[Coral-List] Parrotfish loss drives reef decline
Mark.Tupper at utt.edu.tt
Mon Feb 13 07:38:33 EST 2017
The indigenous people of Panama (and elsewhere in the Caribbean) did indeed have fish hooks - mostly made from sea turtle carapace or from bone. They would not have used fish hooks to target herbivorous species like parrotfish, however. If they did eat parrotfish (probably unlikely given the abundance at that time of grouper, snapper and other predatory species that would readily take a hook), they would have captured it by trap or spear. As you allude, fishing parrotfish is historical in the Pacific but a relatively recent development in Caribbean fisheries and is primarily due to the loss of high-value predatory species such as groupers.
Psrrotfish loss causes coral reef decline through a reduction in herbivory, leading to algal overgrowth and reduced coral recruitment. As you stated, Caribbean species are herbivores that feed on algae by scraping it off the dead coral rock - by definition they feed on dead coral since algae does not grow on live coral polyps. That removal of algae from the deal coral substrate promotes recruitment of new coral spat to the bare surface. I doubt that much of the coral spat would be eaten because parrotfish (and surgeonfish) are generally roving foragers that feed in an area, strip it of algae and move on. They would likely not return to the same patch of substrate until sufficient time has passed for new algal growth to occur. To return to an area recently stripped of algae would not be optimal use of energy and would therefore decrease the fishes' fitness. If coral planulae settle on bare substrate first, I presume they can then preclude subsequent algal growth. A coral biologist can weigh in on that, it's outside of my fish realm and probably depends on factors such as nutrient input.
Mark H. Tupper, Ph.D.
Professor, Fisheries Sciences
Marine Science Unit
University of Trinidad and Tobago
2nd Avenue North, Western Main Road, Chaguaramas,
Republic of Trinidad and Tobago, West Indies.
Office Ph: +1 (868) 642 8888 Ext: 22126
Cell: +1 (868) 385-2545
E-mail: mark.tupper at utt.edu.tt; mtupper at coastal-resources.org
From: coral-list-bounces at coral.aoml.noaa.gov [mailto:coral-list-bounces at coral.aoml.noaa.gov] On Behalf Of Eugene Shinn
Sent: Friday, February 10, 2017 11:56 AM
To: coral-list at coral.aoml.noaa.gov
Subject: [Coral-List] Parrotfish loss drives reef decline
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)
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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