The leader you’ll use to target squid versus snapper or kingfish will be vastly different. One spooks easily but doesn’t put up much of a fight, the other will head straight for underwater structure to try and bust off and will put up a good fight once hooked.
For species that spook easily, like squid and trout; a lightweight fluorocarbon leader is ideal. It’s ultra clear and the thinner diameter of the lower breaking strains make it less visible in the water. The bonus is the higher level of abrasion resistance that fluorocarbon delivers, which makes it ideal for species like squid and trout who are generally found around underwater structure like rocks and weeds.
For smaller saltwater species like gurnard, mackerel, smaller trevally and kahawai/Australian salmon, that don’t put up much of a fight, a lightweight mono leader will work well. You could use anything from 12lb up to 30lb mono leader, and this will give you a good mix of suppleness and knot strength. Depending on the drift or tide strength, weight may or may not be required to get your bait down to your desired depth.
For your freshwater or estuarine species like rainbow and brown trout, salmon, perch and bream; lightweight fluorocarbon is ideal. 4lb – 12lb fluorocarbon tippet offers all the benefits of heavier weight fluorocarbon, but its thinner diameters and ultra clear line offer an increased level of stealth for these wary species.
If you’re targeting snapper, bigger kahawai/Australian salmon, mulloway or other mid-sized reef species, you’ll need to use a mid weight leader (30lb – 60lb). You can use either fluorocarbon or mono, but keep in mind that fluoro will give you a higher level of abrasion resistance. If you’re fishing with lures, and want a less visible and more abrasion resistance, then fluorocarbon will be the best option as its less visible than mono.
When you are targeting bigger or harder fighting species like XL snapper, kingfish, samson fish, groper/hapuku, or bass, a heavier weight leader with a thicker diameter is a must. These fish are strong, will fight long and hard, and will head straight for structure in an attempt to bust off. So, abrasion resistance is important, as is knot strength. Mono is a great option, for breaking strains from 80lb up to about 130lb. If you’re live baiting for these species, use fluorocarbon as it’s less visible to the fish.
When your game fishing, targeting marlin or tuna, you are generally going to be fishing with heavy weight leader – a minimum of 150 plus. If there’s even a slight possibility of catching a barrel sized tuna or a beast sized marlin, then 300-400lb mono leader is recommended. The difference here is that you may also need to increase the length of your leader. Because of the size of these species, you don’t want their bodies to come into contact with your mainline so your leader will need to be at least 3 meters, but many anglers use up to 9 meters when game fishing (if you are fishing for IGFA records, see comments below about combined leader length). Your leader offers a much higher level of abrasion resistance than your mainline, so it will handle chaffing against the fish’s body. It also gives your crew a stronger piece of material to grab hold of when you get your fish boat side.
If you’re chasing a potential IGFA record, make sure you’re up to speed on the rules and regulations around line and leader length. Find out more here.