Most fish are defined by their features, much more so than by colour.
- Firstly, check which of the fins are present, or most prominent and what shape are they: rounded, triangular, tall, small? Do they have any particular markings: spots, lines, or margins (outline colour different to main colour).
- Secondly, check the caudal fin – fancy name for tail! What is the rear outline: forked, truncate (straight vertical), rounded, pointed, lanceolate (like a spear), or lunate (curved inwards like a sickle moon)? And what colour and does it have a margin.
- Thirdly, distinctive features like the barbels on a goatfish, the keels on the surgeonfish, the dorsal spine on the leatherjacket.
- Finally, where in the landscape was it, and what was it doing. For example, Butterflyfish: on the move, usually in pairs, sometimes in schools, nibbling algae; Hawkfish: sitting motionless on top of coral facing out; Coral trout: hiding under an overhang or a large hole.
These features combined should get you to the right family.
The markings and patterns and relative sizes of the different features should then get you to the species.
Remember – we only have the more common fish listed here. Use the references to explore further.