questions reef fish and invertebrates (fwd)
Coral Health and Monitoring Program
coral at coral.AOML.ERL.GOV
Fri Nov 24 18:19:52 EST 1995
Forwarded to coral-list:
---------- Forwarded message ----------
Date: Wed, 06 Dec 1995 14:29:00 -0800 (PST)
From: John McManus <J.MCMANUS at cgnet.com>
To: owner-coral-list <owner-coral-list at reef.aoml.erl.gov>
Subject: RE: questions reef fish and invertebrates
TO : Herman Cesar
FROM : John McManus
DATE : December 6, 1995
The area figure of 100,000 km2 for coral reefs in Indonesia is probably a
good estimate, and one which we and others have arrived at by various,
very crude means. It means that Indonesia covers about 17% of the world's
reefs (plus or minus 5%).
The invertebrate production of reefs vary tremendously depending on
conditions and what people gather. A few studies indicate that the
production might equal that of fish production in areas where many species
are gathered. Thus, a working figure of 15mt/km2/yr (plus or minus 5)
might be appropriate for Indonesia, but only for shallow areas near land
which are accessible. Thus, what is actually harvested for invertebrates
is less than the harvest potential, unlike fin-fisheries which are mostly
overharvested in Southeast Asia. Note also that octupos on reef slopes
are often major fisheries, particularly when fish have been overharvested.
The big problem with invertebrate fisheries is the ease with which a
target group can be depleted. Giant clam, sea urchin and sea cucumber
fisheries have collapsed in many areas. Usually the collapses occur after
large-volume dealers arrive in a village. We are a long way from being
able to determine individually the sustainable yield of most invertebrate
species on reefs, and much further from developing effective ways to
manage such fisheries sustainably.
Subject: questions reef fish and invertebrates
Date: Wednesday, November 29, 1995 10:45PM
All coral list subscribers,
Thanks very much for the many reactions. I have some more questions:
First, I am trying to contact Mark Erdmann who has done some very
interesting work on coral reef ecology. Does anyone know his e-mail or
Secondly, I am looking at some issues related to the poison fish trade. My
questions are (please allow my ignorance as an economist):
If fishermen go to a prestine untouched and unfished area, what would be the
average biomass of groupers (especially Epinephelus spp., Plectropomus spp.
and Cephalopholis spp.) and of Napoleon wrasses (Cheilinus Undulatus) per
square kilometer of reef?
What would be the average sustainable yield of these groupers and N.wrasses?
When do they obtain sexual maturity? (At which bodyweight is that? Are
groupers of 800 grams sexually mature?
Thirdly, I am trying to guess the total area of coral reefs in Indonesia
(e.g. at 20 phantom (37 m; 110 ft.). For the Philippines are have data
ranging from 25 to 33 thousand km2. I have an estimate for the whole of East
Asia of around 180,000 km2. Would 100,000 km2 for Indonesia be a good guess?
Fourthy, does anyone know something of sustainable yield of invertebrates? I
would like to know sustainable yield per km2 of sea-cucumbers, trochus,
giant clams, lobsters, etc.
By the way, if people are interested in receiving a copy of the report on
the economics of coral reef destruction in Indonesia when it is ready and
has become official (early next year hopefully; working paper), please let
Thanks in advance,
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