FIRST RECORD OF THE FRESHWATER SAWFISH, PRISTIS MICRODON, FROM SOUTHWESTERN AUSTRALIAN WATERS

2007·0.86 MB·English

by  Justin A Childlow

Recordsofthe WesternAustralianMuseum 23:307-308 (2007). Short communication
First record of the freshwater sawfish, Pristis microdon,
from southwestern Australian waters
JustinA. Chidlow
DepartmentofFisheries,WesternAustralianMarineResearchLaboratories,
POBox20, NorthBeach,WesternAustralia6920
Email:[email protected]
Sawfishes (family Pristidae) are large (up to 7m) (Last and Stevens 1994; Compagno and Last 1998).
modified batoids with a blade-like snout edged Pristismicrodon mayalsooccurin theAtlanticand
withpairsofrostralteeth.Theyoccurworldwidein eastern Pacific if P. perotteti Muller & Henle, 1841
sub-tropical and tropical shallow coastal sea, and P. zephyreusJordan & Starks in Jordan, 1895
estuaries and freshwatersystems (Lastand Stevens are synonymised with this species (Compagno and
1994; Compagnoand Last 1998).Therearebetween Last 1998). In Australia, the freshwater sawfish is
five and seven recognised species worldwide, with known to occur in the Ord, Durack and Fitzroy
five species represented in Australian waters (Last Rivers (Western Australia), the Adelaide, Victoria
and Stevens 1994). Sawfish populations have been and Daly Rivers (Northern Territory), and the
extirpated from many parts oftheir original global Gilbert, Mitchell, Norman and Leichhardt Rivers
range by gillnetting and trawling and are easily (Queensland) (Last and Stevens 1994; Pogonoski et
entangled in nets by their toothed rostra al. 2002; Thorburn etal. 2004). Only recentlyhas P.
(Simpfendorfer2000).Thelittlethatisknownabout microdon been reported from marine waters
thebiologyofsawfishsuggeststhey have low rates (Thorburn etal.2004).
of reproduction (Tanaka 1991; Compagno and Last
1998; Wilson 1999; Simpfendorfer 2000; Thorburn SouthwesternAustralianP.microdon
teotafl.is2h0i0n4g).geTahri,smcaomkbeinseawdfiwsihthathheiigrhsursicsekptsipbeicliietsy coAmmefrecmiaalleshPa.rkmfiicshreordoopenrawtiansgdceampetrusraeldgilblynetas
acrnidticaallllyhaevnedasnugbeserqeudenutnldyebreetnhelilstUeCdNgloRbeadllyLiasst Finebsrouuatrhywes2t0e0r3n.AuTshtrealicaanptwuarteersloocnattihoen 5*waosf
Assessment2006(Compagnoetal.2006). approximately six miles east of Cape Naturaliste
(33°31'S,115°07'E)in32mofwater.Thesawfishwas
PristismicrodonLatham,1794 estimatedtobe3.5m in lengthTLwhenlandedand
Pristismicrodonisa mediumtolargesawfishthat appeared to be healthy. The specimen was
in Australia grows to at least 361cm TL (Tanaka processed and the fisher retained the remaining
1991), but is reported to reach up to 700cm TL in trunk, fins and saw. I positively identified the
other locations (Last and Stevens 1994). They are processed sawfish as P. microdon using an
born at around 50cm in length after a five month identification kev provided by Last and Stevens
gestationperiod,withlittersizesrangingbetween 1 (1994).
and 12 (Wilson 1999). In the western Atlantic P. The partial length (origin ofthe firstdorsal fin to
microdonmaturesatbetween240cm and300cmTL the insertion point of the second dorsal fin) was
t(wCoompmaaglneosapnedciLamsetn1s998f)r.oTmanNaekaw(1G9u9i1)nerae,porotneed 9ha5lfc)m.T(haepprrosotxriamlastaewalsentghtehtwrausnk79hcamdwbietehn19cuptairisn
measuring 247cm that was immature and a 361cm of teeth that extended to the basal quarter of the
specimen thatwas mature. In Australian waters, P. saw(Figure1).Theinterspacebetweenrostral teeth
microdon feeds on fish such as catfish, small at the base of the saw was 4cm, and 3cm between
crustaceans and molluscs (Allen 1982; Cliff and the teeth at the tip ofthe saw (Figure 1). A groove
Wilson 1994; Pogonoski etal. 2002; Thorburn etal. waspresentalongtheposteriormarginofall rostral
2004). teeth. The origin of the first dorsal-fin was located
Pristis microdon occurs inshore and in intertidal anterior to the pelvic-fin origin and the height of
areas and isusually found in freshwater drainages, thefirstdorsal-finwas 32cm. Thesecond dorsal-fin
lakes and estuaries where itcan penetrateas far as heightwas31cm. Theventral lobeofthecaudal-fin
400km from the coast (Morgan et al. 2004). In the was small, but distinct. The upper and lower
Indo-West Pacific it ranges from New Guinea, SE postventral caudal-fin margins measured 44.5cm
Asia, northern Australia and west to South Africa and 11.5cmrespectively.
308 J.A.Chidlow
Figure1 Rostral saw from a female Pristis microdon, measuring approximately 350cm in total length, captured off
CapeNaturaliste,WesternAustralia.Seetextfordescriptionofmeasurements.
This record of P. microdon from southwestern Last, P.R. and Stevens, J.D. (1994). Sharks and rays of
Australia extends the range of the species Australia.CSIRO,Melbourne,513pp.
approximately 1600 km south of its previously Latham, J. (1794). .An essay on the various species of
known southern limit, Cape Keraudrcn, Western sawfish. Transactions of the Linnean Society of
Australia (Thorburn ef al. 2004) and provides London2(23);273-282.
further confirmation that P. microdon utilizes Morgan, D.L., Allen, M.G., Bedford, P. and Horstman,
marinewaters. M. (2004). Fish fauna of the Fitzroy River in the
Kimberley region of Western Australia - including
Bunuba,Gooniyandi, Ngarinyin, Nyikina and
ACKNOWLEDGEMENTS WalmajarriAboriginalnames.Recordsofthe Western
AustralianMuseum22:147-161.
inIfowrimsehd ttohetWShhAaanrkk JR.esNeealrscohnSewcthioon,thDoeupgahrttfmuelnlty .MulBleesr,chrJeiabnudngHdeenrleP,lagFi.Go.sJt.om(e1n84B1e)r.linS.yPsltaegmiaotsitsocmheen
of Fisheries of the capture, and provided i-xxii+1-200.
atshseisstpaencciemeinn.id1enwtoiufylidngalasnodlickoelletoctitnhgandkataP.fLraosmt PogoCnoonsskeir,vatJ.iJ.o,nPoovlelarrvdi,ewD.aAn.daacntdionPapxltaonnf,orJ.ARu.st(r2a0l0i2a)n.
from CSIRO Marine Research, Hobart, R. McAuley threatened and potentially threatened marine and
from Department of Fisheries WA, Perth and C. estuarine fishes. Environment Australia, February
Simpfendorfer from the Mote Marine Laboratory, 2002.
Florida for theirassistance in positively identifying Simpfendorfer, C.A. (2000). Predicting population
thespecimen. recovery rates for endangered western Atlantic
sawfishes using demographic analysis.
EnvironmentalBiologyofFishes58:371-377.
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