|
| ||
|
|
||
Bluefin Tuna (bluefin + tuna)
Kinds of Bluefin Tuna Selected AbstractsFeeding habits and trophic levels of bluefin tuna Thunnus thynnus of different size classes in the Mediterranean SeaJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2007G. Sarà Summary Possible changes in diet and trophic levels in relation to size of Mediterranean bluefin tuna, Thunnus thynnus, were investigated using labelled carbon (,13C) and nitrogen (,15N) stable isotopes. Samples were obtained from two locations in the southern Tyrrhenian Sea (Western Mediterranean Sea) in May and October 2004. The ,13C and ,15N analyses revealed at least three significant isotopic groups [small juveniles (0.7,2.2 kg), sub-adults (15,50 kg) and adults (70 to 225 kg)]. ,13C was negatively dependent on weight, while ,15N was positively dependent on weight [TW = 8.2 (±0.16) + 0.03 (± 0.0) *,15N (n = 49; r = 0.91; P < 0.001)]. Different prey contribution to the diet was highlighted for each class. The diet of juveniles comprised zooplankton, small pelagic fish and some coastal fish; sub-adults relied on medium pelagic fish, shrimps and cephalopods, and adults relied mainly on cephalopods and larger fish. The trophic level (TL) of tunas belonging to each size class was closely correlated to weight, starting from ca 3.0 TL for Group I and reaching 4.4,4.8 TL for the giants. Bluefin tuna, from small juveniles to giants, showed a shift in feeding preferences due to different use of habitats and food items as a function of the life stage. [source] Pricing U.S. North Atlantic bluefin tuna and implications for managementAGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 2 2001Michael T. Carroll Bluefin tuna is regarded as a high-quality product in the Japanese market and is characterized by an unusual marketing system by seafood industry standards. Each fish is individually inspected for various quality attributes before being flown to Japan for the fresh tuna market. The first objective of this study is to formally evaluate the degree to which the price of U.S. fresh bluefin tuna is determined by quality attributes of each fish, rather than by just the quantity supplied. This is accomplished using a Hedonic model. The results support the hypothesis that the fresh bluefin tuna price is, in fact, significantly influenced by the quality attributes of the fish, including the freshness, fat content, color, and shape. Interesting implications for public management of this highly valued resource arise from the results. [Econ-Lit citation: L150, L190, L660] © 2001 John Wiley & Sons, Inc. [source] Near real-time spatial management based on habitat predictions for a longline bycatch speciesFISHERIES MANAGEMENT & ECOLOGY, Issue 6 2006A. J. HOBDAY Abstract, Southern bluefin tuna (SBT), Thunnus maccoyii (Castelnau), is a quota-managed species that makes annual winter migrations to the Tasman Sea off south-eastern Australia. During this period it interacts with a year-round tropical tuna longline fishery (Eastern Tuna and Billfish Fishery, ETBF). ETBF managers seek to minimise the bycatch of SBT by commercial ETBF longline fishers with limited or no SBT quota through spatial restrictions. Access to areas where SBT are believed to be present is restricted to fishers holding SBT quota. A temperature-based SBT habitat model was developed to provide managers with an estimate of tuna distribution upon which to base their decisions about placement of management boundaries. Adult SBT temperature preferences were determined using pop-up satellite archival tags. The near real-time predicted location of SBT was determined by matching temperature preferences to satellite sea surface temperature data and vertical temperature data from an oceanographic model. Regular reports detailing the location of temperature-based SBT habitat were produced during the period of the ETBF fishing season when interactions with SBT occur. The SBT habitat model included: (i) predictions based on the current vertical structure of the ocean; (ii) seasonally adjusted temperature preference data for the 60 calendar days centred on the prediction date; and (iii) development of a temperature-based SBT habitat climatology that allowed visualisation of the expected change in the distribution of the SBT habitat zones throughout the season. At the conclusion of the fishing season an automated method for placing management boundaries was compared with the subjective approach used by managers. Applying this automated procedure to the habitat predictions enabled an investigation of the effects of setting management boundaries using old data and updating management boundaries infrequently. Direct comparison with the management boundaries allowed an evaluation of the efficiency and biases produced by this aspect of the fishery management process. Near real-time fishery management continues to be a realistic prospect that new scientific approaches using novel tools can support and advance. [source] Plasticity in vertical behaviour of migrating juvenile southern bluefin tuna (Thunnus maccoyii) in relation to oceanography of the south Indian OceanFISHERIES OCEANOGRAPHY, Issue 4 2009SOPHIE BESTLEY Abstract Electronic tagging provides unprecedented information on the habitat use and behaviour of highly migratory marine predators, but few analyses have developed quantitative links between animal behaviour and their oceanographic context. In this paper we use archival tag data from juvenile southern bluefin tuna (Thunnus maccoyii, SBT) to (i) develop a novel approach characterising the oceanographic habitats used throughout an annual migration cycle on the basis of water column structure (i.e., temperature-at-depth data from tags), and (ii) model how the vertical behaviour of SBT altered in relation to habitat type and other factors. Using this approach, we identified eight habitat types occupied by juvenile SBT between the southern margin of the subtropical gyre and the northern edge of the Subantarctic Front in the south Indian Ocean. Although a high degree of variability was evident both within and between fish, mixed-effect models identified consistent behavioural responses to habitat, lunar phase, migration status and diel period. Our results indicate SBT do not act to maintain preferred depth or temperature ranges, but rather show highly plastic behaviours in response to changes in their environment. This plasticity is discussed in terms of the potential proximate causes (physiological, ecological) and with reference to the challenges posed for habitat-based standardisation of fishery data used in stock assessments. [source] Movement and behaviour of large southern bluefin tuna (Thunnus maccoyii) in the Australian region determined using pop-up satellite archival tagsFISHERIES OCEANOGRAPHY, Issue 5 2008TOBY A. PATTERSON Abstract Pop-up satellite archival tags (PSATs) were deployed on 52 large (156,200 cm length to caudal fork) southern bluefin tuna (Thunnus maccoyii) in the western Tasman Sea during the austral winters of 2001,2005. Southern bluefin tuna (SBT) were resident in the Tasman Sea for up to 6 months with movements away from the tagging area occurring at highly variable rates. The data indicated a general tendency for SBT to move south from the tagging area in the Western Tasman Sea. Four individuals migrated west along the southern continental margin of Australia and into the Indian Ocean. Three individuals moved east into the central Tasman Sea, with one individual reaching New Zealand. We also describe the first observed migration of an SBT from the Tasman Sea to the Indian Ocean spawning grounds south of Indonesia. Individuals spent most of their time relatively close to the Australian coast, with an estimated 84% of time spent in the Australian Fishing Zone. SBT favored temperatures between 19 and 21°C, adjusting their depth to the vertical temperature distribution. Distinct diurnal diving patterns were observed and adjustment of depth to maintain constant ambient light levels over a 24-h period. The findings of this study are a significant advance toward greater understanding of the spatial dynamics of large SBT and understanding the connectivity between distant regions of their distribution. [source] Horizontal and vertical movements of juvenile bluefin tuna (Thunnus orientalis) in relation to seasons and oceanographic conditions in the eastern Pacific OceanFISHERIES OCEANOGRAPHY, Issue 5 2007TAKASHI KITAGAWA Abstract Electronically tagged juvenile Pacific bluefin, Thunnus orientalis, were released off Baja California in the summer of 2002. Time-series data were analyzed for 18 fish that provided a record of 380 ± 120 days (mean ± SD) of ambient water and peritoneal cavity temperatures at 120 s intervals. Geolocations of tagged fish were estimated based on light-based longitude and sea surface temperature-based latitude algorithms. The horizontal and vertical movement patterns of Pacific bluefin were examined in relation to oceanographic conditions and the occurrence of feeding events inferred from thermal fluctuations in the peritoneal cavity. In summer, fish were located primarily in the Southern California Bight and over the continental shelf of Baja California, where juvenile Pacific bluefin use the top of the water column, undertaking occasional, brief forays to depths below the thermocline. In autumn, bluefin migrated north to the waters off the Central California coast when thermal fronts form as the result of weakened equatorward wind stress. An examination of ambient and peritoneal temperatures revealed that bluefin tuna fed during this period along the frontal boundaries. In mid-winter, the bluefin returned to the Southern California Bight possibly because of strong downwelling and depletion of prey species off the Central California waters. The elevation of the mean peritoneal cavity temperature above the mean ambient water temperature increased as ambient water temperature decreased. The ability of juvenile bluefin tuna to maintain a thermal excess of 10°C occurred at ambient temperatures of 11,14°C when the fish were off the Central California coast. This suggests that the bluefin maintain peritoneal temperature by increasing heat conservation and possibly by increasing internal heat production when in cooler waters. For all of the Pacific bluefin tuna, there was a significant correlation between their mean nighttime depth and the visible disk area of the moon. [source] Carrying capacity and survival strategy for the Pacific bluefin tuna, Thunnus orientalis, in the Western PacificFISHERIES OCEANOGRAPHY, Issue 2 2006YASUO MATSUKAWA Abstract The carrying capacity for the Pacific bluefin tuna at each life stage is estimated and its survival strategy is examined numerically, using a new method to define the hypothetical capacity, the standard population, and the search volumes that are necessary and are feasible for the tuna. The carrying capacity for the adult is estimated at 1,2 × 106 individuals, which corresponds with 5,10% of the hypothetical capacity and is comparable with the maximum levels of the southern and the Atlantic bluefin tuna populations. It is hypothesized semiquantitatively that the migration at each life stage and the remarkable decrement of growth at 120 days and about 40 cm occur as an evolutionary response to population excess over the carrying capacity. It is also hypothesized semiquantitatively that the early larvae have minimal food available in the Subtropical Water and develop the predatory morphology, high growth rate, and high mobility, however, at the expense of a high mortality as an evolutionary response to the tuna spawning in the Subtropical Water. This method may be an available tool to not only investigate the carrying capacity and survival strategy of a specific fish species, but also predict when and in how much abundance the fish species occurs in a specific area of its habitat. [source] Diving behavior of immature, feeding Pacific bluefin tuna (Thunnus thynnus orientalis) in relation to season and area: the East China Sea and the Kuroshio,Oyashio transition regionFISHERIES OCEANOGRAPHY, Issue 3 2004Takashi Kitagawa Abstract Twenty-four archival tags were recovered from Pacific bluefin tuna previously released off Tsushima Island in the East China Sea. By analysis of the time-series data of the pressure and the ambient and internal temperature from the 24 tags, we examined the relationship between the tuna's pattern of diving and the thermocline depth. In the East China Sea, diving and feeding events occurred throughout almost the entire day in both winter and summer, suggesting that the purpose of diving is for feeding. In summer, the feeding frequency was greater than that in winter, which corresponds to the fact that growth is more rapid in summer than in winter. During summer in the Kuroshio,Oyashio transition region, on the other hand, feeding events were much more frequent than those in the East China Sea, in spite of a lower diving frequency. The mean horizontal distance traveled was also significantly higher and it seems that in this area they may move horizontally to feed on prey accumulated at the surface. We conclude that, in addition to the ambient temperature structure, the vertical and horizontal distribution of prey species plays an important role in the feeding behavior of Pacific bluefin tuna. One bluefin tuna migrated to the Oyashio frontal area, where both the horizontal and the vertical thermal gradients are much steeper. The fish spent most of the time on the warmer side of the front and often traveled horizontally to the colder side during the day, perhaps to feed. This implies that there is a thermal barrier effect, in this case from the Oyashio front, on their behavior. The frequency of feeding events was low, although all the monitored fish dived every dawn and dusk, irrespective of the seasons or location. It is possible that these twice-daily diving patterns occurred in response to the change in ambient light at sunrise and sunset. [source] Identification of Atlantic bluefin tuna (Thunnus thynnus) stocks from putative nurseries using otolith chemistryFISHERIES OCEANOGRAPHY, Issue 2 2003Jay R. Rooker Abstract Chemical signatures in the otoliths of teleost fishes represent natural tags that may reflect differences in the chemical and physical characteristics of an individuals' environment. Otolith chemistry of Atlantic bluefin tuna (Thunnus thynnus) was quantified to assess the feasibility of using these natural tags to discriminate juveniles (age 0 and age 1) from putative nurseries. A suite of six elements (Li, Mg, Ca, Mn, Sr and Ba) was measured in whole otoliths using solution-based inductively coupled plasma mass spectrometry. Otolith chemistry of age-1 T. thynnus collected from the two primary nurseries in the Mediterranean Sea and western Atlantic Ocean differed significantly, with a cross-validated classification accuracy of 85%. Spatial and temporal variation in otolith chemistry was evaluated for age-0 T. thynnus collected from three nurseries within the Mediterranean Sea: Alboran Sea (Spain), Ligurian Sea (northern Italy), and Tyrrhenian Sea (southern Italy). Distinct differences in otolith chemistry were detected among Mediterranean nurseries and classification accuracies ranged from 62 to 80%. Interannual trends in otolith chemistry were observed between year classes of age-0 T. thynnus in the Alboran Sea; however, no differences were detected between year classes in the Tyrrhenian Sea. Age-0 and age-1 T. thynnus collected from the same region (Ligurian Sea) were also compared and distinct differences in otolith chemistry were observed, indicating ontogenetic shifts in habitat or elemental discrimination. Findings suggest that otolith chemistry of juvenile T. thynnus from different nurseries are distinct and chemical signatures show some degree of temporal persistence, indicating the technique has considerable potential for use in future assessments of population connectivity and stock structure of T. thynnus. [source] Schooling and migration of large pelagic fishes relative to environmental cuesFISHERIES OCEANOGRAPHY, Issue 2 2000Robert Humston A kinesis model driven by high-resolution sea surface temperature maps is used to simulate Atlantic bluefin tuna movements in the Gulf of Maine during summer months. Simulations showed that individuals concentrated in areas of thermal preference. Results are compared to empirical distribution maps of bluefin tuna schools determined from aerial overflights of the stock during the same time periods. Simulations and empirical observations showed similar bluefin tuna distributions along fronts, although interannual variations in temperature ranges occupied suggest that additional foraging factors are involved. Performance of the model is further tested by simulating the relatively large-scale annual north,south migrations of bluefin tuna that followed a preferred thermal regime. Despite the model's relatively simple structure, results suggest that kinesis is an effective mechanism for describing movements of large pelagic fish in the expansive ocean environment. [source] Feeding ecology of wild migratory tunas revealed by archival tag records of visceral warmingJOURNAL OF ANIMAL ECOLOGY, Issue 6 2008Sophie Bestley Summary 1Seasonal long-distance migrations are often expected to be related to resource distribution, and foraging theory predicts that animals should spend more time in areas with relatively richer resources. Yet for highly migratory marine species, data on feeding success are difficult to obtain. We analysed the temporal feeding patterns of wild juvenile southern bluefin tuna from visceral warming patterns recorded by archival tags implanted within the body cavity. 2Data collected during 1998,2000 totalled 6221 days, with individual time series (n = 19) varying from 141 to 496 days. These data span an annual migration circuit including a coastal summer residency within Australian waters and subsequent migration into the temperate south Indian Ocean. 3Individual fish recommenced feeding between 5 and 38 days after tagging, and feeding events (n = 5194) were subsequently identified on 76·3 ± 5·8% of days giving a mean estimated daily intake of 0·75 ± 0·05 kg. 4The number of feeding events varied significantly with time of day with the greatest number occurring around dawn (58·2 ± 8·0%). Night feeding, although rare (5·7 ± 1·3%), was linked to the full moon quarter. Southern bluefin tuna foraged in ambient water temperatures ranging from 4·9 °C to 22·9 °C and depths ranging from the surface to 672 m, with different targeting strategies evident between seasons. 5No clear relationship was found between feeding success and time spent within an area. This was primarily due to high individual variability, with both positive and negative relationships observed at all spatial scales examined (grid ranges of 2 × 2° to 10 × 10°). Assuming feeding success is proportional to forage density, our data do not support the hypothesis that these predators concentrate their activity in areas of higher resource availability. 6Multiple-day fasting periods were recorded by most individuals. The majority of these (87·8%) occurred during periods of apparent residency within warmer waters (sea surface temperature > 15 °C) at the northern edge of the observed migratory range. These previously undocumented nonfeeding periods may indicate alternative motivations for residency. 7Our results demonstrate the importance of obtaining information on feeding when interpreting habitat utilization from individual animal tracks. [source] Type and ultrastructure of Didymocystis wedli and Koellikerioides intestinalis (Digenea, Didymozoidae) cysts in captive Atlantic bluefin tuna (Thunnus thynnus Linnaeus, 1758)JOURNAL OF APPLIED ICHTHYOLOGY, Issue 6 2009I. Mladineo Summary Tissue encapsulation, one of the most common tissue reactions to invading parasites, is the hallmark sign of didymozoid (Digenea, Didymozoidae) infections in fish. Investigated were the types of intermediate filaments and ultrastructure of the connective tissue capsule elicited by the presence of didymozoids in the gills and intestine of Atlantic bluefin tuna (Thunnus thynnus Linnaeus, 1758). The evaluation was done performing TEM microscopy of two tissue-embedded didymozoid species, along with monoclonal antibodies labeling (anti-fish collagen type I, anti-human cytokeratin, anti-vimentin antibodies). Ultrastructure of Didymocystis wedli (Ariola, 1902) (prevalence = 61.75%, abundance = 28.91) encapsulated in gill filaments and Koellikerioides intestinalis (Yamaguti, 1970) (prevalence = 54.65%, abundance = 10.96) in the intestinal submucosa showed that the thin parasitic hindbody tegumentum was directly embedded in layers of connective tissue bands. Only a few cellular elements (lymphocytes, fibroblasts and fibrocytes) infiltrated the connective tissue capsule, which differed between the two didymozoid species in thickness, not in the type of filaments expressed. Cysts showed positive reaction to extracellular collagen as well as appearing positive for the cytoskeletal intermediate filaments vimentin and cytokeratin. [source] Feeding habits and trophic levels of bluefin tuna Thunnus thynnus of different size classes in the Mediterranean SeaJOURNAL OF APPLIED ICHTHYOLOGY, Issue 2 2007G. Sarà Summary Possible changes in diet and trophic levels in relation to size of Mediterranean bluefin tuna, Thunnus thynnus, were investigated using labelled carbon (,13C) and nitrogen (,15N) stable isotopes. Samples were obtained from two locations in the southern Tyrrhenian Sea (Western Mediterranean Sea) in May and October 2004. The ,13C and ,15N analyses revealed at least three significant isotopic groups [small juveniles (0.7,2.2 kg), sub-adults (15,50 kg) and adults (70 to 225 kg)]. ,13C was negatively dependent on weight, while ,15N was positively dependent on weight [TW = 8.2 (±0.16) + 0.03 (± 0.0) *,15N (n = 49; r = 0.91; P < 0.001)]. Different prey contribution to the diet was highlighted for each class. The diet of juveniles comprised zooplankton, small pelagic fish and some coastal fish; sub-adults relied on medium pelagic fish, shrimps and cephalopods, and adults relied mainly on cephalopods and larger fish. The trophic level (TL) of tunas belonging to each size class was closely correlated to weight, starting from ca 3.0 TL for Group I and reaching 4.4,4.8 TL for the giants. Bluefin tuna, from small juveniles to giants, showed a shift in feeding preferences due to different use of habitats and food items as a function of the life stage. [source] Further evidence of spawning of bluefin tuna (Thunnus thynnus L., 1758) and the tuna species (Auxis rochei Ris., 1810, Euthynnus alletteratus Raf., 1810) in the eastern Mediterranean Sea: preliminary results of TUNALEV larval survey in 2004JOURNAL OF APPLIED ICHTHYOLOGY, Issue 3 2005I. K. Oray Summary A tuna larval survey (TUNALEV) in the Northern Levantine Basin (Cilician Basin) was conducted onboard a trawler from 5 to 18 June 2004. To determine the spatial distribution and abundance of tuna larvae, Bongo 60 and Bongo 90 nets were used. Ichtyoplankton samples from 104 stations were taken. In total, 121 bluefin tuna (Thunnus thynnus), 94 bullet tuna (Auxis rochei) and 22 Atlantic black skipjack (Euthynnus alletteratus) larvae were collected. In comparison with the other tuna larvae, the concentration of bluefin tuna larvae was highest in the Bay of Mersin. The collected larvae in this area were composed mainly of 5,9 mm size specimens. [source] Diet of young-of-the-year bluefin tuna, Thunnus thynnus (Linnaeus, 1758), in the southern Tyrrhenian (Mediterranean) SeaJOURNAL OF APPLIED ICHTHYOLOGY, Issue 4 2004M. Sinopoli Summary The diet of juvenile bluefin tuna (Thunnus thynnus) caught 2 to 8 miles off NE Sicily was investigated in order to improve knowledge of the species' early life history. From 1998 to 2000, 107 specimens ranging from 63 to 495 mm (total length) were fished between July and November. Fishes were caught by trolling line or purse seine in a Fish Aggregating Devices (FADs) area 2 to 8 miles offshore and as by-catch of the purse-seine sardine fishery 2 to 4 miles offshore. Most frequently found items in the T. thynnus stomachs were fishes (84.5%), crustaceans (54.6%) and cephalopods (50.5%). The largest contribution in weight was provided by cephalopods (47.3%) and fishes (46.5%), while the most abundant items were fishes (51%), cephalopods (27.2%) and crustaceans (21.1%). These results suggest that young-of-the-year tuna have an essentially piscivorous diet, although invertebrate prey provide a substantial contribution to the food array. Prey show little relationship with FADs, although one prey species (blue runner, Caranx crysos) is associated with FADs in the Mediterranean. [source] Structure of the inner ear of bluefin tuna Thunnus thynnusJOURNAL OF FISH BIOLOGY, Issue 6 2006J. Song The ears of five large bluefin tuna Thunnus thynnus were examined by light and scanning electron microscopy (SEM). The gross structure of the ear is similar to that in other fishes. The ears, however, appear to be held more rigidly in place than in other species through the presence of an extensive connective tissue between the membranous ear and the surrounding bone. Moreover, unlike other fishes, the semicircular canals and otolithic end organs have thick cartilaginous walls and there is a dense matrix surrounding the otoliths rather than a more watery fluid found in other species. SEM revealed that the saccular epithelium has a ,standard' hair cell orientation pattern. The hair cell orientation patterns in the lagena and utricle resemble those found in most other fishes. Ciliary bundle density and length vary in different epithelial regions and each ear had >2 × 106 sensory cells. The morphological results support the hypothesis that bluefin tuna probably do not detect sounds to much over 1000 Hz (if that high) and that only very loud anthropogenic sounds have the potential to affect hearing in this species. [source] Mitochondrial DNA sequence variation within and between tuna Thunnus species and its application to species identificationJOURNAL OF FISH BIOLOGY, Issue 6 2001H. Takeyama Restriction analysis detected two types of bigeye tuna (, and ,); the , type was in the majority in the Atlantic but nearly absent in the Indo-Pacific. The , type shared a larger number of restriction sites with other species than the conspecific , type, but bigeye-specific nucleotide substitutions with a novel diagnostic restriction profile were found. Although the nucleotide sequence difference between Atlantic and Pacific sub-species of the northern bluefin tuna was nearly the largest among species, individuals possessing the Atlantic type of mtDNA were found at very low frequency in the Pacific and vice versa. Previous RFLP markers were found to be diagnostic for the other five species (albacore, blackfin, longtail, southern bluefin and yellowfin tunas). Genetic information is provided to discriminate all Thunnus species regardless of their origin and to identify the ocean of capture in the northern bluefin and bigeye tunas. [source] Pan-steatitis in farmed northern bluefin tuna, Thunnus thynnus (L.), in the eastern AdriaticJOURNAL OF FISH DISEASES, Issue 2 2008R J Roberts Abstract Clinical, gross and histopathological investigations were carried out into large-scale mortalities on eastern Mediterranean bluefin tuna, Thunnus thynnus (L.), farms. Fish showed only nervous signs and darkened colour. At post-mortem the liver was bronze coloured and the pyloric area waxy in consistency. There was no evidence of any other gross pathology. Histopathology showed severe hepatic necrosis and lipidosis. Peri-pancreatic lipoid tissue was heavily infiltrated with an inflammatory round cell infiltrate. Fish on all three farms had been fed on a North African pilchard diet rather than traditional local or Baltic species. Once the diet was modified, losses ceased. A diagnosis of pan-steatitis as seen in other farmed fish species, as well as in terrestrial animals, on particular fish-based diets was made, although the actual factor within the diet which induced the inflammatory effect is not known. [source] Pricing U.S. North Atlantic bluefin tuna and implications for managementAGRIBUSINESS : AN INTERNATIONAL JOURNAL, Issue 2 2001Michael T. Carroll Bluefin tuna is regarded as a high-quality product in the Japanese market and is characterized by an unusual marketing system by seafood industry standards. Each fish is individually inspected for various quality attributes before being flown to Japan for the fresh tuna market. The first objective of this study is to formally evaluate the degree to which the price of U.S. fresh bluefin tuna is determined by quality attributes of each fish, rather than by just the quantity supplied. This is accomplished using a Hedonic model. The results support the hypothesis that the fresh bluefin tuna price is, in fact, significantly influenced by the quality attributes of the fish, including the freshness, fat content, color, and shape. Interesting implications for public management of this highly valued resource arise from the results. [Econ-Lit citation: L150, L190, L660] © 2001 John Wiley & Sons, Inc. [source] Mortality of Northern Bluefin Tuna Thunnus thynnus Due to Trauma Caused by Collision During Growout CultureJOURNAL OF THE WORLD AQUACULTURE SOCIETY, Issue 4 2000Shigeru Miyashita Collisions with the walls of tanks or nets caused mass mortality that occurs during growout. The period when collisions frequently occur and the types of injury caused by collision were examined in this study. Juveniles were reared in indoor tanks from 30 to 120 d after hatching, and in an open sea net cage from 42 to 150 d after hatching. Dead fish were collected and counted daily in both of the experiments. In the indoor experiment, the sampled fish were preserved in 10% formalin solution, and each of 10 specimens of about 30, 50, 70, 85, 100, 130, 160 and 225 mm in body length (BL) were examined using x-rays to detect injury of the bones. Juvenile and young adult bluefin tuna showed a reduction in numbers caused by collision with the tank or the net wall during the experiments. In the indoor tank, there were 1,200 fish on day 30 but only eight on day 120. The daily mortality increased from day 30 after hatching, when juveniles reached 50-mm BL and remained over 4%/d until day 60 when juveniles grew to 300-mm BL. The proportion of dead fish with injuries of bone, especially of the vertebral column and the parasphenoid, increased after fish reached 50-mm BL, and exceeded 60% in fish with BL 85 mm or greater. In the open sea net cage, there were 3,841 fish at the start of the experiment on day 42 and only 65 on day 150. In this experiment, the reduction was greatest from the start of the experiment until day 80, when fish grew to approximately 25 cm in total length. Significant bacterial, viral or parasitic diseases were not observed in these fish; the only findings were dislocations of the vertebral column and injuries to the upper and lower jaws. These results show that the loss of juvenile and young adult bluefin tuna was caused by collision with the tank or net wall that fatally damaged the bones of the vertebral columns and the parasphenoid. [source] A rapid latex agglutination test for gender identification in the Atlantic bluefin tuna, Thunnus thynnus (Linnaeus)AQUACULTURE RESEARCH, Issue 9 2010Elisabetta Micera Abstract A rapid, one-step agglutination assay has been developed, based on latex particles sensitized with antibodies against vitellogenin (Vtg), aimed at Atlantic bluefin tuna, Thunnus thynnus (Linnaeus) (ABFT), gender identification. The egg-yolk precursor protein Vtg was used as a gender marker for the assay as it is a female-specific protein synthesized during reproductive maturation. The presence of Vtg in the plasma was revealed in 60,120 s through an agglutination reaction by mixing small volumes of ABFT plasma and an anti-Vtg antibody-latex suspension on a microscope slide. The effectiveness of the present test was restricted to the months of May and June, concomitant with high circulating Vtg levels. Because of its rapidity and ease of performance in the field, the present gender identification assay could be useful for broodstock management in the aquaculture industry as well as in tagging studies on wild populations. [source] Changes in the proximate composition of bluefin tuna (Thunnus thynnus) reared in the cages located on the Gulf of Antalya (Turkey's Western Mediterranean coast) during the fattening periodAQUACULTURE RESEARCH, Issue 15 2009Pinar Yerl, kaya Abstract The aim of this study was to investigate the changes in the proximate composition of bluefin tuna (Thunnus thynnus) muscle reared in cages during the fattening period. Samples were taken from tunas at monthly intervals between July and October. Moisture, crude protein, crude fat and crude ash were analysed. The fat and ash contents increased, and the moisture content decreased during the fattening period. There were no significant differences in the protein content during this period. The mean protein concentration was 21% over this period. The highest levels of dry matter (40%), fat (15%) and ash (1.21%) were found in October. Baitfish (Sardina pilchardus, Sardinella aurita and Alosa fallax nilotica) were also analysed. There were no differences in the moisture, protein and fat contents between baitfish, but a lower ash content was found in sardine than in the others. The mean moisture, protein, fat and ash contents of baitfish were found to be 68.28%; 19.2%; 8.5%; and 1.4% respectively. [source] Changes in myoglobin content and proximate compositions of the dorsal ordinary muscles of full-cycle cultured Pacific bluefin tuna Thunnus orientalis (Temminck et Schlegel) with body sizeAQUACULTURE RESEARCH, Issue 2 2007Yasuyuki Tsukamasa Abstract We investigated the changes in myoglobin (Mb) content and proximate compositions of the cephalad parts of the dorsal ordinary muscles (Ce-DOM) of full-cycle cultured (FC) Pacific bluefin tuna [body length: 42.6,115.4 cm, body weight (BW): 1.7,38.4 kg, killed from July 2004 to October 2005]. The Mb content of Ce-DOM increased (P<0.01) until a BW of 7.0 kg was reached. However, the Mb content of Ce-DOM had a wide variety above a BW of 7.0 kg. On the other hand, the moisture, protein and ash contents of Ce-DOM of FC tuna decreased (P<0.05 and 0.01) with an increase in BW. However, the lipid content of Ce-DOM increased gradually above about a BW of 20.0 kg. Furthermore, the Mb content in protein of the Ce-DOM of FC tuna increased with an increase in BW. These results indicated that the increase in Mb content of Ce-DOM of FC tuna was not related to changes in proximate composition between a BW of 1.7 and 38.4 kg. [source] Growth, food intake and feed conversion rates in captive Atlantic bluefin tuna (Thunnus thynnus Linnaeus, 1758) under fattening conditionsAQUACULTURE RESEARCH, Issue 6 2005Felipe Aguado-Giménez First page of article [source] Ontogeny of immune system organs in northern bluefin tuna (Thunnus orientalis, Temminck and Schlegel 1844)AQUACULTURE RESEARCH, Issue 1 2003M Watts Abstract Serial sections, prepared from 0.5 to 30 days posthatch (dph) larval and juvenile Thunnus orientalis (Temminck & Schlegel 1844), were stained with haematoxylin and eosin and examined by light microscopy for immune organ development. The early kidney was present at 0.5 dph, undifferentiated stem cells began to appear at 2 dph, and by 7 dph occasional small lymphocytes were present. The thymus was first obvious at 5 dph, located above the fourth branchial arch, small lymphocytes appeared at 7 dph, and by 15 dph an outer thymocytic zone and an inner epithelioid zone were visible. The progenitor spleen was present at 2 dph, located close to the gut, and by 12 dph it consisted of a mass of sinusoids filled with red blood cells, and remained mainly erythroid throughout the period studied. These results suggest that development of immune organs in this species is precocious relative to other marine teleosts. [source] | |||||||||||||