I don’t know enough about these two particular species of grouper to answer your question on what specific differences there are between them, though. As for why they split, since one species is in the Pacific and one is in the Atlantic ocean, I’d say that geographic isolation is probably the main reason for their genetic divergence. They started out as one species, then found themselves split into two separated populations with no chance to interbreed among them. It’s interesting that their appearance is identical, although I wonder if there are any differences at all present, no matter how minor. This could mean that their environment and ecological niche is very similar and did not require any drastic evolutionary change. Now I myself am wondering just what exact genetic differences there are and what, if any, physical changes or adaptations may be present between these two species of grouper.

Actually I had wondered exactly what designated a ’species’ and I pondered asking that question, but was loath to do so on this site, as it might be considered off topic. So your response is quite helpful!

I think if I were involved in the species designation plan, I would be among the ’splitters’ more so than the ‘lumpers’. After all a difference is a difference, and science has not studied every difference to know what does or does not cause a change between the two. The difference in DNA could be only change in pigment between the two groupers; but then again that DNA difference could be a specific enzime the one grouper produces that the other does not.

So, in a nutshell, thank you for your response! But of course, now I wonder what specifically is different between the two sets of groupers, that caused them to be split.

Goliath grouper attacks
Wednesday, June 29, 2005 (13:03:07)

Posted by spearman

An estimated 100-pound Goliath grouper, commonly known as a jewfish, recently attacked a diver in the Keys, apparently mouthing the man’s head.

Bob Charles, of Cudjoe Key, came away from the June 7 encounter with a bruised and lacerated lip that required four stitches. “It was just so fast,” Charles told the Keynoter newspaper. “I just [saw] him turn, and then I just saw a bunch of bubbles and blood. “I didn’t realize my head was in his mouth until I was on the way to the hospital, and I saw the blood on the top of my head.” The largest member of the grouper family, a Goliath grouper can reach weights of more than 600 pounds. The fish was placed on the protected species list in 1990 after its numbers had dwindled. But in recent years, anecdotal reports around Florida suggest the species has made a strong comeback.

Goliath grouper are not generally considered aggressive, but there have been tales of a jewfish swallowing a man whole.

Charles would probably argue with the non-aggressive description attached to Goliath grouper.

He was diving with a friend in the Lower Keys, spearfishing for mangrove snapper in about 30 feet of water, when the attack occurred. Charles told the Keynoter that jewfish normally move when a diver is in their vicinity, but this one wouldn’t leave, remaining only 3 or 4 feet away.

“He was making this thudding noise they do, then, all of a sudden, he turned and hit me,” Charles told the Keynoter.

The attack tore off Charles’ facemask and regulator. Charles managed to swim back to his boat.

“I got off easy. He could’ve easily taken my lip off and peeled my face back,” Charles said. “If he was a 200- or 300-pounder, he could’ve easily killed me.”

in The Times-Union

Another source but more light hearted, it’s good ridance to those pesky divers who try to poach on these magnificient species:

Grouper kills fisherman
A fisherman who speared a protected species of grouper while diving off Florida has been killed after the fish swam into a hole and entangled him in the line attached to the speargun.

A 42-year-old Florida man, who has not been named, was free-diving in 7.6m/25′ of water off the lower Florida Keys this weekend when he speared a Goliath grouper, Epinephalus itajara.

According to a report from Reuters, Detective Mark Coleman said that police divers had found the speared fish tightly wedged in a hole with the man’s body entangled in the spear line: “It looks like the fish wrapped the line attached to the spear around the victim’s wrist. The fish then went into a hole in a coral rock, effectively pinning the man to the bottom of the ocean.”

The Goliath grouper is one of the world’s largest grouper species reaching a length of over 2m/6′6″ and weighing in at as much as 400kg/63 stones.

In the old days, it was fairly straightforward. A species was considered different if it could not produce viable offspring with another. This is no longer necessarily the case, as many recognized separate species can interbreed. So why the change in thinking? Some of it has to do with advances in the way of looking at morphology (the animals physical shape and skeletal structure), recognizing unique traits developed in response to the environment. One example is two groups of animals that become separated through geographic isolation and then develop slightly different adaptations in response to selective pressures of their new environment. At some point, the animals may still be similar enough to interbreed, yet obviously have diverged to some degree in terms of morphology and physical characteristics. So we consider whether these changes are enough to be able to classify an animal as a separate species even though they share a close genetic lineage. Speciation (one species branching off into others as a result of geographic isolation, for example) generally takes a long time to occur, so the trick is deciding at what point an animal can be considered a distinct species. Even if they are capable of interbreeding, morphological differences can be considered if they are found fully established within a self sustaining, separate population.

Another reason why the definition of species has undergone changes, and this applies especially in cases like this grouper, is the great advance in our understanding of genetics and DNA. Knowledge in this area has caused vast changes in how we look at species and taxonomy. Due to this understanding, even animals that are very morphologically similar and nearly identical looking are sometimes found to have markedly different DNA that is consistently contained within one population. In this case, an argument can be made that the two are different enough, at least genetically, to be considered separate. There are no doubt many other animals now that are still considered to be the same species, yet are genetically distinct in some way.

There are still problems with all of this. The definition of species has fuzzy boundaries, and there is a lot of disagreement among scientists. Life is diverse, evolving, always changing, branching out, it can be hard to accurately try and label everything as one thing or another. As far as how this relates to taxonomy, you also have your “lumpers” and your “splitters”. Lumpers tend to group similar animals into the same species, they think that minor differences are often not enough to break up one group of animals into different ones. I would imagine a lumper might disagree with separating these groupers into two species based on some DNA differences. “Splitters”, on the other hand, are the opposite. Splitters tend to look at things such as new DNA evidence, and split animals into ever more more species based on unique, sometimes very minor differences. These two camps can debate fiercely over what constitutes a new species, which muddies the waters even further. How many animals are currently the same species that actually are not? The answer to that question could lie a lot in your own viewpoint, are you a lumper or a splitter?

On top of this, you have the fact that, as I mentioned already, speciation is typically a gradual process with no really clear, magical point at which an animal suddenly becomes a new species. Then you have things like hybrids, sometimes whole populations of them, that can cause even further confusion over what can be considered a species.

Everything I have said here is of course very generalized and simplified. Bottom line is that the definition of species is complicated, and always evolving in response to our understanding of the natural world. I could go on and on about this stuff, but I wanted to just put a couple thoughts out there. Hopefully this is useful for you!

I can easily imagine some of the Goliath Groupers taking a snap at divers who enter their range of ocean, and just because of their tremendous size can engulf a human head with their mouths, knocking off regulators and masks. I assume this is the cause of any deaths attributed to these fish, since the ones I’ve met seemed notably non-aggressive, even a bit curious.

Cool story. Nice photo.

One positive note about the status of the Goliath is that, in US waters at least, it’s protected – with all harvesting of it prohibited. It’s rather interesting when again these discoveries arise and bring up the old debate of what really constitutes the classification of a species, since this finding was procured solely from DNA evidence. It really makes you wonder where we should supposedly draw the line at designating a species.