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1.
ABSTRACT:   Immature Pacific bluefin tuna Thunnus orientalis , tagged with archival tags, were released near Tsushima Island in the East China Sea during the winters of 1995 through 1998. Time-series data for ambient and peritoneal cavity temperatures, recorded every 128 or 256 s for 23 fish recovered, were analyzed. The objective of this study was to clarify the process of development of thermoconservation ability with growth in relation to adaptive mechanisms to cooler temperate waters. According to the results, mean ambient temperatures ranged from 14.9 to 20.7°C, which is almost within the optimum temperature range according to previous reports. Mean peritoneal temperatures were higher than ambient temperatures (19.7–27.3°C), but never reached 35°C, which would induce overheating. Although the mean thermal differences between peritoneal and ambient temperatures increased with body size, the rate of increase decreased with body size. A heat budget model suggests that as the insulation of the body develops, the estimated mean values of internal heat production decrease with body size. This is probably due to the allometric scale effect and explains why the thermal difference does not increase quickly with body size. It is likely that Pacific bluefin tuna inhabit cooler temperate waters in mid-latitude regions to avoid overheating.  相似文献   

2.
Archival tags were used to study the seasonal movements, migration patterns and vertical distribution of juvenile North Pacific albacore (Thunnus alalunga). Between 2001 and 2006, archival tags were deployed in North Pacific albacore in two regions of the Northeast Pacific: (i) off Northern Baja California, Mexico and Southern California, and (ii) off Washington and Oregon. Twenty archival tagged fish were recovered with times at liberty ranging from 63 to 697 days. Tagged albacore exhibited five distinct, seasonal migratory patterns. Depth and temperature data also showed a broad range of vertical behaviors. In certain regions such as off Baja California, Mexico, juvenile albacore make frequent dives to depths exceeding 200 m during the day and remain in the surface mixed layer at night, whereas off Oregon and Washington they remain near the surface both day and night. Water temperatures encountered ranged from 3.3 to 22.7°C. Peritoneal temperatures were significantly higher by an average of approximately 4°C, as expected in these warm‐bodied fish. This study provides a comprehensive examination of horizontal and vertical movements of juvenile albacore in the Northeast Pacific. The results reveal diverse behavior that varies regionally and seasonally as albacore move among different habitats throughout the entire North Pacific.  相似文献   

3.
The arrival of the warm tropical Leeuwin Current (LC) into southern Western Australia (SWA) may influence the movement timing and foraging habitat of juvenile southern bluefin tuna (SBT). Seasonal and interannual changes in the strength of the LC lead to thermal differences and potential changes in food availability between tropical and temperate waters in SWA. This phenomenon could influence the habitat utilization of SBT in these summer grounds. Movement characteristics determined from SBT tagged with acoustic transmitters (N = 244) using cross‐shelf lines of automated receivers for three summer‐autumn seasons (2004/2005, 2005/2006, 2006/2007) in SWA revealed interannual variability. Each year, the eastward movements of tagged fish increased as temperatures increased, and fish left the region when temperatures exceeded 20.0°C, a temperature indicative of the leading edge of the LC in SWA waters. Interannual fluctuations in the timing of movements were detected. When the LC was narrow and restricted to the shelf edge in 2004/2005, the distribution of SBT in shelf waters did not change before or after LC intrusion. In contrast, long distance eastward movements frequently occurred when the LC intrusion was spread wide over the continental shelf in 2005/2006 and 2006/2007. This suggests that, off SWA, juvenile SBT move quickly out of local foraging habitats defined by cool sub‐tropical temperate waters ahead of the tropical LC intrusion, despite these waters not being physiologically limiting. These results suggest that the behavioural response of SBT may be related to changes in prey availability as a result of changes in oceanographic conditions.  相似文献   

4.
Young Pacific bluefin tuna Thunnus orientalis with archival tags were released in the East China Sea. Time-series data for depth, and ambient and peritoneal temperatures for nine fish, recorded every 128 s, were analyzed. Our objectives were to describe monthly changes in diving patterns in relation to the ambient thermal structure and the occurrence of feeding events during March–June, and to discuss possible reasons why bluefin tuna repeatedly dived to depths below the thermocline in terms of their thermoconservation mechanisms. It was found that the fish repeatedly dived through the thermocline at intervals of 1.2 h on average, and the dive frequency was high during March–May. However, the dive frequency and periodicity decreased in June, when the gradient became steeper. In contrast, feeding events increased in June. These results indicate that from March to May, bluefin tuna repeatedly dive because food biomass is inadequate at the surface, and they stop undertaking repeated dives in June when food becomes more readily available at the surface, in addition to low visibility caused by low solar radiation. Further, the range of heat transfer times for these fish was so long that their peritoneal temperature was probably maintained by engaging in brief dives. The periodicity of dives may lead to a lower fluctuation in the peritoneal temperature, suggesting that the dives are a kind of behavioral thermoregulation.  相似文献   

5.
ABSTRACT:   Mid-water trawl surveys were conducted from late August to late September in 1999 and 2004 in order to investigate the distribution pattern, hatch date, and growth of juvenile Pacific bluefin tuna Thunnus orientalis in the Sea of Japan. Juveniles were collected at the stations where ambient water temperature (mean water temperature from surface to 30 m deep, WT0−30) was 23.4–25.9°C, and most of them were found in waters where WT0−30 was higher than 24°C. Sampled juveniles ranged 108–280 mm fork length. Based on otolith analysis, they were estimated to grow to approximately 180 and 250 mm at 60 and 90 days old, respectively, and showed similar growth to that of Atlantic bluefin tuna in the Mediterranean Sea. The back-calculated hatch date of the samples was mostly in July and most juveniles spawned in the Sea of Japan.  相似文献   

6.
Bluefin tuna maintain a higher body temperature than ambient sea water. Body heat is derived mainly from metabolic heat to elevate and maintain regional body temperature that is higher than the ambient, while heat loss is caused by heat transfer throughout the whole body surface and gills. Retention of high body temperature is thought to differ at each growth stage, so that a larger body mass maintains a higher body temperature. We evaluated the whole-body heat transfer coefficient, thermal difference between each tissue and water temperature, and metabolic heat in tissues during swimming of juvenile bluefin tuna as a function of fork length (FL) using a small thermometer and a treadmill-type flow tank. A system for maintaining high body temperature was well developed in fish with FL greater than 20.0 cm. Whole-body heat transfer coefficient was fitted to a −0.695 power of mass. Juvenile bluefin tuna showed a transition speed of 3.0 FL/s at which they switched from aerobic to anaerobic motion.  相似文献   

7.
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.  相似文献   

8.
Thirteen adult bluefin tuna were tracked with electronic pop‐up satellite tags during their reproductive migration towards Mediterranean spawning grounds as they entered the Strait of Gibraltar. Fish were caught in tuna traps and tagged either underwater, with the aid of a modified spear gun, or on the deck of the boat. Fish tagged on board initially showed a shallower behavior than those tagged in the water. The pattern of horizontal movements was also different between both groups. Shortly after tagging, the eight fish tagged in the water entered the Mediterranean Sea. Six of these fish reached the spawning ground located southwest of the Balearic archipelago before heading back for the Atlantic, whereas the other two traveled farther east, reaching its easternmost longitudes between Formentera and Sardinia and the South Tyrrhenian Sea, respectively. In contrast, two out of the five fish tagged on board never entered the Mediterranean Sea, and another one did enter the Mediterranean when the reproductive season was already over. These results suggest an impact of the tagging procedure on the post‐release behavior of bluefin tuna. Excluding the tags that popped‐off east of the Strait of Gibraltar, bluefin tuna stayed in the Mediterranean Sea for 22–28 days. Analysis of the median depth indicated a shallow behavior during both day and nighttime throughout the return phase of the fish from the Mediterranean Sea to the Atlantic Ocean with the exception of the area around the Strait of Gibraltar, where they showed a deeper behavior that coincided with a marked vertical gradient in the currents.  相似文献   

9.
Shelf waters of southern Australia support the world's only northern boundary current ecosystem. Although there are some indications of intense nitrate enrichment in the eastern Great Australian Bight (GAB) arising from upwelling of the Flinders Current, the biological consequences of these processes are poorly understood. We show that productivity in the eastern GAB is low during winter, but that coastal upwelling at several locations during the austral summer–autumn results in localized increases in surface chlorophyll a concentrations and downstream enhancement of zooplankton biomass. Sardine (Sardinops sagax) and anchovy (Engraulis australis) eggs and larvae are abundant and widely distributed in shelf waters of the eastern and central GAB during summer–autumn, with high densities of sardine eggs and larvae occurring in areas with high zooplankton biomass. Egg densities and distributions support previous evidence suggesting that the spawning biomass of sardine in the waters off South Australia is an order of magnitude higher than elsewhere in southern Australia. Sardine comprised >50% of the identified prey species of juvenile southern bluefin tuna (SBT, Thunnus maccoyii) collected during this study. Other studies have shown that the lipid content of sardine from the GAB is relatively high during summer and autumn. We suggest that juvenile SBT migrate into the eastern and central GAB during each summer–autumn to access the high densities of lipid‐rich sardines that are available in the region during the upwelling period. Levels of primary, secondary and fish production in the eastern GAB during summer–autumn are higher than those recorded in other parts of Australia, and within the lower portion of ranges observed during upwelling events in the productive eastern boundary current systems off California, Peru and southern Africa.  相似文献   

10.
Dolphinfish are little known migratory fish targeted by sport, artisanal and commercial fleets. In this study, we analyzed a 10 year database of incidental catches of the tuna purse seine fleet in the Pacific Ocean off Mexico with the aim to understand the environmental determinants of the spatial distribution and seasonal migration patterns of dolphinfish. We modeled the probability of occurrence of dolphinfish as a function of spatial (geographical coordinates), temporal (month/year) and environmental variables (sea surface temperature [SST], chlorophyll [CHL] and sea surface height [SSH], inferred from satellites) using logistic Generalized Additive Models. Dolphinfish preferred waters with SST values from 23 to 28°C, low (<0.2 mg/m3) CHL values, and primarily positive SSH values. Two dolphinfish hot spots were found in the study area: one in an oceanic zone (10°–15°N, 120°–125°W), which was more defined during spring, and one on the Pacific side of the Baja California Peninsula, which became important during summer. Models suggested that dolphinfish migrated through the study area following a “corridor” that ran from the Gulf of Tehuantepec along the Equatorial Upwelling zone to the oceanic hot spot zone, which in turn connected with the hot spot off the BCP. This “migratory corridor” went around the Eastern Pacific Warm Pool, which suggested that dolphinfish avoided this high temperature‐low production zone. Dolphinfish occupied zones close to certain oceanic features, such as eddies and thermal fronts. Results suggested that the primary cause of the biological hot spots was wind‐driven upwelling, because the hot spots became more important 3–4 months after the peak in upwelling activity.  相似文献   

11.
The habitat use of Pacific bluefin tuna (Thunnus orientalis; PBF) in nursery waters off the southern coast of Japan was investigated using archival tags over a 3 year study period (2012–2015), and the data were used to examine the free‐ranging habitat preferences of PBF and the relationship between their horizontal movements and the path of the Kuroshio off the Pacific coast of Japan. The path of the Kuroshio fluctuated seasonally, leading to changes in water temperature that strongly influenced the habitat use of small PBF (2–3 months after hatching). Most PBF were present in coastal waters inshore of the path of the current, and their habitat use changed in response to the distance of the current from the coast. The Kuroshio typically flowed along the coast from summer to autumn, and PBF remained in the coastal waters off Kochi Prefecture during this period. In contrast, PBF quickly moved eastward in winter when the current moved away from the coast. Throughout the winter and spring, the area of habitat use extended widely from the eastern end of the southern coast of Japan (the Boso Peninsula) to the offshore Kuroshio‐Oyashio transition region. These findings suggest that the seasonal habitat use and movement behavior of juvenile PBF are influenced by the distance of the Kuroshio axis from the coast, and the ultimate drivers are likely variations in oceanographic conditions and prey availability along the southern coast of Japan.  相似文献   

12.
ABSTRACT:   Immature Pacific bluefin tuna Thunnus orientalis , tagged with archival tags, were released near Tsushima Island in the East China Sea (ECS) during the winters of 1995, 1996 and 1997. Geolocations were estimated using the archival tags from recovered fish. These data, together with sea surface temperature (SST) data from satellite remote sensing, are used to describe the habitat used by these bluefin in the ECS from January to June for 3 years (1996, 1997, 1998), and to asses the effect of water temperature on fish distribution and movement. The results indicate that their geolocations ranged from the area north-east of Tsushima Island to the offshore area in the south-west. However, the area of highest density differed among years, being furthest south in 1996 and furthest north in 1998. The differences were probably caused by changes in SST associated with La Niña (1996) and El Niño (1998) events. Another densely populated area was identified in offshore waters of latitude 28–30 °N in 1996 (only), on the cold side of the Kuroshio front. These fish may have been prevented from moving northwards by an intrusion of Kuroshio water of approximately 25°C into the region immediately to the north-east.  相似文献   

13.
Recruitment of age‐0 Pacific bluefin tuna (Thunnus orientalis) from 1952 to 2014 was examined by a sequential regime shift detection method. The regime shifts in recruitment were detected in 1957, 1972, 1980, 1994 and 2009. The durations of regime shift ranged from 8–15 years and averaged 13.0 years. In both the total (1952–2014) and data rich (1980–2014) periods, negative relationships were found between recruitment and the Pacific Decadal Oscillation in autumn, and positive relationships were found between recruitment and sea surface temperature (SST) anomalies in the northern part of the East China Sea, in the southwestern part of the Sea of Japan, and in the waters off Shikoku and Tokai in summer and autumn. The 1994 and 2009 regime shifts in recruitment occurred in the same years as shifts in SST anomalies in the northern part of the East China Sea in summer. These results suggest that the ocean conditions in the northern part of the East China Sea are closely related to recruitment of Pacific bluefin tuna, and that the warmer conditions result in higher recruitment of the species.  相似文献   

14.
Northern bluefin tuna, Thunnus thynnus, apparently spawn only in the western Pacific and a portion of the juveniles migrate to the eastern Pacific. During the past decade, catches of northern bluefin in the eastern Pacific have declined. One possible cause for this decline, proposed by bluefin stock assessment studies, is a decline in the proportion of bluefin that migrate out of the western Pacific. This hypothesis is examined with several indices of the relative abundance of bluefin tuna in the western and eastern Pacific. These indices suggest a decline in the proportion of bluefin migrating to the eastern Pacific since 1977. This period of reduced bluefin migration coincides with a period when a prey of bluefin, Japanese sardine, Sardinops melanosticta, were abundant off Japan. It is hypothesized that in years when sardines are abundant off Japan, a higher proportion of bluefin stay in the western Pacific compared with years when sardines are scarce. Currently, the adun-dance of sardines off Japan is declining. If this decline continues, this hypothesis predicts an increase in bluefin migrating north of Hawaii and into the eastern Pacific.  相似文献   

15.
Swordfish are highly specialized top‐level predators that have been challenging to study. In this paper, data from 31 pop‐up satellite archival tags attached to swordfish from (i) the eastern Pacific, (ii) central Pacific, and (iii) western North Atlantic‐Caribbean were analyzed. Common across locations was a pronounced diel vertical pattern with daytime hours spent primarily below the thermocline and nighttime hours spent in warmer waters, close to the surface. One exception to this pattern was periodic daytime basking events which were most common in cooler waters off California. Maximum daytime depths were significantly correlated with light penetration as measured by the diffuse attenuation coefficient at 490 nm. Temperature did not appear to influence daytime depths, and swordfish tolerated both extremely low temperatures (4°C) and rapid and dramatic temperature changes (>20°C). Temperature did appear to influence the nighttime depths in the Pacific where fish typically remained in the surface mixed layer. In contrast, in the warm tropical Atlantic this was not the case, and nighttime depths were much deeper. In all areas, nighttime depth increased around the full moon. Given the parallels between the vertical movement patterns of swordfish and those of the deep sound scattering layer we suggest that swordfish vertical distribution patterns, especially during daytime, are influenced largely by resource availability. At night, when swordfish are typically targeted by fisheries, both ambient light and temperature influence movements. Understanding vertical movement patterns of swordfish can help evaluate gear vulnerability, improve population assessments, and potentially reduce fisheries bycatch.  相似文献   

16.
In mass culture of Pacific bluefin tuna Thunnus orientalis, yolk‐sac larvae of other species are fed as a major prey item to tuna larvae from 7 to 8 mm in total length. Marked growth variations in tuna larvae are frequently observed after feeding of yolk‐sac larvae, and this variation in the growth of tuna larvae is subsequently a factor leading to the prevalence of cannibalistic attacks. To elucidate details of the mortality process of hatchery‐reared tuna larvae after the initiation of yolk‐sac larvae feeding, we compared the nutritional and growth histories of the surviving (live) tuna larvae to those of the dead fish, found dead on the bottom of the tank, as direct evidence of their mortality processes. Cause of mortality of tuna larvae 3 and 5 days after the initiation of feeding of yolk‐sac larvae was assessed from nitrogen stable isotope and otolith microstructure analyses. Stable isotope analysis revealed that the live fish rapidly utilized prey fish larvae, but the dead fish had depended more on rotifers relative to the live fish 3 and 5 days after the initiation of feeding of yolk‐sac larvae. The growth histories based on otolith increments were compared between the live and dead tuna larvae and indicated that the live fish showed significantly faster growth histories than dead fish. Our results suggest that fast‐growing larvae at the onset of piscivory could survive in the mass culture tank of Pacific bluefin tuna and were characterized by growth‐selective mortality.  相似文献   

17.
We investigated the broad‐scale movements and pelagic habitats of large juvenile dusky sharks (Carcharhinus obscurus) off Southern Australia. Pop‐up satellite archival tags (PSATs) were deployed on three large juvenile dusky sharks (～2.2–2.6 m total length) for 6 months in Spencer Gulf during 2010. Tagged dusky sharks all migrated westward and across the Great Australian Bight (GAB) during autumn to offshore shelf waters off Western Australia. Estimated minimum distances travelled ranged from 1760 to 2736 km. Depths occupied by tagged dusky sharks ranged from the surface to 355 m. The most common thermal ranges occupied were 19–22°C. Broad‐scale movements of large juvenile dusky sharks across the continental shelves combined with periods of residency in semi‐protected gulf waters indicated that a multi‐jurisdictional management approach may be appropriate for this species.  相似文献   

18.
Howell PJ, Dunham JB, Sankovich PM. Relationships between water temperatures and upstream migration, cold water refuge use, and spawning of adult bull trout from the Lostine River, Oregon, USA.
Ecology of Freshwater Fish 2010: 19: 96–106. This article is a US Government work and is in the public domain in the USA Abstract – Understanding thermal habitat use by migratory fish has been limited by difficulties in matching fish locations with water temperatures. To describe spatial and temporal patterns of thermal habitat use by migratory adult bull trout, Salvelinus confluentus, that spawn in the Lostine River, Oregon, we employed a combination of archival temperature tags, radio tags, and thermographs. We also compared temperatures of the tagged fish to ambient water temperatures to determine if the fish were using thermal refuges. The timing and temperatures at which fish moved upstream from overwintering areas to spawning locations varied considerably among individuals. The annual maximum 7‐day average daily maximum (7DADM) temperatures of tagged fish were 16–18 °C and potentially as high as 21 °C. Maximum 7DADM ambient water temperatures within the range of tagged fish during summer were 18–25 °C. However, there was no evidence of the tagged fish using localized cold water refuges. Tagged fish appeared to spawn at 7DADM temperatures of 7–14 °C. Maximum 7DADM temperatures of tagged fish and ambient temperatures at the onset of the spawning period in late August were 11–18 °C. Water temperatures in most of the upper Lostine River used for spawning and rearing appear to be largely natural since there has been little development, whereas downstream reaches used by migratory bull trout are heavily diverted for irrigation. Although the population effects of these temperatures are unknown, summer temperatures and the higher temperatures observed for spawning fish appear to be at or above the upper range of suitability reported for the species.  相似文献   

19.
The movement of adult muskellunge, Esox masquinongy Mitchill, has been investigated in a variety of systems, but temperature selection by muskellunge has not been examined where well‐oxygenated waters were available over a range of temperatures for much of the year. Thirty subadult and adult muskellunge tagged internally with temperature‐sensing radio tags were tracked from March 2010 to March 2011 in a Tennessee reservoir. Mean tag temperatures were 18.9 °C in spring (March to May), 22.1 °C in summer (June to August), 16.5 °C in autumn and 9.8 °C in winter (December to February). When the greatest range in water temperatures was available (7.1–33.3 °C; May to early August 2010), their realised thermal niche (mean ± 1 SD) was 22.3 °C ± 1.8; the realised thermal niche was affected by fish size (smaller fish selected slightly warmer temperatures) but not sex. An electric generating steam plant discharging warm water resumed operation in January 2011, and most (86%) tagged fish occupied the plume where temperatures were ≈10 °C warmer than ambient water temperatures. No mortalities were observed 15 days later when plant operations ceased. Their affinity for the heated plume prompted concerns that muskellunge will be too easily exploited when the plant operates during winter.  相似文献   

20.
Tuna aquaculture is currently dependent on the wild capture of juveniles for production. The development of hatchery technology for bluefin and other tunas would be a major step forward in improving sustainability of their aquaculture. The present study overviews the technology in the life cycle completion of the Pacific bluefin tuna (PBT) Thunnus orientalis (Temminck et Schlegel) under aquaculture conditions in Kinki University, and the problems to be solved for the establishment of tuna hatchery technology. On 23 June 2002, broodstock of PBT that were artificially hatched and reared spontaneously spawned in captivity. The resulting eggs hatched and were subsequently reared to the juvenile stage. The spawning fish were the result of a research project started in 1987 to rear wild‐caught juvenile PBT that were several months old. Fertilized eggs were obtained from these fish in 1995 and 1996. Resulting juveniles (the artificially hatched first generation) were reared to maturity and spawned in 2002. Over the summer of 2002, 1.63 million eggs from these fish were used for a mass rearing experiment, and 17 307 juveniles were produced and transferred to an open sea net cage. Of these artificially hatched second‐generation PBT, 1100 grew to approximately 95 cm total length and 14 kg body weight in 22 months. This procedure means the completion of PBT life cycle under aquaculture conditions, which was first attained among large tuna species. The problems awaiting solution in PBT hatchery production are their unpredictable spawning in captivity, to improve survival during the first 10 days post hatch, to reduce cannibalism in larval and juvenile stages, and to solve collision problem causing high mortality during the juvenile stage.  相似文献   

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