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 region

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.

Foraging areas of streaked shearwaters in relation to seasonal changes in the marine environment of the Northwestern Pacific: inter-colony and sex-related differences

“…Grand mean ± SD is also shown Sugisaki & Kurita 2004, Iwahashi et al 2006, Sakurai 2007. Predators of these pelagic fishes, such as tunas and seabirds, are also known to migrate into this area in the summer (Shiomi & Ogi 1992, Nihira 1996, Kitagawa et al 2004. Although streaked shearwaters broadly showed the northward shift of their foraging areas, the pattern of seasonal changes differed between the colonies depending upon the location of accessible productive areas.…”

“…The eastward-flowing Kuroshio and Kuroshio Extension regions, on the other hand, where shearwaters from MK feed, support major spawning and nursery grounds for various pelagic fishes, such as anchovy and sardine (Aoki & Miyashita 2000, Kasai et al 2002, Komatsu et al 2002, Sassa et al 2004, Takahashi & Watanabe 2004. Frontal cyclonic eddies in this region enhance primary and secondary productivity (Kimura et al 1997, 2000, Qiu 2001, supporting a range of predators, including, tunas, turtles, and seabirds (Kitagawa et al 2004, Takasuka et al 2004, Polovina et al 2006, Suryan et al 2006, Shaffer et al 2006.…”

“…Seabirds from neighbouring colonies tend to feed in nonoverlapping zones to minimise intra-specific competition for food resources, with the zone of feeding habitat typically closer to a focal colony than any of the neighbouring colonies in the hinterland (Cairns 1989). Females of MK often used offshore areas along the Kuroshio and Kuroshio Extension, where productivity is locally enhanced by frontal cyclonic eddies in lowproductivity Kuroshio water, and where many predators congregate to feed (Kimura et al 1997, 2000, Kitagawa et al 2004, Polovina et al 2006. Waters of the Kuroshio and Kuroshio Extension are much closer to MK than to SA (Fig.…”

Depth and temperature preferences of the deepwater flatfish Greenland halibut Reinhardtius hippoglossoides in an Arctic marine ecosystem

“…Satellite telemetry has been used to study the movement, behaviour and environmental preferences of a wide range of aquatic species, including sharks (Sims et al 2003, 2008, Teo et al 2004, Brunnschweiler et al 2010) and many teleostei, such as tuna (Block et al 2001, Kitagawa et al 2004, Schaefer & Fuller 2004 and flatfishes (Seitz et al 2003, Loher & Seitz 2006, Loher & Blood 2009). These tags are attached externally to the fish, during which time they record depth, temperature and light, and release after a specified length of time, thus providing insight into horizontal and vertical movements and habitat use over different spatial and temporal scales (Block et al 2001, Wearmouth & Sims 2009, Humphries et al 2010.…”

Discovering where bluefin tuna, <i>Thunnus thynnus</i>, might go: using environmental and fishery data to map potential tuna habitat in the eastern Mediterranean Sea

“…More recently, Druon et al (2011) identified the potential bluefin tuna spawning season as occurring from mid-May to July, gradually building up from eastern to western Mediterranean waters. Kitagawa et al (2004) described that during the spawning season (June) bluefin tunas stop undertaking repeated dives, limiting their movements to the surface layer. This behaviour was interpreted as behavioural thermoregulation.…”