Anguilla Bicolor Research Articles

Highly contiguous genome assembly and gene annotation of the short-finned eel (Anguilla bicolor pacifica)

In East Asia, anguillid eels are commercially important. However, unlike other species, they have not been successfully cultivated throughout their lifecycle. Facing population decline due to overharvesting and environmental pressures, the industry is turning to alternatives, such as Anguilla bicolor pacifica (short-finned eel). However, genomic data for short-finned eels are unavailable. Here, we present in-depth whole-genome sequencing results for short-finned eel obtained using two sequencing platforms (PacBio Revio, and Illumina). In this study, we achieved a highly contiguous genome assembly of the short-finned eel, comprising 19 pseudochromosomes encompassing 99.76% of the 1.087 Gb genome sequence with an N50 of 16.88 and 61.07 Mb from contig and scaffold, respectively. Transcripts from four different tissues led to the annotation of 23,095 protein-coding genes in the eel genome, 98.66% of which were functionally annotated. This high-quality genome assembly, along with the annotation data, provides a foundation for future functional genomic studies of short-finned eels.

Growth performance of eel fish (Anguilla bicolor) which are maintained in containers of different colors

Performance of Eel (Anguilla bicolor) maintened in containers of different colors. Growth is the main driver in increasing the profitability of aquaculture. In addition to maintenance management the color of the container is also a factor supporting the growth of eels. This study aims to determine the effect of the color of different rearing containers on the growth and appetite response of eel. The test fish used were elver stage eels with an average weight (129 ±131g). The method used is an experiment with two treatments they are grey and green. The test fish were placed in a container measuring 19x4 m2 and a water level of 1m with a stocking density of 1100 individuals each, 30 days of rearing. The variables observed were growth performance including SR (Survival Rate), ADG (Average Daily Growth), FCR (Food Conversion Ratio), SGR (Specific Growth Rate). The results obtained indicated that there was a significant difference in the average growth of fish reared in grey and green containers. Grey container treatment was proven to get higher yields with average final weight values (192.4 ± 4.5 g), FCR (1.01 ± 0.02), ADG (2.01g/day ± 0.06), SGR (1 .25%BW/day±0.02). Based on the results of the study it can be concluded that there is a significant difference in the growth of eels reared in ash and green containers. The color of the ash container proved to be better in supporting growth performance.Keywords: Elver; Green; Grey; Nocturnal

Genetic structure and demographic history of Anguilla bicolor from Tanzania based on mitochondrial cytochrome oxidase I sequence: Implications for effective management and conservation strategies

Abstract A genetic analysis was conducted on Anguilla bicolor from Tanzania using the mitochondrial COI region. The study aimed to understand the population genetic structure and demographic history of A. bicolor. In this study, 42 samples of A. bicolor were collected from the Lower Rufiji River Basin and Pangani River in Tanzania between January and June 2023. The mtDNA COI sequences of 65 A. bicolor from various Indo‐Pacific countries were retrieved from GenBank. 2. The findings revealed an overall high haplotype diversity (0.83 ± 0.033) and moderate nucleotide diversity (0.63% ± 0.000). The findings revealed an overall high haplotype diversity (0.83 ± 0.033) and moderate nucleotide diversity (0.63% ± 0.000). A limited genetic differentiation between populations was observed (FST = −0.00322, p = 0.0494), indicating gene flow, leading to an absence of population structure. The haplotype network tree also supported a panmictic stock in the Indo‐Pacific region with 44 haplotypes clustered around three principal haplotypes. Furthermore, the significantly overall negative values of both Tajima's D (−2.27, p = 0.002) and Fu's Fs (−26.36, p = 0.000) and the multimodal mismatch distribution suggested the presence of multiple demographic events in A. bicolor populations. Given the lack of substantial genetic structure among populations, managing the fishery as a single‐stock unit is advised, aligning with the current fisheries management practices in Tanzania. It is also crucial to ensure habitat quality along migratory paths to facilitate genetic exchange and long‐term species viability.

Effects of vitamin C dosage levels on growth and survival rate of sidat fish (Anguilla bicolor, McClelland, 1844)

Eel is a species with high economic value, but its slow growth and low survival rate are problems that need to be addressed through the development of effective cultivation technology. This study aimed to investigate the effects of vitamin C dosage on the growth and survival of eels (Anguilla bicolor). This study was conducted at the UPR. Mina Mandiri, Beutong District, Nagan Raya Regency, during the period August to October 2023. The method used was a completely randomized design with four treatment levels and three replications, namely 0, 200, 300, and 400 mg/kg feed. ANOVA results showed that the dose of vitamin C had a significant effect on the growth and survival of eels (P < 0.05). Further tests using Duncan's method showed significant differences between treatments in growth parameters, but there was no significant difference in survival. The 200 mg/kg feed dose showed the highest and optimal results in terms of increasing the growth and survival of eel fish.Keywords: Culture technology; eel; growth; vitamin C

The diversity, distribution, biomass, and conservation status of ichthyofauna of the Singkil peat swamp in Aceh Province, Indonesia

Abstract. Razi NM, Nasir M, Khalidin K, Savira D, Najmi I, Mahfud M, Dermawan F, Fadli N, Muchlisin ZA. 2023. The diversity, distribution, biomass, and conservation status of ichthyofauna of the Singkil peat swamp in Aceh Province, Indonesia. Biodiversitas 24: 6661-6674. The land conversion of the Singkil peat swamp into oil palm plantations poses a significant threat to the aquatic ecosystem, with potentially detrimental consequences for fish biodiversity. Several reports showed that there was no data on fish diversity in the Singkil peat swamp despite the damage occurring in the area. Therefore, this study aimed to analyze the diversity, distribution, biomass, and conservation status of Ichthyofauna in the Singkil peat swamp waters. Sampling was carried out at 13 locations from July 2023 to August 2023, and the samples were caught using gill nets, casting nets, fishing rods, and traps. A total of 934 samples were collected during the sampling, belonging to 39 species, 31 genera, and 26 families. The results showed that Cyprinidae was the most dominant family, with an average diversity index of 1.23, indicating the medium category. The average dominance index was 0.42, which was placed in the low category. Channa striata (Bloch, 1793) and Trichopodus trichopterus (Pallas, 1770) had the highest frequency of occurrence and were found in seven locations out of 13 surveyed. Furthermore, these species were categorized as frequently found based on their availability. The average fish biomass was 288.75 kg/ha, with C. striata having the largest value. Among the 39 fish species obtained, 3 species were classified as near threatened, including Anguilla bicolor (McClelland, 1844), Mystus bimaculatus (Volz, 1904), and Kryptopterus minor (Roberts, 1989), while 1 invasive sample was recorded, namely Oreochromis niloticus (Linnaeus, 1758) in one location.

Object tracking-based deep learning for calculating the quantity of eel seedlings (Anguilla bicolor)

Anguilla bicolor is a highly economically valuable species of eel, whose cultivation needs to be carried out to the maximum. One of the factors supporting successful aquaculture is the optimal stocking density. The current calculation method for determining seedling quantity for stocking density is ineffective for large-scale cultivation. Therefore, in this study, an object-tracking-based calculation method using deep learning was applied to address this issue. Deep learning using YOLO v8 is an advanced method for counting and detecting objects including fish. This algorithm was used with the addition of the ByteTrack algorithm for object tracking and supervision for object counting. Object tracking is applied such that during seed counting, moving objects can be tracked and not counted repeatedly. Training was conducted on two datasets with different labels, namely the head and tail parts, using 300 epochs, 16 batches, and learning rate of 0,001 and 0,01. Based on the training results, the model with the head label has higher precision and recall than the tail-labelled model, with values of 0,91 and 0,93 respectively. The model performed well at a stocking density of 63 individuals/m², with accuracy and F1 scores of 90,91% and 0,95 respectively.

Characterization and Effect of Processing on Parvalbumin Content in Indonesian Shortfin Eel (Anguilla Bicolor-bicolor)

Indonesian shortfin eel (Anguilla bicolor bicolor) is a high economic value fish and a high nutritional content. However, their utilization can be limited because of hypersensitivity cases in individuals allergic to fish. This study aimed to determine the characteristics of the fish major allergenic protein, parvalbumin in different parts of the eel fillet and the effects of boiling technique on the content of this protein. The samples were boiled with 100 mL of water in an Erlenmeyer flask at 95°C for 10 min. The eel fillet was divided into three parts: the front, middle, and rear part of the body. Protein profiles from each part were identified using sodium dodecyl sulfate-polyacrylamide gel electrophoresis and Bradford assays. Parvalbumin was further purified by ammonium sulfate precipitation. The concentration of protein in the different parts of the eel was not significantly different, whereas the processing treatments (meat with water (F1 extract) and meat without water (F2 extract)) affected protein concentration. Eel meat contained proteins with molecular weights ranging from 10 to 186 kDa. Parvalbumins are highly water-soluble, as their content was reduced in the fillet, but were observed at a high concentration in the water after boiling. Parvalbumins of eel were purified by ammonium sulfate 70-90% with high purity. Interestingly, two different bands were observed in SDS-PAGE, suggesting the presence of a protein variant. The molecular weight of parvalbumin obtained from purification ranged from 10 to 11 kDa, similar to that of other fish.

The potential of shallot skin powder and actinomycetes metabolites as antimicrobe and antibiofilm in the treatment of eel (Anguilla bicolor bicolor) infected with Aeromonas hydrophila

BackgroundEel (Anguilla bicolor bicolor) is an Indonesian export commodity. However, it is facing a problem related to Aeromonas hydrophila, which can cause motile aeromonas septicemia (MAS) and produce biofilm formation. Problem with antibiotic resistance challenges the need of an alternative treatment. Therefore, it is important to explore a solution to treat infection and the biofilm formed by A. hydrophila.ObjectivesIn this study, we used shallot skin powder and actinomycetes metabolite 20 PM as antimicrobe and antibiofilm to treated eels infected with A. hydrophila.ResultsShallot skin powder (6.25 g 100 g−1 feed) and Actinomycetes 20 PM metabolite (2 mL 100 g−1 feed) were found to be effective as antimicrobe and antibiofilm agent in treating eels infected with A. hydrophila. Eel treated with antibiotic, shallot skin powder, and actinomycetes metabolite had 80%, 66%, and 73% survival rates, respectively. Other indicators such as red blood cell count, hemoglobin, and hematocrit were increased, but white blood cell count and phagocytic activity were dropped. Biofilm destruction were analyzed using scanning electron microscopy to determined antibiofilm activity of actinomycetes metabolite against biofilm of A. Hydrophila.ConclusionsShallot skin powder and actinomycetes metabolite were potential to treat infection of A. hydrophila in eel as an alternative treatment to antibiotics.

Polyunsaturated Fatty Acids from Eel Extract Attenuate Gastritis and Hepatotoxic by Indomethacin-Induced in Rats

Nonsteroidal anti-inflammatory drugs (NSAIDs) potentially induce hepatotoxicity and ulcerative lesions in the stomach. Several studies have been conducted on the benefits of natural resources to overcome the problem of drug side effects. However, the use of fishery resources, such as the eel (Anguilla bicolor), for medicine has not been widely studied. Eels are rich in omega-3 polyunsaturated fatty acids with antioxidant and anti-inflammatory effects. Therefore, this study aims to determine the gastroprotective and hepatoprotective effects of polyunsaturated fatty acids extracted from eel (FaE). The experimental models were 42 male rats divided into seven groups. The experiment was performed for 14 days by orally administering FaE samples. On the 15th day, the rats were orally induced with indomethacin (48 mg/kg). After 8 h of induction, they were euthanized using ketamine and xylazine. Furthermore, blood samples were collected from the animals to measure the levels of aspartate aminotransferase and alanine aminotransferase. Malondialdehyde (MDA) and glutathione (GSH) levels were measured, while the histology of the liver and stomach were examined. The results showed that the administration of FaE from a dose of 1000 mg/kg significantly attenuated the liver and stomach damage caused by indomethacin. The influence of oxidative stress inhibition on damage is characterized by inhibition of the increase in MDA and a decrease in GSH. This research shows that FaE has the potential to inhibit liver and gastric damage due to the use of NSAIDs. However, further investigation needs to be conducted on other specific parameters of the inflammatory mechanism.

Comparison of Reproductive Aspects of the Tropical Eel Anguilla bicolor (McClelland 1884) in Freshwater and Estuarine Habitats

The tropical anguillid eel, Anguilla bicolor McClelland, experiences significant growth up to the adult size in both freshwater and estuarine ecosystems, encountering salinity gradients that may impact their reproduction. Therefore, this study aimed to investigate the reproductive aspects of A. bicolor collected from Serayu River (freshwater) and Segara Anakan (estuary), Cilacap, Central Java, during July 2020 field surveys. The examined parameters included eye index (EI), fin index (FI), gonadosomatic index (GSI), hepatosomatic index (HSI), and sex ratio of eel specimens in freshwater and estuary. Furthermore, the total length (TL) and body weight (BW) ranged from 260 - 630 mm and 18 - 419 g in freshwater, and 260 - 630 mm and 18 - 447 g in estuary. Significant differences (P<0.01) were observed in the reproductive characteristics between the two habitats (P<0.01), with higher eye index, fin index, gonadosomatic index, and hepatosomatic index in freshwater-caught eels than the values obtained in estuary inhabitants. The mean of these four parameters were 6.99 ± 2.98%, 4.08 ± 0.71%, 1.70 ± 1.13%, and 1.92% ± 1.07 in freshwater, while 3.48 ± 1.60%, 3.45 ± 0.479%, 1.12 ± 0.23%, and 0.28 ± 0.19% were found in estuary. The sex ratio was significantly affected by habitat, with female eels dominating in freshwater (62.5%) compared to estuary (32%). These results suggested that eels in freshwater habitats might exhibit early gonadal maturation compared to those in estuary.

Effects of Indonesian Shortfin Eel (Anguilla bicolor) By-Product Oil Supplementation on HOMA-IR and Lipid Profile in Obese Male Wistar Rats.

The prevalence of people being overweight and obese has increased globally over the past decades. The use of omega-3 fatty acids-a compound usually primarily found in fish oil-has been known to improve the metabolic profile of obese patients. As the demand for eels increases, the number of waste products from the eels increases and creates environmental problems. This study was conducted to investigate the effect of a newly discovered Indonesian Shortfin eel by-product oil supplementation on the Homeostasis Model Assessment-Estimated Insulin Resistance (HOMA-IR) and lipid profiles of obese male (Lee index ≥ 0.3) Wistar rats (Rattus norvegicus). The oil was extracted from waste products (heads). Fifteen obese rats were divided into three groups and were administered NaCl (C), commercial fish oil (CO), and Indonesian shortfin eel by-product oil (EO). All groups had statistically significant differences in total cholesterol, LDL, and triglyceride levels (p < 0.05). The CO and EO group showed a significant decrease in total cholesterol, LDL, and triglyceride after treatment. However, no significant difference was found in HDL levels and HOMA-IR. The supplementation of Indonesian shortfin eel by-product oil significantly improved lipid profile while effectively mitigating environmental challenges.

Alternate Day Feeding as a Cost-effective Strategy for Tank Culture of the Pacific Shortfin Eel Anguilla bicolor pacifica

There is a growing interest in the aquaculture of tropical anguillid eels as an export commodity. However, studies on feeding strategies, and the present demand to reduce feed costs need to be addressed to ensure the economic viability of eel farming. In this study, the effects of daily (DF) and alternate day (ADF) feeding on growth, feed utilization, body composition, blood chemistry, liver and intestinal morphology, and economic viability in the Pacific shortfin eel Anguilla bicolor pacifica were examined. Each feeding group of 30 elvers (166.25 ± 16.23 g mean initial wt) were randomly stocked in triplicate 4 m3 outdoor concrete tanks. These were fed for 155 d with formulated eel powder diet (49.77% crude protein; 10.21% crude lipid) made into a paste. Growth and survival were not significantly different between the two feeding groups. However, feed efficiency was improved in the ADF group, with significantly higher protein efficiency ratio (0.63) than in the DF group (0.39). Feed conversion ratio (FCR) was lower in ADF (3.85) than in the DF group (6.44), resulting in a 40% reduction in total feed consumption. Biometric indices, body proximate composition, and blood chemistry were not significantly affected. Likewise, liver and intestinal morphology showed no apparent alterations between groups. Partial costs-and-returns analysis showed that ADF yielded higher net profit and profit index. These results suggest that feeding on alternate days promote compensatory growth, better feed utilization, and normal physiological condition of A. bicolor pacifica, and reduce feed cost in the rearing process. Therefore, alternate day feeding should be promoted as a sound feed management strategy in the tank culture of tropical anguillid eels.

Utilization of Maggot Meal for Eel Fish Feed (Angguila bicolor bicolor)

The increase in aquaculture production must be accompanied by effective and efficient feed, thus requiring innovation to obtain the appropriate feed ingredients. This research aims to determine the effect of maggot meal and commercial eel feed on the growth, protein digestibility, and production cost of eel (Anguilla bicolor bicolor) aquaculture. Eels were reared in 15 aquariums measuring 60 × 40 × 40 cm, equipped with water filters, with five treatments and three replications. The treatments consisted of maggot meal + eel feed in the following proportions: A1 (0% + 100%), A2 (25% + 75%), A3 (50% + 50%), A4 (75% + 25%), and A5 (100% + 0%). The feed was given twice a day, morning and afternoon, according to the requirements. Data on growth rate and feed efficiency were collected every two weeks, while protein digestibility and production cost were calculated at the end of the 60-day study period. Treatment A2 showed a daily growth rate of 1.218±0.409%, which approached the growth rate of the commercial feed treatment (A1). Treatment A5 had a growth rate of 0.309±0.218% per day, while treatment A1 had a growth rate of 1.440±0.364%. The best feed conversion ratio (FCR) in each phase was obtained in treatment A1, with a value of 1.862±0.086. The highest FCR was found in treatment A5, with a value of 6.455±1.158 in each phase. The best feed efficiency was observed in treatment A2 at 82.79%, while the lowest digestibility was in treatment A4 at 34.88%. The digestibility of feed in treatment A2 was the highest at 58.42%. According to the research findings, the production cost per kilogram of eel was more cost-effective and required less time in treatment A2, with a feed cost of Rp 105,000/kg. The utilization of a combination of maggot meal and commercial feed shows potential as a feed that can be used to enhance growth rate.

Application of herbal probiotics in feed on growth and blood profile of elver eels (Anguilla bicolor McClelland, 1844)

Shortfin eel cultivation in Indonesia has shown significant development in aquaculture. However, various challenges still hinder its successful implementation. This study aims to investigate the impact of herbal probiotics on the growth and blood profile of elver eels (Anguilla bicolor). The research was conducted at UPR Mina Mandiri in the Beutong District of Nagan Raya Regency, from August to October 2022This research was conducted at UPR Mina Mandiri, Beutong District, Nagan Raya Regency, from August to October 2022. A Completely Randomized Design (CRD) with five treatment levels and three replications was employed for this study. The treatments consisted of herbal probiotics added to the eels' feed: 0, 15, 20, 25, and 30 ml/kg. The data obtained from the experiment were subjected to an analysis of variance (ANOVA) to assess the significance of the results. ANOVA test results show that probiotics significantly affect survival rate, absolute weight growth, specific weight rates, feed efficiency, and the elver eel blood profile (hemoglobin, erythrocytes, and leukocytes). (P0.05). Duncan's advanced test revealed significant differences in the growth parameters and blood profiles among the various treatments. Treatment B, which utilized a dosage of 15 ml/kg of feed, displayed the most favorable outcomes. It achieved a survival rate of 93.33%, absolute weight growth of 2.69 grams, a specific growth rate of 1.73%, and a feed efficiency of 48.56%. Additionally, the blood profile measurements for treatment B were as follows: hemoglobin levels ranged from 9.53 to 9.73 g/dl, erythrocyte count ranged from 1.12 to 1.23 x 103 cells/mm3, and leukocyte count ranged from 120 to 133 x 103 cells/mm3.Keywords:blood profilefish healthgrowthshortfin eels probiotics

Production and business performance of Anguilla bicolor fingerlings in a recirculation system with different stocking densities

Eel (Anguilla bicolor) in the grow-out culture requires good fingerling seeds. Increasing the eel productivity can be done by increasing the stocking density, that should be balanced with good environmental and feed management. This study aimed to analyze the production and business performance of fingerlings in a recirculation system to increase the eel survival and growth rate. The study used a completely randomized design with three different stocking densities, namely 4 g/L (A), 5 g/L (B), and 6 g/L (C). The average weight of each fingerling was 20 ± 4.09 g, that was kept in a 1.5-m3 pond with a recirculation system. Feeding was performed two times a day using commercial feed with probiotic supplementation. The results showed that different stocking densities significantly affected feed conversion ratio, total biomass weight, and coefficient of variance. However, different stocking densities had no significant effect on survival rate, absolute weight growth rate, specific weight growth rate, and condition factor. The C treatment obtained the highest profit with an R/C ratio of 1.20 ± 0.03. The best production and cultivation performance of eel fingerling in a recirculation system with different stocking densities is found in treatment C (6 g/L).&#x0D; &#x0D; Keywords: Anguilla bicolor, business performance, production performance, recirculation system, stocking density&#x0D; &#x0D; ABSTRAK&#x0D; &#x0D; Budidaya ikan sidat (Anguilla bicolor) pada segmen pembesaran memerlukan benih yang baik khususnya untuk benih fingerling. Upaya peningkatan produksi benih ikan sidat dapat dilakukan dengan peningkatan padat tebar yang diiringi dengan manajemen lingkungan dan pakan yang baik. Tujuan penelitian ini menganalisis kinerja produksi dan kinerja usaha pada pemeliharaan fingerling dalam sistem resirkulasi sehingga meningkatkan kelangsungan hidup dan pertumbuhan. Penelitian menggunakan rancangan acak lengkap yang terdiri atas 3 perlakuan padat tebar dengan tiga ulangan, yaitu padat tebar 4 g/L (A), 5 g/L (B), dan 6 g/L (C). Fingerling ikan sidat yang digunakan berbobot awal 20 ± 4,09 g/ekor, yang dipelihara dalam bak 1,5 m3 dengan sistem resirkulasi. Pakan diberikan dua kali sehari berupa pakan buatan komersial yang diberi probiotik. Hasil penelitian menunjukkan bahwa padat tebar berpengaruh nyata terhadap parameter rasio konversi pakan, laju pertumbuhan mutlak biomassa, dan koefisien keragaman bobot tetapi tidak berpengaruh nyata terhadap tingkat kelangsungan hidup, laju pertumbuhan mutlak bobot, laju pertumbuhan spesifik bobot, dan faktor kondisi. Hasil analisis kinerja usaha budidaya fingerling dengan padat tebar berbeda menunjukkan berbeda nyata dan sebanding dengan kinerja produksi. Perlakuan C memberikan keuntungan tertinggi dengan rasio R/C sebesar 1,20 ± 0,03. Kinerja produksi dan kinerja usaha budidaya fingerling ikan sidat (Anguilla bicolor) dalam sistem resirkulasi dengan padat tebar berbeda terbaik terdapat pada perlakuan C (6 g/L).&#x0D; &#x0D; Kata kunci: Anguilla bicolor, kinerja produksi, kinerja usaha, padat tebar, sistem resirkulasi

Feeding frequency on survival, growth, blood glucose of glass eel, Anguilla bicolor bicolor cultured in a recirculating aquaculture system

Indonesian shortfin eel, Anguilla bicolor bicolor is one of the eel species that high market demand both for local and export. Feeding frequency is an important that related to production for culture. The purpose of this experiment is to determine the optimal feeding frequencies on survival and growth of shortfin eel at glass eel to elver stages cultured in a recirculating aquaculture system. Four treatments of different feeding frequencies and three replicates each were performed. The treatments were as followed A) 1 time a day; B) 2 times a day; C) 3 times a day; and D) 4 times a day. The result showed that the feeding frequency affect the survival, length and weight growths, and glucose value. The best of survival rate (82.61±3.15%), weight (1.91±0.28 g) and length (10.64±0.45cm) found at feeding frequency 3 times a day compared to the others (P<.0.05). Blood glucose value increases with increasing feeding frequency. Water quality such as dissolved oxygen (DO), temperature and pH were within the optimal range. Three times a day of feeding frequency is recommended for applying on glass eel culture in a recirculating aquaculture system.

Response of Anguilla bicolor Glass Eel to Different Light Colors

The response of eel fish (Anguilla bicolor) glass eel stadia to different light is fundamental knowledge for developing fishing methods and conserving fish resources. The study aimed to describe how glass eel fish react to different types of light. In the laboratory, glass eels were observed responding to red, blue, and white LED light versus no light as controls. Glass eels ranging in size from 4.0 to 6.1 cm and weighing up to 0.28 g were caught in the Pelabuhanratu estuary of the Cimandiri River. Observations were made for 31 days, beginning five days after the glass eel was captured. The Mann Whitney and Kruskal-Wallis tests were used to describe differences of the glass eel's response to light. Observations showed that glass eels responded more to dark zones with values above 80% when compared to zones given red, blue, and white LED light. The percentage of fish in red LED lights was 23±0.22% higher, with the number of fish on blue LED lights by 10±0.21% and white LED lights 8±0.15% (p&lt;0.05, Kruskal-Wallis). The difference in response to light can be used for glass eel catching applications, especially lamps for eel fish aids and eel conservation to create fishing zones and eels.Keywords: Anguilla bicolor, eel behavior, glass eel, LED light, response to light

Gonad Homogeneity, Maturity, and Gonado-Somatic Index of Wild Indonesian Eel (Anguilla bicolor bicolor McClelland, 1844)

Abstract The current study was conducted to investigate the homogeneity of gonad maturity in Anguilla bicolor bicolor, and whether Gonado-Somatic Index (GSI) is a reliable indicator of this maturity. Eel samples were obtained from fishermen at Segara Anakan, Cilacap, Central Java, Indonesia in December 2015, and May 2017. Fourteen specimens were analyzed based on their gonad histological structure from cranial, medial, and caudal portions and were measured for GSI values. The present study shows that there is a synchronization of oocyte maturity time on the medial, cranial and caudal parts. It might suggest that during the maturation process, Anguilla develop into silver eels and return to the sea to spawn. The highest GSI value is 2.67 in the female eel containing the highest number of mid-vitellogenic oocytes. Based on these results, it can be suggested that GSI are a suitable parameter for measuring the gonadal maturity of female A. bicolor bicolor. Keywords: Gonadal maturity, Homogeneity, Indonesian eel, A. bicolor bicolor, Segara Anakan

Differences in Swim Bladder Histology of &lt;i&gt;Anguilla bicolor bicolor&lt;/i&gt; at Various Stages of Sexual Maturity

The current study observed the histological differences of the swim bladder of the tropical eel, Anguilla bicolor bicolor, as an adaptation resulting from hydrostatic change. A total of 15 eels were collected from Pasir Puncu, Keburuhan, Purworejo and Segara Anakan, Cilacap, Indonesia in June 2017, September 2020, and April 2021. The eels were grouped into 4 stages based on the silvering stage and sex, namely: yellow undifferentiated, yellow female, silver male, and silver female. The average length and body weight of yellow undifferentiated eels were 255.07 ± 45.91 mm and 13.66 ± 8.5 g, respectively; for yellow female, the values were 374.35 ± 41.51 mm and 56.5 ± 12.02 g; for silver male, the values were 432.43 ± 15.15 mm and 140.29 ± 13.85 g; and for silver female were 702 ± 0.00 mm and 545 ± 11.31 g. The present study successfully recorded the histological structure of the swim bladder of A. bicolor bicolor in silver male and silver female stages. Silver males and females displayed a greater significant development of the swim bladder than yellow stages in the gas gland, mucosa, and submucosa layers. These results suggest that an increase in the gas gland thickness allows a greater contribution from gas to gas secretion, the mucosa exerts a mechanical effect on the newly formed gas bubbles, and the submucosa thickness reduces gas conductivity from the swim bladder wall.

The effect of bentonite utilization on the physicochemical characterization of eel (Anguilla bicolor bicolor) oil by wet rendering

Eel fish is a fishery commodity that has important economic worth in an international trade market. Eel fish (Anguilla bicolor bicolor) has a protein, carbohydrate, and fatty acid. The fatty acid composition in eel fish makes it a potential source of fish oil for health supplement applications. The extraction method and the purification process determine the quality of the fish oil produced. Wet rendering, or wet extraction is considered to be the most commonly used fish oil separation process. However, this process must be subjected to additional treatment, namely purification to produce quality fish oil. This study aims to determine the effect of the addition of bentonite on the physicochemical profile of eel. The oil is extracted from all of the body eel fish parts except waste like intestines. The crude fish oil thus obtained is then further processed with bentonite for refining to obtain pure fish oil. The results showed the quality of eel oil in respectively: acid number 1.47±0.02 mg KOH/g fat, iodine number 105.51 ± 0.62 Wijs, saponification number 226.12±3.86 mg KOH/g and peroxide value 11.86±0.0221 mEq O2/kg. There is a change in physicochemical profile after purification using bentonite. The conclusion, was that utilization of bentonite for eel oil extraction using the wet rendering process may increase the quality of fish oil.