HCRI Project INTERIM Report Format
I.
Project Title: KAHEKILI ECOSYSTEM RECOVERY AREA -Science Planning and Support
Principle Investigator: Ivor Williams
Project Staff:
Organization: Hawaii Cooperative Fishery Research Unit
Grant Number: NA07NOS4000193
Date: May 23rd 2008
II.
Executive Summary
Hawaii Division of Aquatic Resource (HDAR) is currently working to establish an ‘Ecosystem
Recovery Area’ (ERA) encompassing reef areas adjacent to Kahekili Beach park in West Maui.
The goal of the proposed ERA is to increase the reef’s capacity to resist a phase shift from coral
to macroalgal domination by prohibiting the take of herbivorous fish and sea-urchins.
The aims of this project were to provide survey design, analytical, and other scientific support to
staff of Hawaii DAR to: (1) assist with the design and implementation of a statistically- and
scientifically-valid baseline of pre-ERA establishment conditions on the Kahekili reef; and (2)
utilize new and existing data generated by HDAR and partners, from survey programs in Maui
and elsewhere, to draw broader conclusions about the relationships between local herbivore
stocks and benthic algal communities (particularly in terms of reefs’ vulnerability to macroalgal
overgrowth).
Project staff, together with staff of HDAR and UH Botany (several of whom were working on a
parallel HCRI-RP project based at the proposed Kahekili ERA) together designed and
implemented baselines survey approach. Fish and benthos were therefore surveyed at 89 sites
within the ERA.
Survey sites were grouped into six broad habitat categories, and herbivore biomass in a range of
functional groups was calculated per habitat category.
Data derived from NOAA-DAR cruises of remote and inaccessible locations around the Main
Hawaii Islands (MHI) showed clear negative associations between reef herbivore biomass and
local human population density, consistent with greater fishing impacts at more populous
location.
Among shallow water survey data available to DAR, there was wide variability in local
herbivore biomass, and very clear negative relationships between herbivore biomass and
macroalgal cover.
III.
Purpose
A. Detailed description of the resource management problem(s) to be addressed.
Hawaii Division of Aquatic Resource (HDAR) is presently exploring the possibility of
establishing an ‘ecosystem recovery area’ (ERA) in front of Kahekili Beach Park in West Maui.
The reef in the proposed ERA, while still in relatively good condition, has been intermittently
overgrown by the invasive alga Acanthophora spicifera in recent years. A. spicifera is highly
palatable alga, and the specific goal of the ERA is to restrict take of herbivorous fishes and seaurchins to thereby restore the reef’s capacity to prevent invasive algal blooms from occurring–
and, by doing that, ultimately to halt the insipient slide from coral- to algal-domination. Draft
regulations have been written and HDAR will soon begin the formal process of establishing the
ERA at Kahekili. This project provides analytical and survey design support to HDAR and
partner’s efforts to establish the ERA and generate meaningful data against which eventual
effectiveness of the ERA can be assessed.
While the main spatial focus is on the proposed Kahekili ERA, the problem of coral to algal
phase shifts is a concern for many Hawaii reef areas, particularly around heavily populated parts
of the state, and so this project will also support wider scale collaborative projects in the state
relating to herbivory and macroalgal domination of local reefs.
B. Detailed description of the question(s) asked to answer the resource management
problem(s)
The core longer-term question is whether restricting the take of herbivores in the Kahekili ERA
leads to (i) rises in herbivore stocks; and (ii) whether any increases in herbivore stocks lead to
greater capacity of the reef to resist macroalgal blooms. The timescale of protected area
implementation and of (expected) ecological recovery are very much longer than the duration of
this project, but a key objective of this project is to establish a scientifically meaningful and
robust pre-closure herbivore and benthic community baselines.
In terms of the broader topic of what is driving coral to algal phase shifts on Hawaiian reefs, key
questions include: (1) whether there is any evidence that herbivore stocks are depleted around the
populated parts of the state which have become overgrown by macroalgae in recent years; (2)
whether there is evidence that locations with large herbivore stocks are less prone to macroalgal
overgrowth; and (3) if there are inverse relationships between herbivore stocks and macroalgal
abundance, which group(s) of herbivores are particularly important in terms of providing
resilience to algal overgrowth?
C. Overarching goal(s) of the project
(1) Provide basis for judging effectiveness of herbivore protection as means of reversing
coral to algal phase shifts at Kahekili and on Hawaiian reefs more widely.
(2) Provide scientifically valid information on relationships between herbivore stocks and
algal communities on Hawaiian reefs more generally (particularly around Maui Island),
sufficient to justify wider protection of key grazing organisms (e.g. through stricter bag
or size limits).
D. Hypothesis (if application) and objectives to answer each question.
(1) Objective: Design, and implement baseline surveys of fish and benthic populations in the
proposed Kahekili ERA. No suitable hypothesis for this project.
(2) Objectives: Collate and analyze data on herbivore stocks and benthic cover from surveys
in Maui and elsewhere in the Main Hawaiian Islands (MHI). Collate and analyze
information on the status of herbivore stocks around the MHI, and determine the extent to
which herbivores are or are not depleted close to human population centers.
IV.
Approach
Detailed description of the work performed for each objective from III(C), including (but
not limited to):
A. list individuals and organizations actually performing the work
B. material list
C. construction instructions for anything used to accomplish the III(C) objectives
D. deployment steps
E. data collection procedures
F. data analysis techniques
G. photos from research during each stage (construction, in situ, lab)
H. contact information for companies used to purchase items unique to your project
(if applicable)
(Objective 1)
Baseline surveys of the proposed Kahekili ERA were conducted in January 2008 by
project staff (Ivor Williams), staff of HDAR (Russell Sparks, John Mitchell, Kristy
Wong), staff of University of Hawaii Department of Botany (UH: Mark Vermeij,
Meghan Dailer, Darla White) working on a parallel project (also funded through HCRIRP).
Figure 1. Location of Kahekili Baseline Surveys
Surveys were haphazardly located on hardbottom areas within the proposed Kahekili
ERA boundaries with the aim of broadly covering the full extent of the area and with
adequate replication within different habitat zones (Figure 1). Surveys were conducted
from a small boat. Survey teams comprising two divers each were haphazardly dropped
over hardbottom areas throughout the proposed ERA. The divers would then swim
straight down to the nearest suitable habitat (hardbottom large enough to lay a survey
transect in); one of the survey divers tied of the starting point of the survey transect and
the other recorded the transect start location using a GPS in a waterproof bag attached to
a float. As much as possible, surveys were always run parallel to the shoreline running
approximately northwards, and in all cases a transect bearing was taken by one divers. In
total 89 surveys were conducted throughout the proposed ERA.
Survey transects were of 25m length. One of the divers conducted fish surveys using
methods closely based on those used by NOAA-CRED throughout the state of Hawaii (so
data would be comparable with larger-scale data sets): species, number and size (in 5cm
slots) was recorded for all fishes larger 15 cm total length (TL) within a 4-m wide belt
centered on the diver as they laid out the 25 m transect tape. The diver would then turn
around and resurvey the transect line, recording species, number and size of all fishes
smaller than 15 cm TL in a 2m wide belt centered on the transect line.
The other survey diver followed the fish survey diver, and conducted a photo quadrat
survey of the benthos under the transect line, and then recorded all sea-urchins with a 1mwide belt, during a return swim down the transect line.
Fish surveys were conducted by project staff and by staff of HDAR, but benthic surveys
were largely performed by UH staff working on a parallel project with its own reporting
requirements. This project report will therefore only cover details of fish survey methods
and data processing.
(Objective 2)
Two sources of data have been utilized to broadly assess status of herbivores on
Hawaiian reefs, and on links between herbivore stocks and benthic algal communities:
(1) Main Hawaiian Islands Reef Assessment Program (MHI-RAMP), which involved
staff of NOAA Coral Reef Ecosystem Division in Hawaii (NOAA-CRED) and Hawaii
DAR. For that program, 128 surveys were conducted around mostly previously unsurveyed parts of the MHI between Feb 2005 and Aug 2006; and
(2) Hawaii DAR’s ongoing survey programs, including: (i) laynet-ban assessment
program, which monitors target fish and visually estimated benthic composition at 6
locations around Maui Island; (ii) DAR’s ongoing coral-reef monitoring program around
Maui and Lanai; and (iii) Hawaii DAR’s shallow target fish surveys of the Big Island.
NOAA-CRED survey methods are detailed on the NOAA PIFSC web page
(http://www.nmfs.hawaii.edu/cred/eco_assess.php), but essentially involve three 25mtransects per site. Transects were surveyed by fish and benthic teams – fishes >20cm TL
being surveyed on 4m-wide transects by each of 2 divers per transect (divers swimming
in parallel) and fishes < 20cm TL in 2-m wide belts during return swims on the same
transects.
All Hawaii DAR survey data used here comes from 5 minute timed swims in shallow
water areas (<3m deep). Surveys involved pairs of divers recording fishes (size, species,
number) of target fishes and key herbivores within 5m-wide belts centered on the diver.
In each case, survey start and end points were recorded using GPS’s so that survey
lengths can be determined.
V.
Results
A. Findings for each III(C) objective.
B. Answers to III(B) each resource management question(s).
C. Site specific results for each location (Can place in an appendix as electronic file).
(Objective 1)
Figure 2. Location of Kahekili Baseline Surveys
Herbivore biomass estimates per site are shown in Figure 2. ‘Key surgeonfish’ were those
that are known to feed largely on benthic algae: Acanthurus achilles; A. triostegus; A.
guttatus; A. leucopareius; A. nigrofuscus; Zebrasoma flavescens; Naso lituratus. ’Other
surgeonfish’ are those that are detritivores or planktivores as adults: Ctenochaetus spp.;
Naso breviorostris; Naso hexacanthus, and medium-large surgeonfish which
predominantly feed on diatoms over compacted sand: Acanthurus blochii; A. dussumieri;
A. olivaceous; and A. nigroris.
Sites were also grouped into broad habitat categories within the Kahekili ERA (Table 1).
Table 1. Herbivorous Fish Biomass by habitat type within the Kahekili ERA.
(Mean ±SD)
Habitat
Deep Aggregate Reef
Shallow Aggregate Reef
Shallow Spur and Groove
Mid-Deep Spur and Groove
Shallow Pavement
Mixed Mid-Depth
-2
N
Depth (ft)
Parrotfish (g m )
Key Surgeon (g m-2)
Other Surg (g m-2)
13
29
9
15
12
11
28.0 ± 6.5
3.5 ± 5.6
3.8 ± 3.9
9.0 ± 11.9
13.8 ± 4.0
3.3 ± 6.5
11.3 ± 23.6
15.1 ± 20.3
11.2 ± 1.7
10.6 ± 12.6
21.3 ± 24.4
18.0 ± 43.4
28.1 ± 8.2
4.2 ± 5.9
2.2 ± 4.1
28.0 ± 6.5
7.5 ± 3.3
2.0 ± 3.4
20.0 ± 24.3
9.4 ± 8.6
17.0 ± 5.0
0.5 ± 1.6
2.7 ± 5.1
1.6 ± 3.5
Habitat groupings were still being determined at the time of writing this report, but were
intended to represent clear natural habitat groupings within the ERA. There were clear
differences in fish stocks among locations: for example, shallow spur and groove sites
had much higher herbivore biomass than deeper spur and groove zones. Future
comparisons of fish biomass should be made within comparable habitat zones. To
facilitate that, this project will generate maps of the Kahekili ERA with clearly
demarcated habitat classifications.
(Objective 2)
Big (C. perspic, S. rubro)
Med (C. spilurus, C. carolinus)
Small (S. psittacus, S. dubius, C. zonarchus)
MacroAlgae
Shallow Water Surveys
Fishes > 15cm TL
12
40
20
20
4
Macroalgae %
8
Macroalgae %
Parrotfish Biomass g m-2
30
15
10
5
10
0
1
3
5
7
9
Parrotfish Biomass (g m-2)
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Figure 3. HDAR Shallow-water parrotfish stocks and macroalgal cover
Among DAR shallow water survey sites, comparable data was available from 14
locations, and macroalgal cover data was available from 13 of those locations (Figure 3).
Total parrotfish biomass varied from 0.2 g m-2 at Kihei laynet-assessment sites to 8.7 g
m-2 in Manele-Hulopoe Marine Life Conservation District on Maui. There was also a
clear association between low parrotfish biomass and prevalence of macroalgae. Sites
with abundant maroalgae all had < 3 gm-2 of parrotfish biomass, and equally, no site with
> 3 g m-2 of parrotfish had abundant macroalgae, and nearly all such sites had negligible
amounts. Low parrotfish biomass sites tended to be at locations which were open to
fishing, and relatively accessible (i.e. relatively easy to fish), and areas closed to fishing
tended to have healthy parrotfish stocks. However, it was also the case that sites with few
parrotfish also tended to be places near large human population centers, and hence sites
with low parrotfish stocks are likely to also be impacted by other anthropogenic factors
such as eutrophication.
Figure 4. Sites surveyed for MHI-RAMP cruises.
Among the 128 survey sites, grouped into 18 locations, spread widely around the
populated Hawaiian Islands (Figure 4), there was a strong negative association between
human population density adjacent to survey sites, and parrotfish biomass. In addition,
parrotfish community structure appeared to change as local human population increased –
at the most remote and inaccessible locations, parrotfish biomass was nearly totally
dominated by large-bodied species, Chlorurus perspicillatus and Scarus rubroviolaceus,
and smaller-bodied species such as Scarus psittacus and the medium-sized parrotfish,
Chlorurus sordidus, became a more significant part of the parrotfish community at
locations close to human population centers.
VI.
Dissemination of Project results:
Explain, in detail, how the projects results have been, and will be, disseminated.
A. New fundamental or applied knowledge
B. Scientific publications
C. Patents
D. New methods and technology
E. New or advanced tools (e.g. models, biomarkers)
F. Workshops
G. Presentations
H. Outreach activities/products (e.g. website, newsletter articles)
I. Partnerships established with agencies or organizations
No Dissemination to date – this is an interim report. Results will be presented through
public presentations by project staff and by staff of Hawaii DAR beginning June
2008.
Some portion of these results will be presented to DAR staff at a meeting in early
June 08 in Honolulu. The core goal of that meeting is to discuss appropriate bag and
size limits for inshore fishes of particular ecological importance. Herbivorous fishes,
because of their role in providing resilience to macroalgal overgrowth, are clearly one
such group, and hence data shown in Figure 3 (strong negative association between
herbivore biomass and macroalgal cover) and Figure 4 (evidence of significant
depletion of key herbivores around locations with higher local human populations)
are clearly highly relevant.