EVALUATING TUMBLE CULTURE AS A METHOD TO IMPROVE PACIFIC OYSTER (CRASSOSTREA [MAGALLANA] GIGAS) GROWTH ON SOUTHEAST ALASKA SHELLFISH FARMS
Date
2025-05
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
University of Delaware
Abstract
High water turbulence, tidal flux, and biofouling at Alaska’s high latitude
oyster farms create various challenges for growing marketable Pacific oysters
(Crassostrea [Magallana] gigas). As oyster mariculture expands in the upper Pacific
northwest, developing efficient oyster grow-out methods is critical to ensuring
industry success. Surface culture practices, also referred to as tumble culture, are
configured to move with surface wave action and be exposed during low tide, thus
naturally tumbling oysters, deterring growth of fouling organisms, and potentially
reducing husbandry demands. To evaluate the efficiency of tumble culture in creating
marketable oysters in Alaska where this method is not currently used, we stocked 48
SEAPA baskets with 500 individual seed oysters with an average total length of 26.2
mm ± 5.44 mm (mean ± standard deviation) and monitored growth over a four-month
period. The baskets were deployed in two configurations and tidal zones (intertidal
pivot line baskets and subtidal basket stacks) at a commercial oyster farm in Juneau,
Alaska in early June 2024, and compared to the farm’s existing floating mesh bag
method. Subsets of 20 oysters were collected in late June, July, and September 2024,
to monitor shell morphology (length, width, depth), as well as whole and wet meat
weights to determine differences in growth among the gear configurations and depth
strata. The results indicate that there was a significant effect of gear configuration on
oyster growth. Subtidal basket oysters had the highest shell growth, though growth
was thin and uneven. In contrast, intertidal basket oysters had slightly lower shell
growth but had high wet meat content, producing more market desirable shell shapes
compared to the other gear configurations. Oysters from the floating mesh bag method
had high percent wet meat weight relative to their whole weight, however, these
oysters had the slowest overall growth. These results suggest that gear configuration
and depth affect oyster growth, with the intertidal basket configuration producing
oysters with desirable shell shape and wet meat weight. Ultimately these results can
inform Southeast Alaska farmers about additional methods of growing oysters that use
currently under-developed intertidal lease areas and result in well-shaped oysters.