Aquaculture America 2020

February 9 - 12, 2020

Honolulu, Hawaii

COMMERCIAL ROCK SCALLOP CULTURE: WHAT DOES IT HINGE ON?

 
Carolynn Culver*, Jonathan Davis, Brent Vadopalas, Molly Jackson ,  Andrew Kim,  Art Seavey, and Paul Olin
 

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.