These days, the dusky grouper is a major predator in the Mediterranean Sea, generally growing to about two feet long. But that wasn't always the case...and ancient mosaics provide a rare chance to see what this beast used to be.


Researchers at Italy's University of Salento examined both artistic and literary references to the dusky grouper throughout history. This isn't just an academic issue - the dusky grouper has been the victim of overfishing in recent decades, leaving the species perilously endangered. To have the best chance at preserving the species, we need to know what their ideal conditions are, and then try to replicate them as best as possible.

If Roman art is any indication, we've never seen a real dusky grouper, at least not one in its real preferred habitat. Twenty-three mosaics depicting the fish dating from the 1st to the 5th century CE were studied, and two major trends emerged. First, dusky groupers used to be huge, seemingly big enough to eat a person, as you can more clearly see in this image (below).

Modern groupers are known to reach about 3.5 feet long, and close to 5 feet is just possible under absolutely perfect circumstances, but this suggests they were once even bigger. Even adjusting for artistic licence, we're likely looking at a species that once enjoyed far more abundant food resources and, as a result, grew to generally greater lengths - enough to enter "sea monster" territory, at least as far as Roman mosaic-makers were concerned.


Secondly, the mosaics consistently depict people hunting the groupers with poles and harpoons. That fishing method wouldn't work out in the deep Mediterranean waters where the dusky grouper is now found. Instead, it strongly suggests that the grouper once lived in shallow waters, and in the intervening centuries has been forced out to the deep water. That fits with references made by the Roman authors Ovid and Pliny the Elder, both of who mention anglers fishing for groupers in shallow waters.

A new picture is potentially starting to emerge, thanks to these mosaics. Before the advent of more extreme commercial fishing practices, the groupers lived in the shallows, which provided them with far greater access to food. Consequently, they grew bigger and stronger than they do today. That's backed up by modern reserves, which have been built in shallow waters for the groupers and have since seen the fish grow up to 40 inches long, as opposed to 24 inches in more "natural" sites. It's all a remarkable example of how ancient art can become modern science.

Via Discovery News. Image by Giorces.