Eel Samples Research Articles

Genetic Diversity and Distribution of Haplotypes of Freshwater Eel in Baltic Lakeland Based on Mitochondrial DNA D-Loop and Cytochrome b Sequence Variation

The European eel (Anguilla anguilla (L.)) is a unique catadromous euryhaline fish and the only anguillid eel species classified as ‘critically endangered’. The Baltic Lakeland area contains naturally recruited and introduced eels. There is great uncertainty regarding a baseline for the location and number of naturally dispersed eels in the region. Little is known about the genetic structure of the European eel populations in Baltic countries. The estimation of population genetic structure is important for the efficient management of naturally recruited and introduced eels. Two mitochondrial regions were used to investigate the genetic structure within and between eel samples from 11 waterbodies. In this study, new, unique, and widely distributed haplotypes were revealed. The studied eel population in the Baltic Lakeland shows high genetic diversity, which is possibly a result of intensive restocking programs. Sequences characterized for Anguilla rostrata were revealed in both mitochondrial regions. Understanding the genetic structure of eel populations worldwide is crucial for conservation efforts. Eel restocking in waterbodies where natural migration is restricted contributes to diversity loss for the world gene pool of eels.

DNA Barcoding of Freshwater Eels Anguilla spp from Kuari River Based on Cytochrome C Oxidase Subunit I (COI) Gene

Graphical Abstract Highlight Research Freshwater eels in Kuari River consisted of two species marmorata and A. bengalensis Anguilla marmorata had the highest similarity of 99.82%-100%, while bengalensis indicated the highest identity of 99.84%-100% to the same species in the GenBank database. Phylogenetic species indicated that Anguilla marmorata and Anguilla bengalensis form two different sub-clusters. The water quality in the Bengkulu Kuari River were still in tolerance for fish growth and survival. Abstract Freshwater eels (Anguilla spp.) are classified in the family Anguillidae, and included in the catadromous group. This study aimed to determine the COI gene sequences of the mitochondrial DNA, analyze the genetic distances, and phylogenetics, and characterize the physical and chemical parameters of between freshwater eels habitat in the Kuari River Bengkulu. This research was conducted from November 2020 – April 2021. The methods used in barcoding eel species were DNA isolation, DNA amplification using PCR (Polymerase Chain Reaction), electrophoresis, and sequencing of COI gene regions in mtDNA. The COI mtDNA gene fragments were obtained from PCR results with an annealing temperature of 50°C for 30 seconds in 35 cycles. BLASTn analysis of eel samples AM3 and AM4 had the highest similarity of 99.82%-100% to Anguilla marmorata, and samples AB2-AB5 indicated the highest identity of 99.84%-100% to Anguilla bengalensis. Phylogenetic species indicated that Anguilla marmorata and Anguilla bengalensis form two different sub-clusters. The water qualities in the Bengkulu Kuari River were temperatures 26.5-27.5oC, pH 7.1-8.7, dissolved oxygen 6.19-9.54 mg L-1, brightness 21-47 cm, ammonia 0.16-0.41 mg L-1, total alkalinity 20–52 mg L-1, TDS 33–49 mg L-1, salinity 0.3-0.4 ppt and water velocity 0.5-0.8 ms-1. The COI gene in DNA barcoding is very appropriate to be used for the identification of Anguilla spp species by comparing the DNA sequence of the COI gene with the existing database in the Genbank.

Measurement of Heavy Metal Mercury (Hg) Content in The Swamp Eel (Monopterusalbus) as a Bioindicator from Lake Rawa Taliwang

The presence of heavy metals in Lake Rawa Taliwang can originate from various activities in the upstream river, around settlements, and within the lake itself. Mercury (Hg) is a highly toxic heavy metal due to its neurotoxic nature, affecting both organisms and humans. One of the fish found in Lake Rawa Taliwang is the swamp eel. Swamp eels are often caught for consumption and cultured by the local community. This study aims to determine the mercury (Hg) concentration in swamp eels (Monopterus albus) and assess their suitability for consumption. Sampling was conducted using purposive sampling technique at two stations with two replications at each station. Data analysis involved determining mercury concentration in the swamp eel samples using Atomic Absorption Spectroscopy (AAS). The results showed that the mercury concentration in swamp eels from Lake Rawa Taliwang was 0.13 mg/kg. According to the BPOM regulation no. 9 of 2022, the mercury concentration in these swamp eels is still below the permissible limit for metal contamination in food. This indicates that swamp eels were taken from Lake Rawa Taliwang is safe for consumption.

Analysis of The Heavy Metal Cd Content in Ricefield Eel from Rawa Taliwang Lake, West Sumbawa Regency

It is important to carry out research on heavy metal in fish body. The specific aims and targets of this research are: Want to know the metal content of Cadmium (Cd) in Ricefield eels (Monopterus albus) which comes from Rawa Taliwang Lake. The specific benefit is to protect consumers who consume fish from heavy metal contamination. The research was carried out at Rawa Taliwang Lake, namely in an area that is submerged in water. There are 2 research stations, namely in the eastern and western parts of the lake. Data collection method was carried out using traps (Bubu). Four Ricefield eel samples were taken at each station. Next, the rice eel samples were put into a plastic bag and then stored in a sample box. The research samples were then analyzed at the Mataram Uviversity analytical laboratory and at Environmental Laboratory of the Environmental and forestry services West Nusa Tenggara Province. The data analysis method is carried out by taking the tissues from the Ricefield eel muscles, and then analyzed for Cd heavy metal content by using Atomic Absorption Spectrophotometer. Measurement of heavy metals in Ricefield eel tissue was carried out by adding concentrated HNO3 and HClO4 , heated at a temperature of 60-70ºC for 2-3 hours until the solution was clear. Samples are ready to be measured with AAS using an air-acetylene flame. The conclusion of this research is that the content of Cd heavy metal in Ricefield Eels (Monopterus albus) originating from Rawa Taliwang Lake ranges from 2.55 - 4.01 mg/kg (ppm).

Quality of cultured eels as affected by pollution sources and risk assessment of dioxins and dioxin-like polychlorinated biphenyls

AbstractThe aim of this research was to determine the residues of dioxins and dioxin-like polychlorinated biphenyls in cultured eel and find out the source of pollution and the distribution pattern of eels. One hundred samples of eel, 4 fodder samples, and 12 environmental samples (water, plants, and soil) were collected from 4 cities and counties in Jiangxi Province, China. The contents of 17 kinds of dioxins (PCDD/Fs) and 12 kinds of dioxin-like polychlorinated biphenyls (dl-PCBs) were determined by high-resolution gas chromatography-tandem mass spectrometry, and the exposure risk was evaluated by using risk index. The total toxicity equivalence quantity (TEQ) of dioxin and dioxin-like polychlorinated biphenyls in eel and fodder samples collected in the study area were 0.65 ± 0.31 pg/g and 0.10 ± 0.02 pg/g, respectively. Dl-PCBs were the main dioxin pollution in eel and fodder samples. 2,3',4,4',5-pentachlorodiphenyl and 2,3,3',4,4'-pentachlorobiphenyl were the main contributing monomers. The environmental samples were mainly polluted by polychlorinated dibenzo-p-dioxins (PCDDs), with the main contributing monomer being Octachlorodibenzodioxins (OCDD), while 3,3',4,4',5-pentachlorobiphenyl and 2,3,4,7,8-pentachlorodibenzofuran were the main toxic compounds in eel and fodder. The dioxin pollution of eels cultured in Jiangxi Province was mainly from fodder polluted via dl-PCBs. The meat segment VI (tail) exhibited a strong enrichment effect of polychlorinated benzofurans (PCDFs). It should be the key part for dioxins and dioxin-like polychlorinated biphenyls assessment. Further, the results were helpful to improve the edible safety of eel products and the efficiency of the risk assessment of dioxins and dioxin-like polychlorinated biphenyls in fish. Graphical Abstract

Characterizing Sex Ratios of American Eels ( Anguilla rostrata ) in Louisiana.

The American eel ( Anguilla rostrata) inhabits Louisiana waterways; however, little is known about their life history, population abundance, or behavior. Eels under 400 mm require histologic evaluation to determine sex. We have processed eel gonad samples from 40 sampling locations across Louisiana, as well as across size categories to aid in establishing a sex determination protocol. One hundred and eighteen (118) eel samples have been histologically analyzed to date. The histologic data compliments morphometric, location, and ageing data collected by the Louisiana Department of Wildlife and Fisheries to build an initial understanding of the biological characteristics of American eels in Louisiana.

Relationship between habitat use and individual condition of European eel (Anguilla anguilla) in six estuaries of the eastern English Channel (North-eastern Atlantic ocean)

Brackish habitats are considered important for the facultatively catadromous European eel, but knowledge of eel habitat use strategies and the consequences on their condition, particularly in the estuaries areas, is limited and yet necessary for understanding some features such as growth and maturation in the different habitats that eel inhabit during the continental phase, that might also support assessment and management of local stocks, and contribute to the stock-wide assessment of this panmictic species. This study aimed to characterise and compare the condition of European eels according to their habitat use strategies and local estuarine characteristics. Eels were collected along the salinity gradient in six small and medium-sized estuaries located along the French coast in the eastern English Channel (i.e. the Slack, Wimereux, Liane, Canche, Authie and Somme estuaries). Four condition indices (i.e. Fulton condition factor K, lipid content, hepatosomatic index and health status) were measured on 119 individuals to explore variation with habitat characteristics at the small geographical scale and their habitat use strategies. Eel condition showed clear spatial differences between the six estuaries, with better condition in smaller estuaries. The spatial differences in eel condition appear to be related to variations in their diet composition, corresponding to different availability of macrozoobenthos prey among sites, in turn due to the local hydro-morpho-sedimentary characteristics. Environmental history and movements were reconstructed from the Sr:Ca and Ba:Ca ratios of otoliths from eel samples (N = 37) in both small- and medium-sized estuaries. The Sr:Ca and Ba:Ca ratios were used to distinguish the habitat use strategies and showed that both estuaries had a high proportion of resident eels (81%). Within each estuary, the Sr:Ca and Ba:Ca ratios were sufficiently contrasted to track movements of estuarine resident eels between three resident sectors (i.e. upper, middle and lower estuary). The relationship between eel condition and habitat use showed that inter-habitat shifter eels were in poorer condition than estuarine residents. Eel condition also varied between the three resident sectors, with decreases between eels from the lower to upper estuaries.

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

Effects of preservation by ethanol on δ13 C and δ15 N of three tissues of the critically endangered European eel Anguilla anguilla.

The temporal effects of ethanol preservation on the δ13 C and δ15 N values of tissues excised from European eel Anguilla anguilla were assessed. Preservation significantly enriched δ13 C values of fin and mucus, but not dorsal muscle. The δ13 C enrichment occurred in the initial 15 days of preservation and was independent of initial eel mass. Tissue preservation effects on δ15 N values were negligible. These tissue-specific isotopic shifts should be considered when ethanol preserved eel samples are used.

Molecular identification of critically endangered European eels (Anguilla anguilla) in US retail outlets.

The European eel (Anguilla anguilla) has declined by over 90% since the early 1980s and has been listed as critically endangered. Yet, despite strict export bans from the European Union, the European eel is still sold illegally in many countries. Efforts to monitor the trade of European eels have been primarily concentrated in Asian markets where concerningly high rates of European eel have been reported. Comparably fewer studies have assessed the identities of eel samples from the United States (US), despite the obvious implications for eel conservation. To address this knowledge gap, we purchased 137 eel products (134 freshwater eels and three saltwater eels) from grocers, sushi bars, and restaurants in nine states across the US from 2019 to 2021. Seven samples (5.2%) labeled as freshwater eels (or "unagi") were identified as European eels using a combination of mitochondrial (cytochrome b) and nuclear (18S rRNA) restriction digestion assays, a fast and inexpensive molecular tool for seafood identification that can identify hybrids between European eels (A. anguilla) and American eels (A. rostrata). No hybrids between European and American eels were found and all seven samples identified with restriction digestion as European eels were confirmed by sequencing of cytochrome b and 18S rRNA. Frequency of European eels in US markets did not significantly correlate with state or retail type. Although illegal eel exports are likely reaching US consumers, the frequency of European eel samples in this study of the US market is much lower than found in other non-European countries.

The study of European eel, Anguilla anguilla in the RiverNeretva estuary (Eastern Adriatic Sea, Croatia) using traditional fishery gear

Samples of the European eel, Anguilla anguilla from two different habitats in the River Neretva estuary region were analysed using two different traditional fishery gear, in the period from 2016 to 2019. The monthly eel catches in ten traditional fyke nets in Parila lagoon varied from 4.4 to 12.7 kg (±2.45 kg) in 2016 and 2.4 to 9.6 kg (±2.01 kg) in 2019. There were no statistical differences between monthly and total weights recorded in 2016 and 2019 (t=1.04; p=0.312). The b-coefficient of the length-weight (LW) relationship for the freshwater eel samples varied from 3,1036 to 3,3206 duringtwo-year period of the sampling. The LW relationship for the brackish population was significantly lower (b-coefficient 2,6513). The dominant eel stage in both sites was yellow eel, while silver stage was scarce. The fishery with traditional devices revealed that efficiency of these artisanal tools is low, pointing to poor abundance of eel in their common habitats. The recorded catch using bigger traditional eel trap gear during autumn spawning migrations was also dominated with yellow stage, while silver eel represented only 15,4% of the catch. The infestation of eels with the parasite,Anguillicoloides crassus was significantly higher in freshwater habitat (41% of eel specimens infested) than in brackish, Parila lagoon (7%). Poor efficiency of traditional gear, bad length and weight structure of the population and low b-coefficients of eels in their most important habitat, indicate poor status of European eel population and River Neretva estuarine ecosystems.

Identification of virus infections of European eels intended for stocking measures.

The spread of viral diseases in eels is suggested to severely affect the European eel (Anguilla anguilla) panmictic population. The European Commission has initiated the Eel Recovery Plan (Council Regulation No. 1100/2007) to try to return the European eel stock to more sustainable levels within that measures eel restocking. However, scientific evidence evaluating the efficacy of stocking remains scarce. In addition, knowledge about the impact and contribution of eel stocking on the distribution of infectious diseases is insufficient. In this study, we aimed to investigate virus infections in batches of eels intended for restocking. We analysed samples of glass eels from certified fisheries and farmed European eels from different aquaculture farms. All analysed eels were purchased within a North Rhine Westphalian conservation program. Via a combination of cell culture and qPCR-based techniques, we detected infections of glass eels with the rhabdovirus Eel Virus European X and anguillid herpesvirus 1 infections in farmed eels (10-15 cm).

Dipeptide nanoparticle and aptamer-based hybrid fluorescence platform for enrofloxacin determination.

A novel fluorescence platform was fabricated for enrofloxacin determination by using cDNA-modified dipeptide fluorescence nanoparticles (FDNP-cDNA) and aptamer-modified magnetic Fe3O4 nanoparticles (Fe3O4-Apt). The FDNP were prepared via tryptophan-phenylalanine self-assembling. When magnetic Fe3O4-Apt incubated with standard solution or sample extracts, the target enrofloxacin was selectively captured by the aptamer on the surface of the Fe3O4 nanoparticles. After removing interference by washing with phosphate-buffered saline, the FDNP-cDNA was added, which can bind to the aptamer on the surface of the Fe3O4 nanoparticles not occupied by the analyte. The higher the concentration of the target enrofloxacin in the standard or sample solution is, the less the FDNP-cDNA can be bound with the Fe3O4 nanoparticles, and the more the FDNP-cDNA can be observed in the supernatant. Fluorescence intensity (Ex/Em = 310/380nm) increased linearly in the enrofloxacin concentration range 0.70 to 10.0ng/mL with a detection limit of 0.26ng/mL (S/N = 3). Good recoveries (88.17-99.30%) were obtained in spiked lake water, chicken, and eel samples with relative standard deviation of 2.7-6.2% (n = 3).

Physicochemical Properties and Nutrient Content of Tempe Flour Enriched Eel Flour

AIM: This study aims to evaluate the nutritional content and physicochemical aspect of the combination of eel and tempe flour. METHODS: Samples of swamp eel and tempe flour were combined in a ratio of 1:1 (A), 1:2 (B), 1:3.5 (C), and 1 kilogram of Asian swamp eel meat without additional tempe (D), respectively. Homogenization was done using a sinmag planetary mixer. The sample analysis was performed at the SIG Laboratory (PT. Saraswanti Indo Genetech) on November 16, 2021. The samples were analyzed triple (triplicates). Statistical analysis was performed using GraphPad Prism version 9.3.0 for Mac OS. Variables were analyzed using multivariate ANOVA with 95% CI (0.05). RESULTS: There was a significant difference between Samples A, B, C, and D for every proximate analysis parameter (p = 0.000) p < 0.05. The results showed a significant difference in the unsaturated fatty acid parameter between the groups (p < 0.001). Sample C has the highest B9 (folic acid) content compared to other samples (1258.53 ± 1.39 mcg/100 g) and a significant difference was found between samples (p < 0.0001). CONCLUSION: Tempe flour enriched eel flour can act as a source of folate, due to its high folate content. Tempe flour enriched eel flour could be used as a flour mixture in any food products that require flour to increase folate content.

Meta-analyses of molecular seafood studies identify the global distribution of legal and illegal trade in CITES-regulated European eels

Authentication of seafood products by means of molecular techniques has relevance for food sustainability and security, as well as international trade regulation, linked to transparency in food manufacturing. We focus on the molecular detection of the depleted European eel Anguilla anguilla, a species for which strict international trade regulations are in place since 2010, in studies conducted outside Europe. We found thirteen studies from nine countries (Canada, China, Japan, Malaysia, Peru, Singapore, South Korea, Taiwan, and USA) for which, on average, 59 ± 28% of the 330 sequenced eel samples comprised European eel. Only China, Japan, South Korea, and USA reported the import of European eel in the years prior to sampling. The authentication of eel products demonstrates a global, in part illegal, trade in European eel, covered up by incomplete or fraudulent labelling. This calls into question the compliance with existing national and international trade regulations and its implications for food safety and sustainability.

Development of an Analytical Method for Detection of Anesthetics and Sedatives in Fish.

Anesthetics and sedatives are frequently used to prevent abrasions caused by stress and to facilitate fish management. However, drug residues may persist and cause changes in fish conditions and induce side effects. In addition, drugs that are not permitted for use in edible fish are sometimes potentially used in fish. The drugs can also be found in wastewater and are likely to be detected in fish. The purpose of this study was to establish a quantitative analytical method for 10 anesthetic and sedative (azaperone, chlorpromazine, diazepam, estazolam, haloperidol, nitrazepam, nordiazepam, oxazepam, perphenazine, and temazepam) residues in fish sold in Korean markets. Shrimp, flounder, and eel samples were selected as matrices. Acetonitrile (ACN) containing 0.1% formic acid was selected as an extraction solvent for shrimp and 100% ACN for flounder and eel. The QuEChERS method with C18 and primary secondary amine (PSA) was used as the extraction procedure, and the analysis was performed by liquid chromatography-tandem mass spectrometry (LC-MS/MS). Limit of quantitation, recovery, accuracy, and precision were validated, and satisfactory results were obtained for the drugs. All results applied to the real samples were negative. An optimal validation method was studied. Since the results for all samples were negative, it is considered that additional studies are needed by increasing the number of drugs. The most effective QuEChERS pretreatment method and conditions of LC-MS/MS for the analysis of anesthetics and sedatives in fish were established.

Identification of Micro-organisms (Parasites and Bacteria) which are Potential as Pathogenic Agent in Glass Eel of Anguilla spp. at the Eel Capture Location, Sukabumi, West Java

Eel (Anguilla sp.) is one of the important commercial fish in some countries particularly in East Asian countries such as Japan, South Korea, China, and Taiwan. The need of eel fry or frequently called as glass eel still relies on the natural capture. The issue of natural captured fish is the high level of bacterial infections and diseases. The dependence of glass eel from the nature provides an indication of infections of parasites and bacteria in glass eel. The existence of parasites and bacteria as microorganisms which are potential as pathogenic agents in the cycle of eel culture can be a serious obstacle, so that the glass eel handling needs a particular attention since the capturing proses from the nature. Therefore, identification of parasites and bacteria in the capture location of glass eel was necessarily conducted in Pelabuhan Ratu Bay, Sukabumi, West Java. The glass eel sampling was conducted in May-June 2019, in 3 locations of estuary with the highest capture yield namely Cimandiri River, Cikaso River and Cibuni River. The number of samples taken were 30 eels at each river location with 2 replicates, so that the total eel samples which were taken were 180 eels. Identification of parasites was conducted by examination of ectoparasite and endoparasite and dentification of bacteria was conducted by conventional method (biochemical method). Based on the result of identification, there was no parasite found in the glass eel samples, while bacteria found as many as 12 species and 3 dominant species namely Listeria sp. found in 40 eel samples with prevalence of 22.2%, Aeromonas hydrophila found in 28 eel samples with prevalence of 15.6%, and Staphylococcus spp. found in 22 eel samples with prevalence of 12.2%.Keyword : Micro-organism, Pathogen, Glass Eel, Anguilla spp.

Chinese eel products in EU markets imply the effectiveness of trade regulations but expose fraudulent labelling

The stock of the European eel (Anguilla anguilla) is in a multi-decadal decline. Therefore, trade in European eel is now restricted by EU law and the listing in CITES Appendix II. EU law prohibits the trade of European eel across the EU’s outer border and CITES regulates the global trade elsewhere. In November and December 2019, we purchased 108 eel products in 21 cities in five major eel importing countries in Europe (Germany, Belgium, Netherlands, Great Britain, France) and three online shops. All were imported from China and 73 samples were genetically identified as American eel (A. rostrata), 33 as Japanese eel (A. japonica), and a single sample each as European eel and Indian shortfin eel (A. bicolor pacifica). The one European eel sample violated the EU trade ban and CITES trade regulations. However, 28.7 % of the product labels violated EU Regulation (EU) No 1169/2011 on the provision of food information to consumers (FIC). Our results imply that Chinese exporters sell their European eel products outside the EU market and therefore avoid violating EU law. However, fraudulent labelling point at inadequate existing EU labelling requirements for prepared and preserved products and ongoing molecular genetic control of eel commodities entering the EU from China. Data availability statementThe data that support the findings of this study are openly available in Genbank at www.ncbi.nlm.nih.gov/genbank/ under the consecutive accession numbers MN973673-MN973780. Basic data on unagi kabayaki products are listed in Table 1, details can be obtained from the corresponding author on request.

Characteristics of productive broodstock based on body length and gonad histology of eel (Monopterus albus) in Semarang

The purpose of this study is to describe the characteristics of productive broodstock based on body length and histological gonad description of eels in Semarang. Samples of catched eels in various sizes, each measured its length and weight, determined its sex, recorded morphologically and made microtechnic histological description of gonads. Based on description of gonad hyostology, the eels body length is 28-32 cm for female and consists of egg cells set, which are in 32-36 cm is intersex, the egg cell is decreased sperm cells begin to develop and those are in 37-45 cm. Based on IKG eels obtained in four subdistricts, the egg size cannot be measured because they are in 1.7 to 2.3 mm. Based on gonads microscopic view and visual body length at TKG II, TKG III and IV consisted of eggs and sperm. While eels IKG obtained the most are 25 eels in IKG class 2.829943-3.829943. Conclusion of this research showed that productive female eels have an average body length of 26 - 34 cm with a morphology characteristic sharp head, greenish skin color on the back and yellowish white on the abdomen. Productive male eels have a body length in 54 - 60 cm with a morphological characteristic is greenish brown back, brownish yellow belly, large head and nape size, slightly short tail and blunt ends.

Proximate composition, fatty acid profile and total amino acid contents in samples of the European eel (Anguilla anguilla) of different weights

European eel of different sizes were caught in the River Ulla (Galicia, NW Spain) during winter. The proximate composition differed significantly between fish of different sizes. Discriminant canonical analysis was used to identify the components that enable specimens of different weights to be distinguished. Fat content was the most variable parameter and was directly related to the weight of the fish. The fatty acids that greater increased their content during the growth of the eel were linolenic acid, arachidonic acid, eicosatrienoic acid, and tricosanoic acid. The lipid profiles and quality indices of the eels indicated their high nutritional quality. The threonine, lysine, serine, arginine, alanine and proline contents were highest in the smaller eels. The European eel is a source of high-quality protein with a well-balanced amino acid profile. Moreover, the ratio of essential to non-essential amino acids was highest in the larger eels.