Absorption of different food sources by sea cucumber Apostichopus japonicus (Selenka) (Echinodermata: Holothuroidea): Evidence from carbon stable isotope

The present experiment compared the effects of 6 different diet types, including benthic matter collected from natural sea water (diet A), brown algae Sargassum thunbergii (diet B), red algae Gracilaria lemaneiformis (diet C), mixture of benthic matter and G. lemaneiformis (diet D), mixture of benthic matter and S. thunbergii (diet E) and mixture of G. lemaneiformis and S. thunbergii (diet F) on the growth of sea cucumber Apostichopus japonicus. The sea cucumber fed mixture diet containing benthic matter showed the higher specific growth rate (SGR) relative to the single feed ingredient and sea cucumbers fed diet D showed the maximum SGR. Carbon stable isotope evidence revealed the different feeding preference of sea cucumbers among the various feed ingredients. The results of the present study suggested that G. lemaneiformis might be more preferable to the nutritional requirements of sea cucumber relative to the traditional sea cucumber feed S. thunbergii. G. lemaneiformis which has been widely cultured with higher availability and lower feed cost is suitable for the manufacture of sea cucumber feed in aquaculture practice. Addition of benthic matter collected from the natural sea waters containing microalgae, bacterial and muddy materials is helpful to improve the feeding and absorption of macroalgae by sea cucumber and subsequently to enhance the growth and production of sea cucumber.