There are several flies called a Mohawk but this is the one I've most commonly heard called the Mohawk in the UK. It's good for both fresh and saltwater, regularly used for Pike and has proved very successful for Bass (at least it has for me) 
It's a simple fly to tie, but the finished result is an effective and easy-casting fly, being narrow in cross-section but giving a good solid profile. My version is tied on a Mustad 4447 Heavy Nordic Bend Hook Size #4/0 using a fluorescent orange thread, and the finished length of the fly is about 130mm (5 inches).
Wind the thread all way along the hook from eye to the start of the bend. You can wind a few layers to build up a thicker body but make sure the thread finishes at the bend. Now tie in a small bunch of black bucktail, the "rule of thumb" for the size of bunches is about a 'toothpick' thickness. Immediately behind this tie in a second bunch of bucktail and continue tying in bunches all way along the shank of the hook. Try to keep the bunches on top of the hook.
Just before the eye of the hook tie in your final bunch of bucktail - but this time use red or orange colour bucktail. Finish off with a standard tapered head, whip finish, and seal the thread with head varnish. This is the classic Mohawk pattern and it works really well in poor light conditions and coloured water. It can be fished on a floating line, retrieving it just under the surface or on a slow sinking line to allow the fly to sink the be jerked upwards on retrieve. You can vary the colours and materials but the essence of the fly is the multiple bunches tied in along the hook shank to keep a solid profile.
