The potential for proliferation of an invasive fanworm due to harvesting in mussel aquaculture.
Biofouling, including the accumulation of invasive non-indigenous species, significantly increases production and processing costs in shellfish aquaculture. Harvesting operations have the potential to exacerbate this problem through the fragmentation and discharge of biofouling species and by triggering the release of propagules that can subsequently re-establish in the vicinity. In this study, the potential for the proliferation of the invasive Mediterranean fanworm, Sabella spallanzanii, from harvesting operations in the aquaculture of green-lipped mussels, Perna canaliculus, was examined in New Zealand. The Mediterranean fanworm were experimentally fragmented and held on a mussel farm and in laboratory conditions. Wound closure in most fragments was observed within three days after fragmentation and most fragments had started regeneration of new body structures (new branchial crown or tail segment) within 14 days after fragmentation. Survival was higher for posterior fragments compared to anterior fragments, both in the laboratory and field conditions. Although, posterior fragment survival in the field was lower compared to the laboratory. The size of the fanworm fragment had no effect on regeneration or survival. A large number of fanworms stayed attached to the recovered grow-out rope after passing through the machinery to strip the mussels from the rope. Consequently, the rope and attached fanworms were retained on board the harvesting vessel for return to shore facilities for cleaning prior to reuse, precluding their release back into the sea. Only a small proportion of fanworms were processed through the mussel harvesting machinery with the majority sustaining several wounds, and were often bleeding heavily or were dead. Such injuries are known to result in the release of gametes from fanworm, however, only ripe fanworm sperm are known to be viable when released into seawater. Overall, the results of this study indicate that the potential for proliferation of fanworm from harvesting activities in mussel aquaculture is limited, and could be eliminated by the physical removal of waste material prior to discharge at sea.