Rotifer-Size Selectivity and Optimal Feeding Density of Bluefin Tuna, Thunnus thynnus, Larvae.

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  • 人工孵化クロマグロ仔魚のワムシに対する摂餌サイズ選択性と最適給餌密度

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Abstract

Rotifer-size selectivity and the optimal feeding density were examined for reared bluefin tuna larvae. Larvae were obtained from the broodstocks raised for 11 years in captivity. Larvae were fed rotifers at 5 different densities, 5, 10, 20, 30, or 40 ind./ml, on the day of the commencement of feeding (3 days after hatching) and the next day. In these experiments, rearing at the feeding densities of 10 and 20 ind./ml was extended to 7 days after hatching. Larvae were sampled and the gut contents were examined. The average rotifer number eaten by the larvae was lower at the density of 5 ind./ml than at other densities on the morning of day 3, and was lower at the density of 40 ind./ml on day 4 after hatching. This means that the optimal range of feeding density of rotifers for bluefin tuna larvae is from 10 to 30 ind./ml at the initial feeding. The lorica length (LL) of rotifers positively selected by larvae ranged from 100 μm to 239 μm from day 3 to 7 after hatching, and the lorica width (LW) ranged from 80 to 179 μm. The sizes of LL and LW positively selected by larvae shifted to larger ones with increasing time after hatching in this size range.

Journal

  • Aquaculture Science

    Aquaculture Science 48 (2), 169-177, 2000

    Japanese Society for Aquaculture Science

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