BAITED REMOTE UNDERWATER REMOTE
SURVEY OF RICK MILLS AND BOTTLE
WASHER ARTIFICIAL REEFS, 2011-2013
(DARWIN HARBOUR, AUSTRALIA).
This document was prepared for the Department of Land Resource
Management. Contributing author Dr Victor Gomelyuk
© Copyright of the Northern Territory Government, 2014.
Permission to copy is granted provided the source is acknowledged.
ISBN: 978-1-74350-062-0
Further information
Contact:
Dr Victor Gomelyuk
Marine Ecosystems, Flora and Fauna Division
Dept. of Land Resource Management
564 Vanderlin Drive BERRIMAH NT 0828
Mail to:
PO Box 496, PALMERSTON, NT 0831, Australia
Ph: +61 8 8995 5024
fax +61 8 8995 5099
Cite report as:
Baited remote underwater remote survey of Rick Mills and Bottle Washer artificial reefs,
2011-2013 (Darwin Harbour, Australia).
ii
Executive summary
Biodiversity and abundance of fish communities were assessed using baited remote
underwater system (BRUVS), at Rick Mills and Bottle Washer artificial reefs in Darwin
Harbour in 2011-2012. “Artificial reef effect” was evident at Bottle Washer artificial reef.
Assemblages of sharks and of fishes targeted by amateur anglers and skindivers as well as
reef-associated fishes were more abundant and contained more species at sites adjacent to
the reef than at sites located away from the reef. “Artificial reef effect” was far less evident at
Rick Mills artificial reef. No statistically significant differences in fish abundance were found
between sites close to the reef, but located at different distances from the reef when all fish
fauna has been compared. Surprisingly, overall biodiversity was considerably higher at the
site located 520 m away from artificial reef. Both mean fish abundance and biodiversity of
sharks and fish targeted by anglers and skindivers did not differ significantly among sites
close to artificial reef and more distant site. As for reef-associated fish species the results
were equivocal: mean biodiversity was significantly higher at the site closest to the reef
comparing to second site near the reef. However, no differences have been found in site
closest to the reef and the most distant site (520 m away from the reef) comparisons. No
differences were found in mean reef-associated fish abundance for all compared sites.
There are several possible explanations for our results:
•
Specific of fish fauna in inshore water of Darwin Harbour
•
Relatively short period of both artificial reef constructions.
•
Relatively large distances of sampling sites from AR
Still, Rick Mills and Bottle Washer artificial areas have twice higher fish biodiversity and
almost three times higher overall fish abundance comparing to other monitoring sites in
Darwin Harbour in 2011-2013.
iii
Contents
Executive summary ............................................................................................................... iii
Contents ................................................................................................................................ iv
INTRODUCTION ....................................................................................................................7
MATERIAL AND METHODS ..................................................................................................8
Area description. .................................................................................................................8
BRUVS survey procedure. ................................................................................................11
Underwater video interrogation. ........................................................................................11
Data analysis. ...................................................................................................................11
RESULTS .............................................................................................................................13
Descriptive results.............................................................................................................13
1.
All fish assemblages abundance and biodiversity. .....................................................13
Rick Mills area. .............................................................................................................13
Univariate analyses. .....................................................................................................13
Multivariate analyses. ...................................................................................................16
Analysis of Similarity (ANOSIM). ...................................................................................16
Similarity per cent analysis (SIMPER). ..........................................................................16
Bottom Washer area. ....................................................................................................22
Univariate analyses. .....................................................................................................22
Multivariate analyses. ...................................................................................................24
Analysis of Similarity (ANOSIM). ...................................................................................24
Similarity per cent analysis (SIMPER). ..........................................................................24
2.
Species targeted by anglers and divers abundance and biodiversity. ........................29
Rick Mills area. .............................................................................................................29
Univariate analyses. .....................................................................................................29
Multivariate analysis. ....................................................................................................31
Analysis of Similarity (ANOSIM). ...................................................................................31
Similarity per cent analysis (SIMPER). ..........................................................................31
Bottle Washer area. ......................................................................................................34
Univariate analyses. .....................................................................................................34
Multivariate analysis. ....................................................................................................36
Analysis of Similarity (ANOSIM). ...................................................................................36
Similarity per cent analysis (SIMPER). ..........................................................................36
Reef-associated fish species abundance and biodiversity. ................................................39
Rick Mills area. .............................................................................................................39
Univariate analyses. .....................................................................................................39
iv
Multivariate analysis. ....................................................................................................42
Analysis of Similarity (ANOSIM). ...................................................................................42
Similarity per cent analysis (SIMPER). ..........................................................................42
Bottle Washer area. ......................................................................................................45
Univariate analyses. .....................................................................................................45
Multivariate analysis. ....................................................................................................47
Analysis of Similarity (ANOSIM). ...................................................................................47
Similarity per cent analysis (SIMPER). ..........................................................................48
DISCUSSION ...................................................................................................................51
All fish assemblages spatial distribution. .......................................................................51
Fishes targeted by anglers and divers. .........................................................................51
Reef-associated fish species abundance and biodiversity. ...........................................51
Multivariate analyses of fish assemblages at different sampling sites. ..........................51
CONCLUSION. ....................................................................................................................53
APPENDIX ...........................................................................................................................56
v
List of Figures
Figure 1. Position of artificial reefs Rick Mills and Bottle Washer and BRUVS sampling sites
within each artificial reef area during 2011-2013 studies. .......................................................9
Figure 2. Mean number of all recorded fish (MaxN) at different sampling sites at Rick Mills
artificial reef area. Error bars are standard deviation. ...........................................................14
Figure 3. Mean number of all recorded fish species at different sampling sites at Rick Mills
artificial reef area. Asterisks indicate significance level: * - 0.05 – 0.01; ** - < 0.01 – 0.001; ***
- <0.001 ................................................................................................................................14
Figure 4. Mean number of all recorded fish (MaxN) at different sampling sites at Bottle
Washer artificial reef area. ....................................................................................................23
Figure 5. Mean number of all recorded fish species at different sampling sites at Bottle
Washer artificial reef area. ....................................................................................................23
Figure 6. Mean number (MaxN) of sharks and fish targeted by anglers and skindivers at
different sites at Rick Mills artificial reef area. .......................................................................30
Figure 7. Mean number of species of sharks and species of fish targeted by anglers and
skindivers at different sites at Rick Mills artificial reef area. ...................................................30
Figure 8. Mean number (MaxN) of sharks and fish targeted by anglers and skindivers at
different sites at Bottle Washer artificial reef area. ................................................................35
Figure 9. Mean number of sharks species and fish species targeted by anglers and
skindivers at different sites at Bottle Washer artificial reef area. ...........................................35
Figure 10. Mean number (MaxN) of reef-associated fish recorded during BRUVS survey at
different sites at Rick Mills artificial reef area in2011-2013....................................................40
Figure 11. Mean number of reef-associated fish species recorded during BRUVS survey at
different sites at Rick Mills artificial reef area in 2011-2013...................................................41
Figure 12. Mean number (MaxN) of reef-associated fish recorded during BRUVS survey at
different sampling sites at Bottle Washer artificial reef area in 2011-2013. ...........................46
Figure 13. Mean number of reef-associated species of fish recorded during BRUVS survey at
different sampling sites at Bottle Washer artificial reef area in 2011-2013. ...........................46
List of Tables
Table 1. Sampling sites at Rick Mills and Bottle Washer artificial reefs during fish
assemblages of Darwin Harbour BRUVS survey in 2011-2013.............................................10
vi
INTRODUCTION
Darwin Harbour is undoubtedly the most important location for recreational fishing in the
Northern Territory and more than 30% of all recreational fishing in the Territory takes place
in Darwin Harbour, Shoal Bay and nearby areas (Coleman 2003).
Shipwrecks and artificial reefs are important component of Darwin Harbour habitat. The
seafloors in the harbour generally are broad featureless expanses of soft-bottom, fringed by
occasional rocks. The highest concentration of fish can usually be found around natural
reefs, ledges, shipwrecks, virtually any underwater structures (jetties. pontoons, pipelines,
etc.) or any anomalies on the seabed. Underwater structures and fish assemblages
associated with AR in Darwin Harbour attract both divers and fishers.
The costs and logistical difficulties involved in conducting surveys of reef fish assemblages
in the Northern Territory are such that few reef fish surveys have taken place, a situation
which must be addressed if we are to develop effective management strategies for these
important components of the marine biota. Remote ‘video fishing’ techniques using baited
remote underwater video system (BRUVS) will be employed in this study. BRUVS offer
standardised, non-extractive methodologies for estimating the relative fish abundance
(Cappo et al. 2004, 2007; Gomelyuk, 2008, 2012).
Fish fauna in inshore areas of Northern Territory include species from a variety of ecological
groups and many of them have a complex life history, with different habitat preferences
during different stages of their life cycle (Blaber 1986, Robertson and Duke 1987, Blaber et
al. 1989, Sheaves 1995). However, all variety of habitat preferences of inshore fishes can be
conditionally divided into next categories:

Ubiquitous species with broad distribution; some species juveniles and sub adults in
estuaries and river mouths.

Species found on soft bottoms habitats and/or seagrass beds.

Species found mainly on coral and rocky reefs and/or on sandy areas adjacent to the
reef.

Species usually found in brackish waters estuaries and sometimes entering river
mouths.
As all humane-made underwater construction do, Rick Mills and Bottle Washer artificial reefs
create high profile bottom habitat and expand area of habitat available for colonization by
sessile benthic organisms as well as shelter and foraging area for “reef-associated fishes.
7
Both AR are surrounded by areas of low profile soft bottom habitat. Substantial reef
expansion done in 2011 further increased habitat complexity.
It was reasonable to presume that abundance and biodiversity of reef fishes will be higher at
sampling sites in close vicinity of artificial reefs, the close to AR construction, the higher
abundance and biodiversity. As for distribution of ubiquitous species, species associated
with soft-bottom habitat, we expected no significant differences among BRUVS sampling
sites within each artificial reef area.
The aim of present study was to assess “artificial reef effect” on fish species targeted by
amateur anglers and skindivers and sharks as significant component of inshore ecosystems
by assessing and comparing fish diversity and abundance in assemblages in close vicinity of
“Rick Mills” and “Bottle Washer” artificial reefs and sites located away from artificial reefs.
MATERIAL AND METHODS
Area description.
Both Rick Mills and Bottle Washer artificial reefs were established two decades ago and
expanded by Department of Fisheries in 2011. They located to north-west off Lee Point,
Figure 1. Open low profile sandy and muddy habitat with some rare sea grass is typical for
the area; scarce rocky outcrops, boulders and the hard coral rubbles buried in sediments
with attached macro algae, hydroids occur in the area, but the only extensive
(approximately, 9800 square metres) natural reef is Anglers Reef located 1.3-1.5 km to the
south-east from “Bottle Washer” artificial reef. To obtain a representative samples, three
sites were randomly chosen at each reef. For Rick Mills they were site within 50 m form
artificial reef culvert, site 70 m from nearest artificial reef culvert and site 520 m away from
nearest artificial reef culvert. For “Bottle Washer” one site were within 20 m of artificial reef
culvert, 570 m away from nearest culvert and 160 m away from nearest artificial reef culvert,
Table 1.
All surveys were conducted in September 2011 - September 2013 during neap tides to avoid
high tidal currents and increased water turbidity during spring tides. Surveys were conducted
in daytime (between 8:00 hours and 15:00 hours). A Global
8
Figure 1. Position of artificial reefs Rick Mills and Bottle Washer and BRUVS
sampling sites within each artificial reef area during 2011-2013 studies.
9
Table 1. Sampling sites at Rick Mills and Bottle Washer artificial reefs during
fish assemblages of Darwin Harbour BRUVS survey in 2011-2013.
Rick Mills Artificial Reef Location
7
1-st site at Rick 12–12.5
Open sandy–muddy bottom approximately 50 m
Mills location
from artificial reef culvert. Some hydroids,
occasional polychaetes worm tubes
8
2-nd site at Rick 11–12.5
Open sandy–muddy bottom approximately 70 m
Mills location
from artificial reef culvert. Scarce (less than 1%
habitat cover) hydroids, sponges.
9
3-rd site at Rick 12 –12.7
Open sandy–muddy bottom, approximately 520
Mills location
m away from nearest artificial reef culvert.
Scarce hydroids, occasional soft corals, macro
algae. In some areas per cent cover of sessile
organism was up to 30%, usually 3-5%.
Bottle Washer Artificial Reef Location
10 1-st site at Bottle 11–12
Washer
artificial
reef
Located approximately 20 m from artificial reef
culvert Open sandy–muddy bottom with some
occasional gravel areas. Less than 1% hydroids,
hard coral rubble and algae.
11 2-nd site at Bottle 11–12
Washer
artificial
reef
Located on sandy–muddy bottom approximately
570 m from artificial reef culvert. From 1 to 3%
of hydroids, ascidians and macro algae on
occasion hard coral rubble and very scarce
rocks.
12 3-rd site at Bottle 10–11
Washer
reef
artificial
Open sandy–muddy bottom approximately 160
m away from artificial reef. Less than 1%
hydroids, very scarce sea whips, hard coral
rubble and algae.
10
Positioning System device was used to navigate to each site. The average accuracy of this
device is ±5–7 m. Depth was measured using the boat depth sounder. The BRUVS gear
used in the survey and the sampling procedure was described in a previous report
(Gomelyuk 2014).
BRUVS survey procedure.
At each site, one of the BRUVS apparatus was deployed for video survey (Cappo et al.
2003). The BRUVS remained on the sea floor for 60 minutes, and recorded fish attracted to
the bait canister. Site name, date, the time when survey was started and finished, the depth
and BRUVS device ID number were recorded. Because of relatively large distances between
selected sampling sites and because two BRUVS were never used at the same site, video
replicates were independent (e.g. same fish were unable to visit more than one BRUVS
during the survey). Six one-hour underwater video samples (i.e. replicates) were taken at
each of sampling site each year.
Underwater video interrogation.
An interrogation of video was done according to Cappo et al. (2003, 2004). All 60 minutes of
video were screened and each new fish species arriving in the field of view of the camera
was recorded. Only the maximum number of individuals of each species seen together in the
field of view at one time (MaxN) was used in analyses to avoid the possibility of fish double
counting. According to previous studies (Priede & Merrett 1996; Willis & Babcock 2000
Cappo et al. 2003, 2004; 2007, 20011, Watson et al. 2005), MaxN gives a conservative
estimate of fish relative density. Images of the sea bottom were used to identify different
types of bottom cover. In Darwin Harbour this can vary from hard coral, rocks, pebbles and
gravel to sand, silted sand and silt, depending on the depth and location at survey site.
Where possible, fish were identified to species level. Atlas of Living Australia
http://biocache.ala.org.au database
was used as a main source of information on the previous records of fish species in Darwin
Harbour and Northern Territory waters. International Code of Zoological Nomenclature
(1999) and the list of standardised Australian fish names
http://www.marine.csiro.au/caab/namelist.htm was used in this report. ”Checklist of Darwin
Harbour fishes” (Larson 1997) and Atlas of Living Australia
http://biocache.ala.org.au/occurrences/search?taxa were used in this study.
Data analysis.
Data for each sampling site collected in 2011-2013 was pooled to increase the power of
analysis, to compensate possible natural variation (related to fish movement) and to make
11
the data more generalizable. Prior to pooling the data at each site was tested for treatmentby-time interaction, which might be present and would constrain the generalizability of the
finding (Knapp 2013). In all tests no such interactions were found.
Univariate statistics and descriptive statistics were completed with SYSTAT 13 software ®
(2009 SYSTAT Software Inc., Point Richmond, CA, USA). Analysis of variance (ANOVA)
was used to compare differences among compared sites in fish abundance (MaxN) and
species richness (the number of fish species recorded in each 60-minites video sample).
Data were examined for normality and homogeneity of variances using Kolmogorov-Smirnov
test (Lilliefors) and Levene's test. In order to decrease possibility of Type I error one fixed
factor (factor-different monitoring sites in 2011-2012) was used. Tukey’s multiple comparison
tests (HSD) was used for pairwise comparison.
Contrary to univariate statistical analysis that compare either fish abundance or species
abundance, multivariate analysis compare fish assemblages composition and structure.
Multivariate analyses were carried out with statistical package PRIMER 6.0 & PERMANOVA
+ for PRIMER ® (2012 PRIMER-E Ltd., Plymouth, UK (Clarke & Warwick 1994; Anderson,
Gorley and Clarke 2008).
PERMANOVA is a program for testing the simultaneous response of one or more variables
to one or more factors in an ANOVA experimental design on the basis of any distance
measure, using permutation methods. First, the program calculates the distances between
each pair of observation units (sampling units) to obtain a distance matrix. It then calculates
the test-statistics from this according to the relevant experimental design. (Anderson 2001).
One fixed factor (different sampling sites) design was used in this analysis. As ANOVA,
PERMANOVA comparison of 2011-2012 data was done for sites with pooled data from three
monitoring sites at each artificial reef.
Analysis of similarity (ANOSIM) uses The Bray-Curtis similarity matrix which depends on the
relative order (i.e., ranking) of the similarity coefficients in the Bray-Curtis similarity matrix,
rather than their absolute values. The ANOSIM was used to determine whether the fish
assemblages differed statistically among compared sites. The ANOSIM test statistic, R, is
based on the ratio of the between-group to within-group similarity ranking. Pair wise
comparison tests are also calculated which generate an R value and a significance (p) value
for each possible pair of comparisons. Generally, the value of R ≥ 0.75 indicates well
separated communities, 0.75 > R ≥ 0.5 - overlapping but different communities, 0.5 > R ≥
0.25 - overlapping but somewhat different and R <0.25 indicates insufficiently different
communities (Clarke and Gorley 2001). ANOSIM was done using years pooled data for each
of three sampling sites at each artificial reef area.
12
Similarity percentages (SIMPER) were used to examine similarity within the groups (pooled
samples collected at three monitoring sites within each artificial reef) and to inspect that
species contributed to any observed differences among fish assemblages at different sites.
RESULTS
Descriptive results.
During our samples in 2011-2013 160 hours of underwater video, 80 hours for each artificial
reef was obtained. Altogether, 4360 fish 90 species of
A total 4360 fish from 90 species from 36 families were recorded during 160 hours of
BRUVS surveys at the 6 sampling sites at Rick Mills and Bottle Washer artificial reefs areas
in 2011–2013 (Appendix, Table 1).
1. All fish assemblages abundance and biodiversity.
Rick Mills area.
Univariate analyses.
Analysis of variances of mean fish abundance (mean MaxN) in one 60- minutes video
sample (2011-2013 pooled data) indicated that there were no statistically significant
differences among different sites (one-way ANOVA, df=2, F=0.427, P=0.624), Figure 2.
However, ANOVA of fish biodiversity (mean number of fish species in one 60-minutes video
sample) was significantly different (one-way ANOVA, df=2, F=9.796, P<0.001). Pair wise
comparison shows that site 3RM, located 520 m away from artificial reef (AR) has the
highest biodiversity, higher than site 1RM (50 m from AR) and site 2 RM (70 m from AR),
Figure 3.
13
Figure 2. Mean number of all recorded fish (MaxN) at different sampling sites
at Rick Mills artificial reef area. Error bars are standard deviation.
Figure 3. Mean number of all recorded fish species at different sampling sites
at Rick Mills artificial reef area. Asterisks indicate significance level: * - 0.05 –
0.01; ** - < 0.01 – 0.001; *** - <0.001
14
15
Multivariate analyses.
Analysis of Similarity (ANOSIM).
Table 2. Pair wise tests in Analysis of Similarity (ANOSIM) among fish
assemblages at 3 BRUVS sampling sites at Rick Mills artificial reef area,
pooled data of 2011-2013 surveys. Global R: 0.17, significance level 0.1%.
Groups
R-Statistic
Significance
Number
level %
Observed
1RM, 2RM
0.059
2.1
26
1RM, 3RM
0.302
0.1
0
2RM, 3RM
0.159
0.1
0
Global statistic value is low and indicate insufficient differences in fish assemblages
composition at statistically significant level. Differences in fish assemblages at sites in close
vicinity to AR are even lower, Table 2. Usually, R-values >0.75 interpreted as “well
separated assemblages”; R>0.5 as “overlapping, but clearly different” and R<0.25 as “barely
separable at all”, in accordance with the PRIMER-manual (Clarke & Gorley 2001). Only
differences between the most close to the AR 1RM site and the most distant 3RM fish
assemblages can be interpreted as “overlapping, but clearly different”; other to tests have
returned “barely separated “ reading, Table 2.
Similarity per cent analysis (SIMPER).
Average dissimilarity between fish assemblages from sampling sites 1RM and 2RM, 77.6%
indicates high differences in assemblages composition and structure. Average similarity
within the same assemblage were low, 30.5% and 18.9%, reflecting frequent changes in
species and fish numbers within each sampling site. Still, assemblage similarity at the site
1RM, closest to the artificial reef was higher, comparing to the more remote site, Table 3.
Mid water trevallies Fringefin Trevally, Pantolabus radiatus, Selaroides leptolepis, Caranx
sp., Fourline Striped Grunter, Terapon teraps, Shortfin Batfish, Zabidius novemaculeatus as
well as demersal Northwest Threadfin Bream, Pentapodus porosus and Ponyfishes
Leiognathus sp. were numerically dominant at both sampling sites and have contributed to
71.5% of total dissimilarity between compared assemblages, Table 3. Dissimilarity between
sample site 1RM, the closest to the AR and 3RM, the most remote one was high 78.2%,
indicating differences between assemblages, but only slightly higher than in previous
comparison, Table 4. Fish assemblages at both sites have comparable average similarity.
16
Similar list fish species dominated in assemblages and have contributed to 62.5% of total
dissimilarity between compared assemblages, Table 4.
17
Table 3. Comparison of fish assemblages at site 1RM (50 m from Rick Mills artificial reef) and site 3RM (70 m from the reef), pooled 2011-2013
BRUVS survey data. Cut off low contribution: 90%
Average dissimilarity between
compared assemblages: 77.6%
Species
Site1RM
Site 2RM
Average similarity:
Average similarity:
30.5%
18.9%
Average abundance, N
Average abundance,
Average dissimilarity, δ
Cumulative δ %
N
Pantolabus radiatus
8.03
7.14
16.63
21.44
Zabidius novemaculeatus
4.86
2.17
11.27
35.97
Selaroides leptolepis
3.41
4.90
9.10
47.69
Caranx sp.
2.79
2.59
8.97
59.26
Pentapodus porosus
0.76
1.90
3.56
63.85
Terapon theraps
0.41
1.59
3.25
68.05
Leiognathus sp.
0.62
1.07
2.69
71.51
Scomberomorus queenslandicus
0.62
1.00
2.23
74.39
Lutjanus erythropterus
0.76
0.45
2.09
77.08
Gnathanodon speciosus
0.38
0.69
1.68
79.24
Chaetodontoplus duboulayi
0.59
0.07
1.25
80.86
Upeneus tragula
0.55
0.03
1.25
82.47
Lutjanus russelli
0.48
0.00
0.99
83.75
Sillago sp.
0.31
0.14
0.82
84.81
Carangoides sp.
0.31
0.17
0.79
85.83
Diagramma labiosum
0.28
0.07
0.67
86.70
Lutjanus carponotatus
0.28
0.00
0.61
87.48
Flounder
0.17
0.21
0.60
88.26
18
Carcharhinus dussumieri
0.07
0.17
0.60
89.03
Echeneis naucrates
0.10
0.21
0.58
89.78
Sillago sihama
0.21
0.07
0.56
90.50
Average dissimilarity, δ is average Bray-Curtis dissimilarity between fish assemblages
Cumulative δ %is a cumulative contribution percentage. Species are listed in decreasing order of importance in contribution to δ.
19
Table 4. Comparison of fish assemblages at site 1RM (50 m from Rick Mills artificial reef) and the most remote site 3RM (520 m from
the reef), pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%
Average dissimilarity: 78.2%
Site1RM
Site 3RM
Average similarity:
Average similarity:
30.5%
33.2%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Pantolabus radiatus
8.03
6.33
12.9
16.49
Pentapodus porosus
0.76
6.26
9.5
28.64
Zabidius novemaculeatus
4.86
0.7
9.32
40.55
Selaroides leptolepis
3.41
3.19
7.16
49.7
Caranx sp.
2.79
0.63
5.53
56.77
Upeneus tragula
0.55
1.26
2.44
59.89
Leiognathus sp.
0.62
0.85
2.09
62.55
Lethrinus atkinsoni
0.1
1.07
1.93
65.02
0
1.04
1.88
67.42
0.76
0
1.43
69.25
0
0.78
1.33
70.94
Lutjanus carponotatus
0.26
0.59
1.29
72.59
Carcharhinus dussumieri
0.07
0.67
1.29
74.23
Choerodon cephalotes
0.07
0.7
1.25
75.83
Scomberomorus queenslandicus
0.62
0.59
1.22
77.39
0
0.56
1.05
78.73
Species
Gymnocranius elongatus
Lutjanus erythropterus
Paramonacanthus choirocephalus
Scolopsis sp.
20
Chaetodontoplus duboulayi
0.59
0.07
1
80.01
Terapon theraps
0.41
0.19
0.93
81.2
Lutjanus russelli
0.48
0
0.83
82.26
0
0.56
0.82
83.3
Carangoides sp.
0.31
0.3
0.8
84.33
Gnathanodon speciosus
0.38
0.15
0.77
85.32
Pelates quadrilineatus
0
0.63
0.7
86.22
Chelmon müelleri
0
0.44
0.67
87.07
Sillago sp.
0.31
0.11
0.62
87.86
Choerodon vitta
0.17
0.26
0.58
88.6
Lethrinus sp.
0.03
0.41
0.56
89.31
Sillago sihama
0.21
0.15
0.54
90.01
Siganus fuscescens
21
Bottom Washer area.
Univariate analyses.
Statistically significant differences were found in mean fish abundance (mean MaxN) among
sampling sites at Bottle Washer area (one-way ANOVA, df=2, F=5.598, P=0.006). There
were no statistically significant differences between close vicinity sites - 1BW (20 m from AR)
and 3BW (160 m from AR), however fish abundance at distant site 2BW (570 m from AR)
was statistically significantly lower, Figure 4.
No statistically significant differences were found among sampling sites in mean number of
fish species in one video sample (one-way ANOVA, df=2, F=2.095, P=0.131), Figure 5.
22
Figure 4. Mean number of all recorded fish (MaxN) at different sampling sites
at Bottle Washer artificial reef area.
Figure 5. Mean number of all recorded fish species at different sampling sites
at Bottle Washer artificial reef area.
23
Multivariate analyses.
Analysis of Similarity (ANOSIM).
Table 5. Pair wise tests in Analysis of Similarity (ANOSIM) among fish
assemblages at 3 BRUVS sampling sites at Bottle Washer artificial reef area,
pooled data of 2011-2013 surveys. Global R: 0.214, significance level 0.1%.
Groups
R-Statistic
Significance
Number
level %
Observed
1BW, 2BW
0.332
0.1
0
1BW, 3BW
0.168
0.1
0
2BW, 3BW
0.123
0.2
1
Global statistic value is low and can be interpreted as insufficient differences among fish
assemblages within the area. Pair wise tests indicated higher differences between closest to
the AR sampling site and most distant site fish assemblages, but only slightly above “barely
separated at all” level, Table 5.
Similarity per cent analysis (SIMPER).
Average dissimilarity between fish assemblages at the site near Bottle Washer artificial reef,
1BW and more remote site, 3BW was high, 78.5%. The list of species numerically
dominated and contributed to 64.7% of dissimilarity between sites was similar to the list of
dominant fish at site 1RM, the nearest to Rick Mills artificial reef; Table 4, 6.
Dissimilarity between fish assemblages notably increased in site 1BW and the most remote
from artificial reef 2BW sampling site, Table 8. Several mid-water species abundant at the
site 1BW (Shortfin Batfish, Golden Trevally, Gnathanodon speciosus, Caranx sp.) were not
recorded at 2BW site. Species with open sandy and muddy bottom preferences
(Yellowstripe Scad, Selaroides leptolepis, Ponyfish, Leiognathus sp.) and ubiquitous species
(Northwest Threadfin Bream, Pentapodus porosus, Fringefin Trevally, Pantolabus radiatus
and some other were abundant both at site 1BW near artificial reef and the most remote
2BW site, Table 8.
24
Table 6. Comparison of fish assemblages at site 1BW (20 m from Bottle Washer artificial reef) and the most remote site 3BW (160 m from
the reef), pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%.
Average dissimilarity: 78.5%
Site1BW
Site 3BW
Average similarity:
Average similarity:
27.2%
22.2%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Selaroides leptolepis
3.7
8.31
12.79
16.22
Zabidius novemaculeatus
5.78
0.65
9.51
28.28
Leiognathus sp.
5.35
5.25
9.24
39.99
Pentapodus porosus
1.91
4.77
7.3
49.26
Gnathanodon speciosus
2.7
0.23
4.98
55.57
Pantolabus radiatus
1.17
2.92
4.88
61.76
Caranx sp.
1.04
0.7
2.37
64.76
Nemipterus sp.
0
0.75
1.9
67.17
Nemipterus hexodon
0
1.04
1.84
69.5
Echeneis naucrates
0.96
0.08
1.63
71.57
Choerodon cephalotes
0.61
0.29
1.25
73.16
Scomberomorus queenslandicus
0.39
0.67
1.12
74.58
Seriolina nigrofasciata
0.26
0.4
1.04
75.9
Chaetodontoplus duboulayi
0.57
0
1.01
77.17
Lethrinus atkinsoni
0.26
0.38
0.96
78.4
Flounder
0.3
0.4
0.85
79.47
Choerodon schoenleinii
0.43
0.04
0.81
80.49
Species
25
Lutjanus vitta
0
0.42
0.74
81.43
Gymnocranius elongatus
0
0.44
0.71
82.33
Goby
0
0.38
0.69
83.21
Sillago sihama
0.3
0.19
0.69
84.08
Choerodon cyanodus
0.39
0.08
0.67
84.93
Choerodon vitta
0.43
0
0.66
85.77
Carangoides sp.
0.26
0.19
0.62
86.55
Carangoides hedlandensis
0.35
0.08
0.6
87.31
Sillago sp.
0.13
0.21
0.57
88.03
Nebrius ferrugineus
0.26
0.08
0.57
88.74
Neotrygon kuhlii
0.26
0
0.52
89.41
26
Table 7. Comparison of fish assemblages at site 1BW (20 m from Bottle Washer artificial reef) and the most remote site 2BW (570 m from
the reef), pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%.
Average dissimilarity: 78.8%
Site1BW
Site 2BW
Average similarity:
Average similarity:
27.2%
28.3%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Leiognathus sp.
5.35
4.24
12.46
14.53
Zabidius novemaculeatus
5.78
0
11.77
28.26
Selaroides leptolepis
3.7
2.2
9.5
39.34
Pentapodus porosus
1.91
2.58
6.31
46.71
Gnathanodon speciosus
2.7
0
5.78
53.44
Pantolabus radiatus
1.17
2.21
4.94
59.2
Caranx sp.
1.04
0
2.25
61.83
Echeneis naucrates
0.96
0.04
1.96
64.12
Carcharhinus dussumieri
0.09
0.83
1.8
66.22
Flounder
0.3
0.63
1.64
68.12
Nemipterus hexodon
0
0.67
1.61
70
Nemipterus sp.
0
0.71
1.49
71.74
Sillago sp.
0.13
0.6
1.41
73.39
Choerodon cephalotes
0.61
0.04
1.32
74.92
Scomberomorus queenslandicus
0.39
0.63
1.3
76.44
Chaetodontoplus duboulayi
0.57
0
1.24
77.89
0
0.58
1.15
79.23
Species
Parapercis sp.
27
Nemipterus nematopus
0.17
0.33
1.06
80.47
Choerodon schoenleinii
0.43
0
0.95
81.58
Seriolina nigrofasciata
0.26
0.05
0.81
82.53
Choerodon vitta
0.43
0
0.79
83.45
Carangoides hedlandensis
0.35
0.08
0.71
84.27
Choerodon cyanodus
0.39
0
0.68
85.07
Neotrygon kuhlii
0.26
0
0.65
85.83
Lutjanus fulvus
0.39
0
0.6
86.54
Goby
0
0.25
0.6
87.24
Lagocephalus sceleratus
0
0.34
0.59
87.93
0.3
0
0.58
88.61
Sillago sihama
28
2. Species targeted by anglers and divers abundance and biodiversity.
Rick Mills area.
Univariate analyses.
No statistically significant differences were found between different sampling sites at Rick
Mills area in abundance of fish targeted by anglers and skindivers (see Table 2), (one-way
ANOVA, df=2, F=2.819, P=0.066), Figure 6.
Analysis of variances also found no significant differences among sampling sites in
biodiversity of fish targeted by anglers and skindivers (one-way ANOVA, df=2, F=2.591,
P=0.081), Figure 7.
29
Figure 6. Mean number (MaxN) of sharks and fish targeted by anglers and
skindivers at different sites at Rick Mills artificial reef area.
Figure 7. Mean number of species of sharks and species of fish targeted by
anglers and skindivers at different sites at Rick Mills artificial reef area.
30
Multivariate analysis.
Analysis of Similarity (ANOSIM).
Table 8. Pair wise tests in Analysis of Similarity (ANOSIM) among assemblages
of targeted fishes at 3 BRUVS sampling sites at Rick Mills artificial reef area,
pooled data of 2011-2013 surveys. Global R: 0.237, significance level 0.1%.
Groups
R-Statistic
Significance level
Number Observed
%
1RM, 2RM
0.046
5.1 Not significant
56
1RM, 3RM
0.431
0.1
0
2RM, 3RM
0.253
0.1
0
Global statistic R in ANOSIM of communities of targeted species at 3 sites at Rick Mills point
to insufficient differences among fish communities; differences between nearest to the AR
sites is not only small, but statistically not significant. However, R in pair wise test between
fish assemblages at nearest to AR and the most remote sites indicate more separate
assemblages, Table 8.
Similarity per cent analysis (SIMPER).
Assemblages of species targeted by anglers and skindivers at sites at relative proximity to
artificial reef, 1RM and 2RM were similar both in sets of species and in their abundance.
Only two species-Stripey Snapper, Lutjanus carponotatus and Moses’ snapper, L. russelli
were absent at 2BW site. Stripey Snapper is typical reef and coral reef fish with strong site
fidelity, therefore it absence at open bottom habitat at the distance from the reef is not
unusual, Table 9.
31
Table 9. Comparison of fish assemblages targeted by anglers and skindivers at site 1RM (50 m from Rick Mills artificial reef) and site 2RM (70 m
from the reef), pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%.
Average dissimilarity: 79.0%
Site1RM
Site 2RM
Average similarity:
Average similarity:
26.4%
18.2%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Zabidius novemaculeatus
4.58
2.33
24.12
30.52
Caranx sp.
2.68
2.78
19.34
54.99
Scomberomorus queenslandicus
0.65
1.07
7.52
64.51
Lutjanus erythropterus
0.71
0.48
5.37
71.31
Gnathanodon speciosus
0.35
0.74
3.95
76.3
Choerodon schoenleinii
0.23
0.11
1.9
78.71
Carcharhinus dussumieri
0.06
0.19
1.83
81.03
Diagramma labiosum
0.26
0.07
1.69
83.17
Lutjanus russelli
0.45
0
1.66
85.27
Sphyraena jello
0.06
0.22
1.53
87.2
Epinephelus coioides
0.23
0.04
1.16
88.67
Lutjanus carponotatus
0.26
0
1.04
89.99
Choerodon vitta
0.16
0.04
1
91.26
Species
32
Table 10. Comparison of fish assemblages targeted by anglers and skindivers at site 1RM (50 m from Rick Mills artificial reef) and the most distant
site 3RM (520 m from the reef), pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%.
Average dissimilarity: 88.7%
Site1RM
Site 3RM
Average similarity:
Average similarity:
26.4%
27.0%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Zabidius novemaculeatus
4.58
0.73
23.61
26.61
Caranx sp.
2.68
0.65
14.11
42.52
Lethrinus atkinsoni
0.1
1.12
7.01
50.42
Carcharhinus dussumieri
0.06
0.69
5.01
56.07
Scomberomorus queenslandicus
0.65
0.62
4.98
61.68
Choerodon cephalotes
0.06
0.73
4.4
66.64
Lutjanus erythropterus
0.71
0
4.09
71.24
Lutjanus carponotatus
0.26
0.62
3.89
75.62
Gnathanodon speciosus
0.35
0.15
2.73
78.7
Lethrinus sp.
0.03
0.42
2.48
81.5
Choerodon vitta
0.16
0.27
1.99
83.74
Lutjanus russelli
0.45
0
1.7
85.65
Choerodon cyanodus
0.03
0.27
1.56
87.41
Diagramma labiosum
0.26
0
1.39
88.98
Choerodon schoenleinii
0.23
0
1.38
90.54
Species
33
The presence of reef-associated Shortfin Batfish, Zabidius novemaculeatus and Yellowtail
emperor, Lethrinus atkinsoni and Stripey Snapper at open bottom sandy area 520 m away
from artificial reef was least expected. The abundance of the later fish was even higher than
at the site near artificial reef, Table 10.
Bottle Washer area.
Univariate analyses.
The highest targeted fish mean abundance was recorded at site 1BW, nearest to AR,
differences highly significant (one-way ANOVA, df=2, F=36.361, P<0.001). Difference in this
statistic between site 2BW and 3BW, located more remotely from AR were not significant,
Figure 8.
Mean biodiversity was also significantly higher at nearest to AR site, 1BW; the lowest value
was recorded at site 2BW located 520 m away from AR (one-way ANOVA, df=2, F=8.148,
P<0.001), Figure 9.
34
Figure 8. Mean number (MaxN) of sharks and fish targeted by anglers and
skindivers at different sites at Bottle Washer artificial reef area.
Figure 9. Mean number of sharks species and fish species targeted by anglers
and skindivers at different sites at Bottle Washer artificial reef area.
35
Multivariate analysis.
Analysis of Similarity (ANOSIM).
Table 11. Pair wise tests in Analysis of Similarity (ANOSIM) among fish
targeted by anglers and skindivers at 3 BRUVS sampling sites at Bottle
Washer artificial reef area, pooled data of 2011-2013 surveys. Global R: 0.329,
significance level: 0.1%
Groups
R-Statistic
Significance
Number
level %
Observed
1BW, 2BW
0.488
0.1
0
1BW, 3BW
0.181
0.1
0
2BW, 3BW
0.287
0.1
0
The value of Global statistic R value is low, indicating low degree of separation. In pair wise
test the highest dissimilarity between fish assemblages was found in 1BW, the closet
sampling site to AR and 2BW, the most remote. The value of R was close to the level
“overlapping, but still clearly different”, Table 11.
Similarity per cent analysis (SIMPER).
As at sampling sites near Rick Mills artificial reefs, lists of species in assemblages at two
sites adjacent to Bottle Washer AR were similar, Table 12. However, some reef-associated
species – Batfish, wrasses, Blacktail Snapper, Lutjanus fulvus) and some
36
Table 12. Comparison of fish assemblages targeted by anglers and skindivers at site 1BW (20 m from Bottle Washer artificial reef) and more
remote site 3BW (160 m from the reef), pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%.
Average dissimilarity: 88.6%
Species
Site1BW
Site 3BW
Average similarity:
Average similarity:
22.6%
22.6%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Zabidius novemaculeatus
6.05
0.67
26.38
30.44
Gnathanodon speciosus
2.82
0.24
13.97
46.57
Caranx sp.
1.09
0.73
7.31
55.01
Scomberomorus queenslandicus
0.41
0.7
4.62
60.34
Choerodon cephalotes
0.64
0.3
3.73
64.65
Seriolina nigrofasciata
0.27
0.41
3.73
68.96
Lethrinus atkinsoni
0.27
0.39
3.26
72.72
Lutjanus vitta
0
0.43
2.79
75.95
Choerodon schoenleinii
0.45
0.04
2.45
78.77
Carcharhinus dussumieri
0.09
0.27
2.34
81.47
Choerodon cyanodus
0.41
0.09
2.11
83.9
Choerodon vitta
0.45
0
1.71
85.88
Sphyraena obtusata
0.09
0.17
1.44
87.54
Lutjanus fulvus
0.41
0
1.3
89.04
Carcharhinus tilstoni
0.09
0.04
1.05
90.25
37
Table 13. Comparison of fish assemblages targeted by anglers and skindivers at site 1BW (20 m from Bottle Washer artificial reef) and the most
remote site 2BW (570 m from the reef), pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%.
Average dissimilarity: 89.9%
Site1BW
Site 2BW
Average similarity:
Average similarity:
22.6%
22.6%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Zabidius novemaculeatus
6.05
0
28.75
31.97
Gnathanodon speciosus
2.82
0
14.51
48.1
Carcharhinus dussumieri
0.09
0.86
8.3
57.34
Scomberomorus queenslandicus
0.41
0.65
5.69
63.67
Caranx sp.
1.09
0
4.89
69.11
Choerodon cephalotes
0.64
0.04
3.11
72.56
Choerodon schoenleinii
0.45
0
2.8
75.68
Seriolina nigrofasciata
0.27
0.05
2.22
78.14
Carcharhinus tilstoni
0.09
0.13
2.16
80.54
0
0.17
1.91
82.67
Choerodon cyanodus
0.41
0
1.9
84.78
Choerodon vitta
0.45
0
1.9
86.89
Lutjanus fulvus
0.41
0
1.42
88.47
Sphyraena sp.
0.32
0
1.15
89.75
Lutjanus erythropterus
0.27
0
1.09
90.96
Species
Lutjanus vitta
38
species with wide distribution (Golden Trevally, Trevally Caranx sp.) were not recorded at
more remote site 3BW, Table 12. This difference between adjacent to artificial reef and more
remote sampling site in fish assemblages composition became even more clear in sites 1BW
and 2 BW comparison. While some ubiquitous fish abundance (School Mackerel, Australian
Blacktip Shark) have similar abundance at both sites, majority of fish recorded at 1BW, near
artificial reef both reef and ubiquitous species either have not been recorded at 2BW site,
570 m from AR or have very low abundance at this site. The only exception was White
Cheek Shark, species preferring sandy and muddy areas of the open bottom, whose
abundance was higher at 2BW when at 1 BW site, Table 13.
Reef-associated fish species abundance and biodiversity.
Rick Mills area.
Univariate analyses.
No statistically significant differences were found in mean abundance of reef-associated
fishes among sites at Rick Mills (one-way ANOVA, df=2, F=3.033, P=0.054), Figure 10.
Mean biodiversity in reef- associated fish species was substantially higher at site closest to
AR, 1RM, no differences found in more remote sites 2RM and 3RM comparisons (one –way
ANOVA, df=2, F=5.19, p=0.008), Figure 11.
39
Figure 10. Mean number (MaxN) of reef-associated fish recorded during
BRUVS survey at different sites at Rick Mills artificial reef area in2011-2013.
40
Figure 11. Mean number of reef-associated fish species recorded during
BRUVS survey at different sites at Rick Mills artificial reef area in 2011-2013.
41
Multivariate analysis.
Analysis of Similarity (ANOSIM).
Table 14. Pair wise tests in Analysis of Similarity (ANOSIM) among assemblages of reef-
associated fishes at 3 BRUVS sampling sites at Rick Mills artificial reef area,
pooled data of 2011-2013 surveys. Global R: 0.301, significance level 0.1%.
Groups
R-Statistic
Significance level
Number Observed
%
1RM, 2RM
0.138
0.7 Not significant
6
1RM, 3RM
0.467
0.1
0
2RM, 3RM
0.299
0.1
0
Global R value remained low, reflecting barely separate fish assemblages in 3 compared
sites, however in pair wise tests the highest dissimilarity was found between fish
assemblages from site closest to AR, 1RM and the most remote site, 3RM, Table 14.
Similarity per cent analysis (SIMPER).
The reef-associated fishes at 1RM and 2RM sites, located close to Rick Mills artificial reef in
general have similar abundance. The only exception was Stripy Snapper, the species did not
found at 2RM. The list of reef fishes was rather short, Table 15. Unpredictably, many reef
fishes were recorded at sampling site 3RM, 520 m away from artificial reef. Abundance of
Yellowtail Emperor, Stripey Snapper and Blue Tuskfish, Choerodon cyanodus was at 3RM
even higher than at 1RM, Table 16.
42
Table 15. Comparison of reef-associated fish assemblages at site 1RM (50 m from Rick Mills artificial reef) and site 2RM (70 m from the reef),
pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%.
Average dissimilarity: 84.4%
Site1RM
Site 2RM
Average similarity:
Average similarity:
27.4%
8.7%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Zabidius novemaculeatus
4.58
2.33
57.31
67.93
Choerodon schoenleinii
0.23
0.11
8.03
77.45
Diagramma labiosum
0.26
0.07
5.47
83.93
Lutjanus carponotatus
0.26
0
3.37
87.93
Choerodon sp.
0.06
0.11
3.06
91.56
Species
43
Table 16. Comparison of reef-associated fish assemblages at site 1RM (50 m from Rick Mills artificial reef) and the most distant site 3RM (520 m
from the reef), pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%.
Average dissimilarity: 84.4%
Site1RM
Site 3RM
Average similarity:
Average similarity:
27.4%
8.7%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Zabidius novemaculeatus
4.58
0.73
42.43
44.45
Lethrinus atkinsoni
0.1
1.12
20.07
65.47
Lutjanus carponotatus
0.26
0.62
8.58
74.46
Lethrinus sp.
0.03
0.42
5.99
80.73
Choerodon schoenleinii
0.23
0
4.38
85.32
Choerodon cyanodus
0.03
0.27
3.75
89.25
Diagramma labiosum
0.26
0
3.24
92.65
Species
44
Bottle Washer area.
Univariate analyses.
Reef fish abundance was several times higher at the site 1BW, nearest to AR, comparing to
more remote sites 2BW and 3BW, differences highly significant (one-way ANOVA, df=2,
F=21.647, P<0.001), Figure 12.
Reef fish biodiversity was higher at site 1BW, nearest to the AR comparing to the most
remote site, 2BW, difference highly significant, the most remote site, 2BW have the lowest
mean value of biodiversity (one-way ANOVA, df=2, F=11.491, P<0.001), Figure 13.
45
Figure 12. Mean number (MaxN) of reef-associated fish recorded during
BRUVS survey at different sampling sites at Bottle Washer artificial reef area in
2011-2013.
Figure 13. Mean number of reef-associated species of fish recorded during
BRUVS survey at different sampling sites at Bottle Washer artificial reef area in
2011-2013.
46
Multivariate analysis.
Analysis of Similarity (ANOSIM).
Table 17. Pair wise tests in Analysis of Similarity (ANOSIM) among
assemblages of reef-associated fishes at 3 BRUVS sampling sites at Bottle
Washer artificial reef area, pooled data of 2011-2013 surveys. Global R: 0.341,
significance level 0.1%.
Groups
R-Statistic
Significance
Number
level %
Observed
1BW, 2BW
0.486
0.1
0
1BW, 3BW
0.198
0.1
0
2BW, 3BW
0.302
0.1
0
ANOSIM of reef-associated fish assemblages indicated that the pattern in dissimilarity
between fish communities remained unchanged: the highest dissimilarity was found in the
closest to AR 1BW sampling site and the most remote, 2BW, Table 17.
47
Similarity per cent analysis (SIMPER).
Reef fishes group recorded at 1BW and 3BW, sites near Bottle Washer artificial reef was
similar, however abundance of some species (Shortfin Batfish, Blackspot Tuskfish,
Choerodon schoenleinii and Blue Tuskfish) was much higher at the site close to AR. Two
species - Yellowtail Emperor and unidentified Emperor recorded at 3BW, 160 m away from
the AR have not been found at 1BW, Table 18.
At the site 2BW, the most remote from Bottle Washer artificial reef 5 species recorded at
1BW were absent. However, unexpectedly, Brown sweetlip, Plectorhinchus gibbosus,
species normally associated with rocky reefs and Brownstripe Snapper, Lutjanus vitta,
occurring on open bottom areas surrounding reefs have been recorded at site 2BW, 570 m
away from artificial reef, Table 19.
48
Table 18. Comparison of reef-associated fish assemblages at site 1BW (20 m from Bottle Washer artificial reef) and more remote site 3BW (160 m
from the reef), pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%.
Average dissimilarity: 91.9%
Site1BW
Site 3BW
Average similarity:
Average similarity:
25.3%
17.8%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Zabidius novemaculeatus
6.05
0.67
47.91
52.13
Choerodon schoenleinii
0.45
0.04
11.38
64.5
Lethrinus atkinsoni
0.27
0.39
9.04
74.34
0
0.43
7.83
82.86
0.41
0.09
3.72
86.91
0
0.13
3.36
90.57
Species
Lutjanus vitta
Choerodon cyanodus
Lethrinus sp.
49
Table 19. Comparison of reef-associated fish assemblages at site 1BW (20 m from Bottle Washer artificial reef) and the most remote site 2BW (570
m from the reef), pooled 2011-2013 BRUVS survey data. Cut off low contribution: 90%.
Average dissimilarity: 100.0%
Site1BW
Site 2BW
Average similarity:
Average similarity:
25.3%
5.0%
Average abundance
Average abundance
Average dissimilarity, δ
Cumulative δ %
Zabidius novemaculeatus
6.05
0
52.8
52.8
Choerodon schoenleinii
0.45
0
20.25
73.05
Lutjanus vitta
0
0.17
6.57
79.61
Plectorhinchus gibbosus
0
0.13
3.67
83.28
Choerodon cyanodus
0.41
0
3.43
86.71
Carcharhinus melanopterus
0.09
0
2.59
89.3
Lutjanus fulvus
0.41
0
2.58
91.88
Species
50
DISCUSSION
All fish assemblages spatial distribution.
No differences in all fish abundance and biodiversity were found in comparisons of sampling
sites located close to Bottle Washer artificial reef and more remote sites. Similar results were
obtained during fish abundance comparisons at samples sites within Rick Mills area.
Surprisingly, overall fish biodiversity was considerably higher at the site located 520 m from
Rick Mills artificial reef, comparing to adjacent sites.
Fishes targeted by anglers and divers.
Both abundance and biodiversity of fish targeted by anglers and skindivers did not differed
significantly among all 3 sampling sites at Rick Mills artificial reef area. Distinctive differences
in these fish spatial distribution were found at Bottle Washer area: sampling site closest to
artificial reef culvert has statistically significantly higher abundance and biodiversity
comparing to the most remote site (570 m away from the reef).
Reef-associated fish species abundance and biodiversity.
Results of present study do support presumption of higher abundance and biodiversity of
reef-associated fishes at sampling sites located in close vicinity of Bottle Washer artificial
reef. Fish abundance was ten-fold higher at the site nearest to artificial reef comparing to the
most remote sampling site and threefold higher comparing to the site located 160 m away
from the reef. Biodiversity was also significantly higher at sites adjacent to artificial reef
comparing to the most remote site; the close the site was located to the reef the higher was
biodiversity.
No differences were found in abundance of reef-associated fish among sampling sites at
Rick Mills artificial reef area. Mean biodiversity was significantly higher at the sampling site
closest to artificial reef comparing to more remote site, but it did not differ significantly from
the most distant site, 520 m away from the reef.
Multivariate analyses of fish assemblages at different sampling sites.
ANOSIM (Analysis of Similarity) of all fish assemblages, assemblages when only of sharks
and fish targeted by anglers and skindivers were included and only reef-associated fish
groups in all cases have Global R values below 0.5, indicating only insufficient level of
differences between fish assemblages from different sites. Even when only reef-associated
species groups were compared, in no occasion they have been found to be clearly different.
First, this indirectly reflects the fact that both artificial reefs areas are likely to be inhabited by
51
a mixture of fishes with different habitat preferences. Second, it allows a suggestion about
some level of heterogeneity of bottom habitat outside of artificial reefs, that makes the habitat
suitable for fishes with different environmental requirements, including reef-associated
species.
Similarity percent analysis (SIMPER) examining each species contribution to assemblage
structure results clearly indicate that fish assemblages both in close vicinity to artificial reef
constructions and far away from the reef consist of ubiquitous species, that can live in a
variety of habitats, reef-associated species, and species inhabiting open bottom sandy and
muddy habitat, that dominates areas surrounding both artificial reefs.
Among reef-associated species, Shortfin Batfish was abundant at both artificial reef areas.
Noticeably, the fraction of reef-associated fish (Stripey Snapper, Lutjanus carponotatus,
Painted Sweetlips Diagramma labiosum, Scribbled Angelfish, Chaetodontoplus duboulayi)
was rather small even at sampling sites adjacent to both artificial. Ubiquitous species and
species that prefer open sandy and muddy bottom dominated at both Rick Mills and Bottom
Washer artificial reefs.
The most “discrepancies” in fish distribution were observed at Rick Mills artificial reef.
Unexpectedly, abundance of juvenile Crimson Snapper, Lutjanus erythropterus, fish that
prefer muddy bottom habitat was higher at close vicinity to the reef while at the most remote
sites this species has not been recorded at all. Stripey Snapper, Lutjanus carponotatus,
typical rocky and coral reef species has twice higher abundance at the site away from
artificial reef. Ubiquitous fish Moses' Snapper, Lutjanus russelli was among common species
at the site closest to the reef. However, the fraction of sand and mud bottom associated
fishes (Bartail Goatfish, Upeneus tragula, Swallowtail Seabream, Gymnocranius elongatus,
Pigface Leatherjacket, Paramonacanthus choirocephalus, White Cheek Shark, Carcharhinus
dussumieri, Fourline Striped Grunter, Pelates quadrilineatus was higher at the site, the most
remote from Rick Mills artificial reef.
We suggest that the key factor contributing to these “disagreements” in fish
distribution within artificial reefs areas and Rick Mills AR in particularly is presence of
infrequent rocks, boulders and aggregations of coral rubble in generally homogenous sandy
and muddy flat bottom. These portions of hard substrate provide suitable habitat for sessile
invertebrates (hydroids, occasional soft corals) and macro algae. In several occasions such
small “pseudo-reefs” images surrounded by areas of open sandy or muddy bottom were
recorded during BRUVS survey at both reefs. The importance of complex habitats that
serves as refuge from predators is long known (Heck & Wetstone 1977; Orth et al. 1984;
Rozas & Odum 1987; Nelson W.G. and Bonsdorff 1990). Therefore these “pseudo-reef”
attracting reef-associated fish; that makes fish distribution at Rick Mills artificial reef more
52
complex rather than a simplistic assumption of “fish are concentrated on artificial reef
construction and around it”.
CONCLUSION.
We suggest that the “artificial reef effect” is evident at Bottle Washer artificial reef.
Assemblages of sharks and of fishes targeted by amateur anglers and skindivers as well as
reef-associated fishes were more abundant and contained more species at sites adjacent to
the reef than at sites located away from the reef. However, when all fish fauna components
were included in analysis no differences in fish abundance and biodiversity have been found
in comparisons of sampling sites located close to Bottle Washer artificial reef and more
remote sites.
“Artificial reef effect” was far less evident at Rick Mills artificial reef. No differences in fish
abundance were found between sites adjacent to the reef when all fish fauna has been
compared. Surprisingly, overall biodiversity was considerably higher at the site located 520 m
away from Rick Mills. Both mean fish abundance and biodiversity of sharks and fish targeted
by anglers and skindivers did not differ significantly among sites close to artificial reef and
more distant site. As for reef-associated fish species the results were equivocal: mean
biodiversity was significantly higher at the site closest to the reef comparing to second site
near the reef. However, no differences have been found in site closest to the reef and the
most distant site (520 m away from the reef) comparisons. No differences were found in
mean reef-associated fish abundance for all compared sites.
There are several possible explanations for our results:

Specific of fish fauna
Fish fauna in both artificial reefs areas consists of species associated with open sandy and
muddy bottom (52.2%), ubiquitous species (occurring in a wide variety of habitats, from coral
reefs to muddy open bottom represent 30% of all fish and a fraction of reef-associated fish is
17.8%, Appendix, Table 1. Open bottom and ubiquitous species found suitable habitat on
artificial reef and in close vicinity of the reef, therefore they dominate fish assemblages.

Relatively short period of both artificial reef existence.
It was just 3 years since 2011 when both artificial reefs were substantially upgraded. Reefassociated fish fauna just started to colonise both reefs.

Relatively large distances of sampling sites from AR
53
In our study we intentionally avoided to employ BRUVS devices close than 20 metres from
the artificial reef construction to avoid possible snagging and interactions with anglers
utilising the reef. It was demonstrated in a recent study, fish association with the artificial reef
is on a localised scale (< 30 m) (Scott et al. in press). Anglers are well aware that the catches
can drop substantially if the position of the reef or rock was identified incorrectly.
Still, Rick Mills and Bottle Washer artificial areas have twice higher fish biodiversity and
almost three times higher overall fish abundance comparing to monitoring sites in Darwin
Harbour entrance and area approximately 1 kilometre from south-west edge of Channel
Island (Gomelyuk 2014). Further studies and monitoring will be required in a future to assess
the success of these artificial reefs implementation.
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APPENDIX
Table 1. List of fishes recorded during 160 hours of BRUVS surveys of Rick
Mills and Bottle Washer artificial reefs in 2011-2013
Fish ecological
FAMILY
SPECIES
Rick Mills
Bottle Washer
group*
+
RF
+
RF
+
RF
HEMISCYLLIDAE
Chiloscyllium punctatum
GINGLYMOSTOMATIDAE
Nebrius ferrugineus
+
CARCHARHINIDAE
Carcharhinus melanopterus
Carcharhinus sorrah
+
RF
Carcharhinus dussumieri
+
+
OB
Carcharhinus tilstoni
+
+
OB
Galeocerdo cuvier
+
UB
Negaprion acutidens
+
UB
SPHYRNIDAE
Sphyrna mocorran
+
+
UB
+
OB
+
RF
RHINOBATIDAE
Rhynchobatus djiddensis
DASYATIDAE
Neotrygon kuhlii
+
Himantura undulata
+
OB
56
Himantura uarnak
+
OB
Himantura jenkinsii
+
OB
Himantura sp.
Dasyatis sp.
+
+
OB
+
OB
MYLIOBATIDAE
Aetobatus narinari
+
OB
MURAENIDAE
Gymnothorax longinquus
+
+
RF
+
RF
Synodus sp.
+
OB
Platycephalus endrachtensis
+
OB
Gymnothorax sp.
SYNODONTIDAE
SERRANIDAE
Epinephelus coioides
+
+
UB
Epinephelus lanceolatus
+
+
RF
+
RF
CENTROPOMIDAE
Psammoperca waigiensis
SILLAGINIDAE
Sillago sihama
+
+
OB
Sillago sp.
+
+
OB
TERAPONTIDAE
Terapon theraps
+
OB
Pelates quadrilineatus
+
OB
APOGONIDAE
Sphaeramia orbicularis
+
+
OB
Pantolabus radiatus
+
+
UB
Selaroides leptolepis
+
+
OB
Carangoides hedlandensis
+
+
OB
Carangoides caeruleopinnatus
+
+
UB
Caranx sp.
+
+
UB
Gnathanodon speciosus
+
+
UB
CARANGIDAE
Scomberoides commersonnianus
+
UB
+
+
OB
+
+
OB
+
+
UB
Lutjanus erythropterus
+
+
OB
Lutjanus carponotatus
+
+
RF
Lutjanus vitta
+
+
RF
Lutjanus russelli
+
+
UB
+
RF
Seriolina nigrofasciata
LEIOGNATHIDAE
Leiognathus sp.*
ECHENEIDAE
Echeneis naucrates
LUTJANIDAE
Lutjanus fulvus
57
Lutjanus gibbus
+
Lutjanus johnii
+
RF
+
OB
+
RF
HAEMULIDAE
Plectorhinchus gibbosus
Diagramma labiosum
+
+
RF
Pomadasys maculatus
+
+
OB
Pomadasys kaakan
+
OB
LETHRINIDAE
Gymnocranius elongatus
+
+
OB
Lethrinus atkinsoni
+
+
RF
Lethrinus sp.
+
+
RF
+
OB
NEMIPTERIDAE
Nemipterus hexodon
Nemipterus nematopus
+
+
OB
Nemipterus sp.
+
+
OB
Pentapodus porosus
+
+
UB
Scolopsis sp.
+
OB
MULLIDAE
Upeneus tragula
+
+
OB
Pupeneus heptacanthus
+
+
OB
SCIAENIDAE
Protonibea diacanthus
+
OB
EPHIPPIDAE
Zabidius novemaculeatus
+
Platax orbicularis
+
RF
+
RF
CHAETODONTIDAE
Chaetodon aureofasciatus
+
+
RF
Chelmon müelleri
+
+
OB
+
RF
+
+
RF
+
+
UB
Sphyraena obtusata
+
UB
Sphyraena sp.
+
UB
Chelmon marginalis
POMACANTHIDAE
Chaetodontoplus duboulayi
SPHYRAENIDAE
Sphyraena jello
LABRIDAE
Choerodon cyanodus
+
+
RF
Choerodon cephalotes
+
+
RF
Choerodon schoenleinii
+
+
RF
Choerodon vitta
+
+
OB
Choerodon sp.
+
RF
PINGUIPEDIDAE
Parapercis sp.
+
OB
BLENNIDAE
58
Meiacanthus luteus
+
+
RF
+
+
OB
+
+
OB
+
+
UB
+
+
OB
Paramonacanthus choirocephalus
+
+
OB
Monacanthus chinensis
+
+
OB
Pseudomonacanthus elongatus
+
GOBIIDAE
Goby, unidentified
SIGANIDAE
Siganus fuscescens
SCOMBRIDAE
Scomberomorus queenslandicus
BOTHIDAE
Flounder, unidentified
MONOCANTHIDAE
OB
Anacanthus barbatus
+
Paramonacanthus filicauda
+
TETRAODONTIDAE
OB
OB
Lagocephalus sceleratus
+
+
OB
Lagocephalus lunaris
+
+
OB
Feroxodon multistriatus
+
+
OB
Arothron manilensis
+
OB
* RF – reef-associated fish; OB – open bottom preference; UB – ubiquitous fish (with very broad distribution)
59