How the Goliath Grouper Evolved into two Species

The Goliath Grouper or jewfish lives in the tropical and sub-tropical waters of the Pacific and Atlantic Oceans. The largest of the groupers, the goliath grouper can grow to over two meters in length and exceed 800 pounds in weight.

For over a hundred years, ichthyologists (scientists who study fish) believed that the goliath groupers found in both the Atlantic and Pacific Oceans belonged to the same species. Fish from the two geographically separated communities appeared identical.

In 2008, a group of scientists from the Wildlife Conservation Society, the Smithsonian Tropical Research Institute, the National Marine Fisheries Service and Projecto Meros do Brazil under the leadership of Doctor. Matthew Craig of the Hawaii Institute of Marine Biology published their study of the genetic code of the two populations of groupers. These scientists found significant differences between the DNA of the Atlantic goliath grouper and the Pacific goliath grouper. Based on their findings, the Pacific goliath grouper now has the new species name Epinephelus quinquefasciatus. The Atlantic goliath grouper remains under the old name of Epinephelus itajara.

Geographical separation of populations is one of the methods in which new species of animals evolve. Until three and a half million years ago, the continents of North and South America were separate and fish could swim freely between the Atlantic and Pacific oceans. Then the small strip of land we know as Panama joined the two continents together.  This isolated the tropical waters of the Pacific from those of the Atlantic and Caribbean.

The goliath grouper, a tropical or sub-tropical fish, is unable to tolerate the cold waters, which joins the two oceans in the arctic or around Cape Horn. Therefore, two geographically separate populations of fish were created.

When DNA replicates, small errors in transcription occur. Where these errors do not cause fatal mutations, they are passed on to future generations. With each succeeding generation, the genetic code of the population drifts further away from that of the original population. These errors are random events so two separate populations will accumulate different errors. Eventually the DNA of the two populations is significantly different that they can be ascribed to two different species as has happened with the goliath grouper.

Overfishing has placed both species of goliath grouper under significant environmental pressures. The scarcity of the Atlantic goliath grouper led to its placement on the World Conservation Union’s Red List of Endangered Species of Fauna and Flora. It is probable the Pacific goliath grouper will join this list in the not to distant future. It took millions of years for the two species to evolve, let us hope that a few hundred years of man’s predation will not cause them to become extinct.

Reference sources:

Florida State University Koenig and Coleman Laboratory

The Marine Genomics Project

NOAA South East Fisheries Research Center