Two Species of Goliath

When it comes to the heavyweights of tropical reefs of the world, few fish will command more attention than the Goliath grouper (Epinephelus itajara). But did you know there are two species of Goliath?

Atlantic goliath grouper (Epinephelus itajara)

No, they’re not named after the biblical giant slain by David, but for their robust size. Fully grown, a West Atlantic goliath grouper (Epinephelus itajara) can exceed 500 lbs. / 220 kgs in weight, and measure up to 7 ft. / 2.1 m in length, easily making them the largest tropical reef dwelling boney fish in the world. Once this robust size fish could be found on the reefs Tropical Atlantic and Caribbean from Florida to Brazil. Due to overfishing throughout much of this region, Florida has become the only remaining holdfast where this species is still found in any numbers.

But, did you know they also reside in the waters of the Eastern Pacific, from the Sea of Cortez to Columbia?

For years it was widely believed that both Atlantic (E. itajara) and Eastern Pacific goliath groupers were the same species. Now it looks like the text books many need a rewrite, as researchers from the University of Hawaii, the Wildlife Conservation Society, Smithsonian Tropical Research Institute, National Marine Fisheries Service and Projecto Meros do Brazil have collectively confirmed back in summer of 2008 that the Panamic (East Pacific) goliath is in fact a separate species – Epinephelus quinquefasciatus.

“For more than a century, ichthyologists have argued that the Pacific and Atlantic goliath grouper were the same species, because the two populations are identical in body form and markings,” said Dr. Matthew Craig of the Hawaii Institute of Marine Biology. “It wasn’t until the use of genetic testing techniques on fish DNA became widespread that the argument was settled.”

Turns out that both species did share the same ancestry, going back roughly three-and-a-half million years ago, when the Caribbean was open to the Pacific. But when the isthmus that is now present-day Panama formed, the population on the Pacific side was completely cut off.

Eastern Pacific goliath grouper (Epinephelus quinquefasciatus)

Before DNA testing became the fashionable answer for everything, ichthyologists had to rely on a fish’s anatomical physiology (appearance) for classification. Not an easy task, considering that there are over 60 named groupers belonging to the species Epinephelus, in the Tropical Western Pacific alone. Fortunately, only a small number of these groupers are capable of reaching anywhere close to the massive proportions of the Atlantic goliath (Epinephelus itajara).

Tropical Western Pacific giant grouper (Epinephelus lanceolatus). Photo taken in 1992.

The largest, and for the most part equal in size, is the giant grouper – Epinephelus lanceolatus found in the tropical Western Pacific. Although considered to be the “sister species” of goliath groupers found in the western hemisphere, their body markings and coloration are different. Instead of mottled tan and grey, their primary dark grey coloration is punctuated by small, whitish spots and blotches, and many times yellow accenting their fins.

Next in line, based on both physical resemblance and the ability to reach comparable size, is the malabar grouper (E. malabaricus). And to a lesser extent, it is followed by the brown-marbled grouper (E. fuscogutattus), and then the orange-spotted grouper (E. coioides). Again, the physical build is close to identical, but the brown to tan and grey mottled coloration patterns are significantly different.

However, this last part was of little help considering there is no outward difference in physical appearance between West Atlantic and Pacific goliaths when placed side by side. 

Here we have what could be called the variety pack. Five Atlantic goliath grouper (Epinephelus itajara) displaying at least three different coloration and marking patterns.

It wasn’t until researchers began testing, using DNA markers that the hypothesis was clarified—Pacific and West Atlantic goliath groupers were not the same. This warranted the Pacific group name change, from E. itajara classification to a new species designation E. quinquefasciatus, of for us layman, the Eastern Pacific goliath.

In all my years of diving Florida, the Caribbean and the Eastern Pacific from Panama and Costa up to Mexico’s Sea of Cortez, I have seen two these Eastern Pacific variants. Both where in Costa Rica between the late 1980’s and early 1990’s. Considering these giant groupers are coastal species, as they are not encountered in the waters of off shore islands like Cocos Island or the Galapagos, and the fact the status of the rest of their kin is considered for the most part critically endangered, the Eastern Pacific could very well become extinct due to over fishing a few years from now.

 

Information for this article was provided by: Matthew T. Craig, M.A., Ph.D., Papahānoumokuākea Marine National Monument Postdoctoral Fellow, Hawaii Institute of Marine Biology, Kaneohe, Hawaii.