USE OF MUSSEL FARMS FOR ON-GROWTH OF AMERICAN LOBSTER, HOMARUS AMERICANUS  

Mussel (Mytilus edulis) farms in Newfoundland, Canada were investigated as potential sites to hold adult lobsters Homarus americanus in inshore benthic cages (Fig. 1). The goals of this project were 1) to determine if lobsters can be maintained for prolonged periods in cages and survive and grow larger by feeding on mussels dropping off of culture lines, and 2) to determine if lobsters can be incorporated into a multitrophic aquaculture operation as a means of removing moribund mussels that might otherwise stagnate on the seabed. The effects of biotic and abiotic factors on the moulting, growth rates and serum protein concentrations were monitored at regular intervals in both the field and the lab over a 6 month period. Although survival rates were high under mussel lines (> 95%), the moulting rate was relatively low (13%) and analysis of serum protein concentration showed they were in a poorer condition than fed lobsters in the lab experiments. In the laboratory diet type, temperature, feeding frequency and compartment size were manipulated to determine possible factors influencing survival and growth of the lobsters in the field. In the lab, moulting was highest at 15̊C and survival lowest at 5̊C, and lobsters fed a mixed versus a mussel only diet were healthier. In a separate lab experiment, lobsters that were fed twice weekly grew larger than those fed once per month. However, feeding frequency did not affect survival or the number of animals that moulted. The lab experiments suggested that the combination of low temperature and infrequent food input was the likely cause of the low moulting rate and overall quality of the lobsters in the field.

This project showed although lobsters can be stored in benthic cages in the field for up to 6 months, relying on mussel drop-off alone is limited, and lobsters may need supplemental feeding in order to produce a larger, higher quality product for market. Initial results also suggest the promise of incorporating lobsters into a multitrophic aquaculture system as a means to remove mussel drop-off underneath culture lines.