[Coral-List] Long term change in Eritrean reefs: past, present, future
goreau at bestweb.net
Fri Apr 18 10:08:16 EDT 2008
A paper by Gordon Sato in a book I am editing for the UN mentions
that the local fishermen are claiming increased catches after
mangrove establishment. Like you, I'd suspect the usual mangrove
dwellers. I think that Gordon has mainly word of mouth from local
fishermen, but he has close contacts with the Eritrean fisheries
department, and can let you know who might be following up on this.
I'm sure you know Ivan Nagelkerken's recent great recent paper that
resolves the controversy on whether mangrove juvenile fish habitat is
due to strucutural protection by the mangrove roots per se, or the
fact that they are in shallow water habitat, or because the shoreline
is remote from large reef predators (notwithstanding the barracudas
that love to lurk near mangrove roots)? By making artificial mangrove
roots and placing them in many different habitats he found the
highest juvenile fish recruitment on outer reef slopes, proving that
it is the shelter itself that is the key factor.
We similarly notice extraordinary juvenile fish recruitment to
electrical reef restoration projects, and we are joining forces with
the Ecocean group to release juveniles and larvae into such habitat
to short circuit juvenile mortality and rapidly restore reef
fisheries (that is to say, if anyone will fund this kind of work,
which is far from clear). It is now obvious that MPAs don't work
unless they protect prime quality habitat, and where that is gone
only habitat restoration will restore fisheries. Now all we need is a
few decades more for policymakers and funders to realize that the MPA
fad can't work unless habitat restoration is the prime focus of
coastal fisheries management. Until then they will continue to throw
good money after bad and pray for "resilience" and that global
warming and pollution will disappear by themselves.............
On Apr 18, 2008, at 8:22 AM, Tupper, Mark (WorldFish) wrote:
> Dear Tom and listers,
> I have been following this thread with some interest after doing a
> review of GEF-funded coral reef-related projects, which included
> work in Eritrea. I was wondering the same thing as Tom - if the
> reefs are so great, why are the fisheries not so great?
> Taking a snippet from Tom's post:
> "I am one of the scientific advisors to the Manzanar Project, which
> has planted vast mangrove forests along Eritrean desert shorelines
> where no mangroves ever existed, using Gordon Sato's innovative
> approaches, and these have resulted in large increases in catches
> by local fishermen, which would presumably imply that the reef
> fisheries habitat is not as pristine as claimed."
> I was wondering if anyone knew what species these large catch
> increases involved. If they were Gerreids or Lutjanids, some
> species of which have mangrove-dependent life history stages, or
> other fishes that might be wholly dependent on mangrove habitats,
> then the increases would result simply from the increase in
> available mangrove habitat. In that case, the amount of reef
> (pristine or otherwise) would have no bearing on the catch.
> However, if the increased catches contained a high proportion of
> reef fish which maybe using mangrove prop roots as an alternative
> form of structure/shelter, that might imply (as Tom said) that
> there was insufficient suitable reef habitat.
> Tom, do you have any data on those increased catches, or would you
> know someone who does?
> Mark Tupper
> -----Original Message-----
> From: coral-list-bounces at coral.aoml.noaa.gov on behalf of Thomas
> Sent: Fri 4/18/2008 1:35 AM
> To: coral-list at coral.aoml.noaa.gov
> Cc: Gordon Sato
> Subject: [Coral-List] Long term change in Eritrean reefs: past,
>> Long term change in Eritrean reefs: past, present, future
> I'm wondering why this very interesting article on Eritrea's reefs
> just posted on the list server ends with the word "Advertisement"?
> Could that be because every place in the world is advertising their
> reefs as "pristine" to attract tourists, whether that is true or not?
> In the early 1960s the late Thomas F. Goreau did a lot of work on
> Eritrean reefs, especially in the Dahlak Arhipelago. To his surprise
> he found the coral cover was very low. That was where he discovered
> the feeding mode of Acanthaster planci, extruding its stomach to
> digest coral tissue, something he had not seen when he collected the
> first live Acanthaster intact at Bikini Atoll in 1947, when they
> lived deep in crevices and only came out to feed at night (they were
> previously known from dredge haul samples and nothing was known of
> their ecology). He attributed the low coral cover he found in Eritrea
> to chronic infestation by Acanthaster swarms. This was long before
> the "first" outbreaks that he, Rick Chesher, and Rick Randall studied
> in the Western Pacific in the late 1960s. I have all the photos and
> scientific specimens, but I have never found anyone interested in
> comparing them to look at long term change.
> Now if the report below is correct, and I completely trust Charlie
> Veron''s assessment, this implies that the severe Acanthaster
> predation that was there 4-5 decades ago has disappeared completely
> and permanently? If so, that is truly remarkable, and deserves much
> further work because all across the Indo-Pacific we have been seeing
> recurrent infestations and nobody has any idea how to control them.
> It should also be noted that mapping the Bleaching HotSpots (sensu
> Goreau & Hayes, 1994) shows that there should have been several very
> severe bleaching events there in recent decades. I have several times
> alerted researchers in Eritrea to look out for them, but never
> received any field confirmation. The long term sea surface
> temperature trends for Eritrea (which I can supply on request)
> suggest that worse lies ahead since maximum temperatures in this
> region is warming considerably faster than the global ocean average
> (Goreau et al, 2005).
> Another interesting point about this article below is that if the
> reefs are so good everywhere in Eritrea, why have the fisheries
> declined? I am one of the scientific advisors to the Manzanar
> Project, which has planted vast mangrove forests along Eritrean
> desert shorelines where no mangroves ever existed, using Gordon
> Sato's innovative approaches, and these have resulted in large
> increases in catches by local fishermen, which would presumably imply
> that the reef fisheries habitat is not as pristine as claimed.
> It is delightful to hear that Eritrean reefs are "pristine", but this
> raises very important issues of long term historical changes, and
> almost certainly does not imply immunity to the challenges that
> global warming will throw at them. More work is clearly needed.
>> Thomas J. Goreau, PhD
> Global Coral Reef Alliance
> 37 Pleasant Street, Cambridge MA 02139
> goreau at bestweb.net
Thomas J. Goreau, PhD
Global Coral Reef Alliance
37 Pleasant Street, Cambridge MA 02139
goreau at bestweb.net
More information about the Coral-List