Euthynnus Alletteratus Research Articles

Assessing the stock status of Euthynnus alletteratus (Rafinesque 1810) exploited by tuna purse seiners in the Northeast Atlantic Ocean: implications of using the length-based Integrated Mixed Effect model

ABSTRACT Euthynnus alletteratus, a crucial commercial resource for West African states in the Northeast Atlantic Ocean (ATNE), is of high research priority in the Atlantic Ocean, but its stock assessment is limited. This study aimed to explore the implications of integrating length, catch and abundance indices on the status of ATNE stock using the LIME model. We innovatively developed time series of abundance indices using tuna purse seine catches and efforts obtained from separate ICCAT datasets, alongside length-frequencies. The scenarios (S) S1 (length-only), S2 (length + catch + abundance), S3 (length + catch), and S4 (length + abundance) were considered. We observed that S1–S3 did not converge in LIME, except for S4. The stock's spawning potential ratio and mean length were below the target (SPR< 40%) and 95% maturity length (M95), respectively. By implication, the lack of convergence in S1–S3 portrayed data conflicts, which were mitigated by the abundance index in S4. A mean length above M95 is recommended when evaluating the stock using the length-only option in LIME. The stock was unsustainable, requiring management measures. Integrating the abundance index with length improved the performance of LIME for the stock, which estimate could be replicated for other species' assessments.

Microscopic study of the gonads in males and females of Euthynnus alletteratus (Rafinesque, 1810) and Sarda sarda (Bloch, 1793), two species of coastal affinity from the gulf of Guinea, Côte d’Ivoire

Microscopic study of the gonads in males and females of Euthynnus alletteratus (Rafinesque, 1810) and Sarda sarda (Bloch, 1793), two species of coastal affinity from the gulf of Guinea, Côte d’Ivoire

The gills and skin microbiota of five pelagic fish species from the Atlantic Ocean.

The gills and skin microbiota and microbiome of wild fish remain far more under-investigated compared to that of farmed fish species, despite that these animal-microbe interactions hold the same ecophysiological roles in both cases. In this study, the gills and skin bacterial microbiota profiles and their presumptive bacterial metabolisms were investigated in five open-sea fishes: bullet tuna (Auxis sp.), common dolphinfish (Coryphaena hippurus), Atlantic little tunny (Euthynnus alletteratus), Atlantic bonito (Sarda sarda) and Atlantic white marlin (Kajikia albida). Gills and skin tissues were collected from two to three individuals per species, from specimens caught by recreational trolling during summer of 2019, and their bacterial 16S rRNA gene diversity was analysed by high-throughput sequencing. The gills bacterial communities among the five species were clearly different but not the skin bacterial microbiota. The dominant operational taxonomic units belonged to the Moraxellaceae, Pseudomonadaceae, Rhodobacteraceae, Staphylococcaceae and Vibrionaceae families. Despite the differences in taxonomic composition, the presumptive bacterialmetabolisms between the gills and skin of the five fishes investigated here were ≥ 94% similarand were dominated by basic metabolism, most likely reflecting the continuous exposure of these tissues in the surrounding seawater.

Total mercury in three small tunas from southeastern Brazil: Stable isotope relations and human risk assessment

Mercury (Hg) bioaccumulation can be highly variable in marine species. Its concentration is influenced by several physico-chemical and biotic processes, including size, age, diet composition and foraging habitats. Herein, we addressed total mercury (THg) concentrations in three small tuna species in Brazil: the frigate tuna Auxis thazard, the little tunny Euthynnus alletteratus and the skipjack tuna Katsuwonus pelamis. Samples were collected from commercial landings in the SE Brazilian coast from 2017 to 2019. The influence of trophic ecology and habitat preference on Hg accumulation was assessed through stable isotope [carbon (δ13C) and nitrogen (δ15N)] measurements. Additionally, the human health risk regarding the species consumption was assessed by the estimated weekly intake (EWI) and the provisional tolerable weekly intake (PTWI) for total consumers, adult men and adult women. Variables such as size and age were positively correlated to Hg, due to the bioaccumulation process. Trophic position appears to positively influence the mercury concentrations for A. thazard and K. pelamis, since relationship between δ15N and THg was significant. For E. alletteratus, the lack of relationship suggests that δ15N values do not vary much among adult fish (> 300 mm). Muscle THg concentrations in the three species did not exceed the established tolerable limit for mercury by Brazilian and international organs, as indicated by the %PTWI. This finding suggests that the consumption of those species caught off southeast Brazil at the considered amounts does not present a risk for healthy adults.

Lobatozoum woodi n. sp. (Digenea: Didymozoidae) parasitizing Euthynnus alletteratus (Scombriformes: Scombridae) in the coast of the State of Rio de Janeiro, Brazil.

The aim of this study was to describe a new species of Didymozoidae (Trematoda) found in the mesentery of Euthynnus alletteratus (Rafinesque) off Cabo Frio, in the coastal area of the state of Rio de Janeiro, Brazil. Thirty specimens of E. alletteratus were obtained between August 2023 and June 2024, directly from traders who sell fresh fish in markets. The parasites were fixed in AFA (93% ethanol 70%, 5% formaldehyde and 2% glacial acetic acid) with or without compression, stained with Langeron's hydrochloric carmine, dehydrated in an alcohol series, clarified in clove oil and mounted in Canada balsam as permanent slides. The new species was assigned to the genus Lobatozoum Ishii, 1935, mainly by the presence of lobes in the posterior region of the body and by the arrangement of the testes, ovary and vitellaria. Lobatozoum woodi n. sp. differs from all congeneric species mainly by presenting three testicular tubules, by the size of pharynx, larger than the oral sucker, and by the absence of digestive glands cells in esophagus and initial portion of caeca. The finding of a new species of Lobatozoum represents the eleventh valid species in the genus.

Interspecific, ontogenetic and temporal variations in stable isotopes of small tuna species in the northeast Atlantic Ocean

ABSTRACT In order to study the trophic level of small tuna species and their contribution to the carbon flow in pelagic food webs, an analysis of carbon and nitrogen stable isotopes was carried out. The investigation was focused on four small tuna species (Auxis rochei, Auxis thazard, Euthynnus alletteratus and Sarda sarda) commonly harvested in the northeast Atlantic Ocean. The isotope analysis showed how the results for S. sarda are different from the rest of the species analysed, with a higher trophic level, similar to other major tuna species. The greatest niche overlap in δ13C and δ15N occurs among A. rochei, A. thazard and E. alletteratus. Auxis rochei and E. alletteratus showed a size-dependent variability in δ15N, and in δ13C for S. sarda. The small tuna S. sarda exhibits the highest migration rates among various geographical areas in comparison to other small pelagic tunas, and the seasonal variability of isotope values in the area studied can be attributed to the incorporation of larger individuals with a higher lipid content. The results of this work provide new information on the ecological role played by small tuna in food webs, which is more complex and varied than currently thought. This knowledge is essential for a more effective management of fisheries.

Immunohistochemical Evaluation of Histamine Levels and Hygienic Aspect of Little Tunny (Euthynnus alletteratus) Musculature at Different Environment Time and Temperature

ABSTRACT We investigated the effect of storage time and temperature on muscular histamine (HIS) contents in little tunny (LT). Fifty LT were preserved at various temperatures (0- 21°C). We collected muscles from several areas at 0-, 6-, 12-, 18-, and 24 h post-fishing for further examination. Throughout storage time and temperature, there was a significant increase in fish deterioration, HIS levels, and HFB count in abdominal > tail > dorsal muscle. Vitek2 gave 99% confidence identity of the highly histaminergic strains Lelliottia amnigena-1 and Acinetobacter haemolyticus. There was a positive correlation between HIS levels, HFB counts, and microscopic lesion scores during storage.

Bioaccumulation of heavy metals in water and organs of Tilapia brevimanus and Euthynnus alletteratus from a coaster water in southwestern Nigeria

The bioaccumulation of some heavy metals in coaster waters directly affects the ecosystem and human beings. Thus, the objectives of this study are to evaluate the interaction between fish and coastal water and assess the long-term implications of human consumption of some major organs obtained from Tilapia brevimanus and Euthynnus alletteratus. The study determined the concentrations of arsenic (As), cadmium (Cd), chromium (Cr), and lead (Pb) in twenty coaster water samples collected from two points and in the muscle, gills, and intestine of ten pieces of Tilapia brevimanus and ten pieces of Euthynnus alletteratus using a Perkin Elmer Model 306 Atomic Absorption Spectrometer. Furthermore, the accumulation of these metals and the assessment of the long-term implications of human consumption of the designated organs of the two species types were performed. The statistical significance level of the obtained results was determined using the T-test analysis tool, which revealed that the distribution of the metals varies in different organs of the fish species. The levels of pollutants were higher in Tilapia brevimanus organs than in Euthynnus alletteratus. The contents of As, Cd, Cr, and Pb in the gills were higher than those in the muscle. Also, the metal pollution index in the organs followed the order of intestine > gills > muscle for both Tilapia brevimanus and Euthynnus alletteratus, posing serious health risks.

Movement patterns and size distribution of little tunny (Euthynnus alletteratus) in the Eastern Central Atlantic Ocean: Insights from conventional tag release-recapture data

This study investigates the movements, patterns, and size distribution of little tunny (Euthynnus alletteratus) in the Eastern Central Atlantic Ocean. Data were collected as part of the ICCAT Atlantic Ocean Tuna Tagging Programme (AOTTP) through conventional tag release-recapture experiments. The study analyzed data from 7870 tagged fish, of which 452 were recaptured between 2016 and 2020. The results indicated that little tunny could travel long distances, with some fish covering up to 600 Nm between Mauritania and Côte d’Ivoire. The movement patterns of tagged fish varied, and there appeared to be some exchange of fish between Senegal-Mauritania and the Gulf of Guinea through the Côte d’Ivoire Exclusive Economic Zone (EEZ). The recapture rate was the highest within the first month after release, with half of the tagged fish recaptured within this period, then approximately 17 % and 11.5 % of tagged fish were recaptured within 60 and 90 days, respectively. The size distribution of tagged and recaptured little tunny varied by area with statistically significant differences between Côte d’Ivoire – Gulf of Guinea and those from Mauritania to Liberia. The recaptured fish were larger than the tagged fish in all areas studied, suggesting a significant growth of individuals (4.2 cm per quarter). In conclusion, this study highlights the extensive movements and migration patterns of little tunny in the Eastern Central Atlantic Ocean. These findings suggest that factors such as Anchored Fish Aggregating Devices (AFAD) may influence the mobility of fish in certain areas and that the size distribution varies significantly between different regions.

Isolation and Identification of Pathogenic Bacteria from Domestic Retail Fish Market at Zliten City, Libya

The microbial load of both fish and fish products has been a cause of concern to consumers, and the industry itself. The present study was focused on isolation and identification of pathogenic bacteria found in selected species of fish taken at the city market of Zliten, Libya. Thirty-five fish samples were analyzed; the bacterial counts and identification of potentially isolated-bacteria were carried out by using standard bacteriological procedures. The sensitivity test was determined by the disc-diffusion method. The results have shown the highest bacteria count was reported for the gills of Euthynnus alletteratus (7.61´106 cfu/mL) compared to Sarpa salpa and Scomber japonicas (1.82´106 cfu/mL and 4.45´106 cfu/mL) respectively. The whole fish of Euthynnus alletteratus had also the highest bacterial count (7.589´106 cfu/mL) followed by the intestine of Sarpa salpa (6.07´105 cfu/mL) and Scomber japonicas (2.22´106 cfu/mL). Bacteria identified from this study include Staphylococcus spp. and Staphylococcus aureus, Bacillus, Pseudomonas Vibrio spp. The higher levels of Staphylococcus spp. was observed for Euthynnus alletteratus and Scomber japonicas (P&lt;0.0043) compared to Euthynnus alletteratus. No Significant differences were observed in the microbial load between the domestic and imported fish. However, the ratio of the isolated Bacillus spp. was higher (P&lt;0.02) in imported fish (Scomber japonicas) compared to domestic fish. Isolated bacteria from fish samples were tested for resistance against thirteen antibiotics (Penicillin, Vancomycin, Clindamycin, Cefoxitin, Oxacillin, Linezolid, Cephalexin, Rifampicin, Streptomycin, Tetracycline, Erythromycin, Gentamicin and Ampicillin). Among the isolated bacteria, the Staphylococcus spp. was resisted to different antibiotics whereas one hundred present of (Cephalexin and Rifampicin). The Staphylococcus aureus was resistance to Tetracycline and Vancomycin. Bacillus spp. was resistance to Vancomycin whereas the Pseudomonas was resistance to Rifampicin. Even though, the isolated bacteria were sensitive to different antibiotic.

Organotin contamination in seafood from the Yucatán Peninsula, Mexico: Is there a potential risk for the health of consumers?

Since seafood is considered an important source of organotin compounds (OTCs), the present study assessed the potential risk to human health of ingesting butyltins (BTs) and phenyltins (PhTs) along with this type of food. Seafood samples were collected at five fishing sites in the Yucatán Peninsula (Mexico) during February and March 2018. In general, organotins were detected in all samples, suggesting a widespread occurrence of these compounds in the investigated region. The average concentration of total organotins in the muscle of demersal fish (Lutjanus synagris, Lutjanus campechanus, Calamus pennatula, Haemulon plumierii, Rhomboplites aurorubens), pelagic fish (Euthynnus alletteratus, and Opisthonema oglinum), gastropods (Melongena bispinosa and Strombus pugilis), oyster (Crassostrea virginica) and shrimp (Penaeus duorarum) was 146.7 ± 76.2, 93.1 ± 92.6, 61.0 ± 53.0, 76.7 ± 2.6, and 28.8 ± 2.7 ng Sn g−1 dry weight, respectively. Overall, MPhT among PhTs was the dominant compound in fish, while TBT among BTs was the dominant compound in shellfish. Regarding the toxic OTCs, TBT followed by DBT were the predominant compounds in all seafood species, while TPhT was below the quantification limit in most samples. The estimated daily intake values were lower than the tolerable daily intake (TDI) for the sum of organotins established by the European Food Safety Authority (EFSA). Furthermore, the hazard quotients (HQ) and hazard indices (HI) values were all lower than 1, suggesting that daily exposure to these levels of organotins is unlikely to cause any harm to the human health of seafood consumers at the Yucatán Peninsula. Thus, consumers may not be at risk through the inclusion of these investigated seafood species in their normal diet. However, due to the increasing coastal urbanization, maritime activities, and the likely illegal use of tin-based paints in Mexico, additional monitoring is needed to assess organotin levels in other regions along the Mexican coastal zone and using other seafood species.

NEW GEOGRAPHIC OCCURRENCE: DIGENEA Lobatozoum multisacculatum (DIDYMOZOIDAE) ON LITTLE TUNNY, Euthynnus alletteratus (SCOMBRIDAE)

Considering that the quantitative and ecological studies related to parasites of scombrids are scarce in Brazil and that in Rio Grande do Norte (RN) there are no records, specially of Trematoda in Euthynnus alletteratus, this work reports the presence of the digenean Lobatozoum multisacculatum as well as their ecological parasitic indexes in this host species.&#x0D; Keywords: geographic distribution, Didymozoids, Trematoda in scombrids, little tunny.

The Gyaros island marine reserve: A biodiversity hotspot in the eastern Mediterranean Sea.

Since July 2019, Gyaros island in the central Aegean Sea, enjoys the status of a partial Marine Protected Area (MPA), allowing for exploitation by small-scale fishers following specific spatio-temporal restrictions. The need for assessing the effectiveness of the MPA in the future, led MAVA Foundation to fund a knowledge survey project aiming to serve as a baseline for future reference. A series of experimental fishing surveys took place with static nets, the outcomes of which are presented herein. From June 2018 to September 2020, a series of 8 fishing excursions with a total of 40 experimental fishing sets with bottom static nets were realized in 5 set locations around Gyaros island, inside the MPA protection zone. A total of 75 species were identified; the most abundant species, in terms of biomass, being: parrotfish-Sparisoma cretense, red scorpionfish-Scorpaena scrofa, common spiny lobster-Palinurus elephas, red porgy-Pagrus pagrus, little tunny–-Euthynnus alletteratus, Mediterranean moray-Muraena helena, lesser spotted dogfish -Scyliorhinus canicula, forkbeard-Phycis phycis, surmullet-Mullus surmuletus, common cuttlefish-Sepia officinalis and common Pandora-Pagellus erythrinus. A comparison with similar data in adjacent areas outside the MPA allowed for assessing the effectiveness of the MPA based on four indicators: species diversity index, species relative biomass index, key predator species abundance, and alien fish abundance. Based solely on the experimental fishing trials, the MPA seems to be functioning, since both species diversity and abundance were higher within the protected area. However, its performance may still not be considered as optimal, as this is indicated by the large proportion of undersized key predators (e.g. groupers), although more abundant and larger than the ones residing outside the MPA.

Trophic relationships revealed by dart tags found in the stomachs of large pelagic fishes in the Atlantic Ocean

Plastic dart tags are the main type of tag used in all major fish tagging projects but their potential for studying trophic relationships has never been addressed. The occurrence of dart tags in the stomach contents of large pelagic fishes and direct observations onboard tagging vessels reveal novel information on predation and cannibalism by tropical tunas in the Atlantic Ocean. The observations were all made during the Atlantic Ocean Tropical Tuna Tagging Programme (AOTTP), which targeted bigeye tuna (Thunnus obesus), yellowfin tuna (Thunnus albacares), skipjack tuna (Katsuwomis pelamis), wahoo (Acanthocybium solandri), and little tunny (Euthynnus alletteratus). During the programme (so far) 5 conventionally tagged fish have been reported in stomach contents from captures made in Brazil, São Tome and Principe, and Ivory Coast: including one yellowfin tuna and two skipjack tunas in a yellowfin tuna, one yellowfin tuna in a blue marlin (Makaira nigricans), and one yellowfin tuna in a non-identified shark. We use these observations to illustrate the potential role that dart tags could play in helping describe trophic interactions among marine pelagic fish species.

Thymus vulgaris L. Essential Oil: Effect on Fatty Acids and Proteins Oxidation of Little Tuna (Euthynnus alletteratus) Minced during Refrigerated Storage

People are uncomfortable having their food chemically treated to boost its shelf life. Thus, Tunisian Thymus vulgaris Essential Oil (TVEO) were investigated in parallel with its capacity to limit fatty acids and proteins oxidation in tuna (Euthynnus alletteratus) minced during refrigeration storage (4°C). Our results revealed that for tuna preservation, the measured concentrations of PV, TBARS and TVB-N during different storage periods showed a good efficiency of this Essential Oil (EO) (3%) in limiting lipids and proteins oxidation of tuna flesh. Moreover, we observed increase in all batches which was significantly different (P&lt; 0.05) with lots treated with TVEO were the most conserved comparing to the BHT. Overall outcomes suggest that TVEO use for tuna conservation could represent a promising strategy to improve the qualitative characteristics as well as the safety of seafood.

Age, growth, and maturity of little tunny, Euthynnus alletteratus (Rafinesque, 1810) in southeastern Brazil

This is the first attempt to assess life parameters of little tunny Euthynnus alletteratus in the southwestern Atlantic. Fin spines, liver, and gonad information from 345 fishes (330-780 mm fork length) sampled from artisanal landings between March 2018, and February 2019 were used to analyze age, growth, and sexual maturity. Age was estimated by counting and measuring increments in sectioned spines, and the von Bertalanffy growth function was used to fit length-at-age data. There was no significant difference between male and female size distributions. Gonadosomatic index peaked from November to February in both sexes, associated with the South Atlantic Central Water (SACW) upwelling in temperatures between 15-18°C. Reproduction in cold waters has never been reported before and is possibly related to a richer environment for feeding and growth of larvae. The coefficient of variation among successive readings was 9.2%. The oldest fish was 5 years, and one annual increment for 2 and 3-year-old fish was observed to form associated with SACW. Little tunny growing in southeastern Brazil shows a higher growth rate and smaller asymptotic length when compared to most stocks in Mediterranean waters. Growth was not significantly affected by sex, and the von Bertalanffy growth parameters for all fish were L∞ = 791.9 mm, k = 0.42, and t0 = -0.97 yr-1. Length at first maturity is attained by 1-year-old fish of either sex (423-492 mm), suggesting that a small proportion (8%) of juveniles was recorded from fishery landings.

Neonematobothrium annakohnae n. sp. (Digenea: Didymozoidae) parasitizing Euthynnus alletteratus (Perciformes: Scombridae) in the Southwest Atlantic Ocean.

Describe a new species of didymozoid digenean Neonematobothrium Yamaguti, 1965 from the operculum of the scombrid fish, Euthynnus alletteratus (Rafinesque, 1810), in the Southwest Atlantic Ocean off Brazil. Thirty-four specimens of E. alletteratus were collected in the coastal zone of the state of Rio de Janeiro and obtained from local fishermen between 2006 and 2018 in the municipal market of São Pedro in Niterói, Brazil. The parasites were fixed in AFA (93% ethanol 70%, 5% formaldehyde, 2% glacial acetic acid) without pressure, stained with Langeron alcoholic acid carmine, dehydrated in an alcohol series, cleared in beachwood creosote or clove oil and mounted in Canada balsam as permanent slides. Neonematobothrium annakohnae n. sp. is a member of the genus based on a combination of the following characteristics: body free, uncapsulated; body long and dorsoventrally flattened; esophagus surrounded by gland cells; ovary and vitellarium single, long, narrow and unbranched in the anterior and posterior halves of the body, respectively; uterus with three loops; and site of infection in subcutaneous tissue of scombrid fish. The new species differs from the two recognized species of the genus mainly by the size of the body, which is much larger, the shape of the genital pore, which is differentiated in a structure similar to a small sucker and by esophagus without diverticula. Neonematobothrium annakohnae n. sp. parasite of E. alletteratus from the Southwest Atlantic Ocean, described herein, represents the third species of Didymozoidae belonging to the genus Neonematobothrium. The two known species Neonematobothrium kawakawa Yamaguti, 1965 and Neonematobothrium dorsale Yamaguti, 1970 were described from fish belonging to the same genus of the host from Pacific Ocean. The diagnosis of the genus is enlarged to "esophagus with or without diverticula", to fill the characteristics presented by the new species. The description of N. annakohnae n. sp. demonstrates the need to expand the studies of these interesting and intriguing group of parasites, due to the fact that number of known didymozoids taxa in the Atlantic Ocean is far from representing the real situation.

Interannual trophic behaviour of a pelagic fish predator in the western Mediterranean Sea

The exploitation of forage fish species can modify the functioning of marine ecosystems potentially impacting the population status of predators. This may be the case for the western Mediterranean Sea, where a reduction in the biomass of two key pelagic forage fish (European anchovy Engraulis encrasicolus and European sardine Sardina pilchardus) could produce a change in the diet composition of their main predators, which would consume alternative preys or change the size of the prey consumed. Here, we aimed to investigate the potential effect of biomass reduction of sardine and anchovy in the western Mediterranean Sea on the trophic preferences of the little tunny (Euthynnus alletteratus), a medium-sized predator that present a high consumption of these forage fish. We compared its interannual trophic ecology by combining the analysis of stomach contents and stable isotopes. Specifically, we examined if the diet of little tunny changed in its main trophic habits (diet composition, prey size, and trophic niche) during a 6-year period. We found that small pelagic fish, especially clupeiformes, were the most important prey group for the little tunny during the study period. However, we found changes in the body size of anchovy and the relative importance of sardine in recent years, probably reflecting the reported reduction in the biomass and body size of these two forage fish in the study area. In addition to these changes, we found an increase in some demersal and benthopelagic species in the diet of little tunny, which could act as an alternative diet resource.

Hg, As, Cr, Sn, Ni, and Se concentrations in the muscle of little tunny (Euthynnus alletteratus) from the western Algerian stock.

Muscle-metal (As, Se, Hg, Sn, Cr, Ni) levels were measured in little tunny (Euthynnus alletteratus) from the western Algerian stock. Relationships between metal levels in the muscle tissues and fish fork length and total weight were examined. The accumulation of metals in muscle tissues varied in the following ascending order: Ni, Cr, Sn, Hg, Se, and As. The range of metal concentrations (mg kg-1/wet weight) were 1.2561-3.8562 (As), 0.6897-3.4123 (Se), 0.3852-1.4235 (Hg), 0.1569-0.6512 (Sn), 0.1254-0.4002 (Cr), and 0.0719-0.3122 (Ni). Significant variations (t > 1.96, p < 0.05) between metal concentrations were observed in muscle tissues of E. alletteratus. The concentrations of all metals investigated increase as the fish increased in size and total weight. Furthermore, the results of exponential regressions showed significant positive relationships (p < 0.05) between metal levels and fish size and weight. Average levels of heavy metals in muscle tissues of E. alletteratus were lower than permissible limits for fish consumption prescribed by FAO/WHO, EC, ASTDR, and USFDA.

Carboxylesterase activities as potential biomarkers of pollution in marine pelagic predators

Assessment of chemical exposures in the marine environment is frequently undertaken in sedentary organisms inhabiting coastal environments. However, predatory pelagic fish should be considered sentinel species, as they play an important role in the sustainability of the ecosystems due to their high position in trophic webs. In this study, carboxylesterase (CE) activities were analysed in four predatory tuna species of commercial interest along the western Mediterranean Sea: little tunny(Euthynnus alletteratus), Atlantic bonito (Sarda sarda), bullet tuna(Auxis rochei) and albacore tuna(Thunnus alalunga). CEs are potential biomarkers of chemical exposure, as they are an important family of enzymes involved in the metabolism of xenobiotic and endogenous compounds. CE measures were taken from the liver of these tuna species using five commercial substrates: 4-nitrophenyl acetate (4NPA), 4-nitrophenyl butyrate (4NPB), 1-naphthyl acetate (1NA), 1-naphthyl butyrate (1NB), and 2-naphthyl acetate (2NA). Butyrate substrates (1NB and 4NPB) yielded the highest hydrolysis rates, and were thus the best substrates for these measures. CE activities differed between species. The larger differences were attained with 1NB-CE, with higher activities seen in bullet tuna, followed by little tunny, Atlantic bonito and albacore tuna. Individual size was identified as one of the main factors modulating CE activities, while there was no evidence for a role for trophic level (measured as δ15N). Using little tunny as sentinel, no geographical differences but inter-annual variation in CE activity was observed. The kinetic parameters and in vitro exposure to the pesticide dichlorvos provided complementary information on the sensitivity of tuna CEs to this model pesticide. Our results propose that the little tunny could be considered a potential bioindicator species in the pelagic realm.