瀬戸内海広島湾のアサリ漁場の干潟における大型クロダイAcanthopagrus schlegelii（タイ科）の出現の季節変化

広島湾最大のアサリ漁獲量のある漁場である広島県廿日市市の前潟干潟において，2003年2月から2004年1月の1年間にわたり刺網による調査を行い，アサリ食害魚種である大型のクロダイAcanthopagrus schlegeliiの出現状況を明らかにした。9種73個体の魚類が採集され，クロダイ（23.6～48.5cm TL）が全個体数の79％を占める優占種であった。クロダイの月別CPUE（個体数/300m/回）は0～18.8の範囲であり，6月末に急上昇し，7月末には最高値の18.8を示し，8月末，9月末も高値を示した。本種は，初夏から秋季の6月末～10月末の5ヶ月間に多く出現すること，この間は，体サイズにかかわらず干潟域を利用することが明らかになった。

Black porgy, Acanthopagrus schlegelii (Family: Sparidae), is a commercially important fish in Japan. This species is known as a major predator of the short-neck clam Ruditapes philippinarum in tidal flats. Seasonal occurrence of large fishes such as the porgy was investigated from February 2003 to January 2004 at the Maegata tidal flat, which has the largest catch of short-neck clam in Hiroshima Bay, western Seto Inland Sea. As a result, 73 individuals from nine species were collected by monthly gill net sampling. A. schlegelii, 23.6-48.5 cm total length was the dominant species and accounted for 79% of the total individuals. The catch per unit effort (CPUE: number of fish caught/300 m of netting) of the porgy was 0–18.8. The CPUE rapidly increased in late June. In late July, it reached 18.8, the highest annual value, after which the CPUE maintained high values during late August and late September. From late November values were low (0-3.0) again. These results indicate that large-sized A. schlegelii occur seasonally in the tidal flats from late June to late October.