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Description:The Gulf of Maine is warming faster than 99% of the world’s oceans, threatening the livelihoods of thousands of Mainers who make a living from the sea. Marine resource diversification is essential for adapting to this rapid change and ultimately promoting economic resilience for Maine’s coastal communities. Manomet and our shellfish farmer partners tested the viability of quahog and oyster polyculture as a way to diversify shellfish farms by using the vertical space of the water column. Overall, we found that growing quahogs on an existing oyster farm as a crop diversification strategy does appear to be economically viable, although there are many factors that can influence production and revenue. For example, the mortality events observed on Winnegance farm in 2020 greatly reduced profits from 2017-2018 cohorts. Furthermore, our results indicate overall greater growth and survival for quahogs grown on the surface, rather than submerged beneath floating cages (although this can also vary by site). This could be an issue for farms with limited space that need to prioritize space for higher value oysters on the surface. Growing quahogs on the bottom may still be viable, but potentially more risky if mortality events occur. However, using the cost-revenue estimator, even the highest amount of mortality we observed (42%) would still result in a net gain of $2,800. Environmental factors that correlate with growth, such as temperature and chlorophyll content (i.e., food) are important considerations when selecting a site or considering adding quahogs to an existing site (i.e., warmer temperatures and higher chlorophyll concentrations promote faster growth). Further exploration and experimentation to determine how site variability impacts growth and survival is warranted.
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Rights Information:CC0 Public Domain
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Compliance:Submitted
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