Quantitative diet assessment of wobbegong sharks (genus Orectolobus) in New South Wales, Australia
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1272
Quantitative diet assessment of wobbegong sharks
(genus Orectolobus) in New South Wales, Australia
Charlie Huveneers, Nicholas M. Otway, Susan E. Gibbs, and Robert G. Harcourt
Huveneers, C., Otway, N. M., Gibbs, S. E., and Harcourt, R. G. 2007. Quantitative diet assessment of wobbegong sharks (genus Orectolobus) in
New South Wales, Australia. – ICES Journal of Marine Science, 64: 1272– 1281.
The diets of three species of wobbegong (Orectolobus ornatus, O. maculatus, and O. halei) in New South Wales, Australia, were inves-
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tigated using stomach contents from specimens caught by commercial fishers. Some 80% of wobbegongs caught by commercial setline,
and 60% caught by trap or scuba diving, had empty stomachs, most likely due to regurgitation. Wobbegongs were frequently hooked in
the stomach (80–90% of the catch), potentially contributing to the greater proportion of empty stomachs compared with other species
of shark. The diet of all three species was primarily osteichthyans, but with some cephalopods and chondrichthyans. Interspecific differ-
ences in the diets were related to total length of the shark. Octopuses were more frequent in the diet of O. ornatus (dwarf ornate
wobbegong) than other wobbegong species, possibly through the smaller adult size facilitating capture of octopuses in small holes/
crevices. Orectolobus halei fed more frequently on pelagic species and chondrichthyans, possibly because of their greater mobility.
Wobbegongs feed at a high trophic level, and their removal from their ecosystem may impact lower trophic levels.
Keywords: commercial fishery, diet, New South Wales, Orectolobus, wobbegongs.
Received 30 October 2006; accepted 7 June 2007; advance access publication 21 July 2007.
C. Huveneers, S. E. Gibbs, and R. G. Harcourt: Marine Mammal Research Group, Graduate School of the Environment, Macquarie University,
Sydney, NSW 2109, Australia. N. M. Otway: NSW Department of Primary Industries, Port Stephens Fisheries Centre, Taylors Beach Road,
Taylors Beach, NSW 2316, Australia. Correspondence to C. Huveneers: tel: þ61 2 9850 7980; fax: þ61 2 9850 7972; e-mail: charlie.huveneers@
gse.mq.edu.au
Introduction role of wobbegongs in marine ecosystems will enhance fishery
Sharks are among the top predators in the marine environment management.
(Cortés, 1999) and have an important role in energy exchange Wobbegongs are demersal sharks that are usually seen resting
between trophic levels (TLs) (Cortés and Gruber, 1990; on the substratum (Whitley, 1940; Stead, 1963; Munro, 1967;
Wetherbee et al., 1990). As such, any removal of top predators Coleman, 1980; Last and Stevens, 1994; Compagno, 2001).
from coastal ecosystems has the potential to cause trophic cascades However, they have also been observed ambushing or actively
that may result in alterations to the abundance of lower trophic chasing prey (Whitley, 1940; Last and Stevens, 1994; Compagno,
species (Jennings and Kaiser, 1998; Myers et al., 2007). However, 2001). At present, it is unclear whether feeding follows a diel
there is an absence of quantitative information on the diet of pattern (Huveneers et al., 2006). Although descriptive studies
sharks in many ecosystems, making assessment of how they con- with limited sample sizes suggest that wobbegongs feed on a
tribute to marine trophic structure difficult (Cortés, 1999). variety of prey (Cochrane, 1992; Chidlow, 2003), a quantitative
Wobbegong sharks are abundant predators, commonly found assessment of their diet will provide a critical first step in under-
at coastal rocky reefs off New South Wales (NSW), Australia standing trophic interactions and possible ecosystem effects of
(Last and Stevens 1994; Compagno, 2001). They are commercially the wobbegong fishery.
targeted in NSW waters by fishers within the Ocean Trap and Line Here, we investigated the diets of the three wobbegong species
Fishery, and are sold as boneless fillets or “flake”. The commercial (Orectolobus ornatus, O. maculatus, and O. halei) occurring in
catch has declined from ca. 150 t in 1990/1991 to ca. 70 t in 1999/ coastal waters off NSW using stomach contents collected from
2000, a decrease of more than 50% in a decade (Pease and animals caught commercially or as bycatch, or collected by
Grinberg, 1995; NSW DPI, unpublished data). The extent to hand. Diet components were examined and the relative impor-
which this decline can be attributed to fishing is unclear, and tance of each prey item was quantified. Interspecies variation,
whether the trend is consistent across species is unknown, prey diversity, and dietary overlap were also investigated to
raising concern for the status of wobbegong shark populations assess resource partitioning between the three species.
in the region. As a result, spotted and ornate wobbegongs are
classified by the IUCN as “Vulnerable” in NSW (Cavanagh et al., Material and methods
2003). Quantification of wobbegong diet is critical to understand- Collection of specimens and stomach processing
ing the potential effects of their removal (via a commercial fishery) Wobbegongs were obtained using setlines, lobster traps, and by
on the coastal marine ecosystem. Improved understanding of the scuba diving between June 2003 and May 2006. Most stomachs
# 2007 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved.
For Permissions, please email: journals.permissions@oxfordjournals.orgQuantitative diet assessment of wobbegongs in New South Wales 1273
were collected aboard commercial fishing vessels in the Ocean other three indices, was also calculated, and expressed as a percen-
Trap and Line Fishery targeting wobbegongs with demersal tage (%IRI; Cortés, 1997). A three-dimensional graphic represen-
setlines at four locations in NSW (Nambucca Heads, Port tation, where each point on the graph represents the numerical
Stephens, Newcastle, and Sydney) (Figure 1). All three species importance, percentage importance by mass, and percentage
were collected throughout the year and at all locations (except occurrence, was also used as an alternative to summary tables
in Sydney, where O. ornatus is not found). Sample size was sup- (Costello, 1990; Cortés, 1997). Only prey families with at least
plemented by wobbegongs taken as bycatch in lobster traps, and one of the quantifying parameters .10% were represented in
collected while scuba diving. Once captured, wobbegongs were the graph to avoid a cluster of minor prey items close to the
identified to species, the sex was determined, and total length origin of the axis.
was measured to the nearest millimetre. The position of the All quantitative analyses were undertaken using %IRI at a
embedded hook (i.e. in the mouth, oesophagus, or cardiac family level, and excluding data for contents that were not identi-
stomach) was recorded for each wobbegong caught by the fiable to family level (Simpfendorfer et al., 2001). To determine
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setline fishery before excising the stomach. Wobbegong foreguts whether the sample size was sufficient accurately to describe the
(anterior of oesophagus to pyloric sphincter) were removed, diet of wobbegongs, the cumulative number of prey species was
placed in labelled bags, and stored at 2208C for later analysis in plotted against the number of stomachs examined. The order in
the laboratory. which stomachs were analysed was randomized ten times (Ferry
In the laboratory, stomach contents were thawed and washed et al., 1997). Cumulative curves were considered asymptotic if at
with water. Identification was based on intact and remaining least ten previous values of the total number of prey were in the
hard items, including cephalopod beaks, fish otoliths, and internal range of the asymptotic number of prey + 0.5. The number of
and external skeletal material, combined with general shape and stomachs at which the number of prey items reached an asympto-
anatomical features of the prey. Recognizable prey items were tic value identified the minimum sample size required to describe
identified to the lowest taxon possible, using reference collections the diet adequately (Cailliet et al., 1986; Cortés, 1997).
of fish otoliths (78 Australian species) and cephalopod beaks (20 Low sample size resulting from the large proportion of empty
species) held at the South Australian Museum, and reference stomachs prevented investigation of ontogenetic and sexual
guides (Smale et al., 1995; Lu and Ickeringill, 2002). Contents variation in the diet of the wobbegong species. Dietary overlap
identified as bait via prominent hook marks and/or knife cuts between species was calculated using Horn’s (1966) index of
were excluded from the analysis. The number of empty stomachs overlap (R0). Values of 0 –0.29, 0.3– 0.59, or .0.6 indicate low,
together with the number of stomachs containing only bait was medium, or high overlap, respectively (Langton, 1982). Diet diver-
recorded and expressed as a percentage of the total number exam- sity (breadth) of each species was also calculated using the com-
ined. Prey items were assigned to a prey category (demersal, bined index (CI; Cortés et al., 1996), calculated by taking the
predominantly demersal, or pelagic) according to Stevens and average of the Levin’s index (B) and the Shannon –Weiner index
Wiley (1986), using standard taxonomic literature and Kuiter (H0 ) standardized on a scale of 0 –1 (Krebs, 1999). Similarity
(2000). The wet mass of each food item was determined on an among species was also examined with cluster analysis in Primer
electronic balance to the nearest 0.01 g when prey items were v5.2.9 (Clarke and Gorely, 2001), using the techniques described
small and on a spring balance (600 + 5 g or 2.5 + 0.02 kg) when in Clarke and Warwick (2001). Analysis of diet differences
prey was large. between species was undertaken following Platell and Potter
(2001), and White et al. (2004). Diet data within each species
Analysis were randomly allocated into groups of four or five, and mean
The contributions of different prey items to each species’ diet were values were determined. Mean IRI values were then square-root
determined by the numerical importance (%N; Hyslop, 1980), transformed and a similarity matrix produced, using the Bray –
frequency of occurrence (%F; Hynes, 1950; Hyslop, 1980), and Curtis similarity coefficient. An MDS ordination plot was
mass (%M; Pillay, 1952; Hyslop, 1980). The index of relative obtained from the resulting similarity matrix. One-way analyses
importance (IRI; Pinkas et al., 1971), which incorporates the of similarities (ANOSIM) were used to test for significant
Figure 1. Sampling locations for collection of wobbegongs in New South Wales.1274 C. Huveneers et al.
Table 1. Summary table of wobbegongs sampled, hook position, and numbers of prey items.
Parameter Category Orectolobus ornatus Orectolobus maculatus Orectolobus halei Total
Number dissected – 285 155 201 641
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
Stomachs with prey item – 64 39 41 144
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
Prey items – 97 65 151 313
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
Empty stomachs (%) Line 82.8 75.6 79.8 –
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
Trap/diving 64.6 49.5 66.7 –
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
Hooking location (%) Stomach 82.7 70.2 67.9 –
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
Mouth 12.2 20.2 22.6 –
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . .
Oesophagus 5.1 9.6 9.5 –
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Number dissected, the numbers of wobbegongs dissected; Stomachs with prey item, the numbers of stomachs with at least one prey item; Prey items, the
numbers of prey items found in stomachs; Empty stomachs, the proportion of stomachs that were empty or only contained bait; Hooking location, the
frequency of hooking location.
differences among the diets of the three species. Similarity percen- Results
tages (SIMPER) were used to determine the dietary categories that A total of 641 wobbegongs (285 O. ornatus, 155 O. maculatus, and
typified particular species and/or contributed most to the dissim- 201 O. halei) was examined for diet (Table 1). Wobbegongs
ilarities between species (Clarke, 1993). Multivariate dispersion with empty stomachs or bait only were common (ca. 80% in wob-
(MVDISP) was used to determine the degree of dispersion of begongs caught on setlines). Wobbegongs caught in traps or while
the diet samples on ordination plots (Somerfield and Clarke, scuba diving had a lesser proportion of empty stomachs (ca. 60%).
1997). Results obtained from the multivariate analyses were Wobbegongs were mainly hooked in the cardiac stomach (75%).
compared with the dietary overlap and breadth indices. In a few cases (n ¼ 23), the hook had perforated the stomach
Finally, the TL for each species of wobbegong was calculated wall and damaged the liver or vertebral column. In all, 313 prey
following Cortés (1999): items were found in 144 stomachs, and ca. 50% of these contained
! a single prey item only.
X
3
TL ¼ 1 þ Pj TLj ;
j¼1 Cumulative diversity and quantitative description
of wobbegong diets
where Pj is the proportion of prey category j, TLj the TL of each The cumulative curve for wobbegongs (species combined) reached
prey category j, and j the number of prey categories (3), i.e. an asymptote after 130 stomachs had been examined
Osteichthyes, Cephalopoda, and Chondrichthyes. (Figure 2a). Although the cumulative curves for each species
Figure 2. Randomized cumulative prey curve of (a) wobbegongs (species combined), (b) Orectolobus ornatus, (c) O. maculatus, and
(d) O. halei; error bars represent standard deviations.Quantitative diet assessment of wobbegongs in New South Wales 1275
described a general asymptotic relationship, they did not reach chondrichthyans and cephalopods were consumed by O. halei in
asymptotic stabilization (Figure 2b –d), suggesting that the small numbers, but made up a large proportion of the total
stomachs sampled may not be entirely representative of each mass of the stomach contents. In contrast to the situation for O.
species’ diet. maculatus, chondrichthyans (three families) were the second
Other items in the stomachs of wobbegongs included stones in most dominant prey group in the diet of O. halei on the basis of
single specimens of O. maculatus and O. halei, and in two %N, %M, %F, and %IRI, followed by cephalopods (Octopus
O. ornatus, algal fragments in 14 O. ornatus, 3 O. maculatus, and spp.). Within the bony fish category and when quantified by
3 O. halei; and molluscan shells in single specimens of O. mass, carangids were the most important prey group, followed
ornatus and O. halei. These items may have represented incidental by sciaenids, labrids, and kyphosids. Trachurus novaezelandiae
ingestion or the stomach contents of prey, and were not included and S. australasicus were important numerical contributors to
in the overall analysis. the diet of O. halei, but only made up a small proportion of the
total mass of prey items examined. A few Achoerodus viridis,
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Orectolobus ornatus Argyrosomus japonicus, and unidentified kyphosids were found,
Bony fish (ten families) were the dominant food of O. ornatus in but they constituted a large proportion of the stomach contents
terms of %N, %M, %F, and %IRI, followed by cephalopods by mass. Other bony fish found as prey and ranked in accordance
(two families) (Table 2, Figure 3a). The rankings of prey items with the IRI included species from the families Clupeidae,
in the bony fish category differed according to the method of Berycidae, Sparidae, Arripidae, Uranoscopidae, and
quantification. The IRI indicated that unidentified bony fish Diodontidae. Of chondrichthyans, Heterodontus portusjacksoni,
were most prominent, followed by sparids, with Pagrus auratus O. ornatus, and species of the family Rhinobatidae were found
(snapper) particularly important. When quantified by mass, in the stomachs. Although the diet of O. halei had a broader diver-
Gymnothorax prasinus (green moray) was the most prominent sity of pelagic prey than O. ornatus and O. maculatus, the prey
prey item, followed by P. auratus (snapper), Girella tricuspidata composition of O. halei was similar to that of the other two orec-
(blackfish), and unidentified bony fish. Within the bony fish, G. tolobids, and was mostly demersal.
prasinus, P. auratus, and G. tricuspidata contributed to a large pro-
portion of the total mass of the stomach contents sampled, Species comparison
whereas unidentified items contributed more to abundance than Diet breadth of O. maculatus and O. ornatus was similar and rela-
to mass. Other bony fish found as prey and ranked in accordance tively low (ca. 0.3), and that of O. halei was even smaller (0.18).
with the IRI included species from the families Batrachoididae, Overall, the diets of the three species differed significantly
Carangidae, Platycephalidae, Monacanthidae, Mugilidae, (ANOSIM: R-statistic ¼ 0.184, p , 0.01). The diets of O. ornatus
Pempheridae, and Berycidae. Octopuses dominated the cephalo- and O. halei overlapped only slightly (0.29 Horn’s index) and
pod category, contributing more numerically than by mass to were significantly different (ANOSIM: R-statistic ¼ 0.336, p ,
the diet, and were followed by cuttlefish. Most prey taxa were 0.01). However, neither the diets of O. ornatus and O. maculatus
demersal, only the Carangidae being pelagic. nor those of O. maculatus and O. halei differed significantly
(ANOSIM: R-statistics ¼ 0.077 and 0.01, respectively, and p .
Orectolobus maculatus 0.05 in both cases). These relationships were supported by
Bony fish (14 families) also dominated the food of O. maculatus in Horn’s index, suggesting strong overlap of the diets of
terms of %N, %M, %F, and %IRI, and were followed by cephalo- O. ornatus and O. maculatus (0.87), and a medium overlap of the
pods (various species of octopus), then chondrichthyans (Table 2, diets of O. maculatus and O. halei (0.46). Octopuses accounted
Figure 3b). The rankings of prey items in the bony fish category for most of the difference between diet compositions of the
also differed by method of quantification. The IRI indicated that three species of wobbegong, with carangids and sparids also con-
unidentified bony fish dominated, followed by P. auratus tributing (SIMPER). Samples from all three species were largely
(snapper) and Scomber australasicus (slimy mackerel). When scattered, with dispersion values of 0.87, 1.07, and 1.29 for
quantified by mass, sparids were the most prominent prey, fol- O. ornatus, O. maculatus, and O. halei, respectively. The MDS
lowed by unidentified bony fish, Muraenesox bagio (pike eel), plot had a high stress level, indicating a poor fit between actual dis-
and kyphosids. Unidentified items contributed more numerically tance measures and distance in the ordination, so the plot was dif-
than by mass to the diet, whereas P. auratus, M. bagio, and ficult to interpret and did not show any major trends.
Scorpis spp. all contributed more gravimetrically than numerically.
Other bony fish found as prey of O. maculatus and ranked in TL of wobbegong sharks
accordance with the IRI included species from the families All three species of wobbegong fed on secondary consumers, at
Carangidae, Sciaenidae, Berycidae, Dinolestidae, Moridae, TL . 3. Trophic levels of prey categories were 3.2, 3.24, and 3.65
Labridae, Serranidae, Mugilidae, Monacanthidae, and Diodonti- for cephalopods, osteichthyans, and chondrichthyans, respectively.
dae. Within the chondrichthyan group, prey items from the The trophic levels of the three species were 4.23, 4.24, and 4.25 for
order Heterodontiformes, and the families Rhinobatidae and O. ornatus, O. maculatus, and O. halei, respectively, making them
Triakidae were found in stomach contents. Prey taxa were all tertiary consumers.
mostly demersal, only two prey groups (Carangidae and
Scombridae) being identified as pelagic. Discussion
Although the proportion of empty stomachs was high, the data
Orectolobus halei obtained contribute to better understanding of the diet and
Bony fish (11 families) again dominated the food of O. halei in feeding habits of wobbegongs and their role in the trophic
terms of %N, %M, %F, and %IRI, and contributed more numeri- ecology of NSW coastal rocky reefs. The use of samples collected
cally to the diet than by mass (Table 2, Figure 3c). However, by commercial fishers imposes an overlying pattern of collection1276 C. Huveneers et al.
Table 2. Dietary information for wobbegongs caught in NSW. Prey categories, demersal (D), predominatly demersal (PD), or pelagic (P) are
based on Stevens and Wiley (1986) and descriptions from Kuiter (2000); %M is the percentage mass of each prey group; %N, the
percentage of the number of each prey group identified; %F, the percentage frequency of occurrence of each prey group; %IRI, the
percentage IRI of each prey group; general taxonomic groupings are emboldened; orders are underlined.
Prey items Prey category Orectolobus ornatus Orectolobus maculatus Orectolobus halei
%M %N %F %IRI %M %N %F %IRI %M %N %F %IRI
Cephalopoda 13.50 26.58 29.69 7.82 14.50 13.33 20.51 3.53 7.97 2.65 9.76 0.60
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Octopoda
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Octopodidae
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Octopus spp. D 11.98 24.05 26.56 32.01 14.50 13.33 20.51 23.22 7.97 2.65 9.76 2.79
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Downloaded from https://academic.oup.com/icesjms/article-abstract/64/6/1272/616342 by guest on 13 March 2019
Sepioidea
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Sepiidae D 1.52 2.53 3.13 0.42 – – – – – – – –
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Osteichthyes 86.50 73.42 87.50 92.18 78.76 80.00 97.44 95.62 79.52 92.05 97.56 97.38
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Unidentified bony fish 7.76 27.85 32.81 39.02 12.75 30.00 28.21 48.58 2.83 10.60 24.39 8.81
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Anguilliformes
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Muraenidae
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Gymnothorax prasinus D 26.24 2.53 3.13 3.03 – – – – – – – –
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Muraenesox bagio D – – – – 11.05 1.67 2.56 1.33 – – – –
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Batrachoidiformes
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Batrachoididae D 3.74 7.59 9.38 3.55 – – – – – – – –
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Beryciformes
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Berycidae D 0.02 1.27 1.56 0.07 – – – – 0.55 0.66 2.44 0.08
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Unidentified Berycidae D – – – – 0.15 1.67 2.56 0.19 – – – –
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Centroberyx affinis D – – – – 1.57 1.67 2.56 0.34 – – – –
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Clupeiformes
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Clupeidae P – – – – – – – – 1.05 0.66 2.44 0.11
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Gadiformes
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Moridae
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Pseudophycis spp. D – – – – 0.90 1.67 2.56 0.27 – – – –
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Lotella rhacina D – – – – 0.74 1.67 2.56 0.25 – – – –
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Scorpaeniformes
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Platycephalidae D 0.34 2.53 3.13 0.30 – – – – – – – –
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Perciformes
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Unidentified Perciformes 4.99 6.33 6.25 2.37 1.26 1.67 7.69 2.08 4.96 5.30 12.20 3.37
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Labridae PD – – – – 1.66 1.67 2.56 0.35 – – – –
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Achoerodus viridis PD – – – – – – – – 10.88 1.99 7.32 2.53
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Sparidae D – – – – – – – – 0.09 0.66 2.44 0.05
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Unidentified Sparidae D 6.47 2.53 3.13 0.94 0.97 1.67 2.56 0.27 – – – –
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Pagrus auratus D 22.85 11.39 14.06 16.17 18.60 6.67 10.26 10.54 – – – –
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Serranidae D – – – – 1.01 1.67 2.56 0.28 – – – –
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Arripidae
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Arripis trutta P – – – – – – – – 0.61 0.66 2.44 0.08
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Carangidae P 1.07 2.53 3.13 0.38 – – – – – – – –
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Trachurus novaezelandiae P – – – – 1.28 5.00 7.69 1.97 27.10 52.98 31.71 68.33
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Scombridae
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Scomber australasicus P – – – – 5.50 10.00 10.26 6.47 6.84 13.91 14.63 8.17
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Mugilidae PD 0.32 1.27 1.56 0.08 – – – – – – – –
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Mugil cephalus PD – – – – 0.83 1.67 2.56 0.26 – – – –
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Kyphosidae
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Unidentified Kyphosidae D 0.68 1.27 1.56 0.10 – – – – 10.66 1.32 4.88 1.57
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Girella tricuspidata D 10.27 2.53 3.13 1.35 0.80 3.33 5.13 0.86 0.05 0.66 2.44 0.05
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Girella sydneyanus D 1.14 1.27 1.56 0.13 – – – – – – – –
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Scorpis spp. D – – – – 11.05 1.67 2.56 1.33 – – – –
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ContinuedQuantitative diet assessment of wobbegongs in New South Wales 1277
Table 2. Continued
Prey items Prey category Orectolobus ornatus Orectolobus maculatus Orectolobus halei
%M %N %F %IRI %M %N %F %IRI %M %N %F %IRI
Sciaenidae
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Argyrosomus japonicus PD – – – – 5.02 1.67 2.56 0.70 11.63 1.32 1.70 1.70
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Pempherididae
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Pempheris spp. D 0.08 1.27 1.56 0.07 – – – – – – – –
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Dinolestidae
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Dinolestes lewini D – – – – 3.22 1.67 2.56 0.51 – – – –
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Uranoscopidae
Downloaded from https://academic.oup.com/icesjms/article-abstract/64/6/1272/616342 by guest on 13 March 2019
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Kathetostoma leave D – – – – – – – – 0.44 0.66 2.44 0.07
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Tetraodontiformes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Diodontidae D – – – – 0.14 1.67 2.56 0.19 – – – –
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Dicotylichthys punctulatus D – – – – – – – – 1.83 0.66 2.44 0.16
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Monacanthidae D 0.53 1.27 1.56 0.09 – – – – – – – –
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Eubalichthys spp. D – – – – 0.26 1.67 2.56 0.20 – – – –
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Chondrichthyes – – – – 6.74 6.67 10.26 0.85 12.51 5.30 19.51 2.02
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Carcharhiniformes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Triakidae D – – – – 4.05 1.67 2.56 0.60 – – – –
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Orectolobiformes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Orectolobidae
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Orectolobus ornatus D – – – – – – – – 2.33 0.66 2.44 0.20
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Heterodontiformes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Heterodontidae D – – – – 1.15 1.67 2.56 0.29 – – – –
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Heterodontus portusjacksoni D – – – – – – – – 2.76 0.66 2.44 0.22
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Rajiformes
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Rhinobatidae D – – – – 1.54 3.33 5.13 1.02 3.33 2.65 9.76 1.57
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . . . . . . .. . . . . . . . . .
Aptychotrema rostrata D – – – – – – – – 1.27 0.66 2.44 0.13
times and areas. Results may also have been influenced by tem- feed on, bait. One O. halei was found with 19 bony fish in its
poral or spatial variation in prey availability. However, the main stomach, but still took the bait. Regurgitation of the stomach
fish fauna does not differ across the NSW state, and wobbegong contents was often observed when wobbegongs were brought to
prey species are found throughout the sampling locations the surface and onto the boat, and may have been an attempt to
(Yearsley et al., 1999; Hutchins and Swainston, 2001). Sampling dislodge the hook (CH, pers. obs.). Regurgitation of stomach con-
was throughout the year, with all species caught at each location, tents is likely to explain the high percentage of empty stomachs
except at Sydney where O. ornatus is not found. Therefore, recorded (Wetherbee and Cortés, 2004), but infrequent feeding
spatial and temporal biases attributable to prey availability are or short periods of feeding followed by periods of rapid digestion
expected to be minimal. cannot be discounted.
The total combined percentage of empty stomachs was 80% Overall, 80 –90% of the wobbegongs examined were hooked in
when wobbegongs were caught on setlines, and 50 –65% when the cardiac stomach or anterior oesophagus. Wobbegongs feed in a
caught in traps or while scuba diving. These values are high similar manner to angel sharks (Squatina australis), but take prey
when compared with those of other species of shark (Wetherbee in front of the shark (Compagno, 2001). The short broad mouth
et al., 1990; Simpfendorfer, 1998; Joyce et al., 2002; Morato and large broad pharynx produces suction, and prey items are
et al., 2003). Nevertheless, they were consistent with other wobbe- usually swallowed whole. This behaviour may explain why hooks
gong diet studies (Cochrane, 1992; Chidlow, 2003), which found were embedded more frequently in the cardiac stomach than in
that 60 –70% of stomachs examined were empty. The use of the mouth. Although most commercial fishers in NSW use
setlines may explain the high percentage of empty stomachs J-shaped hooks to catch wobbegongs, research elsewhere (e.g.
(Cortés, 1997). Bait is likely to be more attractive to hungry Cooke and Suski, 2004) has shown that the use of circle hooks
sharks rather than to those with full stomachs, because fish that can decrease the proportion of stomach-hooked animals and, on
feed to satiation have a reduced response to the odour of bait occasions, cause a simultaneous reduction in overall catch. The
(Lokkeborg et al., 1995). The greater percentage of stomachs environmental impact statement for the NSW Ocean Trap and
with prey in wobbegongs caught in traps and while scuba diving Line Fishery (NSW DPI, 2006) has recommended a minimum
support this. However, Chidlow (2003) showed that 70% of wob- legal size limit of 130 cm total length for all species of wobbegong.
begongs caught in gillnets had empty stomachs. Moreover, many Consequently, future research should examine the effects that
wobbegongs were captured with full stomachs and bait, indicating J-shaped and circle hooks have on catches and post-release
that wobbegongs with full stomachs may still be attracted to, and mortality of individuals less than this recommended size. It is1278 C. Huveneers et al.
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Figure 3. Three-dimensional graphic representation of diet separated by family in (a) Orectolobus ornatus, (b) O. maculatus, and (c) O. halei.
Only prey families with at least one of the quantifying parameters .10% are represented in the graph to avoid clustering minor prey items
close to the origin of the axis.
imperative that such studies be done before the introduction of T. novaezelandiae and S. australasicus form large schools close to
size limits, because the results of this study (i.e. the stomach- or the seabed during periods of low water temperature. The greatest
oesophagus-hooking of 80 –90% of all wobbegongs) suggest that proportions of T. novaezelandiae and S. australasicus were in
a minimum size limit will result in unquantified, fishing-related stomachs of O. halei caught off Sydney in July, when water temp-
mortality. Introducing such management action does not adhere erature is low (i.e. ,168C), suggesting that O. halei might have fed
to the principles of ecologically sustainable development, nor on these prey species when they were close to the seabed.
would it be in line with the objectives of the National Plan of In Western Australia (WA), Chidlow (2003) found that bony
Action for the Conservation and Management of Sharks in fish were the dominant prey of wobbegongs, with occurrences of
Australian waters (Shark Advisory Group and Lack, 2004). 60% and 66.7% in O. ornatus and O. maculatus, respectively.
The diets of wobbegongs in NSW waters were dominated by The present study found a large proportion of bony fish, about
bony fish, with cephalopods and chondrichthyans also important. 95%IRI in all three species, similar to the results of earlier
Most of the prey species were demersal, closely associated with studies in northern NSW (Cochrane, 1992). Trachurus novaezelan-
reef ecosystems, and consistent with the habitats of wobbegongs diae and S. australasicus were numerically important prey of
and previous descriptions of their diet (e.g. Last and Stevens, O. halei, with multiples of both prey species found in single
1994; Compagno, 2001; Chidlow, 2003). Only a few prey items stomachs, e.g. up to ten T. novaezelandiae and nine S. australasicus
were classified as pelagic. Midwater schooling fish such as in the stomach of one large O. halei (1800 mm TL), possiblyQuantitative diet assessment of wobbegongs in New South Wales 1279
inflating the IRI. However, the relative importance of carangids Orectolobiformes (average 3.6, maximum 4.1; Cortés, 1999).
and scombrids was diminished when %F was considered, However, the estimated TL for Orectolobiformes from Cortés
because few wobbegongs consumed pelagic species. Prey items (1999) did not include the Orectolobidae. The high TL of wobbe-
with large mass and low frequency, such as P. auratus in O. gongs indicates that they are top predators, although in part this is
ornatus or A. japonicus in O. halei, were only found in a few wob- attributable to the chondrichthyans (TL 3.65) found in the diet of
begongs, so the IRI was enhanced by the prey’s gravimetric O. maculatus and O. halei and to cephalopods in the diet of O.
importance. ornatus. Cortés (1999) did not find elasmobranchs in the diet of
Previous reports have suggested that the diet of wobbegongs any Orectolobiformes, explaining their lower average TL of 3.6.
includes other sharks and possibly cannibalism for O. maculatus Given the high TL of wobbegongs [higher than seabirds and
(Coleman, 1980; Compagno, 2001), but we did not find evidence similar to some marine mammals (Cortés, 1999)], the removal
of cannibalism. Cochrane (1992) failed to find any evidence of of these top predators may potentially have top-down effects on
chondrichthyan prey in his study of the diet of wobbegongs, but their prey and other lower level consumers. Several authors have
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Chidlow (2003) and we, in this study, did find sharks and rays asserted that trophic cascades are rare in large, diverse ecosystems
in wobbegong stomachs. The presence of O. ornatus in the buffered by multiple trophic links and spatial heterogeneity
stomach of an O. halei and several observations of feeding beha- (Strong, 1992). Therefore, there are debates whether sharks exert
viour (R. Brislane, Nambucca Heads, pers. obs.; P. Hitchins, significant top-down effects (Stevens et al., 2000; Kitchell et al.,
South West Rocks Dive Centre, pers. obs.; CH, pers. obs.) 2002). However, the removal of large, predatory fish, including
confirm that O. ornatus is regularly consumed by O. halei. sharks, has led to species declines and changes in community
Cephalopods were noted as prey of wobbegongs in this study structure through competitive (Fogarty and Murawski, 1998)
and also by Cochrane (1992) and Chidlow (2003). However, the and predatory release (Baum et al., 2003; Shepherd and Myers,
IRI for cephalopods in NSW (0.5 –7.8%) was much lower than 2005; Ward and Myers, 2005; Myers et al., 2007). Ecosystem
in WA (28%; Chidlow, 2003). The lesser proportion of cephalo- models exist for southeastern Australia (Goldsworthy et al.,
pods in wobbegongs from NSW than in WA was offset by the 2003), but they do not include sharks, hindering assessment of
increased proportions of bony fish and chondrichthyans. the effects of wobbegong removal on animals at lower TLs. The
Octopuses were clearly the dominant cephalopod prey in NSW development of an ecosystem model that includes chondrichth-
and WA, reflecting their presence in nearshore rocky habitats yans and identifies the effects of their removal in NSW waters is
and the demersal feeding behaviour of wobbegongs. clearly needed.
We found no crustaceans in wobbegong stomachs, agreeing
with the findings of Chidlow (2003), but contrasting with those Acknowledgements
of Cochrane (1992), who reported that crustaceans were taken at We thank Reala Brislane, Jason Moyce, Ian Puckeridge, Mark
a %F of 6.6 (though derived from a single crustacean found in Phelps, and Shannon Fantham for assistance on board their
the stomach of one individual). Other authors (e.g. Whitley, fishing vessels, and several interns and volunteers for help with
1940; Stead, 1963; Last and Stevens, 1994; Compagno, 2001) have sampling. We also gratefully acknowledge the analytical assistance
reported crustaceans in the diets of wobbegongs. Crustaceans may of Terry Walker, and the reviews by Simon Allen, Joe Bizzaro, and
feature in the diets of neonates and/or juvenile wobbegongs, reflect- two anonymous referees, all of which helped us improve the
ing possible ontogenetic changes in diet. Small O. ornatus manuscript. CH was supported by an international Macquarie
(,600 mm total length), and O. maculatus and O. halei (each University Research Scholarship. Financial support was provided
,1100 mm total length) could not be sampled in the present by the Graduate School of the Environment, NSW Department
study, but perhaps should be the focus of future research. of Primary Industries, and the Australian Geographic Society.
Overlap indices and the ANOSIM suggested that the diet of The study was undertaken under the NSW DPI permit number
O. halei was statistically different from that of O. ornatus. PO03/0057 and a Macquarie University Ethics Committee
However, there were no differences between O. ornatus and approval number 2003/011.
O. maculatus, or between O. maculatus and O. halei. Interspecific
differences in dentition were not evident (Huveneers, 2006) and
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