The ability of the deposit-feeding sea cucumber Australostichopus mollis to use natural variation in the biodeposits beneath mussel farms

The feeding biology and ecology of juveniles of the Australasian sea cucumber, Australostichopus mollis are not well understood. A better understanding may provide useful information for the development of the aquaculture of this species. Currently, A. mollis is being co-cultured beneath mussel farms and it is not clear if it can effectively use the wide natural variation in the food availability typically found under mussel farms. In this study the feeding and growth of juvenile A. mollis, was examined on feeds containing different levels of mussel, Perna canaliculus, biodeposits, resulting in different levels of total organic matter (TOM) (1, 4, 12, and 20%) covering a range similar to that found beneath a typical mussel farm in New Zealand. As the TOM content increased in the food from 4% to 20%, the ingestion rate of sea cucumbers decreased and both the apparent assimilation and food conversion efficiencies increased. There was no significant growth of sea cucumbers in the 1% TOM feed treatment, while sea cucumbers in the remaining treatments had similar final wet weights with a combined mean daily specific growth rate of 0.6% d− 1. These results demonstrate the ability of this species to use different levels of TOM to generate similar growth rates mainly by changes in their feeding behaviour and digestive physiology. These changes in their feeding biology together with the spatial and temporal variation of food availability in the sediments impacted by the mussel farm need to be taken into account when selecting suitable mussel farms for co-culture, as well as when defining the initial stocking biomass of sea cucumbers.

► Feeding and growth was evaluated in juvenile sea cucumbers fed with mussel waste.
► Feeding behaviour and growth of sea cucumbers depend on the food availability.
► Sea cucumbers are able to cope with the food variation only until a certain level.
► The possible implications for co-culture with mussels are discussed.