Rock Gunnel

Fascinating facts about the Rock Gunnel

• When Carl Linnaeus first described this fish in 1758, he called it Blennius gunnellus; the species was later designated as the type species of the genus Pholis.
• A fully grown rock gunnel can reach up to 30 cm, and the maximum published standard length is 25 cm (9.8 in).
• These fish hide in the intertidal zone and can survive out of water by breathing air when the tide goes down, often splashing around on wet rocks.
• From November to January, a female deposits a clutch of 80–200 eggs in a ball tucked beneath a stone or inside a bivalve shell, then guards the mass until the larvae hatch.
• Their range stretches from Labrador and Greenland down to Delaware Bay in the west, and from the Kanin Peninsula to the Bay of Biscay in the east, spanning both North Atlantic and Arctic waters.

At a glance

About the Rock Gunnel

The rock gunnel, Pholis gunnellus, glides through the coastal waters of the North Atlantic and the Arctic fringe with a body that betrays an eel-like silhouette, flattened, elongated, and capped by a long dorsal fin that stretches from just behind the head to the tail. Adults grow to about 30 cm, their skin shifting through a palette of yellow-green, brown, or even crimson, each dorsal fin marked by a series of nine to thirteen dark spots rimmed in pale. A modest head bears a protruding lower jaw and an upward-turned mouth, hinting at a diet of small crustaceans, polychaetes, mollusks and fish eggs that the gunnel snatches from the crevices of its rocky realm. It favors the shelter of rocks and algae from the intertidal zone down to depths beyond 100 m, using these hideaways to evade seabirds, predatory fish, and marine mammals. A surprising trait sets the butterfish apart: when low tide exposes its perch, it can linger above water, breathing air and splashing conspicuously as it darts beneath overhanging algae. In the colder reaches of its North American range, the gunnel retreats from the intertidal during winter, a seasonal migration that likely spares it from freezing air, while the female guards a ball-like clutch of 80 to 200 eggs beneath stones or empty bivalve shells until the larvae emerge, continuing the cycle of this resilient, yet often overlooked, shoreline dweller

More fish to discover

Browse Feravox