Rock Gunnel

The Rock Gunnel (Pholis gunnellus) is a small, eel-like fish in the family Pholidae, common along rocky shores of the North Atlantic on both the European and North American sides. It is a characteristic inhabitant of the intertidal zone, frequently found hiding under rocks, in crevices, or among seaweed in tide pools at low tide. Its slender, laterally compressed body and row of pale-ringed dark spots along the dorsal fin make it distinctive among small shore fish. Rock Gunnel is abundant and not of conservation concern, playing an important role as prey for shorebirds and larger fish in intertidal food webs.

Identify the Rock Gunnel by:

• Slender, laterally compressed, eel-like body reaching about 10-25 cm
• Olive-green to reddish-brown coloration that can shift to match surroundings
• A row of 9-13 dark round spots, each ringed in white or pale color, along the base of the long dorsal fin
• Long, low dorsal fin running nearly the full length of the body
• No pelvic fins
• Small, pointed head with a slightly upturned mouth

The dorsal fin's ringed spot pattern is the clearest way to distinguish it from other small eel-like intertidal fish such as blennies.

Rock Gunnel is found along rocky, seaweed-covered shores of the North Atlantic, from the eastern coast of North America to the coasts of Britain, Scandinavia, and northern Europe. It is a classic intertidal species, most commonly encountered under rocks, in tide pools, or tucked into crevices and seaweed holdfasts, especially at low tide. It tolerates significant fluctuations in temperature, salinity, and oxygen typical of the intertidal zone, and can survive brief periods of air exposure by remaining moist beneath rockweed. Its depth range extends from the intertidal zone down to a few tens of meters in the shallow subtidal.

Rock Gunnel is a secretive, mostly nocturnal forager that spends daylight hours hidden beneath rocks or seaweed, emerging to feed on small crustaceans, mollusks, and worms as the tide covers its habitat. Its flexible, eel-like body allows it to wriggle into tight crevices for shelter from predators and from the physical stresses of the intertidal zone, including temperature swings and wave action. It shows a remarkable tolerance for brief air exposure, remaining damp and inactive under cover during low tide. Spawning occurs in colder months, with adults coiling around clusters of eggs deposited in crevices or empty mollusk shells, guarding them until hatching.