Gravimetric Method for Sorting Blacktip Grouper <I>Epinephelus fasciatus</I> Juveniles with and without Swimbladder Inflation

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  • 濃塩水を用いたアカハタ稚魚の鰾開腔魚と鰾未開腔魚の選別
  • ノウシオミズ オ モチイタ アカハタ チギョ ノ ヒョウカイコウギョ ト ヒョウミカイコウギョ ノ センベツ

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We describe a simple sorting method for separating hatchery-reared blacktip grouper Epinephelus fasciatus juveniles (4.6-6.7 cm in total length) with and without swimbladder inflation based on body density differences. The body density of the juveniles was measured in a series of anaesthetic-hypersaline salt water solutions from 3.5 to 16% with 0.5% steps. The density of a hypersaline salt water floated the juveniles with swimbladder inflation was 1.030-1.098 g/cm3 at 27.8°C and 1.025-1.081 g/cm3 at 19.4°C, and that of nonswimbladder inflation was 1.094-1.116 g/cm3 at 27.8°C and 1.078-1.112 g/cm3 at 19.4°C. As a result, it was impossible to sort completely the juveniles with and without swimbladder inflation by the buoyancy difference because the values overlapped. Therefore, the density of an anaesthetic-hypersaline salt water solution for eliminating juveniles without swimbladder inflation was considered in 1.090 g/cm3 at 27.8°C and 1.075 g/cm3 at 19.4°C. When the efficiency of separation for large population was tested at 1.075 g/cm3 at 19.6°C, 96% of the juveniles with swimbladder inflation floated and without swimbladder inflation all sank.


  • Aquaculture Science

    Aquaculture Science 60 (3), 421-425, 2012

    Japanese Society for Aquaculture Science


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