Utilizing the waste stream: Determining the suitability of the sea cucumber Stichopus mollis for co-culture with Greenshell mussels.

[Extract] The Greenshelf (TM) mussel (Perna canaliculus), is the dominant aquaculture species in New Zealand, accounting for ~60 percent of domestic aquaculture production. The technique used to farm Greenshell mussels in New Zealand is the Japanese longline technique where a continuous rope dropper is hung from double backbone ropes supported by surface buoys (Figure 1). Currently, 4,500 ha of coastal area is occupied by mussel farming activities in New Zealand and with increasing expansion, this may exceed 20,000 ha by 2025. The GreensheIl (TM) mussel, like many other bivalves, is a suspension feeder, consuming phytoplankton and other particulate matter that it filters from the water column. A single mussel is capable of filtering up to 300 L per day. Because mussels are highly efficient at removing particles from the water, they, in turn, produce a large amount of fecal waste. For example, the average mussel farm is stocked with mussels at around 150/m2 of seafloor and each mussel produces about 230 mg of waste each day, which translates to 35 g/m2 of mussel waste per day. The enormity of this waste production becomes evident if the amount generated is calculated over a year: 125 t/ha/yr of mussel feces.