Feeding preference of Apostichopus japonicus: comparing carbon stable isotope analysis and carbon budget approach

Abstract

Research into the feeding preferences of the sea cucumber Apostichopus japonicus is essential for its aquaculture. We adopted both carbon budget and stable isotope analysis approaches to determine the feeding preference of this species. Powdered Chaetomorpha linum, Zostera marina detritus, and muddy sediment mixed at 5 dry weight ratios (40:0:60, 30:10:60, 20:20:60, 10:30:60, and 0:40:60; diets 1, 2, 3, 4, and 5, respectively) were fed to juvenile sea cucumbers (mean body weight: 10.45 g) for 2 mo. Carbon budget analysis revealed that, based on carbon specific growth rate (% d-1) and food carbon conversion efficiency (%), the experimental treatments could be divided into 2 groups, diets 1-3 and diets 4-5. Carbon contributions of the 3 ingredients based on the stable isotope analysis suggested that C. linum and Z. marina were the main carbon sources for A. japonicus in the 5 treatments, and C. linum was a better food source than Z. marina. In addition, a new potential index, i.e. the ratio of carbon contribution to composition (RC_con:C_com), was constructed to assess the feeding preferences of A. japonicus; according to this ratio, the preferences for the 3 diet ingredients were: muddy sediment > C. linum > Z. marina in the 5 treatments. Compared to the carbon budget method, carbon isotope analysis could distinguish the feeding preferences of A. japonicus for the diet ingredients in each treatment and had the advantage of being less labor intensive; thus it was considered to be a better approach for measuring the feeding preference of A. japonicus.