There are no sure tactics for catching tailing trout, in fact they are probably the hardest trout to consistently fool.
There are a few reasons as to why they can be so hard to catch, the first I suspect is that their head is mostly in the weed - they can't see your fly. Secondly, if they are on a bed of snails, amphipods or chasing stick caddis nymphs, then they may just have too many choices (your fly is another needle in the haystack). Thirdly, it doesn't matter how well you tie a fly, it still has a sharp piece of curved metal hanging out one end, and a piece of line tied to the other, so there's no such thing as exact imitation. With the water starting to warm, and levels rising, now is the time to start chasing the tails, so despite their complete unpredictability, here are some tailing trout tactics to try.
Tailing, finning and charging
The term tailing for most is used to describe any fish that has its fins out of the water, and as such it's meaning can be a bit vague. As a tactic, the best way to chase these "tailers" is to separate them in to three categories - tailing trout, finning trout and charging trout. At first they may all look the same, but in a plan of attack they can all be quite different.
A tailing trout is strictly speaking a trout feeding "head down and bum up" in shallow water, which results in its tail waving about in the air. This is really exciting fishing, but definitely the hardest of the three generic tailing situations. More often or not the fish is feeding on a concentration of snails, amphipods ("scud" or "shrimp') or stick caddis nymphs. These food sources are typically intermingled with fine weed and the fish are really focussed on the tiny prey. The general idea is to present the fly right on the nose of these fish without getting the fly weeded or spooking the fish. This is covered later in a bit more depth.
Finning trout are trout that are more or less cruising in shallow water with their backs or tails out of the water from time to time. These fish usually know what they're looking for, but they aren't feeding on a concentration of any particular food. Often they may be searching for stick caddis or other nymphs swimming around that they can intercept. Again a quick cast on their nose is the principle, but this time the odds are on the side of the angler since the fish doesn't have its head buried in weed.
Charging trout describes the third common situation that can be found with trout feeding in shallow water, with these fish more likely to be feeding on larger prey items such as frogs, baitfish or tadpoles. Bigger flies such as the fur fly can be used and accuracy is often not as important as with a true tailing trout.
The principle behind presenting a fly to any of these shallow water feeders is relatively simple. Firstly, work out in which direction the fish is feeding, the cast needs to go in front of the fish. A quick accurate cast is then required with a fly that imitates the likely food source. Let the fish swim to the fly, if it doesn't then start a very slow retrieve. A typical tailer, if it eats your fly, will shuffle with bum up over to your fly, taste it and then spit it out. To counter this you need bravery - you just have to bite the bullet and strike if you think the fish has your fly. If the strike is made and there's no fish, then instantly recast as all may not be lost (though it probably will be). It may take a dozen casts just to get the fish's attention, so be prepared to recast quickly and accurately with little or no false casts. In dead calm conditions lengthening the leader may help to prevent the fish spooking, and remember no wading if it can be helped as this nearly always spooks the fish. If the fish is spooked and doesn't charge away, wait for a few minutes and you might find that it comes back feeding again - they really are unpredictable.
Flies and leader set-ups
A tailing trout may eat any form of fly - wets, dries or nymphs. Generally the warmer the water the more likely that the dry will work if that is your preference. As mentioned earlier, the fly needs to be kept out of the weed so the fish can see it, this can be achieved in a number of ways. The most common method of setting up a leader to use on tailing fish is to hang a nymph 15-30 centimetres off of the hook bend of a dry fly such as a Royal Wulff (tie it on the bend with a blood knot). This gives the angler a strike indicator, and keeps the nymph out of the weed. A second similar tactic is to substitute the dry fly with a very small indicator such as wool or pinch on foam. This can be very useful for beginners as again it's easy to see if the fish moves the leader, and the fly is kept out of the weed. The third leader set up is to use a more traditional single fly approach, and grease the whole leader with the exception of the final 15 centimetres or so with Gink or Vaseline. The floating section of leader will hold the fly up out of the weed, and the angler can watch for the movement of the leader to signal that the fly has been eaten.
As usual with fly-fishing, trying to catch a tailing trout is more about presentation then it is about the fly, but there are some consistent catching patterns. Good patterns to try include the Black and Peacock Snail, Seals Fur Nymph, Clipped Woolly Worm and the Stick Caddis Nymph. If dry flies are your preference then a Black Spinner Parachute, Klinkhammer Special or an ordinary old Red Tag may do the job.
Locations and conditions.
Nearly every piece of slow moving or still water in Tasmania has tailing fish feeding at some stage or another in the season. Lowland hotspots do however include Brumby's Creek or any of the Northern Midland streams when in flood. Rising water levels on dull, still, overcast days can be ideal for Brumby's, as long as the Great Lake water is not too cold coming in from the tailrace. A snail or stick caddis imitation is probably the best bet. Little Pine and Bronte Lagoon, and the Western Lakes are the most renowned tailing fish waters in the Highlands, with all producing exceptional fishing in prime conditions. If the fish are tailing after small invertebrates then a snail, stick caddis or even a dry fly can work, whilst if they are chasing frogs or tadpoles or other fish, then a fur fly style fly can be the better alternative. The Road Shore is an easily accessible shore on Little Pine Lagoon where tailers after invertebrates can be found, whilst Tailers Bay as the name suggests is an easily accessible bay for anglers looking for tailing or finning fish at Bronte Lagoon. Ideal conditions for finding tailers in the highland lakes also revolve around calm conditions and overcast cloudy days, though in any of these locations tailing fish could be found at any time and in any conditions of the year - be on the look out in all the likely places, you may surprise yourself!
Persistence pays off
An example of how hard tailing fish can be to get the attention of, and how unpredictable they can be, occurred on Brumby's Creek in March. The fish was tailing against an undercut bank for over fifteen minutes. He was fished to the whole time with all manner of flies but in the end fell for a size 8 deer hair grasshopper pattern!
A few tailing trout patterns
Black and Peacock Snail (bead head optional)
Thread: 6/0 or 8/0
Ribbing: Fine copper wire
Body: 3-4 strands of peacock herl
Hackle: Soft black hen (Herbert Minor hackles preferably)
Seals Fur Nymph
Thread: 6/0 or 8/0
Tail: Brown hackle fibres (Coq de Leon saddles provide excellent tailing materials)
Body: Brown seals fur dubbed on a roughened up with Velcro
Ribbing: 3 turns of flat copper wire
Head: Brown seals fur roughened up with Velcro
Clipped Woolly Worm
Tail: Pheasant tail tippets
Hackle: Hen feather colour to suit (Herbert Minor hackles preferably)
Body: Variegated chenille (brown and green), or chenille to suit.