Schist rocks, still water and well-conditioned trout are a good angling mix, writes southern contributor Greg Morton.

In the rock-strewn high-country hills behind Central Otago towns such as Ranfurly, Omakau, Alexandra, Clyde and Roxburgh, there are several large irrigation reservoirs. Wilderness basins were drowned decades ago to save precious winter and spring water, and as well as storing water, each dam also provides a rocky home for either brown or rainbow trout.

The dam list is long, and I have visited the following over the years: Falls Dam, Fraser Dam, Onslow Dam, Poolburn Dam, Upper Manorburn and Lower Manorburn Dams, Conroys Dam and Butchers Dam.

Trees are scarce at high altitudes, so dam trout depend on wind-blown tussock and matagouri forage items such as beetles, grasshoppers, blowflies, cicadas, and spiders; along with water-based prey such as cockabullies, snails, nymphs, midges and crayfish. Food opportunities such as frogs, tadpoles, worms, and mice are also never turned down.

Rocky irrigation dams provide good crayfish habitat.

Freshwater crayfish, or koura, thrive in these rocky habitats and a couple of the dams named above once had large populations. Sadly, those heady days are gone due to over-harvesting, but there are enough survivors still around to keep the resident trout happy. Trout with a heavy koura diet often have flesh that is a deep orange or rich red colour. They taste wonderful.

Catching crayfish-eating trout in rocky habitats calls for gear that imitates how the real crustacean lives, moves and feeds. There are two species of freshwater crayfish in New Zealand with the larger southern crayfish living in my patch. They hide in cover or under rocks during the day and are most active just before dark and during the night through to dawn. Freshwater crayfish like clean, well-oxygenated water and Otago’s windy backcountry dams tick their needs boxes.

They live hidden away but if caught out in the open during the day, they use their tail to propel themselves backwards in short spurts into cover such as an overhang, weed bed or under a rock shelf. They defend themselves with their claws and pincers and are clothed in a tough, armour-like outer covering. They face any enemy who approaches with claws raised and rely on their brown camouflage to stay undetected. Night is the best time to fish as both the crayfish and largest trout are out and about – if night fishing is not your thing, then focus your efforts during the day on murky water, overcast clouds or dawn or dusk.

An irrigation dam trout snagged on a grub soft-bait.

Koura scavenge and hunt on the bottom. While worm angling as a kid, I often noticed small tugs on my rod and then later found my gear snagged because a cray had grabbed the worms and retreated with them under a rock. Occasionally a crayfish was retrieved back to shore hanging onto the worms and hook. What was even more interesting at the Upper Manorburn Dam was that occasionally when retrieving worm gear, a rainbow trout would whack the worms being retrieved and get hooked. I imagine these trout thought the wiggling worms were an escaping crayfish and went into attack mode.

These days I have a range of gear I use when fishing crayfish water. The accompanying photograph shows most of them. They fall into four categories:

• Marabou or Woolly Bugger Jigs

• Generic Aquafoil lure

• Generic spinners

• Lifelike imitations.

Lightly weighted dressed jig head lures can be used to represent swimming crayfish. The jig should be fished down deep, retrieved very slowly, stop/started with small twitches, and allowed many pauses. It should be retrieved as a crayfish would act, either fleeing in short spurts or diving for cover. I often add a trailer imitation to the jig hook.

Aquafoil lures are the journeyman trolling lures of any tackle box. The most common ones down my way are the Tasmanian Devil and Tillins, but I prefer the action and look of the Johnson Super Kobra. This lure darts erratically on the retrieve and, in the brown colour, looks like an escaping crayfish. It is an all-rounder lure that represents all fleeing forage items. I use the 13g lure, which casts well, tracks deep, and has caught many trout, both brown and rainbow. The only downside is that it is heavy, so in shallower water, I use spinners, jigs and imitations.

A collection of crayfish imitation lures.

Spinners are also generic lures that represent many moving food types. The two brands I use in crayfish waters are the brown/yellow Panther Martin when the water is deeper and the brown Mepps Thunder Bug when it is shallower. The latter has a dressed hook as this addition looks a bit like trailing pincers in the water. I wind both slowly.

The last category is expanding wildly out there in the world of tackle innovation. The 3D imitation creations available are so realistic it looks like they can swim, breed and feed. I have added the Z Man and Savage offerings to my line up, plus various soft-bait grubs that look a bit like fleeing crayfish in the water. The grubs have caught many fish this year in crayfish dams so I can only assume the dark-coloured ones are mistaken for koura. When fishing these lures you cannot wind too slow but you can wind too fast.

The game changer when using the jigs and imitation soft-baits has been my new Tansui rod – matched with a 2000 Daiwa reel, it allows me to cast light stuff a long way, retrieve them oh-so-slowly, feel every touch and nibble, and handle hooked fish easily. Crayfish are a big food item, so you always have a chance for a trophy fish on koura imitations.

February 2023 - Greg Morton
New Zealand Fishing News Magazine.
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