~65lb wahoo caught neat Cat Island

We were talking at Pete’s Pub last night about growth rates in wahoo,
so I tracked down a paper that describes this directly.

Fish can be aged using otoliths, the ear bones that are used for balance,
orientation and sound detection.  They are useful for aging fish because they
growth in distinct annual rings, much like the rings in a tree.  Since each ring
corresponds to a year of growth, fish can be easily aged using this technique.
Here is an otolith image from the paper my McBride et al in Marine and
Freshwater research (2008):

Image from a 2008 paper in Marine and Freshwater Resaerch by McBride et al.

This fish had 8 rings, identified by the small white dots, and thus in its
ninth year of life.  By aging a number of fish, a “length at age” curve can
be developed that is used to predict how old a fish is based on its length.
Here is the curve for Bahamas wahoo:

Length at age curve for Bahamas wahoo from the McBride et al. paper in Marine and Freshwater Research. Click for a larger view.

The y-axis here is in millimeters.  So this curve suggests that at 1 year old,
a wahoo would be predicted to be ~1 meter (40 inches) fork length.  That is
an extremely high growth rate – incredible a fish can grow that fast.
The curve also suggest that after ~3 years of age, growth rates slow substantially.

I will post some growth rates of other pelagic fish soon for comparative purposes.