Harvested Fish Research Articles

Fishing safely during COVID-19 in Newfoundland and Labrador, Canada: Making it happen

Globally, fisheries have been the site of multiple documented outbreaks of COVID-19. Existing studies point to the threat posed by the pandemic to livelihoods and health among migrant industrial fishery workers, small-scale fish harvesters, and fishing communities. They show the pandemic enhanced safety, economic, social and political layers of vulnerability in fisheries, while also showcasing examples of resilience. Case studies of COVID-19 response provide an opportunity to explore how existing organizational structures, leadership and networks in fisheries can enable the rapid co-development of customized strategies for fishing safely during large-scale global disruptions such as pandemics. This article contributes to our understanding of governance and fishing safety in small-scale fisheries during the early pandemic, examining the response of small-scale fisheries in the Canadian province of Newfoundland and Labrador. These seasonal fisheries successfully opened with regulator approval after a short delay and operated without documented COVID-19 outbreaks during 2020. Findings draw from key informant interviews with a safety sector association and union leader, complemented with insights from an anonymous online survey of small-scale harvesters. Interviews capture the organizational processes and resources mobilized to rapidly co-develop the COVID-19 Safe Work Practice Guideline. Online survey findings indicate that fifty-nine percent of respondents (crew and skippers) had no COVID-19-related concerns while fishing in 2020; older harvesters and owner-operators were significantly more likely to indicate concerns. When asked about the relative practicality of listed COVID-19 precautions, respondents commonly identified sanitization, reduced interactions with shore workers, social distancing, protection equipment, modifications to eating/rest areas, and reduced crew as impractical. These assessments are generally consistent with those of the interviewed leaders and the Guideline approach. This suggests the co-developed Guideline provided tailored and practical COVID-19 prevention strategies. Pre-existing governance structures and networks can help address small-scale fisheries vulnerabilities to pandemics by supporting co-development of organizational resources and evidence-informed prevention strategies.

Transnational fishers’ movements: emergence, evolution, and contestation

Global transformations in fisheries have contributed to the expansion of transnational movements, as they continuously seek out new ways to strengthen their global linkages and find spaces and platforms for engagement. As more platforms emerge for addressing international concerns, intergovernmental bodies have become increasingly implicated in navigating the political integration of diverse global actors, such as transnational fishers’ movements. Focusing on the World Forum of Fisher Peoples and the World Forum of Fish Harvesters and Fish Workers, this article tracks their engagement in the politics of global fisheries. It explores the history of these movements, beginning with the first steps that were taken toward building an international fishers’ network between 1984 and 1997, and follows their evolution into the movements they are today. It also examines their political agendas and strategies, and their representation of small-scale fishers in international spaces over the last two decades. The article argues that three pivotal developments offer important insights into the politics of transnational fishers’ movements. First, they are internalizing overlapping fisheries, food and climate crises, and are aligning their activities and demands accordingly. Second, fishers’ and agrarian movements and platforms are increasingly converging around common struggles. Third, international intergovernmental bodies have broadened their attention to fisheries issues in their analysis and activities. These developments have been crucial in shaping the movements’ political agendas, and for building alliances in order to scale up and strengthen their advocacy work.

Stability and bifurcation analysis of a phytoplankton-zooplankton-fish model involving fear in zooplankton species and fish harvesting

ABSTRACT In this paper, a predator–prey model that takes into account the interactions between three species of fish, zooplankton, and phytoplankton has been developed. The logistic growth of phytoplankton has been considered in the absence of zooplankton. It is assumed that zooplankton eats phytoplankton. It is considered that the growth rate of zooplankton decreases due to the fear of fish. The release of toxins by phytoplankton and fish consumption are two further factors that are assumed to decrease the growth rate of zooplankton. The harvesting of fish has also been considered in this study. Local and global stability of the system around the equilibrium points has been investigated. The existence condition of oscillatory behaviour of the system has been studied through Hopf bifurcation. It is found that the increasing rate of minimum cost of fear may stabilize the system. It is obtained that the rate of increase of release of toxin substance by phytoplankton may be responsible for the stability of the system. It is also found that the system may become unstable for the increase of level of fear of zooplankton. Some numerical simulation results are presented to test the theoretical findings.

Modeling of nutritional behavior and harvest profit margin in fattening pacu (Piaractus mesopotamicus) fed on balanced digestible protein contents and raised in an intensive recirculating aquaculture system

Adjusting aquafeed to obtain sustainable growth and maximum profit margin of harvest is a worthy stride toward achieving the Sustainable Development Goals (SDGs) outlined by the United Nations. Therefore, this research aimed at modeling of nutritional behavior and harvest profit margin in fattening pacu (Piaractus mesopotamicus) fed on balanced digestible protein (BDP) contents and raised in an intensive recirculating aquaculture system (RAS). The feeding trial consisted of six treatments with three randomly arranged replicates (tanks) per treatment. A total of ten fattening pacus (490.60 ± 14.39 g, initial weight) were stocked per tank. Six experimental feeds containing the increasing contents (163, 201, 238, 272, 315, and 348 g kg-1 diet, dry matter) of BDP were manually fed to the fish for seven weeks three times a day until apparent satiation. The data obtained over the test diets were assessed through appropriate statistical procedures and mathematical models. Optimal levels of BDP were calculated for different nutritional and economic scenarios. Feed cost showed an ascending linear relationship with the BDP intake. Feed intake, feed efficiency, final body weight, weight gain, and specific growth rate (%) showed an inverted U-shaped quadratic behavior (P < 0.05). Feed conversion ratio showed a U-shaped quadratic behavior (P < 0.05). Protein efficiency ratio significantly (P < 0.05) decreased linearly in response to the increasing BDP contents. Final weights of the eviscerated and sliced fish showed an ascending linear behavior, but the overall effect was insignificant (P > 0.05) between the treatments. Whole body moisture and crude protein content increased (P < 0.05) linearly, while the whole body lipid content decreased (P < 0.05) linearly over the increasing BDP intake. Whole body ash content showed a U-shaped quadratic behavior (P < 0.05). The nutritionally optimal BDP content corresponding to the maximum gain in body weight of fattening pacu was calculated as 292 g kg-1 diet (dry matter). To obtain sustainable growth and maximum profit margin of harvest when it will be sold in the form of whole-body, eviscerated, and sliced fish the economically functional BDP intakes were calculated as 249, 256, and 260 g kg-1 diet (dry matter), respectively. This research revealed that the optimal BDP intake greatly improve the nutritional performance of fattening pacu. Moreover, harvest profit margin and eventually the economically sustainable BDP intakes were found dependent on the way the fish harvest is marketed and the changes in total feed cost.

α‐2‐macroglobulin, an infection‐resistant biomarker in Epinephelus fuscoguttatus (Forsskål, 1775)

Epinephelus fuscoguttatus (Forsskål), or brown-marbled grouper, is a favoured species among aquaculture farmers for its relative easy management and high commercial value. Disease outbreaks, however, negatively impact farmers' livelihoods by reducing fish harvest yields. Traditional selective breeding of disease-resistant strains is still being practised due to limitations in vaccines and effective antibiotics. Development of biomarkers and molecular quantitative techniques has potential to advance approaches in handling outbreaks of disease. This study aimed to determine selected proteins' expression patterns and suitability as infection-resistant markers in brown-marbled grouper. Experimental infection of brown-marbled grouper with Vibrio parahaemolyticus was established. Fingerlings (N = 70) were acclimatized and maintained in saltwater at 28 ± 2°C, pH 7.9 ± 1, salinity 29 ± 1 ppt and dissolved oxygen 5 ppm. V. parahaemolyticus at 5 × 1011 CFU/ml was injected into the dorsal area of the fish and monitored for 7 days. Expressions of alpha-2-macroglobulin, nattectin and parvalbumin were determined in liver, spleen, and blood cells by quantitative PCR. Alpha-2-macroglobulin in plasma was detected by western blot immunoassay. Clinical signs of infection included skin haemorrhagic lesions and depigmentation. Susceptible and resistant fish were differentiated by lesions >5 cm and absence of lesion at injection site, respectively. Infection significantly increased expression of alpha-2-macroglobulin, nattectin and parvalbumin in the liver and spleen but not in blood cell samples. Levels of alpha-2-macroglobulin and parvalbumin were significantly increased in liver of susceptible grouper, whereas alpha-2-macroglobulin significantly increased in plasma of resistant fish. In conclusion, alpha-2-macroglobulin is a potential infection-resistant biomarker in brown-marbled grouper and readily detected in fish plasma.

Catch and release angling for sea trout explored by citizen science: Angler behavior, hooking location and bleeding patterns

Sea trout (anadromous brown trout, Salmo trutta L.) is a popular target species for angling in Denmark and many other countries. In most regions, angling for sea trout is regulated by measures such as minimum landing sizes, bag limits or seasonal closures. This can lead to high catch and release (C&R) rates. However, information about angler behavior, C&R practices, hooking locations and level of injury and bleeding, as well as post-release impacts on survival and growth, is largely missing for this species. In this study, we used a citizen science approach to investigate C&R practices of Danish sea trout anglers and to explore drivers for hooking location and bleeding. During the study period from January 2016 to August 2021, 35,826 sea trout caught by angling were reported by users of the citizen science platform. Spin fishing was the most popular angling method (46 %), followed by fly fishing (35 %), bombarda fishing (19 %) and natural bait fishing (1 %). The results confirmed that C&R is a very widespread practice among Danish sea trout anglers, and ≥80 % of all sea trout captured are being released, the majority because they are below the minimum landing size. Twenty-five percent of the caught sea trout bled, and 2 % showed heavy bleeding. Bleeding was related to hooking location (deeply hooked fish bled the most) and to angling method (fly-caught sea trout bled less than fish caught on spin fishing gear), but the role of these two factors varied with fish length. When looking at fish above the legal minimum size, the share of bleeders among the released sea trout was significantly lower compared to harvested fish, suggesting that anglers were more prone to harvest fish that bled. Further studies on lethal and sublethal effects of C&R on coastal sea trout are needed, ultimately aiming to provide fishery managers and anglers with species- and fishery-specific best practice C&R guidelines.

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.

How local communities access, utilise and evaluate inland fisheries, and their influence on fishery conservation status in northern Zimbabwe

The conservation status of inland fishery resources is vulnerable worldwide, and this threatens the livelihoods of fishing-dependent communities. This case study aimed to: (i) establish the use and perception of fisheries and ecosystem services by locals, (ii) undertake a monetary valuation of the fisheries, (iii) determine the potential threats to the fisheries, and (iv) examine the social drivers and barriers for citizen science involvement. Lastly, (v) we evaluated how the above factors affected the conservation of fisheries at Mushumbi Pools, Zimbabwe. A cross-sectional survey of 69 households was conducted. Results of the study showed that locals utilised 17 fish species for social, economic, cultural and religious purposes. Locals attach high intrinsic socio-economic value to the fisheries resources and wetland ecosystem services provided by the Mushumbi Pools. Despite the sustained income from fisheries, the local market in Mushumbi Pools is actually undervaluing fisheries resources, as the fish prices in the area are very low compared to standard market prices countrywide. A larger proportion of the respondents (65%) cited poor land-tilling practices, heavy application of agropesticides and use of unsustainable fish harvesting methods as the main threats to fish diversity in Mushumbi Pools. Relaxed fishing concessions for women and children in specific fishing zones were key drivers for community participation in fisheries conservation. However, strict enforcement of fishing bans in breeding and nursery zones and restricted access to some parts of the Mushumbi Pools were the main barriers for local involvement in the conservation of fisheries resources. Without the fishing community’s participation there is no guaranteed sustainability of the fishery resources in the pools. Legitimising community access, ensuring fair valuation and utility rights is a key driver for successful management of inland fisheries resources in Sub-Saharan Africa.

СУЧАСНИЙ СТАН ОСНОВНИХ ПРОМИСЛОВИХ ВИДІВ РИБ КРЕМЕНЧУЦЬКОГО ВОДОСХОВИЩА

The major quantitative and qualitative indicators of the main commercial fish species of the Kremenchug reservoir were analyzed in the study and the main parameters of the optimal commercial fisheries catch by gill nets were determined. Original materials for investigations were data of control commercial catches in the Kremenchug reservoir during 2021. Conservative techniques were used in sampling and analysis during ichthyological studies.&#x0D; Materials on the main commercial fish species in the Kremenchug reservoir were collected. Biological materials from commercial gill nets were selected and the fish productivity of the reservoir was determined.&#x0D; The work provides up-to-date information on the main biological indicators of commercial fish species of Kremenchug reservoir in modern conditions of anthropogenic press and calculates scientifically proven parameters of optimal commercial fish harvest.&#x0D; The article can be used by scientists, practitioners, fisheries patrol and the State Ecological Inspectorate to predict future catches and knowledge of the current situation with the main industrial fish species in the Kremenchug Reservoir. Modern material on the main commercial fish species will help to see the real picture in the reservoir and take necessary fish protection measures.

Non-Intrusive Fish Weight Estimation in Turbid Water Using Deep Learning and Regression Models.

Underwater fish monitoring is the one of the most challenging problems for efficiently feeding and harvesting fish, while still being environmentally friendly. The proposed 2D computer vision method is aimed at non-intrusively estimating the weight of Tilapia fish in turbid water environments. Additionally, the proposed method avoids the issue of using high-cost stereo cameras and instead uses only a low-cost video camera to observe the underwater life through a single channel recording. An in-house curated Tilapia-image dataset and Tilapia-file dataset with various ages of Tilapia are used. The proposed method consists of a Tilapia detection step and Tilapia weight-estimation step. A Mask Recurrent-Convolutional Neural Network model is first trained for detecting and extracting the image dimensions (i.e., in terms of image pixels) of the fish. Secondly, is the Tilapia weight-estimation step, wherein the proposed method estimates the depth of the fish in the tanks and then converts the Tilapia’s extracted image dimensions from pixels to centimeters. Subsequently, the Tilapia’s weight is estimated by a trained model based on regression learning. Linear regression, random forest regression, and support vector regression have been developed to determine the best models for weight estimation. The achieved experimental results have demonstrated that the proposed method yields a Mean Absolute Error of 42.54 g, R2 of 0.70, and an average weight error of 30.30 (±23.09) grams in a turbid water environment, respectively, which show the practicality of the proposed framework.

Paradigm Shift: Applying Capture–Recapture Techniques to Electronic Licensing System Data to Estimate Chinook Salmon Harvest

Implementing creel surveys that produce robust and unbiased estimates of harvest can be complicated, expensive, and labor intensive. Additionally, field personnel often face safety risks associated with traversing roads and highways, occasionally under inclement travel conditions. Here, we develop an alternative method to estimate recreational fish harvest using a hybrid creel that employs capture–recapture techniques in conjunction with data collected from the Oregon Department of Fish and Wildlife's electronic licensing system. We evaluated the method by comparing harvest estimates between the new approach (e-creel) and estimates from a traditional roving creel conducted on four of Oregon's coastal Chinook Salmon Oncorhynchus tshawytscha populations in 2019. Our results indicated that Chinook Salmon harvest estimates derived from our hybrid creel approach were more precise than estimates using traditional creel methods. Both methods generated statistically equivalent estimates of Chinook Salmon recreational harvest, differing by only 3.4%. Estimated mean harvest was 1,264 Chinook Salmon based on the e-creel approach versus 1,258 based on the traditional creel approach. On average, the e-creel estimates reduced the SE by 41% relative to traditional creel estimates. Post hoc assessment of spending associated with creel projects in 2019 suggested that a total savings of US$74,525 in personnel and operational cost, corresponding to an average 15% budget reduction per investigation, could be realized by transitioning from a traditional creel design to an e-creel design.

Impacts of brush pile fishing on fish biodiversity: A case study of the Shari-Goyain River in Bangladesh

Brush pile (katha), a fish aggregating device, has been widely used in the Shari-Goyain River since 2003 to congregate fish for easier catch. Katha is usually used during the winter season when the water depth decreases. Hence, this experiment was conducted from November 2018 to March 2019 on katha fishing to investigate its status and impacts on fisheries resources of the Shari-Goyain River in the Sylhet district of Bangladesh. The study was based on the hypothesis that katha fishing might have detrimental impacts to fish biodiversity and production. Data were obtained through a questionnaire-based survey, personal interviews, catch assessment (CA), focus group discussions, and key informant interviews. A total of 54 species were documented, including two exotic fish species (tilapia and common carp) and 3 species of prawn during harvesting of the kathas. The catch per unit effort (CPUE) (kg/gear/ha/person/hour) was the highest in December (1.13 ± 0.37), followed by November (1.06 ± 0.40), January (0.80 ± 0.25), February (0.71 ± 0.23), and March (0.52 ± 0.21). The catch per unit area (CPUA) (kg/ha) was the highest in November (264.66 ± 18.21), followed by December (205.05 ± 27.77), January (175.02 ± 76.04), February (147.73 ± 52.11), and March (102.08 ± 41.04) where significant differences (p < 0.05) among the months were observed. Average catch per katha in a month ranged from 41.09 ± 16.11 to 12.42 ± 5.89 kg, with a mean of 24.29 ± 11.08 kg, and a significant decrease in average catch was observed with the progression of months. The most species richness was noticed in December (38), followed by November (35), January (34), February (28), and March (25). Siluriformes (39.123%) was the most dominant order, followed by Cypriniformes (33.956%), Decapoda (14.661%), and Ovalentaria (3.278%). According to the CA and respondents’ perception, indiscriminate harvesting of fish by katha fishing can be a cause of fish biodiversity loss as it reduces open water catches, total production, and disturbs the ecosystem. From the research findings, it is suggested that katha fishing should be stopped for sustainable management and conservation of fisheries resources in the Shari-Goyain River. Research on the effects of katha fishing should be conducted in other open waters of Bangladesh where this type of fishing is common.

Economic, social, and environmental assessment of farming Nile tilapia in net-cages in a reservoir in hot semi-arid region during an extended drought event.

Water reservoirs have been constructed in hot semi-arid regions, which may be used to produce fish. The present study described major features of the economic, social, and environmental characteristics of a net-cage Nile tilapia production system, stocked with 100 and 120 fish/m3, implemented in a reservoir in the hot semi-arid region of Brazil during an extended drought event. The production cycle was reduced from 6-8 to 4 months because of the lack of water in the reservoir. This resulted in the harvest of small fish weighting ~300-350 g that reached a low value in the market. As a consequence, indicators of financial feasibility showed low values, which were not attractive for entrepreneurs. Nevertheless, for both stocking densities, the monthly income was about US$ 1,500.00, which is 5-fold the minimum wage in the region. In general, the activity has a positive social impact, despite the low contribution to development of the local economy and food security because most supply came from outside and fish were sold to distant regions. Various age and ethnic groups were represented among the employees, but the enterprise was operated only by men. Phosphorus accumulations in the reservoir were 2.1 and 2.0 kg/t of fish produced and particulate material accumulations of 110 and 100 kg/t of fish production for 125 fish/m3 and 100 fish/m3, respectively. The study indicated that the Nile tilapia culture in hot semi-arid region is strongly affected by long drought events and adaptations in the planning and management should be done when implementing the systems. However, it seems that the activity has some resilience to still provide food, generate wealth, and promote social development for local population with low environmental impact.

Restrictions on leader length in an in‐river sport fishery reduce catch of threatened wild chinook salmon Oncorhynchus tshawytscha and increase harvest of hatchery origin chinook

AbstractTo achieve conservation and harvest objectives associated with Chinook Salmon, fisheries managers have relied on mark‐selective and anti‐snagging rules in freshwater whereby anglers are required to release wild Chinook and fish hooked in anatomical locations other than the head and mouth. However, in some cases these regulations have resulted in increased mortalities due to the number of fish (hatchery and wild) that require release. Regulations effective at increasing the number of fish hooked in the mouth have the potential to decrease total encounters (number of fish caught) of both hatchery and wild fish while increasing the total number of fish harvested; however, this has not been tested. A roving creel survey and a test fishery were used to describe the effect leader length and bait under a bobber has on catch rate and hooking location and simulate how a variety of restrictions on gear type would affect catch and harvest on wild and hatchery origin Chinook salmon. Results indicate that a 6‐foot leader length restriction would result in the highest catch of hatchery fish harvested and reduce exploitation rate on wild fish by greater than 20%. Regulations limiting leader length to 3 feet are expected to result in the greatest reduction (75.7%) to total encounters on wild fish; however, this method was unpopular and resulted in few hatchery fish harvested. The use of bait suspended under a bobber resulted in intermediate results with a reduction of 60.0% to catch of wild Chinook and the smallest number hooked outside the mouth (0/30). These results provide the first evaluation of the effect of leader length in a mark‐selective hook and line fishery and suggest that a 6‐foot leader length restriction would be expected to reduce encounters on wild Chinook, increase harvest of hatchery fish and extend the fishing season.

Declining size-at-harvest in Norwegian salmon aquaculture: Lice, disease, and the role of stunboats

Sea cages used for fish farming are typically open to the environment, making the grow-out phase a race against the accumulation of infections. In Norway, farmed Atlantic salmon (Salmo salar) suffer outbreaks of salmon lice (Lepeophtheirus salmonis), which by law must be managed, and comorbid infections that weaken salmon and increase the risk of mortality following delousing treatments. To understand the role of louse management on size-at-harvest, we analysed monthly data from 1054 salmon farms over a 10-year period. Mean weight at harvest declined 6.6% (−310 g) from 2012 to 2021, with the smallest size-at-harvest occurring in months when delousing treatments were reported. In 2021, size-at-harvest was 3.4% smaller during treatment vs. non-treatment months. There is a pattern of increasing responsiveness to louse outbreaks over time, with delousing treatments preferred for small fish and harvesting preferred for large fish. There are also several lines of evidence suggesting that potential post-treatment mortalities are sometimes diverted to harvest statistics. Treatments tend to lead to higher relative mortality in the following month, except when a harvest was also reported during the treatment month. Stunboats are harvesting vessels equipped with stunning, bleeding and chilling systems, and anecdotally, are preferred for ‘emergency’ harvests. We found that stunboat visits were disproportionately associated with harvests of small fish during 2018–2021. Moreover, stunboats often visited during treatment months without any harvest being reported, consistent with accounts of stunboats standing by during risky operations to salvage moribund fish if necessary. Because harvests and mortalities are reported monthly, it is not clear how often harvests during treatment months reflect (i) harvesting of vulnerable fish as an alternative to treating, or (ii) risky treatments that produce moribund fish. However, if the latter is common, mortality statistics will underestimate the health and welfare risks of delousing treatments.

COVID-19 and small-scale fisheries in Africa: Impacts on livelihoods and the fish value chain in Cameroon and Liberia

This study explores the emerging impacts of the COVID-19 pandemic on coastal small-scale fishing communities in Cameroon and Liberia, where we conducted qualitative interviews with small-scale fish harvesters, fish processors, traders, and consumers. We found that the implementation of COVID-19 safety and health protocol initiatives impacted the entire fish value chain, which contributed to social anxiety and negatively affected social well-being for those who depend on small-scale fisheries for employment and livelihoods. Fisheries in both nations saw a reduction in fish catch, widened supply and demand gap and a significant spike in fish price. Drawing on the Sustainable Livelihoods literature, we discuss how COVID-19 interacted with other existing aspects of community vulnerability and lack of capacity, despite communities finding ways to respond safely to the challenges of the pandemic. Moving forward, these small-scale fisheries will require a holistic assessment of the long-term social, ecological, and economic impacts of the pandemic. Better fish processing and storage facilities and more robust institutional structures around markets and fisheries management will improve the adaptive capacity of people in these communities, who will no doubt face future challenges related to issues such as climate change.

Population Dynamics and Harvest Management of the Bonneville Cutthroat Trout Fishery in Bear Lake, Idaho–Utah

AbstractLand‐use disturbances and associated losses in habitat quantity and quality negatively affected the Bonneville Cutthroat Trout (BCT) Oncorhynchus clarkii utah population in Bear Lake, Idaho–Utah, in the early 1900s. Bear Lake BCT follow an adfluvial life history strategy, and without access to suitable spawning habitat, the population of wild BCT was nearly extirpated by the early 1950s. In response to this decline, supplementation of the population with hatchery BCT began in 1973. Production of wild BCT was minimal until conservation efforts shifted towards improving fish habitat and access to spawning tributaries. In 2002, only 5% of the population consisted of wild fish; by 2017, nearly 70% of BCT in annual population surveys were wild. As a result, rule changes have been proposed to allow for regulated harvest of wild BCT. However, gaining a comprehensive understanding of the population dynamics of BCT in Bear Lake is critical before changes are made to management of the fishery. The objectives of this study were to describe the population dynamics of wild and hatchery BCT in Bear Lake and evaluate different management options. We evaluated population demographics of hatchery and wild BCT in Bear Lake and used age‐structured population models to assess a variety of management scenarios associated with wild fish harvest regulations (e.g., bag limits). Bonneville Cutthroat Trout grew at relatively fast rates, and females began to mature at age 5. We observed considerable differences in the length and age structure of the hatchery population (i.e., exploited) versus the wild population (i.e., unexploited) of BCT. In general, BCT in Bear Lake were larger and older than Cutthroat Trout O. clarkii in other systems. The current rate of exploitation for hatchery BCT was estimated as 0.27 (i.e., two‐fish daily limit). If the limit were changed to a six‐fish daily limit, the rate of exploitation would be approximately 0.47. A yield‐per‐recruit model evaluating spawning potential ratio indicated that a limit of two wild fish would be a sustainable level of exploitation, whereas a six‐wild‐fish limit would result in recruitment overfishing. This research has provided baseline population dynamics of BCT in Bear Lake that will provide insight for future monitoring efforts. Under current conditions, allowing harvest of either origin BCT in Bear Lake would satisfy angler values while ensuring the persistence of an ecologically and recreationally important population.

Miracle of using biofloc technology for fish culture in Bangladesh

Bio-floc technology ensures increased aquaculture intensification and the most efficient use of land, water, and feed resources, all while minimizing environmental impact. Bangladeshi farmers hope that Biofloc technology will provide them with a new horizon in the face of massive climate change. With the introduction of bioflock technology, the cost of fish production for farmers is falling. With the filling of rivers, canals, and beels, the number of houses and factories in Bangladesh is expanding. With all of this in mind, biofloc technology is timeless and sustainable for high-density fish farming in a small area, ensuring safe net food and increased production. As the fishing industry has evolved, more innovative and efficient methods of raising and harvesting fish have been adopted to meet the demands. The Biofloc technology, for example, was developed to cope with wastewater management, sustain biochemical cycles, and preserve aquatic life's nutritional levels. Within a short period of time, this approach has experienced tremendous growth. It is now widely utilized to assure the continued growth of aquatic life and the fishing sector. Its main goal is to convert the hazardous waste material produced in aquatic environments into protein-rich food for the creatures that live there.

The Changing Dynamics of Kazakhstan’s Fisheries Sector: From the Early Soviet Era to the Twenty-First Century

Kazakhstan, a former Soviet republic that is now independent, lies near the center of arid Eurasia. Its sparse hydrographic network includes a small number of large rivers, lakes, and reservoirs, many ponds and smaller streams, as well as littoral zones bordering the Caspian Sea and the Aral Sea. A diverse fisheries sector, initially based on wild fish capture and later including aquaculture, developed in these waters during the Soviet era, when animal agriculture was unable to meet the protein needs of Soviet citizens. The sector, which was originally centered on the Volga–Caspian basin, was tightly managed by Moscow and benefitted from coordinated investments in research, infrastructure, and human resources, as well as policies to increase the consumption of fish products. Independence in 1991 administered a political and economic shock that disrupted these relationships. Kazakhstan’s wild fish harvests plummeted by more than two-thirds, and aquaculture collapsed to just 3% of its previous level. Per capita consumption of fish products also declined, as did processing capacity. Favorable recent policies to define fishing rights, incentivize investments, prevent illegal fishing, and make stocking more effective have helped to reverse these trends and stabilize the sector. Continued recovery will require additional steps to manage water resources sustainably, prioritize the use of water for fish habitats, and minimize the effects of climate change. This comprehensive assessment of Kazakhstan’s fisheries sector over the past century provides the basis to understand how long-term dynamic interactions of the environment with the political economy influence fisheries in Eurasia’s largest country.

Fishing for Litter: Creating an Economic Market for Marine Plastics in a Sustainable Fisheries Model

This paper studies an economy specialized in fisheries facing a rising marine litter problem. We present a dynamic optimization model to explain the mechanism through which marine litter causes inefficiencies in the fishery sector. We do so by investigating the properties of the model when the marine litter externality is internalized through the price of fish. We find that if the marine litter externality is neglected, fish harvest increases, and ocean quality deteriorates. We subsequently explore the possibility of introducing an incentive scheme where marine litter can be traded in a hypothetical market. The introduction of a so-called fishing-for-litter market removes the inefficiencies caused by fishermen neglecting marine litter and provides a direct incentive for them to maximize overall welfare through resource recovery, i.e. by converting plastic waste into a new valuable resource.