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Examining the Impacts of Recreational SCUBA Divers on 1
Subtropical Rocky Reef Systems in Mozambique 2
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Amy O’Briena*, Yara Tibiriçá b, Claire Eatocka. 4
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a Falmouth Marine School, Killigrew Street, Falmouth, Cornwall, TR11 3QS, UK 6
bLemanja – Zavora Marine Lab., Inharrime, Prov. Inhambane, Mozambique 9
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Abstract 12
Reef systems are under threat worldwide from a variety of anthropogenic 13
activities. With an increase in the number of recreational SCUBA divers worldwide 14
more divers seek the warm, clear waters and high biodiversity associated with 15
tropical and subtropical reefs. As a result concerns have been raised regarding the 16
impact this increase in visitors may be having on the health status of reefs globally. 17
We examined the diving behaviour of 85 divers in Zavora, Mozambique to assess 18
correlations between diver characteristics and observed behaviour underwater. 19
Several diver impact studies have been conducted on tropical reefs worldwide, this 20
is the first study to be conducted on subtropical rocky reef systems. The results 21
show that while 87.1% of divers made contact with the reef benthos at least once 22
* Corresponding author. Present address: 1 Burley Court, New Street, Falmouth, Cornwall, TR11 3HJ, UK. Tel.: +441326-317751.
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during the observation period there were no significant correlations between any 23
of the variables analysed. We suggest that a combination of briefings, focused on 24
environmental awareness, and dive staff intervention during dives is required to 25
ensure the sustainability of Zavora’s diverse reef systems. 26
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Keywords: Environmental impact; Marine tourism; Mozambique; Rocky reef; 28
SCUBA diving; Subtropical. 29
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1. Introduction 31
SCUBA diving has been used recreationally since the 1940s (Garrod and Gossling, 32
2008). Recent figures from PADI show that they have certified 18 459 295 divers 33
worldwide since they began operation in 1967 (PADI, 2010). As diving tourism 34
increases so does the potentially damaging impact of inexperienced or careless 35
divers on fragile ecosystems. 36
37
This rise in diver certifications coincides with a significant increase in 38
international tourism which doubled from 1990 to 2009 (UNWTO, 2010). In 2009 39
alone 440 000 000 international tourists were travelling purely for leisure, 40
recreation and holidays (UNWTO, 2010). The development of global travel has 41
exposed previously isolated locations to mass tourism. Provisional figures from 42
the World Tourism Organization suggest that between 2007 and 2009 tourists 43
visiting Mozambique increased by 32% from 771 000 to 2 386 000 (UNWTO, 44
2010). 45
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Mozambique was in a state of civil war from 1977-1992 and consequently has 47
been relatively untouched by the tourism sector until more recent years (Ministério 48
Do Turismo, 2004). As a result the Mozambican coastline, which stretches 49
approximately 2700km along the Indian Ocean, remains relatively undeveloped 50
with areas of comparatively pristine marine life (Tibiriçá et al., In press). Praia de 51
Zavora is located in southern Mozambique and since the opening of the first dive 52
centre in 2008 has developed a reputation as an excellent dive spot with beautiful 53
reefs. These reefs support an abundance of marine life including one of the main 54
attractions, manta rays (Manta birostris and Manta alfredi). Other charismatic 55
species frequenting the productive local waters include whale sharks (Rhincodon 56
typus) and humpback whales (Megaptera novaeangliae), which are a major 57
attraction for tourists and recreational divers (Tibiriçá et al., In press). 58
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Coral reefs are a habitat of global importance. Despite covering as little as 0.2% of 60
the ocean floor coral reefs have been estimated to support 25% of all marine life 61
(Cesar et al., 2003). Reef systems protect the coastline by acting as a natural 62
barrier against strong wave action, yield a high biodiversity of fish species which in 63
turn support local fishing communities and provide the opportunity for 64
communities to capitalise on the growing international tourism industry 65
(Conservation International, 2008; Spalding et al., 2001). Globally, coral reefs are 66
under threat from various impacts including: pollution; sedimentation; 67
unsustainable and damaging fishing methods; climate change; direct physical 68
impacts from activities such as mooring boats and recreational diving. It has been 69
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reported that 60% of the world’s coral reefs are ‘seriously at risk’ from the 70
cumulative impact of anthropogenic stresses (Cesar et al., 2003). 71
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The warm, clear waters supporting coral reef systems make for ideal diving 73
conditions and are a major attraction for divers of all levels of experience (White & 74
Rosales, 2004; Cesar et al., 2004). Various studies have been conducted to assess 75
the impact that recreational divers may be having on coral reefs and also to 76
ascertain which diver characteristics may have a significant impact on the damage 77
caused to the reef. Evidence suggests that certain diver characteristics may have 78
an impact on the number of contacts made with coral and the damage caused. Key 79
characteristics include: diver qualification and experience; gender; attending a 80
dive briefing and the use of underwater photography (Barker and Roberts, 2004; 81
Davis and Tisdell, 1995; Luna et al., 2009; Medio et al., 1997; Rouphael and Inglis, 82
1997, 2001; Uyarra and Cote, 2007; Worachananant et al., 2008). 83
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Roberts and Harriott (1994) found that damage to the reefs was more likely to be 85
caused by inexperienced divers (divers who had logged <100 dives) than more 86
experienced divers. This work has subsequently been supported by the findings of 87
Zakai and Chadwick-Furman (2002) and Barker and Roberts (2004). Male divers 88
have been recorded to cause significantly more damage to coral than female divers 89
(Rouphael and Inglis, 1997, 2001) however the later of the studies demonstrated 90
that females were more likely to contact the substrate with their hands. 91
Conversely, findings by Worachananant et al. (2008) show that females cause 92
significantly more damage to coral. Studies by Davis and Tisdell (1995), Medio et 93
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al. (1997) and Worachananant et al. (2008) conclude that attendance at a pre-dive 94
briefing reduced diver contacts. Barker and Roberts (2004) observed divers after 95
receiving a “one sentence environmental briefing” and found that it had no impact 96
on the contact rate but found dive leader intervention to have a significant impact. 97
The length and content of the briefing is likely to have influenced the results of 98
these studies. Barker and Roberts (2004) found that underwater photographers 99
caused significantly more damage to the reef than non-photographers however 100
photographer experience (non-specialist or specialist) had no significant effect. 101
Medio et al. (1997), Worachananant et al. (2008) and Luna et al. (2009) also found 102
photographers made significantly more contacts with the reef than non-103
photographers. 104
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Several studies have found fin kicks to be the most common cause of unintentional 106
contact with the reef whilst the divers’ hands were used most frequently to 107
intentionally touch the substrate (Barker and Roberts, 2004; Luna et al., 2009; 108
Medio et al., 1997; Worachanant et al., 2008). 109
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The aim of this study was to assess the direct impact of recreational SCUBA divers 111
on the reef systems of Praia de Zavora, Mozambique. The study used trained 112
interns to observe the behaviour of divers in order to examine the effect of certain 113
diver characteristics on the rate of contact and any subsequent damage caused to 114
the reef benthos. 115
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2. Methodology 117
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2.1 Study site and diver samples 118
SCUBA divers were observed from March 2010 to January 2011 at Praia de Zavora, 119
Inhambane, Mozambique. Divers were accompanied on their dives by Y. Tibiriçá 120
and one or two trained interns. Tibiriçá lives at the location and heads a scientific 121
internship program whilst conducting environmental talks for guests at the local 122
resort and for children at a nearby school. Many of the divers were aware that 123
Tibiriçá was sampling the area for biodiversity and of the involvement of interns 124
however, all of the observed divers remained unaware of the specific nature of the 125
research. When asked about the research interns only discussed manta ray 126
identification or the health status of the reefs. During the dive the observers 127
buddied up and became a natural part of the dive groups. These measures were 128
taken to prevent any changes in the behaviour of the divers due to the presence of 129
the observers. To reduce bias in data collection Tibiriçá trains all of the interns on 130
site and monitors their work. 131
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Divers were chosen using stratified random sampling. On each dive one diver was 133
observed from their entry into the water for 30 consecutive minutes, or until they 134
began their ascent (whichever came first). Towards the end of their stay in Zavora 135
all divers were also asked to complete a questionnaire to determine many factors 136
including; dive history, dive experience in Zavora, purpose of the visit to 137
Mozambique and Zavora. 138
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2.2 Dive sites 140
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All of the divers were diving with MozDivers who took guests to a variety of 141
inshore and offshore dive sites all of which were accessed by boat. The depths at 142
the dive sites varied from 7 to 33 metres. The dive sites were usually determined 143
prior to launching the boat based on the weather and sea conditions and guest 144
specifications and experience. The appropriate briefing was given by the 145
divemaster to all divers prior to leaving the dive centre. This included a mention 146
of the dive company’s no-glove policy aimed at deterring divers from touching the 147
reef. 148
149
2.3 Factors Recorded 150
At each dive site observations were made about the physical conditions and 151
nearby activity including: time, location, weather, wind, air temperature, surface 152
and bottom water temperature, boat activity within 1km of the site, current and 153
wave impact on a scale of 1-5, underwater visibility and key species observed 154
during the dive. 155
156
Some diver characteristics (gender, possession of a camera) were recorded prior 157
to the dive. Divers with photography equipment were classified as amateur if they 158
were using a basic point and shoot camera or professional if the equipment was 159
more advanced, videographers were also recorded. During the observation period 160
all contact made underwater by the diver was recorded as well as the time into the 161
dive, the depth at which the contact took place, the part of the diver’s body 162
involved in the contact, the type of substrate affected, whether it was intentional or 163
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unintentional and the result of the contact (no damage, abrasion, breakage or 164
sediment disturbance). 165
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2.4 Statistical Analysis 167
SPSS was used to conduct Spearman’s rank correlation to explore the relationships 168
between the recorded diver characteristics (gender, number of dives logged, dive 169
qualification, camera possession) and each of the following sets of observed data: 170
number of contacts made with the substrate (contacts min-1); intentional contacts 171
(contacts min-1); intentional living contacts (contacts min-1); intentional not living 172
contacts (contacts min-1); unintentional contacts (contacts min-1); unintentional 173
living contacts (contacts min-1); unintentional not living contacts (contacts min-1). 174
Microsoft excel was used in conjunction with StatPlus to generate descriptive 175
statistics. 176
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3. Results 178
3.1 Diver Characteristics 179
In total 85 divers were observed underwater for 30 minutes, or until ascent, 180
starting from their entry into the water. A majority (74.1%, n=63) of divers 181
observed were male. Table 1 shows the division of divers into four experience 182
groups based on the total number of dives they have logged (Worachanant et al., 183
2008). Under this classification the majority of the observation subjects (68.2%, 184
n=58) are considered expert divers having logged over 100 dives. Comparatively, 185
diver experience may also be determined using the individuals dive qualification 186
(Table 2). The observed divers were mainly qualified to ‘advanced’ level (49.4%) 187
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with far fewer divers at either end of the spectrum. However this classification 188
may not be a true representation of experience as any two divers with the same 189
qualification may have logged a different number of dives. 190
191
Of the 85 divers observed 51.8% (n=44) were photographers, of those: 61.4% 192
(n=27) amateur; 20.5% (n=9) professional; 18.2% (n=8) videographers. 86.4% of 193
divers in possession of underwater photography or filming equipment were male. 194
67.4% (n=58) of the observed divers also returned completed questionnaires at 195
the end of their stay in Zavora. 196
197
3.2 Observed Diver Behaviour 198
Overall, 87.1% (n=74) of the divers observed made contact with the substrate at 199
least once during the observation period, with a mean contact rate (contacts min-1) 200
of 0.18 ± 0.02 (mean ± S.E.) and a median of 0.11 contacts min-1. 201
202
Of the contact observed underwater 47.1% (n=208) were made by fins, closely 203
followed by 39.1% (n=173) of contacts being made by hand (Figure 1). 25% 204
(n=52) of fin contacts and 67.1% (n=116) of hand contacts were made to rock. 205
46.6% (n=97) of fin contacts compared to 14.5% (n=35) of hand contacts were 206
made to living organisms (Figure 2). 207
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Of all the contacts made with the substrate 62.4% (n=252) resulted in no 209
noticeable damage. 28.7% of contacts with the substrate resulted in damage 210
(breakage or abrasion) and 8.9% of substrate contacts disturbed the sediment. 211
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3.3 The Impact of Diver Characteristics on Diver Behaviour 213
Analysis of the data, using Spearman’s Rank Correlation on SPSS, revealed that 214
there were no correlations between each of the observed diver characteristics 215
(gender, number of dives logged, dive qualification, camera possession) and each 216
of the observed data sets. 217
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3.4 Diver profiles 219
Upon finding no correlations between the diver characteristics and the observed 220
data the profiles of the 10 divers with the highest contact rate (contacts min-1) 221
were isolated and examined (Table 3). This diver sample is 11.8% of the total 222
observation sample and accounts for 39.3% of contacts with the substrate 223
(contacts min-1). This sample set was compared with the profiles of the 10 most 224
damaging divers, those with the highest damage (combined breakage and 225
abrasion) rate (damages min-1) (Table 4). 90% of the divers ranked as the top 10 226
most frequent to contact the substrate were classified as ‘experts’ and were 227
responsible for almost half (44.4%) of the damage caused to the substrate. 228
Analysis of the top 10 profiles reveals that 91.2% of damages were caused by 229
11.8% of the observation sample. Further analysis of the whole data set shows 230
that 16.5% of the divers observed are responsible for 100% of the substrate 231
damages. 4 of the divers profiled appeared in both sample sets: 3 were ‘expert’ 232
divers and 1 was a ‘beginner’. 233
234
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4. Discussion 235
In this study diver contact with the substrate was common, occurring in 87.1% of 236
the diver surveys, but a majority of the contacts (62.4%) resulted in no damage. 237
Only 2.2% of contacts with the reef benthos resulted in coral breakage. A similar 238
result was also recorded by Talge (1991), who observed 90% of divers contacting 239
the reef with only 2% causing damage to corals, and Barker and Roberts (2004) 240
who recorded coral breakages in only 4.1% of substrate contacts. This study found 241
that 39.1% of all substrate contacts were made with rock. The reef systems at 242
Zavora are not true coral reefs. They are rocky reefs composed of limestone rock 243
which supports a range of flora and fauna including an array of coral species 244
(Tibiriçá, Personal communication). As a result parts of the reef may appear as 245
just rock but on closer inspection this rock may in fact support a vast range of 246
micro-organisms (Figure 3). Therefore further investigation is required to 247
establish whether diver contact with rock is actually having more of an impact on 248
the reef community than first meets the eye. 249
250
Concurring with previous studies (Barker and Roberts, 2004; Harriott et al., 1997; 251
Roberts and Harriott, 1994; Rouphael and Inglis, 2001; Worachanant et al., 2008; 252
Zakai and Chadwick-Furman, 2002) the largest single cause of contact with the 253
substrate was by fins (47.1%). 93.3% (n=194) of the fin contacts were 254
unintentional indicating a lack of diver control of buoyancy. However, the 255
proportion of fin contacts is substantially lower than the 81.4% recorded by 256
Barker and Roberts (2004). Their observation sample size was high in the Basic 257
category compared to Advanced, Leader and Instructor categories of divers and 258
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their data showed a significant positive correlation with number of dives logged 259
(dive experience) and contact rate (Barker and Roberts, 2004). If fin contacts with 260
the substrate are an indication of divers with poor technique (e.g. swimming and 261
buoyancy control) then the lower figure found in this study may be explained by 262
the high number of divers in the ‘expert’ category of this sample (Table 1). The 263
second most frequent contact made underwater in this study was by divers’ hands 264
(39.1%). The vast majority (97.1%) of these contacts were intentional of which 265
83.9% resulted in no damage. Again this may be an indication of more 266
experienced or environmentally conscious divers. Findings by Worachanant et al. 267
(2008) showed similar findings with 41.4% of contacts caused by fins and 31.1% 268
caused by hand. 269
270
Rouphael and Inglis (2001) hypothesised that divers using underwater cameras 271
would cause more damage to corals than those who did not due to a lack of proper 272
buoyancy control near to and an eagerness to get closer to the substrate. This 273
study found no such trend. 274
275
The disturbance and re-suspension of sediment occurred in 26.2% of contacts 276
observed during the surveys. Prior research suggests that long-term sediment 277
accumulation can have a negative impact on reef dwelling organisms (Rogers, 278
1990). Particularly susceptible to localised increases in turbidity are sessile 279
species such as corals and sponges. Sedimentation may also smother or abrade 280
organisms, reduce settlement opportunities or reduce the growth and 281
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reproduction rate of corals as a higher proportion of energy must be used to expel 282
the sediment (Luna-Perez et al. 2010; Rogers, 1990). 283
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5. Conclusion 285
While other studies have identified links between diver behaviour and various 286
diver characteristics this study has found no such correlations. Of particular 287
interest in this study is the high number of ‘expert’ divers whose dive experience 288
would suggest a greater ability to control their movement underwater and 289
therefore exhibit a reduced rate of damaging contacts. Although only a minority of 290
individuals (12.9%) caused breakages 72.7% (n=8) of them were classified as 291
‘expert’ divers and none of them were considered ‘beginners’ (having completed 292
<25 dives). The lack of correlations combined with diver profile observations in 293
this study indicates that experienced divers are not necessarily practicing good 294
diving behaviour. This may be due to preconceptions they have regarding 295
appropriate diving behaviour being based on their own experience and 296
assumptions rather than being based on current knowledge. In this case a little 297
education could go a long way. 298
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Regardless of dive experience, dive qualification, gender or camera possession 300
divers need to be educated thoroughly on the local environment and specific dive 301
sites prior to diving and monitored for the duration of their dive by local dive staff 302
who should be prepared to intervene when appropriate (shown to be effective by 303
Davis and Tisdell, 1995; Medio et al., 1997; Worachanant et al., 2008). Establishing 304
good management techniques and standard diver protocol is of particular 305
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importance with the prospect of two new dive centres to be opened in Zavora 306
within the next year (Tibiriçá, Personal communication). 307
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6. Acknowledgements 309
We are grateful to the management and staff at MozDivers and Zavora Lodge for 310
allowing interns and Y.Tibirica to accompany guests on their dives to collect the 311
data. We also extend a sincere thank you to all of the interns for their help in the 312
field and all of the divers who gave their time to answer questionnaires. Thank 313
you to Edward O’Brien and Katie Sambrook for thoroughly proofreading and 314
critiquing this article. This research has been part-funded by Oceans Research, 315
South Africa. 316
317
7. References 318
Barker, N.H.L., Roberts, C.M., 2004. Scuba diver behaviour and the management of 319
diving impacts on coral reefs. Biological Conservation. 120, 481-489. 320
Cesar Environmental Economics Consulting, 2003. The economics of worldwide 321
coral reef degradation. Arnhem: CEEC. 322
Cesar, H.S.J., van Beukering, P., Pintz, S., Dierking, J., 2004. Economic valuation of 323
the coral reefs of Hawai'i. Pacific Science. 58, 231-242. 324
Conservation International, 2008. Economic Values of Coral Reefs, Mangroves, and 325
Seagrasses: A Global Compilation. Arlington: Conservation International. 326
Davis, D., Tisdell, C., 1995. Recreational scuba-diving and carrying capacity in 327
marine protected areas. Ocean and Coastal Management. 26, 19-40. 328
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Garrod, B., Gossling, S., 2008. New Fronteirs in Marine Tourism: Diving 329
experiences, Sustainability, Management. Amsterdam: Elsevier Ltd. 330
Harriott, V., Davis, D., Banks, S., 1997. Recreational diving and its impact in marine 331
protected areas in Eastern Australia. Ambio. 26, 173–179. 332
Luna-Pérez, B., Valle, C., Vega Fernández, T., Sánchez-Lizaso, J.L., Ramos-Esplá, A.A., 333
2010. Halocynthia papillosa (Linnaeus, 1767) as an indicator of SCUBA diving 334
impact. Ecological Indicators. 10, 1017-1024. 335
Luna, B., Pérez, C.V., Sánchez-Lizaso, J.L., 2009. Benthic impacts of recreational 336
divers in a Mediterranean Marine Protected Area. Journal of Marine Science. 66, 337
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to corals by scuba divers. Biological Conservation. 79, 91–95. 340
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República De Moçambique: Ministério Do Turismo. 345
Roberts, L., Harriott, V.J., 1994. Recreational scuba diving and its potential for 346
environmental impact in a marine reserve. In: Bellwood, O., Choat, H., Saxena, N. 347
(Eds), Recent Advances in Marine Science and Technology 1994. James Cook 348
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Rogers, C.S., 1990. Responses of coral reef organisms to sedimentation. Marine 350
Ecology Progress. 62, 185–202. 351
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different reef topographies. Biological Conservation. 82, 329-336. 353
Rouphael, A.B., Inglis, G.J., 2001. ‘‘Take only photographs and leave only 354
footprints’’?: an experimental study of the impacts of underwater photographers 355
on coral reef dive sites. Biological Conservation. 100, 281-287. 356
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at the UNEP World Conservation Monitoring Centre. University of California Press, 358
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Worachananant, S., Carter, R.W., Hockings, M., Reopanichkul., P., 2008. Managing 371
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376
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Table 1. Dive Experience of Observed Divers 377 Groups Frequency Percentage
Beginners (1-25) 12 14.1
Novices (26-50 dives) 7 8.2
Enthusiasts (51-100 dives) 8 9.4
Experts (more than 100 dives) 58 68.2
Total 85 100
378
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Table 2. Level of Diver Qualification 379 Qualification Level Frequency Percentage
Open Water 7 8.2
Advanced 42 49.4
Rescue 14 16.5
Divemaster 11 12.9
Instructor 7 8.2
Other (e.g. technical) 4 4.7
Total 85 100
380
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381 Figure 1. The Cause of Diver Contacts 382
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
45.0
50.0
Fin Hand Reg Cylinder Knee Other
Pe
rce
nta
ge
(%
)
Contact Cause
Fin
Hand
Reg
Cylinder
Knee
Other
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383 Figure 2. The Cause and Object of Diver Contact 384
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
80.0
90.0
100.0
Fin Hand Reg Cylinder Knee Other
Pe
rce
nta
ge
(%
)
Contact Cause
Hard Coral
Sponge
Soft Coral
Algae
Diver
Other
Silt
Sand
Rock
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Table 3. Profiles of the 10 divers with the highest contact rate 385
Rank Substrate contact rate
(min-1) Highest
Certification Total Logged
Dives Gender
Camera Possession
1 1.00 2 500 Male Amateur 2 0.89 5 970 Male Video 3 0.82 5 970 Male Video 4 0.67 2 25 Female No 5 0.57 3 245 Male Prof 6 0.40 2 150 Male No 6 0.40 3 200 Male Prof 6 0.40 3 200 Male Prof 6 0.40 6 495 Male Amateur
10 0.38 4 350 Male Amateur
386
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Table 4. Profiles of the 10 divers with the highest damage rate 387
Rank Damage Rate (min-1) Highest
Certification Total Logged
Dives Gender
Camera Possession
1 0.28 2 12 Male No 2 0.26 5 970 Male Video 3 0.23 2 25 Female No 4 0.21 2 340 Male Video 5 0.18 5 970 Male Video 6 0.13 2 150 Male No 7 0.10 4 110 Male No 8 0.07 2 36 Male Amateur 9 0.06 2 38 Male No
10 0.05 4 200 Male Amateur
388
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389 Figure 3. Photograph demonstrating the range of micro-organisms which can be found 390
upon closer inspection of the ‘rock’. 391