Effects of traditional fishing techniques on internal organ regeneration, physiology, and biochemistry in the tropical sea cucumber Stichopus horrens

The sea cucumber Stichopus horrens is an important resource in the Kingdom of Tonga. Domestically, there are two fisheries; one at a commercial scale and one for subsistence purposes. Both fisheries involve harvesting all viscera (digestive tract, gonads and respiratory tree) through a lateral body wall incision, although only the digestive tract and gonads are consumed. Under the right conditions the sea cucumber can survive organ harvest and regenerate the viscera. This study investigated the biochemical and physiological consequences of organ regeneration by comparing sham (longitudinal body wall incision without organ removal) and excised (internal tissues removed after incision) sea cucumbers to control (handled but not incised) animals. Biochemical measurements of lactate, glucose, and glycogen showed that body wall energy reserves were depleted in both sham and excised animals relative to controls at the Day 10 measurement. The presence of an energy substrate depletion in sham animals indicated an effect related to loss of body wall integrity, rather than internal organ regeneration. Although the regeneration of digestive and respiratory organs was rapid, oxygen consumption rate and ammonia excretion rate were unchanged in excised and sham animals relative to controls. These data suggest that S. horrens can survive the internal organ harvest associated with subsistence fishing and regenerate excised tissues rapidly. However, this comes at an energetic cost that is likely to affect growth and reproduction. Fisheries management measures such as the implementation of a minimum rest period between harvests may promote the sustainability of this important fishery.