Yoshihiko Kamei

Thermohaline Staircases in the Warm-Core Ring off Cape Erimo, Hokkaido and Their Fluxes Due to Salt Finger

Thermohaline staircases off Cape Erimo, Hokkaido are described and their physical properties are compared with those in other seas. The mean fluxes for heat and salt across the interface induced by salt finger were estimated as 105 cal cm−2d−1, and 0.03 g cm−2d−1, respectively. These values were in the same order as those in Caribbean Sea. The “effective eddy diffusivities” were also in the same order as the Caribbean ones. This suggests that the double-diffusive convection plays on important role on the water mass conversions occurring in the interfrontal zone between the Oyashio and the Kuroshio Waters.

Effects of hypoxia on the feeding intensity and somatic condition of the blackfin flounder Glyptocephalus stelleri in Funka Bay, Japan

To clarify effects of hypoxia on feeding and somatic condition of blackfin flounder Glyptocephalusstelleri, we studied the temporal relationship between hypoxia and feeding intensity as well as the condition of this species in May and August 2006–2012. Hypoxia occurred near the seafloor in August between 2010 and 2012 but not in May. Population densities of gammarid amphipods Ampelisca brevicornis and Melita sp., the main prey items of blackfin flounder, were consistently low; however, the somatic condition and feeding intensity of blackfin flounder increased during hypoxia. Such an increase was not detected in May 2012 under non-hypoxic conditions. These facts imply that the hypoxia increased prey availability for blackfin flounder through the increased exposure of the gammarids over the sea floor, and, thus, resulted in improved body condition in August 2011 and 2012. Hypoxia positively would influence the somatic condition and feeding intensity of blackfin flounder in Funka Bay in August 2011 and 2012; however, the somatic condition during this period did not reach the levels recorded in 1983, suggesting that habitat quality for blackfin flounder in Funka Bay in 2011 and 2012 was worse than that in 1983.