Two species of fish have been found at Younger Lagoon. One of them is an endangered species called the Tidewater Goby, Eucyclogobius newberryi, and can only live in highly disturbed environments.  The low oxygen levels and varying salinity of Younger Lagoon are a perfect match for this fish.  

The other species, the Threespine Stickleback, Gasterosteus aculeatus, has been found in previous years at the Lagoon, however is not known to be currently breeding or living there.