Age and growth of mitre squid Photololigo chinensis in the Tonkin Gulf of Vietnam based on statolith microstructure

摘要

A total of 254 mitre squid Photololigo chinensis collected in the coastal area of Tonkin Gulf was subjected to daily increment of statolith analysis to determine the ages. The oldest individuals observed were 194 days old for specimens collected in the summer-autumn season. Size-at-age relationship was best described by power function for both individuals hatched in spring-summer and autumn winter periods. P. chinensis exhibited sexual dimorphism in the relative growth of the mantle length: males grew faster in length compared with females while weight growth rates were similar for both sexes. Seasonal factors strongly influenced the growth of squid, and the growth rates in the warm water season was higher than those in the colder season.%トンキン湾沖合海域から採集されたヒラケンサキイカ254個体について平衡石輪紋から推定された日齢に基づき成長解析を行った。最長齢の個体は夏秋季に採集された194日齢のものであった。日齢から推定された春夏季および秋冬季発生群の齢-外套長の関係はそれぞれ高い有意性を示した。本種は外套の成長において性的二型を示し，体重量の成長が類似するのに対し，雄の外套長の成長は雌にくらべ優位に速いことが示された。ヤリイカ類の成長には季節的な要因が強く影響し，成長率は寒冷期にくらべ温暖期で明らかに高かった。