Hard clam Mercenaria mercenaria aquaculture centered in Cedar Key, Florida, is a 30-year economic success story by any measure. Over 180 growers produce more than 90% of the state’s crop, supporting 430 jobs and $29.3 million in industry output. However, the past two years have brought unprecedented challenges from weather and climate-related events, raising growers’ concerns about the profitability and even sustainability of their operations in the face of climate change. Florida is particularly vulnerable to climate change due to its low elevation, geographic location, and landscape configuration. Further, shellfish aquaculture is particularly sensitive to multiple drivers including sea level rise (15 cm in 30 years), coastal habitat loss, and increased hurricanes and harmful algal blooms.
In August 2023, Hurricane Idalia made landfall near Cedar Key as a category 3 hurricane with a storm surge of 3.26 meters from MLLW, causing crop losses exceeding 75% with projected damages of $25.9 million. Even before the hurricane, growers reported substantial mortalities due to extreme temperatures. According to the NOAA National Weather Service, August 2023 was the warmest on record in the area; water temperatures at leases exceeded 32oC on 19 days in that month (Figure 1). Another heat wave in June 2024 affected new crops which were also vulnerable to lower salinities. Variability in rainfall has led to inconsistent river discharges resulting in additional water quality stressors during summer months. As recovery efforts from Hurricane Idalia were underway, the industry suffered a new setback in September 2024 when Hurricane Helene, a category 4 storm, made landfall in the same location with a surge of 3.99 meters.
Weather and climate adaptation strategies being considered include reducing clam densities and changing cultivation methods from bags to bottom plants, which would allow clams to bury deeper in the substrate. In the longer term, selective breeding efforts of clams for greater tolerance to higher temperatures are ongoing and may strengthen adaptive capacity. Growers may also adapt by shifting to other species, such as the eastern oyster, or new strains, such as a hybrid with the native clam Mercenaria campechiensis. Relocation of leases is unlikely. But climate change may lead to a shorter growing season and development of markets for smaller clam sizes. These strategies and future concerns will be discussed.