相模湾東岸における大型アワビ類浮遊幼生の出現動態に影響する環境要因

抄録

Planktonic larvae of three abalone species (Haliotis discus discus, H. madaka and H. gigantea) were collected from October to January in 2004–2010 on the south (Miura) and the west coast (Yokosuka) of Miura Peninsula, Sagami Bay, Japan. Species identification by PCR-RFLP method was conducted for the larvae collected in Yokosuka from 2004 to 2006. The relationships between larval occurrence pattern and environmental factors were examined. High larval densities over 1 ind. m^-3 were detected in every year except 2007 in Yokosuka, but only in 2007 and 2008 in Miura. Meanwhile, larval occurrences in lower densities were observed several times in every year in both areas. During the survey period, maximum larval densities were 0.06–2.64 and 0.57–5.07 ind. m^-3 in Miura and Yokosuka, respectively. In many cases, high-density larvae appeared after passages of storms with high waves, suggesting that spawning events of the abalone species were induced by storms. Larval occurrences were not synchronized between Miura and Yokosuka although those were synchronized among the stations in each area. In the larvae collected from 2004 to 2006 in Yokosuka, H. discus discus, H. madaka, H. gigantea and the hybrid of H. discus discus and H. madaka occupied 41%, 2%, 51% and 6%, respectively. In Yokosuka, the maximum larval density in each year was positively correlated with the averaged water temperature from the previous July to December, especially with that in July. This result suggests that water temperature in the gonad developmental period (from July to December) is an important factor affecting maturation and fecundity of adult abalone. In both areas, the annual first occurrences of larvae from 2004 to 2010 were observed between 1969 and 2465°C·day in the effective accumulated temperature (EAT), indicating that adults of these abalone species become possible to spawn about 2260°C·day in EAT.