報告書番号

U95002

タイトル（和文）

ヒラメ稚魚の無眼側黒化に対する飼育環境の影響

タイトル（英文）

Effects of rearing conditions on the ambicoloration of young Japanese flounder

概要 （図表や脚注は「報告書全文」に掲載しております）

ヒラメの無眼側黒化防止技術の開発に資するために、光や飼育槽底面の性状がヒラメ雑魚の黒化に与える影響を検討した。（１）飼育槽底面が透明樹脂板の場合には、下方からの照度が７ｌｕｘと低くても、１１００ｌｕｘの場合と同様に、すべての個体が黒化した。（２）飼育槽底面に砂を敷設した場合には、ほとんど黒化しなかったが、紙ヤスリや黒色樹脂板では大部分の個体が黒化した。（３）透明砂を敷設した場合には、下方からの照度を１４００ｌｕｘとしてもほとんど黒化は生じなかった。これらの結果より、ヒラメの黒化に対する飼育環境の影響としては、無眼側の照射光や、無眼側の砂に似た刺激の有無ではなく、ヒラメが潜ることができる砂状物質の有無が重要であることが明らかとなった。

概要 （英文）

Effects of light intensity and/or bottom condition such as sand,sand paper,and transparent grass powder on the abnormal pigmentation of the blind side(ambicoloration)of Japanese flounder were examined.Juvenile or young flounder from hatchery-reared source were reared for 4 to 16 weeks at 23ﾟC with commercial pellet diet in the plastic fish tank.The lid and bottom of the tank were transparent so as to irradiate the fish with fluorescent light up-and down-ward.The side walls of the tank made of matted black plastic.(1)When the bottom of the tank was transparent plastic plate,the ambicoloration was observed in all fish tested independently of the light intensity at the bottom(downward/upward illumination intensity examined;1300/1100,1300/60,150/7 lux).(2)When the bottom of the tank was covered with transparent grass powder(0.5-1mm in diameter)in 1cm thickness with upward illuminance intensity of 1400 lux,only 27% of fish showed the abnormal pigmentation.On the other hand,100% of fish showed the abnormalpigmentation,when the bottom was covered with white plastic plate with upward illuminamce intensity of only 10 lux.(3)The enlargement of the abnormaly pigmented area in the blind side was observed in no fish,when the bottom of the fish tank was covered with sand(0.5-1mm in diameter)in 1cm thickness.While,the enlargement of the pigmented area in the blind side was observed in the 50% of fish tested,when the bottom of tank was covered with sand paper to give the blind side sandy feeling,.From these results,it is considered that the light irradiation to the blind side is not the main cause of the ambicoloration,and that covering the bottom of fish tank with granular substance into which the flounder can submerge has the effect on preventing the abnormal pigmentation.

報告者

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