[Coral-List] Parrotfish loss drives reef decline

Eugene Shinn eugeneshinn at mail.usf.edu
Fri Feb 10 10:55:42 EST 2017

One might wonder if the indigenous people of Panama had fishhooks 
1000-500 years ago? And, were they able to affect parrotfish abundance 
enough to influence coral growth?Of all the many reef cores  drilled 
during the past few decades I can’t recall seeing Parrotfish 
teeth/beaks. It would take a good eye especially since cores recovered 
using these devices are biased toward larger corals. Most uncemented 
reef sand that could contain teeth and urchin spines is flushed out and 
lost during coring. Even if the article in Nature, “Parrotfish loss 
drives reef decline” is correctly interpreted one has to wonder if the 
conclusion is a “chicken-or-egg-which-came- first issue?” Cores from 
Florida reefs show they have suffered periods of non-growth during the 
Holocene and in fact cores and seismic profiling show long strips of the 
Florida reef tract where corals did not create a coral reef during the 
past 6,000 years. With all the sea fans, sea whips, sponges, and 
occasional large head corals that populate these non-reef areas it is 
easy for the average diver to think they are swimming over true coral 
reefs. In the early days of diving I certainly made that mistake. 
Whether periods of non-growth, and its causes in the past were the same 
as the non-growth we are seeing today is problematic. People in Florida, 
unlike citizens of Pacific islands, do not catch or legally eat 
Parrotfish. In Tahiti parrotfish are often the most expensive fish on 
the restaurant menu. Because we don’t eat them we still have an 
abundance of Parrotfish and Blue Tangs that munch the abundance of algae 
growing on our mostly dead corals. There is also no competition from 
algae eating /Diadema/, which disappeared from Florida reefs (in fact 
Caribbean wide) in 1983.

By watching and listening  keys divers can always see and hear the 
munching of Parrot fish taking bites from dead coral to get at the 
attached algae. I suspect there are more Parrots feeding on our dead 
reefs than on live reefs because they do not munch on live coral. On the 
Florida reef tract one simply cannot find dead corals that lack 
distinctive crisscrossing beak and tooth marks. Our dead reef areas are 
literally being chewed away and defecated as reef sand.Any coral polyps 
that might recruit to these dead coral surfaces will likely be swallowed 
by roving munching bands of Parrotfish and gangs of Blue Tangs. One 
might wonder that if these coral munchers were removed would the growing 
corals come back? Of course something else killed them in the first 
place and that something needs to be solved. It is highly doubtful if 
reef cores could be used to determine which came first, death of corals 
or Parrotfish removal. Gene


No Rocks, No Water, No Ecosystem (EAS)
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E. A. Shinn, Courtesy Professor
University of South Florida
College of Marine Science Room 221A
140 Seventh Avenue South
St. Petersburg, FL 33701
<eugeneshinn at mail.usf.edu>
Tel 727 553-1158
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