Academic literature on the topic 'Thunnus alalunga'

The tuna fish (Thunnus spp.) is highly migratory and commercial tuna fishery. The fish tuna abudance supported ocea-nography and geography condition in North Mallucas Sea. The fishery targets catch increase on fish tuna provided a view of the need for assessment of phylogenetic tuna. The study was conducted to infer the phylogenetic in North Mollucas Sea. The research method was PCR-Sequensing. Moleculer analysis included extraction, Polymerase Chain Reaction (PCR), electrophoresis and DNA sequencing in control region mtDNA locus. Phylogenetic reconstructed with Neigbor joining with Kimura 2-parameter model using MEGA5. The result showed that four clade (bigeye, yellowfin, alalunga and skipjack). Genetic distance between bigeye with yellowfin was (0.084), bigeye with alalunga (0.163), ye-llowfin with alalunga (0.174), bigeye with skipjack (0.294), skipjack with alalunga (0.312) and yellowfin with skipjack (0.297). The overall result showed significant genetic different. That information explain about one populations species tuna. The tuna phylogeography unlimitedin geographic distributions. AbstrakIkan tuna (Thunnus spp.) adalah ikan pelagis yang memiliki kemampuan ruaya dan nilai komersial. Kondisi oseanogra-fis dan letak geografis mendukung kelimpahan stok sumber daya ikan tuna di Perairan Maluku Utara. Aktifitas penang-kapan yang meningkat memberikan pandangan perlu adanya pengkajian filogenetik ikan tuna. Penelitian ini bertujuan untuk memperoleh informasi filogenetik ikan tuna di perairan Maluku Utara. Metode yang digunakan adalah metode PCR-Sekuensing pada lokus mtDNA control region. Analisis molekuler meliputi ekstraksi, Polymerase Chain Reaction (PCR), elektroforesis dan sekuensing DNA. Rekonstruksi pohon filogenetik dengan metode Neighbor joining dengan model evolusi Kimura 2-parameter dilakukan menggunakan aplikasi MEGA5. Hasil penelitian menemukan empat clade spesies ikan tuna yang berbeda (tuna mata besar, sirip kuning, alalunga, dan cakalang). Jarak genetik tuna mata besar (Thunnus obesus) dengan sirip kuning (Thunnus albacares) adalah 0,084; tuna mata besar dengan tuna alalunga (Thunnus albacore) adalah 0,163; tuna sirip kuning dengan tuna alalunga sebesar 0,174; tuna mata besar dengan caka-lang (Katsuwonus pelamis) adalah 0,294; cakalang dengan tuna alalunga adalah 0,312; dan tuna sirip kuning dengan cakalang adalah 0,297. Semua hasil menunjukkan perbedaan genetik signifikan. Namun dapat dijelaskan bahwa spesies tuna berasal dari satu keturunan. Filogeografi tuna tidak memiliki batas distribusi yang nyata spesies.

A proposta do presente trabalho é caracterizar, através de modelos de mistura isotópica (13C e 15N), a dieta de predadores de topo pelágicos do Oceano Atlântico Sudoeste. Para isso, amostras de tecido muscular foram coletadas dos seguintes peixes: Xiphias gladius, Thunnus obesus, Thunnus alalunga, Thunnus albacares, Prionace glauca, Alopias superciliosus e Isurus oxyrinchus. Os resultados indicam que a dieta de X. gladius é composta primariamente de cefalópodes (lulas Ommastrephidae). Um padrão similar é apresentado por T. alalunga, cuja dieta é também composta principalmente por lulas Ommastrephidae. T. albacares e T. obesus apresentam padrões similares de composição da dieta, ambas as espécies alimentam-se primariamente de pequenos peixes pelágicos. A. superciliosus compõe sua dieta principalmente de espécies de Scombridae (T. albacares e T. alalunga), diferentemente de P. glauca, cuja dieta é composta primariamente de peixes pelágicos de menor porte. O uso, de forma conjunta, das informações extraídas tanto do conteúdo estomacal dos predadores, quanto das análises isotópicas de seus tecidos, apresenta-se como um importante passo em direção ao completo entendimento da rede trófica pelágica do Oceano Atlântico Sudoeste.

Thunnus alalunga is an important commercial tuna species widely distributed in the three major oceans and the Mediterranean Sea. The Mediterranean population is currently classified as a data-poor stock and little is known about its basic life history parameters. This study provides the first detailed information on some aspects of the reproductive biology of T. alalunga from the western Mediterranean Sea. A total of 16 104 specimens were measured between 2005 and 2012. The overall sex ratio of females to males was 1.1:1, although the ratio was female biased in fish <70 cm fork length (LF) and male biased in those >75 cm LF. Histological analysis of the ovaries (N = 587) and the monthly variation of the gonadosomatic index for both sexes showed that spawning occurred from June to August, which is a much shorter period than the 7 months reported for T. alalunga in tropical oceanic waters. Thunnus alalunga caught during June and July are capable of spawning daily. The gonadosomatic index values for T. alalunga from the western Mediterranean were up to eight times higher than those of T. alalunga from other oceans. Histological examination of the ovaries showed that the minimum length at sexual maturity of females was 56 cm LF, which is considerably smaller than those estimated for other stocks.

Commercial yield of tunas in the central Pacific increased severalfold between 1952 and 1998. We developed age-structured production models that incorporate information from multiple fisheries to estimate population biomass and recruitment trends of tunas (Thunnus alalunga, Thunnus albacares, Thunnus obesus, and Katsuwonus pelamis) and billfish in the central north Pacific (0°N to 40°N and 130°E to 150°W). Our results suggest that all tuna stocks remain above 40% of 1950s levels, whereas blue marlin (Makaira nigricans) declined to 21% and swordfish (Xiphias gladius) to 56%. Estimated biomasses of juvenile bigeye (T. obsesus) and yellowfin (T. albacares) tuna increased to 112 and 129%, respectively, of 1950s levels. Juvenile albacore (T. alalunga) decreased during the 1970s and 1980s but recovered to historical highs (121%) in recent years. Skipjack (K. pelamis) remained relatively stable between 1952 and 1980, declined by 35% between 1981 and 1990, and then increased to 68% of 1950s levels. These changes generally represent decreases in top predators and increases in small tunas, which make up their prey. Application of stock assessment methods set in a food web context provides an important step toward developing a method that recognizes fishery exploitation as a component of ecosystem dynamics.

Abstract Fish catch species provide essential information for marine resource management. Some international organizations demand fishing vessels to report the species statistics of fish catch. Conventionally, the statistics are recorded manually by observers or fishermen. The accuracy of these statistics is, however, questionable due to the possibility of underreporting or misreporting. This paper proposes to automatically identify the species of common tuna and billfish using machine vision. The species include albacore (Thunnus alalunga), bigeye tuna (Thunnus obesus), yellowfin tuna (Thunnus albacares), blue marlin (Makaira nigricans), Indo-pacific sailfish (Istiophorus platypterus), and swordfish (Xiphias gladius). In this approach, the images of fish catch are acquired on the decks of fishing vessels. Deep convolutional neural network models are then developed to identify the species from the images. The proposed approach achieves an accuracy of at least 96.24%.

This study is on albacore (Thunnus alalunga, Bonnaterre 1788), an epi- and mesopelagic oceanic tuna species cosmopolitan in the tropical and temperate waters of all oceans including the Mediterranean Sea, extending in a broad band between 40°N and 40°S. What it’s known about albacore population structure is based on different studies that used fisheries data, RFLP, mtDNA control region and nuDNA markers, blood lectins analysis, individual tags and microsatellite. At the moment, for T. alalunga six management units are recognized: the North Pacific, South Pacific, Indian, North Atlantic, South Atlantic and Mediterranean stocks. In this study I have done a temporal and spatial comparison of genetic variability between different Mediterranean populations of Thunnus alalunga matching an historical dataset ca. from 1920s composed of 43 individuals divided in 3 populations (NADR, SPAIN and CMED) with a modern dataset composed of 254 individuals and 7 populations (BAL, CYP, LIG, TYR, TUR, ADR, ALB). The investigation was possible using a panel of 94 nuclear SNPs, built specifically for the target species at the University of Basque Country UPV/EHU. First analysis done was the Hardy-Weinberg, then the number of clusters (K) was determined using STRUCTURE and to assess the genetic variability, allele frequencies, the average number of alleles per locus, expected (He) and observed (Ho) heterozygosis, and the index of polymorphism (P) was used the software Genetix. Historical and modern samples gives different results, showing a clear loss of genetic diversity over time leading to a single cluster in modern albacore instead of the two found in historical samples. What this study reveals is very important for conservation concerns, and additional research endeavours are needed.

Albacore tuna (Thunnus alalunga) is a highly migratory species found in all of the worlds oceans. The origin of albacore south of Africa is in question. This species constituted 85% of catches of the South African commercial tuna fishing fleet from 2000-2009 and is an important species in supporting a large boat-based recreational fishery. Albacore were sampled at angling competitions, which offer a repeatable and cheap source of tuna, in the Western Cape of South Africa during 2012 and 2013. 119 Samples were used to determine a length-weight relationship and to provide conversion ratios of various body measurements to fork length when total length was not available. Visual examination of testes and ovaries indicated that albacore are not spawning off the coast of South Africa.A comparison between the ease of using sectioned sagittal otoliths and first dorsal spines indicated that otoliths were more precise for estimating the age of albacore. Von Bertalanffy growth parameters were estimated from 51 fish, ranging from 2-9 years old (L∞=1100.07 mm; K=0.238 y-1; t₀=-2.14). Stomach content analysis indicated that the mesopelagic squid Lycoteuthis lorigera is the most important prey item for South African albacore. δ13C and δ15N stable isotope analysis of albacore and yellowfin tuna (T. albacares) muscle tissue showed that they feed on prey that may depend on different primary producers but that the two species of tuna share the same niche in the southern Benguela food web. Trophic levels of 3.8 and 3.76 were assigned to albacore and yellowfin tuna respectively.

La peche thoniere dans l'ocean atlantique intertropical occidental constitue une activite economique tres importante. Parmi les especes capturees au cours des quarante deux dernieres annees, l'albacore (thunnus albacares), le germon (thunnus alalunga) et le thon obese (thunnus obesus) ont fait l'objet d'une forte exploitation par les flottilles palangrieres. Cependant, l'exploitation de ces ressources est conditionnee par la variabilite hydroclimatique du fait des relations entre les thons et l'environnement. Dans ce contexte, les objectifs de cette etude sont de decrire les conditions hydroclimatiques de cette region de l'atlantique intertropical, notamment la variabilite saisonniere et interannuelle, et d'analyser les relations thons-environnement pour tenter d'identifier les parametres environnementaux susceptibles de jouer un role important sur la distribution et la capturabilite de ces trois especes. Les principaux resultats obtenus nous ont permis d'observer que (i) la zone d'etude peut etre divisee en deux secteurs aux caracteristiques hydroclimatiques differentes separes par le parallele 5\s, mais presentant une dynamique saisonniere tres marquee ; (ii) cette variabilite de l'environnement conditionne largement l'occupation de la zone d'etude (20\w-50\w et la cote bresilienne / 10\n-20\s) par ces trois especes ainsi que leur exploitation ; (iii) le germon presente un comportement obstine par rapport a sa migration de reproduction du fait de sa presence dans une meme zone et a la meme epoque de l'annee pour se reproduire ; (iv) les fortes anomalies positives de temperature de surface de la mer observees dans cette zone de ponte ont ete probablement a l'origine des chutes des indices d'abondance du germon au cours des saisons 1972/1973, 1973/1974 et 1987/1988 ; (v) la structure thermique verticale semble jouer un role important sur la capturabilite du thon obese dont les conditions les plus propices seraient probablement associees a la profondeur et a l'epaisseur de la couche de temperatures optimales pour l'espece ; (vi) l'existence de zones potentiellement favorables a la capture du thon obese dans des couches plus profondes que celles atteintes par la palangre profonde ont ete identifiees : l'une situee entre 10\n-20\n et 40\w-60\w, l'autre au large du cap san roque au nord-est du bresil, entre la cote et le meridien de 30\w. Enfin, ces resultats montrent que les effets de la variabilite de l'environnement sur les ressources et la peche thoniere doivent etre prises en consideration dans la gestion rationnelle de ces ressources.

Aquest treball es centra en el coneixement de l'estructura poblacional de tres espècies piscícoles de la família Scombridae, el bonítol (Sarda sarda), la bacora (Thunnus alalunga) i la tonyina (Thunnus thynnus) en la seva distribució de l'atlàntic i el mediterrani.<br>This work focuses on understanding the population structure of three fish species of the family Scombridae, bonito (Sarda sarda), the figs (Thunnus alalunga) and bluefin tuna (Thunnus thynnus) distribution in the Atlantic and the Mediterranean.

Submitted by (edna.saturno@ufrpe.br) on 2017-02-08T16:07:31Z No. of bitstreams: 1 Bruno de Oliveira.pdf: 2373684 bytes, checksum: 5f89aaf529fed3c21f21b9c51546d9b8 (MD5)<br>Made available in DSpace on 2017-02-08T16:07:31Z (GMT). No. of bitstreams: 1 Bruno de Oliveira.pdf: 2373684 bytes, checksum: 5f89aaf529fed3c21f21b9c51546d9b8 (MD5) Previous issue date: 2010-08-31<br>Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq<br>Analysis between the environmental variability in the pelagic ocean environment, distribution and abundance of the main oceanic fishing resources, have been evaluated in several studies, mainly with the intensification of global climate changes in the recent decades. The main objective of this study was to evaluate the relations between the catches (CPUE) of albacore(Thunnus alalunga) and some environmental parameters, together with spatio temporal data of fishing activities during the period between 1980 and 2007. The fishing data used, including the spatio temporal distribution of effort and catches are referred of long line fleet operations of Brazil (BNDA) and China Taipei (ICCAT). The environmental parameters (SST– Sea Surface Temperature and DML – Depth Mixed Layer) were obtained in international oceanographic data banks. Generalized Additive Models (GAM’s) were used for analyses between CPUE (dependent variable) and the environmental variability. Furthermore, spatio temporal aspect(latitude, longitude, month and year) of fish activity were included, in order to evidence the seasonality in catches. The results obtained show that the environmental variability on oceanographic conditions have a strong influence in the distribution and abundance of albacore, and, consequently, in its catch rate (CPUE). The SST (positive correlation with latitude, for the area of this study) was the most important environmental parameter in catch rates (CPUE). Besides that, we inferred that catches received a positive influence in areas where the thermocline is more superficial and there is a seasonal pattern in the distribution and abundance characteristic. These aspects seem to be in relation with the migratory movements of this specie in the South Atlantic Ocean, including the concentration along the Brazilian coast for spawn in austral summer.<br>Relações entre a variabilidade ambiental do ambiente pelágico oceânico e a distribuição e abundância relativa dos principais recursos pesqueiros oceânicos, vêm sendo avaliadas em diversos estudos, principalmente com a intensificação dos processos de mudanças climáticas, ocorridos em décadas recentes. O objetivo principal deste estudo foi avaliar a relação entre a captura (CPUE) da albacora branca (Thunnus alalunga) e algumas variáveis ambientais, juntamente com dados espaço-temporais da atividade pesqueira, referentes ao período compreendido entre 1980 e 2007. Os dados de pesca utilizados, incluindo a distribuição espaço-temporal do esforço de pesca e das capturas, são referentes à operação da frota espinheleira do Brasil (Banco Nacional da Pesca de Atuns e Afins) e de China Taipei (International Comission for Conservation of Atlantic Tunas, em inglês). Os dados ambientais (TSM – Temperatura da Superfície do Mar e PCM – Profundidade da Camada Mistura) foram obtidos de bancos internacionais de dados oceanográficos. Modelos Aditivos Generalizados (GAM’s) foram utilizados para averiguar as relações entre o rendimento pesqueiro, expresso através da CPUE (variável dependente), e à variabilidade ambiental. Além disto, aspectos espaço-temporais (latitude, longitude, mês e ano) foram incorporados, de modo a evidenciar a sazonalidade das capturas na área do estudo. Os resultados obtidos mostram que à variabilidade ambiental do ambiente oceanográfico influencia fortemente à distribuição e abundância da espécie e, consequentemente, das capturas. A TSM (correlação positiva com a latitude, para a área de estudo) foi o fator ambiental que mais influenciou a CPUE. Além disto, podemos inferir que as capturas sofrem influência positiva em áreas com a termoclina mais próxima da superfície aquática e que existe um padrão sazonal de distribuição e abundância bem marcado. Estes aspectos parecem estar relacionados com o padrão migratório da espécie no Atlântico sul, incluindo a concentração da mesma ao largo da costa brasileira para fins reprodutivos, durante o verão austral.

L’habitat et l’écologie trophique des germons dans l’Atlantique Nord-Est sont étudiés par (1) analyse de données de captures par unité d’effort (CPUE) annuelles, (2) télémétrie ultrasonique et prospection acoustique, (3) analyse de contenus stomacaux et (4) mesures de leur adiposité. L’habitat vertical chez les individus les plus jeunes apparaît plus superficiel, et limité par la thermocline saisonnière chez les germons de 2 ans. Une importante variabilité géographique de l’alimentation est mise en évidence, et suggère une possible variabilité géographique du comportement alimentaire associé, ainsi que du budget énergétique des germons. La réplétion stomacale est plus élevée, et la capacité à accumuler de l’énergie plus faible et plus variable chez les individus les plus petits, ce qui suggère des besoins énergétiques plus importants chez ces individus. Ces résultats ont des implications de trois ordres concernant l’exploitation et l’évaluation de la population : - une variabilité de la capturabilité des germons de 2 ans, liée à la variabilité de leur habitat thermique vertical. Ceci peut entraîner une importante mortalité par pêche en période de capturabilité élevée, et introduire un biais dans l’évaluation du stock si les influences environnementales sur la capturabilité de ces germons n’est pas prise en compte. - une variabilité géographique de la capturabilité des germons par les ligneurs et les canneurs, liée à la variabilité géographique de leur comportement alimentaire, pouvant entraîner un biais dans la standardisation des CPUE. - une mortalité naturelle plus élevée chez les individus les plus jeunes, du fait de leurs restrictions physiologiques, et des dépenses énergétiques importantes associées à leur croissance et à ces restrictions<br>Habitat and trophic ecology of albacore (Thunnus alalunga) in the North-East Atlantic were studied through (1) the analysis of annual catch per unit of effort (CPUE), (2) sonic tracking and echosounding, (3) stomach content analysis and (4) fat content measurements. The vertical habitat of smaller individuals appears shallower, and limited by the seasonal thermocline in the case of age-2 albacore. An important geographical variability of the diet is shown, and suggests a possible geographical variability in the associated feeding behaviour. Stomach repletion appears higher, and ability to store energy lower and more variable in smaller individuals, which suggests higher energetic needs for these individuals. These results have implications on three aspects regarding the exploitation and assessment of the population: - a variability in the catchability of age-2 albacore, related to the variability of their thermal vertical habitat, can induce an important fishing mortality when their thermal habitat favours high catchabilty levels, and introduce a bias in the stock assessment if the environmental influences on catchability are not taken into account. - a geographical variability of albacore catchability by trolling and baitboat, related to the geographical variability of their feeding behaviour, could also introduce a bias in CPUE standardization. - a higher natural mortality in smaller individuals, due to important energetic needs related to their growth and to their physiological restrictions

Submitted by (edna.saturno@ufrpe.br) on 2017-02-22T16:09:14Z No. of bitstreams: 1 Vanessa Baptista Pedrosa.pdf: 733342 bytes, checksum: 553e5fd04a4d2eccb1338f8210bc81ba (MD5)<br>Made available in DSpace on 2017-02-22T16:09:14Z (GMT). No. of bitstreams: 1 Vanessa Baptista Pedrosa.pdf: 733342 bytes, checksum: 553e5fd04a4d2eccb1338f8210bc81ba (MD5) Previous issue date: 2011-06-28<br>Albacore is one of the main species of tuna caught in the South Atlantic for tuna Brazilian fishing vessel. Moreover, it has a little knownledge available about albacore biology in this portion of Atlantic Ocean, mainly regard to reproduction, aim of this study. Histological analysis of 735 gonads (370 males and 365 females)captured in the southwest atlantic were conducted during 2005 to 2010. Fork length of specimens ranged from 89 cm to 138 cm. Gonad index was determined monthly and observed the spawning activity from September to March. also, females exhibiting hydrated oocytes and post ovulatory follicles indicating an imminent spawning stage and post spawning, respectively.The sex ratio prior the reproductive period was 1:1 (males:females) with males mainly in the larger length classes (> 114 cm FL). At the first sexual maturity the length was 92 cm for females and 100 cm for males. The batch fecundity ranged from 0.5 to 1.2 million oocytes with approximately 3.700 oocytes/g. The oocyte diameter frequency showed a parceled spawning due to the occurrence of successives modes of unyolked oocytes, yolked and hydrated. These results contribute with information about the reproduction of the species in the South Atlantic both these life history parameters will allow to assess the albacore stock from this region.<br>A albacora branca é uma das principais espécies de atuns capturadas no Atlântico sul pela frota atuneira brasileira. Entretanto, pouco é conhecido sobre a biologia da espécie nesta parte do Atlântico, principalmente no que se refere à reprodução, objetivo do presente estudo. Análises histológicas das gônadas de 735 indivíduos de Thunnus alalunga (370 machos e 365 fêmeas) capturados no Atlântico Sudoeste foram realizadas no período de 2005 a 2010. O comprimento dos espécimes variou de 89 cm a 138 cm. Através do acompanhamento mensal do índice gonadal foi observada atividade de desova entre os meses de outubro a março, com fêmeas apresentando ovócitos hidratados e folículos pós-ovulatórios, indicando iminente estado de desova e pós-desova, respectivamente. A proporção sexual anterior ao período reprodutivo entre machos e fêmeas foi de 1:1, com os machos predominando nas maiores classes de comprimento (> 114 cm CF). O tamanho de primeira maturidade sexual determinado para as fêmeas foi de 92 cm e para os machos de 100 cm. A fecundidade variou de 0,5 a 1,2 milhões de ovócitos com cerca de 3.700 ovócitos/g. Pela freqüência do diâmetro dos ovócitos de fêmeas (37 - 1200 μm) foi verificada a desova do tipo parcelada devido a ocorrência de modas sucessivas de ovócitos avitelogênicos, vitelogênicos e hidratados. Esses resultados contribuem com informações sobre a reprodução da espécie no Atlântico Sul que junto com outros parâmetros do seu clico de vida permitirá avaliar o estoque dessa região.

One of the most sensitive life periods for each species is the first life stages (larval and juvenile). The survival rates of pelagic fish larvae in these phases are usually very low and subject to fluctuations, consequently affecting the recruitment of new generations. From historical Tuna landing data, the stock's abundance is fluctuating, especially for Atlantic Bluefin Tuna (ABT) (Thunnus thynnus, Linnaeus, 1758) Eastern stock. It is the largest Mediterranean Tuna and one of the most expensive species in the world. Some studies hypothesized that the fluctuations are dictated by environmental factors, particularly in the early life stages. Therefore, it appears necessary to better understand the reproductive biology, structure of the reproductive population, and the recruitment processes related to the environmental drivers of the Mediterranean Sea. In fact, it is a crucial area for maintaining ABT at a global level. It is essential for the other two species too, which share time and space during spawning in summer and their first life stages: ABT, Albacore Tuna (Thunnus alalunga, Bonnaterre, 1788), and Bullet Tuna (Auxis rochei, Risso, 1810). They carry out an essential ecological role as top predators, are fisheries targets globally, and have a fundamental influence on the structure and function of marine communities. Therefore, their sustainable management is essential and depends on a better understanding of the fish ecology, especially early life-history (LH) traits. Despite the Strait of Sicily (Central Mediterranean Sea) being an important spawning site for Tuna species, little is known about the relationship between the environmental variables and their larval spatial distribution in this area. Using historical larval collections from seven yearly surveys, in-situ environmental measurements, and satellite data, in this thesis, the interaction between ecological conditions and Tuna LH traits, horizontal distribution and spatial structure of the three Tuna species at the larval stage has been modelled. A multidisciplinary approach involving lagrangian simulations, species distribution modelling, and morphometric analysis has been used to verify the influence of environmental conditions on the distribution pattern of Tuna spawning and its effects on larval development and, consequently, on their survival probability. Finally, the potential impacts of the identified main driver have been investigated through forecasting models to determine the Tuna larval habitat patterns under possible future climate change scenarios. Understanding what influences the growth and survival of individuals among large pelagic fish populations, particularly during the larval stage, is crucial because these factors will eventually determine recruitment variability and the number of survivors that reach the adult stage. This work aims to improve knowledge of the growth and survival of Tuna larval stages, casting the complex system of the Central Mediterranean Sea in a new light. A site where upwelling, gyres, and fronts play a key role and observations could indicate a meta-population structure in Tuna populations. Chapter 1 provides an introduction with a background on the topic of study. Chapter 2 is a work published during my PhD candidate career. It is the basis for the characterization and knowledge of the central Mediterranean larval habitat. The abundance and presence-absence of larval specimens for the three Tuna species were modelled to examine their relationships with environmental factors. The results suggest that temperature, salinity, and day of the year are the key factors for understanding these species' ecological mechanisms and geographical distribution in this area. In Chapter 3, we look back in time and evaluate the conditions experienced by larvae, starting from their hatching to the point at which we found them. In this way, it was possible to better know the larval habitat and the spawning areas selected by the adults. We hypothesized that the environments experienced along the passive transport period would affect the development of these organisms. It seems helpful to describe not the difference in morphometric measurement but an early or late development. This work also highlighted different spatial patterns between the species. Finally, in Chapter 4, predictive models have been structured to model recruitment under different future climate change scenarios. Thanks to these models, it was possible to verify how the proportion of species could change. Despite the potential habitat seeming to expand, the abundances do not always follow the same trend. The results of this study can help manage future adult stocks and understand recruitment patterns under different future climate change scenarios. In fact, thermal sensitivity is a fundamental physiological attribute and one of the main reasons for induced changes in natural communities.<br>One of the most sensitive life periods for each species is the first life stages (larval and juvenile). The survival rates of pelagic fish larvae in these phases are usually very low and subject to fluctuations, consequently affecting the recruitment of new generations. From historical Tuna landing data, the stock's abundance is fluctuating, especially for Atlantic Bluefin Tuna (ABT) (Thunnus thynnus, Linnaeus, 1758) Eastern stock. It is the largest Mediterranean Tuna and one of the most expensive species in the world. Some studies hypothesized that the fluctuations are dictated by environmental factors, particularly in the early life stages. Therefore, it appears necessary to better understand the reproductive biology, structure of the reproductive population, and the recruitment processes related to the environmental drivers of the Mediterranean Sea. In fact, it is a crucial area for maintaining ABT at a global level. It is essential for the other two species too, which share time and space during spawning in summer and their first life stages: ABT, Albacore Tuna (Thunnus alalunga, Bonnaterre, 1788), and Bullet Tuna (Auxis rochei, Risso, 1810). They carry out an essential ecological role as top predators, are fisheries targets globally, and have a fundamental influence on the structure and function of marine communities. Therefore, their sustainable management is essential and depends on a better understanding of the fish ecology, especially early life-history (LH) traits. Despite the Strait of Sicily (Central Mediterranean Sea) being an important spawning site for Tuna species, little is known about the relationship between the environmental variables and their larval spatial distribution in this area. Using historical larval collections from seven yearly surveys, in-situ environmental measurements, and satellite data, in this thesis, the interaction between ecological conditions and Tuna LH traits, horizontal distribution and spatial structure of the three Tuna species at the larval stage has been modelled. A multidisciplinary approach involving lagrangian simulations, species distribution modelling, and morphometric analysis has been used to verify the influence of environmental conditions on the distribution pattern of Tuna spawning and its effects on larval development and, consequently, on their survival probability. Finally, the potential impacts of the identified main driver have been investigated through forecasting models to determine the Tuna larval habitat patterns under possible future climate change scenarios. Understanding what influences the growth and survival of individuals among large pelagic fish populations, particularly during the larval stage, is crucial because these factors will eventually determine recruitment variability and the number of survivors that reach the adult stage. This work aims to improve knowledge of the growth and survival of Tuna larval stages, casting the complex system of the Central Mediterranean Sea in a new light. A site where upwelling, gyres, and fronts play a key role and observations could indicate a meta-population structure in Tuna populations. Chapter 1 provides an introduction with a background on the topic of study. Chapter 2 is a work published during my PhD candidate career. It is the basis for the characterization and knowledge of the central Mediterranean larval habitat. The abundance and presence-absence of larval specimens for the three Tuna species were modelled to examine their relationships with environmental factors. The results suggest that temperature, salinity, and day of the year are the key factors for understanding these species' ecological mechanisms and geographical distribution in this area. In Chapter 3, we look back in time and evaluate the conditions experienced by larvae, starting from their hatching to the point at which we found them. In this way, it was possible to better know the larval habitat and the spawning areas selected by the adults. We hypothesized that the environments experienced along the passive transport period would affect the development of these organisms. It seems helpful to describe not the difference in morphometric measurement but an early or late development. This work also highlighted different spatial patterns between the species. Finally, in Chapter 4, predictive models have been structured to model recruitment under different future climate change scenarios. Thanks to these models, it was possible to verify how the proportion of species could change. Despite the potential habitat seeming to expand, the abundances do not always follow the same trend. The results of this study can help manage future adult stocks and understand recruitment patterns under different future climate change scenarios. In fact, thermal sensitivity is a fundamental physiological attribute and one of the main reasons for induced changes in natural communities.

The purpose of this study is to identify the intrinsic and extrinsic quality characteristics of West Coast albacore tuna (Thunnus alalunga). Albacore tuna were troll caught off the Oregon coast and transferred to the Oregon State University Seafood laboratory in Astoria, Oregon. Core samples were extracted from six designated body zones of 16 fish and analyzed for lipid, moisture, protein, ash, and fatty acid distribution. Proximate distribution was constant throughout the body zones. Protein and ash made up 25% of the composition, lipid and moisture made up the remaining 75%. The lipid content ranged from 3.9 ± 0.2 to 36.3 ± 1.1%, with a distribution of higher lipid towards the head and lower lipid towards the tail. Total omega-3 content averaged 40% of the identified fatty acids for each body zone, with omega-3 (g/100g tissue) ranging from 2.1 ± 0.5 to 3.5 ± 0.4. Furthermore, an inverse correlation (R²= -0.95) was found for lipid and moisture content, enabling a faster estimate of lipid content derived from moisture content. Onboard handling techniques for West Coast albacore tuna were evaluated using sensory and analytical methods. Chilling (immediately and after 3 h), spiking, and bleeding at the throat and gills were evaluated by a sensory panel for overall quality, color, smell, texture and flavor. 2-Thiobarbituric acid-reactive substances (TEARS) and pH were also compared. Rapid chilling significantly and positively influenced overall quality, color, texture, and flavor; and significantly reduced oxidative rancidity. Bleeding at the throat significantly and positively influenced all sensory attributes tested, but did not significantly influence TEARS or pH. Neither spiking nor bleeding at the gills significantly affected sensory attributes.<br>Graduation date: 2003

碩士<br>國立高雄海洋科技大學<br>漁業生產與管理研究所<br>96<br>This study is aiming to investigate the age and growth of Indian albacore tuna, based on length frequency analyses and otoliths reading methods. The historic length data and catch statistics of the Indian albacore were kindly made available by the Overseas Fisheries Development Council (OFDC). Owing to the apparent peaks in the length frequency distributions for the year of 1980-1983, the length data of this time period were adopted to estimate the age and growth of Indian albacore. These data were debugged, summed up and expanded to the total albacore catch in numbers. The MULTIFAN program was applied to estimate the von Bertalanffy’s growth equation, and the k and L∞ were then obtained as 0.157yr-1 and 144 cm, respectively. In addition, 54 otolith samples of albacore were provided by the observers worked on board. The otoliths were then examined under microscope after preliminary treatments, such as cleaning, embedding, and grinding. Some of these otoliths were difficult to be identified their rings, and only 34 of them were carried on the ring-count procedures. Each of these otoliths was examined two times independently, and the APE was calculated as 4.58%. For those ring-count were different between two readings, their otoliths were examined for the third time. However, ring-count of 30 otoliths were finally confirmed. Based on the length of the fish and their ring-count on otoliths, the mean lengths of albacore at age of 4-13 were obtained, respectively. These estimated lengths at age were found to be smaller than the von Bertalanffy’s growth equation derived from the length frequency analyses.