Records of the Western Australian l\luseum 23: 7-1 I (2006).

Distribution of the spotted minnow (Galaxias maculatus (Jenyns, 1842»(Teleostei: Galaxiidae) in Western Australia including range extensions

and sympatric species

David L. Morgan, Andrew Chapman, Stephen J. Beatty and Howard S. Gill

Centre for Fish and Fisheries Research, Murdoch University, South Street, Murdoch, Western Australia 6150

Abstract Galaxias maculatus was captured from a number of rivers outsideits previously known range. In Western Australia, it was formerly onlyknown from rivers and lakes between the Goodga River (Two People's Bay,30 km east of Albany) and the Dailey River (50 km east of Esperance), withadditional records from the Boat Harbour Lakes (Kent River). An intensivesurvey of the inland fishes in rivers and lakes along the south coast ofWestern Australia has extended its distribution east by 50 km (Thomas River),west by approximately 40 km (Walpole River) and north by 400 km (HarveyRiver). The Western Australian Museum also has a specimen from theCanning River, a further 100 km north. Field salinity tolerance of Gmaculatus was high, with fish found alive in 81 mScm 1 (-45 ppt). Thefreshwater piscifauna east of, and including, the Pallinup River isdepauperate, with G. maculatusbeing the only freshwater species present. Allsympatric teleosts are tolerant of salinity and, with the exception of theintroduced Gambusia holbrooki, are estuarine, including Pseudogobius olorum,Leptatherina wallacei and Acanthopagrus butcheri.

INTRODUCTION

The Spotted Minnow, Common Galaxias orCommon Jolly tail (GaJaxias macuJatus (Jenyns,1842» is a small, elongate, partially translucent,scaleless, osmeriform fish (Figure 1). It is one ofthe most widely distributed freshwater fishes inthe world (Berra et aJ. 1996; Waters et aJ. 2000),with populations occurring in Australia, LordHowe Island, New Zealand, Chatham Islands,Falkland Islands and South America. Both land­locked (i.e. complete their life-cycle in inlandwaters) and catadromous (with a marine larvalphase) populations are recognised, and thiswidespread distribution has been attributed to thepresence of catadromous populations throughoutits range in eastern Australia, New Zealand andSouth America, with the larvae moving into thesea after hatching (Benzie 1968; Pollard 1971;McDowall et aJ. 1975). The presence of G.macuJatus in Western Australia was first reportedby Coy (1979) and jv1cDowall and Frankenberg(1981), where the distribution was thought toextend from the Goodga River in the west to thestreams around Esperance (see Figure 2). Jaensch(1992) later reported a single specimen to the westof the Goodga River in the Boat Harbour Lakes(Kent River) (Jaensch 1992) (Figure 2).

This paper presents new data on the distributionof G. macuJatus within Western Australia andextends the range of the species in this State.

MATERIALS AND METHODS

This study focused on sampling the fish fauna inthe rivers and lakes east of, and including, thePallinup River on the south coast of WesternAustralia, excluding estuaries. Fish were sampledprimarily using a combination of fine mesh seinenets in 148 sites between the Pallinup River andPoison Creek (east of the Thomas River, see Figure2). Data presented in Morgan et aJ. (1998) were usedfor the distribution of G. macuJatus to the west ofthe Pallinup River, while the unpublished reportsby Morgan and Beatty (2003a, b) were utilised forthe occurrences of G. maculatus in the Walpole andHarvey rivers, respectively.

Species distribution maps were created using sitelatitude and longitude data in the program MapInfo(Maplnfo Corporation 1998).

Dissolved oxygen, temperature and conductivitywere measured in situ with a WTW Multiline P4meter. Unless otherwise stated, measurements weremade immediately below the water surface.

RESULTS

Distribution of Galaxias maculatus in WesternAustralia

During this study G. macuJatus was capturedfrom the following rivers and lakes within itspreviously known range: Goodga and Angove

8 D.L. Morgan, A. Chapman, S.J. Beatty, H.S. Gill

Figure 1 The spotted minnow (Galaxias maculatus).

rivers (Morgan et al. 1998), Pallinup, Bremer,Gairdner, Fitzgerald, Hamersley, Phillips, Steere,Jerdacuttup, Oldfield, Munglinup, Torradup,Young, Lort and Dalyup rivers; Yallobup, Kateup,Coramup and Bandy creeks; Moates, Gardner,Angove, Wheatley, Mullet and Woody lakes (Figure2). Additionally, G. maculatus was captured from:Lake Boolenup and the Thomas River,approximately 100 km east of Esperance; theWalpole River, approximately 140 km west of theGoodga River; and in a drainage canal of BancellBrook, a tributary of the Harvey River,approximately 580 km west and north from theGoodga River by coast (Figure 2).

Sympatric speciesThe estuarine Swan River Goby (Pseudagabius

alarum) was found in the majority of systemsbetween the Pallinup and Thomas rivers; theWestern Hardyhead (Leptatherina wallacei) wasfound from the Pallinup River to Bandy Creek;Black Bream (Acanthapagrus butcheri), wascaptured with G. maculatus in the Oldfield Riverand in Wheatley and Woody lakes; and theintroduced eastern Mosquitofish (Gambusiahalbraaki) was found only in the Pallinup River(Figure 3).

Environmental variablesGalaxias maculatus was captured in

conductivities ranging from 0.3 to 94.4 mScm-1, andtemperatures from 12 to 30°C, however, all fishfound in conductivites greater than 88 mScm-1 weredead, yet in all salinities <81.6 mScm-1 (-45 ppt) theywere alive. Field measurements and repeatedobservations revealed that when dissolved oxygenlevels were less than 1.5 mgl-1 at 30 cm depth, G.

maculatus approached the surface to respireaerially. In these instances the surface dissolvedoxygen concentration was always marginally higherthan that at 30 cm. Furthermore, dead fish wererecorded on several occasions when watertemperatures were >30°C and salinity was <2 ppt.

DISCUSSION

During this study the range of G. maculatus wasextended considerably, i.e. east to Lake Boolenupand the Thomas River, approximately 100 km eastof Esperance; west to the Walpole River,approximately 140 km west of the Goodga River;and, in a drainage canal of Bancell Brook, atributary of the Harvey River, approximately 580km west and north from the Goodga River by coast(see Figure 2). The data presented here highlightsthe absence of studies of the inland fish fauna onthe south coast of Western Australia.

There is a marked reduction in the number ofspecies of native freshwater fish from west to eastalong the south coast of Western Australia. Tenfreshwater fish species occur in the region with amoderate Mediterranean climate to the west of, butnot including, the Pallinup River (Morgan et al.1998; Allen et al. 2002), whereas only onefreshwater species (i.e., G. maculatus) occurs in theregion with a dry Mediterranean climate east of thePallinup River (this study) (Figure 2). The ranges ofG. maculatus and the estuarine P. alarum extend tothe eastern most river on the south coast, i.e. theThomas River (Figures 2 and 3), while the estuarineL. wallacei extends as far east as Bandy Creek. Thespecies composition of the rivers east of, andincluding, the Pallinup River is a reflection of thehigher natural salinities of these lower rainfall

Galaxias maculatus in Western Australia

SOUTHERN OCEAN o

9

Figure 2 The sites that Galaxlas 71l1lClIlatlls were captured at during this study and from those specimens housed in theWestern Australian Museum.

systems than for those rivers to the west. Thus, onlyspecies that are salt tolerant are found in the riverseast of the Pallinup. The feral G. holbrooki is able totolerate salinities up to -60 ppt (Morgan et al. 2004)but does not currently extend east of the PallinupRiver however it is found in most of the riversystems west of the Pallinup and north to the HuttRiver, approximately 450 km north of Perth (seeMorgan et a1. 1998, 2004). This species is known toseriously impact other small south-western WesternAustralia fishes (Gill et al. 1999), yet it is not clearwhat impacts it has on the species in the PallinupRiver. It is probably inevitable that it will eventuallybe introduced into other rivers on the south coast ofWestern Australia.

During the current study, the number of G.maculatus captured at those sites within itspreviously known range was far greater than thoserecorded to the west of its previously known range(i.e., Walpole and Harvey rivers) For example,despite extensive sampling, only four and oneindividuals were captured in the Walpole andHarvey rivers, respectively (M organ and Beatty2003a, b). Therefore, these individuals, particularlyin the case of those in the Harvey River, are eitherindicative of populations with very low abundances

or are simply marine stragglers. It is likely that theestablishment of new, self-maintaining populationsis only achieved when adequate numbers migrateinto these systems and environmental tolerances,particularly salinity and possibly temperature, arenot exceeded. For example, while G. maculatus isextremely tolerant to high salinity (acute LDso of 45ppt, Chessman and Williams (1975) and supportedby field observations in this study), watertemperatures experienced on the west coast ofWestern Australia (e.g., Harvey and Canning rivers)may often exceed 30°C during summer, atemperature that Richardson et al. (1994) suggest islethal to at least some New Zealand populations.

Previous workers have faced uncertainty whetherWestern Australian G. maculatus were land-lockedor diadromous, though on the basis of an inlandbreeding record from the Pallinup River, the formerwas suspected (Alien 1982). A recent detailed studyon the biology of G. maculatus in south-westernAustralia that included populations in the Goodga,Phillips, Oldfield and Jerdacuttup rivers confirmsthat, over most of its range in Western Australia, G.macuJatus has a self sustaining, land-lockedbreeding strategy (Chapman 2004). Furtherevidence for this is the presence of fish in the

10 D.L. Morgan, A. Chapman, 5.J. Beatty, H.5. Gill

ioCl

[J Pseudagabius alarum

o Leptatherina wallacei

* Gambusia halbroaki

..." ...> ...

i:2 " "> ... >... 0- i:2 " i:2>" g -0 i:2...

> t: "i:2 ;;l 0; 0 >u tl: Oll .....l i:2

'" '" -0 C

~ "E (5;;l 0- >->.,.0 1 ~~ >- -0 ".c c;; a ~

0.. Cl coU

1

SOUTHERN OCEAN o

WESTERNAUSTRALIA

lOOkm

.'

Figure 3 The distribution of the three sympatric species captured within the main range of Galaxias maclIlatlls.

Jerdacuttup River, which has probably not hadcontact with the sea for 6 000 years (Hodgkin andClark 1990). In other rivers, occasional contact withthe sea by either adult or larval fish is a possibilityas raised beach bars can either be breached byflooding, vigorous winter flow or humanintervention (artificial excavation).

McDowall (1988) considered that diadromousgalaxiids represented the primitive or ancestralstock and that freshwater limited populations werea more recently derived phenomenon. Waters et al.(2000a) proposed that the loss of the primitivemarine juvenile phase may be an importantmechanism of galaxiid speciation. It is very likelythen that on the south coast of Western Australiathe land-locked strategy has developed fromdiadromous stock in response to changes to localcoastal geomorphology over recent geologicaltime, with most of the rivers of the region nowbeing only intermittently open. For example,Culham Inlet, previously the Phillips Riverestuary, where G. maculatus is confirmed toundergo a land-locked life-history (Chapman2004), was permanently open to the sea as recentlyas 3 500 years ago but is now better described as acoastal salt lake (Hodgkin 1997). Most of theregion's rivers are now open to the sea only aftermajor rainfall events.

Although the presence of diadromouspopulations of G. maculatus in rivers on the southcoast was not demonstrated during the presentstudy, its presence in the Walpole River, whichenters the sea via a permanently open channel atthe mouth of the Nornalup Inlet (Hodgkin andClark 1988), suggests that that there is at least thepotential for diadromy in Western Australia.

Recent allozyme (Berra et al. 1996) andmitochondrial (Waters et al. 2000b) studies havedemonstrated the considerable powers of dispersal,due to a marine larval stage in some populations, ofG. maculatus. For example Berra et al. (1996)considered that gene flow continues to occurbetween Australia, New Zealand and SouthAmerica, and whilst Waters et al. (2000b) confirmedgene flow between Australia and New Zealand,they were less convinced that dispersal occurredacross the Pacific. It is likely that the presence of G.maculatus in the Walpole and Harvey rivers, is aresult of larval drift via ocean currents from eitheroutside Western Australia or from a south coastriver. The collection of more mitochondrial data isrequired to test which of these hypotheses is themore likely. Such data would also permitcomparisons of the genetic structure of populationswithin Western Australia, and between WesternAustralia, eastern Australia, New Zealand and

-------------------------------------------.

Galaxias maculatus in Western Australia

South American populations, i.e. is there regulargene flow between systems?

ACKNOWLEDGEMENTS

We would like to thank the Natural HeritageTrust, Murdoch University, Department ofFisheries, Water and Rivers Commission, HarveyRiver Restoration Trust and Fishcare WA forproviding funds towards this project. Thanks toCALM for providing permits to sample in NationalParks and A Class Reserves. Thank you to CharlotteMorgan for help with sampling.

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11

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Manllscript received 19 lmwan; 2004; accepted 23 March 2005