The distribution of elasmobranchs indicates the location on the coasts of Sabah where each have been observed (see Map 1, Manjaji, this volume, b). Their abundance was Table 3. Comparisons
Total length
Pectoral posterior margin Mouth width
Mouth length Vertebral numbers Coloration
of morphometric of Mustelus Mustelus sp.1 Mustelus sp.2
KPU-BKK BKK 1 9196 30 15496 940mm
lobe tip black
spp. from Sabah.
Mustelus sp.2 Mustelus sp.2 BKK BKK 32 15497 7 6397
468mm
Table 4. Comparisons of morphometric of Mustelus manazo, M. antarcticus,
N.a: not available
Mustelus manazo (Compagno, 1984) Large, 1.7-2.5 times preorbital length and 2.4-4.1% of total length
6-7.8% of total length;
preoral snout 5.7-7.5%
of total length; snout moderately long and bluntly
angularin lateral view 19-23% of total length
Narrow, 3.7-4.5%
of total length Fairly narrow, 2-2.9%
of total length Anterior margins 11-15%
of total length, width of posterior margin 7.5-14%
of total length Mouth fairly short, approx.
equal to eye length and 2.5-3.7% of total length Uppers considerably longer
than lowers and 1.9-2.5%
of total length Precaudal centra 71-91;
monospondylous centra 33-41;
diplospondylous centra 35-54 Molariform and asymmetric
with cusp reduced to a low point Buccopharyngeal denticles covering almost entire palate
and floor of mouth Pectoral and pelvic fins relatively small; trailing edges
of dorsal fins denticulate, without bare ceratotrichia;
first dorsal broadly triangular, with posteroventrally sloping posterior margin; ventral caudal
lobe not falcate in adults Uniform grey or grey-brown above, light below, usually with
numerous white spots but no dark spots or dark bars
Mustelus antarcticus (Compagno, 1984) Fairly large, 1.6-3.2 times
preorbital length and 2.4-4.2% of total length 5.8-7.8% of total length;
preoral snout 5.7-7.4%
of total length; snout moderately long and bluntly
angular in lateral view 19-23% of total length Fairly broad, 3.7-5.1%
of total length Broad, 2.6-3.2%
of total length Anterior margins 12-16%
of total length, width of posterior margins 8-13%
of total length Mouth short: length subequal to eye length and 3-3.6% of total length Uppers considerably longer
than lowers and 2-2.8%
of total length Precaudal centra 76-86;
monospondylous centra 35-38;
diplospondylous centra 39-50 Molariform and asymmetric
with cusp reduced to a low point Buccopharyngeal denticles
confined to tongue and anteriormost part of palate
Pectoral and pelvic fins relatively small; trailing edges
of dorsal fins denticulate, without bare ceratotrichia;
ventral caudal lobe more or less falcate in adults
Grey or grey-brown above, light below, usually with numerous small white spots
but without dark spots or dark bars
and /W.sp.A
Mustelus sp. A (Last and Stevens, 1994)
Eyes oval, dorsolateral on head
Relatively long (preoral length 6-6.3% of total length),
tip relatively narrow and pointed Interdorsal ridge present Relatively narrow, 5.6-6.0%
of total length 2.4-2.7% of total length
N.a.
Mouth relatively narrow length 1.1-1.3 of width Uppers 0.8-1.1% of total length, shorter than lowers
Total: 138-146;
precaudal centra 90-92;
monospondylous centra 34-37 Cusp rather high, teeth in both jaws flattened, arranged
in a pavement-like pattern Buccopharyngeal denticles confined to anterior end
of mouth
Second dorsal fin considerably larger than anal fin; pectoral fins moderately broad, weakly falcate; apices pointed. Caudal fin with deep subterminal notch
Uniformly bronze or greyish-brown dorsally, pale ventrally (lacking white spots on the body). Second dorsal and upper
caudal-fin tips usually with dark margins; pectoral and
caudal fins with pale posterior margins.
estimated using a log, rapid estimate of abundance (Table 1). This numerical procedure, was only initiated in February 1997 and continued up to the end of the project period (June 1997). The results presented in the following are the average of the five months when such data are available. It was intended that each market would be
visited at least once a week, to obtain comparable data between markets. However, this proved to be logistically unrealistic for some markets.
Analysis of the data suggests that the species are evenly distributed around Sabah. However, this may be an over-simplification and a more detailed analysis taking into
account all available data may later show up subtle variations. Indeed, some preliminary analysis by Mycock and Cavanagh (pers. comm.) has shown indications that the east coast species may be more diverse. The three shark species showing the highest abundance (average per month, class 3 of the log3 estimate) were whitecheek shark Carcharhinus dussumieri, milk shark Rhizoprionodon acutus, and scalloped hammerhead Sphyrna lewini. The rest showed an average of class 2 per month of the log3 estimate. These were C. amblyrhyncoides, C. amblyrhynchos, C. brevipinna, C. limbatus, C. sorrah, all of the family Carcharhinidae;
Chaenogaleus macrostoma and Hemigaleus microstoma of the family Hemigaleidae, and Mustelus sp. of the family Triakidae. Mustelus showed a possible seasonality pattern and were only observed in markets during the beginning of the year (February-May in 1996 and 1997). Further research to collect more data is needed to support these observations.
For rays, higher abundances were recorded, (average per month was class 4 of the log3 estimate), particularly for the bluespotted maskray Dasyatis kuhlii and whitespot whipray Himantura gerrardi. The latter abounds throughout the year, and mature adults were observed for the duration of the project. Other rays were observed at abundance estimate class 2 (Himantura uarnacoides, Taeniura lymma of the family Dasyatidae; Aetobatus narinari family Myliobatidae; Rhinoptera javanica family Rhinopteridae;
and Rhynchobatus cf. australiae family Rhinidae).
Interestingly, new records were made throughout the study period, with several more species seen only in the last few months of the project work. For example, the river shark Glyphis recorded from the Kinabatangan River, and the oceanic silky shark Carcharhinus falciformis, recorded only from the island of Mabul, off the south-eastern tip of mainland Sabah.
Conclusion
The elasmobranch biodiversity in Sabah is far richer than previously thought (Compagno, Last, pers. comm.) and the species occurring in this area are now well documented.
Findings from the project surveys have also added to the current knowledge level of the species concerned. The results will contribute to improvements in the systematics of some species, particularly the rays, H. uarnak and Pastinachus species complexes, which are currently still poorly known. Information gathered on the basic reproductive patterns and abundance of several species may be useful in preparing guidelines on the issuance of number of fishing gear per season/year, as an immediate action in shark and ray management strategy in Sabah.
Further analysis of seasonality patterns may also prove useful. This project has collected a great deal of the baseline data that is essential for conservation and management
strategies. Future work on the shark and ray resource should be directed towards more specific objectives, now that the elasmobranch biodiversity status has begun to be addressed.
Acknowledgements
This study has been made possible with support from the governments of Sabah (through Dept. of Fisheries-Sabah) and UK (Darwin Initiative for the Survival of Species).
The author also wishes to acknowledge the assistance provided by the following authorities: Borneo Marine Research Unit-Universiti Malaysia Sabah (BMRU-UMS) for its support midway through the project period; School of Biological Sciences- National University of Singapore (SBS-NUS) for use of its zoological laboratory facilities and reference collection; OIC of Research Section, DOF for providing office space and computer facilities for the project team members. Scott Mycock and Rachel Cavanagh, Darwin Project volunteers who collected the abundance estimate data (March-June 1997) and carried out many other field observations during the same period.
Thanks also to Scott Mycock and Rachel Cavanagh for comments on the manuscript.
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