Oysters are key subjects in circatidal rhythm studies. They anchor to hard surfaces and are generally immobile. Scientists use specialized tech to monitor the opening and closing of their two shells, called 'valves,' during activities like feeding and spawning. These valves close during low tide for protection. Research methods: 1) Electrodes on each valve detect electromagnetic changes, logged onto a waterproof data card. 2) Power comes from mains, batteries, or solar energy. 3) Captured data details valve movements, including duration, frequency, and unique events like spawning. 4) The data undergoes analysis over different time frames—lunar, daily, tidal, annual—to yield insights into the oysters' rhythmic biology and behaviors.