The effect of high air and water temperature on juvenile Mytilus edulis in Prince Edward Island, Canada

Mussel aquaculture on Prince Edward Island (PEI), Canada, is an important but relatively new industry. Although seed manipulation using hatcheries for mussel culture occurs on the west coast of North America, seed supply on the east coast of Canada, including Prince Edward Island (PEI), is based solely on wild collection. Two techniques for culling seed (<10 mm) were studied in this experiment to look at the effect on productivity, measured as size, growth and survival. The separate effects of air exposure or high water temperature treatments on a sample of Mytilus edulis spat were examined in the lab and in the field. The in vitro treatments resulted in a similar to50% mortality from an air exposure of 11 h at 27 degreesC and similar to75% mortality from a 6-h exposure to 33 degreesC water. Survivors of each treatment (n=1152) were measured, along with controls (n=2304) and randomly placed in compartmentalized (condo) cages. Cages were deployed on a mussel farm in each of three bays on Prince Edward Island, Canada. Size, growth and survival were monitored over a 10-month period. After the initial treatment, survivors of the air exposure treatment were significantly (p<0.01) larger than the control. Survivors of the high water temperature treatment were smaller than the control (p<0.01). Results from the field study showed that the treatments had a significant effect on size, growth and survival. These results suggest that relatively simple husbandry practices of weeding out weaker mussel seed can affect productivity. Given the limited availability for lease expansion in PEI bays, new husbandry practices are an important avenue to investigate, in order for the mussel industry to maximize production capability. (C) 2004 Elsevier B.V. All rights reserved.