Two fly river fishing - twice the fun
The Hedged Bet
Fishing two flies is often referred to as hedging your bets - typically the leader will consist of a buoyant dry fly such as Royal Wulff tied on the end of the tippet, and tied between 30 and 60 centimeters off its hook bend will be a nymph such as a Pheasant Tail nymph. If the fish are feeding off the of surface, then the fish may take the dry, however, if the fish is feeding below the surface, such as trout feeding on nymphs, the fish will probably take the nymph trailing below the Wulff, hence the reference to a hedged bet.
The tandem nymph and dry rig is easy to fish, and doesn't result in too many more tangles than usual, but the results can be a lot more spectacular than the solitary dry fly. On small streams such as the St Patrick's river catches can be three or four times higher then they would be with a single dry fly. Earlier in the season before any serious hatches begin, or before the terrestrials such as grasshoppers start hitting the water, the tandem rig is again quite often a more successful tactic than the single dry fly. Tailing trout are a third opportunity for the tandem rig to perform, as the buoyant dry fly can act as an indicator for those minute takes that some tailing fish can produce.
Building the two fly rig
The two fly rig is very easy to build, consisting simply of a tapered leader, some tippet material and three Half Blood knots, which is the most common knot used to join the fly to the leader. (Geoff Wilson's Encyclopedia of Fishing Knots and Rigs has the full instructions to this knot and just about any other fishing knot known to man).
First of all the dry fly is tied on to the end of the tapered leader using a Half Blood knot. This top fly should be buoyant to hold up the nymph, and fairly visible for when it is drawn down by a fish taking the nymph. Ideal dry flies for this purpose are Wulffs, Humpies and Stimulators.
The second step is to determine how deep you would like the nymph to hang. On a typical Tasmanian stream, to achieve the desired depth the tippet should be almost twice the length of the depth your trying to fish. For example, if you would like the nymph to be 15 centimeters down, then try a 30 centimeter dropper, and for a 30 centimeter depth, try a 60 centimeter dropper. This technique is limited to a 60 centimeter dropper, any longer and it becomes quite hard to cast and fish effectively. Once you have determined your desired dropper length, tie this dropper to the hook bend of the dry fly with a half blood knot. As opposed to loch style fishing, the nymph or second fly is attached directly to the first fly. The leader materials used for this dropper are usually the same breaking strain or less then the tapered leader joining to the dry fly and fluorocarbon is often the preferred leader material used as it is less refractive and therefore less visible underwater, and is also denser than ordinary monofilament so that it and the nymph will sink to the desired depth quicker than with ordinary monofilament tippet material.
The third and final step is to tie the nymph on to the end of the dropper. The type of nymph will depend on the weight of the fly desired, and the type of imitation you're after. Pheasant tail nymphs, bead head nymphs, stick caddis nymphs and snail imitations are all good flies to use as nymphs in the tandem rig.
Where and when
The ideal locations for the tandem fly rig are just about anywhere where the fish may be feeding both on the surface and underneath it, and where a single dry fly is proving ineffective. Contrary to what you would expect, the trailing nymph does not readily hook up on stream bottom rocks, making it perfect for small bubbly streams such as the St Patrick's river, Meander and Mersey rivers. The technique is also quite effective on larger rivers such as the Macquarie where fish focusing on stick caddis nymphs or snails are sometimes all but impossible to catch with a lone dry fly. Fish taking nymphs and emergers close to the surface on the highland lakes are also good targets for this rig, either casting at the fish visually feeding, or fishing the windlanes, slicks or foam lines.
Anytime that the lone dry fly isn't working is a good time to try the tandem rig. For fish preoccupied with nymphs it can be a deadly method, but also worth noting is that even during a good hatch, the fish may still take preference for a lightly weighted nymph trailed behind the dry.
If things still aren't going your way try altering the weight of the nymph rather then changing to different types of flies. Quiet often a heavier fly can make all the difference, or a lighter, smaller, or bigger fly can do the trick. Brown, black or green coloured nymphs are generally better flies for Tasmanian rivers compared to the lighter coloured nymphs often preferred in New Zealand where this method of fishing is so popular.
Other two fly options
A nymph and a dry fly aren't the only possible options to use when using multiple flies on a river. Using two dry flies can be equally effective, one large buoyant attractor fly and a smaller imitative fly can be a useful way of hedging your bets, or alternatively two wet flies such as a couple of soft hackled "spiders" can be another option, cast across the current and swung in front of fish (the Partridge and Orange, Snipe and Purple or Hares Ear and Grouse are patterns to try).
A tandem fly rig can really improve catches when things are slow, and for the beginner in particular is an effective way to start finding fish regularly. Don't be daunted by the thought of two flies as they really are fairly easy to use. If the dry fly goes under strike immediately - you may be striking at snags for 20 or 30 goes, but the 31st strike may just be the fish you've been after.