Something which fascinates me is when a very successful species is so successful that it evolves away from its original habitat into a new niche. Examples of this literally make up the history of life on the planet, but today I want to talk about one of my favorite families of fish, Balistidae, the triggerfish, the cunning, clever, and truculent nast5ers of the coral reef environment. Except today we are writing about a triggerfish which left the colorful, frenetic cities of the coral reef and evolved to live in the vast open ocean. This is Canthidermis maculata aka “the spotted oceanic triggerfish”, a medium-sized triggerfish which has a worldwide distribution in temperate oceans from New York to London, down around the Cape of Good Hope and then across the Indian Ocean to the Gulf of Thailand. It can be found in the Pacific Ocean from Japan across to Hawaii and to the California and South American coasts.

The fish are silver or gray with little pale dots of blue or white. Although they can grow to half a meter (20 inches) in length, adults are more commonly 35 centimeters (14 inches) long. Reef triggerfish are opportunistic feeders and so, it seems are spotted oceanic triggerfish which can be carnivorous or planktivorous depending on the circumstances (although they seem to specialize in hunting smaller fish).

Like many pelagic fish (but unlike most other triggerfish) these fish seem to assemble in loose schools to travel the oceans. they are preyed on by sailfish, mahi-mahi, large sea birds, and other such predators (and by rapacious humans, of course). Female triggerfish build their nests in rough proximity on ocean bottoms from 4 meters to 45 meters deep where they guard and aerate the eggs (which hatch very quickly and disseminate the little larval fish throughout the oceans.

A School of Ocean Triggerfish photographed by Klaus Stiefel