- 著者
- 古田 晋平
- 出版者
- 公益社団法人 日本水産学会
- 雑誌
- 日本水産学会誌 (ISSN:00215392)
- 巻号頁・発行日
- vol.65, no.2, pp.167-174, 1999-03-15 (Released:2008-02-01)
- 参考文献数
- 19
- 被引用文献数
- 12 13
鳥取県沿岸浅海域においてヒラメ当歳魚の分布量, 全長組成, 摂餌状態および肥満度の季節的変化を調査した。また, 同様にアミ類の分布量とヒラメ1-2歳魚の胃内容物も併せて調べた。5月下旬から6月上旬まで大量に分布していたヒラメ当歳魚のうち, 小型個体は6月中旬から下旬にかけて急激に減少した。これらの個体の全長組成は沖合に移動した大型個体には結びつかないことから, 急激な減少は浅海成育場における減耗の結果と考えられた。この減少と同時期に, 小型個体の主要な餌料であるアミ類の分布量が急激に減少して, 小型個体の摂餌率と肥満度が低下し, ヒラメ1-2歳魚の胃内容物から当歳魚が出現する率が急激に上昇した。以上より, 摂餌条件の悪化に起因する飢餓の進行が被食による大量減耗を誘発したと考えられた。
1 0 0 0 OA 鳥取県沿岸浅海域に放流したヒラメ人工種苗の分布,成長および個体数変動
- 著者
- 古田 晋平 渡部 俊明 山田 英明 西田 輝巳 宮永 貴幸
- 出版者
- 公益社団法人 日本水産学会
- 雑誌
- 日本水産学会誌 (ISSN:00215392)
- 巻号頁・発行日
- vol.63, no.6, pp.877-885, 1997-11-15 (Released:2008-02-29)
- 参考文献数
- 21
- 被引用文献数
- 25 28
Stock enhancement programs involving the mass release of hatchery-reared Japanese flounder have been conducted in nearly all coastal regions of Japan. These programs have been regionally successful, however, many fundamental problems that inhibit further success remain. Changes in distribution, growth and abundance of released juvenile flounder were investigated in the coastal area of Tottori Prefecture form 1989 through 1991. Flounder juveniles were directly counted by divers along transect lines at 6 depths between 0.5m and 13m. Beam trawl samples were taken and densities were estimated using gear efficiencies obtained by comparison between the number of fishes collected by the trawl and the number counted by divers. Released juveniles were found mainly in waters shallower than 10m, and showed nearly the same distribution pattern as wild juveniles. A significant length increase was not observed in recaptured flounder. The number of reared juveniles rapidly decreased during the first week after release and the retention rate after the 1st week ranged from 3.5% to 26.9%. Based on changes in distribution and growth after release, the authors concluded that the rapid reduction in the number of released juveniles was caused by high mortality. Causes of mortality of released and wild flounder are discussed in relation to the abundance of prey and predation by piscivorous fishes.