春季の日本海鳥取沖におけるカタクチイワシの成熟と産卵

抄録

The purpose of this study was to clarify the characteristics of maturation and spawning of the Japanese anchovy, Engraulis japonicus, off Tottori, Sea of Japan during spring. The research was based on histological analysis of ovaries and gonadsomatic index (GSI) of female anchovies caught by purse seine fisheries off Tottori and landed at the Sakaiminato fisheries port in 2003 and 2004. In addition, the frequency of anchovy eggs collected during 1995 and 2004 using a NORPAC-net off Tottori by the Tottori Prefectural Fisheries Experimental Station was assessed. Female GSI was positively correlated with body length from April to May, and yolked stage or more matured stage oocytes were found in ovaries of females ≥4.7 in GSI and ≥11.9 cm in body length. Females with migratory nucleus stage oocytes were 18% of total females in March. More than 90% of total females had nucleus stage or more matured stage oocytes in April and May. Frequency of matured females increased rapidly when the sea surface temperature increased to about 12°C in spring. Anchovy eggs were collected where the SST was between 11.8 and 19.4°C from April to June. This study found that anchovy can spawn in low temperature area off Tottori in spring.