Formula for fish weight

[jasonfish320]

Hey gang,

I had a very interesting conversation with a client of ours today who also happens to be an Orvis sponsored fly fisherman and has possibly caught the world's largest brook trout (12lb 3oz) on Osprey Lake in Northern Territories. It's a long story, but basically it was believed that the largest brooky was caught in the 1800's, however someone caught a 14lb'r in the same river 3 years ago and challenged the record but after a DNA sample the fish came back to be a native splake, not a brook trout, which brings up the argument of whether or not the one caught back in the 1800's was in fact a brook trout. It was interesting story, anyways back on topic...

He showed me a formula I had never seen before to figure out weight of a fish and be accurate within an 1/8oz. I have not tried it yet, as I just learned about it this morning, but here it is:

(L)X(G)squared/800=weight

Length x Girth(squared) divided by/ 800=approx. weight.

[nofearengineer]

That formula is usually given with the length squared instead of the girth, but it should be fairly accurate, but to say within 1/8 oz. is ludicrous. That formula might be accurate to within 5% on most typical fusiform fish in a 1-10lb range, but outside of that, you're definitely going to have to specify a different scaling factor (your 800) for each species, and maybe for each sub-population, i.e. Florida strain vs. Northern strain Largemouth, or for very large fish.