An estimation of the carrying capacity of a commercial mussel farm in Newfoundland

Abstract

The mussel industry in Newfoundland began in the early 1980’s. with the number of farms increasing rapidly over the next ten years. By the early 1990’s some of the farms had grown quite large, in excess of 100 hectares, and the industry was becoming concerned about the carrying capacity of some sites. -- This project was initiated to evaluate the carrying capacity of a commercial mussel farm, owned and operated by Atlantic Ocean Farms Ltd., in Fortune Harbour, Newfoundland. The site operators noted it was taking longer to obtain a market size mussel than it had in previous years. -- Over the two year study period, 1994-1996, mussels suspended at 2 m and 15 m and at opposite ends of the site were significantly different in shell length, dry tissue weight, dry shell weight and, in those near the surface, in condition. -- Chlorophyll-α, temperature, and salinity at 2 m were not significantly different at either location although both salinity and temperature at 2 m were significantly different than at 15 m. The site had a low current speed, <2 cm/s, low tidal flushing, and less than optimal chlorophyll-α concentrations with an annual mean of 1.6 µg/L. There were three different carrying capacity models used to determine an appropriate stocking density for the site: tidal volume method, food depletion approach, and food demand versus food supply. The stocking density present on the site, 65 x 10⁶ mussels in 1995, was more than two times the suggested stocking density based of these models. -- It is recommended the operators reduce density of mussels on the site and stock at a rate of approximately 14,000 socks annually or 35 x 10⁶ mussels (132 socks per hectare or 33 x 10⁴ mussels per hectare).