Environmental changes influence foraging behavior for most animals. Dolphinfish, Coryphaena hippurus, are epipelagic predators and have a cosmopolitan tropical to warm-temperate (>20°C) distribution. We simultaneously obtained the ambient temperature and the foraging behavior (i.e., swimming speed, depth and tailbeat acceleration) of dolphinfish, using an acceleration data-individuals. Although the dolphinfish spent a mean ± standard deviation of 43.4±27.7% of their time at the surface (0-5 m), dive excursions from the surface (DES) were observed in all individuals and maximum DES depths ranged from 50.1 to 95.4 m. DES events resulted dives below the thermocline for these dolphinfish, and there was a significantly positive relationship between the isothermal layer depth (ILD) and DES depth. Our results demonstrate that dolphinfish avoided the rapid thermal change beyond the thermocline, and their prey is most likely found in the upper layers of the thermocline. Gliding behavior during the DES phase was also observed and dolphinfish gradually descended to deeper waters with gliding. The gliding time was longer when the ILD was deeper, and fish tended to dive deeper. We suggest that dolphinfish adopt gliding behavior to search a broader range of depths for prey, while minimizing energy use.

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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.

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Broadcast-spawning scleractinian corals annually release their gametes with high levels of synchrony, both within and among species. However, the timing of spawning can vary inter-annually. In particular, the night of spawning relative to the full moon phase can vary considerably among years at some locations. Although multiple environmental factors can affect the night of spawning, their effects have not been quantitatively assessed at the multi-regional level. In this study, we analysed environmental factors that are potentially correlated with spawning day deviation, in relation to the full moon phase, in Acropora corals inhabiting seven reefs in Australia and Japan. We accordingly found that sea surface temperature and wind speed within one to two months prior to the full moon of the spawning month were strongly correlated with spawning day deviations. In addition, solar flux had a weak effect on the night of spawning. These findings indicate that Acropora have the capacity to adjust their development and physiology in response to environmental factors for fine-tuning the timing of synchronous spawning, thereby maximizing reproductive success and post-fertilization survival.

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