Effect of ambient temperature on the vertical distribution and movement of Pacific bluefin tuna Thunnus thynnus orientalis

The marine spawning area of the New Zealand longfin eel Anguilla dieffenbachii is unknown. The present study used 3 popup tags to obtain information on the offshore swimming behaviour and possible swimming directions and destination of migrating eels. All 3 eels showed very consistent behaviour and underwent daytime dives to depths of 600 to 900 m, where they experienced temperatures of 6 to 7°C. These dives were followed by nighttime ascents to depths of 200 to 300 m. From the consistency of these dives, we propose that eels are using regular exposure to cool temperatures to regulate the rate of maturity. While swimming at depth could also reduce predation, the increased pressure would stimulate development of the ovaries, something mediated by ascent to shallower water. Comparisons of ascent locations and swimming speeds are consistent with spawning in the tropics, possibly in the South Fiji basin. KEY WORDS: Anguilla dieffenbachii · Freshwater eel · Diving · ThermoregulationResale or republication not permitted without written consent of the publisher

“…Dagorn et al 2000, Kitagawa et al 2000, Musyl et al 2003 and ocean sunfish (Cartamil & Lowe 2004). Tuna also use such dives to regulate body temperature (e.g.…”

Section: Discussionmentioning

confidence: 99%

Vertical migrations may control maturation in migrating female Anguilla dieffenbachii

Jellyman¹,

Tsukamoto²

2010

“…This diel pattern is likely induced by changes in light intensity. Changes in diel light intensity are thought to initiate similar bounce diving behavior in other pelagic fishes, such as blue sharks Prionace glauca (Carey & Scharold 1990), swordfish Xiphias gladius (Carey & Robison 1981), and some tunas (Holland et al 1990b, Kitagawa et al 2000. Various explanations have been posited for this behavior, most of which focus on prey acquisition as the primary motivation for diving activity.…”

Section: Vertical Movementsmentioning

confidence: 99%

Diel movement patterns of ocean sunfish Mola mola off southern California

Cartamil¹,

Lowe²

2004

115

Ocean sunfish Mola mola are a seasonally common inhabitant of southern Californian waters, and comprise the largest bycatch component (29% of total catch) of the California drift gillnet fishery for swordfish. We used temperature and depth-sensing acoustic transmitters to quantify the fine-scale movement patterns of ocean sunfish near Santa Catalina Island, California. Eight ocean sunfish were tracked continuously over 24 to 72 h periods, during which oceanographic data were collected every 2 h. Geographical position and depth of tracked fish were analyzed in relation to oceanographic data and time of day. Ocean sunfish traveled a mean distance of 26.8 ± 5.2 (± SD) km d ) (SD = 0.58) was significantly higher than either nighttime period. Horizontal movements were highly directional, with angular concentration values (r) as high as 0.765 over the duration of entire tracks. Nocturnal vertical movements were confined to the surface mixed layer and thermocline, while diurnal vertical movements were often characterized by repeated dives below the thermocline. A significant relationship was found between maximum dive depth and the post-dive period spent in the mixed layer, suggesting that ocean sunfish may behaviorally thermoregulate between deeper daytime dives. The observed depth-distribution patterns of ocean sunfish indicate that lowering the depth of gillnets in the water column could significantly reduce bycatch of this species in the California drift gillnet fishery. KEY WORDS: Acoustic telemetry · Pelagic tracking · Drift gillnet fishery · Bycatch · ThermoregulationResale or republication not permitted without written consent of the publisher

“…Although electronic devices, such as archival tags, can accurately log daily geo-location, swimming depth, ambient water temperature, and other data (Kitagawa et al 2000, 2004, 2009, Block et al 2011, data for a fish's entire life are not available from these devices because very small fish cannot carry these devices, as noted by Shiao et al (2010). Moreover, only a single fish can be tracked with one electric device at a time, which is generally expensive, and released tags are not always recovered.…”

Section: Introductionmentioning

confidence: 99%

Otolith δ18O of Pacific bluefin tuna Thunnus orientalis as an indicator of ambient water temperature

Kitagawa¹,

Ishimura²,

Uozato³

et al. 2013

Self Cite

To detect the relationship between ambient temperature and otolith stable oxygen isotope (δ O, −0.17 ‰) were lower, but were not significantly different from those of larvae reared in + 0.31 ‰ water, which is the δ 18 O value of the water in which the spawners were raised. These results suggest that the sample size for the 32 psu experiment was too small and that the rearing durations were too short to affect the otoliths completely. Our results demonstrate that otolith δ