Growth and performance of blue mussels (Mytilus edulis) exposed to effluents from cod (Gadus morhua) aquaculture in Norway

Abstract

Fish farming produces excess particulate matter from uneaten feed, faeces and excretion products. The sustainability of this industry is dependent on minimising impact on the surroundings. Two nine-month growth experiments were carried out in the laboratory and the field to examine whether blue mussel (Mytilus edulis) could improve growth by exposure to these nutrients from Atlantic cod (Gadus morhua) aquaculture on the West Coast of Norway. In the laboratory, the growth of mussels exposed to pure inlet water or waste water from tanks with cod production were compared. In the field, lines with blue mussels were placed in a mussel farm and a cod farm, respectively. Growth was evaluated by shell length, live weight, meat yield, soft tissue dry matter and condition index. In the laboratory, mussels grew faster when exposed to waste water from the cod. Shell length, meat yield and soft tissue dry matter were significantly higher compared to mussels receiving pure inlet water. In the field, there was no difference in mussel growth performance after nine months, but a higher degree of new settlements at the mussel farm. Mussels showed higher growth in the field. Attachments by byssus threads were strongest in the field and in the mussels exposed to outlet water. The mussels exposed to inlet water seemed more mobile and did not develop strong byssus threads