Gurnards are distinctive fish with large, bony heads and a sloping or concave face. They 'walk' on three 'feelers'...
Gurnards belong to a group of fish known as sea robins (Triglidae); they are related to scorpionfishes, which have similar large bony heads and tapering bodies. Much of the information I found was about grey and red gurnards, but the other species probably live in a similar way. Divers see gurnards most often on the sea bed, where they often spread their pectoral fins if threatened, probably in preparation for a quick getaway, but perhaps also to distract predators; the bright blue pectorals of the tub gurnard are startling when opened suddenly. Gurnards may occasionally be seen swimming in mid-water, using their large pectoral fins as gliders. In winter, they sometimes form dense aggregations just above the sea bed, when more than a thousand individuals may be caught in a single fishing net haul.
These fascinating fish use their taste-sensitive feelers to ‘walk’ across the sea bed, and to find food. Young gurnards eat mainly small crustaceans, especially shrimps and crabs, while larger gurnards also eat other fish. One of the most interesting features of gurnards is that they apparently ‘talk’ to each other while hunting for food. I’ve only observed them as single fish, but offshore they can form large foraging schools, when they apparently communicate by knocking, grunting and growling. The noises are made by vibrating the swim bladder, and may be the origin of the collective name of sea robins. In what must have been one of the more fun fish research projects, biologists reported that the grey gurnard ‘frequently emits knock and grunt sounds during competitive feeding, and seems to adopt both contest and scramble tactics under defensible resource conditions’. I think this means it either fights for it or grabs it first. The researchers interpreted ‘grunts’ as aggressive sounds and ‘knocks’ as less aggressive, and found that smaller fish grunted more, while larger fish made less noise and did proportionally more knocking!
Grey gurnards in the North Sea have a strong seasonal migration, which does not occur in other populations, so is thought to be related to avoidance of low water temperatures in the southern North Sea in winter. As the water warms up in spring and summer, the fish migrate southeast to spawn, releasing 200,000–300,000 tiny eggs that float in the water. The larvae hatch when they are 3–4mm long. Grey gurnards can live to nine years, while red gurnards can live as long as 21; females grow larger and live longer than males. Gurnards are commercially fished, usually as a by-catch in trawling.
BEAST AT A GLANCE
Most often seen on sandy sea beds, also on mixed ground.
BEST PLACE TO SEE:
Can be seen all round Britain.
LIKELY TO APPEAR:
Present all year but some populations have seasonal migrations. More active at night.
Gurnards are distinctive fish with large, bony heads with a sloping or concave face. They ‘walk’ on three ‘feelers’. The grey gurnard has a dark blotch on the edge of its first dorsal fin; the red gurnard is similar in shape but is reddish overall; tub gurnards have a peacock-blue edge and blue spots on their pectoral fins (young grey gurnard may also have a pale blue edge); streaked gurnard have larger blotched fins.
Grey, red and streaked gurnards grow to between 35-45cm; female tub gurnard can reach 75cm.