We investigated the oxygen consumption and resistance for hypoxia in captivity of coral trout grouper Plectropomus leopardus. The fish with an average bodyweight 3 g consumed 515, 667 and 654 mg/kg/h of oxygen at water temperature 25, 27 and 30℃, respectively. On the other hand, one with an average bodyweights 5 g consumed 468 and 804 mg/kg/h at 25 and 30℃. The former groups recorded a decrease in oxygen consumption rate from 5 mg/L. The latter groups recorded from 4 mg/L. In a water temperature ranges from 25 to 30℃, 3 g fish began to die at dissolved oxygen levels of 0.99 to 1.06 mg/L (oxygen saturation of 15.4 to 16.0%), while at 0.73 to 1.15 mg/L (oxygen saturation of 11.0 to 18.8%), 5 g fish groups began to die. This is a significant result and gives a scientific impact on hypoxia for coral trout grouper aquaculture.

This study clarified the structures and seasonal changes of the annual Zostera marina population from April 2003 to November 2004, growing at Tategami-ura, Ago bay, Mie prefecture. Productive structures showed the graminous types excluding flowering period (May-June). Biomass and shoot density reached maximum values in May-June. At that time, over 80% of shoots were flowering shoots. And then, all shoots were disappeared in summer. From October-November, a lot of seedlings recruited and grew to flowering shoots by next spring. Maximum daily net production showed 4.50 g m^-2 day^-1 in June, which was similar level to that of the perennial Zostera marina population. However, yearly net production (305.0 g m^-2 year^-1) showed lower than that of the perennial type. Yearly maximum biomass was 152.6 g m^-2, and production/biomass (P / B) ratio was 2.0. It is necessary to more research in the production because the biomass and shoot density of the annual population verify drastically year to year.