Fly selection should be made depending on what there feeding on. As they say you will need to "match the hatch" as these fish are known to be finicky. In most cases a glass minnow pattern works best with a full intermediate sinking fly line and minimum 20 lb. tippet. 25 lb. is better.
They are pelagic fish that are constantly on the move looking for food and never stop swimming. So you can image the calorie intake they might need. They are mostly late spring and summer time visitors to our near shore waters here in NE Florida but have also been occasionally caught in the other months. You can find them in a feeding frenzy attacking large bait pods by looking for diving birds over erupting water. They generally run 8-12lbs. (recorded 36.5 lbs). My largest ever caught came in at 16 lbs. This fish deserves to be on a fly rodders bucket-list! Be sure to check out the video located on my websites home page.
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St. Augustine Fly Fishing 10 Lb. Little Tunny
(caught on a Temple Fork Outfitters BVK Rod/Natilus NV 10/11 Fly Reel)