Freshwater Fish Species Research Articles

Lake Malawi/Niassa/Nyasa basin: Status, challenges, and research needs

Lake Malawi/Niassa/Nyasa (LMNN) is one of the most important and third-largest African Great Lakes. It has the largest number of freshwater fish species in the world, most of which are endemic. Current estimates put the number of fish species in the range of 800–1000. The riparian countries of Malawi, Mozambique and Tanzania enjoy enormous benefits that accrue from the ecosystem services that the lake provides. However, LMNN is experiencing severe adverse impacts resulting from anthropogenic and climatic stressors, leading to increased sediment and nutrient loading. This observation motivated this study to identify existing research gaps to enhance the lake’s sustainable management. Specifically, the assessment focused on three key issues identified and prioritised by the LMNN Basin Fisheries and Aquaculture Network (LMNNBFAN), namely: fishery health, invasive species, and climate change. Data collection involved stakeholder consultations, field surveys, and desk reviews. Recommendations from study findings, that would create a conducive environment for the sustainable management of the lake, have been grouped into four main categories: research needs, infrastructure development, human capacity building and funding.

Purification and characterization of amylases from three freshwater fish species providing new insight application as enzyme molecular markers for zymography.

Purification of amylases from digestive tracts of three freshwater fish species with Q-Sepharose Fast Flow and Sephacryl S-200 columns displayed two isoforms of amylases from Osteochilus hasselti (O1, O2) and three isoforms of those from both Hampala dispar (UB, H1, H2) and Puntioplites proctozystron (P1, P2, P3). The optimum pH values displayed at 7.0 and 8.0, while the optimum temperatures revealed at 40 and 50°C. Almost isoenzyme activities were activated by NaCl and CaCl2, whereas EDTA and SDS strongly inhibited all enzymatic activities. Verification with an atomic absorption spectrophotometry exhibited the presence of Ca2+ ions in the range of 0.02-13.53ppm per mg protein indicating that amylases are Ca2+ dependent. Molecular weight analysis revealed 12 to 147kDa. The UB, O1, and H2 amylases with appropriate molecular masses of 64, 49, and 25kDa validated with LC-MS/MS were selected. Three certain enzymes revealed high stability in a sample buffer after five cycles of freeze-thawing process upon storage at - 20°C for 12weeks. No protein degradation was observed on polyacrylamide gel, and the enzymes still displayed sharp and clear bands on zymograms. The result suggested that the purified fish amylases, which expressed high activities and stabilities, were potentially used as enzyme molecular weight markers for zymography.

Experimental assessment of the effect of different types of salt and temperature on the survival of the larval stage of eurasian perch Perca fluviatilis Linnaeus, 1758

Salinization of freshwaters is a serious problem leading to a decrease in biodiversity and degradation of aquatic ecosystems. In conditions of climate warming, the toxic effect of salinization can increase. The aim of this study was an experimental assessment of the survival of the pre-larvae of the Eurasian perch Perca fluviatilis under conditions of different concentration of two types of salt (salt mining wastes and sodium chloride), and also under two temperature regimes. We found that under temperature conditions of 8–15 ° C, the mortality of pre-larvae was significantly lower compared to the values obtained with an increase in temperature by 5 °C. The tolerance limit (LC50 ) under exposition to salts for 24 hours was a mineralization value equal to 9.8 g/l and 8.7 g/l under an exposition of 72 hours. There were no significant differences between the two types of salts — salt mining wastes and sodium chloride in terms of LC50. There were also no significant differences in the time of death of 100 and 50% of the tested prelarvae. At the same time, a higher mortality of pre-larvae was revealed in solution of salt-mining wastes at concentrations of 7 and 8 g/l. At concentrations above 9 g/l, the opposite trend was observed — a greater mortality rate was found in sodium chloride solution. For both types of salts, a greater survival rate of prelarvae was revealed at a salt concentration of 8 g/l compared to a concentration of 7 g/l, which requires more detailed studies. These results are important for understanding the limits of tolerance to salinity in the larval stage of development of one of the most widespread ecologically flexible freshwater fish species. The relevance of the study is determined by current trends in climate change and the increasing level of salinization of boreal freshwaters as a result of salt pollution.

Aeromonashydrophila infection in tilapia triggers changes in the microbiota composition of fish internal organs.

Aeromonas hydrophila is a major pathogenic species that causes mass mortality in various freshwater fish species including hybrid tilapia, the main fish species in Israeli aquaculture. Our hypothesis was that A. hydrophila infection may cause changes in the microbiota composition of fish internal organs, and therefore we aimed to study the effect of A. hydrophila infection by injection or by net handling on the microbiota compositions of fish intestine, spleen, and liver. Significant differences in the microbiota composition were found between the internal organs of the diseased and the healthy fish in both experimental setups. Fusobacteriota was the most dominant phylum in the microbiota of healthy fish (∼70%, liver). Cetobacterium was the most abundant genus and relatively more abundant in healthy, compared to diseased fish. When A. hydrophila was inoculated by injection, it was the only pathogenic genus in the spleen and liver of the diseased fish. However, in the handling experiment, Vibrio was also detected in the diseased fish, demonstrating coinfection interactions. Based on these experiments, we conclude that indeed, A. hydrophila infection in tilapia causes changes in the microbiota composition of fish internal organs, and that fish net handling may trigger bacterial infection in freshwater aquaculture.

Centenarian lifespans of three freshwater fish species in Arizona reveal the exceptional longevity of the buffalofishes (Ictiobus)

During the 1910s three buffalofish species (Catostomidae: Ictiobus cyprinellus, I. bubalus, I. niger) were reared in ponds along the Mississippi River. Individuals of these buffalofishes were transported to locations across the United States to support or establish commercial fisheries, including Roosevelt Lake, Arizona in 1918. During the 1930s–1960s a commercial fishery existed on Roosevelt Lake, ending by 1970. Scarce information exists on Arizona buffalofishes since. From 2018 to 2023 we studied buffalofishes from nearby Apache Lake (adjacent and downstream of Roosevelt Lake) in collaboration with anglers. Here we show that > 90% of buffalofishes captured from Apache Lake are more than 80 years old and that some of the original buffalofishes from the Arizona stocking in 1918 are likely still alive. Using unique markings on old-age buffalofishes, we demonstrate how individuals are identified and inform dozens of recaptures. We now know all species of USA Ictiobus can live more than 100 years, making it the only genus of animal besides marine rockfishes (Sebastes) for which three or more species have been shown to live > 100 years. Our citizen-science collaboration has revealed remarkable longevity for freshwater fishes and has fundamentally redefined our understanding of the genus Ictiobus itself.

The Hematological Assessment of Toxic Effects Induced by Bisphenol A (BPA) in Oreochromis mossambicus Fish Species

Bisphenol A (BPA) is a widely used industrial chemical that has been detected in various aquatic environments. BPA is known to have endocrine-disrupting effects on aquatic organisms, but its impact on the hematological system is not well understood. In this study, we exposed Oreochromis mossambicus, a freshwater fish species, to different concentrations of BPA (1.0, 2.5, 5.0, and 7.5 mg/L) for 20 days and measured the changes in their hematological parameters. We found that BPA exposure caused a significant decrease in red blood cell (RBC) count, white blood cell (WBC) count, hemoglobin (Hb) concentration, and packed cell volume (PCV) in the fish compared to the control and solvent control groups. The decrease in these parameters was dose-dependent, meaning that higher concentrations of BPA resulted in lower values. We also found that BPA exposure affected the mean corpuscular hemoglobin concentration (MCHC), mean corpuscular hemoglobin (MCH), and mean corpuscular volume (MCV) of the fish, indicating that BPA altered the size and shape of the red blood cells. These results suggest that BPA has a negative impact on the blood system of the fish, affecting their oxygen transport, immunity, and hydration. The possible mechanisms of BPA-induced hematological alterations may involve oxidative stress, endocrine disruption, and immune suppression. Therefore, BPA poses a serious threat to the health and well-being of Oreochromis mossambicus and other aquatic organisms. The present study has concluded that the BPA exposure can cause anemia, oxidative stress, and immune dysfunction in Oreochromis mossambicus fish, depending on the dose and duration of exposure.

Population pharmacokinetics of enrofloxacin and florfenicol in the giant danio (Devario aequipinnatus) following oral administration of both antibiotics and bath administration of enrofloxacin

The lack of pharmacokinetic and drug exposure data, even for commonly utilized antibiotics, in freshwater ornamental teleost fish species magnifies the difficulties in treating bacterial pathogens. This study aimed to determine the population pharmacokinetics of enrofloxacin and florfenicol and to predict their probability of target attainment for giant danio (Devario aequipinnatus), a close relative of the commercially and biomedically important zebra danio (Danio rerio). Enrofloxacin was dosed orally at 8 mg/kg or via bath at 10 mg/L in 95 fish, and florfenicol orally at 60 mg/kg in 56 fish. Informative sampling times were identified by optimal design analysis. Drug concentrations in blood and muscle homogenate were quantified by LC-MS/MS and modelled by population pharmacokinetics. Monte Carlo simulations were used to predict the probability of pharmacokinetic/pharmacodynamic (PK/PD) target attainment. The apparent total clearance was 1.17 mL/h (33.9% coefficient of variation [CV] for between animal variability) for enrofloxacin and 1.89 mL/h (20.9% CV) for florfenicol. The ratio of drug exposure in muscle homogenate compared to that in plasma was 1.61 (33.3% CV) for enrofloxacin and 0.782 (19.4% CV) for florfenicol. Oral florfenicol at 60 mg/kg robustly covered MICs up to 2 to 4 mg/L, depending on the PK/PD target. While oral enrofloxacin (8 mg/kg) robustly covered MICs up to 0.125 to 0.5 mg/L, bath dosing at 10 mg/L for 5 or 10 h only covered MICs up to 0.0156 to 0.125 mg/L. These Monte Carlo simulations provided guidance on the range of MICs that result in high probabilities of successful treatment.

The Effect of Red Ginger Oleoresin Addition on the Oxidation Level in Oil Pangaas Catfish Offal (Pangasius hypoptalmus)

Pangas Catfish (Pangasius Hypophthalmus) is a freshwater fish species in Indonesia. The by-products of catfish processing offer potential for fish oil production due to their diverse fatty acid composition. However, fish oil is prone to oxidation, leading to deterioration of its quality. To address this issue, red ginger oleoresin (Zingiber Officinale Var. Rubrum), known for its antioxidant properties, is investigated as a possible solution to inhibit oxidation in the oil of Pangas Catfish offal. The objective of this study is to evaluate the impact of adding red ginger oleoresin at various concentrations to the oil of pangas catfish offal on its oxidation level. The research employed a Completely Randomized Design (CRD). Red ginger oleoresin was added to the oil of pangas catfish offal at concentrations of 0,2%, 0,4%, and 0,6%. The results indicated that the addition of 0,4% red ginger oleoresin was the most favorable treatment, as determined by sensory evaluations, which ranged from 7,57 to 7,85. The peroxide value (PV) of the oil was measured at 4,38 meq/kg, and the free fatty acid (FFA) was 1,25%. Furthermore, the oil of pangas catfish offal treated with 0,4% red ginger oleoresin exhibited significant levels of omega-3, omega-6, and omega-9 fatty acids at 1,02%, 16,26%, and 35,04%, respectively. The Saturated fatty acids (SFA), monounsaturated fatty acids (MUFA) and polyunsaturated fatty acids (PUFA) content were recorded at 43,22%, 37,04%, and 19,61%, respectively.

The paradise fish, an advanced animal model for behavioral genetics and evolutionary developmental biology.

Paradise fish (Macropodus opercularis) is an air-breathing freshwater fish species with a signature labyrinth organ capable of extracting oxygen from the air that helps these fish to survive in hypoxic environments. The appearance of this evolutionary innovation in anabantoids resulted in a rewired circulatory system, but also in the emergence of species-specific behaviors, such as territorial display, courtship and parental care in the case of the paradise fish. Early zoologists were intrigued by the structure and function of the labyrinth apparatus and a series of detailed descriptive histological studies at the beginning of the 20th century revealed the ontogenesis and function of this specialized system. A few decades later, these fish became the subject of numerous ethological studies, and detailed ethograms of their behavior were constructed. These latter studies also demonstrated a strong genetic component underlying their behavior, but due to lack of adequate molecular tools, the fine genetic dissection of the behavior was not possible at the time. The technological breakthroughs that transformed developmental biology and behavioral genetics in the past decades, however, give us now a unique opportunity to revisit these old questions. Building on the classic descriptive studies, the new methodologies will allow us to follow the development of the labyrinth apparatus at a cellular resolution, reveal the genes involved in this process and also the genetic architecture behind the complex behaviors that we can observe in this species.

Infection of bream with Ligula plerocercoids (Ligula intestinalis) of the Chernovsky reservoir of the Orenburg region

In recent years, much attention has been paid in the Orenburg region to the issues of increasing fish stocks in natural and artificial reservoirs. Annually, the Ural River, reservoirs of the region are stocked with carp, sturgeon species of fish, as well as land reclamation activities. One of the reasons that worsen the quality of fish products from the reservoirs of the region is helminthiases. They reduce fatness and fat content, spoil the marketable appearance of caught fish, thereby causing significant economic damage [1]. Ligullosis is a common helminthic disease of many species of freshwater fish, especially often recorded in cyprinids. The disease in fish is caused by plerocercoids of Ligulidae from the genus Ligula (family Ligulidae). Parasitizing in the abdominal cavity, the helminth compresses the internal organs, disrupts their functions, which can lead to atrophy and infertility [2]. The natural causes of the spread of ligulosis include fish-eating birds - the final hosts of the Ligula. In the intestines of birds, helminths become sexually mature and live only a few days, standing out with litter and not causing much harm. It is quite difficult and not always possible to control the number of fish-eating birds in water bodies [3]. The aim of our research was to study the degree of infestation of bream with plerocercoids of the genus Ligula in the Chernovsky reservoir of the Orenburg region.

Species range shifts of notorious invasive fish species in China under global changes: Insights and implications for management

Due to global changes, e.g., climate change and trade globalization, China is facing an increasingly severe threat from invasive freshwater fish species, which have the potential to cause negative impacts across various aspects and pose significant challenges for their eradication once established. Therefore, prioritizing the understanding of invasive species’ potential ranges and their determinants is vital for developing more targeted management strategies. Moreover, it is equally essential to consider the transitory range dynamics of invasive species that reflect changes in habitat availability and accessibility. Here, we used species distribution models (the maximum entropy algorithm) to assess the potential distributions of six notorious invasive fish species (i.e., Coptodon zillii, Cyprinus carpio, Gambusia affinis, Hemiculter leucisculus, Oreochromis mossambicus, and Oreochromis niloticus) in current and future (i.e., the 2030s, 2050s, and 2070s) periods along with their determinants, under two Shared Socio-economic Pathways scenarios (SSP1-2.6 and SSP5-8.5; global climate model: MRI-ESM2-0). Our results showed that the habitat suitability for the six species substantially benefited from temperature conditions (i.e., annual mean temperature or maximum temperature of warmest month). Throughout the given time periods, dramatic range expansions would occur for C. zillii, G. affinis, O. mossambicus, and O. niloticus, ranging from 38.61% to 291.90%. In contrast, the range of C. carpio would change slightly and irregularly, while H. leucisculus would contract marginally, with losses ranging from 1.06% to 12.60%. By the 2070s, species richness of these species would be relatively high in South, Central, and East China and parts of Southwest China. Furthermore, transitory fluctuations in the species ranges for all six species were observed throughout the entire time period (the 2030s–2070s). Given the range shifts for each species during different time periods, as well as time costs and budgets, adaptation strategies should be developed and implemented in the areas where they are most needed in each time period.

Occurrence and Health Risk Assessment of Sulfonamide Antibiotics in Different Freshwater Fish in Northeast China.

This study aimed to investigate the levels of 12 sulfonamide antibiotics in freshwater fish species obtained from three cities in northeastern China (Harbin, Changchun, and Shenyang). The analysis was conducted using HPLC-MS/MS to accurately quantify the antibiotic concentrations in the fish samples. The results showed that the average levels of sulfonamide antibiotics in fish samples from Harbin, Changchun, and Shenyang were 1.83 ng/g ww, 0.98 ng/g ww, and 1.60 ng/g ww, respectively. Sulfamethoxazole displayed the highest levels and detection rates in all three cities, whereas sulphapyridine exhibited the lowest concentrations in all the fish samples. The levels of sulfonamide antibiotic residues in the different fish species varied widely among the cities, and the highest level of antibiotic residues was found in the muscle of carnivorous fish. The results from a health risk evaluation on the consumption of these fish indicated that the risk from long-term antibiotic exposure to local residents from the intake of the sampled fish was small and not sufficient to pose a significant health risk to consumers.

Studies on some aspects of the fish Endoparasites (Cestodes)

Parasitic diseases are the major cause of morbidity and mortality in man, domesticated animals and wild life. Cestodes are multicellular, bilaterally symmetrical and parasites of great importance to human health. Intestinal infections of cestodes are very common in country and areas with poor socio-economic status are endemic unhygienic living and food habits promote the spread of infection causing high morbidity and complications. Mixed intestinal infection due to cestodes and nematodes is quite common and therefore, there is a need to study the cestode parasites whose prevalence is high. Cestodes infect almost all vertebrates. The freshwater fish species found in Nagapur Reservoir, Parli-Vaijnath, Dist. Beed (M.S.) were observed for the infection of cestode parasites. It was found that the freshwater fishes like Mystus seenghala and Mastacembelus armatus were infected by the cestode parasites. After detail study they were identified as Gangesia senghali (Hiware, 1999), Circumoncobothrium yamaguti (Jadhav et al., 1990). The cestode parasites were found in the small intestine of the host fishes.

Assessment of human health hazard associated with heavy metal accumulation in popular freshwater, coastal and marine fishes from south-west region, Bangladesh

An analysis was conducted on both freshwater, coastal and marine fish species to evaluate the concentrations of heavy metals, with the aim of assessing their levels and examining the potential health risks for humans linked to the consumption of contaminated fish. This study estimate concentrations of Cr, Fe, Cu, As, Cd and Pb in 60 individuals belonging to 20 species (10 species for freshwater and another 10 for coastal and marine fishes) by using Atomic Absorption Spectrophotometer. Metal concentrations of Cr, Fe, and Pb in freshwater fishes and Cr, Fe, As, and Pb in marine fishes were exceeded the maximum allowable concentration (MAC). The Estimated Daily Intake (EDI), Average Pollution Load Index (APLI), Target Hazard Quotient (THQ), Hazard Index (HI) and Target Cancer Risk (TCR) of heavy metals were determined for the assessment of human health risk. Ranking order of the values of EDI for freshwater fishes, coastal and marine fishes were Cd > Fe > Pb > Cr > Cu > As and Cd > Fe > Pb > Cr > As > Cu. Highest APLI value of 8.14 (Puntius ticto) that is seriously polluted and 3.003 observed in Otolichthoides pama in freshwater and marine fishes, respectively. THQPb and THQAs for all the fish species were exceed the safe limit (THQ>1) suggesting potential health risk to consumers. The hazard index for both the fish samples were exceeded the USEPA (United States Environmental Protection Agency) permitted risk level (HI > 1). The target carcinogenic risk value for Cr and As were crossed the USEPA standard limit (TCR> 1E-04), which denotes that continuous consumption of studied fishes may cause health risk to the consumers. On the other hand, sensitivity analysis of freshwater, coastal and marine fishes indicates that all the metal concentrations were responsible factor for health risk.

Comparative phylogeography informs community structure and assembly during and after Pleistocene Lake Bonneville

Abstract Dispersal is one of the major processes controlling both genetic diversity and species diversity and is frequently studied in both phylogeography and community ecology. As such, integrating these fields to uncover how both historical and contemporary dispersal have affected local community structure can provide greater insights into community assembly. We used comparative phylogeography to determine if freshwater fish species in the Bonneville Basin show evidence of geologically recent dispersal and gene flow, which would probably have occurred when the basin was inundated by Lake Bonneville in the late Pleistocene. We then used museum records to uncover patterns of contemporary community structure and relate them to the results of the phylogeographical analyses. We found evidence for late Pleistocene dispersal throughout the Bonneville Basin in most of the fish species studied, which would have homogenized ancient communities. However, modern communities show evidence of non-random community structure and dispersal limitation between major sub-basins and habitats. Together, these results suggest that the Bonneville Basin fish fauna assembled due to a combination of historical dispersal and contemporary habitat filtering and extinction dynamics following isolation. Further work should continue to combine different data types to achieve more accurate inferences regarding contemporary community assembly.

New Australian frontier in freshwater fish invasion via Torres Strait Islands

AbstractAll continents, excluding Antarctica and the Artic, have been affected by incursion from alien freshwater fish species. Australia has not been spared. Four hundred and fifty species have now been declared on the ornamental importation list, making management a real challenge. With approximately 25 non-native species documented, Papua New Guinea (PNG) has likely some problems with invasive freshwater fish. Many of these species have been intentionally introduced to increase access to food as a protein source for remote communities or have spread naturally from western parts of Java and Indonesia, and now constitute a large biomass on some floodplain areas in PNG. The Torres Strait is located between PNG and northern Queensland and was previously a land bridge, though now under higher sea levels the region exists as a series of approximately 300 islands. The threat of further range extension of freshwater fish from PNG into northern Queensland via the Torres Strait Islands is significant, with two invasive fish species already recorded on northern islands of the Torres Strait (climbing perch, Anabas testudineus which has been continually recorded for the past decade; and recently the GIFT tilapia, Oreochromis niloticus). Here we present a case to control further spread of invasive freshwater fish species towards Australia, using a Land and Sea Ranger program, where Rangers are trained to be confident in the identification of pest fish species and to implement strategies to protect their borders from potential future incursions. The success of this program relies on Rangers to continue partaking in surveillance monitoring of coastal waters, checking and controlling for any new invasive species moving from PNG into Australian waters. We outline the biosecurity obligation under Article 14 of the Treaty between the two nations, which identifies the importance of conservation and protection of coastal floodplains from invasive species, and the spread between both nations.

Tea polyphenols protect against Flavobacterium columnare-induced gill injury via suppression of oxidative stress, inflammation, and apoptosis in grass carp

Flavobacterium columnare (F. columnare) is one of the deadliest fish pathogens causing bacterial gill rot disease in various freshwater fish species globally. Tea polyphenols (TPs) are an inexpensive product extracted from tea that have received much attention as a feed additive in aquaculture. The current study was designed to investigate the underlying mechanisms and protective effects of dietary TPs against F. columnare-induced gill injury via suppression of oxidative stress, apoptosis, and inflammation in grass carp. TPs were not supplemented to the diet (control) and were supplemented at 40, 80, 120, 160 or 200 mg/kg diet. The feeding experiment was carried out for 60 days, followed by a 3-Day F. columnare challenge test. The results showed that 120 mg/kg TPs in the diet exerted the following five protective effects in fish gill: (1) control gill-rot disease and improved histopathology, (2) inhibit excessive apoptosis, (3) enhance the activity of antioxidant enzymes and upregulate related gene expression via the Nrf2/Keap1 pathway, (4) increase the activity of immune enzymes, And (5) mediate inflammatory cytokine gene expression via the JAK/STAT3 pathway. Taken together, dietary supplementation with TPs is a compelling approach to protect the gill function of fish against F. columnare.

Nutritional composition of available freshwater fish species from homestead ponds of Patuakhali, Bangladesh

The purpose of this study was to analyze the proximate composition and mineral contents of available freshwater fish species from homestead ponds of Patuakhali. Eleven (11) different species of freshwater fish were collected. The moisture content of analyzed fish species ranged from 65.46 to 76.82 %. Significantly higher content of protein was found in Channa striatus and Anabas testudineus and lipid and ash was found in A. testudineus. However, protein and lipid content were significantly low in Esomus bengalensis and Notopterus notopterus, respectively. The lowest content of ash was experienced in Wallago attu and Heteropneustes fossilis. The higher concentration of calcium (Ca), sodium (Na), phosphorous (P) were obtained from Colisa fasciata. The magnesium (Mg), potassium (K), and sulpher (S) content were high in C. striatus, H. fossilis, and N. notopterus, respectively. The lowest content of Ca and Mg was obtained from A. testudineus. Lower content of Na and K was found in E. bengalensis. P and S content was low in C. punctatus. The PCA biplot analysis showed positive and negative relations between fish species for both proximate composition and mineral contents. Therefore, homestead ponds of the coastal area could be a habitat for multiple fish species and a good source of household nutrition.

Extinction risks and threats facing the freshwater fishes of Britain

Abstract Extinctions occur naturally in all environments, but rates have accelerated rapidly during the Anthropocene, especially in fresh water. Despite supporting many fish species of conservation importance, there has never been a formal assessment of their extinction risks in Britain, which has impeded their inclusion in relevant legislation and policy. This study therefore used the International Union for the Conservation of Nature (IUCN) Red List of Threatened Species™ Categories and Criteria to conduct the first systematic assessment of the extinction risks and threats facing the native freshwater and diadromous fishes of Britain. In addition, national assessments were produced for England, Scotland and Wales, reflecting the level at which environmental policy decisions are taken in Britain. Seven species were categorized as being threatened with extinction at the regional level, with European eel Anguilla anguilla and allis shad Alosa alosa classified as Critically Endangered, Atlantic salmon Salmo salar, vendace Coregonus albula and European whitefish Coregonus lavaretus classified as Endangered, and Arctic charr Salvelinus alpinus and twaite shad Alosa fallax classified as Vulnerable. In addition, burbot Lota lota was classified as Regionally Extinct, ferox trout Salmo ferox was categorized as Data Deficient, and 25 species were categorized as Least Concern. European sturgeon Acipenser sturio and houting Coregonus oxyrinchus, although probably native, qualified as only vagrants in fresh water, so were categorized as Not Applicable. The assessments provide objective baselines against which future changes can be determined, and a key evidence base to support policy and management decisions for the conservation of freshwater and diadromous fish species and their habitats in Britain. It is recommended that the assessments are repeated every 10 years, which would enable changes in conservation status, the effectiveness of policies and where targeted interventions may be required to be examined using the Red List Index.

Evaluation of Fatty Acid and the Composition of Six Different Species of Freshwater Fish in the North of Algeria


 
 
 Background: Few studies have been published about the quality of freshwater fish in Algeria. This study determined the chemical composition and the fatty acid of six species of freshwater fish cultivated in the North region of Algeria (Nile tilapia, red tilapia, common carp, Algerian barb, crucian carp, and mirror carp) as well as the nutritional quality of the lipids in these freshwater fish species.
 Methods: One hundred and ten freshwater fish were randomly caught in the spring of 2021 from Achor Ali farm (Jijel), Beni-Haroun Dam (Mila), and EL-Agrem Dam (Jijel) from Algeria. Moisture, ash, protein, lipid, and fatty acids were measured according to standard laboratory procedures and protocols of previous studies. Statistical analysis was performed using ANOVA (XLSTAT 2014), and the pair wise comparison of the means was done by Tukeys test at the 5% significance level (p<0.05).
 Results: Regarding freshwater fish species, fatty acid profiles were discovered to have 38.94 to 57.75% Saturated Fatty Acids (SFAs), 29.35 to 46.63% Monounsaturated Fatty Acids (MUFAs), and 6.79 to 26.55% Polyunsaturated Fatty Acids (PUFAs). Common carp was a rich resource of Eicosapentaenoic Acid and Docosahexaenoic Acid (EPA+DHA) (5.38%); the highest concentration of ω-3 was recorded in crusian carp (10.63%); and Nile tilapia contained significant levels of ω-6 PUFA. Results demonstrated that the examined freshwater fish species appeared to have a good nutritional value and be a source of important fatty acids with positive effects on consumer health. On the other hand, results revealed low levels of PUFAs.
 Conclusion: The examined freshwater fish species appeared to have a good nutritional value, but, it is important to provide diets rich in fatty acids, in particular PUFAs, to these freshwater fish to improve the nutritional quality of their lipids.