Here's a formula for estimating the weight of a dogtooth tuna. It has been suggested by Julien Derozier in "Partir Pecher" nr. 36 (September 2013).
C = circumference (measured at the thickest point of the fish) in inches
L = length (measured only to the fork of the fin, i.e. the "shortest length") in inches
W = calculated weight in lbs
W = C x C x L : 800
The weight in kilos is W x 0,453.
Let's see who can confirm.