butterflyfish

[Ernie Reese]

Dear Colleagues,
We have read with interest the discussion that was initiated by
the May 19,
2001 posting by Dr. Gomelyuk related to our butterflyfish
indicator species
methodology (Crosby and Reese 1996; download-able from
http://coral.aoml.noaa.gov/themes/butterfl.pdf).  Apologies for
not being
able to provide input to this discussion in a more timely manner. 
Hopefully, this interesting and useful discussion can continue
and be
expanded (either on the coral listserver, or off-line between all
directly
interested parties).

Over the last few years, we have interacted with nearly 100
different
researchers, non-government environmental groups, and government
agency
representatives from around the world who have either used our
methods
(sometimes with interesting modifications) or were interested in
using the
method for various different end goals.  In partial response, we
have
conducted a number of training workshops throughout the Hawaiian
Islands,
Saipan, American Samoa and Guam, with more planned in the near
future in
other regions of the Indo-Pacific (i.e., in the Middle East later
this
month).  During last years ICRI Pacific Regional Symposium and
Workshops in
Noumea, an ad hoc group convened an informal meeting under the
auspices of
our host, Dr. Michel Kulbicki (ORSTOM), to discuss the potential
for a)
convening an international symposium and workshop on the use of
butterflyfish as indicators of change in coral reef ecosystems,
and b)
developing a coordinated database for those who are actively
utilizing some
form of our monitoring method.  There was unanimous support for
both steps
to occur, but no source of financial support has yet been
identified to mak=
e
either a reality.

It is clear that there is significant interest in the utilization
of
butterflyfish as indicators of change in the condition (some may
read this
as "health") of coral reef habitats.  The recent discussion on
this topic
that was initiated on the coral listserver reiterates this
interest (as wel=
l
as the continued value of the coral listserver for encouraging
discussion
and debate of various issues related to coral reefs =AD Jim
Hendee continues
to deserve major kudos).

We would now like to add our two-cents worth to the recent
discussion =AD

We have admittedly been somewhat lax in not publishing more
widely in the
peer-reviewed literature our analyses of approximately six years
worth of
data on butterflyfish from throughout the Pacific.  We hope to
rectify this
in the next few months with several manuscripts that we are now
completing
that we hope will provide more rigorous quantitative analyses of
a variety
of conditions in which the technique may be employed (including
as a measur=
e
of "recovery" of previously heavily impacted reefs near military
bombing
ranges).  Nevertheless, there is already quite a bit of
literature that has
been published related to various different aspects of
butterflyfish
behavior and their relationship with the coral reef community,
and even mor=
e
formal presentations on this topic have been made at numerous
scientific
forums (i.e., Proceedings of the Hawai'i Coral Reef Monitoring
Workshop,
June 9-11, 1998, Honolulu, Hawai'i; International conference on
Scientific
Aspects of coral Reef Assessment, Monitoring, and Restoration,
April 14-16,
1999, Ft. Lauderdale, FL; Ninth International Coral Reef
symposium, October
23-27, 2000, Bali)  by many others and ourselves.

Some useful points to remember when considering the butterflyfish
behavior
technique (which also includes more standard accepted coral and
fish
transect methodologies):
(1) many people who have tried to use this method have not
followed the key
guideline which is to pick one or two  obligate coral feeding
species, not
the entire assemblage of chaetodontids,
(2) percent coral cover should be measured in areas where the
candidate
indicator species has established their territories, since the
relation is
directly between the fish and its territorial coral habitat. The
inferences
of these relationships can then be extrapolated over the broader
reef
environment.
(3) feeding biology of the indicator species must be known.
(i.e., even
within the coral-feeding guild, a number of species specialize on
acroporid
corals).
(4) for the method to work best and to provide an "early warning"
of visibl=
e
change, the behavioral components must be measured. To date, few
studies
have done this,
(5) comparisons should be made within sites over time.  Care
should be take=
n
when attempting to make comparisons between sites that may differ
because o=
f
the stochastic processes of recruitment of coral and fish.

Some further thoughts for consideration:
=85 The general concept of "indicator species" is both powerful
and valid whe=
n
applied and interpreted correctly.
=85 "Criticisms" that have been sometimes been mentioned in the
past with
respect to our specific methodology are due to confusion between
the use of
obligate corallivore species=B9 behavioral changes over time, as
an indicator
of gradual sub-lethal and not readily visible change in coral
community
condition, versus the more general use of the broader approach of
counting
all species of Chaetodontidae as an indicator of coral cover.
[The recent
discussions on this topic on the coral listserver have been more
perceptive
than many in other venues for correctly noting this point].
=85 Despite the criticism by some in the literature that the more
general
method of correlating total chaetodontid numbers with percent
coral cover,
even this crude approach shows a significant correlation between
the two
variables.  Nevertheless, our contention is that obligate
corallivore
chaetodontid behavioral patterns and population size are more
directly
linked to the corals on which they are dependent as an energy
source,
especially when following one or at most two obligate corallivore
species
over time, than is the linkage between the entire butterflyfish
assemblage
and the coral community.
=85 Clearly, the selection of the candidate indicator species
must be based o=
n
knowledge of their behavioral ecology.  The life history
characteristics
that are important are : a) obligate coral feeder, b) territorial
and
therefore strongly site-attached, c) long-lived (most
butterflyfish seem to
be), and d) colorful or otherwise easily identifiable.
=85 As a general rule-of-thumb, the butterflyfish indicator
approach is most
appropriate when: a) gradual change (either deterioration or
recovery) of a
reef area is suspected, b) repeated measures over time at the
same site are
possible, and c) funds and "professional scientists" (i.e.,
Ph.D.=B9s and/or
expensive consultants) are not available.
=85 As a general rule-of-thumb, the butterflyfish indicator 
approach is
inappropriate when a) sudden, catastrophic change occurs or has
occurred
(i.e., due to storms, coral bleaching, or predation by crown-of-
thorns
starfish), b) repeated measures over time at the same site are
not possible=
,
and c) funds and professional scientists are available.
=85 If the question to be answered is "what is the percent coral
cover?" at a
particular point in time (i.e. a one-time snap-shot), it is
clearly more
useful and efficient to directly sub-sample the coral community
with
standard methods (i.e., line transect, quadrate).  A one time
"snap-shot" o=
f
chaetodon abundance and behavior is not appropriate to answer
such a
question.
=85 When gradual change in a coral reef community is suspected,
and an "early
warning" (i.e., before the reef is visibly dead) of such a change
is
desired, then the behavioral components (feeding rates, agonistic
rates, an=
d
territory size) of the indicator method are useful measurements
to collect
over time.
=85 The behavioral components of our method are unique in methods
for coral
ref assessment and monitoring.
=85 Of the behavioral components, agonistic behavior is the most
difficult to
interpret because it has multiple motivational causes.  Agonistic
behavior
includes both aggressive and submissive behaviors and may simply
be referre=
d
to as "fighting".  Animals fight for resources.  The three
fundamental
resources required of all animals are food, mates and a place to
live.  For
obligate corallivore butterflyfish, all of these resources are
directly
impacted by changes in the corals themselves.  If the food
quality or
quantity of a territorial organism declines, that organism will
tend to
expand its territory to increase its food supply and/or increase
its feedin=
g
rate.  When neighboring con-specifcs both follow this strategy,
agonistic
encounters will increase.  Thus, changes in agonistic rates of
behavior
and/or feeding rates and/or territory size serve as a potentially
powerful
"early warning" of changes in ecological conditions on the reef.

The bottom line is that the idea of using butterflyfish as
indicators of
coral reef ecosystem "health" is not going to die, nor should
it.   Aside
from its clear value as a legitimate tool in the diverse arsenal
of
professional scientific research methods for monitoring coral
reefs, and
perhaps more importantly as a tool for volunteer monitoring and
education/outreach programs, there are simply too many people who
find it
enjoyable and educational to swim around on the coral reefs
counting corals
and chaetodontids, and as an excuse to have fun, to have the
method fall
into disuse.  As rather thoroughly discussed  at the 1998 Hawaii
workshop,
there is no "perfect" method for monitoring coral reefs, and most
methods
have value by themselves and collectively. Our method is like a
step-wise
regression with each step adding information based on
implementers ability
to employ the additional step.  It can be modified to suit needs
and abilit=
y
of different situations and will provide reliable and useful
quantitative
date if conducted appropriately.  We see further "fine tuning" of
the metho=
d
and its gradual wide use in coral reef conservation,
sustainable-use
resource management and education/outreach efforts.


Dr. Ernst S. Reese      Dr. Michael P. Crosby
Professor                   The Senior Science Advisor for Marine
& Coastal
Ecosystems
Dept of Zoology         USAID & NOAA
University of Hawaii    Washington, DC
ereese at hawaii.edu       mcrosby at usaid.gov
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