405_April_24

MARINE BIOLOGY WITH MIKE SCOTLAND - FISH IDENTIFICATION

The Hawaiin Triggerfish at Sanggeang Island Komodo under the double volcano

triggerfish was used as in latin ‘Ballista’ means crossbow and ‘oides’ means ‘similar to’. Their scientific name is ‘Ballistoides’. The third little spine might just be a spare. They are a diverse family of fish and are related to Leatherjackets (File Fish) and Porcupine fish. They belong to the Order of fish named Tetraodontoformes which means four teeth. It can be a little hard to see the relationship between the Leatherjackets and the Trigger fish until you have a close look at their anatomy. They provide a good introduction to fish biology for those who like to learn about fish. The

reasoning behind fish classification can also be seen by looking more closely at the two families. We have discussed the dorsal spine arrangement which both have. Both use it as a defensive mechanism to lock themselves into a crevice so that predators cannot get them out. They both have a large second dorsal fin at the tail end which is made of soft fin rays. Both have a similarly large anal fin also made entirely of soft fin rays. The two large soft fins at the rear are quite symmetrical and can make up about one third to half of the body length. Undulating

Pinktail Triggerfish, Melichthys vidua , has white dorsal and anal fins with a black margin, a pinkish caudal fin with a white base, and yellowish snout and pectoral fin.

79

www.divelog.net.au

DIVE LOG Australasia #405 - April ‘24