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Clamming and Oystering

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Climate Change Indicator


 The area of the Sound designated as prohibited or restricted for harvesting shellfish decreased in 2023.

The acreage of shellfish growing areas that are designated as “restricted”, which includes “prohibited”, “restricted relay”, and “conditionally restricted relay”  decreased by 4,942 acres in 2023 from the previous year. However, the area of “prohibited” shellfish growing areas, which is determined by bacteria contamination and is an indicator of poor water quality, actually increased by 632 acres from the previous year. Changes in the classification of shellfish growing areas are usually related to improvement or decline in water quality, based upon the results of water quality monitoring and/or updated sanitary survey findings. However, in 2023, changes in the classification mapping for shellfish beds that extended offshore of Madison was largely responsible for the reduction of 5,062 acres in the “restricted relay” category.44 The Connecticut Department of Agriculture's (DoAg) Bureau of Aquaculture (BoA) monitors water quality and classifies shellfish growing areas according to their potential for yielding healthful, uncontaminated shellfish. There is a total of approximately 390,000 acres of shellfish beds managed by the DoAg, BoA.

Water quality assessment criteria for shellfishing as a designated use only applies to inner-shore, and mid-shore estuarine waters where shellfish growth is viable, which is approximately 50 percent of Connecticut’s estuarine waters. Only about 20 percent of the estuarine waters identified as assessed in the 2022 Integrated Water Quality Report can fully support shellfish harvesting from Class SA waters.** Meanwhile, the percent of estuarine waters that can fully support shellfish harvesting from Class SB waters remains unchanged from the 2020 report at approximately 62 percent.45

Goal: The goal for marine shellfishing is to “upgrade 5 percent of the acreage restricted or closed for shellfishing in 2014 by 2035” (2015).46 The “restricted or closed” acreage in 2014 totaled 167,264 acres, which included areas designated by DoAg as “prohibited”, “restricted relay”, and “conditionally restricted relay”. Therefore, the goal is a reduction of restricted or closed acreage to 158,901 acres by 2035, shown on the chart as a gold horizontal line. 


Technical Note: *The vertical axis in the chart above has been shortened, beginning at 100,000 acres rather than the customary zero. **SA waters allow shellfish harvesting for direct human consumption where authorized, whereas SB waters allow shellfish harvesting with depuration or relay where authorized. Depuration is the action or process of freeing something of impurities. In the case of shellfish, this usually means moving the shellfish to areas with better water quality.



44  DoAg, Bureau of Aquaculture, personal communication with M. Zuber, December 22, 2023; portal.ct.gov/DOAG/Aquaculture1/Aquaculture/Aquaculture-Home-Page.
DEEP, 2022 Integrated Water Quality Report to Congress, p. 38; portal.ct.gov/-/media/DEEP/water/water_quality_management/305b/2022/IWQR-Final-2022.pdf#page=38.

46  Long Island Sound Study Comprehensive Conservation and Management Plan, 2015; longislandsoundstudy.net/our-vision-and-plan/.