Line Weight Vs Fish Size

[fishpro]

Here's something I've been thinking about for a while and I'm struggling to figure it out. How do rod weights (in terms of AFTMA grain weights) relate to fish size in terms of two rods from the same series but of different weights? For example, a 12wt weight "requires" 380 grains to load, and it is common and acceptable to fish for and land 100lb tarpon on such a rod, yet a two weight at 80 grains (approximately 20% of the 12wt) would never be used for a 20lb tarpon, nor would it be considered ethical. Is there any relation or function between grain weights and target fish size? Logically it sounds like it would be a linear relation, but fly fishing knowledge suggests otherwise.

[DonAndersen]

Fish pro,

 

Fly size/weight determines fly line weight required to cast it. Big flies = big fish = heavy lines.

Note the word cast not lobed as some of the techniques of today require.

 

Don

[bcubed]

Don, i'll play ball. Lots of tarpon flies are a hell of a lot smaller and less heavy then what guys are throwing for trout (clousers, etc). Easy to throw a tarpon toad on a 5 weight, but I don't want to be connected to the thing on the other end that eats it with a 5 weight!

[Conor]

Fish pro, it's a good question. Id say it has to do with practicality and specifics of the target species. I think what your poking at is whether it is ethical to fight large game on fly tackle, which is a fair question.

 

 

To keep the same ratio of rod power to fish size, we would be looking at a 50 weight or so for tarpon and other large quarry. But you can fight a tarpon for and hour and release it safely. Not so with trout. And it is easy to bring an 8 weight for baby tarpon, not so easy to find a 50 weight for the big boys. That's the practicality aspect which takes linear out of the equation.

[fishpro]

That's a good point about the species. It also lead me to think that perhaps larger fish (even of the same species) tend to have more stamina, therefore it's okay to play them longer as they will still survive.

[DonAndersen]

Bcube,

 

As you rightly point out, a lot of "trout flies" would be better handled by spin gear. Casting a Clouser w/o using a line capable is called lobbing.

And I had no idea that Tarpon ate tiny flies, I just assumed as a predator, it ate 'big".

 

Don

 

[lad]

Tarpon can be caught on the same flies that catch big bulls. Anything that represents a minnow and the big difference between Tarpon and bullies are the Tarpon have no teeth! Really need to strip set very hard to get a good set. Fantastic fish to catch and the air show they put on is incredible. Great fish for fly fishing but the larger ones are much harder to keep on the line due to them fighting in the air. Quite beautiful fish with these huge scales. Coolest fly fishing T-shirts have them on! haha Here are a couple pics from the south.

[BTCA]

If I may chip in.

Fly lines have nothing to do with the fish size. Fly lines are only to carry flies which in this case they are about the same size flies. But the rod is used to cast it and to fight the fish.

The grain weight of the lines is what loading the rods. A 12wt tarpon rod blank is thick and stiff and will require more grain to make it bend and loaded.

A 2wt rod blank is thin that only need light grain weight to load it.

You can still use that 2wt fly line with 12wt tarpon rod and probably landing a 100lb tarpon with it, but you can't use a 2wt rod with 12wt line to land a tarpon.

So big fish = big rod.

[DonAndersen]

If I may chip in.

Fly lines have nothing to do with the fish size. Fly lines are only to carry flies which in this case they are about the same size flies. But the rod is used to cast it and to fight the fish.

The grain weight of the lines is what loading the rods. A 12wt tarpon rod blank is thick and stiff and will require more grain to make it bend and loaded.

A 2wt rod blank is thin that only need light grain weight to load it.

You can still use that 2wt fly line with 12wt tarpon rod and probably landing a 100lb tarpon with it, but you can't use a 2wt rod with 12wt line to land a tarpon.

So big fish = big rod.

 

The line weight must be high enough to transmit the energy to the fly. Small flies can be cast with any line weight however large flies require kind weights containing enough energy to move the fly.

Ya don't shoot elephants with a pop gun.

 

Don