a forward-looking synthesis that considers the potential mechanisms and pathways by which the consequences of the pandemic may positively and negatively impact freshwater fishes over the longer term. We conclude with a candid assessment of the current management and policy responses and the extent to which they ensure freshwater fish populations and biodiversity are conserved for human and aquatic ecosystem benefits in perpetuity.

Use of Environmental DNA to Determine Fantail Darter (Etheostoma flabellare) Density in a Laboratory Setting: Effects of Biomass and Filtration Method

Estimating fish abundance/biomass holds great importance for freshwater ecology and fisheries management, but current techniques can be expensive, time-consuming, and potentially harmful to target organisms. Environmental DNA (eDNA) has proven an effective and efficient technique for presence/absence detection of freshwater vertebrates. Additionally, recent studies report correlations between target organism density/biomass and eDNA levels, although widespread application of this technique is limited by the number of studies examining this relationship in various species and settings. Additionally, filter clogging is a commonly encountered issue in eDNA studies in environments with significant sediment and/or phytoplankton algae. Frequently, a sample must be split into multiple aliquots and filtered separately in order to process the entire sample. The present study examines both the relationship between biomass and eDNA and the effects of single versus multiple filter sampling on eDNA concentrations of fantail darters (Etheostoma flabellare) in a laboratory setting. Tank tests were performed in quadruplicate at four environmentally relevant fantail biomass levels. eDNA samples were collected and processed in parallel (one as a whole through a single filter and one in parts through multiple filters). Species-specific primers and a probe were developed for E. flabellare from cytochrome b sequences obtained from locally collected specimens, and real-time quantitative PCR was used to analyze eDNA levels at each biomass. Significant correlations were observed with increasing biomass for both methods, although this relationship was stronger for samples processed by the multiple filter method. These data should be useful in eDNA studies in which turbidity necessitates the use of multiple filters per sample as well as in the use of eDNA to estimate darter populations.

Status and impacts of non‐native freshwater fish on fisheries biodiversity and biogeography in Kenya: A management perspective

AbstractThe introduction and spread of non‐native fish species in Kenyan inland freshwater systems are affecting the integrity of Kenya's aquatic biodiversity and ecosystems. The present study investigated the existing knowledge of non‐native fishes in Kenyan inland freshwater systems and their consequential implications regarding fisheries management. A total of 29 non‐native fish species have been introduced to Kenyan inland freshwater systems, with 20 of these being alien fish species and nine extralimital. These introductions have increased the fish faunal compositional similarity of inland drainage systems by 4.1% to a current similarity of 26.9%, compared to a historical similarity of 22.8%. Documented impacts of this situation include displacements, predation, competition, hybridization, habitat modification and disease transmission, all of which have had negative impacts on the status and management of Kenyan freshwater fisheries. The present study addresses the taxonomic bias created by existing studies on non‐native fishes focusing on individual species, by providing more information on the status of other non‐native species about which information is limited and whose status is uncertain. The present study presents information that can be used in management efforts to control invasions and mitigate their negative impacts.

Freshwater fish biodiversity in the Leizhou Peninsula of China

Leizhou Peninsula is located in the Indo-Burma biodiversity hotspot. However, information about freshwater fish species in this peninsula is very scarce. Based on surveys and a literature review, a total of 100 freshwater fish species (92 native and eight non-native) within seven orders, 21 families and 70 genera, have been recorded in the Leizhou Peninsula. Four species, Mud Carp (Cirrhinus molitorella), common carp (Cyprinus carpio), South Sharpbelly (Pseudohemiculter dispar), and Helmet Catfish (Cranoglanis bouderius) are listed as threatened species in red list of IUCN. Sand mining, aquaculture pollution, non-native aquatic species, and overfishing are the greatest threats to freshwater fish biodiversity of Leizhou Peninsula. For better sustainable development, conservation efforts should be focused on the establishment of protected areas, improvement of sustainable fishery management and control of non-native species. This study provides management recommendations that will be useful for freshwater fish biodiversity conservation and fishery management in Leizhou Peninsula.

A comparison of freshwater fisheries management in the USA and Japan

The USA and Japan differ in their approaches to managing inland recreational fisheries. The USA uses a public property rights regime whereby access rights are assigned to the states, which manage the fishery resource for the public good. Japan uses a common property rights regime whereby access rights for waterways are assigned to fishery unions, which manage the resource for the benefit of their members. Members of fishery unions are likely to develop an emotional attachment to the fishery that results in few regulation violations or illegal fish introductions. The USA would benefit from actions that promote such a caretaker attitude toward the environment. Habitat improvement is a major activity in the USA but is less prevalent in Japan where stocking is the dominant management activity. Catch-and-release angling, size restrictions, and employment of professional fisheries biologists are more prevalent in the USA compared to Japan. The USA has a tax on fishing equipment that funds management activities whereas such a funding source is lacking in Japan. Despite differences in management regimes, both countries face similar challenges in recruiting new anglers and meeting the conflicting mandates to enhance sport fisheries while conserving native species.

Evaluating a Stakeholder‐Driven Bass Regulation Change in Florida: Agency Staff and Stakeholder Perspectives

We evaluated stakeholder engagement aspects of a statewide Largemouth Bass Micropterus salmoides regulation change in Florida. Staff from the Florida Fish and Wildlife Conservation Commission (FWC) who worked on the project and stakeholders who participated in outreach were interviewed and/or surveyed about their opinions of the process. This was the largest stakeholder engagement process ever conducted by FWC for freshwater fisheries management decision making; therefore, an evaluation was critical to measure the success of the process and to inform future stakeholder engagement. Staff reflected positively on the process but noted breakdowns in communication and a lack of human dimensions expertise. Stakeholders felt that their input was appreciated and used by the agency to aid in decision making. This evaluation illustrates where the project was effective and areas where improvements can be made for future projects.

Inland fish stock assessment: Applying data‐poor methods from marine systems

AbstractInland fisheries can be diverse, local and highly seasonal. This complexity creates challenges for monitoring, and consequently, many inland fish stocks have few data and cannot be assessed using methods typically applied to industrial marine fisheries. In such situations, there may be a role for methods recently developed for assessment of data‐poor fish stocks. Herein, three established data‐poor assessment tools from marine systems are demonstrated to highlight their value to inland fisheries management. A case study application uses archived length, catch and catch‐per‐unit‐effort data to characterise the ecological status of an important recreational brown trout stock in an Irish lake. This case study is of specific use to management of freshwater sport fisheries, but the broader purpose of the paper was to provide a crossover between marine and inland fisheries science, and to highlight accessible data‐poor assessment approaches that may be applicable in diverse inland systems.

Satellite and Airborne Remote Sensing Applications for Freshwater Fisheries

Remote sensing has been pivotal to our understanding of freshwater fisheries, and we review this rapidly changing field with a focus on satellite and airborne applications. Historical applications emphasized spatial variation in the environment (e.g., watershed land use and in situ primary productivity), but improved access to imagery archives facilitates better change detection over time. New sensor platforms and technology now yield imagery with higher spatial, temporal, and spectral resolutions than ever before, which has accelerated development of remote sensing products that more accurately characterize aquatic environments. Free access to imagery archives, cloud computing, and availability of derived products linked to national hydrography databases are all removing historical barriers to its use by fisheries professionals. These advances in remote sensing have allowed new questions to be answered at finer spatial resolutions across broader landscapes and longer time frames, providing a new big‐picture perspective to freshwater fisheries conservation and management.

Analyzing the effects of estuarine freshwater fluxes on fish abundance using artificial neural network ensembles

Decreased estuarine freshwater inflow can adversely impact commercially and recreationally important fisheries as many fish species utilize estuaries during a portion of their life. To ameliorate effect on estuarine fisheries, regression models using fish catch and freshwater inflow have been implemented to determine minimum flow necessary to sustain these populations. These models typically use streamflow data, with no correction for evaporation and precipitation. Our models including evaporation and precipitation developed using artificial neural network (ANN) ensembles had nearly 50% better classification accuracy compared to regression model using flow. This ANN ensemble method was successfully applied to the Nueces Estuary in the United States. It can improve the decision-making processes of freshwater regulation and fishery management in many coastal regions.