Fish Classification

Fact: Seahorses are the only fish that swim upright.

IMG_4827In 2010 it was estimated that there are more than 21,000 fish species worldwide, with more than 4000 of these being on coral reefs. It is an impossible task for anyone to remember all of these species, especially now as Marine Scientists venture deeper than ever before, discovering new species of fish on every dive they make.

Luckily there is, as recreational divers, no need to learn every species of fish by heart, whether your preferred diving location is equatorial or subpolar waters many of the fish you come across will be from the same or similar families. If you repeatedly dive in similar destinations, you will quickly start to pick up the names of frequently seen fish.

Classification or categorising is a simple yet effective way of placing the many fish species into groups. These groups are used in practically all fish identification books. Fish classification is an easy way for you to look up an unknown fish after your dive. In the PADI Adventures in Diving, AWARE Fish Identification course you learn a list of the 12 groupings which are ‘commonly used’ to identify fish in tropical or temperate water, the groups are as follows;

  1. Butterflyfish, Angelfish and Surgeonfish
  2. Jacks, Barracuda, Porgy and Chubs
  3. Snappers and Grunts
  4. Damselfish, Chromis and Hamlets
  5. Groupers, Seabass and Basslets
  6. Parrotfish and Wrasse
  7. Squirrelfish, Bigeyes and Cardinalfish
  8. Blennies, Gobies and Jawfish
  9. Flounders, Scorpionfish, Lizards and Frogfish
  10. Filefish, Triggerfish, Puffers, Trunkfish, Cowfish, Goatfish, Trumpetfish and Drums
  11. Eels
  12. Sharks and Rays

IMG_0967[1]However this may depend on the fish book you or your dive centre may own. Not all books are assembled into the 12 groups above. Many fish books identify and classify the fish in an index in the front of the book. These indexes usually have named sections which briefly describe classification method, there are also sketches of various fish which belong to that section, these are labelled and a page reference is given. By identifying certain factors of your unknown fish (whilst on your dive) it is easy to find them in the various fish ID books you or your dive centre may be in possession of. A few key factors to bear in mind are

  1. Shape.
  2. Where about on the reef it swims, this maybe just above the reef or near the surface or under rocks.
  3. Method of swimming, be this with pectoral fins or caudal fin.

Yet each book varies and classification methods do depend from book to book, not every book is like how is described above, a good idea is to become familiar with your fish ID book before your dive, that way you know what characteristics to look out for whilst on your dive, should you spot a new and unknown fish.

4 responses to “Fish Classification

  1. Reading your fact about the Seahorses, there are an incredible minority and therefore I can safely deduct that this is the reason why as a diver you should never been seen to dive in the position of a Seahorse 🙂

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