Silver trevally

Silver trevally occupy coastal and shelf waters around southern Australia and New Zealand, and they use more of the water column than their reef-associated relatives.

THEY SCHOOL IN OPEN WATER OVER REEF AND SAND, from inshore bays out onto the shelf, generally from a few metres down to a couple of hundred, with larger fish deeper.

REEF EDGES, PINNACLES AND CHANNEL EDGES concentrate them, but the fish occupy the water above and around structure rather than sitting in it — a school of trevally over a reef is a midwater mark.

CURRENT AND TIDE ARE PART OF THE HABITAT, with schools holding where flow concentrates the zooplankton and small invertebrates they feed on.

THEY ARE PLANKTON AND SMALL-INVERTEBRATE FEEDERS more than piscivores, which distinguishes them from the tropical trevallies and explains the schooling, midwater habit.

JUVENILES USE ESTUARIES AND SHELTERED BAYS as nursery habitat in numbers, and are a familiar small fish around jetties and harbours before moving offshore.

TEMPERATE WATER IS THE REQUIREMENT — this is a cool-water carangid, and its range and abundance are set accordingly.

AND THE SPECIES IS LONG-LIVED AND SLOW-GROWING for its size, which is a poor combination with a schooling habit: schools are easy to locate and remove, and populations recover slowly, which is why several stocks carry management attention.

A shoaling mid-water fish that feeds on small crustaceans and baitfish over reef, sand and around structure, and the methods reflect a fish that is neither strictly a bottom feeder nor a surface hunter.

LEDGERING with small baits works because the fish feeds close to the bottom over open ground, and because trevally shoal — so a static bait in the right place reaches many fish rather than one.

JIGGING works over reef and structure, where the fish holds in mid-water and responds to a small fast lure.

SPINNING covers the same fish from shore around harbour walls and rock.

THE PRACTICAL POINT. Trevally are shoal fish with small mouths relative to their fighting ability, so the common mistake is tackle that is too heavy and hooks that are too large. Scaling both down usually transforms the fishing, which is the opposite instinct to the one the fight encourages.

Silver trevally combine a directional cutting hazard with a food-quality problem, and both are decided in the first minute after landing.

THE SCUTES ARE THE INJURY. Like every carangid, silver trevally carry a row of hardened keeled scales along the rear lateral line, and like every carangid they are safe stroked one way and sharp the other. A hand sliding from tail to head meets them edge-on and is cut. The grip that avoids the whole problem is across the body FORWARD of the scutes, ahead of the second dorsal, where the flank is ordinary scaled fish.

THE MOUTH IS SMALL AND UNARMED — trevally feed on small crustaceans and fish taken by suction rather than by seizing — so unhooking is a matter of a tool reaching a small space rather than of keeping fingers out of anything dangerous.

AND THE FISH'S REPUTATION AS FOOD IS DECIDED BEFORE IT REACHES THE ICE. Silver trevally have dark, well-vascularised muscle along the flank and a high metabolic rate, and a fish left to die slowly in a bucket in the sun with its blood in it produces flesh that is soft, strongly flavoured and unattractive. The same fish bled at once — a cut through the gill arches, into water, so the heart pumps it out — and put straight onto ice is a genuinely good eating fish. That single difference accounts for essentially the whole gap between people who rate this species and people who do not.

WHICH MAKES THE DECISION THE THING TO GET RIGHT: decide whether a fish is being kept or returned at the moment it is landed. A fish for the table is bled and chilled immediately. A fish for release goes back immediately, handled from head to tail, without ever entering a bucket. What ruins fish is the third option, where they sit in the bottom of the boat while somebody decides.