Effects of Geoduck Aquaculture on Predation and Growth of Non-Target Clams

As aquaculture expands world-wide, it becomes increasingly important to determine the ecological affects of each aquaculture practice in a region. This paper examines the affects of Pacific geoduck aquaculture in Puget Sound, WA, USA on non-target Manila clams. Manila clams were planted in active geoduck aquaculture sites in South Puget Sound and non-farmed beaches nearby. A SCUBA survey of each plot was conducted to determine predator density differences between farmed and reference plots. Clams were retreived, counted and measured to determine predation and growth rates. Potential predators of Manila clams occurred in greater numbers in farmed plots than reference plots. Clam recovery was analyzed at each sites and showed lower overall survival rates for Manila clams at farmed plots. Similarly, growth rates for the non-target clams were slower at the farmed plots. These results suggest that geoduck aquaculture in Puget Sound provides an artificial habitat for predators and negatively affects the survival and growth of non-target bivalves.