Chapter One: Reef Fishes I

From Microcosm Aquarium Explorer

The History & Anatomy of Reef Fishes

A Primer on Some of Nature’s Most Successful and Fantastic Works

“Why such an explosion of fishes, so brilliantly adorned in pattern, so famously varied in contour? No one knows.”

—Carlos Safina, Song for a Blue Ocean, 1997

By Scott W. Michael

"In the foothills of the Alps in northern Italy, there is a fossilized coral reef where scientists have found the remains of more than 80 families of saltwater fishes, including members of the Acanthuridae, Chaetodontidae, Labridae, Pomacentridae, and Zanclidae—all strikingly similar to the modern-day forms of marine angelfishes, butterflyfishes, wrasses, damselfishes, and even the Moorish Idol. The victims of a mass die-off, perhaps caused by an algal bloom, these exceptional fossils represent the first-known record of a complete community of coral reef fishes. Known as Monte Bolca, the reef and its fossil fishes is an estimated 50 million years old.

Reef fishes are ancient life forms, with many of them traced back to the Eocene Epoch, which followed shortly after the extinctions of the dinosaurs of the late Cretaceous Period. It was a time of great change in marine environments, with the appearance, diversification, and spread of the reef-building stony corals (which had come close to obliteration at the time of the mass extinction of the dinosaurs), and the creation of new, shallow-water habitats. Over a 20-million-year period, most of the modern reef fish families appear in the fossil record, and from that time until today, a period of over 50 million years, they have remained relatively unchanged.

The precursors to the reef fishes are much older and among the first vertebrates known on Earth. The first fishes in the fossil record date back roughly 500 million years. Fossil evidence of the first-known hominids, by way of comparison, dates back a mere 5 million years. Of the 48,170 recognized living vertebrates found on Earth, more than half—or about 24,600—of these are fishes. Birds and mammals together account for less than 14,000 species.

Clearly, living in water can have long-term advantages. The fishes are an evolutionary success story, with anatomies and survival modes that have carried them through some of the worst geological and meteorological conditions and disasters Earth has known. Long before the appearance of mammals and birds in the fossil record, the fishes survived the tremendous mass extinction of 225 million years ago that killed 95% of all marine invertebrate species. Then, whatever wiped out the dinosaurs 65 million years ago was dodged by a great array of fishes—enough to give us greater species diversity today than at any time in Earth’s history. Almost 60% of the world’s known fish species live only in saltwater. Not surprisingly, the coral reefs of the world are home to an amazing variety of bony fishes. Almost every niche on the reef, as well as nearby ecosystems (mangrove areas, seagrass beds, etc.), is occupied by one or more fish species.

In general terms, reef fishes are smaller, more colorful, and more diverse than the oceanic fishes. They are also relatively long-lived and more sedentary, often spending their entire lives on the same reef, with the exception of a larval period in which many species spend days or weeks drifting in the plankton before settling out."

Excerpt from Reef Fishes Volume 1