Northern Tidewater Goby
Male northern tidewater gobies burrow into sand and mud in the spring, cementing together grains of sand with a mucous, and shutting the burrow off from the waters above with a mucous and sand plug. Females will become aggressive during the spring and fight over a potential mate, slapping each other with their tails and biting when posturing is insufficient to drive their rivals away. The female will then attempt to entice the male to open his burrow.
If the female is successful (which may be infrequent - Camm Swift reports that 23 observed courtships resulted in only a single successful entry into the burrow by the female,) she will lay eggs on the burrow's sides and roof. The male protects the eggs for 9–10 days before they hatch. Although their life expectancy is not well known, tidewater gobies may live for only a year.