The tried and tested method of Blue Shark fishing is laying a chum slick and fishing bait in the middle of the slick. To lay a chum slick starts with grinding up Mackerel, herring, sardines, squid, or any small baitfish until it looks like a porridge. You can grind this into a 5 gallon pail, put on the lid and throw it into the freezer. Once frozen drill a few holes in the bottom and hang it off your boat with just the bottom in the water. As it thaws it will leave a nice slick behind you. Watch that the Blue shark does not grab onto or try to take a piece out of the bucket.
Double the last 20 feet or so of your line with a Bimini twist, then attach a 200-pound test ball-bearing snap swivel with an Offshore Swivel Knot. The leader for Blue Sharks can be single-strand stainless from 100 to 300 pound test, with a haywire twist in the upper end and a 6/0 to 10/0 hook. Bait the hook with whole or chunk pogy, mackerel, herring, whiting, or any small bottom fish.
A 3/0 to 4/0 size reel matched to a six-foot stand-up style rod loaded with 30- to 50- pound test mono will do fine, although some veterans prefer an 80-pound outfit in case one of those bigger critters is hooked. Either way, a good rod belt with a gimbal pin, plus a shoulder or kidney harness is a must.
Send your baited hook out into the middle of the slick about 50 to 75 yards behind the boat. Now it's a waiting game, if the Blue Shark is around it will follow the slick until it reaches your bait.