Utilization of different seaweeds (Sargassum polycystum, Sargassum thunbergii, Sargassum horneri, Enteromorpha prolifera, Macrocystis pyrifera, and the residue of M. pyrifera) in the diets of sea cucumber Apostichopus japonicus (Selenka, 1867)

Abstract

The sea cucumber Apostichopus japonicus is an important aquaculture species in China, which is fed mainly macroalgal powder. The algae Sargassum polycystum and Sargassum thunbergii are the most commonly used, however, these resources have decreased in recent years. In order to find new algae species as substitute for Sargassum, a 60-day experiment was conducted to examine the effects of different algae ingredients (S. polycystum, S. thunbergii, Sargassum horneri, Enteromorpha prolifera, Macrocystis pyrifera, and the residue of M. pyrifera) on the growth, body composition, and digestive enzyme activities of sea cucumbers. They were fed with six types of diets with either one of the five macroalgae or M. pyrifera residue mixed with sea mud. The results showed that the body weight of sea cucumbers fed on each diet increased significantly during the trial (P < 0.05). Sea cucumbers had higher specific growth rate (SGR) when fed with S. horneri (1.31% day−1), S. thunbergii (1.25% day−1), S. polycystum (1.04% day−1), or E. prolifera (0.83% day−1) than when fed with the M. pyrifera (0.55% day−1) or M. pyrifera residue (0.50% day−1). The ingestion rate (IR) was much higher when fed with M. pyrifera (1.1 g g−1 day−1) or M. pyrifera residue (1.5 g g−1 day−1) than when fed with S. thunbergii (0.48 g g−1 day−1), S. polycystum (0.5 g g−1 day−1), S. horneri (0.58 g g−1 day−1), or E. prolifera (0.65 g g−1 day−1). The nutritional compositions and digestive enzyme activities in the body of A. japonicus reflected those of corresponding diets, but the content of essential amino acid kept in a relatively constant state among different treatments. S. horneri and E. prolifera are novel supplementary nutrient sources for sea cucumbers and may be used by aquacultures.