Ancient fish mosaics help modern scientists
STANFORD (US) — Ancient mosaic art is helping researchers
look far back into the history of the dusky grouper to determine
how effective efforts to reverse the decline of the fish species
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Photo credit: E. Trainito
Ideally, reserve biologists would compare modern fish to groupers
hundreds or thousands of years ago, before the advent of large-scale
commercial fishing, but because humans have had an impact on grouper
populations in the Mediterranean for so long, that’s not possible.
“When we consider a species recovered, they may still in
fact be altered relative to their original baseline,” explains
Fiorenza Micheli, professor of marine ecology at Stanford University.
Grouper populations in no-take reserves show signs of returning
to ancient numbers and sizes and also seem to be moving into more
Micheli and Paolo Guidetti of the University of Salento in Italy
are using ancient mosaic art to look farther back into the grouper’s
history than traditional ecological methods allow. Their paper appears
in Frontiers in Ecology and the Environment.
Fishing scenes were not uncommon sources of inspiration for coastal
Mediterranean artists. Micheli and Guidetti found hundreds of Etruscan,
Greek, and Roman artworks involving sea creatures. Fish depicted
in mosaics were often detailed enough to be recognizable as dusky
groupers, but unlike today’s animals, the ones depicted were
enormous—in one case, large enough to eat a fisherman whole.
Though possibly a case of artistic license, the depictions imply
that groupers were large enough to be considered “sea monsters.”
By comparison, groupers in unprotected waters today range from 50-60
centimeters (20-24 inches) in length.
Even more surprising, mosaics show men fishing for groupers with
harpoons at the water’s surface, unheard of today. Modern
sport fishermen spearfish groupers in deep water. Writings from
the time corroborate the Roman view of the grouper as a shallow-water
fish. Pliny and Ovid both describe angling for groupers from shore.
“It’s particularly interesting that there are children
fishing from the boats,” says Micheli in reference to the
Louvre’s Triumph of Neptune and Amphitrite, which depicts
cupids harpooning a grouper. “One interpretation would be
that it’s so easy to fish them that kids could do it.”
Modern grouper populations in no-take reserves show signs of returning
to historical numbers and sizes. Reserve biologists report that
populations that haven’t faced being harvested for years begin
to move into shallower waters. Groupers in protected areas achieve
population abundances five to 10 times greater than those in the
rest of the Mediterranean, and can reach sizes of 90-100 centimeters.
Unfortunately, these advances mainly highlight the failed recovery
of dusky groupers at large. Because the average size of many grouper
populations is smaller than the size of sexual maturity, current
conditions appear unsustainable.
“One extreme suggestion would be to place a moratorium on
grouper fishing, because they’re not recovering outside of
a few small marine reserves,” Micheli says. “But this
would be an unpopular measure.” Sport fishing is a major tourism
draw in the Mediterranean, and one of the primary targets is grouper.
Ignoring historical, qualitative sources of ecological data creates
the risk of producing a drastically distorted view of baseline conditions,
Micheli says. “At the moment, we’re missing a major
player in Mediterranean shallow-water ecosystems.”
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