Hooded Nudibranch Mating Season Begins

Late summer each year is the time Hooded nudibranch (Melibe leonina) migrate from deep water to the shallow eelgrass beds of Puget Sound to mate and lay eggs. During peak times, they can be seen by the thousands at dive sites such as Edmonds Underwater park and Redondo Beach. They can also be found as far north as Alaska and south to California.

Hooded nudibranch by David Sisson

Hooded nudibranch by David Sisson

Hooded nudibranch can reach up to 4” long with a round oral hood that is used to catch prey.  Their bodies are translucent, with a pale white, yellow, orange, or greenish tint and give off a sweet smell when taken out of water. During reproductive season in the late summer, they congregate in shallow eelgrass (genus Zostera) habitat, clinging to eelgrass blades. They are carnivorous, eating small fish & invertribrates such as copepods and zooplankton. Hooded nudibranch are in turn preyed upon by larger fish, Northern kelp crabs, and sea stars.

Hooded nudibranch are hermaphrodites, meaning they have both male and female reproductive organs. To reproduce, two Hooded nudibranch simply fertilize each others eggs. After laying their eggs, the Hooded nudibranch die off, leaving behind a new generation.

The best time for divers to see Hooded nudibranch is at the end of the dive, during a safety stop. Hover over the eelgrass bed at around 15’ and look down, inspecting the eelgrass for Hooded nudibranch clinging to the blades.