[Coral-List] Artificial reefs

Lad lad at reef.org
Mon Mar 8 12:00:44 EST 2004

HI John and All,

I feel compelled by a strange Monday morning wind to weigh in on the AR
discussions.  Sorry if I'm taking up space in your in-box!  For those
interested in the continuing dialog, I feel that an important point is being
overlooked regarding management of artificial reef (AR) sites.

John, all of your points are very well taken and I agree with almost all of
what you presented.  Two issues that warrant further discussion are, first,
what is the purpose of an artificial reef and, second, if the purpose is
conservation, then we should consider applying some of the same conservation
techniques to artificial reefs that we use on natural reefs.

Relative to the first point, some artificial reefs are used for purposes
other than conservation (i.e. recreational diving, science, fishing).  If
the purpose is to provide increased catch per effort, then ARs may be the
way to go (considering the effect on overall stocks, of course).  If the
purpose is to provide a wreck diving recreational opportunity, then
placement of an AR may be a viable solution. If the purpose is to provide
structure for manipulative study, then ARs may serve that purpose. It is
important to remember that all ARs do not serve all purposes and that many
purposes may not warrant the use of ARs considering the related impacts.

Relative to the second point (conservation), it seems that much discussion
revolves around the effect of ARs in attraction vs. production.  I would
like to point out that attraction may not always be a bad thing.  The
concern is that fish are removed from an AR, not that fish are attracted.
The activities allowed on the AR should be the real issue, not simply the
effect of those activities.  It seems that in many recent discussions, it is
almost a given that ARs will include fishing activities and few are
addressing the potential of zoning ARs as no-take.

I would present that a no-take AR would attract fish, serve as habitat for
benthic organisms, provide non-extractive recreational opportunities and
opportunities for science without the negatives of increasing catch.  Of
course, your points of enforcement are well taken, though this is an issue
facing no-take natural reefs as well.  Stability of the structure is
dependent upon design, construction and placement.  And opportunities do
exist for funding of ARs that would not otherwise be available for
conservation programs (i.e. DOT funding for removal of concrete bridge
rubble, MARAD ship money).

I am not the greatest fan of artificial reefs, but I am also not ready to
write them off as a complete negative either.  I believe there are
possibilities for AR use, even in conservation, that satisfy specific
purposes, if the design, construction, and placement of the structure, as
well as the management of the site, follow the purpose.

Thanks for the forum!


Lad Akins
Executive Director
Reef Environmental Education Foundation (REEF)
98300 Overseas Hwy
Key Largo  FL 33037

-----Original Message-----
From: coral-list-bounces at coral.aoml.noaa.gov
 Behalf Of John McManus
Sent: Saturday, March 06, 2004 7:00 PM
To: 'Coral List'
Subject: [Coral-List] Artificial reefs

Hi all,

I believe that artificial reefs are potentially valuable tools for coral
reef conservation. However, most are probably not. Based on some
fascinating emails I have received, I think it important to explain my
reasoning. Unfortunately, the explanation is long, and so read on only
if you have a strong interest in all this.

Within the first several years or so, none of the newly-settled fish on
an artificial reef can possibly have a positive impact in terms of
alleviating fishing pressure. They will be too young. So, here are two
of the issues with respect to fishing.

1. How do you manage the reef in such a way that people do not use it to
increase fishing pressure on area stocks within the first five or so
years until the settled fish can reach the age of first reproduction?
Generally, the structure will have to be in an area in which fishing is
strictly and successfully prohibited for several years.

2. How do you demonstrate that after that time, the majority of fish
caught in the artificial reefs are those that settled there as
juveniles, especially given that there is usually incontrovertible
evidence (as in question 1) that the artificial reefs do indeed attract
fish from natural habitats? And, consequently, how many fish per unit
area of artificial reef do you then allow people to remove by fishing
(basically some very small fraction of the ones that settled there
several years before and managed to survive all those years despite the
high mortality imposed by the in-migrant fish)?

I've seen the impressive thousands of juveniles that often settle on
artificial reef. However, I'm also aware that only a few of those ever
survive to the age of first maturity. As Polovina pointed out very
elegantly more than a decade ago, an area is overfished only once its
natural stocks have been reduced by over 40 - 60% or more. Why then
would anyone think that there is a need to provide more habitat space in
order to get more fish? In most cases, if you want more fish, reduce
fishing. Do not make it cheaper for people to catch fish, as this
usually leads to fish stock depletion beyond the point where continued
overfishing leads to zero net profit.

Let's suppose you have an artificial reef of 10 by 10 meters, and that
after 5 years, there is one 5-year-old fish per sq. meter. (ignore the
1, 2, 3 and 4-year-olds, you'll need them in the following years). Let's
assume that that species has just exceeded its age of first reproduction
at five years, and is ready to start harvesting. There are now 10 x 10
or 100 fish to be harvested in that year. You cannot even keep one
fisher's family fed with the fish that grew up in that artificial reef.
The truth is, however, that the artificial reef will probably be
supplying far more than 100 fish per year. It will be getting them from
surrounding areas -- that is, unless the decline in fish stocks have
already made that source negligible.

Show me a situation where an artificial reef will not lead to
overfishing. Show me the fishing restrictions and the evidence that they
will be followed. Then show me that parts of it will not lift up during
large storms and destroy natural habitat. Show me that it won't pollute.
Show me that you have not diverted public funds from conservation
efforts, and that the expected returns justify the investment. Show me
that these and other harmful effects have been accounted for and I will
be public ally supportive.

I think artificial reefs, including those enhanced with electric
current, could increasingly be important ways of helping reefs to
recover from losses of corals (perhaps replacing them with
bleaching-resistant corals), and possibly fish. However, they should
meet the above criteria. Very few do.




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 rsmas.miami.edu
Tel. (305) 361-4814
Fax (305) 361-4910

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