questions reef fish and invertebrates (fwd)

[Coral Health and Monitoring Program]

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 

Dear Herman, 

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.  

Sincerely, 

John McManus 
 ---------- 
From: owner-coral-list 
To: coral-list 
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  
other address? 

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  
me know. 

Thanks in advance, 

Herman Cesar