Fish scales comparing ctenoid and cycloid

Fish scales are composed of connective tissue covered with calcium.  Typically, soft-rayed fish have smooth cycloid scales and spiny-rayed fish have ctenoid scales.

Scales can be used for aging fish.  The annulii, or growth rings like on trees, are counted from the focus (where growth starts) outward.  By measuring the distance between annulii, along a radius, the growth rate of the fish can even be estimated.



FWC Facts:
The Gulf sturgeon spawns 140 miles upstream from the mouth of the Suwannee River, one of the last pristine rivers with no dams to bar its path.

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