The months from November through to early March encompass the peak of sea-run brown trout activity at large South Island river mouths. The reason for this is simple – food.

They turn up to ambush schools of whitebait, smelt and ‘bullies which, when the tides are right, move into estuary and lower-river margins to spawn. In league with kahawai and terns, they cash in on the annual feast, and in turn anglers in the know can take advantage of their collective vulnerability.

Popular river-mouth areas to target these fish include Nelson, Marlborough, West Coast, North Canterbury, Central South Island and, where access allows, Fiordland. Rivers such as the Hurunui, Waimakariri, Rakaia, Rangitata, Hokitika, Waitaki, Clutha, Karamea, Mohikinui, Buller, Grey, Taramakau, Hokitika, Paringa and Haast are often mentioned in sea-run trout despatches.

Searun trout are an under-utilised quarry because their habits are different to resident trout, making them harder to catch, and the areas they feed in can be a difficult and dangerous environment to safely fish. They live in fast water in a tidal habitat, and because they are wired-in to eat mainly small fish, they tend to be active when the small fish are active. It is feast or famine with sea-run trout. When the small fish are absent, so are the trout. Or, if the small fish are present but not migrating, then the sea-run trout are nearby, too, lying doggo on the river bottom waiting for the dinner gong to sound.

Funnily enough, this stop/start feeding cycle affects all the other predators as well. When the small fish are quiet, only odd terns flitter around, while the dark-coloured kahawai school rests off the river-mouth with fins sticking out of the water. Only the inexperienced visitor anglers waste time casting lures into the listless water.

However, a pushing or falling tide, around dawn, dusk and after dark, or when the water is discoloured, all see sea run trout get active, because the small fish feel safer and are on the move at these times.

A watchful angler spots the signs. Diving terns, seagull activity, splashy surface swirls on the edge of the current, and loud plops in the distance, signify the estuary is now a killing field.

Sea-run trout are mainly caught in three ways: spinning, using popular lures such as the yellow-grey Tasmanian Devil or Rapala; drifted natural baitfish, such as smelt or bully; and lure fishing using specialised gear.

Quite often sea-run trout are caught by salmon anglers too, because trout and salmon are at the same location at the same time, and will hit zeddies and ticers on occasion in poor light. It is not uncommon to see three or four big trout landed right at dawn by salmon anglers fishing the river-mouth gut and surf. It always seems to be just in that first half hour; as the morning brightens, the trout disappear.

Often the angler thinks his or her catch is a salmon, because sea run trout can be big (up to 7kg) and, in comparison, the salmon have been small in recent years. Both species are silvery, but trout have a squarer tail, a white not black inner mouth, and spots that look like the letter X.

The first river rapids above the tidal push are popular spots for anglers to target sea runners, as they provide an obstacle to baitfish and allow ambushing to occur. If the water is really shallow, the chasing fish create impressive bow waves that end in a swirling explosion of water. Along the current edges is another popular ambush location. When the smelt are pouring upstream, the trout get very aggressive and slash rather than bite. Strikes are therefore savage. With so much action going on, you would imagine that every angler present has a bent rod and screaming reel. Not so. With so much food on offer, the fish don’t need to grab every offering. They can be choosy. But even if you are not catching fish, there’s lots to watch.

The most successful anglers fish after dark, and traditionally they catch the bigger sea-run trout. Invariably, these guys are lure anglers, using smelt flies, a monofilament line, a weight to get their gear down on the bottom quickly, and a specialist lure rod and reel.

A couple of articles ago I talked about the concept of drift; well, these guys are masters of drift. They flick out their weighted lure, let it swing through fishy water in an arc, then strip it upstream along the bank before repeating. When a fish hits, it is time for them to hang on and race off downstream after their quarry. In recent times, many lure anglers are using soft-baits as a substitute for flashy lures.

Tales of big, sea-run-fish battles don’t seem as common these days, however, and North Canterbury Fish & Game even closed down the lower reaches of rivers in their district over winter because fish stocks had taken a dramatic dip.

Anglers who fish for river-mouth sea-run trout during daylight hours struggle more, and tend to land smaller fish. These vary from very small up to about 2.5kg, with the medium ones making great eating due to the nature of their diet, their flesh being a reddyorange. Most are in superb condition.

While lure anglers talk of having a-dozen-fish-or-more sessions, my best using spinners would be three or four. Just when I think I’m getting good, I have a couple of dud trips to bring me back to earth. My best fish thus far weighed 4kg. While that’s a good fish, my second best weighed 2.5kg, so the big one was a flash in the pan. Obviously, lots of learning still required...