Fish'o'meter - a unique ready
reckoner for estimating the weight of fish.
With many salmonid stocks diminishing in numbers, more and
more anglers are now returning fish rather than keeping them. However,
it is difficult to accurately weigh a fish which is still alive, so we
developed an equation to calculate this as accurately as possible. Only
two measurements are required, length (to the fork in the tail) and girth
(measured immediately in front of the dorsal fin). Both measurements can
be made quite easily using an ordinary measuring tape. Measure your fish
in centimeters and then add your measurements in the boxes below. The
formula is based on the measurements obtained from over 800 adult Atlantic
salmon sampled during the summer of 1994. For most fish, this should give
a weight which is within 5% of the actual weight. Although the formula
was calculated using salmon, I have been informed that it is reasonably
accurate for other salmonids such as trout. Formula was derived by Alastair
Gowans B.Sc. CEng. and Andy Gowans Ph.D.
For comparison, weights are also estimated using formulae derived from
NASCO and the Salmonid Council for Newfoundland and Labradors' data. We
have also extrapolated a length-only equation based on our own existing
data, so if you don't know the girth of your fish, fear not!
If you would like to more about the formula then e-mail