Experimental Fish Research Articles

Efficacy of 17β-estradiol on survival rate, sex reversal, and growth performance of climbing perch (Anabas testudineus) using the immersion method

This study aimed to evaluate the efficacy of estradiol on the survival rate, sex reversal ratio, and growth performance of climbing perch (Anabas testudineus) using the immersion method. A completely randomized design was applied, involving three estradiol (E2) treatment groups at concentrations of 1.0 mg/L (1E2), 1.5 mg/L (1.5E2), and 2 mg/L (2E2), along with a control group triplications. Seven-day-old fingerlings were exposed to the E2 solution for 2 h before being transferred to nurseries in hapas placed in earthen ponds at a density of 200 fish/m² for 60 days. After the hormone treatment and 60 days of rearing, the highest survival rate was observed in the control group (86.7%). The female ratios in the 17β- stradiol (E2) treatments ranged from 72.0% to 90.0%, which were significantly higher than the ratio of the control group (55.6%) (P < 0.05). The 2E2 treatment demonstrated the highest female percentage, which was statistically greater than that observed in the 1E2 and 1.5E2 treatments (P < 0.05). The mean weight and length of fish in the E2 treatments were greater than those in the control treatment, although the differences were not statistically significant (P > 0.05). Additionally, the study revealed a direct proportionality between the average weight of experimental fish and the hormone concentration. Based on these findings, the recommended dose for achieving maximum mono-sex female climbing perch is 2 mg/L of 17β-estradiol.

Analyses of Heavy Metals Bioaccumulation in the Organs of Clarias gariepinus Following Exposure to Sub-Lethal Concentrations of Waste Burnt Tire Residues

This study evaluated the bioaccumulation of certain heavy metals of waste burnt tire residues (WBTRs) in certain organs (viz-gills, liver, kidney and muscles) of Clarias gariepinus following exposure to sublethal concentrations (SLCs) of water-soluble fractions (WSFs) of WBTRs. Clarias gariepinus (average weight of 47.95±0.34g and length of 15.54±0.36cm) were exposed to SLCs at different concentrations (0.00, 0.23, 0.47, 0.94, 1.87, and3.74 ppm) of WSFs of WBTRs for a period of fifty-eight days. Heavy metal concentrations in WBTRs and in the organs of the experimental fish were measured using a handheld X-Ray Fluorescence Analyzer (NitonXL3T). Results showed that strontium, lead, zinc, cobalt, bismuth, rubidium, gold, tungsten, iron, thorium, arsenic, copper, and niobium were detected in WBTRs although the maximum level of zinc was perceived however, no significant difference (P>0.05) was observed as compared to the control group regarding heavy metal accumulation in muscles, 53.10±12.78; liver, 56.30±76.96; kidney, 164.54±12.78; and gills, 241.36±146.87 of the exposed fish. The high levels of heavy metals present in WBTRs are of great concern as potential detrimentl pollutants to the aquatic ecosystem. These allochthonous inputs get into the aquatic ecosystem through sewage flow and runoffs effluents. Resident non-target communities particularly fishes from such polluted aquatic systems with WBTRs become vunerable and incriminated with attendant high levels of heavy metals that could be detrimental to human consumers.

Improved growth and immunity in Nile tilapia Oreochromis niloticus fed a fermented rice bran supplement

Improvement of growth performance and disease resistance of cultured species is an important objective of the aquaculture industry. In this study, solid-state fermentation (SSF) was applied for increasing the nutritional value of rice bran with baker's yeast (Saccharomyces cerevisiae). Four diets containing different levels of fermented rice bran (FRB) at 0, 100, 200 and 300 g/kg (FRB0, FRB10, FRB20 and FRB30, respectively) were tested using juvenile Nile tilapia Oreochromis niloticus (average body weight = 5.22±0.02 g) for 56 days. Compared to FRB0, all diets improved growth performance of the experimental fish (P<0.05). Intestinal amylase and protease amounts were significantly increased (P<0.05). The experimental fish were intraperitoneally injected with Streptococcus agalactiae and the cumulative mortality rate was monitored for 10 days. All FRB-supplemented diets resulted in greater survival rates in challenge fish. The FRB20 and FRB30 diets promoted expression of insulin-like growth factor I (IGF-I) transcripts and enhanced non-specific immunity; lysozyme and antioxidant enzyme activities; myeloperoxidase (MPO), catalase (CAT), and superoxide dismutase (SOD) (P<0.05). The expression level of interleukin 8 (IL-8) was down-regulated in fish fed FRB20 and FRB30 (P<0.05) but IL-10 was up-regulated in fish fed FRB10 and FRB30 (P<0.05) while IL-1β was up-regulated in fish fed FRB20 (P<0.05). The expression of complementary 3 (C3) transcripts was significantly increased while nuclear factor-kappa B (NF-κB) was decreased in fish fed all FRB-supplemented diets (P<0.05). Conventional histology revealed increased villus height following FRB30 treatment (P<0.05). These results suggest the beneficial use of FRB supplementation on growth, immune defense and stress tolerance for juvenile O. niloticus.

Autocrine/paracrine fibroblast growth factor 1 (FGF1) enhances systemic lipid metabolism in rainbow trout fed with a high-fat diet by elevating uridine levels through the AMPK signaling pathway and activating the upp2 promoter via irf1

Fibroblast growth factor 1 (FGF1) is recognized for its role in regulating vertebrate energy metabolism, yet its impact on metabolic fatty liver disease in fish remains unexamined. This study investigates the regulatory mechanism of the autocrine/paracrine cytokine FGF1 on systemic lipid metabolism in rainbow trout (Oncorhynchus mykiss) subjected to a high-fat diet (HFD). Experimental fish (540 in total) were divided between two dietary groups (low-fat diet (LFD) and HFD) and categorized into three treatment groups: LFD + PBS (LFD injected with PBS), HFD + PBS (HFD injected with PBS), and HFD + rFGF1 (HFD injected with recombinant FGF1 protein). Over a 6-week period on the HFD, rainbow trout demonstrated weight gain and signs of metabolic dysregulation. However, compared to the HFD + PBS group, exogenous rFGF1 administration significantly lowered hepatosomatic index (HSI), whole-body, muscle, and liver crude fat content, hepatic vacuole formation, serum triglyceride (TG), serum LDL-c, and the expression levels of fatty acid synthesis (fas) and transport genes (cd36, fatp6), while elevating HDL-c and the expression levels of fatty acid oxidation genes (cpt1a, pparα, and acox1) (P < 0.05), thereby alleviating HFD-induced lipid accumulation without a significant impact on body weight (P > 0.05). Serum metabolomic analysis indicated that rFGF1 significantly elevated serum uridine levels (P < 0.05), with uridine demonstrating a capacity to regulate hepatocyte lipid metabolism effectively. Furthermore, rFGF1 was shown to enhance hepatic uridine biosynthesis through the AMPK signaling pathway, concurrently modulating uridine catabolism by downregulating interferon regulatory factor 1 (irf1) and altering its transcriptional control of uridine phosphorylase 2 (upp2). These findings suggest that rFGF1 mitigates hepatic lipid accumulation in rainbow trout under an HFD by promoting uridine synthesis via the AMPK pathway and partially inhibiting uridine catabolism through IRF1-UPP2 signaling.

Longline hook selectivity for whiting (Merlangius merlangus euxinus) with a perspective on small-scale fisheries management in the Black Sea, Türkiye

This study investigated the selectivity parameters of bottom longlines for the Whiting (Merlangius merlangus euxinus) in the small-scale fisheries of the Southeastern Black Sea. Experimental fishing operations were conducted using longlines with hook of 11, 12, 13, and 14mm gaps. A total of 552 fish specimens from four species were captured, with Whiting, the target species, accounting for 90.94% (502 specimens) of the total catch by numbers. The sizes of the Whiting ranged from 10.6 to 20.0 cm Total Length (TL), with a mean size of 15.79 ± 0.087 cm TL. The longline selectivity parameters and curves were fitted using the SELECT method, with the bi-modal model offering the best-fit, based on the lowest deviance value. The modal sizes of specimens caught using the hook of 11, 12, 13, and 14-mm gaps were 12.40, 13.53, 14.66, and 15.78 cm TL, respectively. The modal sizes and spread values increased proportionally with hook size. All the individuals caught by the 14-mm gap hooks exceeded the minimum landing size (MLS) of 13 cm. However, the proportions of individuals below the MLS for the 11, 12, and 13-mm gap hooks were 32.09%, 6.98%, and 0.68%, respectively. Based on the MLS, hooks with gaps larger than 11 mm were found to be highly selective and are recommended for sustainability of the fisheries while ensuring the conservation of immature individuals in the Whiting stocks of the Black Sea. These findings contribute to the much-needed data and information for the design of sound management plans for the small-scale fisheries in the region.

Immune protective, stress indicators, antioxidant, histopathological status, and heat shock protein gene expression impacts of dietary Bacillus spp. against heat shock in Nile tilapia, Oreochromis niloticus

This research evaluated the efficacy of mixed Bacillus strains probiotic supplements in mitigating acute thermal-induced stress in Nile tilapia (Oreochromis niloticus). Three experimental fish groups involved 135 Nile tilapia (49 ± 2 g); one control (no added probiotics), 0.5, and 1% of selected Bacillus strains (B. subtilis, B. licheniformis, and B. pumilus) for 58 days. After the feeding period, growth parameters, immunological parameters, stress biochemical markers, and antioxidant parameters in addition to genes related to stress and histopathological changes in fish, were assessed; subsequently subjected to heat shock at 36 ± 0.5 ◦C for 2 h. Before the heat challenge, our results exhibited a marked increase in the growth efficacy (P < 0.05), lower marked serum levels of triglycerides and cholesterol, and tissue malondialdehyde (MDA) levels along with significantly increased superoxide dismutase (SOD) and catalase (CAT) enzymes activity in fish-fed Bacillus probiotic at 0.5% concerning the control group (P < 0.05). There were no significant changes in the serum levels of glucose, cortisol, lactate, phagocytic activity, respiratory burst (ROS), total immunoglobulin Ig, alanine aminotransferase (ALT), aspartate aminotransferase (AST), lactate dehydrogenase (LDH), total protein, albumin, globulin, uric acid, urea, creatinine, as well as HSP70, GST, and GPx mRNA expression in most of the probiotic groups compared to the control group (P > 0.05). When Nile tilapia was exposed to heat stress, supplementation with Bacillus probiotic in the diet significantly decreased most of the indices related to serum biochemical (ALT (P < 0.01; P < 0.001), AST (P < 0.01), LDH (P < 0.01), urea (P < 0.05), and creatinine (P < 0.01)), triglycerides (P < 0.001; (P < 0.01)), cholesterol (P < 0.01; (P < 0.05)), glucose (P < 0.001), and cortisol (P < 0.01; (P < 0.05)), with tissue oxidative stress MDA levels (P < 0.05), and HSP70 mRNA expression (P < 0.01; P < 0.001), aligned with the stressed control group. In addition, a notable upsurge in the total protein, albumin, globulin, phagocytic and ROS activities, and total Ig, as well as the enzymatic antioxidant ability (SOD, CAT) (P < 0.01), with GST and GPx mRNA expression (P < 0.05; P < 0.01), were shown in fish-fed Bacillus spp. post-exposure compared with the stressed control group. Besides, no histopathological alterations were revealed in the spleen and brain of fish pre- and post-heat exposure. According to our findings, diet supplementation of Bacillus species has the potential to combat the suppressive effects of heat shock in Nile tilapia.

Comparison of catch efficiency of wire mesh fish traps operated along the coast of Thoothukudi, South-east coast of India

Aim: The study designs and fabricates traps with diverse wire mesh colors and shapes for field experiments. It also collects detailed catch data to assess their catch efficiency and determine the most effective design. Methodology: Experimental fish traps were fabricated utilizing four distinct colors (Light green, Dark green, White and Orange) and three different shapes (rectangle, square and circle). Fishing trials were conducted in selected fishing villages of Thereshpuram, with the traps operated fortnightly from June 2022 to May 2023. The catch rate per trip (CPUE) was calculated using the Total catch (in numbers) divided by the Unit Effort (White, 1987). An economic analysis of trap fishery was also performed based on gross revenue and total cost (Geetha et al., 2014). Results: The traps' overall catch per unit effort (CPUE) was recorded at 0.48Nos hr-1. Siganus canaliculatus emerged as the dominant species among the fishes trapped, constituting 16% of the total catch. Regarding trap color, the highest CPUE was observed with traps of dark green color (0.63 Nos hr-1), followed by light green (0.51 Nos hr-1), white (0.49 Nos hr-1) and orange (0.38 Nos hr-1). Economically, the performance of the trap fishery was evaluated using indicators such as operating cost/year, fixed cost, gross revenue and profit cost ratio. The success of the trap fishery was further emphasized by a benefit-cost ratio (BCR) of 3.50. Interpretation: Dark green-colored, square-shaped traps show promise in significantly enhancing fishermen's profits due to their higher catch per unit effort (CPUE) compared to other colors. Moreover, dark green traps may offer ecological advantages by blending into natural surroundings. This study highlights their potential and provides practical insights for fishermen to make informed gear choices, considering factors like color and shape. Key words: BCR, Color, CPUE, Shape, Trap

The Effect of Phytase Enzyme in Feed on Growth Performance, Feed Utilization Efficiency, and Survival Rate of Milkfish (Chanos chanos) Fingerlings

The aim of this study was to evaluate the effect of phytase enzyme supplementation on the growth performance, feed utilization efficiency, and survival rate of milkfish fingerlings. The experimental fish used in this study were milkfish fingerlings with an average weight of 2.89±0.46 g per fish. The feed used in this research was a formulated pellet feed containing 30% protein, with added phytase enzyme. The treatments consisted of different phytase enzyme doses, namely A (0 mg/kg feed), B (250 mg/kg feed), C (500 mg/kg feed), and D (750 mg/kg feed). The results showed that different doses of phytase enzyme in the feed significantly affected (P&lt;0.05) growth performance and feed utilization efficiency but did not significantly affect (P&gt;0.05) the survival rate of milkfish fingerlings. The optimal dose of phytase enzyme for improving growth performance and feed utilization efficiency in milkfish fingerlings was between 502-665 mg/kg feed, resulting in a maximum total feed consumption (TFC) of 140.43 g, Feed Conversion Ratio (FCR) of 1.18, feed efficiency (FE) of 78.16%, protein efficiency ratio (PER) of 2.6, and relative growth rate (RGR) of 4.43%.

Effect of water pollution by nickel on hepatic enzymes and oxidative enzymes in Cyprinus carpio (common carp)

Nickel (Ni) is considered a toxic heavy metal that causes serious diseases in humans and animals. Therefore, this study was conducted on common carp, which is considered an essential food item for humans. This study was designed to investigate the effect of nickel on the hepatic and antioxidant enzymes of Cyprinus carpio after 3 and 6 weeks of exposure to water contaminated with Ni. C. carpio fingerlings were purchased from a neighboring fish hatchery. The morphometric characteristics of the experimental fish were documented. All fish were stocked, regardless of gender. The fish were exposed to different concentrations (20, 40, 60, 80, and 100 mg/L) to obtain the LC50 for Ni during 96 hours, and the median lethal concentration of Ni was 80 mg/L through 96 hours. The fish were exposed to two safe concentrations, 1 ppm and 5 ppm. The results after 3 and 6 weeks were as follows: When compared to the control groups, all treated groups had significantly higher levels of liver function parameters (ALT and AST). Malondialdehyde (MDA) and catalase activity measurement (CAT) enzyme levels were considerably higher in all treated groups after 3 and 6 weeks as compared to control groups. These changes are trustworthy indications of the cellular and humoral immune responses in C. carpio.

Preparation of Platinum Nanoparticles of Biophytum reinwardtii and Evaluation of Neuroprotective Activity of MPTP-induced Parkinson’s Disease in Zebra Fish

Aim: To evaluate the Neuroprotective activity of Biophytum reinwardtii Platinum nanoparticles Methods: Biophytum reinwerdtii platinum nanoparticles were subjected to evaluation of the neuroprotection activity in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine induced zebra fishes. Experimental fishes are divided into 5 groups, each containing 8 fishes. Group I is considered a normal group; Group II is a toxic group means treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine 225 mg/kg, i.p. for 5 days; Group III, IV, and V are treatment groups means treated with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (225 mg/kg) with 0.3 µmol, 0.4µmol, and 0.5 µmol of Biophytum reinwardtii Platinum nanoparticles respectively for 5 days. Results: In the in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine group, locomotor activity and complex I activity are decreased, Malondialdehyde levels increased, antioxidants, and catecholamines levels decreased, whereas Biophytum reinwardtii Platinum nanoparticles treated fishes exhibit significant locomotor and increased levels of antioxidants and catecholamines. Conclusion: These results suggest that Biophytum reinwardtii Platinum nanoparticles. Showed significant neuroprotection activity in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine -induced Parkinson’s zebra fishes.

The use of protein hydrolysate from fish waste as part of microbiological culture media

The need to involve in the processing of significant amount of secondary protein-containing raw materials formed during fish cutting, on the one hand, and on the other hand, the shortage of a source of the protein component of microbiological nutrient media determines the relevance of the work. The goal was to study the possibility of using fish protein hydrolyzate obtained by enzymatic hydrolysis from secondary fish raw materials in microbiological nutrient media. Microbiological and physicochemical methods were used to conduct research. When optimizing the developed algorithm for the fermentation process, a mathematical model of the experiment was used with a minimum number of experiments. An algorithm has been developed for obtaining fish protein hydrolyzate from meat and bone waste from cutting pelagic fish (cod). The hydrolysis parameters were optimized: the concentration of the enzyme preparation is 1.33 % of the total mass of waste, the duration of the fermentation process – 3 hours. The characteristics of the resulting fish hydrolyzate are determined: the mass fraction of total nitrogen – 13 %, amine – 3.6 %, water – 4.6 %, sodium chloride – 2.7 %, fat – 0.3 %. An experimental fish hydrolyzate has been studied as a source of protein nitrogen in accordance with the formulation of a microbiological medium used for counting when growing colonies of microorganisms. The effectiveness of the prepared nutrient media was assessed by comparing the performance coefficients of the experimental and control nutrient media, as well as by identifying test microorganisms grown on the experimental medium. It was established that the growth pattern of test cultures both on the studied nutrient medium and on the control medium was almost the same. Test microorganisms retained their biochemical, morphological and cultural characteristics. The research results showed the possibility of using fish protein hydrolyzate obtained by enzymatic hydrolysis from secondary fish raw materials in microbiological nutrient media.

Ameliorating effects of natural herbal supplements against water-borne induced toxicity of heavy metals on Nile tilapia, (Oreochromis niloticus)

The efficacy of herbal supplements in mitigating heavy metals (HMs) toxicity was investigated using a widely grown fish, the Nile tilapia (Oreochromis niloticus). The experiment was conducted over two phases: during the stress phase, the experimental fishes were exposed to sub-lethal concentrations of HMs, including lead, cadmium, zinc, and copper for 15 days; following which during the feeding phase, herbal supplements were given for 70 days to ameliorate their effects. Seven groups were established: the control negative group (CON−ve), control positive group (CON+ve, without any treatment), and five groups with supplementation of 1% turmeric (TUR), cinnamon (CIN), ginger (GIN), garlic (GAR), and their mixture (MIX), respectively. A total of 315 fishes were distributed evenly in experimental tanks (15 fishes per tank, in triplicates). The results revealed that exposure to HMs led to significant (p < 0.05) alterations in all the tested parameters, i.e., liver damage and growth reduction. The herbal supplements, especially the MIX groups, ameliorated the harmful effects of HMs and restored fish growth, digestibility, carcass composition, and liver health. In conclusion, the study demonstrated that the herbal supplements were effective in reducing the HMs-linked toxicity in Nile tilapia. Future studies pertaining to the mechanisms facilitated by the various herbal bioactive substances-linked tolerance to HMs in fishes are warranted.

A Study on the Catch Losses and Mesh Selectivity Related to the Attachment of Marine Mammal Bycatch Reduction Devices on Midwater Trawl Gear

The National Institute of Fisheries Science in Korea is developing marine mammal bycatch reduction devices (BRDs) for high-risk fishing gear, such as trawls. We experimented with two BRD types (guiding nets) attached in front of codend at 30° and 45° angles, and catch losses and mesh size selectivity were investigated. Experimental fishing operations were conducted along the East Coast of South Korea where whales and dolphins are commonly sighted. The catch was classified according to fishing location, BRD type, codend, and covernet, with measurements recorded for body length, maximum girth, and weight. The average selectivity for each haul was analyzed using the ‘selfisher’ package. The catch loss rates with the BRD attached at tilt angles of 30° and 45° were 11% and 29% for common flying squid, 6% and 28% for sailfin sandfish, and 5% and 8% for pearlside. While the mesh selectivity rates for common flying squid and pearlside remained at 0.2–0.5 across all lengths and tilt angles, the mesh selectivity curve for sailfin sandfish was estimated. There were significant differences in catch loss between 30° and 45° angles, with the 30° angle being more effective in catch loss. We observed a masking effect in the codend.

Spectral-based detection of chromatin loops in multiplexed super-resolution FISH data

Involved in mitotic condensation, interaction of transcriptional regulatory elements and isolation of structural domains, loop formation has become a paradigm in the deciphering of chromatin architecture and its functional role. Despite the emergence of increasingly powerful genome visualization techniques, the high variability in cell populations and the randomness of conformations still make loop detection a challenge. We introduce an approach for determining the presence and frequency of loops in a collection of experimental conformations obtained by multiplexed super-resolution imaging. Based on a spectral approach, in conjunction with neural networks, this method offers a powerful tool to detect loops in large experimental data sets, both at the population and single-cell levels. The method’s performance is confirmed on experimental FISH data where Hi-C and other loop detection results are available. The method is then applied to recently published experimental data, where it provides a detailed and statistically quantified description of the global architecture of the chromosomal region under study.

Oral administration of recombinant Lactococcus lactis expressing largemouth bass (Micropterus salmoides) IFNa3 protein enhances immune response against largemouth bass virus (LMBV) infection

Largemouth bass virus (LMBV) is a highly pathogenic pathogen that often causes high mortality of affected largemouth bass and significant financial losses. Type I interferon as an effective and broad spectrum tool has been successfully used for therapeutic or prophylactic treatment some viral infections. However, the implementation of immunotherapies based on interferon administration to combat LMBV infections has not been reported. And Lactic Acid Bacteria (LAB) are a powerful vehicle for expressing cytokines or immunostimulant peptides at the gastrointestinal level after oral administration. In this study, Lactococcus lactis (L. lactis) expression system with lactose as a screening marker was utilized to express the Micropterus salmoides interferon a3 (IFNa3) protein and orally administered to largemouth bass. The genetically engineered strain pNZ8149-Usp45-IFNa3-6His/L. lactis NZ3900 was successfully constructed, and its potential to elicit immune protection response by oral administration was evaluated. After orally administration, the recombinant L. lactis was detected in guts of experimental fish and remained detectable for 72 h. Additionally, IFNa3 was able to enhance the test fish's immune response, as determined by the relatively increased mRNA relative expression of immune-related genes in the liver, spleen, and kidney tissues, including IFN-γ, TNF-α, IL-1β, IL-8, IgM and IgT. Following LMBV challenge, the experiment group of pNZ8149-Usp45-IFNa3-6His/L. lactis NZ3900 exhibited a 70 % survival rate, while survival rate were 15 % in the PBS control group, 45 % in the pNZ8149/L. lactis NZ3900 group. Furthermore, the viral load in the surviving fish was significantly lower than that of the control groups. These findings suggest that oral administration of recombinant L. lactis producing IFNa3 induces largemouth bass immune responses at a systemic level to effective prevent and combat of LMBV infection.

Spatio-temporal Dynamics of Anuran Populations in the Wetlands of Korhogo, Côte d'Ivoire

Aims: The Korhogo commune contains several natural habitats that are home to a large community of frogs. But today, these habitats are facing strong anthropic pressures. This study aims to show the effect of anthropogenic activities on wetlands and the organisms that live there. Methodology: Sampling took place from June 2023 to May 2024, and samples came from experimental fishing using deep-net dip nets with 2 mm mesh or rod and line, and from commercial fishing using various gears. Results: A total of 791 individuals were caught, for a total biomass of 48.872 Kg. These individuals were divided into 5 species, 4 genera and 4 families. Spatially, diversity was highest in the lakes (80) and lowest in the rice fields (20%). Temporally, diversity was highest in the rainy season (100%) and lowest in the dry season (40%). The species Hoplobatrachus occipitalis dominated the population with 94.66% of captures. It accounted for 25.46%, 24.27%, 22.81%, 13.93% and 13.53% respectively in lakes, rice fields, rivers, wells and shallows. The strong presence of this species in the wetlands of this commune shows that these areas are highly threatened. Conclusion: This study contributes to the knowledge of the frog population and helps to combat the degradation of wetlands in the city of Korhogo.

The New Fishing Technique With Lighted Gillnets in Lake Kivu: Panacea or Pandora's Box?

ABSTRACTA new fishing technique has been introduced in Lake Kivu, across the Congo side. It consists of gillnets on which light‐emitting diode (LED) lamps are attached. Traditional fishermen have introduced the fishing technique without any studies related to the positive and drawback effects of this fishing technique. We sought to understand whether the gillnets with LED lamps fishing technique improve fishing catches and can be regarded as sustainable for the Lake Kivu ecosystem, or is it just only a marketing strategy for gillnets and LED lamp sellers. Two complementary approaches have been used in this study. Experimental fishing campaigns were conducted from June 2021 to June 2022 and monitoring of fishing team in the field coupled with surveys of fishermen about the effectiveness use of this new fishing technique. We observed that (i) 88% of fishermen using gillnet in the Bukavu sub‐basin have already adopted the recently introduced fishing technique; (ii) the average catch per unit effort of gillnets with LED lamps is higher than those without LED lamps (3.84 ± 1.95 kg/net vs. 2.69 ± 2.04 kg/net); (iii) these gillnets retrieve larger specimens (79.88 mm vs. 76.69 mm) and generate monthly a higher average profit to fishermen ($916.35) than the fishing technique lacking the LED ($807). However, (iv) the gillnets with LED lamps generates a lot of plastic trash: around 2130 kg of plastic bags/month under fishing conditions in the Bukavu sub‐basin. So, this new fishing technique is a real panacea for its practitioners, but a veritable Pandora's box generating plastic pollutants in Lake Kivu. Instead of banning this new fishing technique, we need to adapt it by using submersible LED lamps.

Integrating Direct Experimental Fishing and Environmental DNA Metabarcoding to Assess Fish Biodiversity in the Cibareno River, Indonesia, to Support Fishway Design

Integrating Direct Experimental Fishing and Environmental DNA Metabarcoding to Assess Fish Biodiversity in the Cibareno River, Indonesia, to Support Fishway Design

Organ-specific bioaccumulation of microplastics in market fish of Dhaka and size-dependent impacts of PVC microplastics on growth of Anabustestudineus

Microplastics (MPs), a growing environmental concern with potential ecotoxicological risks, are ubiquitous in aquatic environment. This study investigated the organ-specific distribution and variation of MPs in commercially caught fishes (7 species, 140 individuals) collected from Dhaka's two main fish distribution hubs (Uttara and Jatrabari). Additionally, the impact of different-sized MPs on fish growth (Anabas testudineus) was examined in a control experiment. Results revealed that kidneys of market fish bioaccumulated the highest concentration of MPs (average, 59.1 MPs/g), followed by liver (24.6 MPs/g) and intestine (18.6 MPs/g). On average, fish from Uttara had a higher MPs concentration (36 MPs/g) compared to Jatrabari (25 MPs/g). Among fish species, Glossogobius giuris showed the highest MPs bioaccumulation due to its feeding habits and morphology. Fiber-shaped MPs were most prevalent in all fishes (79–93%) except Glossogobius giuris (fragments, 51%). Fourier-transform infrared spectroscopy (FTIR) analysis identified 19 different polymer types, with high density polyethylene (HDPE), ethylene vinyl acetate (EVA) and polyamide (PA) being commonly found in all organs. The experimental study confirmed that large-sized PVC MPs (1.18 mm-300 μm) had a greater negative impact on fish growth (length) and caused more physical deformities (particularly intestinal injuries) compared to small-sized PVC MPs (150 μm–75 μm). Moreover, fish exposed to larger diameter MPs experienced highest physical weight and depth loss among exposed groups. Large-sized PVC MPs bioaccumulated highest in fish compared to small-sized PVC MPs. Similar to market fish, kidney in the experimental fish had the highest MPs bioaccumulation (6.5 MPs/g), followed by liver (5.2 MPs/g) and intestine (4.8 MPs/g), with a dominance of fibers despite the presence of high concentration of fragments in the food source. Statistical analysis also supported a clear correlation between increasing MPs size and adverse effects on fish growth and health. Urgent action is needed to curb microplastic pollution and protect ecosystems and human health.

Evaluation of visible implant elastomer (VIE) tags for use in supplementation of an endangered estuarine fish

AbstractObjectiveDelta Smelt Hypomesus transpacificus are thought to be close to extinction in the wild, which has spurred multiagency conservation efforts to supplement their population. In conjunction with these recent efforts, monitoring is needed to assess the effectiveness of supplementation. Such monitoring often uses large‐scale tagging of released fish to distinguish between hatchery‐origin and wild‐origin fish that are captured during later surveys.MethodsIn this study, we evaluated the use of visible implant elastomer tags in Delta Smelt to determine whether fish survival, fish growth, or tag retention were dependent on (1) tag color (blue, green, orange, red, yellow, and no‐tag control) or (2) tagged body location (posterior‐dorsal, anterior‐dorsal, mid‐lateral line, and no‐tag control).ResultOver 165 days of the first experiment, there was no difference in growth rate (mean = 0.073 mm/d, range = 0.072–0.075 mm/d) or survival (mean = 68%, range = 63–77%) among tag colors. Across all color groups, mean tag retention was 96% (range = 87–100%). Over 120 days of the second experiment, tag location had no influence on fish growth rate (mean = 0.064 mm/d, range = 0.062–0.067 mm/d) or survival (mean = 50%, range = 43–58%). For the surviving fish in experiment 2, the tags that were placed at the mid‐lateral line were retained less (84% on day 120) than those at posterior‐dorsal and anterior‐dorsal locations (99% and 98%, respectively).ConclusionOur results suggest that visible implant elastomer tagging is a suitable method for marking adult Delta Smelt (&gt;50 mm fork length) for up to 165 days and can be useful for conservation monitoring efforts.