What does grey gurnard eat?

The grey gurnard has a feeding apparatus that nothing else on its ground possesses, and it is worth describing before the diet itself.

The three lowest rays of each pectoral fin are free of the webbing and act as independent, mobile, finger-like appendages carrying both touch and chemical receptors. The fish props on them, moves them ahead of itself over the seabed, and detects buried prey by feel and by taste before it can see anything. A gurnard genuinely walks over the bottom and genuinely tastes what it walks on.

The diet follows directly. The two verified relationships are decapod crustaceans — shrimps, prawns and small crabs — and polychaete worms, all taken from and just under the surface of clean sand and fine gravel. Small fish including sandeels and gobies are taken opportunistically, and the fish component rises with size.

Because detection is by contact and chemistry rather than by sight, a grey gurnard feeds as effectively at night and in coloured water as in clear daylight. That is a real advantage over the visual bottom feeders sharing the same ground, and it is why gurnards are caught at every state of light and water.

Hearing is developed too. Gurnards drum specialised muscles against the swim bladder to produce audible grunts and croaks, and a fish that calls is a fish that listens — though what role sound plays in feeding rather than in communication is not established.

The seasonal pattern is a depth shift rather than a change in diet: fish move shallower through summer and autumn and offshore in winter, feeding throughout.

Gurnards are mostly caught by accident, and the interpretation below is about turning that into something deliberate.

A STATIC BAIT ON THE SEABED matches the hunting method exactly, and that is the whole reason gurnards are so easy to catch: the fish walks over the bottom testing it, and a bait lying on the bottom is what it is testing for. Worm and fish strip are both conventional.

LURE COLOUR IS WIDELY HELD TO MATTER LITTLE, and the reasoning is the sensory profile: a fish that finds food by contact and chemistry is not making a colour judgement. This is practitioner inference from biology rather than a tested claim, and it is a good example of the kind that sounds like a fact.

MOVEMENT STILL WORKS. A small jig worked slowly along the bottom takes gurnards readily, which is usually explained as investigation rather than as feeding — something crossing the fish's ground is worth examining whether or not it resembles food. Also inference.

The handling consequence is not interpretation and is the most important thing on this page for anybody who has just caught one. The gill covers and shoulder carry sharp backward-pointing spines and the first dorsal is spiny; none is venomous and all of it punctures, and marine puncture wounds infect out of proportion to their size. Grip the fish across the body behind the pectorals with the dorsal folded flat, never sliding a hand forward from the tail.

Both relationships are group-level and neither establishes proportions. The fish component of the diet is substantial in larger individuals and is represented by no modelled relationship, because the sources describe it at a level of generality the precision rule will not accept as a species claim. Nothing here quantifies the shift in diet with size, and the role of hearing in feeding as distinct from communication is not established.