Survivorship and growth of the sea cucumber Australostichopus (Stichopus) mollis (Hutton 1872) in polyculture trials with green-lipped mussel farms

Abstract

The suitability of the common New Zealand sea cucumber Australostichopus mollis to polyculture with green-lipped mussels was investigated in a six-month field study. Sea cucumbers were caged at three densities (2.5, 5 and 15 ind m⁻²) on the seabed beneath an operating mussel farm and survivorship and growth (weight change) monitored on a monthly basis. The sea cucumbers transplanted to below an operating farm showed excellent survivorship (91.7% overall) over the period of the study and exhibited growth at densities exceeding observed natural densities. Growth was density-dependent and at the highest densities appeared to be constrained by food limitation. A. mollis held at 2.5 and 5 ind m⁻² gained 15.37%±5.33 (mean±SE) and 13.16%±3.42 of their pre-caged body weight, respectively, while those caged at a density of 15 ind m⁻² showed a 0.21%±2.12 weight loss over the sixmonth trial. In addition, the acceptability of mussel farm-impacted sediment as a food source was investigated in tank-based feeding experiments with wild-collected A. mollis. Adult A. mollis readily consumed mussel farm-impacted sediment in laboratory feeding experiments, consuming 6.70 g±1.59 (mean±SE) wet weight mussel sediment d⁻¹. These results clearly indicate that A. mollis is an ideal candidate for polyculture with green-lipped mussel farms.