coral-list-digest V7 #61 Questions Based on Don Baker Question, Discussion on MPA Benefits, & John McManus Response

Jack Sobel jsobel at
Fri Mar 8 12:24:56 EST 2002

Can anyone provide any similarly conclusive, empirical evidence, using
similar standards, that any other fishery management tool, other than
reserves, has been directly responsible for improving long-term fishery
yields in a tropical reef system? How about sustaining those fisheries?
Sustaining the coral reef ecosystem?  Preventing collapse, extirpation, and
extinction of the more vulnerable fish populations?  Preventing reef
degradation?  Maintaining natural diversity and intact systems?  Could they
be doing this without being implemented or implemented very incrementally or
in very small areas?  I'm not questioning whether some of these other tools
do some of these things, just whether they can be demonstrated to do them
with the same standard and rigor of proof that is being asked by some for

I agree with much of the prior discussion on this topic, appreciate Don
Baker's frustration in selling the MPA/Marine Reserve concept to skeptics,
some of whom may have a strong short term political of financial stake in
resisting them.  There is certainly abundant published empirical evidence
and a strong theoretical basis for the positive effects of "no-take" within
reserves, including, but not limited to rebuilding fish populations and
restoring natural communities/systems. There is an equally strong
theoretical basis for the impact such rebuilding should have externally,
including both common-sense and more sophisticated (?) modelling and
numerical approaches, and increasing though more limited information on
positive impacts adjacent to or outside of reserves, including fishery
benefits. The issue of conclusively demonstrating that Marine Reserves will
improve fish catches overall to everyone's satisfaction is a difficult one
complicated by many factors, not the least of them being "control" issues
(both spatial & temporal), replicibility, natural environmental/recruitment
variability, interaction with the complicating effects of other management
measures, changes in fishing patterns or effort external to the reserves,
and a double standard or bias against reserves held by many.  Given this and
considering how few and how small existing reserves genarally are compared
to the size of fished areas, its amazing that science has made as much
progress as it has in demonstrating external changes and fishing benefits.
As the evidence for reserve benefits continues to mount, people's comfort
levels continue to grow, and especially as reserve size, number, and design
improves, the evidence for external fisheries benefits will also continue to
grow.  There is much more to reserve benefits than just fishery benefits and
they may not be the most important.

Jack A. Sobel, Director
Ecosystem Programs
The Ocean Conservancy
1725 DeSales St. NW, Suite #600
Washington, DC  20816
Phone:  (202) 429-5609 or (202) 857-3270
Fax:      (202) 872-0619
Email:  jsobel at
Web:    <>

-----Original Message-----
From: owner-coral-list-digest at
[mailto:owner-coral-list-digest at]
Sent: March 08, 2002 12:01 AM
To: coral-list-digest at
Subject: coral-list-digest V7 #61

  ----- Original Message -----=20
  From: pacaqts=20
  To: coral-list at
  Sent: Thursday, March 07, 2002 7:43 AM
  Subject: MPA Benefits - In Numbers

  Dear Coral - List Members,

  Though MPAs have a great many benefits with regards to observations , =
statements in a stack of MPA pubs, etc.  - where may I quickly find =
direct research and studies references that "do the numbers?"  The =
politicians and Gov. economic advisers simply say to us  'Yeah, well =
good & fine - talk is talk - but show us the figures - where you can =
prove to us that fisheries stocks are indeed enhanced by MPAs?" =20

  I need case examples with those numbers and not just words, =
observations, and perhaps institutional / academic 'whitewashing'.   An =
example of numbers would be a historical record of past catch landings =
vs those after the MPA establishment - with direct, verifiable =
correlation to the MPA of course. Anyone comment on Apo?

  Any assistance would be well appreciated here.

  Many thanks,
  Don Baker
  Lankayan-Billean-Tegaipil MPA
  Sabah, Malaysia


Date: Thu, 7 Mar 2002 21:19:41 -0500
From: "John McManus" <jmcmanus at>
Subject: MPAs -- Wrong null hypothesis?

I have long been puzzled by the resistance to MPAs found among some
scientists. It seems to me to be intuitively clear that if you fish heavily,
stocks will decline, and if you stop fishing, and have not irreversibly
altered the habitat, stocks should increase. I have certainly seen no
reasonable evidence that this is not the case. I suggest that we have been
using the wrong null hypothesis. We have been treating the reserve as if it
were a "treatment", when in fact, it is the lack of, or removal of, a
treatment (fishing pressure).

The null hypothesis should be that a reduction in fishing pressure should
lead over time to a return toward (if not to) natural abundances of fish.
The alternative hypothesis, and the one that should carry the burden of
proof, is that reducing fishing pressure does NOT result in a return toward
natural levels of abundance. Where the alternative turns out to be true, one
should investigate why it was true. Was it because the habitat had not yet
returned to reasonable normalcy? Is the result likely to be because the
study period was too short? Or, is it truly because reducing fishing
pressure does not generally result in increases in fish abundance.

The labeling is mostly important because most scientists are deeply
concerned about reducing Type I error (the chance that you say something is
true that is not), and pay little heed to Type II error (the chance that you
say something is not true when it is). The error should relate to the
alternate hypothesis, and the null hypothesis should be accepted in the
absence of sufficient evidence that the alternative is true. Thus, the null
hypothesis is that which arises most naturally from simple common sense, and
the alternative is the challenge to that logic. If we construct tests of
high power, lots of sample units, long time frames, etc., then we minimize
Type II error, and the designation of hypotheses is not as important.
However, the fact is that exceedingly few studies of MPAs have been
conducted in such a way as to minimize Type II error. And, because of our
arrangement of hypotheses, we have encouraged stakeholders and managers to
wait around while we challenge a null hypothesis that heavy fishing is
generally completely irreversible and thus reserves are useless.

I also propose that we keep separate the question of the increase of fish
catch balancing out the loss of fishing grounds. Obviously, this depends
greatly on how much fishing ground is being lost, how much the fish
populations had been reduced around the reserve, as well as factors such as
the mobility of fish in and out of the reserve. This is thus a question of
design -- how big, what shape, etc., and not one of "are MPAs effective or
not". I know of many tens of small reserves, on the order of 1/4th to 2 sq.
km, that have been put in by coastal communities in heavily fished areas,
and have not heard of any that resulted in people complaining that the
reserve did not increase in fish abundance. Rather, there are many cases of
fishers fishing preferentially around the edges of these reserves,
indicating that abundances are indeed higher in the reserves. So, "do the
reserves gain more fish compared to heavily fished areas nearby of similar
habitat type?" -- in all the cases I know of, published or unpublished, the
answer is yes. "Did the reserve's output make up for the loss in fishing
ground?" -- that would depend entirely on local circumstances. And,
evaluating "making up for" should generally include weighing nonfishery
benefits into the equation.

I suggest that we stop worrying about "are reserves effective?" until strong
evidence shows that most of them (with real fishing exclusions) are not.
Instead, we should focus on how big, what shape, where, etc.




John W. McManus, PhD
Director, National Center for Caribbean Coral Reef Research (NCORE)
Rosenstiel School of Marine and Atmospheric Sciences (RSMAS)
University of Miami, 4600 Rickenbacker Causeway
Miami, Florida 33149.
jmcmanus at
Tel. (305) 361-4814
Fax (305) 361-4910

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Date: Fri, 8 Mar 2002 14:49:11 +1000
From: "Mark Tupper" <mtupper at>
Subject: Fw: MPAs -- Wrong null hypothesis?

John McManus wrote:

> I suggest that we stop worrying about "are reserves effective?" until
> strong evidence shows that most of them (with real fishing exclusions) are
> Instead, we should focus on how big, what shape, where, etc.

I understand and agree with the thrust of John's message. I think there is
ample evidence to show that reserves CAN be effective, given sufficient
management and funding capacity and adequate design (e.g. reserves large
enough to encompass target species home range, etc.). I have no doubt that
significant reductions in fishing pressure will help fish populations to
rebound. However, asking whether reserves ARE effective is a different
question altogether. So far, broad scale assessments of MPAs have indicated
that most of them do not meet their management objectives. This is in many
cases not a question of biology or ecology but one of politics and
economics. It's fine to say that a reserve needs to be this big or that
shape to enhance fisheries, but getting all stakeholders to agree on MPA
specifics is often impossible, and hammering MPA plans past objecting
resource users will always lead to poor compliance.

 Before I ramble any further, I'll try to sum this up succinctly. Most MPAs
are basically "paper parks" that do not meet their resource management
goals. This fact has little to do with the ecological effects of protective
management on fish production, but is based mainly on institutional and
community capacity to properly manage MPAs. Thus, the proper question is not
"are MPAs effective", but "can MPAs be effectively managed for a given
community or fishery". I would submit that the answer to that question is
likely to be location and/or fishery-dependent.


 Mark Tupper

 Dr. Mark Tupper, Assistant Professor
University of Guam Marine Laboratory
UOG Station, Mangilao, Guam 96923, USA
Tel. 671-735-2185; Fax 671-734-6767

 Coordinator, Marine Protected Areas Research Group

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