Fish Protection Research Articles

Analysis of the trade-off between hydroelectricity generation and ecological protection from the perspective of eco-efficiency in Southwest China

Driven by the global net-zero carbon emission goal, even though the impact of hydropower on river ecosystems cannot be ignored, hydropower scale and intensity will be expanded in Southwest China (SC). Therefore, the trade-off between hydroelectricity generation and ecological protection remains an issue requiring urgent attention at the moment. This paper proposes an eco-efficiency (EE) indicator system of hydropower adopting the water consumption of hydropower product (PWC), labor, and capital as inputs and the power generation, ecological flow deviation (EFD) as outputs and then explores the factors influencing the EE value of hydropower in SC. The results indicate that (1) The EE incorporates the impact of each plant on fish, provides decision support for hydropower development planning and serves as the foundation for eco-dispatch operations. (2) Hydropower generation affects fish reproduction in SC, and the EE value of the Wu River is relatively low. (3) The scale of power generation and degree of fish protection are two significant factors that can increase the EE value of hydropower. To compensate for plant inadequacies in these two aspects, equivalent changes in hydropower planning and eco-dispatch operations should be implemented.

Optimization principles for inlet portal designs of gravity fish outlets of fish protection structures of water intake facilities

Prevention of juvenile fish from entering water intakes for various economic purposes utilizing a fish protection structure design is associated with the need to divert protected juvenile fish (fish outlet) to a safe place of a water source while maintaining its viability. The development of principles for selecting fish outlet structural elements is based on the existing hydraulic and biological requirements to ensure the effective movement of fish outside the influence of water intake. For the conditions of an open gravity fish outlet, the features of functioning and possible ways of its central element optimization are considered: the inlet part, the receiving section, and the transition section. Based on the analysis of the most characteristic features of the flow formation in the zone of the water intake influence, the conditions for the layout of the inlet part of the fish outlet are determined. The technical solution of the receiving section is based on the design features and calculation of the hydraulic parameters of the pressure nozzles. Moreover, the structural elements of the receiving section should be a sequential combination of nozzles from the functional aspect: a conical confuser – a cylindrical nozzle- conical diffuser, and the hydraulic conditions should correspond to biological requirements and ensure a flowing current that is safe for fish; the analysis of hydraulic and technical conditions of fish outlet is given. From the standpoint of modern hydraulic and biological requirements and the knowledge of fish behavior patterns, the optimal design is proposed for the design of the inlet portal of an open gravity fish outlet of the fish protection structure of the water intake facility.

Питание окуневых рыб (Percidae) в малом озере бассейна Онежского озера

The article s focuses on studying the fish nutrition, which is one of the ways to identify the patterns of fish onto- and phylogenesis, as well as the patterns of fish abundance and using food resources in the water bodies. Nutrition determines the key physiological and biochemical reactions in the fish body in a qualitative and quantitative sense, which finally affects the growth of both individual organisms and the entire population. The results of these studies are of practical importance in the work of fish protection authorities. Information about the fish feeding in the small water bodies of Lake Onega basin is practically absent in the literature. There are presented the results of the studies carried out within the framework of forecasting and economic and contractual issues of the Northern Water Problems Institute of the Karelian Research Centre of the Russian Academy of Sciences (NWPI KarRC RAS) and Petrozavodsk State University (PetrSU) on assessing the nutrition of perch species (perch, ruff) in the lakes of the Konchezero group (South Karelia) - the lower reaches of the river Shuya belonging to the catchment area of Lake Onega. The work was carried out by the specialists of the NWPI KarRC RAS in 2018–2020. The main hydrological and ichthyological indicators of Lake Urozero have been studied. It is found that in the diet of perch in Lake Urosero there appear larvae Chironomidae, Ephemeroptera and aerial insects, and the latter having the maximum index of relative importance. The diet of ruff caught in Lake Urozero differs widely: along with benthic organisms fish eggs were also present. Ruff’s nutrition is more abundant: the index of filling its stomach averages 225.3 0/000 against 51.2 0/000 in perch. Perch longer than 13 cm is a typical ichthyophag in Lake Urosero. It is typical for the Karelian lakes that the transition of perch to predation is ob-served when reaching the size (on average) 15 cm.

An integrated environmental risk assessment framework for coal-fired power plants: A fuzzy logic approach.

This study quantifies the environmental risk of a coal-fired thermal power plant during operation by using environmental monitoring data, site surveys, and documented evidence. The following criteria are assessed: emissions (CO, SO2 , NOx , PM10 ), impact on aquatic ecosystem (fish protection at cooling water intake and cooling water discharge temperature), and waste management (fly ash and bottom ash). Fuzzy sets were defined for each criterion, taking environmental regulatory context as an expert judgment. A survey was conducted with multiple stakeholders to determine the relative importance of risk factors. The survey results showed that the most concerned risks are SO2 and NOx emissions. The proposed method estimates the risk of each environmental criterion separately and then accumulates them into an environmental risk index (ERI). Accordingly, we assessed the Catalagzi coal-fired power plant, which has been in operation on the Black Sea coast in northwestern Turkey. For this case study, the ERI resulted in a value of 0.78 (on a scale of 0-1), showing high environmental risk to the facility. Moreover, the applicability of the proposed framework was tested in several existing coal-fired power plants using simultaneous measurements. All studied coal-fired power plants in Turkey have unacceptable pollutants (PM10 , SO2 , and NOx ) concentration levels indicating high health risk potential. The application of the integrated environmental risk assessment framework showed that new environmental regulations are needed in Turkey to specify more strict emission limits and to monitor CO2 , fine particulate matter emissions, cooling water discharge, and fish protection at cooling water intake.

Retrofitting of Existing Bar Racks with Electrodes for Fish Protection—An Experimental Study Assessing the Effectiveness for a Pilot Site

Downstream-migrating fish in rivers tend to follow the main current, and are in danger of swimming through the turbines at run-of-river hydropower plants, possibly causing high mortality rates. To avoid these losses, fish must be prevented from entering the turbines. Most existing vertical bar rack systems (used for turbine protection) however usually do not ensure proper fish protection due to large bar spacings. FishProtector technology enables the retrofitting of existing bar racks (i.e., the mechanical barrier) with additional electrodes to create a hybrid barrier. The induced electric field in the water aims to create a behavioral barrier to prevent fish passage through the bar rack. In this study, ethohydraulic experiments to investigate the effect of such a behavioral barrier on fish were performed. In detail, the fish-protection rate at a bar rack with a bar spacing of 30 mm was tested in five different scenarios: (i) a bar rack without electrodes (reference), and four electrified setups with electrode spacings of (ii) 80 mm, (iii) 120 mm, (iv) 160 mm, and (v) 200 mm. A flow velocity of 0.23 m/s was chosen to replicate the situation at a planned pilot site. The study was conducted in an outdoor laboratory flume using small fish of several local riverine species, mostly cyprinids and minnows. The results show that the mean fish-protection rate in the experiments could be increased from 62% in the reference setup up to 96% in the electrified setups.

Protection and guidance of downstream moving fish with horizontal bar rack bypass systems

During their life cycle, fish carry out distinct movements within rivers and migrate upstream and downstream to reproduce, to feed, and to shelter in refuge habitats. During downstream movements, they can incur severe injuries that may be lethal directly or indirectly over time when passing through hydropower plants or when being entrained at other water intakes. Horizontal bar rack bypass systems are a state-of-the-art technology to protect and guide downstream moving fish towards a reasonably safe corridor around water intakes. They have been in operation at multiple hydropower plants for more than a decade, but only little is known about the potential fish protection and guidance efficiencies and the fine scale reactions of different fish species when encountering such racks. To resolve this, systematic live fish laboratory tests were conducted under various hydraulic conditions involving a diverse assemblage of riverine fish species differing in their swimming behavior and morphology. Six riverine species, namely spirlin (Alburnoides bipunctatus), barbel (Barbus barbus), nase (Chondrostoma nasus), brown trout (Salmo trutta fario), Atlantic salmon (Salmo salar), and European eel (Anguilla anguilla) were tested with a rack consisting of foil-shaped bars, clear bar spacings of 15 and 20 mm, a horizontal rack angle of 30° to the flow direction, and a full depth open channel bypass. Variations in fish behavior were observed between different species and hydraulic conditions, but the results suggest that the guidance and protection efficiencies primarily depend on the ratio of the fish width to the clear bar spacing. Larger fish were well protected by the horizontal bar rack, while smaller fish frequently passed through the rack. New equations are proposed to estimate the protection and guidance efficiencies as a function of the clear bar spacing and the fish species' biometry, which is highly relevant to assess the effect of horizontal bar racks as fish protection measures prior to installation.

Proactively averting the collapse of Amazon fisheries based on three migratory flagship species.

Migratory species are the most important commercial fishes in the Amazon. They are also now the most threatened directly by some combination of overfishing, floodplain deforestation, and dam construction. Limited governmental monitoring and implemented regulations impede adequate management of the fisheries at adequate scale. We summarize the current stock status of the three most heavily exploited long-distance migratory species, which are two goliath catfishes (Brachyplatystoma rousseauxii and B. vaillantii) and the characiform Colossoma macropomum. In addition, we analyze impacts beyond overfishing on these species. Our results indicate: (i) the overfishing trends for these important species are either ominous or indicate the verge of collapse of the commercial fisheries based on them, and (ii) a dangerous synergy between overfishing, hydroelectric dams, and floodplain deforestation further challenge fisheries management of migratory species in the Amazon. We propose eight direct governmental actions as a proactive approach that addresses the main impacts on the fisheries. We consider that the most practical way to assess and manage overfishing of migratory species in the short run in an area as large as the main commercial fishing area in the Amazon is at market sites where enforced regulations can control fish catch. The management of the three species considered here has implications beyond just their sustainability. Their management would represent a paradigm shift where the governments assume their legal responsibilities in fishery management. These responsibilities include regulation enforcement, data collecting, inter-jurisdictional cooperation to protect migratory species at realistic life history scales, mitigation of the Madeira dams to assure goliath catfish passage to the largest western headwater region, and recognition of monitoring and managing wetland deforestation for the protection of fish and other aquatic and terrestrial biodiversity.

A Physical and Behavioral Barrier for Enhancing Fish Downstream Migration at Hydropower Dams: The Flexible FishProtector

Fish protection at hydropower plants is important for the sustainability of hosting ecosystems and the acceptance of hydropower. On their way downstream, fish are exposed to hydropower plants and various related negative effects, ranging from a delay in downstream movement to being injured or killed by a turbine. Understanding the behavior of fish in close proximity to protection devices is essential in order to establish efficient fish protection facilities. In this study, physical (horizontal steel cables) and behavioral barriers (electric field) for fish protection were developed (Flexible FishProtector) and their effectiveness was investigated. The behavior of brown trout (Salmo trutta fario), rainbow trout (Oncorhynchus mykiss), grayling (Thymallus thymallus) and chub (Squalius cephalus) at the Flexible FishProtector was analyzed using video evaluation. The experimental setup was a non-scaled section model of a runoff river power plant. The used electric field induced a flight reaction at a corresponding distance to the Flexible FishProtector that significantly increased the protection rate. Furthermore, an increase in guiding efficiency was achieved with the use of a physical as well as a physical and behavioral barrier, supporting safe downstream migration with the narrower cable clearance (30 mm versus 60 mm).

Об использовании рыбозащитных сооружений в условиях водоприемных ковшей

The purpose of the study is to assess the conditions forensuring the protection of fish from entering water intakes when using water intake buckets. The article analyzes the possibilities of protecting fish in conditions of use of water intake buckets, which, depending on the hydrological characteristics of the water source, taking into account changes in water levels and flow rates, as well as water protection requirements and sanitary and epidemiological conditions, provide the required conditions for water supply. The possibilities of ensuring the protection of fish when using water intake buckets are considered on the example of three designs from different water sources, of which only in one condition the protection of fish can be assessed as satisfactory. At the same time, the need for additional implementation of measures to remove fi sh from the bucket is a determining condition for the success of their conservation. However, this presents the greatest difficulty, which is currently not solved in the layout of bucket water intakes, including foreign practice. As possible fish protection devices for the conditions of water intake buckets, the designs are considered which use the effect of hydraulic flushing and diversion, in particular filtering, louvering, etc. Based on the results of the analysis of hydraulic conditions in the bucket, a scheme for the formation of a fish diverting stream with subsequent movement along the fish drainage tract beyond the influence of the water intake bucket is considered.

ОСОБЕННОСТИ И АНАЛИЗ ИССЛЕДОВАНИЙ РЫБОЗАЩИТНОГО КОМПЛЕКСА ДЛЯ ВОДОПРИЕМНИКОВ КРУПНЫХ ВЫСОКОНАПОРНЫХ ГИДРОЭЛЕКТРОСТАНЦИЙ

Development of effective fish protection measures at water intakes is one of the main directions of fish resources conservation and reproduction in inland water bodies of the country. Its complexity is associated with the involvement of many related disciplines: ichthyology, physiology, hydrobiology, ecology, hydraulics, hydrology, etc. In the process of solving the problem of standardization of information to be used for creating mathematical models for forecasting potential impact of water intakes with fish protection on aquatic ecosystem. The article gives a review of the research on the technology of aquatic bioresources (ABR) conservation, conducted by JSC «Institute Hydroproject» (Moscow) together with LLC «Hydrotechnika» (Sochi), the basic provisions of modeling methodology are considered; the results of mathematical modeling of currents in the upstream in the area of hydraulic units, spillways and rockfi ll dam at Boguchanskaya HPP; results of experimental studies of stream generators and biohydraulic modeling. The assessment of the conducted research is given.

Use of acoustic telemetry to evaluate fish movement, habitat use, and protection effectiveness of a coral reef no-take zone (NTZ) in Brazil

Movement is a key factor that shapes the distribution and structure of fish populations and influences the extent of the benefits provided by conservation and management measures, such as the implementation of marine no-take zones (NTZs). We used visual surveys and acoustic telemetry to investigate density and movement of 2 Brazilian endemic and highly targeted reef fish species inside and outside a coral reef NTZ, and subsequently inferred the effectiveness of the NTZ for protecting these species. To do so, visual surveys were performed on protected and unprotected reefs between 2016 and 2017. Moreover, 20 gray parrotfish Sparisoma axillare and 9 Brazilian snapper Lutjanus alexandrei were tagged with acoustic transmitters and passively monitored from December 2016 to October 2017. For both species, fish densities were significantly higher within the NTZ. Also, both species presented a high residence index over the short term, indicating they were full-time residents of the monitored area until detections were permanently lost. The absence of detections may indicate relocation to deeper reefs, predation, or fishing mortality when fish left the NTZ. Home ranges were small (0.10 to 0.45 km2), and both species presented spatially segregated subgroups within the populations. On average, the percentage of the home ranges within the NTZ was 88% for S. axillare and 95% for L. alexandrei. The results showed that small NTZs that are important to part of the life cycle of a target species are an effective measure to conserve reef fish populations, and also highlight the importance of fisheries management outside NTZs.

Some aspects of organizing the protection of fish from going into water intake facilities

The results of laboratory studies of water intake structures of engineering-ecological type with devices that prevent fi sh from entering the water intake windows are presented. When they work in the water intake zone, optimal hydraulic conditions are created that contribute to the guaranteed fish diversion. Three versions of the protective device were studied: single heads of cylindrical and bull types, as well as a structure with a series of fi ve bull-type heads installed obliquely in the direction of the flow. Studies of the influence of the hydraulic structure and hydrodynamic characteristics of the fl ow on the entry of fish into the water intake were carried out in a mirror tray with a change in the water intake in the range of 17…52 l/s. The experiments involved juveniles of different breeds with a size of 35…45 mm. The kinematics turned out to be partly expected: with an increase in water withdrawal, the degree of flow concentration increased. Experiments have shown that when installing a series of water intake heads, the possibility of fish getting into the zone of water intake windows increases compared with the installation of single heads. When placing single heads, the maximum negative velocities in the zone of the water intake window and the distance at which they are observed behind the bull head are signifi cantly higher. As a result of the analysis of hydro biological studies, it was found that the capaability of fish to leave the zone of influence of water intake decreases sharply with an increase in the amount of water withdrawal (outcome III). With a single cylindrical head, the intensity of pressure pulsation is approximately by 18% greater than with a bull head. A series of water intake heads arranged obliquely in a checkered order has higher fish protection properties.

Fish Skin and Gill Mucus: A Source of Metabolites for Non-Invasive Health Monitoring and Research.

Mucous membranes such as the gill and skin mucosa in fish protect them against a multitude of environmental factors. At the same time, changes in the molecular composition of mucus may provide valuable information about the interaction of the fish with their environment, as well as their health and welfare. In this study, the metabolite profiles of the plasma, skin and gill mucus of freshwater Atlantic salmon (Salmo salar) were compared using liquid chromatography coupled to high-resolution mass spectrometry (LC-HRMS). Several normalization procedures aimed to reduce unwanted variation in the untargeted data were tested. In addition, the basal metabolism of skin and gills, and the impact of the anesthetic benzocaine for euthanisation were studied. For targeted metabolomics, the commercial AbsoluteIDQ p400 HR kit was used to evaluate the potential differences in metabolic composition in epidermal mucus as compared to the plasma. The targeted metabolomics data showed a high level of correlation between different types of biological fluids from the same individual, indicating that mucus metabolite composition could be used for fish health monitoring and research.

Effects of heat shock protein inducer on Hsp70 gene expression and immune parameters during Streptococcus iniae infection in a Persian sturgeon fry.

Heat shock proteins (HSPs) as stress-related factors play a fundamental role in innate and adaptive immune responses in fish, which can be considered as strong candidates for the development of new methods for fish disease prevention. It has been proven that Pro-Tex® as a heat shock protein inducer (HSPi) reduces harmful effects of cellular stress by increasing the Hsp70 protein production. We evaluated the effects of Pro-Tex® as an HSPi in a Persian sturgeon, (Acipenser persicus) exposed to a pathogenic bacterium. Therefore, A. persicus fries were pre-treated with 25.00, 50.00 and 100 mg L-1 of Pro-Tex® and then, injected with Streptococcus iniae ATCC29178. The Hsp70 gene expressions were determined in various organs including liver, gill and intestine and lysozyme (LYZ) activities along with supplemental levels of complement component 3 (C3) and immunoglobulin M (IgM) were also determined in sturgeon blood in days 3 and 7 after infection. Expression of Hsp70 gene was increased during the first three days of infection and then, it was found to be down-regulated during the infection process. Also, levels of LYZ activity, C3 and IgM increased in a concentration-dependent manner; but these parameters decreased after 7 days. Our data suggest that induction of Hsp70 is a promising approach in modulation of immune response in A. persicus and it might be employed to confer protection in fish against bacterial infections.

The use of umbrella fish species to provide a more comprehensive approach for freshwater conservation management

Abstract Where freshwater species populations are in decline, conservation management requires rapid, cost‐effective approaches to develop recommendations, particularly at broad geographical scales or where species‐specific information is lacking. The umbrella species approach, typically applied to terrestrial taxa, is one potentially useful option to inform large‐scale freshwater management efforts. A quantitative, integrated approach is proposed for selecting suites of umbrella fish species over diverse spatial scales using a combination of species ranges, life‐history traits, and species vulnerability scores. The approach also uses expert opinion to validate methods and results. This approach was applied to native fishes in California, and results for two river basins are explored in the context of instream flow management. These examples illustrate how the results could help address two common instream flow management challenges in California: (i) the lack of information related to species‐specific flow requirements in basins with many species; and (ii) the need to move beyond a single species approach to flow management. In addition, the results indicate that the protection of native fishes in California would provide co‐benefits for other aquatic and riparian taxa. A key benefit of this approach is that the data used to select suites of umbrella species (e.g. species ranges, life‐history traits, climate vulnerabilities) are widely available at varying degrees of specificity for most freshwater fishes. Therefore, this flexible approach could be applied in other regions to aid managers in making freshwater conservation decisions, such as for instream flow strategies, in an efficient and cost‐effective manner.

The time-area fishing closure impacts on fish stock; Qiantang River before and after a four-month fishing closure

Fishing closures, commonly used to manage fisheries’ catch, involve temporarily closing a body of water to particular fishing gears to control fishing effort and protect feeding and spawning areas. In recent years in Qiantang River of China, with the socio-economic development, protection of fish stock has become increasingly urgent. The year 2019 was the first year that Qiantang River was included in the unified fishing ban system for the south of Yangtze River basin. Here, fish captures and hydroacoustic surveys were carried out in the research area of Qiantang River in order to present comparative descriptions of the dominant fish species, the temporal changes of fish size, density, biomass, and distribution affected by the four-month fishing closure in 2019. The results showed that Pseudobrama simoni (Bleeker, 1864) was the most dominant species both before and after the closure by using the traditional capture method. The mean target strength (TS) of overall fish after closure was –50.28 ± 0.19 dB, which was lower than that before, resulting in a significantly shorter derived mean length (13.42 ± 0.74 cm). The mean fish density and calculated biomass after closure were both significantly higher than that before it. More than 50% of fish species were distributed in the water of 5–20 m depth after the closure, which likely occurred in water deeper than 20 m before. Meanwhile, fewer outliers were found in different depth categories after closure. It is concluded that the four-month closure in 2019 had a positive effect on fish size, density, and biomass, leading to protection of pelagic fishes and a more even distribution of fish.

Foundation and Prospects of Wild Population Reconstruction of Acipenser dabryanus

Acipenser dabryanus is an endemic fish inhabiting the upper reaches of the Yangtze River in China. It is classified as a first-class nationally protected animal in China and is listed in the International Union for Conservation of Nature (IUCN) Red List of Critically Endangered Species (CR). Recently, there has been a decrease in natural reproduction of A. dabryanus, and the wild population is almost extinct. This paper summarizes the changes observed in the natural population of A.dabryanus and the factors leading to its endangerment. Based on the process of artificial propagation and achievement of relevant protection goals, this paper presents the concept and technical framework for reconstruction of the wild population of A. dabryanus. In addition, by comprehensively reviewing the research findings and existing problems in the resource protection and monitoring of A. dabryanus in recent years, we assessed the possibility of wild population reconstruction and resource restoration for A. dabryanus. Reconstruction and restoration measures for the wild population of A. dabryanus are proposed, with the aim of providing a scientific basis for the reconstruction of the natural population and the improvement and restoration of critical habitat of this species. Furthermore, it is hoped that this paper will serve as a reference for the protection and restoration of other endangered fishes.

New Scientific Information Can Help to Inform the Evaluation of EU Deep-sea Fisheries Regulations

Abstract The European Union’s deep-sea fisheries regulations (Regulation (EU) No. 2016/2336) established obligations to manage deep-sea fisheries and to protect vulnerable marine ecosystems (VMEs). The European Commission is scheduled to complete a review of the regulations in 2021, providing an opportunity for new scientific information to be incorporated into the implementation of the regulations. Here, we summarise research outputs from the EU-funded Horizon 2020 ATLAS Project and explain their relevance to the regulation of deep-sea fisheries in EU waters. ATLAS research has increased our understanding of the distribution of VMEs and their importance in terms of ecosystem functioning. ATLAS research has also highlighted the utility of molecular techniques to understand fish population structure and the potential for habitat suitability models to help incorporate climate change into decision-making. Building on these scientific advances, we provide recommendations to help increase the effectiveness of management measures to conserve deep-sea fish stocks and protect VMEs.

Analyses of Protection and Conservation According to the Fish Act 1950 in Bangladesh’s Kaptai Lake Fisheries Management

Kaptai Lake (KL), the largest inland watershed in Bangladesh (ca. 700 km2) and one of Southeast Asia’s largest artificial reservoirs, features an abundant variety of indigenous fishery species. Moreover, it provides a plethora of ecological benefits to society. Nevertheless, the KL is suffering from multidimensional natural and anthropogenic stressors that threaten these wetlands’ sustainability. Though the legal framework assures sustainable conservation of fisheries resources, the implementation scenarios of fisheries laws, regulations, and policies in the KL wetland are insufficient. This study aimed at assessing the fisher’s perception of the regulation implementation efficiency of the Protection and Conservation Fish Act of 1950, while analyzing the effectiveness of the legal framework in the context of biodiversity conservation and the management sustainability of KL. By integrating qualitative and quantitative data collected through participatory Rural Appraisal (PRA) tools viz. 225 interviews with fishers, four focus group discussions, and 12 key informant interviews, the investigation was performed in four selected areas in KL. The findings show that fishers routinely disregard laws and restrictions of the Protection and Conservation of Fish Act 1950 due to various socioeconomic and political forces. Although the annual fish harvest rate from KL appears to be increasing, the lake is losing its charismatic biological diversity primarily due to inappropriate and ineffective enforcement of fishing regulations. Many fishers believe that they still follow the act’s significant laws and regulations while being involved in several destructive and prohibited fishing practices. There is a link between community awareness, the scope of the act’s provisions, the effectiveness of its enforcement, and the strength of its execution. One of the leading causes of biodiversity loss in the KL is inadequate and ineffective fishing regulations. Improvement in the enforcement of the fishing act may be the prominent option to ensure better biodiversity conservation and sustainable management of this wetland. This result calls for functional and policy attention to revising the regulations to account for socioeconomic and political elements contributing to environmental degradation. This study also highlights the urgent need for transdisciplinary collaboration initiatives and synchronous cooperation among the agencies in order to effectively implement the fishing laws and contribute to better conservation and sustainability of the Kaptai lake fisheries resources.

Protection of Teleost Fish against Infectious Diseases through Oral Administration of Vaccines: Update 2021.

Immersion and intraperitoneal injection are the two most common methods used for the vaccination of fish. Because both methods require that fish are handled and thereby stressed, oral administration of vaccines as feed supplements is desirable. In addition, in terms of revaccination (boosting) of adult fish held in net pens, oral administration of vaccines is probably the only feasible method to obtain proper protection against diseases over long periods of time. Oral vaccination is considered a suitable method for mass immunization of large and stress-sensitive fish populations. Moreover, oral vaccines may preferably induce mucosal immunity, which is especially important to fish. Experimental oral vaccine formulations include both non-encapsulated and encapsulated antigens, viruses and bacteria. To develop an effective oral vaccine, the desired antigens must be protected against the harsh environments in the stomach and gut so they can remain intact when they reach the lower gut/intestine where they normally are absorbed and transported to immune cells. The most commonly used encapsulation method is the use of alginate microspheres that can effectively deliver vaccines to the intestine without degradation. Other encapsulation methods include chitosan encapsulation, poly D,L-lactide-co-glycolic acid and liposome encapsulation. Only a few commercial oral vaccines are available on the market, including those against infectious pancreatic necrosis virus (IPNV), Spring viremia carp virus (SVCV), infectious salmon anaemia virus (ISAV) and Piscirickettsia salmonis. This review highlights recent developments of oral vaccination in teleost fish.