Search

Atlantic bluefin tuna (ABFT; Thunnus thynnus) is a highly migratory species. To investigate the migrations and vertical behaviours of ABFT migrating to Nordic waters, we deployed pop-up satellite archival transmitting tags on 25 ABFT off Norway (curved fork length: 228–292 cm). We obtained 16 full-year migrations, which differed between individuals, and physically recovered 13 tags, which provided 4699 days of archival depth and temperature data. ABFT occupied waters from the Arctic Circle to as far south as Cabo Verde, Africa, and occupied depths down to 1190 m and temperatures from 0.5 to 27.8°C. During their annual migrations, ABFT spent, on average, 68 days in Norwegian waters, 65 days in the Newfoundland Basin, 35 days around the Canary Islands and 33 days in the West European Basin. Most ABFT entered the Mediterranean Sea with a mean entry date of 13 May and visited known spawning grounds, staying, on average, 44 days. All ABFT with full-year deployments returned to Norwegian waters. ABFT displayed high site-fidelity and dynamic vertical diving behaviours that varied between hotspots and seasons. These spatiotemporal data provide important ecological knowledge for sustainable management and the conservation of the recently recovered eastern ABFT stock. [ABSTRACT FROM AUTHOR]

Aim: Predicting spatial and temporal changes in species distributions is difficult for highly mobile species, making effective management challenging. We aim to understand the seasonal variability in habitat suitability for Atlantic bluefin tuna (Thunnus thynnus; ABFT) by using tracking data to create species distribution models. Location: North‐east Atlantic Ocean. Methods: Forty‐nine ABFT were tagged with pop‐up archival satellite tags along the west coast of Ireland during successive autumns from 2016 to 2021. Four thousand two hundred and sixteen daily locations were used to build a habitat model to describe ABFT environmental preferences and habitat suitability. For each location, 100 'pseudoabsence' locations were simulated using correlated random walks. Results: Tags had a mean retention rate of 237 ± 107 days, resulting in 11,602 cumulative days at liberty, and a mean daily distance travelled of 51 ± 143 km. ABFT showed two primary migration routes from Ireland, travelling to the Bay of Biscay or across the Mid‐Atlantic ridge in the winter. However, in 2019 six individuals travelled northwards towards Iceland, likely in response to a marine heatwave. Eight ABFT entered the Mediterranean in May/June for putative spawning, with six returning to Irish waters a year later. Five environmental covariates best described ABFT habitat, with habitat suitability highest at sea surface temperatures (SST) of 15–18°C, a mixed layer depth between ~200 and 300 m, high relief bathymetric features (i.e. shelf breaks and seamounts) and frontal regions as revealed by non‐linear preferences of eddy kinetic energy and SST standard deviation. Main Conclusions: In the last decade, ABFT have been re‐establishing historic foraging grounds in higher latitudes, for example, Irish and Nordic waters. Our model shows the extent of suitable habitat in these regions and how recent ocean warming may have contributed to northern expansions. Understanding the drivers behind these reappearances is fundamental to successful future management. Achoimre: Aidhm: Tá sé deacair athraithe i ndáileadh ama agus spásdháileadh speiceas atá an‐soghluaiste a thuar, rud a chiallaíonn go bhfuil sé dúshlánach bainistiú éifeachtach a dhéanamh. Tá muid ag iarraidh inathraitheacht shéasúrach in oiriúnacht ghnáthóg an Tuinnín Gorm Atlantach (Thunnus thynnus; TGA) a thuiscint tríd sonraí rianaithe a úsáid chun samhail dháileadh speiceas a chruthú. Suíomh: Oirthuaisceart an Atlantaigh. Modh: Rinneadh clibeadh ar 49 TGA le clibeanna cartlainne a thagann go barr uisce ar chósta iarthar na hÉireann le linn ceithre fhómhair i ndiaidh a chéile ó 2016–2021. Úsáideadh 4216 suíomhanna laethúil chun samhail ghnáthóg a chruthú a rinne cur síos ar roghanna timpeallachta agus oiriúnacht ghnáthóg an TGA. I gcomhair gach suíomh, ionsamhlaíodh 100 suíomhanna bréag‐neamhláithreacht ag úsáid siúlóidí randamacha comhghaolaithe. Torthaí: Bhí meán ráta coinneála de 237 ± 107 lá ag na clibeanna, rud a thug 11,602 lá taifeadta i ndiaidh a chéile agus meán fhad laethúil taistealta de 51 ± 143 km dá bharr. Léirigh TGA dhá phríomhbhealaí imirce ó hÉirinn, ag taisteal go Bá na Bioscáine nó thar Droim an Atlantaigh Láir i rith an gheimhridh. Ach i 2019 thaisteal sé iasc ó thuaidh i dtreo an Íoslainn, is dócha mar gheall ar thonn teasa mara. Chuaigh ocht TGA isteach sa Mheánmhuir i rith mí Bealtaine/mí an Mheitheamh chun uibheacha a sceitheadh de réir dealraimh. Tháinig sé dóibh ar ais go huiscí na hÉireann an bhliain dar gcionn. Déanann cúig athróg timpeallachta an cur síos is fearr ar ghnáthóg an TGA, tá oiriúnacht ghnáthóg is airde ag teocht barr uisce (TBA) de 15–18°C, nuair atá doimhneacht an chisil mheasctha idir ~200 agus 300 m, ag gnéithe bataiméadrach ard‐rilíf (i.e. scoilteanna scairbhe agus tuláin grinnill), agus ag réigiúin frontacha léirithe ag roghanna neamh‐líneacha fuinneamh cinéatach guairneánach agus diall caighdeánach TBA. Príomhchonclúidí: Le leathscór bliain anuas tá TGA tar éis réigiúin sealgaireachta stairiúil a athbhunú in áiteanna le hard‐domhanleithead, ar nós uiscí na hÉireann agus uiscí Nordacha. Taispeánann ár samhail achar an ghnáthóg oiriúnach sna réigiúin seo agus an bhaint féideartha a bhí ag téámh aigéanach le gairid ar leathadh ó thuaidh. Tá sé buntábhachtach na cúiseanna don athfhilleadh seo a thuiscint i gcomhair bainistiú rathúil amach anseo. [ABSTRACT FROM AUTHOR]

Tuna is an excellent food product, relatively low in calories, that is recommended for a balanced diet. The continuously increasing demand, especially for bluefin-tuna-based food preparations, and its relatively high market price make adulteration by intentionally mixing with other lower-priced tunas more prospective. The development of rapid methods to detect tuna adulteration is a great challenge in food analytical science. We have thus developed a simple, fast, and low-cost molecular rapid test for the visual detection of tuna adulteration. It is the first sensor developed for tuna authenticity testing. The three species studied were Thunnus thynnus (BFT), Thunnus albacares, and Katsuwonus pelamis. DNA was isolated from fresh and heat-treated cooked fish samples followed by PCR. The PCR products were hybridized (10 min) to specific probes and applied to the rapid sensing device. The signal was observed visually in 10–15 min using gold nanoparticle reporters. The method was evaluated employing binary mixtures of PCR products from fresh tissues and mixtures of DNA isolates from heat-treated tissues (canned products) at adulteration percentages of 1–100%. The results showed that the method was reproducible and specific for each tuna species. As low as 1% of tuna adulteration was detected with the naked eye. [ABSTRACT FROM AUTHOR]

During recent decades, the health of ocean ecosystems and fish populations has been threatened by overexploitation, pollution and anthropogenic‐driven climate change. Due to a lack of long‐term ecological data, we have a poor grasp of the true impact on the diet and habitat use of fishes. This information is vital if we are to recover depleted fish populations and predict their future dynamics. Here, we trace the long‐term diet and habitat use of Atlantic bluefin tuna (BFT), Thunnus thynnus, a species that has had one of the longest and most intense exploitation histories, owing to its tremendous cultural and economic importance. Using carbon, nitrogen and sulphur stable isotope analyses of modern and ancient BFT including 98 archaeological and archival bones from 11 Mediterranean locations ca. 1st century to 1941 CE, we infer a shift to increased pelagic foraging around the 16th century in Mediterranean BFT. This likely reflects the early anthropogenic exploitation of inshore coastal ecosystems, as attested by historical literature sources. Further, we reveal that BFT which migrated to the Black Sea–and that disappeared during a period of intense exploitation and ecosystem changes in the 1980s–represented a unique component, isotopically distinct from BFT of NE Atlantic and Mediterranean locations. These data suggest that anthropogenic activities had the ability to alter the diet and habitat use of fishes in conditions prior to those of recent decades. Consequently, long‐term data provide novel perspectives on when marine ecosystem modification began and the responses of marine populations, with which to guide conservation policy. [ABSTRACT FROM AUTHOR]

Climate change and size-selective overexploitation can alter fish size and growth, yet our understanding of how and to what extent is limited due to a lack of long-term biological data from wild populations. This precludes our ability to effectively forecast population dynamics and support sustainable fisheries management. Using modern, archived, and archaeological vertebrae dimensions and growth rings of one of the most intensely exploited populations, the eastern Atlantic and Mediterranean bluefin tuna (Thunnus thynnus , BFT), we estimated catch-at-size and early-life growth patterns from the 3rd century bce to the 21st century ce to understand responses to changes in its environment. We provide novel evidence that BFT juvenile growth increased between the 16th–18th, 20th, and 21st centuries, and is correlated with a warming climate and likely a decrease in stock biomass. We found it equally plausible that fisheries-induced evolution has acted to increase juvenile BFT growth, driving earlier maturation as a result of size-selective exploitation. Coincidently, we found limited evidence to suggest a long history of large ( >200 cm FL) BFT capture. Instead, we found that the catch-at-size of archaeological BFT was relatively small in comparison with more intensive, 20th and 21st century tuna trap fisheries which operated further from shore. This complex issue would benefit from studies using fine-scale biochronological analyses of otoliths and adaptation genomics, throughout the last century especially, to determine evolutionary responses to exploitation, and further disentangle the influence of temperature and biomass on fish growth. [ABSTRACT FROM AUTHOR]

Atlantic bluefin tuna (Thunnus thynnus) is the most important tuna species in Mediterranean tuna fishery and a valuable commodity on the global fish market. Croatia is a pioneer in tuna farming in the Mediterranean and the only country that has the exclusive right to farm wild-caught juvenile tuna (8 to 30 kg). This paper identifies key challenges to the sustainability of current farming and fattening practices, primarily economic and environmental, and possible solutions to overcome these challenges. This paper analyses data on tuna catch and aquaculture production (FAO FishStatJ and EU-Eurostat database) and updates the latest literature on farming practices, production challenges related to biotechnical, economic and environmental issues, the market and current legislation in Croatia, as well as fattening in other Mediterranean countries. Tuna capture-based aquaculture is attractive to investors because it promises high returns, but the sustainability of intensive tuna farming and fattening is questionable and raises many ethical issues. Tuna farming and fattening relies on wild fish for stocking and feeding, and further expansion of tuna farming and fattening is limited by the size of wild tuna and small fish populations. To meet the growing global demand for tuna and to conserve wild tuna stocks, further investments are needed. The knowledge gained in Croatian tuna farming is valuable for future sustainable close-cycled tuna farming in the Mediterranean. Due to its good environmental status, the availability of small pelagic fish, the availability of a highly qualified and well-organised labour force, the good cooperation between producers and researchers, and the application of modern farming technologies, ABFT farmed in Croatia have high quality and a good reputation on the market. The main weakness of Croatian tuna farming is that the entire industry is dependent on the Japanese market, but this can be overcome by the possibility of product diversification for new markets, including the tourism industry. [ABSTRACT FROM AUTHOR]

Copyright of South China Fisheries Science is the property of South China Fisheries Science Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Controversies remain regarding the periodicity, or seasonality, of otolith growth band formation, which directly influences a correct age determination of Atlantic bluefin tuna using this structure. The aim of this work was to apply marginal increment analysis and marginal edge analysis to determine the timing of band deposition. The index of completion was analyzed using general additive models to evaluate the importance of variables, such as month, age/size, and reader. Results indicate that the opaque band formation begins in June and is completed by the end of November. From the end of the year to the beginning of the following year, there is minimal marginal edge growth as the translucent band begins to form. The translucent zone then reaches a maximum development in May. The results obtained in this study provide evidence that the annulus formation in the otoliths of Atlantic bluefin tuna are completed later in the calendar year than previously thought. This would mean it is necessary to delay the date of the current July 1st adjustment criterion to November 30. [ABSTRACT FROM AUTHOR]

Simple Summary: We investigated the influence of the lunar cycle on bluefin tuna prey composition in the Strait of Messina by stomach content analysis. We tested if the lunar phases could determine changes in mesopelagic prey composition and abundance. Moreover, we considered two potential impacts of the lunar cycle: the lunar irradiance and the strength of currents. These factors could affect availability of mesopelagic prey in upper waters of the study area. Mesopelagic fish and cephalopod prey were 60.7% of overall diet by number. In summary, the Strait of Messina has highly specific hydrodynamic and biological features which strongly depend on upwelling currents, which in turn are influenced by the lunar cycle (new and full moon with strong currents, quarters with fewer currents). Upwelling causes water mixing, bringing to the surface a large amount of mesopelagic fauna which become more readily available to tuna. Lunar irradiance contributes to the variation of prey composition, increasing the success of visual predation on mesopelagic resources at high light in the water column. The influence of the lunar cycle on bluefin tuna foraging in the upwelling area of the Strait of Messina was investigated by exploring trophic interaction with mesopelagic fish and cephalopod prey. To focus on how the lunar cycle could affect availability of mesopelagic prey for this predator, we tested potential differences in the diet related to each lunar phase. Moreover, we considered two potential impacts of the lunar cycle: the lunar irradiance and the strength of currents. Overall, 2672 prey items were mesopelagic fish and cephalopods, representing 60.7% of overall diet by number. The main mesopelagic fish prey items were lanternfishes and dragonfishes, while Onychoteuthis banksii was the most important cephalopod prey. In summary, the Strait of Messina has highly specific hydrodynamic and biological features which strongly depend on upwelling currents, which in turn are influenced by the lunar cycle (new and full moon with strong currents, quarters with fewer currents). Upwelling causes water mixing, bringing to the surface a large amount of mesopelagic fauna which become more readily available to tuna. Lunar irradiance contributes to the variation of prey composition, increasing the success of visual predation on mesopelagic resources at high light in the water column. [ABSTRACT FROM AUTHOR]

Estimated larval backward trajectories of three Tuna species, namely, Atlantic Bluefin Tuna (Thunnus thynnus, Linnaeus, 1758), Bullet Tuna (Auxis Rochei, Risso, 1801) and Albacore Tuna (Thunnus alalunga, Bonnaterre, 1788) in the central Mediterranean Sea, were used to characterize their spawning habitats, and to assess the impact of changes due to the major environmental parameters (i.e., sea surface temperature and chlorophyll-a concentration) on larval development during their advection by surface currents. We assumed that the environmental variability experienced by larvae along their paths may have influenced their development, also affecting their survival. Our results showed that the Tuna larvae underwent an accelerated growth in favorable environmental conditions, impacting on the notochord development. In addition, further updated information on spawning and larval retention habitats of Atlantic Bluefin Tuna, Bullet and Albacore Tunas in the central Mediterranean Sea were delivered. [ABSTRACT FROM AUTHOR]

The purse seine fishery in the Mediterranean represents about 60% of the international catch for Atlantic Bluefin Tuna (Thunnus thynnus). Yet, tagging operations from this segment of the fisheries remain rare and despite its potential importance for management, several aspects related to the migratory behavior of Atlantic Bluefin Tuna from these areas remain unaddressed. In the present manuscript, we report the results of two tagging operations carried out on a commercial purse seiner during two consecutive years in the spawning ground around the Maltese islands in the Central Mediterranean Sea. During these operations, eight individuals were tagged and the results showed that the larger fish (> 200 cm) undertook large-scale migrations outside the Mediterranean, whereas smaller individuals did not. This study suggests that size might affect the migratory behavior of Atlantic Bluefin Tuna, and underlines the potential of large-scale tagging operations from spawning grounds to address scientific questions having significant management implications. [ABSTRACT FROM AUTHOR]

At the behest of the Green Deal, circular economy concepts are currently being widely promoted, not least within the aquaculture sector. The current study aims to demonstrate the technical feasibility of extracting collagen and fish oils from waste Atlantic bluefin tuna biomass originating from the Maltese aquaculture industry. For collagen, a three-stage methodology, consisting of pre-treatment, extraction, and retrieval, was applied to biomass originating from bone, skin, muscle, and internal organs (offal) in order to extract both acid-soluble collagen (ASC) and pepsin-soluble collagen (PSC). The chemical identity of the extracted collagen was confirmed through the conduction of hydroxyproline and SDS-PAGE tests as well as through FTIR, whilst the extracted collagen was also tested for its microbiological and heavy metal profiles. The collagen yield was found to be highest for skin tissue and for PSC-based protocols and is comparable to the yield cited in the literature for other tuna species. Oils were extracted through low temperature, high temperature, and enzymatic means. The fatty acid profile of the extracted oils was assessed using GC-FID; this indicated high proportions of EPA and DHA. Yield indicated that the enzymatic extraction of oil is most effective. High heat and the presence of iron-containing muscle starting material promote oxidation and rancidity. Further effort into the optimization of both collagen and lipid extraction protocols must be invested, with a special focus on the production of high-value fractions that are much closer to the quality required for human use/consumption. [ABSTRACT FROM AUTHOR]

The spawning grounds of the Atlantic bluefin tuna (Thunnus thynnus) are traditionally considered to be the Gulf of Mexico (Gulf of Mexico) and the Mediterranean Sea (Mediterranean Sea). However, for the western Atlantic, unequivocal evidence of bluefin spawning outside the Gulf of Mexico has been shown. In this study we present the first records of genetically confirmed bluefin larvae in the southern Bay of Biscay (eastern Atlantic). These findings provide evidence of bluefin spawning activity outside the Mediterranean Sea, in the north‐eastern Atlantic. However, our results suggest that the bluefin spawning in the Bay of Biscay is a sporadic phenomenon. [ABSTRACT FROM AUTHOR]

The highly migratory Atlantic bluefin tuna (ABFT) is currently managed as two distinct stocks, in accordance with natal homing behavior and population structuring despite the absence of barriers to gene flow. Larval fish are valuable biological material for tuna molecular ecology. However, they have hardly been used to decipher the ABFT population structure, although providing the genetic signal from successful breeders. For the first time, cooperative field collection of tuna larvae during 2014 in the main spawning area for each stock, the Gulf of Mexico (GOM) and the Mediterranean Sea (MED), enabled us to assess the ABFT genetic structure in a precise temporal and spatial frame exclusively through larvae. Partitioning of genetic diversity at nuclear microsatellite loci and in the mitochondrial control region in larvae spawned contemporarily resulted in low significant fixation indices supporting connectivity between spawners in the main reproduction area for each population. No structuring was detected within the GOM after segregating nuclear diversity in larvae spawned in two hydrographically distinct regions, the eastern GOM (eGOM) and the western GOM (wGOM), with the larvae from eGOM being more similar to those collected in the MED than the larvae from wGOM. We performed clustering of genetically characterized ABFT larvae through Bayesian analysis and by Discriminant Analysis of Principal Components (DAPC) supporting the existence of favorable areas for mixing of ABFT spawners from Western and Eastern stocks, leading to gene flow and apparent connectivity between weakly structured populations. Our findings suggest that the eastern GOM is more prone for the mixing of breeders from the two ABFT populations. Conservation of this valuable resource exploited for centuries calls for intensification of tuna ichthyoplankton research and standardization of genetic tools for monitoring population dynamics. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Fish Biology is the property of Verlag Natur & Wissenschaft and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The reproductive success of fish populations depends on their reproductive potential and offspring survival to maturity. The reproductive potential affects recruitment and hence populations' resilience and productivity. Extensive research carried out throughout the current century has improved our understanding of the reproductive biology of the Atlantic bluefin tuna (ABFT), Thunnus thynnus. Yet, crucial questions still remain unresolved. This paper examines key factors that drive ABFT reproductive performance (maturity, spawning frequency, fecundity, sex ratio, spawning habitat). Some reproductive variables (spawning at age, spawning omission, egg and offspring viability, parental effect) remain poorly investigated due to the enormous challenge of implementing the required research across the distribution range and over time. These fundamental traits of the reproductive life history, however, provide valuable information to fish stock assessment models and hence require further attention. There is a major debate as to the extent of similarity in reproductive traits between eastern and western ABFT stocks. Both stocks have been considered to display differing maturity schedules, which would result in different spawning rates and reproductive outputs. Yet, similarities have been found in major reproductive aspects suggesting that discrepancies between stocks may not be as broad as often assumed. Though substantial, the information acquired on ABFT reproduction over the years is still incomplete for adequately advising fisheries management. The present report provides a synthesis of the existing information on the reproductive biology of ABFT. It also identifies major research needs and analyses future research actions towards bridging current gaps in ABFT reproduction science. [ABSTRACT FROM AUTHOR]

Copyright of Bulletin of Fish Biology is the property of Verlag Natur & Wissenschaft and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The mineral component of fish otoliths (ear bones), which is aragonitic calcium carbonate (CaCO3), makes this structure the preferred sample choice for measuring biological carbon and oxygen-stable isotopes in order to address fundamental questions in fish ecology and fisheries science. The main drawback is that the removal of otoliths requires sacrificing the specimen, which is particularly impractical for endangered and commercially valuable species such as Atlantic bluefin tuna (Thunnus thynnus) (ABFT). This study explores the suitability of using the first dorsal fin spine bone of ABFT as a non-lethal alternative to otolith analysis or as a complementary hard structure. The fin spines of freshly caught ABFT were collected to identify carbonate ions within the mineral matrix (i.e., hydroxyapatite) and to determine the nature of the carbonate substitution within the crystal lattice, knowledge which is crucial for correct measurement and ecological interpretation of oxygen and carbon stable isotopes of carbonates. Fin spine sections were analyzed via X-ray Photoelectron Spectroscopy (XPS), Raman Spectroscopy, and Fourier Transform InfraRed (FTIR). The XPS survey analysis showed signals of Ca, O, and P (three compositional elements that comprise hydroxyapatite). The Raman and FTIR techniques showed evidence of carbonate ions within the hydroxyapatite matrix, with the IR spectra being the most powerful for identifying the type B carbonate substitution as shown by the carbonate band in the v2 CO32− domain at ∼872 cm−1. The results of this study confirmed the presence of carbonate ions within the mineral matrix of the fin spine bone of ABFT, showing the feasibility of using this calcified structure for analysis of stable isotopes. Overall, our findings will facilitate new approaches to safeguarding commercially valuable and endangered/protected fish species and will open new research avenues to improve fisheries management and species conservation strategies. [ABSTRACT FROM AUTHOR]

Among the many fish species commercially exploited since prehistoric times, Atlantic bluefin tuna (Thunnus thynnus) is one of the most economically significant, having left an indelible imprint on several civilizations including the Phoenicians, Greeks, and Romans. Here, we describe our efforts to identify tuna specimens among the remains of 345 fish vertebrae and bones in several large collections from the Atlantic Ocean, Mediterranean Sea, and Black Sea, dating from the Late Iron Age (2nd century BCE) to the early 20th century (1911–1927). Unfortunately, ancient fish specimens are often mislabelled, which can cause a great deal of confusion among zoologists. Protocols were developed and optimized to overcome the unique challenges related to the compromised integrity of genetic material preserved in ancient bones. Three DNA isolation protocols were compared to maximize yields, and as reported for other faunal remains, a silica spin column‐based method was proven most effective. Endogenous DNA was successfully extracted from the majority of bones and amplified using polymerase chain reactions (PCRs) and an assortment of four primer pairs targeting nuclear (internal transcribed spacer) and mitochondrial sequences (cytochrome oxidase subunit 1 and control region). Protocols targeting mitochondrial markers were more successful than those focused on nuclear targets. Due to the restricted length of the extracted DNA molecules, character‐based keys containing diagnostic nucleotide substitutions were defined and used to identify 231 samples to genera, of which 171 were identified to species level. The success rate of assignment of specimens to species level varied between location and collection, reflecting variation in DNA preservation between different sites and environments. The methods detailed herein can be used to identify other ancient fish specimens and provide information about historical human diets, trade, species distribution, and biodiversity. The same tools can be applied to the analysis of processed food items with highly damaged DNA. [ABSTRACT FROM AUTHOR]

Summary: The Atlantic bluefin tuna (ABFT), Thunnus thynnus (Linnaeus, 1758), is an important commercial species managed as two different stocks, western and eastern Atlantic, with their spawning grounds in the Gulf of Mexico and in the Mediterranean Sea, respectively. The eastern Atlantic stock has been overexploited in the last decades, leading to the application of specific management measures introduced by the International Commission for the Atlantic Tuna (ICCAT). A clear understanding of the genetic structure of ABFT Mediterranean population should be pursued in order to support management decisions. To date the genetic studies on the Mediterranean ABFT, carried out with different molecular markers and sampling procedures, have produced unclear results. Here, we analysed ABFT samples from central and western Mediterranean Sea with mitochondrial sequences and 11 microsatellite loci to investigate, among the others, the area of the Strait of Messina, where environmental conditions seem to support a resident population of ABFT. Furthermore, genetic analyses of mitochondrial sequences were carried out including nucleotide sequences of Adriatic ABFT wild larvae retrieved from GenBank. Among the investigated areas a genetic differentiation was detected between the Strait of Messina and the Tyrrhenian Sea with microsatellite loci according to the exact G test, but not to the Bayesian analyses carried out with STRUCTURE. The analyses with mitochondrial sequences do not reveal any differentiation among sampled areas, however, a highly significant genetic divergence was observed between the Adriatic mitochondrial sequences retrieved from GenBank and the central‐western Mediterranean sequences obtained in the present work. Our results provide some evidence of population structure of Mediterranean ABFT adding pieces to a still unclear picture. [ABSTRACT FROM AUTHOR]

This study aims to clarify some aspects of the growth of Atlantic bluefin tuna, Thunnus thynnus (L.), (ABFT) mainly regarding parameters of the growth equation and of relative growth, in this case length-weight relationships. There is a great volume of literature on these matters and there is a danger that the resulting confusion may give rise to mistaken decisions. In spite of the publication of 55 articles on absolute growth (FL > 50 cm), which contain a total of 43 growth equations, no consensus has yet been reached within the ABFT assessment group (AG) of the SCRS on parameters such as Lmax and L∞. The results of the present study indicate that the L∞ = 314.9 cm of the growth equation used for the western stock by the AG from 2010 (Lt = 314.9 [1 - e-0.089 (t+ 1.13)]), which was discarded in 2016, lies within the confidence limits of the maximum Ls presented in this study (Lmax= 321.4 ± 8.7 cm), confirming that this equation fit the biology of the ABFT growth. With regard to the length-weight relationships, 38 articles (FL > 50 cm) have been consulted containing a total of 71 equations, but in spite of this the models adopted by the AG in 2014 underestimate the weight of spawners (>2 m) in high fattening phase by up to 23%. The coincidence of the length-weight model for the ABFT western stock, discarded by the AG in 2014, with that of Pacific bluefin tuna, Thunnus orientalis (T & S), (PBFT) indicates that both species must have the same growth, something that is not surprising since both were the same species until 2003. Other coincidences, such as the trend of condition factor K in adults and the growth in the first months of life, could ratify it. In the Pacific Ocean, where far fewer growth studies have been made on PBFT than on ABFT in the Atlantic and Mediterranean, the management of growth models for the purposes of stock assessment in the International Scientific Committee (ISC) makes more sense than that carried out by the SCRS on this matter. [ABSTRACT FROM AUTHOR]

Copyright of Estudis Romànics is the property of Institut d'Estudis Catalans and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Environment-recruitment relationships can be difficult to delineate with parametric statistical models and can be prone to misidentification. We use non-parametric time-series modeling which makes no assumptions about functional relationships between variables, to reveal environmental influences on early life stages of bluefin tuna and demonstrate improvement in prediction of subsequent recruitment. The influence of sea surface temperature, which has been previously associated with larval growth and survival, was consistently detected in recruitment time series of bluefin tuna stocks that spawn in the Mediterranean Sea, the North Pacific, and the Southern Ocean. Short time series for the Gulf of Mexico stock may have precluded a clear determination of environmental influences on recruitment fluctuations. Because the non-parametric approach does not require specification of equations to represent system dynamics, predictive models can likely be developed that appropriately reflect the complexity of the ecological system under investigation. This flexibility can potentially overcome methodological challenges of specifying structural relationships between environmental conditions and fish recruitment. Consequently, there is potential for non-parametric time series modeling to supplement traditional stock recruitment models for fisheries management. [ABSTRACT FROM AUTHOR]

Background: Elucidating the patterns of the Atlantic Bluefin tuna [ABFT, Thunnus thynnus (Linnaeus, 1758)] population structure constitutes a challenging task of great importance. Most of the unique challenges stem from its biology, as well as the attributes of the marine realm in which it disperses. Accurate information is urgently needed for stock assessment, and the identification of critical features to the persistence and adaptation of populations in order to formulate and adopt effective strategies for ABFT conservation and management. Conclusions of a great number of ABFT genetic studies on the Mediterranean Sea stock structure are rather controversial and not yet conclusive. In this study, ABFT genomic diversity was investigated in the Mediterranean Sea, which is the most important area for the species' reproduction. Results: Analyzing genome-wide SNPs and microsatellites from ABFT samples collected throughout the Mediterranean Sea did not provide strong evidence of genetic structure, pointing towards the existence of a single panmictic unit. An alternative view would recognize a failure to reject the null hypothesis of a panmictic unit as an effect of the study's sampling design, the type of markers used, and the effectiveness/suitability of analysis methods in respect to the species biological characteristics or any combination of the above. Conclusions: Unravelling the drivers of ABFT population diversity would require the consideration of important aspects of the species spawning behavior for the determination of the appropriate sampling design. Novel approaches and methods of analysis that will bring together experts in genetics/-omics, ecology and oceanography are deemed necessary. Analyzing ABFT genetic data under the discipline of seascape genetics could provide the analysis framework under which major abiotic and biotic forces controlling ABFT recruitment could be identified, elucidating the complicated population dynamics of the species, while multiple and continuous fisheries monitoring should in all cases be considered as a prerequisite in order to achieve efficient and long-term ABFT conservation. [ABSTRACT FROM AUTHOR]

Atlantic blue fin tuna (Thunnus thynnus) is a species of great importance for Mediterranean Sea area, from both ecological and commercial points of view. The scientific literature reports few data on the contamination of this fish by emerging organic compounds such as perfluorinated alkylated substances (PFASs) and phthalates, being the latter never been studied in tuna. This study therefore investigated the presence of the PFASs perfluorooctane sulphonate (PFOS) and perfluoroctanoic acid (PFOA) and the phthalate di-2-ethylhexyl phthalate (DEHP), also monitored by its metabolite mono-2-ethylhexyl phthalate (MEHP), to assess both the state of contamination of Atlantic bluefin tuna specimen and the risk due to the toxicity of these compounds for human consumption. While PFOA was never found, detectable levels of PFOS (0.4-1.88 ng/g), DEHP (9-14.62 ng/g) and MEHP (1.5-6.30 ng/g) were found. The results were elaborated relating the accumulation to the size and age of the individuals and showed a correlation between the levels of different pollutants investigated. [ABSTRACT FROM AUTHOR]

The fatty acid profile of crevalle jack was compared with that of Atlantic bluefin tuna, Atlantic Spanish mackerel, red snapper, and Nile tilapia. Crevalle jack and Atlantic Spanish mackerel showed similarities in their fatty acid profiles, with the saturated fatty acid > monounsaturated fatty acid > polyunsaturated fatty acid pattern. Atlantic bluefin tuna and red snapper followed a similar pattern to each other, with the polyunsaturated fatty acid > saturated fatty acid > monounsaturated fatty acid pattern, and the pattern for Nile tilapia was saturated fatty acid > monounsaturated fatty acid ≈ polyunsaturated fatty acid. In winter, the DHA+EPA content of crevalle jack (493.2 mg/100 g fillet) was 37% lower than Atlantic bluefin tuna and Atlantic Spanish mackerel, 35% higher than for the red snapper, and 2.8 fold higher than for the Nile tilapia. The best nutritional indices were for Atlantic bluefin tuna > red snapper > Atlantic Spanish mackerel > crevalle jack > Nile tilapia. [ABSTRACT FROM PUBLISHER]

The recently adopted model by ICCAT Standing Committee on Research and Statistics (SCRS) for the western Atlantic bluefin tuna (ABFT),Thunnus thynnus(L.)(RW= 0.0000159137SFL3.020584,WEST), together with the model used to date (RW= 0.0000152 SFL3.0531,Ec1) is analyzed in using a bi-variant sample (SFL(cm),RW(kg)) of 698 pairs of data (K= 2.02 ± 0.23 SD) in order to validate them and to establish the model that fits best the reality represented by the sample and, therefore, will have the greatest descriptive and predictive power. The result of the analysis indicates that the adopted modelWESTclearly underestimates the weight of spawning ABFT being modelEc1 that best explains the data of the sample. The result of the classical statistical analysis is confirmed by means of the quantile regression technique, selecting the quantiles 5%, 25%, 50%, 75%, and 95%. Other biological and fisheries indicators also conclude that the modelWESTgradually underestimates the weight of ABFT spawners (of 2–3 m) by 11–13%, does not meet the criterion that forRW= 725 kg (Wmax),SFL= 319.93 ± 11.3 cm (Lmax), and the average value ofK(1.77) obtained for a wide range of size–weight values, usingWESTmodel, represents ABFT in low fattening condition. [ABSTRACT FROM PUBLISHER]

Background: The largest of the tuna species, Atlantic bluefin tuna (Thunnus thynnus), inhabits the North Atlantic Ocean and the Mediterranean Sea and is considered to be an endangered species, largely a consequence of overfishing. T. thynnus aquaculture, referred to as fattening or farming, is a capture based activity dependent on yearly renewal from the wild. Thus, the development of aquaculture practices independent of wild resources can provide an important contribution towards ensuring security and sustainability of this species in the longer-term. The development of such practices is today greatly assisted by large scale transcriptomic studies. Results: We have used pyrosequencing technology to sequence a mixed-tissue normalised cDNA library, derived from adult T. thynnus. A total of 976,904 raw sequence reads were assembled into 33,105 unique transcripts having a mean length of 893 bases and an N50 of 870. Of these, 33.4 % showed similarity to known proteins or gene transcripts and 86.6 % of them were matched to the congeneric Pacific bluefin tuna (Thunnus orientalis) genome, compared to 70.3 % for the more distantly related Nile tilapia (Oreochromis niloticus) genome. Transcript sequences were used to develop a novel 15 K Agilent oligonucleotide DNA microarray for T. thynnus and comparative tissue gene expression profiles were inferred for gill, heart, liver, ovaries and testes. Functional contrasts were strongest between gills and ovaries. Gills were particularly associated with immune system, signal transduction and cell communication, while ovaries displayed signatures of glycan biosynthesis, nucleotide metabolism, transcription, translation, replication and repair. Conclusions: Sequence data generated from a novel mixed-tissue T. thynnus cDNA library provide an important transcriptomic resource that can be further employed for study of various aspects of T. thynnus ecology and genomics, with strong applications in aquaculture. Tissue-specific gene expression profiles inferred through the use of novel oligo-microarray can serve in the design of new and more focused transcriptomic studies for future research of tuna physiology and assessment of the welfare in a production environment. [ABSTRACT FROM AUTHOR]

Following an extensive description and review of the bibliography of the overall situation of the bluefin tuna,Thunnus thynnus(L.), ABFT, from ancient times until the present, the eastern Atlantic fisheries that traditionally caught ABFT spawners (traps of the Strait of Gibraltar and northern European fisheries) are described with the aim of explaining the reasons behind their decline from the 1960s. The study includes the fishery of the Bay of Biscay, an area where small and medium-sized spawners migrated towards areas of trophic concentration in the north of Europe. The fisheries of ABFT juveniles began to develop in the eastern Atlantic at the end of the 1940s (Bay of Biscay) and the middle of the 1950s (off the coast of Morocco). The results of an analysis of the juvenile ABFT population of the eastern Atlantic part between 1949 and 1962 reveal that under different scenarios the high fishing mortality exerted on the juvenile fish groups (<5 years) in the period studied may have been one of the main factors behind the decline of the north eastern Atlantic fisheries of spawners from 1963. Juvenile catches of that magnitude (6,879,967 ABFT) may have given rise to the limited recruitment from juvenile age to spawning stocks. The analysis has also been made for the periods 1970–2006 and the present (2009). In the first of these two cases, fishing mortality (F) fell as a result of a fall in the catch of juveniles, mainly the fishery of Morocco. Nevertheless, during these years, over 4 million specimens of 1 year were caught illegally in the Atlantic part of the eastern stock. The fall in F is now even greater due to the practically entire disappearance of the juvenile fisheries as a result of the implementation of the Pluriannual Recovery Plan (PRP) of theInternational Commission for the Conservation of Atlantic Tunas(ICCAT), which began in the fisheries of the eastern stock in 2007. [ABSTRACT FROM AUTHOR]

Mitochondrial DNA locus cytochrome oxidase I was used to asses intraspecific genetic diversity of a didymozoid species Didymosulcus katsuwonicola. Adult forms of this species live encapsulated in pairs in the gills of the reared Atlantic bluefin tuna (Thunnus thynnus). The life cycle of this food-borne parasites and its migration in the host tissues after releasing from the digestive tract to the definitive site in the gills are unknown. Our goal was to assess whether two encysted didymozoids share the same haplotype, indicative of a common maternal origin, as well as the extent of cross- in respect to self-fertilization strategy. Intraspecific comparison showed high haplotype diversity, while the presence of two matching haplotypes within a single cyst encompassed only 17% of sampled individuals. This infers that cross-fertilization between paired individuals within the cyst is more common mechanism than self-fertilization. Such hermaphroditic parasite's trait suggests the existence of intricate infection and reproduction mechanisms, presumably as an adaptation for successful fulfillment of their indirect life cycle through dissemination of genetically more diverse and consequently more fit offspring. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the current levels of heavy metals and trace elements in Atlantic bluefin tuna muscle tissues and how they are influenced by the fattening process and various life history parameters to ascertain whether the concentrations in muscle tissue exceed the maximum levels defined by the European Commission Decision and to evaluate the health risk posed by fish consumption. A total of 20 bluefin tuna reared in sea cages, ranging from 160 to 295 cm in length and from 80 to 540 kg in weight, were sampled from a bluefin tuna farm in the Ionian Sea. The condition factor K of each specimen was calculated and their age was estimated. Heavy metal and trace element (Hg, Zn, Fe and Cu) contents were determined in muscle tissue using cold vapour atomic absorption spectrometry and flame and graphite furnace atomic absorption spectrometry. The total Hg concentrations ranged from 0.28 to 1.28 mg kg–1 w/w, Zn from 5.81 to 76.37 mg kg–1 w/w, Fe from 12.14 to 39.58 mg kg–1 w/w, and Cu from 0.36 to 0.94 mg kg–1 w/w. Only 5% of the muscle samples of tuna contained Hg above the maximum level laid down by the European Commission Decision. Moreover, 15% of the muscle samples contained Zn above the maximum level, while Fe and Cu concentrations were within the acceptable tolerable guideline values. The reared bluefin tuna had lower concentrations of Hg than the wild ones from the Mediterranean Sea. Hg and Fe concentrations showed a positive relationship with size and age of bluefin tuna, whereas negative relationships were found for the concentrations of Zn and Cu. The estimated dietary intake values of the analysed metals were mostly below the derived guidelines. [ABSTRACT FROM PUBLISHER]

Prey size selectivity in piscivorous fish larvae is important to both aquaculture and fisheries science, but laboratory experiments are few. We analyzed selective foraging in Atlantic bluefin tuna larvae (Thunnus thynnus) using two larval fish prey species. The experiments revealed that selective foraging of prey sizes differed among bluefin tuna predator sizes (15–25 mm SL) and prey species, bonito (Sarda sarda) and seabream (Sparus aurata). The observed pattern suggest a general preference for small bonito prey larvae but large seabream prey. Thus, prey size alone is not the only trait responsible for size selectivity in piscivorous fish larvae. [ABSTRACT FROM PUBLISHER]

Following extensive review, a model of the Atlantic bluefin tuna (ABFT),Thunnus thynnus(L.), length–weight relationship for the eastern Atlantic and Mediterranean (RW= 0.0000188SFL3.01247;Ec 1) is presented on the basis of samples of ABFT spawners, with an average value of indexK= 2.03 ± 0.15SD, collected by the Atlantic traps of Portugal and Spain in the Strait of Gibraltar (1963; 1996–1998; 2000–2012), and a set of samples of juvenile fishes from ICCAT–GBYP (n= 707). The resulting model (Ec 1), together with the model used for the eastern stock assessment (RW= 0.000019607SFL3.0092;Ec 2) and a recently adopted by ICCAT Standing Committee on Research and Statistics (SCRS) (RW= 0.0000315551SFL2.898454;EAST) are analyzed in using a bi-variant sample [SFL(cm),RW(kg)] of 474 pairs of data with the aim of validating them and establishing which model(s) best fit the reality represented by the sample and, therefore, will have the greatest descriptive and predictive power. The result of the analysis indicates that the modelEASTclearly underestimates the weight of spawning ABFT and that modelEc 2overestimates it slightly, being modelEc 1that best explains the data of the sample. The result of the classical statistical analysis is confirmed by means of the quantile regression technique, selecting the quantiles 5, 25, 50, 75, and 95%. Other fisheries and biological indicators also conclude that the modelEASTgradually underestimates the weight of ABFT spawners (of 2–3 m) by 9–12.5 %, and does not meet the criterion that forRW= 725 kg (Wmax),SFL= 319.93 ± 11.3 cm (Lmax). [ABSTRACT FROM AUTHOR]

The growth equation currently used for Atlantic bluefin tuna, Thunnus thynnus (L.), eastern stock (Lt = 318.85 [1-e-0.093 (t + 0.97)]) is validated using several approaches. The first method involved a comparison of studies with von Bertalanffy parameter estimates in which, different methods for the age estimation are utilized, taking as references the maximum size of this species (Lmax = 319.93 ± 11.3 cm) and the growth equation of the western Atlantic stock (Lt = 314.90 [1-e-0.089 (t + 1.13)]). The result of this analysis showed that the growth equation used by ICCAT's Standing Committee on Research and Statistics Atlantic bluefin tuna assessment group for the eastern stock perfectly fits Lmax. Second, an analysis was realized from first dorsal spine rings, 578 samples (age groups 0 to 3) of ABFT collected from the Bay of Biscay and the Mediterranean Sea, enabled the interpretation of the wide opaque bands (fast growth), formed during the boreal late spring and completed by autumn (June to November), and the translucent rings (hyaline rings, slow growth), formed during boreal autumn to late spring (November to May-June). In addition, first dorsal spine sections bands of two recovered fish that had carried conventional and electronic archival tags are also consistent. The chronological analysis of the opaque bands and hyaline rings of one fish tagged with an archival tag and recovered in the Bay of Biscay (the first time such a spine had been available for such analysis) revealed that transatlantic migrations may lead to double hyaline ring formation in the spine. Finally, the validation of the ABFT growth equation is made by superimposing tag-recovery data from tagging surveys in the Bay of Biscay, western Mediterranean and western Atlantic (N = 131) and spine readings (N = 299) to the eastern stock ABFT growth equation and analysing residuals. The coefficient of determination (R² = 97.98) and the residual's distribution indicated good performance of the model. Although no important differences between the growth model of the eastern stock and that of the western stock are found, in all cases studied, the predictive accuracy indicators are better for the eastern model. [ABSTRACT FROM AUTHOR]

This study presents the results of an electronic tagging programme on mature Atlantic bluefin tuna (ABFT) that has been conducted since 2007 offshore of the French Mediterranean Coast. The spatial distributions of ABFT showed little year-to-year variation and the fish concentrated in a small area of the central northwestern Mediterranean, where they may stay for several months. The individual tracks display sinuous trajectories in this area, indicating the possibility of feeding behaviour. No fish went out to the North Atlantic, but several fish displayed some migration to the southern western Mediterranean Sea during winter and the central Mediterranean during the spawning season. The homing behaviour of one fish after a full year as well as the back and forth of several fish further indicates that this restricted feeding area is probably persistent from year to year. We hypothesize that this area could result from local enrichment due to permanent mesoscale oceanographic features related to the North Mediterranean Current and the North Balearic front. The option of a spatial management, through marine protected areas, for a highly migratory species, such as ABFT, thus deserves more careful consideration because those species displayed complex spatial dynamics (e.g. homing), and population structure (e.g. several subpopulations of different sizes). [ABSTRACT FROM PUBLISHER]

Atlantic bluefin tuna ( ABFT) has always displayed spectacular changes in its spatial distribution, but the underlying mechanism of such variations still remains obscure. This study focuses on this challenging issue by scrutinizing the intriguing 'Brazilian episode' during which a large quantity of ABFT (a temperate species) was caught during the 1960s in the equatorial Atlantic. To investigate this event, we applied a niche model to an extensive data set of catch and environmental variables from 1960 to 2009. ABFT exhibited a remarkably large ecological niche, which matches well with our current knowledge of ABFT. Our results also depicted a high probability of ABFT occurrence in the South Atlantic and, more interestingly, favorable environmental conditions in the western equatorial Atlantic during the 1960s, but not later. ABFT could thus have migrated from their northern spawning grounds to the South Atlantic during the 1960s through the western equatorial Atlantic, playing the role of an 'ecological bridge'. We argue that the rarity of ABFT in the southern Atlantic during the last four decades would result from the interaction of several processes, particularly oceanographic conditions, migratory behavior, density-dependence, exploitation levels and population structure. Examination of the catch data further indicated that the fish caught in the equatorial Atlantic were from the western stock and we concluded that the lack of rebuilding of this stock could result from a regime shift due to the combination of oceanographic changes in the equatorial Atlantic and overfishing in the North Atlantic in the 1960s and 1970s. [ABSTRACT FROM AUTHOR]

The Atlantic bluefin tuna ( Thunnus thynnus) population in the western Atlantic supports substantial commercial and recreational fisheries. Despite quota establishment and management under the auspices of the International Commission for the Conservation of Atlantic Tunas, only small increases in population growth have been estimated. In contrast to other western bluefin tuna fisheries indices, contemporary estimates of catch per unit effort ( CPUE) in the southern Gulf of St. Lawrence have increased rapidly and are at record highs. This area is characterized by the Cold Intermediate Layer ( CIL) that is defined by waters <3°C and located at depths of 30-40 m in September. We investigated the influence of several in situ environmental variables on the bluefin tuna fishery CPUE using delta-lognormal modelling and relatively extensive and consistent oceanographic survey data, as well as dockside monitoring and mandatory logbook data associated with the fishery. Although there is considerable spatial and temporal variation of water mass characteristics, the amount of available habitat in the southern Gulf of St. Lawrence (assuming a > 3°C thermal ambit) for bluefin tuna has been increasing. The percentage of the water column occupied by the CIL was a significant environmental variable in the standardization of CPUE estimates. There was also a negative relationship between the spatial extents of the CIL and the fishery. Properties of the CIL account for variation in the bluefin tuna CPUE and may be a factor in determining the amount of available feeding habitat for bluefin tuna in the southern Gulf of St. Lawrence. [ABSTRACT FROM AUTHOR]

Information on distribution and abundance of cephalopods inhabiting pelagic water masses is often not available because of the difficulty of applying conventional methods in this remote habitat. An alternative source of information is represented by stomach content analysis of pelagic predators that are known to be efficient cephalopod prey collectors. This study focuses on the occurrence of cephalopod prey in the diet of young-of-the-year bluefin tuna (Thunnus thynnusL. 1758, Pisces: Scombridae) in the southern Tyrrhenian Sea (central Mediterranean). Overall, 139 fishes were sampled by trolling lines or purse-seine in a Fish Aggregating Devices (FADs) area and as by-catch of the purse-seine sardine fishery, from 1998 to 2000 between July and November. Cephalopods found in the stomach contents were identified to the lowest possible taxon and, when digestion was too advanced, beaks from stomachs were considered as the best taxonomic feature for classification. Of a total of 1233 cephalopod prey, 1144 individuals were identified, belonging to 15 species.Onychoteuthis banksiiwas the most common prey (%N = 58.39), followed byHeteroteuthis dispar(%N = 23.03). This importance was confirmed also in terms of biomass withO. banksiiandH. disparthat respectively reached 39.41% and 21.23% in weight, followed byTodarodes sagittatus(%W = 20.16). In general, young-of-the-year bluefin tunas are able to feed on a large spectrum of cephalopod prey in the study area, usually relying on juvenile specimens and epipelagic and mesopelagic shoaling species. In fact, the identified preys mainly belong to muscular squids (71%) and sepiolids (25%), but pelagic octopuses, buoyant squids and juvenile demersal octopuses were also recorded. These data provide further information on the feeding habits ofT. thynnus, relative to a poorly investigated life stage. The improving knowledge on trophic relationships of young tunas and their reliance on cephalopod taxa is an important step in supporting management of this fishery resource. [ABSTRACT FROM AUTHOR]

The optimal management of the commercially important, but mostly over-exploited, pelagic tunas, albacore ( Thunnus alalunga Bonn., 1788) and Atlantic bluefin tuna ( BFT; Thunnus thynnus L., 1758), requires a better understanding of population structure than has been provided by previous molecular methods. Despite numerous studies of both species, their population structures remain controversial. This study reports the development of single nucleotide polymorphisms ( SNPs) in albacore and BFT and the application of these SNPs to survey genetic variability across the geographic ranges of these tunas. A total of 616 SNPs were discovered in 35 albacore tuna by comparing sequences of 54 nuclear DNA fragments. A panel of 53 SNPs yielded FST values ranging from 0.0 to 0.050 between samples after genotyping 460 albacore collected throughout the distribution of this species. No significant heterogeneity was detected within oceans, but between-ocean comparisons (Atlantic, Pacific and Indian oceans along with Mediterranean Sea) were significant. Additionally, a 17- SNP panel was developed in Atlantic BFT by cross-species amplification in 107 fish. This limited number of SNPs discriminated between samples from the two major spawning areas of Atlantic BFT ( FST = 0.116). The SNP markers developed in this study can be used to genotype large numbers of fish without the need for standardizing alleles among laboratories. [ABSTRACT FROM AUTHOR]

During the first 2 years of larval rearing trials with Atlantic bluefin tuna, survival was a challenging issue. As bacterial colonization of the gut has been shown to play a key role for other species, we studied the profiles of the microbiota associated with individual larvae at different stages in three distant hatcheries. The Bacterial Community Profile ( BCP) was quantified based on PCR- DGGE analyses of partial amplicons from 16S rDNA. Considerable individual variability in BCP was observed before onset of feeding, and the BCP did not show regular fluctuation during ontogenesis. Microalgae were added to the rearing tanks in two of the three hatcheries, but it was not possible to distinguish the effect of location from the effect of algal addition on BCP. In one hatchery, the larvae were reared either with algal addition or in mesocosm, but due to high individual variability, no significant difference in BCP was detected between the two groups. It was hypothesized that this variability was caused by differences in health, physiological status and developmental stage of the larvae. A practical conclusion from the study is the need to analyse a considerable number of individuals to reflect statistically significant differences between the microbial communities associated with rearing groups. [ABSTRACT FROM AUTHOR]

Superficial mechanosensory organs (neuromasts) distributed over the head and body of fishes and amphibians form the "lateral line" system. During zebrafish adulthood, each neuromast of the body (posterior lateral line system, or PLL) produces "accessory" neuromasts that remain tightly clustered, thereby increasing the total number of PLL neuromasts by a factor of more than 10. This expansion is achieved by a budding process and is accompanied by branches of the afferent nerve that innervates the founder neuromast. Here we show that innervation is essential for the budding process, in complete contrast with the development of the embryonic PLL, where innervation is entirely dispensable. To obtain insight into the molecular mechanisms that underlie the budding process, we focused on the terminal system that develops at the posterior tip of the body and on the caudal fin. In this subset of PLL neuromasts, bud neuromasts form in a reproducible sequence over a few days, much faster than for other PLL neuromasts. We show that wingless/mt (Wnt) signaling takes place during, and is required for, the budding process. We also show that the Wnt activator R-spondin is expressed by the axons that innervate budding neuromasts. We propose that the axon triggers Wnt signaling, which itself is involved in the proliferative phase that leads to bud formation. Finally, we show that innervation is required not only for budding, but also for long-term maintenance of all PLL neuromasts. [ABSTRACT FROM AUTHOR]

A meta-analysis of the straight fork lengths (herewith abbreviated as L) of 2,458,028 Atlantic bluefin tuna, Thunnus thynnus (L.), taken from 224 scientific publications and unpublished L data from scientific organizations and fishing companies spanning most of the known Atlantic and Mediterranean Atlantic bluefin tuna fisheries dating from 1605 to 2011, give L values ranging from Lmin = 20 cm and Lmax = 330 cm. The results indicate that the parameter L∞ = 318.85 cm of the growth equation used by ICCAT's Standing Committee on Research and Statistics Atlantic bluefin tuna assessment group for the eastern stock (Lt = 318.85 [1 – e−0.093 (t + 0.97)]) lies within the confidence limits of the maximum Ls presented in the study: Lmax = 319.93 ± 11.3 cm, confirming that this equation perfectly fits the biology of the growth of this species. These conclusions are also valid for the equation for the western stock (Lt = 314.90 [1 – e−0.089 (t +1.13)]). The ICCAT Atlantic bluefin tuna database contains numerous records of Atlantic bluefin tuna L outside the biological feasibility, and solutions are provided to recognize and remove these outliers based on the application of fixed values of Fulton's condition factor (K) between 1.4 and 2.6 and appropriate L-W relationships to correct this situation in the future. [ABSTRACT FROM AUTHOR]

The study of feeding habits of the Atlantic bluefin tuna was carried out in 123 specimens, ranging from 115 to 222 cm fork length (FL) and collected during spring seasons of 2010 and 2011 in the central Mediterranean Sea (Strait of Messina). The analysis of stomach contents allowed us to identify 91 taxa of prey items, mainly belonging to Teleostea (54), Cephalopoda (20) and Crustacea (13). The percentage of index of relative abundance ( IRI) shows the highest values for the myctophid Hygophum benoiti (% IRI = 22.854) and the stomiid Chauliodus sloani (% IRI = 15.124), followed by the oegopsid squid Illex coindetii (% IRI = 14.316). The broad spectrum of prey items could suggest a generalist behavior of this predator, with several species that occasionally occurs in its diet. However, if prey are grouped into food categories, the importance of mesopelagic and benthopelagic fishes can be appreciated (54.41 % of % IRI). The assessment of the hypothetical foraging rhythm of the Atlantic bluefin tuna highlighted that its feeding activity is concentrated on diel migrating fauna during night and on larger preys upon daylight. The predation on the high-energetic food as mesopelagic and bathypelagic fishes during the pre-spawning and the spawning period may bring an energetic advantage in tuna metabolism and gonadal maturation [ABSTRACT FROM AUTHOR]

This paper is based on recently recovered daily catch and effort data from the Algarve traps (south of Portugal) during the 1898−1900 period. These 18 traps targeted the two migrations of bluefin tuna, entering and leaving the Mediterranean Sea, each year during a period between mid April and the end of August. Their bluefin catches were significant, corresponding to average yearly catches of 61 000 bluefin, i.e., approximately 7900 t. Migration dates and durations towards and away from the Mediterranean Sea were estimated based on the daily catch per unit effort (CPUE) by the traps. Migration patterns were very stable during these three years. The entry migration took place over an average of 42 days, and the return lasted 53 days. Daily catches show large waves of tunas passing during the two migratory phases. It can be hypothesised that each of these waves of tuna spent about 52 days in the Mediterranean Sea, and that each group was stable and consistent during their arrival and return migrations. Migration trajectories along the Algarve coast can be estimated from the daily CPUEs of the different traps. They appear to be different between the arrival and return migrations. The daily data per trap show that most traps caught entering bluefin at quite low CPUE, whereas only a few traps were efficient for catching the returning bluefin, but with much larger catches and CPUEs. The analysis of catch and CPUEs during the entering and leaving phases allowed us to conclude that the catchability and fishing mortality of the bluefin stock in the Algarve trap fishery was much larger during the return migration. Additional daily data from other traps, both historical and contemporary, should be collected and analyzed in order to provide more comprehensive results on the patterns and changes in migration, stock structure and stock exploitation rate. [ABSTRACT FROM AUTHOR]

Virtual population analysis requires information on the fishing mortality rate (or abundance) for one age group from each cohort. In many cases available data are insufficient to estimate these rates for every age group and structural assumptions must be imposed to reduce the number of effective parameters. Past assessments of western Atlantic bluefin tuna (Thunnus thynnus) have reduced the number of parameters by assuming pre-specified values for the ratios of the fishing mortality rates on adjacent age groups. More recent bluefin tuna assessments have estimated terminal fishing mortality rates (F) on each age with a constraint that restricts change from one year to the next. We explore the implications of these methods of estimating terminal-year F through retrospective analyses of the 2006 bluefin tuna assessment and through stochastic simulations. The use of pre-specified ratios for F created strong retrospective biases and may have led to overly optimistic projections. Constraining annual changes in the terminal-year F appeared to mute retrospective patterns and resulted in abundance projections less prone to spurious initial leaps. Simulation results indicate that the constraint improves estimation, particularly with moderate to low interannual changes in selectivity. [ABSTRACT FROM AUTHOR]

An undescribed species of Microsporidia Balbiani, 1882 was isolated from the muscularis mucosa of the intestinal mucosa of the reared Atlantic bluefin tuna ( Thunnus thynnus). Transmission electron microscopy showed that the pyriform unikaryotic microsporidium, measuring 3.6 μm ± 0.08 in length and 1.8 μm ± 0.04 in width (inferred from TEM sections), had two layers of 14-17 coils of polar filament and a robust manubrium of the filament. No developmental stages were observed in xenoma. Phylogenetic analysis of the small subunit rRNA showed closest similarity with Kabatana spp. (88.4%), clustering the microsporidium together in a sister group with K. takedai and Kabatana sp. (JI-2008)/ K. newberryi clade. While recognized Kabatana members show ovoid, rounded to pyriform spore, lack of sporophorous vesicle or xenoma, 3-10 coils of polar filament in 1-2 rows and are localized within cytoplasm of trunk muscle, the new species is markedly pyriform, xenoma forming, with many filament coils in 2 rows and parasitizing smooth intestinal muscle. Since morphological features were not typically congruent with any of Kabatana spp. so far described and molecular clustering indicated paraphyletic position within Kabatana clade, we suggest assigning described species to collective group Microsporidia, as Microsporidium milevae sp. nov., until more evidence permits potential formation of the new genus. [ABSTRACT FROM AUTHOR]

Copyright of Kafkas Universitesi Veteriner Fakultesi Dergisi is the property of University of Kafkas, Faculty of Veterinary Medicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Time-area closures are commonly used to manage fisheries bycatch and involve temporarily closing an area of the ocean to particular fishing gears. We examine conditions in which implementing a time-area closure would increase the economic value of fisheries, focusing on a case study application in the Gulf of Mexico. Pelagic longline fishermen catch the highly valued Atlantic bluefin tuna ( Thunnus thynnus, Scombridae) on their Gulf of Mexico spawning grounds while fishing for Atlantic yellowfin tuna ( Thunnus albacares). We analyze a multispecies, multifishery bioeconomic model that includes information on migratory patterns from electronic tagged bluefin tuna. We use dynamic optimization to identify management strategies that would maximize the net present value of tuna fisheries, allowing for discounting of future benefits and costs relative to the present. If past fishing mortality rates continue in Atlantic bluefin tuna fisheries, implementing a time-area closure in the Gulf of Mexico incurs economic costs. However, the net present value of the fisheries is increased by implementing a time-area closure as part of a broader commitment to rebuild the heavily depleted bluefin population, provided the discount rate and the costs of such a closure in forgone fishing opportunities are not too large. The increase in economic value offered by a time-area closure is small relative to the overall economic value of rebuilding itself and it may be economically optimal only to implement a closure once sufficient rebuilding has already taken place. [ABSTRACT FROM AUTHOR]

The Atlantic bluefin tuna ( Thunnus thynnus) is an extraordinary fish that has amazed humanity since ancient times. However, the continuous overexploitation of this fishery, particularly in the Mediterranean Sea, could result in a total collapse of this resource. Currently, this species is managed as two stocks: Western Atlantic and Mediterranean-Eastern Atlantic, with a recognized genetic differentiation between them. On the other hand, the population structure within the Mediterranean Sea is still unclear. The biological data supports the idea of two separate populations in the eastern and western Mediterranean basins. However, nuclear microsatellite and mitochondrial DNA (mtDNA) analyses of two samples representative of these two basins result in a lack of heterogeneity. A comparison of these results with previously published studies reveals some discrepancies. We have compared 59 genetic differentiation tests that include samples within the Mediterranean. Of these, about 60% gave significant differentiation while the remaining 40% were non-significant. But, when only nuclear-based loci were considered, genetic differentiation was detected in up to 73% of the cases with an average significant F of only 0.018, whereas the average significant F of the mtDNA-based studies was significantly higher (0.029). However, in some cases, it is difficult to reconcile the biology of the species with the results suggesting genetic differentiation. In conclusion, although it is not yet possible to reach a definitive conclusion about the population structure, but considering all biological and genetic data, we suggest an independent management approach for each basin to avoid the impact of a type II error that could lead to the possible loss of the regional subpopulations. [ABSTRACT FROM AUTHOR]

Copyright of Kafkas Universitesi Veteriner Fakultesi Dergisi is the property of University of Kafkas, Faculty of Veterinary Medicine and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)