網の付着物に関する研究 : 付着ヌタの季節変化

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  • Studies on the Attaching Materials of the Nets―II Seasonal Variations of the fine Attaching Materials.

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1. We observed the seasonal variations of fine attaching materials and living periphytons (except micro-organisms) on Cremona nets laid in the sea and the optical density (O.D.) of sea water, being measured by the clinical photo-electric colorimeter (660 mμ, 2 cm. cuvette) at the station in Sakibe Inlet, Sasebo Bay, from October 1958 to December 1959. 2. Peaks in the seasonal variations of fine attaching materials occured three times from spring to fall in the case of the nets laid during a month, being two times in that during two months and from fall to winter in that during three months, respectively. The vertical differences of the attaching materials was smaller in summer and in fall. 3. O.D. was higher from summer to fall and lower from winter to spring. The vertical differences of it was larger in summer and in fall, small in winter and in spring. Usually, O.D. was higher at the bottom and lower in the middle than other layers in each season. 4. Negative corelations were seen between the seasonal variations of fine attaching materials and O.D. from winter to spring, although being positive from summer to fall. 5. It seems that these relations are attributed to the ecological effects of attaching algae and animals, especially Gammarids, thrived abunduntly, were a dominate factor which leads to the large volumes of attaching materials from winter to spring.

1.'58年10月から'59年12月にわたって,浸漬クレモナ網の付着ヌタと付着生物及び海水濁度の季節変動を観察した.2.付着ヌタの季節変動は,1カ月網では春・夏及び秋に,2カ月網では春と秋に,3カ月網では冬と秋にそれぞれ山がある.3.海水の濁度は冬～ 春に低く,夏～ 秋に高い.上下層の差は濁度の高い季節には大きく,低い時期には小さい。また周年を通じて濁度は底層で高く,表・中層の順に低くなる.4.冬～ 春では濁度と付着ヌタ量は逆関係にある.1カ月網の水深別では,濁度の上下層の差の大きい夏～秋に,付着ヌタの上下層の差は小さく,冬～ 春の前者の小さい時に後者の差が大きい.5.付着ヌタの季節変動は付着生物(micro-org.を除く)によって影響をうける． 特に冬～ 春にはGammarideaの影響は大きい.6.1カ月間以上の浸漬では,大型生物はヌタの付着に阻止的に作用するものと考えられる.

長崎大学水産学部研究報告, v.9, pp.64-69; 1960

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