World's Fish Research Articles

What to do when invaders are out of control?

AbstractBiological invasions threaten species and ecosystems worldwide. Impacts from invasions are especially prevalent in freshwaters, where managers have struggled to contain the problem. Conventional approaches to managing invaders focus on prevention and control. In practice, these measures have proven to be variably effective. Control or eradication of established invaders is particularly difficult and, even if ecologically feasible, it may not be socially desirable. Here we propose a new alternative to managing invasive species: managing impact modifiers (MIM). The MIM approach focuses on managing impacts, rather than controlling the invader directly. We reviewed the literature for the world's worst invasive fishes in freshwaters to show there is strong evidence to support the potential for MIM as an effective means of managing impacts of invasions. This included evidence pointing to characteristics of the environment or species themselves that modify impacts of invasions. Detail of three case studies reinforces the potential for MIM as a viable option. Although MIM appears promising, effective application could involve significant investment in an information gathering phase to identify impact modifiers and the means to manage them. Accordingly, MIM is best incorporated into management plans that include a strong learning or adaptive component. Ultimately, MIM may be one of the only viable alternatives for managing invasive species that are truly out of control.This article is categorized under: Water and Life > Nature of Freshwater Ecosystems Water and Life > Stresses and Pressures on Ecosystems Water and Life > Conservation, Management, and Awareness

World Fish Migration Day Connects Fish, Rivers, and People – From a One‐Day Event to a Broader Social Movement

Widespread declines in migratory fish highlight the need for increased global efforts to raise awareness of their value and abate threats they face. World Fish Migration Day (WFMD), coordinated by the World Fish Migration Foundation, is a biennial global celebration of open rivers and migratory fish achieved through locally organized events with the common theme of connecting fish, rivers, and people. Since 2014, over 1,200 events have been organized in 80 different countries across all inhabited continents. Here we provide an overview of the WFMD social movement, highlighting its ability to raise awareness surrounding the plight of migratory fish. We provide pertinent case studies to illustrate the creative events held throughout the world intended to build the public and political will to enable protection and restoration of migratory fish populations. From a coordination perspective, there are several key principles that underlay the success of WFMD, including taking an optimistic approach, identifying change‐makers in the community, and carefully timing the growth of the movement. By reflecting on the approach and growth of WFMD, we feel this perspective piece will prove useful to other groups and organizations considering using the power of social movements to achieve common goals related to environmental conservation.

Reduced hypoxia tolerance and survival at elevated temperatures may limit the ability of Amazonian fishes to survive in a warming world

The Amazon basin contains more than 20% of the world's freshwater fishes, many of ecological and economical importance. An increase in temperature of 2.2 to 7 °C is predicted to occur within the next century in the worst-case scenario of climate change predictions, which will likely be associated with an increase in the prevalence and duration of reduced water oxygen levels (hypoxia). Furthermore, there is an increasing frequency of heat waves in the Amazon basin, which exacerbates issues related to temperature and hypoxia. Increases in temperature and hypoxia both constrain an organism's ability to supply oxygen to metabolizing tissues, thus the ability to cope with thermal and hypoxic stress may be correlated. Here, we reveal a positive correlation between acute thermal tolerance and acute hypoxia tolerance amongst 37 Amazonian fish species at the current river temperatures of 28–31 °C. The effects of long-term (10 days or 4 weeks) increases in temperature were investigated in a subset of 13 species and demonstrated that 2 species failed to acclimate and survive at 33 °C, 9 species failed at 35 °C, and only 2 species survived up to 35 °C. Of those that survived long-term exposure to 33 or 35 °C, the majority of the species demonstrated only an improvement in acute thermal tolerance. In contrast, hypoxia tolerance was reduced following acute- and long-term exposure to 33, 35 or 37 °C in all species investigated. The results of this study suggest that many of the fish species that inhabit the Amazon may be at risk during both short- and long-term temperature increases and these risks are exacerbated by the associated environmental hypoxia.

Valorization of By-Products from Commercial Tuna Cannery for New Formulation of Pet’s Food Product: Physicochemical Characterization and DLC Determination

Aida karray*, Ameni ktata, Naima mounedi and Adel Sayari Author Affiliations Laboratoire de Biochimie et de Génie Enzymatique des Lipases, Tunisia Received: July 17, 2020 | Published: July 28, 2020 Corresponding author: Aida Karray, Laboratoire de Biochimie et de Génie Enzymatique des Lipases, ENIS Route de Soukra, université de Sfax-Tunisia DOI: 10.26717/BJSTR.2020.29.004759

Development and application of a sensitive droplet digital PCR (ddPCR) for the detection of infectious spleen and kidney necrosis virus

Infectious spleen and kidney necrosis, caused by the infectious spleen and kidney necrosis virus (ISKNV), has damaged the economy of the world fish industry. Droplet digital PCR (ddPCR) is a novel, sensitive, accurate and absolute quantitation method that does not require a standard curve. In this study, we established a sensitive ddPCR method to rapidly detect and quantify ISKNV DNA. The established method is highly specific to ISKNV and does not cross-react with other iridoviruses. The detection limit of the ddPCR was found to be 1.5 copies/μL, which is much lower than the 34 copies/μL determined for TaqMan real-time PCR (qPCR). This indicated that the sensitivity of the ddPCR assay was 20-fold higher than the sensitivity of the qPCR assay. We explored the feasibility of ddPCR to detect ISKNV from 23 fry samples (mandarin fish, Siniperca chuatsi) and compared the data with qPCR, in terms of sensitivity and accuracy. The detection results for fry samples showed that the positive detection rate of ddPCR (65.22%) was higher than that of qPCR (30.43%). In conclusion, the ddPCR method shows superiority for detection in samples with low ISKNV viral loads, which will facilitate the surveillance of sources and transmission routes of ISKNV.

Correction: Body temperature stability in the whale shark, the world's largest fish.

There was an error in Journal of Experimental Biology (2019) 223, jeb210286 (doi: 10.1242/jeb.210286).The authors inadvertently transposed the explanations of the colours in Fig. 4. HTC models in red are with the rate of temperature change due to internal heat production and those in blue are without the rate of temperature change due to internal heat production. The original and corrected figures and legends are shown here. Both the online full-text and PDF versions of the article have been updated. The authors apologise for this error and any inconvenience it may have caused.

Use of a paraprobiotic and postbiotic feed supplement (HWF™) improves the growth performance, composition and function of gut microbiota in hybrid sturgeon (Acipenser baerii x Acipenser schrenckii)

The contribution of cold water aquaculture for the world fish production is significant. Although sturgeon farming is an important part of China's cold water aquaculture industry, its production is less compared with the current potentiality of the country. There are many reasons for the lower production of cold water fish farming including feed and disease. The aim of the present study was to investigate the effect of a paraprobiotic and postbiotic feed supplement (Herpes Worry Free or HWF™) on the growth, feeding efficiency and gut microbiota balance of hybrid sturgeon. Besides, the effect of sturgeon gut microbiota fed on the diet supplemented with HWF™ on the expression of growth promoter, and immune regulatory genes of germ free (GF) zebrafish was evaluated. Sturgeon were fed for three weeks with HWF™ supplemented or basal diet. At the end of the experiment gut content of sturgeon, fed on either experimental diet was transferred and colonized to GF zebrafish. Sturgeon fed with HWF™ supplemented diet showed significantly higher weight gain rate and lower feed conversion ratio (FCR) as compared with the control (P < 0.05). Compared with the control group, the relative abundance of Firmicutes, were significantly higher in the HWF™ group (P < 0.05), whereas Proteobacteria, Actinobacteria and Chlamydiae were significantly higher in the control group (P < 0.05). Furthermore, at the genus level Clostridium (64.50 ± 5.99%) and Lactococcus (29.5 ± 3.05%) were the most dominant gut bacteria in the HWF™ group and the control group of sturgeon, respectively. The expression of genes related to growth, inflammation and non-specific immunity was significantly upregulated in GF zebrafish colonized with gut microbiota of HWF™ sturgeon group. In conclusion, HWF™ played significant role in growth, feed efficiency and modulation of gut microbiota of sturgeon. The gut microbiota of sturgeon fed on the diet supplemented with HWF™ upregulated the expression of genes related to growth, inflammation and non-specific immunity in GF zebrafish model.

Comparison of growth rates between growth hormone transgenic and selectively-bred domesticated strains of coho salmon (Oncorhynchus kisutch) assessed under different culture conditions

Aquaculture continues to be the fastest-growing animal food sector and accounts for over 50% of the world's fish consumption. This trend is projected to continue, highlighting the role that the aquaculture industry will play in ensuring future global food security. Enhancement of growth rates of fish can optimize aquaculture production and has been achieved through selective breeding programs producing fast-growing domesticated strains, or the development of growth hormone (GH) transgenic strains. Although the ability of selectively-bred domesticated and GH transgenic salmon to outgrow wild-type salmon is well documented, very little research has been reported that directly compares the growth rates of domesticated and GH transgenic strains. The aim of the present study was to compare the growth and survival of selectively-bred domesticated and GH transgenic coho salmon across a range of experimental conditions. We performed four experiments investigating the growth rates of domesticated and GH transgenic salmon by comparing these strains at different developmental stages and under different experimental rearing conditions, as well as under conditions when strains were competing and when they were reared separately. Results from all experiments showed that GH transgenic coho salmon grew faster and to a larger size than the selectively-bred domesticated coho salmon. This was true whether fish groups were reared post-smolt in freshwater or seawater, whether reared together or separately, and whether manipulated to be size-matched at early stages. Thus, GH transgenesis could become a viable complement to selective breeding to produce fast-growing salmon for aquaculture systems. While further research can continue to optimize the development and use of transgenic strains, the data presented here also are important for environmental risk assessments by providing data on the relative fitness and ecological consequences of selectively-bred domesticated and GH transgenic fish should they enter nature.

Analysis of the potential investment attractiveness of the Russian fisheries sector

The fishery complex is an integral part of the national economy. Fish and its processed products are an important part of a balanced and healthy diet. They do not have an alternative replacement, therefore, an efficiently functioning fishery complex plays a big role in ensuring the country's food security and preserves aquatic biological resources. In coastal areas, it is a center of labor force employment, since fishing cannot do without related industries: shipbuilding, production of gear, processing, packaging and transportation of fish products, and therefore it is the core of production and port infrastructure, an incentive for the development of the social sphere and a center attraction of innovation. Currently, the industry is experiencing difficulties associated with both internal and external problems. For further progressive development of the complex, it is necessary to attract investors and financing from various sources for the technical re-equipment of the existing material and technical base, as well as create completely new production assets. A potential investor needs information about the possible pluses and minuses, acquisitions and losses. Therefore, the purpose of this study is to analyze the potential investment attractiveness of the domestic fisheries complex. In theoretical science there is no definition of investment attractiveness. Therefore, when conducting this study, the authors followed the canons of classical economic theory and used comparison methods, historical, deduction and induction, statistical and others. Analyzing the legislation, regulatory documents, scientific articles, monographs, reviews, they came to the following conclusions: the fishery complex has an investment attractiveness under a set of certain conditions. The potential for investment attractiveness of the fishery complex at the present stage is characterized by the presence of a legislative base, increasing demand for fish in world markets and domestically, the stability of the conditions for obtaining quotas for fishing and aquatic biological resources, government participation in co-financing projects, the availability of a state order for finished products, and scientific opportunities capacity etc.

Infection outbreak for Piscinoodinium pillulare in Piaractus brachypomus from aquaculture farm in Brazilian cerrado

The Brazilian aquaculture stands out due to the climate and water availability, and grows along with the world fish production, due especially to the human population growth. The Piaractus spp. shows great participation in production due to the high economic value and productive performance, and because species of the genus are native from South America, including Brazil. Fish are susceptible to parasitizing infection by Piscinoodinium pillulare, a protozoa that causes a disease known as “rust disease”, even more at high population densities and stressful circunstances. An outbreak was observed in a semi intensive aquaculture farming property of Piaractus spp. for preservation, and without any commercial interest, in the municipality of Jataí, Goiás, Brazil, where the main characteristics were: dying fish on the water surface; petechiae in the ventral region of the body, especially in the abdomen; ulcers in the cranial portion; inappetence; and high mortality rates. Three specimens of P. brachypomus were captured and a scraped was performed on the body surface and gills and subjected to microscopic analysis. After microscopic analysis, P. pillulare was observed in slides of all samples. The diagnose was based only on the visualization of P. pillulare trophons (protozoa) in the skin and gills of the fish. The populational and climate conditions that P. brachypomus were exposed at Brazilian Cerrado are equivalent with those required to lead fish to stressful conditions and thus, make them susceptible to parasites infections, such as P. pillulare.

Does phylogeny have an influence on the date of first description? A comparative study of the world's fishes

The process of species description is not random, and understanding the factors that influence when a species is first described (the date of first description, DoFD) allows us to target environments and/or species' traits to increase our knowledge of diversity. Such studies typically correlate species traits (e.g. maximum size, occupational depth) against DoFD, forgetting that species are not statistically independent of each other, owing to the inheritance of shared characteristics. A recent study of extant fishes by Costello et al. (2015) identified depth and geographic range size as the most important (of many) predictors of the DoFD, implying that newly described species will likely occupy restricted areas and occur deep in the water column. However, these authors failed to accommodate for “identity by descent” in their analyses. We correct that oversight here, and conclude that while the adjustments strengthen the associations between the different predictors and the DoFD, the overall affects are minimal and they do not materially change Costello et al.’s (2015) conclusions. This is briefly discussed.

State of Fisheries in Lake Qarun, Egypt: Review Article

This article aims to review the available studies concerning fisheries status of Lake Qarun to suggest an effective strategy for improving its annual total fish catch. Data were collected from the available Publications from GAFRD (General Authority for Fish Resources Development), Central Agency for Public Mobilization and Statistics (CAPMAS), and data collected from reports funded by World Fish Center and FAO were used as data sources of this article. In addition to published papers and reports. Also, from extended visits to Lake Qarun. This article introduces information about study area, environment of Lake Qarun, fishing boats and methods, total fish production, species composition and different biological studies that carried out on Lake Qarun from 1935 till 2019. Recommendations for proper management of this selected sector were recorded in the present study.

Work and struggle of fishing livelihoods in the Delta: Development and ‘new’ change along the Ayeyarwady (Irrawaddy) River, Myanmar

Fishing constitutes a key source of income and food for rural communities worldwide. This is the case in predominantly rural Myanmar (World Fish, 2019), particularly in the Ayeyarwady (Irrawaddy) River Delta. Fishing has long been a central livelihood strategy and valuable source of food security in the Delta, and now also generates a substantial contribution to the gross domestic product. However, the livelihood practices of the fishers, particularly small‐scale fishers, are largely ‘invisible’ in the literature and policy. In this article, we advance understanding of the significant but understudied livelihoods of small‐scale fishers through interviews with fishers and a range of other actors in 2018. Taking a careful examination of the challenges, practices and responses of fishers in the Delta, our research underlines that fishers are important actors in the ‘making’ of the Delta as a geographical scale and concept, yet they are being pushed out of the very landscape they have helped co‐create and have lived in for generations. At this crucial point in Myanmar's development and change, we contend that a better understanding of the livelihoods of fishing households, as some of the nation's most vulnerable, is important for inclusive policy development, economic reforms and research strategy going forward.

Body temperature stability observed in the whale sharks, the world's largest fish.

It is generally assumed that the body temperature of large animals is less likely to change due to their large body size, resulting in a high thermal inertia and a smaller surface area to volume ratio. The goal of this study was to investigate the stability of body temperature in large fish using data from field experiments. We measured the muscle temperatures of free-ranging whale sharks (Rhincodon typus), the largest extant fish globally, and investigated their ectothermic physiology and the stability of their body temperatures. The measured muscle temperature of the whale sharks changed substantially more slowly than the water temperature fluctuations associated with vertical movements, and the whole-body heat-transfer coefficients (HTC) of whale sharks estimated using heat-budget models were lower than those of any other fish species measured to date. The heat-budget models also showed that internal heat production does not contribute to changes in muscle temperature. A comparative analysis showed that the HTC at cooling in various fish species including both ectothermic and endothermic species ranging from 10-4 to 103 kg was proportional to body mass-0.63. This allometry was present regardless of whether the fish were ectothermic or endothermic, and was an extension of the relationship observed in previous studies on small fish. Thus, large fish have the advantage of body temperature stability while moving in environments with large temperature variations. Our results suggest that the large body size of whale sharks aids in preventing a decrease in body temperature during deep excursions to more than 1000 m depths without high metabolic costs of producing heat.

Extinction of one of the world's largest freshwater fishes: Lessons for conserving the endangered Yangtze fauna

The mega river ecosystem of the Yangtze River was once home to diverse aquatic megafauna but is increasingly affected by various anthropogenic stressors that have resulted in continuous loss of biodiversity, such as the probable extinction of Yangtze River Dolphin. The Chinese paddlefish, Psephurus gladius, was one of only two extant members of a relict lineage that was most diverse and widespread 34–75 million years ago. It is also one of the largest freshwater fish species, reaching up to 7 m in length. The Chinese paddlefish was once common in the Yangtze River, with c.25 t being harvested per annum during the 1970s. Populations have, however, declined drastically since the late 1970s as a result of overfishing and habitat fragmentation. Here, a basin-wide capture survey during 2017–2018 found 332 fish species, but did not find a single specimen of Chinese paddlefish. Furthermore, 140 historically reported fish species have not been found and most of them are considered highly endangered. Based on 210 sightings of Chinese paddlefish during the period 1981–2003, we estimated the timing of extinction to be by 2005, and no later than by 2010. In addition, the paddlefish probably became functionally extinct (i.e. it was unable to reproduce) by 1993, before it went extinct. It is likely that the lack of reproduction was among the major causes of extinction. As no individuals exist in captivity, and no living tissues are conserved for potential resurrection, the fish should be considered extinct according to the IUCN Red List criteria. The delayed extinction of Chinese paddlefish resulted from multiple threats, suggesting that optimizing conservation efforts on endangered Yangtze fauna is urgently needed.

World fish market: current trends, state and prospects

The article analyzes the state of the world fish market, problems and prospects for its development in the context of current trends in the world economy. The authors emphasize the importance of the space allocated to the world fish market in solving global problems of our time, such as fighting hunger, ensuring food security, sustainable development, etc. The article presents the current state of world fishing and fish farming, the main producers and exporters, Russia’s place in this market. Reflected issues related to the role of developing countries in this sector of the economy. Conclusions are drawn about the problems and prospects of the world fish market from the point of view of the sustainable development of the world community and the growth of consumption of this food product by the population of the planet.

Prey-size plastics are invading larval fish nurseries

Life for many of the world's marine fish begins at the ocean surface. Ocean conditions dictate food availability and govern survivorship, yet little is known about the habitat preferences of larval fish during this highly vulnerable life-history stage. Here we show that surface slicks, a ubiquitous coastal ocean convergence feature, are important nurseries for larval fish from many ocean habitats at ecosystem scales. Slicks had higher densities of marine phytoplankton (1.7-fold), zooplankton (larval fish prey; 3.7-fold), and larval fish (8.1-fold) than nearby ambient waters across our study region in Hawai'i. Slicks contained larger, more well-developed individuals with competent swimming abilities compared to ambient waters, suggesting a physiological benefit to increased prey resources. Slicks also disproportionately accumulated prey-size plastics, resulting in a 60-fold higher ratio of plastics to larval fish prey than nearby waters. Dissections of hundreds of larval fish found that 8.6% of individuals in slicks had ingested plastics, a 2.3-fold higher occurrence than larval fish from ambient waters. Plastics were found in 7 of 8 families dissected, including swordfish (Xiphiidae), a commercially targeted species, and flying fish (Exocoetidae), a principal prey item for tuna and seabirds. Scaling up across an ∼1,000 km2 coastal ecosystem in Hawai'i revealed slicks occupied only 8.3% of ocean surface habitat but contained 42.3% of all neustonic larval fish and 91.8% of all floating plastics. The ingestion of plastics by larval fish could reduce survivorship, compounding threats to fisheries productivity posed by overfishing, climate change, and habitat loss.

Numerical analysis of local and global responses of an offshore fish farm subjected to ship impacts

Due to limited nearshore areas and great impact to local ecosystems, the aquaculture industry is moving the fish farms into more exposed sea regions where the environmental conditions are much more severe. Like other offshore installations operating at sea, fish cages are also exposed to the risk of collisions from attendant or visiting vessels. This paper evaluates the structural strength of the world's first offshore fish farm operating in Norway subjected to supply vessel collisions by the use of nonlinear finite element simulations. The fish cage is a semi-submersible floating structure consisting of ring-stiffened columns connected by braces. A standard 7500-ton supply vessel is used as the striking vessel. Both local shell deformation analysis using LS-DYNA and beam deformation analysis using USFOS are carried out. In the local shell analysis, collision scenarios with both decoupled and coupled methods are simulated for several representative impact locations. The decoupled model adopts prescribed paths for ship motions, while in the coupled model, the ship motions are calculated based on hydrodynamic forces from linear potential theory as well as inertia and collision forces. In the global beam-column analysis in USFOS, the force-deformation curves of the supply vessel from local shell analysis are used as the input. The resulting damage and energy absorption are compared with those from local shell simulations. The results are discussed with respect to the impact resistance, energy absorption and structural damage.

Pysicochemical Characterization of Nano Calcium phosphate from Milkfish's (Chanos - Chanos Forks) Bone Flour in Duration of Autoclaving and Boiling Time Different

According to the Food and Agriculture Organization in 2018, milkfish 1,188,000 tons (2016) or 2% of the world's total fish (2016) (The State of World Fisheries and Agriculture, 2018). South Sulawesi milkfish production is the highest in Indonesia. Milkfish production in 2016, to 127,434.1 tons (Anonymous, 2018). Milkfish is a fishery commodity in Pangkep Regency, in 2016 has increased by 28,759 tons (Anonymous, 2018), an increase in fish consumption it will also increase of milkfish bone waste. The use of milkfish bone waste as a source of calcium is an alternative provide a calcium-rich food source. The purpose of this research is to study the physicochemical of milkfish bone calcium phosphate with in duration of autoclaving and boiling time differently. The treatment are in duration of autoclaving (A) A1 = 1,5 , A2 = 2, and A3 = 2,5 hours, and boiling time (B) B1 = 30 , B2 = 60 and B3 = 90 minute. The design used is complete randomized design with two factors, consist of three level. Each treatment was repeated three times. The data analysis by variance analysis using SPSS V. 21 software. The parameters measured are yield, water, ash, protein, fat, calcium and phosphorus. Milkfish bone in this study contained the highest calcium 41.87% and phosphorus 25.86% obtained from a combination of 2.5 hours autoclaving and boiling length 90 minutes. Yield 36.59%, moisture 5.22%, ash 77.87%, protein 25.13%, and fat content 4.01%.

Economics of Aquaculture Policy and Regulation

Since the Blue Revolution began in the late 1960s, global aquaculture production has grown rapidly. Aquaculture now accounts for over half of the world's fish for direct human consumption and is expected to approach two-thirds by 2030. With aquaculture's growth, a number of high-profile concerns have arisen, including pollution, feeding practices, disease management and antibiotic use, habitat use, non-native species, food safety, fraud, animal welfare, impacts on traditional wild fisheries, access to water and space, market competition, and genetics. Managing these concerns requires thoughtful and well-designed policies and regulations. This manuscript reviews the contributions natural resource economics has made to evaluating aquaculture policy and regulation. Despite their valuable contributions, however, economists have been largely underrepresented in the debate. The primary influencers of aquaculture policies and regulations have been traditional fisheries managers, environmental groups, and natural scientists. We identify many important areas that should be more thoroughly addressed by economists.