[Coral-List] Parrotfish and coral
Mark.Tupper at utt.edu.tt
Fri Feb 17 17:36:46 EST 2017
Just for clarification, I wasn't suggesting that hook and line were the only gears used by pre-Colombian people. Traps were certainly certainly used, as were weirs, intertidal fish corrals, nets made of plant fibres such as liana vines, and spears. Many of these ancient forms of fishing are still being used in developing countries and/or rural areas, for example Hawaiian intertidal fish ponds (check out Jason Philibotte's interesting work on those), or coastal mangrove weirs and fish corrals using natural materials - still common in the Philippines and in Brazil. A very interesting read on Brazilian ancient fishing methods still in use can be found at http://antiquity.ac.uk/projgall/colonese344. The corrals and fish ponds right outside my house on Nonoc Island (Philippines) were built to target coralgroupers and rabbitfish, but of course they catch everything under the sun and Filipino reef fishers do not entertain such wasteful concepts as "discards".
The point may seem like semantics but it is important whether a reef fish is caught or whether it is specifically targeted. Many Caribbean herbivorous fish now and in pre-Columbian times were likely bycatch in fisheries targeting larger species that had higher fillet yields (flesh to bone/organ ratio).
One of the arguments brought up in discussing ancient fisheries (eg in the Wing and Wing paper) is whether the shift to pelagic fisheries was a result of fishing down reef fish, some environmental change, or the development of improved net technology. It seems like most people agree with the fishing out the reefs explanation. Im not certain of anything but I'm a little skeptical that overfishing reefs is the only answer, although I've no doubt that's part of the picture. Fishers are a pragmatic bunch and will usually chase the best ratio of cost, value and yield. If you compare pelagics like mahimahi, yellowfin tuna, or swordfish that have fillet yields of 65-80% to snappers and groupers that have fillet yields of 30-35%, you can see the incentive to develop gear capable of catching fast-swimming pelagics. As for small surgeonfish like blue tang, I've never seen a fillet yield published but I would be surprised if it was more than 20-25%. They're quite thin and bony. Large parrotfish such as rainbows and midnights probably have good fillet yields and would therefore be potential targets, depending on how pre-Colombians found their palatability. Fishers I knew in the Turks & Caicos didn't target them because apparently they "tasted like mud".
Fillet yield would also explain why Pacific Islanders do target Acanthurids as preferred species. There are a number of large surgeonfish and unicornfish species in the Pacific that yield enough flesh to be a valuable catch. But I can certainly say that here in the SE Caribbean, nobody gets up in the morning and says "oh boy, I can't wait to catch a blue tang". Nonetheless some are inevitably landed in trap fisheries.
I agree with Les and Tim and Dennis that there are all sorts of underlying complexities that we are not getting at. For example, traditional fisheries "wisdom" (dogma?) tells us that fishing preferentially for piscivores should lead to a release of predation on their prey. For all the preferential pressure on grouper, snapper, grunt etc., and apparent fishing down food webs, was there ever an increase in their herbivorous prey (such as parrotfish and surgeonfish)? I don't know and nor does anyone I've asked. If there wasn't, why not? Sufficient non-target (bycatch) mortality on herbivores? Are we wrong about the effects of releasing predation on herbivores? Or are there simply enough other non-targeted predators (squirrelfishes? morays?) to keep herbivorous fish populations in check?
There is absolutely nothing simple about coral reef ecology or reef fisheries.
On Feb 17, 2017, at 5:24 PM, Eugene Shinn <eugeneshinn at mail.usf.edu<mailto:eugeneshinn at mail.usf.edu>> wrote:
Thanks to all who have weighed in and posted comments on the subject of
parrotfish herbivory, ancient fishing, and coral growth. I learned a
lot. The paper by Cramer, K. L., (2013) /History of human occupation and
environmental change in western and central Caribbean Panama,/ /Bulletin
of Marine Science /89m (4) 955-982 Is an outstanding read. The paper is
well documented, and shows how heavily populated central America was in
pre Columbian times before the Spanish came and obliterated more than 90
percent of the population. And yes, they did eat fish but most of the
damage to coral reefs then as now was mainly related to agriculture and
runoff. To feed fish to the once large population using only fish hooks
made from turtle shell still seems a bit of a stretch, especially
herbivorous fish. How does one bait a hook with algae? Most likely the
ancients used spears and nets along with fish traps. Traps are easy to
construct from native materials and such traps are still made and used
today in various parts of the Caribbean. Traps will certainly capture
parrotfish while even modern metal fishhooks seldom catch these fish.
Other postings point out that parrotfish remove algae on dead
coral or other surfaces thus preparing the surface for coral
recruitment. This has long been the accepted standard explanation and
surely applies in many areas.
Hanna Rempel (off line) pointed out that indeed certain parrotfish
do bite live coral. I agree and have watched them doing so. I once spent
a day on Looe Key reef watching parrotfish taking bites from large
Montastraea heads. It was an especially calm day and there were small
piles of parrotfish poop resting on the tops of several live coral
heads. Unfortunately I was not there long enough to watch for an effect
the defecated sand might have on the coral. Of course waves eventually
swept the sandy material off or the coral polyps removed the sand. What
was obvious, however, were many 3 to 5 cm dead spots supporting algae
and/or infected with black band disease. Bite marks suggested that
parrotfish made these areas. I had never seen parrotfish bites in
infected with algae before. Possibly there was an overabundance of
parrotfish because the reef is protected.
Now back to my earlier comments concerning Carysfort reef in the
Florida Keys. I have been taking serial photos there for the past 56
years. Three summers ago I spent a day there with Phil Dustan who had
done the most significant monitoring work there in the 1970s when it was
a beautiful live /Acropora/ reef. At Carysfort all the /A. palmata/ and
virtually all the backreef /A. cervicornis/ was dead and had been
converted to rubble. Parrotfish were have a field day. They were biting
coral that had died back in the mid 1980s. There had been virtually no
recruitment there in the 30 or more years since. At the rapid rate the
parrotfish and roving bands of blue tangs are munching the dead coral an
abundance of reef sand has been created. That reef sand no doubt
contains fish teeth. Now spring ahead a hundred years and assume the
coral are flourishing and take some cores of the reef. Where would the
parrotfish teeth be? Would they not be in the sediment associated with
the period of time when the reef was dead and plenty of algae to eat? If
you counted the abundance of the teeth in the sandy part of the cores
would you conclude the parrotfish had killed the reef? Or would you
assume the fish died thus causing the corals to die? Or was it
pollution/disease/or climate change or something else, possibly African
dust that killed the reef?
That parrotfish herbivory is not needed to stimulate coral reef
growth has been shown by others, Auchley A. McField MD. Alverez-Filip L.
(2016) /Rapidly increasing macroalgal cover not related to herbivorous
fishes on Mesoamerican reefs/. PeerJ 4:e2084
<https://doi.org/10.7717/peerj.2084>their observations on the Belize
reef tract are well documented.
Kauffman has suggested hurricanes might kill and cause rubble to
become algal infested. That could also lead to parrotfish increases.
That event was well documented in Jamaica.
When hurricane Donna decimated Grecian Rocks reef in 1960 the
reef did not become algal infested. In fact most broken fragments of
branching corals began growing and the reef area expanded. We documented
the storms effect. (Ball, et al 1967), and the recovery (Shinn 1976).
The same happened in 1965 when Betsy decimated the same reef. Again the
reef recovered. However, the reef did not recover after 1990 when
hurricane Andrew swept though the upper keys. Something had changed and
algal infestation became rampant. There were no longer /Diadema/ to
remove the algae (they had died in 1983) but there were sill abundant
parrotfish. Some time ago I proposed that the 1983 increase in algal
turf was related to the Caribbean-side demise of /Diadema/ and the
effects of African dust. (Lessios, et al 1984) had shown that /Diadema/
demise was Caribbean-wide. Monitoring of African dust by Joe Prospero
showed the dust had blanketed the Caribbean in 1983; He had been
monitoring dust in the eastern Caribbean since 1965 and showed 1983 to
be the peak year of dust flux to the Caribbean. (Shinn, E. A. Smith, G.
W., Prospero, J. M, Betzer, P., Hayes, M I, Garrison, V. Barber. R T.,
2000, /African dust and the demise of Caribbean coral reefs/: Geological
Research Letters, v. 27, P. 3129-3132). Many will say it was sewage and
increasing population in the Keys that cause demise. However that does
not explain why the same events were happening simultaneously to reefs
around small islands throughout the Caribbean. Dust flux remains high
and a recent unfunded and unpublished preliminary testing of African
dust collected from the air showed it to be lethal to A/. cervicornis/.
Why it is toxic is not known but our earlier work at USGS showed that in
addition to the nutrients iron, and phosphate, the dust coincidentally
contains (copper, mercury, arsenic, radiogenic beryllium 7, lead 210,
various pesticides, and approximately 200 viable species of bacteria and
fungi) Possibly some of these ingredients can affect coral growth. But
that's another story. Hopefully some day someone will do the work needed
to determine exactly what is in the dust that affects coral and people)
but do not expect any government agency to fund the research. Everyone
who has written a proposal to do so has been turned down. Is more study
needed? You bet! 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<mailto:eugeneshinn at mail.usf.edu>> Tel 727 553-1158
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<mailto:eugeneshinn at mail.usf.edu>>
Tel 727 553-1158
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