Date of Award

Winter 1-20-2023

Document Type

Thesis: Open Access

Degree Name

MS Marine Science

Department

Environmental and Ocean Sciences

Committee Chair

Theresa Sinicrope Talley

Committee Co-Chair

Drew Talley

Committee Member

Jeff Crooks

Committee Member

Carolynn Culver

Abstract

With demand for sustainable sources of seafood on the rise, California is looking to expand aquaculture with a focus on innovative culturing methods and use of native or resident species. Therefore, this study examined the potential for culturing native North American west coast venus clams (Chione californiensis and Chione undatella) using integrated multi-trophic aquaculture (IMTA). An ITMA approach was chosen because it is a culture method that uses species from different but functionally complementary trophic levels that have been found to reduce the potential negative effects of traditional monoculture. California sea cucumber (Parastichopus californicus) and the seaweeds red ogo (Gracilaria -Gracilariopsis complex) and sea lettuce (Ulva spp.) were chosen as the detritivore and nutrient extractors for the system. Clam performance (mortality and growth) was evaluated through both a controlled aquarium (March 19- August 2, 2021) and a bay (June 25 to December 10, 2021) growout experiments. The aquarium experiment had four treatments 1) Clam Only, 2) Seaweed Only, 3) Clam and Seaweed 4) All Three Species) with four replicates each. The seaweed-only treatment was established to elucidate mechanisms underlying observed patterns in clam performance (e.g., to reveal the potential influence of seaweed on water parameters). However, the seaweed did not perform well and there were no observed differences in water parameters between treatments in the recirculating aquarium system so four slightly different treatments were tested in the bay: 1) Clam Only, 2) Clam and Seaweed, 3) Clam and Cucumber, 4) All Three Species, with each treatment represented in one of four bins in a floating aquaculture system in San Diego Bay. Clam growth did not differ between treatments in the aquarium with an average of 1-5% growth in length and weight, and low mortality (≤2 deaths/aquarium/4.5 months) across all treatments. In the bay, clams in the Clam Only treatment experienced 1.5-3x faster growth rates than the treatments in the other bins. Average mortality was similarly low across treatments in the bay (≤3 deaths/treatment-bin/6 months). While the IMTA treatments were not found to increase clam growth compared to monoculture, there were other benefits of culturing multiple species together, primarily a reduction in fouling and increased cleanliness of aquaria and treatment bins. Therefore, the results indicate that the implementation of an IMTA growout may require a tradeoff analysis, as IMTA does diversify product and has the potential to reduce cleaning and maintenance efforts but may not improve species growth. While the clams grew more when cultured alone than with other species in this study, further studies using different species, locations, growout system sizes, and/or time scales are necessary to determine a wider range of outcomes likely to be observed in experimental and production-scale aquaculture operations across the region.

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