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AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
1
REPORT 2008-1 May 2008
Community monitoring of reef sharks in
the Coral Sea and Great Barrier Reef,
Australia
Smith, A.K., Welch, D.J. and Rupnik, M.
Australian Underwater Federation
c\14 Cleveland Terrace, Townsville, QLD, Australia, 4810
shark@auf.com.au
Townsville, QLD, Australia, 4810
AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
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Abstract
This report provides preliminary results on 678 reef sharks counted by freedivers
participating in The Great Australian Shark Count (GASC) in the Coral Sea and Great
Barrier Reef waters between October and December 2007. Data reported here were
collected using two different methodologies: Dedicated counts and Opportunistic
counts. The most common species of reef shark counted in the Coral Sea was the
Grey Reef Shark (69%) and the most common species of reef shark counted on the
Great Barrier Reef was the White Tip Reef Shark (25%). The GASC project will
continue throughout 2008 and early 2009 and with increased data collection will
greatly improve the capacity for spatial and potentially temporal comparisons
among species. These are important information gaps for fisheries and marine park
managers.
Background
Australia has an large number of shark species, with at least 167 true sharks
inhabiting Australian waters (Last and Stevens 1994). Sharks are captured by
commercial, indigenous, recreational and game fishers, and in shark control
programs for bather protection. Sharks are taken as target species and as incidental
catch, which is either retained or discarded. In 1998/99, two thirds (66%) of the
quantified Australian shark catch was comprised of just 15 species or groups of shark
species, with the gummy shark contributing the greatest proportion ( 27.7 %) of the
total catch (DAFF, 2004). Sharks are also valued for their intrinsic contribution to
marine ecosystems and tourism. A single shark has been estimated as being worth
between $3,300 and $250,000 to the tourism industry (Chin and Kyne 2007; WWF,
2007)
There are widespread concerns that shark catches in Australia have increased in
recent years, that there is a general lack of scientific information on fished shark
species, and that sharks generally are vulnerable to overfishing and climate change
(AIMS, 2004; Robbins et al, 2006; Chin and Kyne, 2007). Primarily through the
Australian Government Department of the Environment and Water under the
Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act), there have
been recent increases in research activities and in the management of sharks in
response to these concerns. Management responsibility for sharks is shared between
the six State Governments, the Northern Territory and the Australian Government.
The main indicator of stock abundance used in assessments for all the target shark
fisheries is catch per unit effort (CPUE) information from fishers’ mandatory returns
(DAFF, 2004). In recent years non-destructive fishery independent research (eg.
Meekan and Cappo, 2004; DEWHA, 2008) and community monitoring of sharks has
been undertaken for high profile and protected species such as Grey Nurse Sharks,
Great White Sharks and Whale Sharks (Otway, 2001; Unidive 2006; CCSA, 2008;
ECOCEAN 2008). Disagreement and controversy over abundance estimates for grey
nurse sharks, and how thsse data have been interpreted by conservation and
management agencies, has also resulted in legal disputes between stakeholder
groups (NCC, 2007; Recfish Australia, 2007).
AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
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Relatively little research has been undertaken on reef sharks in the Great Barrier Reef
(GBR) and Coral Sea areas (Chin and Kyne 2007; Undersea Explorer, 2007). A recent
study on two of the most common GBR reef sharks, the grey reef shark (Carcharhinus
amblyrhynchos) and the white tip reef shark (Triaenodon obesus), concluded that
abundance of these species had declined dramatically on the GBR (Robbins et al.,
2007). A separate more recent study on reef sharks reported that the catch per unit
effort based on commercial fisheries data had been relatively stable since 1989
(Heupel et al., unpublished data). These studies highlight the need for greater
understanding of the status of reef shark populations on the GBR.
The lack of information on the status of sharks in Australian waters and the need for
better education about the role and importance of sharks in ecosystem integrity led
to the development of “The Great Australian Shark Count”. This is a community
based monitoring program initiated by spearfishers of the Australian Underwater
Federation (AUF) and implemented in October 2007 (AUF, 2007). In the first six
months of this program, over 4000 shark sightings were reported throughout
Australian waters by skindivers (AUF, 2008). This report provides more detail on
sharks counted by freedivers on the GBE and in the Coral Sea between October and
December 2007.
Methods
Underwater visual counts were made of all sharks sighted by skindivers usually
while conducting recreational spearfishing activities. Data reported here were
collected using two different methodologies:
(1) Dedicated counts - A freediver (A. Smith) recorded the species and maximum
numbers of sharks sighted within 30 metres of a group of spearfishers who were
aiming to attract pelagic fish with flashers and berley (Figure 1). This was carried out
during a charter trip to a number of reefs, shoals and seamounts in the Coral Sea and
on the Great Barrier Reef during December 2007 (Figure 2). Some individual sharks
were recognisable due to individual markings (Figures 3, 4). This methodology
minimised double counting the same individual shark. The freediver count used a
methodology similar to a Stationary Point Count (Samoilys and Carlos, 2000), but as
we attract the sharks it is also similar to Baited Remote Underwater Video (AIMS
2004; Meekan and Cappo, 2004). Additional information on time, length, sex and
environmental variables was also recorded where possible (Appendix 1).
Figure 1- A freediver berlying with fish (left); Grey Reef Shark eating berley (middle);
and Grey Reef Shark attracted to flasher (right).
AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
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Figure 2. Map of locations where dedicated counts of sharks were undertaken from
8-15 December 2007.
(2) Opportunistic counts - multiple freedivers recorded information on shark species,
number, size, sex, date, time period, location, water temperature, visibility and depth
observed. These data were reported by freedivers and spearfishers in Queensland
waters between October and December 2007. They reported sightings by logging
onto the Great Australian Shark Count website (AUF 2007). A data verification
process was established where one of the authors checked for possible errors,
duplication and also randomly selected 20% of participants for data verification (by
phone call).
Results
Dedicated Coral Sea shark counts
A total of 443 sharks from 5 species were recorded from 30.5 hours of freediving
(average 14.5 sharks/hour), comprising: 304 Grey Reef HTUCarcharhinus amblyrhynchosUTH
(69%), 91 Whitetip Reef HTUTriaenodon obesusUTH (21%), 45 Silvertip HTUCarcharhinus
albimarginatusUTH (10%), 2 Tiger HTUGaleocerdo cuvierUTH (<1%) and 1 Great Hammerhead
HTUSphyrna mokarranUTH (<1%) Sharks (Table 1, Figure 3) (Table 1). Due to the large number
of sharks, individual lengths and sex were generally not determined; however a size
range was estimated.
AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
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Figure 3- Grey Reef Shark (left) and White Tip Reef Shark (right)
Figure 4. Individual markings on a Grey Reef Shark
Table 1 – Counts of sharks by species, date, location, effort, and comments from the
Coral Sea trip 8-15th December 2007. WT - White Tip, GR - Grey Reef, ST - Silver Tip,
T - Tiger, GH - Great Hammerhead.
Date Location Daily
Effort
(hrs)
WT GR ST Other Total Comment
8/12/07 Bougainville
North
3:20 22 49 17 88
9/12/07 Bougainville 3:10 14 25 39
10/12/07 Holmes 5:00 27 102 1 130 Small GR
11/12/07 Holmes West 3:00 8 25 1 34
11/12/07 Flora North 1:30 13 6 19
12/12/07 Flora SE & W 3:20 12 52 4 1 69 T
13/12/07 McDermott 2:00 3 2 5 T, GH
14/11/07 Seamount 4:30 20 11 31 Hook in ST
15/12/07 Jenny Louise 5:00 8 18 2 28
TOTALS 30.5 91 304 45 3 443
AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
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The interaction rate at three Coral Sea reefs ranged between 11 and 26 sharks per
hour (Figure 3). For each of the three reefs there was some daily and location
variability. The Seamount and Jenny Louise Shoal had an average of 5-7 sharks per
hour. This may be because the Seamount was a small area of about 4 hectares with
the shallowest point at about 28 metres. In contrast, McDermott Bank had the lowest
relative number of sharks with an average of 2.5 diver\hour. This was because there
were no Grey Reef or White Tip Sharks but rather large sharks such as Tiger, Greater
Hammerhead and Silvertips.
Figure 3. Average interaction rate of sharks (all species combined) counted per diver
hour from Coral Sea and Great Barrier Reef.
Opportunistic counts
A total of 235 sharks from 11 species / species groups were recorded
opportunistically by freedivers, comprising 58 Whitetip Reef (25%), 48 Grey Reef
(20%), 39 Whaler group Carcharinus spp (17%), 38 Blacktip Carcharhinus melanopterus
(16%), 20 Tiger (9%), 16 Silvertip (7%) and 16 other (7%) Sharks (Table 2). The
information was grouped according to three locations: Coral Sea, Great Barrier Reef
and South Queensland (Table 2).
Table 2- Summary of location, species and number of sharks, from Queensland
waters (October to December 2007). WT- White Tip, GR- Grey Reef, BT- Black Tip,
WH- Whaler species, ST – Silver Tip, T- Tiger
Location WT GR BT WH ST T Other Total
Coral Sea - 11 4 7 - 12 - 34
Great
Barrier
Reef
58 37 34 24 16 5 2 Wobbegong
4 Tawny
180
South
Qld
- - - 8 - 3 1 Silky
2 Hammerhead
7 Grey Nurse
21
Total 58 48 38 39 16 20 16 235
AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
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Discussion
Diversity and abundance of sharks
There were striking differences in the diversity of and diver interaction rates with
sharks between the various reefs and shoals in the Coral Sea and on the Great Barrier
Reef. General trends from the dedicated count methodology in the Coral Sea were
that Grey Reef Sharks were more common than all other sharks at all reefs, and that
the greatest number of Grey Reef Sharks were at Holmes and Bouganville Reefs. It is
interesting that the Grey Reef Sharks at Holmes Reef were also the smallest observed
(from 50cm, pers. observ) compared to most other locations, and also the most
aggressive, coming to the surface and biting speared fish and approaching close to
freedivers. Whitetip Reef Sharks were not recorded from McDermott shoal and the
Cairns Seamount (Table 1). This finding is consistent with Fishbase (2008), which
considers them to be a sluggish inhabitant of lagoons and seaward reefs, often found
resting in caves or under coral ledges during the day, usually on a sand patch, or in a
channel.
The data from the opportunistic counts (Table 2) is difficult to interpret because of
the different divers, skill, location and effort involved. There were low numbers of
sharks observed from the Coral Sea and South Queensland, but reasonable numbers
(180) from the Great Barrier Reef. The data from the opportunistic counts of sharks
on the GBR indicates that Whitetips were the most common, closely followed by
Grey Reef, Whaler Group and Blacktip Reef Sharks. The primary difference between
the two data sets is that Blacktip Sharks were not recorded during the dedicated
counts.
It is recognised that there has been considerable work done on sharks at Osprey Reef
(Undersea Explorer, 2007), but this research has focussed on length, growth and
movement. There is one published estimate of abundance that states: “The resident
population of sharks at Osprey Reef, the main dive site in the Coral Sea, is 40
animals” (WWF, 2007). However, we have heard anecdotal reports of between 100 to
200 sharks from several freedivers and SCUBA divers at one location known as
“Scuba Zoo” at Osprey Reef (Craig Barnett, Norkat II, pers comm.).
There are no similar community monitoring programs with which to compare our
data here, however there are some scientific studies reporting reef shark abundance
and distribution estimates. Robbins et al. (2000) used underwater visual census of
reef crests on 21 reefs in the northern and central Great Barrier Reef and at the Cocos
Keeling Islands to derive mean reef shark density estimates of between 0.4 and 2 per
hectare for these areas. The total number of sharks observed and the species involved
were not reported in the paper, but it appears that less than 40 sharks were counted.
Despite the small sample sizes, there were significant differences between mean reef
shark abundance from different management zones. The greatest abundance of reef
sharks was reported in no-entry (preservation) zones.
Meeken and Cappo (2004) reported that there was a striking difference in the species
composition and abundance of sharks between Mermaid Reef (closed to fishing) and
Scott Reef (open to fishing) in WA waters. BRUVS recorded 88 sharks from 8 species
in 75 deployments at Mermaid Reef, but only 14 sharks from 5 species in 28
AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
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deployments at Scott Reef. When corrected for sampling effort, the authors estimated
that sharks were, on average, from 4 to 17 times more abundant at Mermaid Reef
than at Scott Reef. Analysis of BRUVS tapes also showed that it took twice as much
time (50 min) at Scott Reef for sharks to appear in the video than at Mermaid Reef,
further suggesting that they were much less abundant at Scott Reef than at Mermaid
Reef (Meekan and Cappo, 2004). One of the few Grey Reef sharks seen at Scott Reef
had a wound in its left jaw that may have been caused by fishing gear.
Implications for future monitoring and management
This baseline data comprises the first monitoring information on relative abundance
and distribution of sharks in the Coral Sea and may be useful for future estimation of
population size. With increasing numbers of reported shark sightings during the
project, there will be increasing utility of the data; however, it is important to
recognise the limitations of the methodology before making valid interpretations.
Some of the issues of community reporting of data include poor species
identification, potential double counting of animals, and recall bias. Most of the data
collected by GASC will be ad hoc (unstructured) reporting, however the Coral Sea
data collected here may provide greater insight into estimates of relative abundance.
The use of underwater diver census methods also has limitations for highly mobile
species such as sharks, where behavioural responses of sharks can greatly influence
sightings and can also be highly variable by location, season, time of day/tide, and
location within a reef. It is possible that a means of attracting sharks within visible
range (by spearfishing and/or berleying) provide more accurate estimates of relative
abundances of sharks, however it is uncertain the extent of reef area that sharks may
be attracted from. Spatial information on species distribution is likely to be of
significant benefit from the GASC project.
The GASC project will continue throughout 2008 and early 2009, and with increased
data collection will greatly improve the capacity for spatial comparisons among
species and hopefully also allow temporal comparisons, particularly between
seasons. These are important information gaps for fisheries and marine park
managers. From even initial data collected we can see benefits from the GASC,
through continuation of the project beyond 2008 will be highly dependent on future
funding.
The Coral Sea and the Great Barrier Reef Marine Park are important areas for all
Australians. These include commercial and recreational fisheries and tourism
operators. A voluntary agreement between commercial fishers and the tourism
industry have been made to not catch fish at Osprey Reef in the Coral Sea (Murphy,
2007). WWF-Australia has a campaign to declare the entire Coral Sea region a Marine
Protected Area (WWF, 2007). The monitoring data from the Great Australian Shark
Count is essential baseline information for fishers, divers, conservationists and
managers to consider in the context of current and future management.
References
AIMS (2004). New study indicates shark numbers under threat. Media release-
March 26, 2004 http://www.aims.gov.au/news/pages/media-release-
20040326.html
AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
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AUF (2007). Great Australian Shark Count. http://www.auf-
spearfishing.com.au/serendipity/auf_index.php accessed on 18PthP April 2008
AUF (2008). Great Australian Shark Count. http://www.auf-spearfishing.com.au/
accessed on 18PthP April 2008
Chin, A., and Kyne, P.M. (2007). Chapter 13. Vulnerability of chondrichthyan fishes
of the Great Barrier Reef to climate change. In Climate Change and the Great Barrier
Reef, eds. Johnson JE and Marshall PA. Great Barrier Reef Marine Park Authority
and Australian Greenhouse Office, Australia.
CCSA (2008). White Shark Count Project.
http://www.ccsa.asn.au/index.php?option=com_content&task=blogcategory&id=1
4&Itemid=73
DAFF (2004). Australian National Plan for the Conservation and Management of
Sharks. http://www.daff.gov.au/fisheries/environment/bycatch/sharkplan
DEWHA (2008). TCarcharias taurusT, Grey Nurse Shark (East Coast population)
http://www.environment.gov.au/biodiversity/threatened/species/c-taurus.html.
Website accessed on 18PthP April 2008.
ECOCEAN (2008). ECOCEAN Whale Shark Photo-identification Library
http://www.whaleshark.org/
Erbe, C. (2000). Census of Marine Mammals. In conference New Technologies for
Observing Marine Life, BC http://pulson.seos.uvic.ca/meeting/scor2000/pres.html
Fishbase (2008). Triaenodon obesus Whitetip reef shark.
http://www.fishbase.org/Summary/SpeciesSummary.php?id=907
Last, P. R., and Stevens, J. D. (1994) Sharks and rays of Australia. 513 pp. (CSIRO
Australia: Melbourne.)
Meekan, M and Cappo, M. (2004). Non-destructive Techniques for Rapid Assessment
of Shark Abundance in Northern Australia. AIMS, Townsville. 36pp.
http://www.aims.gov.au/pages/research/rasana/pdf/rasana.pdf
Murphy, P. (2007). Fishing group to protect reef life. The Australian newspaper. TMay
14, 2007T
http://www.theaustralian.news.com.au/story/0,20867,21725110-2702,00.html
NCC (2007). The Grey Nurse Shark Plight
http://www.nccnsw.org.au/index.php?option=com_content&task=view&id=2218&
Itemid=653
TOtway, N. 2001. Grey Nurse Shark. Nature Australia 26 (12): 20-21.T
AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
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Owen, R., Mitchelmore, C., Woodley, C., Trapido-Rosenthal, H., Galloway, T.,
Depledge, M., Readman, J., Buxton, L., Sarkis, S., Jones, R and Knap. A. (2005). A
common sense approach for confronting coral reef decline associated with human
activities – Editorial. Marine Pollution Bulletin 51. 481-485.
Recfish Australia (2007). Grey Nurse Shark Case Result Sensible
http://www.recfish.com.au/hot_topics/media.html
Robbins, W.D., Hisano, M., Connolly, S.R and Choat, J.H. (2006). Ongoing Collapse
of Coral-Reef Shark Populations. Current Biology 16, 2314-2319.
Samoilys, M.A., Carlos, G. (2000). .Determining Methods of Underwater Visual
Census for Estimating the Abundance of Coral Reef Fishes. Environmental Biology of
Fishes. 57(3): 1573-5133
Undersea Explorer (2007). Shark Research. Great Barrier Reef and Coral Sea. South
West Pacific. http://www.sharkresearch.com/
Unidive (2006). Grey Nurse Shark Project.
http://unidive.org/index.php?option=com_content&task=view&id=38&Itemid=39.
Accessed 18 April 2008.
WWF (2007). Plunder or protection: WWF calls for safeguard of Coral Sea. 17 Sep
2007. http://www.wwf.org.au/news/plunder-or-protection-wwf-calls-for-
safeguard-of-coral-sea/
Acknowledgements
This project has been funded by the Commonwealth Government Recreational
Fishing Community Grant Program. This project is also a contribution to the
International Year of the Reef 2008. The charter trip to the Coral Sea was organised
by Blue Water Hunting International (Rob Torelli). The boat used was the Norkat II
skippered by Craig Barnett and Les Eckart. Photographs used in this report were
taken by Adam Smith, Ben Cropp and Terry Maas. The AUF acknowledges members
of the Steering Committee; Dr Marcus Lincoln Smith, Dr Colin Simpfendorfer, David
Welch and Andrew Chin. The report was provided for peer review to scientists and
managers from AIMS, GBRMPA, JCU, CSIRO and WWF. Particular thanks to Dr
David Pollard for editorial comments.
The AUF acknowledges the support of the following groups for the Great Australian
Shark Count:
AUF (2008) Community monitoring of reef sharks in the Coral Sea and GBR
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Appendix 1 – Data recording sheet
Date: Dive #: Divers:
Time: eg Morning, or 9:30-10am
1
2
3
4
Location
1
2
3
4
GPS
1
2
3
4
Wind: 0 - 5k, 5 - 10k, 10 - 15k,
15 - 20k, 20 - 25k, 25k+
Sky: blue sky, <50% overcast, >50% overcast,
drizzle, moderate rain, heavy rain
Current: eg slight Vis and temp: Depth (m) eg 10-20
Maximum number of sharks sighted (for up to 4 dives)
Data Whitetip Blacktip Grey Reef Whaler Tiger Other
Number
Length
Sex ratio (unknown, M, F)
Number
Length
Sex ratio (unknown, M, F)
Number
Length
Sex ratio (unknown, M, F)
Number
Length
Sex ratio (unknown, M, F)
Number
Length
Sex ratio (unknown, M, F)
Comments:
