The Mianus River Watershed Council and Town of Greenwich installed an underwater video camera at the Mianus Pond Dam near Rt. 1 in Cos Cob to improve the accuracy of counting fish that pass through the Mianus Pond Fishway in April 2009. The fishway, built in 1993, has allowed hundreds of thousands of anadromous fish such as alewives and blueback herring, collectively referred to as river herring, to swim upstream (over the Mianus River Dam) through an carefully engineered sluiceway with resting pools so that they can spawn in the freshwater habitat of the Mianus Pond and upstream habitat. The river herring provide a important base in the food pyramid of sport fishing for Long Island Sound. So its important to measure and monitor the success of river herring.
The Town of Greenwich has used an electronic fish counter installed in the fishway to count the number of fish that swim upstream and downstream through the fish ladder. The camera will help identify the species passing through the fishway as well as their direction and size. The Mianus River Watershed Council and Town an online streaming Web camera feed from the fish camera that is accessible during the migration season in early spring when water temperatures rise during the months of March to June. The link to the web camera can be found on the Town of Greenwich webpage which also provides additional details on the history, design and images of the fishway.  In addition to a fishway for river herring, the Mianus River Dam fishway has an eel pass to enable catadromous fish (eels) to wiggle up and over the dam through a net. Eels are not able to swim up through the fish ladder so a large fishing net is anchored to the dam to enable the eels to access freshwater. Eels have a live cycle that is the opposite of the anadromous river herring. Eels (catadromous fish) spend most of their lives in freshwater until they are sexually mature, then swim downstream, slip over the dam or swim down through the fish laddder and out to sea to spawn. Most American eels congregate in the south Atlantic Ocean to spawn. Baby eels drift with the ocean currents until that are able to swim and make their way back to freshwater and the Mianus River Dam to complete their circle of life by wiggling up and over the dam and swimming upstream as far as the can to find their preferred habitat.The fish camera was funded through a Long Island Sound Study Futures Fund (LISSFF) small grant in April 2009.