34 SEPTEMBER 2012 dynamics, mooring components and tensions and operability has been summarized (Rice et al. 2003, Fullerton et al. 2004, Horton 2008, Turmelle et al. 2009). In parallel with engineering studies, aquaculture production experiments were conducted (Chambers et al. 2007). Growth studies using various feeds were conducted with Atlantic halibut (Hippoglossus hippoglossus), Atlantic cod (Gadus morhua), haddock (Melanogrammus aeglefinus), summer flounder (Paralichthys dentatus) and steelhead trout (Oncorhynchus mykiss) (Howell et al. 2005, Chambers and Howell 2006). Fish distribution in cages, swimming speed and feeding behavior were measured using acoustic tags and hydrophones (Rillahan et al. 2009). Operational methods were also developed for open sea, live harvesting of cod (Chambers et al. 2003). Maintenance The most time-consuming maintenance procedure was the annual removal of mussel biofouling on grid lines and flotation elements. This cleaning process required two scuba divers to do 4-6 dives (2-3 days of operation, depending on duration under water). Occasionally zinc anodes were added to steel subsurface floats for corrosion protection. No anchor alignment procedures or line or float replacement was necessary following the initial deployment. Recovery and Inspection In June 2010, the submerged mooring was recovered and inspected. In general, the deployed gear was in good condition. Two of 12 anchors had excessive material loss from corrosion on the tips of flukes but this did not threaten the operability or integrity of anchors. The ground chain was in good condition. However, the portion of the chain nearest the anchor line attachment had greater wear and material loss (2-3 mm) compared to the remainder of the chain. Anchor and grid lines fouled heavily with mussels, but with minimal fraying along most of their length. Line fraying was observed around thimbles at rope ring connections (Fig. 7), mostly in the northeast quadrant of the grid, the dominant storm wave direction. The connection between the anchor line and anchor chain did not fray. Therefore, it is assumed that relative motion, present at the grid level, caused some wear between the line and rope rings. Subsurface floats were in good condition, with little wear, and were structurally sound. More details of post-deployment assessment of the grid are provided in DeCew et al. (2010 b). Summary A submerged grid mooring was deployed for seven years at an exposed site off the northeast coast of the United States. FIGURE 4. Significant wave heights recorded at the site during spring 2007. A 50-yr storm event occurred on 16 April. FIGURE 5. A selection of cages deployed at the site. Clockwise from top left: SeaStation cage, Aquapod net pen, prototype gravity system and an OCAT cage.
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