More than 40 years ago, the purple-hinge rock scallop, Crassadoma gigantea, was identified as a candidate for marine aquaculture . Since that time rock scallops have been the focus of research along much of the North American West Coast. G rowers too have been experimenting with rock scallop culture either on their own when natural sets of seed have been available and/or in collaboration with researchers . Despite all the interest and effort, rock scallop culture ha s eluded commercial production leaving some to question whether its culture is just a fantasy.
To help move rock scallop culture closer to commercialization, we addressed two remaining bottlenecks: lack of commercial quantities of seed and the development of cost effective grow-out techniques . Specifically, w e conducted trials to improve diploid production and develop triploid induction protocols . During this process, w e found that scallops recently collected from the wild could be readily spawned using serotonin, but some that had been held in the laboratory for more than 3-4 weeks could not. Further, those that readily spawned did not always produce viable eggs as determined from a lack of successful fertilization or development . As a result, there was only one fairly robust spawn ing event, with about 12,000 diploid seed produced. These s eed were settled on artificial seaweed with a diffuser that provided aeration and increased water flow. While triploid seed production was not achieved, several techniques were tested informing future work.
F actors associated with the rock scallop cementing stage, when scallops permanently attach to substrates, were also examined . Cementation can hinder commercial growout when scallops cement to the culturing gear, often damaging both the product and gear during harvest. We expanded our previous work on this issue and confirmed that: 1) the cementing behavior is primarily exhibited over a certain size range, 2) cementation can be inhibited through occasional disturbance in some locations, 3) shell growth and adductor muscle size is enhanced when scallops are attached, and 4) continuous attachment is not required for good adductor muscle growth . This means promoting or inhibiting (when possible) attachment may result in good growth and survival, and the manipulation may be required for only a small window of time thereby reducing costs associated with it. However, whether and how to manipulate the cementing stage will depend on the culture system used and related environmental conditions.
Based on this work, remaining issues with rock scallop culture include: broodstock conditioning to achieve reliable gametogenesis, identification of suitable conditions for metamorphosis, and, to a lesser extent, refinement of grow-out techniques. Overcoming regulatory hurdles with use of diploid seed in the vicinity of wild populations (possible use of triploids) and harvesting scallops during harmful algal blooms also require additional attention in some areas. Careful experimentation in these research areas will undoubtedly solve the remaining hurdles of commercial scale rock scallop culture, such that it will become a reality.