The Historical and Current Status of Freshwater Fish in New South Wales

11 Pages·1994·2.4 MB·English

by  R. A. Faragher

Proceedings from the Symposium: Animals of New South Wales
and their History in the 20th Century
Royal Zoological Society of New South Wales
Paper presented 10 September, 1993
The Historical and Current Status of Freshwater Fish
in New South Wales
R. A. Faragherl and J. H. Harris1
'Fisheries Research Institute, New South \Vales Fisheries. P.O. Box 21, Cronulla, New South Wales 2230
ABSTRACT
Examples are given of a number of New South Wales freshwater fish species which have declined
in abundance since last century. Reasons for the declines include river regulation, changes to riparian
vegetation, erosion and siltation. The effects of alien species on the stocks of native fish are also
discussed together with possible remedial measures to restore both habitat and fish communities.
INTRODUCTION including 12 alien species (14.5%) (Table 1).
The nukhers of some species have fallen to
During the late 19th century and in the
the extent that they have been listed as
early part of this century Murray Cod Maccullo-
threatened. The Australian Society for Fish
chella peelii peelii, were abundant in the
Biology has, since 1985, published a classifica-
Murray-Darling River system. The explorer
tion of Australian threatened fishes (Harris
John Oxley (1820 in Kowland 1989) stated of
1987; Jackson 1992; Wager and Jackson 1993
the Lachlan River that "the river is rich in the
and Table 2) which presently includes 74
most excellent fish, procurable in the utmost
species (marine and freshwater). The increase
abundance. One man in less than an hour
from 59 to 74 species between 1985 to 1993
caught 18 large fish, one of which was a
reflects an increase in awareness and knowledge
curiosity from its immense size and the beauty
of the subject, more than a dramatic deteriora-
of its colours . . . it weighed an entire 70
tion, but the increase is nevertheless cause for
pounds.. . Most of the other fish taken this
concern.
evening weighed from 15 to 30 pounds." Con-
ditions have changed dramatically in the Or the 71 New South Wales native species,
intervening 174 years! 12 (16.9%) are included in the threatened
species list (Table 3), with seven species in the
Concerns over the declining abundance of categories of "Potentially Threatened" or
fish in New South Wales were raised as early "Endangered. No New South Wales species
as 1880 at the Royal Commission into the are listed as "Extinct" or "Vulnerable",
Fisheries of New South Wales. The trend of although one species is of "Uncertain Status".
declining stocks of New South Wales fresh-
water fiyh species has been paralleled and
CASE HISTORIES OF
indeed exacerbated by the degradation of fish
REPRESENTATIVE SPECIES
habitats. Some examples and the probable
causal mechanism are presented here 1. Fish of the Coastal Drainage: Diadromous
together with an account of efforts to reverse Fishes
the trend in stocks.
a. Australian Bass Macqua72a nouemuculeata
Australian bass are representative of the
CONSERVATION STATUS OF
nine catadromous species of coastal drainages,
NEW SOUTH WALES
that is, migrating to the estuary for spawning
FRESHWATER FISHES
and returning to fresh water as adults and
In New South Wales the freshwater fish juvenile fish. Bass spawn in the estuary in
fauna includes 83 species in 33 families winter (optimal salinity 8-14 g 1-I) and the
166 Australian Zoologist, Vol 29(3-4) December 1994
Table I. Regional represenlalion of fishes in New South Wales fresh rr,atel-r (dots indicate presence
in region and * indicates alien species: t refers to slxcies oanrlocated Tram their normal rangc;
rpl, sp2 refer to descriptions in McDorrall 1980).
No.rth Sourh Murray Darling
Family Species coast coast sys.tem system
.
Amhassidar A~,rhn.riirn gossizi . .
Ambmsis cn5trl?mt,i . •
Anthorsh Trigripinnis .
Angoillidae ~Ingrillrro lcrtmlis . •
Arzpilla reinhn?rltii .
Apogor~idae Glorrnmiu npnon
Ariidae Arirrr .nffei
Arhe~inidae Atlrolriosornn rnirroslomn
.
Cmrcrocepholus ornniculru . .
CrnterocepholtfiJIuuiolilts •
Crnre,acephalur rnnjorine
Cmteroc@halha(uss Icrcrurnwcn~~r~
Belonidae Stm,igyluro kr<ft>i •. .
Bovichthyidac Preurlnphntis un,illii
.
Chanidae Chanos rhonor •
Clupeidae Arevnatnlorae rebi . . .
Polamnlosn nch?nondia . .
Cobitidae ~Wi~ptgumnu~s ~pillicnr~lalzrJ* •.
Cyprinidae Ca~mixnsa ratus* . .
Cjp<?ttlc cnrpio*
Rutilru mtilu* .
Ti?rca lincax
Eleotridae Butis hrrlts •.
Gohiomorphcu auslrnlis
Cobiomorphru cnxii •. . .
H~pseleolrisc o~npre~sa . .
HyprcleolrU gnllii
.
Hypseleotris kluniiageri . . .
Hypseleolri~s pl
Hypseleahb sp2 •. •. .
Mopmda orlrpersn . . .
Mopmda moprnda .
Philypnndon pandiceps . .
Philypnodon sp I o .
Cadopsidae Gadopsir bispinom
.
Codopris mrmoralvr . o . .
Calaxiidae Galariar brenip~nnis . .
Galarbm arulnlur o .
Galariar olidus
Gal& roslrotus .
Georridae Geotrk ouslralis
Gobiidae Acanthogobiufivimanuc* .
Arenigobius bz/renahu.
Pseudugobi~uo lorum •
Redigobius rnacvmlona .
Hemirhamphidae Arramphwfcleralepic .•
Kuhliidae h'annupercu aut~olir . •
Aiawtopoca oxleyona .
Lutjanidae Lu$anus argmlimaiulnlus .
Megalopidae Megalops cypiyprinoides .
Melanotaeniidae ~Melanotaenladubouhyi .
Melanolaenkj3uukfili- •
Pseudomugil sign@ o .
Rhadinocenlm omorus
Monodactylidae MonodocQlus argenleur • o
Mordaciidae Mordack mordar .
Mordack praecox
Mugilidae AId7ichrtlof orrlen
.
Liul argmlea .
Mugil cepholw .
My- elongolu o
Myncrpetardi . .
Valamugil georgii . .
Percichthyidae Mnc~ullochelloi ki • . .
M, macqua7icnrh t . .
M. pecliipeelii -7
Macquarin nmbigua *i
Macquoria aurhalacka o
Macquoria colonmum • o
Macqurin navemaculeata • o
December 1994 Australian 7001ogist, Val. 29134) 167
-(yy61 s!meH moJd) 4u!u~eds
JO aql JO sn%nvp ue Llnr Su!~np' puomq~!aq lroN Zl IVJL
le hnqsa~neaq~l jo (ru) 1q8!aq ~eadp ue '(dep lad IN) dsmuopuq sntar u!mla,un
lah!a 0103 aql jo a;i~eqx!pd lqluour axelane q i !p~a izdmo, orudqm opudow
s! aauepunqe a;ielua=~adp opad dead ZT e J~AOs seg d~nq rn~o~z,llrron~ .9~3
-saxmeH 10 amepunqe ssep-lead le!l!u! an!lelax -I a~d!.+ nqnnuuro rnlqJa3oiavu2 pan!nsa~
o~,m~lv~~.w~aa!~al~eum!mbla~la~p ul
6161 iL61 SL61 CL61 IL61 6961 rnlrdp!q rnun<v!g
\ 1" ouamour ral>o~to~ord
A
xi,~an~m3v,uow paualearql
6S b9 P9 59 69 Zi bL 1 ~ ~ ~ 1 .
El 91 91 61 FI PI 91 mmelsu!elra~un
fiZ E6 IF OF ZE 06 LZ par2!nsag
z z I. z z z E aleu!rulalapul
paualeaq
F S L O I I I blle!lua~od
P E C 9 9 E 9 alqelau(nA
P f 9 8 6 I I I I palaXrlepu3
0 0 0 0 0 0 0 13U!lY3
.sseq u1 Iualuqnmai uo!lelndod jo ale1 aql
Su!~npa.i 's~ogq 8!q asaql jo Ouanbalj
aq, passaiddns seq sruep Xq uo!lelnsai
pea id sap!^ 'laAaM0~'( 8861 S!lleH) (1 .8!d)
1sn8nv pue Xln[ Bu~inps Mon iaAu 4314 jo
s~eaXq 11p~a lela~io.i~~ Suoia~lse 'amepunqe
asoql u! alq!ssod Xluo s! uo!le18!ur 'sian!l aluos uoqo~~ uanbasqns pue '~uaun!n~las~se q
u~ .(+861 s!lle~)s la!lleq qms kq palmnsqo uegeasnv u! sqead 'd!qsuo!lela~ s!q~ JO
uaaq seq alqepehe Xlle!lualod q1Sua1 rueails asneJaa .Monluealls u! sasealau! IaIIelus lo
1elo1 a q J O jleq kla~em!xo~dd0e1 ssa3x pue Su!poog 01 asuodsai u! lnmo 'jlas~!i no!neqaq
'slay1 lelseo3 Xuew u! suo!lei8!lu lualul!nmal 8u!u~edsp ut! 'uo!1el8!m Bu!u~edss noluoip
pue 8u!u~eds pannilsqo aAeq ske~asne3 -eles aqL '(9861 s!lieH) ken pue kienuer
pue smup 'si!a~S u!pnpu! 'sia!iieq [e!sy!~iv uaa~laqI aIeM qsaij 01 a1e181lu sapuannr
. .
. .
. .
. . .
. . I-. . 1...
. .
. . . .
. . . .
.
. . . .
.
. . . .
.
.
. . . .
-
wa~sL maeb lseo3 lseo3
Bu!l~ea beunyy- W~OS quo^
years in which high flows drown-out barriers (1989) considers that its extinction is not
and, as a result, there are frequent gaps in the properly understood.
annual recruitment pattern.
2. Non-diadromous Fishes of Coastal
Table 4. The numlxrs of impoundments obrtrucring fish Drainages
passage (includes all types of dams and weirs) in large coastal
riven of New South Wales, plus the proportion of total a. Eastern Cod Maccullochella ikei
stream length upstream of major impoundments (from
Harris 1984). Until the early 1900s large populations of
this now-endangered species existed in the
Nunherof Per cent of
Clarence and Richmond River systems of
River svsrem im~oundment valley lenqth
northern New South Wales. The Eastern Cod
Richmond 23 14 is a large, long-lived, slow-growing species
Clarence i 11
with relatively low fecundity and a long
Hunter 18 29
Hawkerhury 82 49 generation period (Kowland 1993). In 1863
Shoalhaven 18 80 large numbers of fish up to 27 kg were caught
Snowy 9 16 in the Clarence River and its tributary, the
Orara River. A dramatic decline in abundance
occurred in the period to 1930, by which time
The mean age and size of bass in the the species was probably near extinction in the
Hawkesbury River system (Fig. 2) decreased Richmond River (Rowland 1993). In the
during a four-year study, despite a drought Richmond River the decline was associated
period when spawning was negligible (Harris with the construction of the north coast rail-
1988). The increased rate of total mortality way, which closely follows the river, and the
causing the observed decline in age and extensive dynamiting which occurred. River
size, was mainly attributed to fishing flooding and siltation were also implicated,
pressure. and the species disappeared from much of the
Clarence River system after a number of flood-
The effects of artificial barriers apply
similarly to some 26 diadromous fish species, related fish-kills during the 1920s and 1930s.
that is all of those migrating between fresh Again, the building of the railway was probably
a contributory factor but poor land-use
water and the estuarylsea at some specific
stage of their life-cycle, including the cata- practices, especially those leading to catchment
erosion and siltation, and damage to riparian
dromous, anadromous and amphidromous
vegetation corridors have also undoubtedly
groups (Harris 1984). These other affected
species include Congolli Pseudaph~itesu millii, contributed to loss of habitat for the cod. Like
the other three Australian freshwater cod
which appear to migrate downstream as
adults to spawn in weedy estuaries from late species, Eastern Cod is highly vulnerable to
fishing, and gross overfishing has been
April to August (Allen 1989), Freshwater
implicated in their declines. Regulatory
Herring Potomalosn richmondia, Striped Mullet
controls, including a total ban in the catching
Mugil cephalw and Freshwater Mullet Myxw
of Eastern Cod, have been imposed to protect
petardi.
this species in New South Wales.
b. Australian Grayling Prototroctes maraena
Small numbers of Eastern Cod were captured
The Australian Grayling, a threatened in the upper Clarence River, in pristine
species, is fecund (mean number of eggs habitat, during the 1980s for a species-
47 000) and lives for an estimated five years conservation project by New South Wales
(Bema 1982, 1987). Spawning is thought to Fisheries. Techniques for artificial breeding
occur in fresh water, the larvae then being were then developed at the Eastern Fresh-
swept downstream to the estuary and juvenile water Fish Research Hatchery and 29 000
fish migrating upstream four to six months juvenile Eastern Cod were released into the
later. Such a life-history is amphidromous, Clarence and Richmond River systems, and
i.e., those diadromous fish which migrate their survival is being monitored.
regularly at a particular stage of their life-cycle
but not for the purpose of spawning. The
3. Murray-Darling River Basin Species
Australian Grayling had only one congener,
the New Zealand Grayling P. oqrhyuchu~, a. Murray Cod Maccullochella peelii
which is now extinct. Although several
theories exist as to the causes of extinction The commercial fishery for Murray Cod
including habitat degradation, disease and declined from a peak in 1918. On the Murray
competition from alien species, McDowall River it is probable that, at lest until the 1930s
Australian Zoologist. Vol. 29(34J 169
Decline in ape of Hawkesbury baas
YO.1.
Figure 2. Ages of Bass taken in bass residential habitats of the Hawkesbury River system during the sampling period plotted
against lime. Where more than one data point falls in an individual plot area, the number is indicated by numerals (9 represenrs
nine or more) (n = 386) (From Hanis 1988).
and probably through recent years, the decline following inundation during floods. But the
of the cod fishery was largely caused by over- frequency, timing and duration of floods
fishing by both commercial and recreational has been considerably reduced by river regu-
fisheries (Rowland 1989). Although the lation by dams, weirs and abstractions so that
fishery was becoming uneconomic for large- the regular spring floods no longer occur
scale operators by the 1930s, catches of every year. Cod spawn in spring and early
Murray Cod in the period from 1940 to 1951 summer, and thus optimal conditions for the
represented 42-65 per cent of the entire spawning of Murray Cod now occur less
inland fishery (Figs 3 and 4). By 1955-56 the frequently than in the pre-regulation period
catch decreased further and today Murray Cod (Rowland 1988).
form only 10 per cent of the total freshwater
commercial catch (Rowland 1988; New South
Wales Fisheries Annual Reports). In 1928 there
were 1 300 commercial fishermen on the
Murray RiverIRiverina but by 1993 this number
had fallen to only 48 in New South Wales
(Grant 1993). Apart from over-exploitation by
commercial and recreational fisheries, a
decrease in spawning success due to river
regulation and general habitat degradation
has also reduced recruitment and survival of
the Murray Cod. Fish larvae are dependent
on the availability of zooplankton and other
small aquatic organisms such as insect larvae
Figure 3. Total annual catch per licensed fisherman per
for their early survival and growth. These
licensed boat from inland waters in New South Wales from
prey become abundant on the floodplain 1940 to 1981 (From Rowland 1989).
770 Australian Zoologist, Vo1. 29(3-4) December 7994
b. Silver Perch Bidjanm bidyanus food abundance) for life-history events,
inadequate flows for passage past obstacles, or
Silver Perch were once vely common in
excessive water velocities downstream of
most areas of the Murray-Darling River
irrigation storages. Similarly, poor water
system but this species is now formally
quality because of hypolimnetic (i.e., from
classified as "Potentially Threatened" (Jackson
deeper layers of dams) releases of cold,
1993). At Euston Weir on the Murray River
deoxygenated water, often containing
historical data (Mallen-Cooper and Brand
hydrogen sulphide and other toxic substances,
1992) show that during the period 194142,
and the modified flow regime, particularly
Silver Perch were the most abundant fish to
related to changes to the seasonality of flows
use the fishway. During that period, 11 526
and temperature regime of the natural
Silver Perch were captured with up to 450 fish
pattern are often associated with river
moving each day. In 1991 only 317 Silver Perch
regi~lationb y dams.
used the fishway and the maximurn catch was
38 in a day (Mallen-Cooper and Brand 1992). Water temperatures are usually severely
The data indicated a decline in the mean depressed downstream of impoundments which
annual abundance of Silver Perch of 93 per release cold, hypolimnetic water (Pollard el al.
cent of this 50-year period (Mallen-Cooper 1980; Llewellyn 1983; Wager and Jackson
1993). Over the same period, the frequency 1993) (Fig. 9). This has a severe effect on fish
of the small floods of 5 000-10 000 mllday, distribution and spawning. In the Macquarie
which stimulate migration, have declined by River below Burrendong Dam the effects of
about half (Close 1990; Mallen-Cooper 1992). this have only recently begun to be investigated
Silver Perch are thought to be flood-spawners (Hanis, NSW Fisheries, and Erskine, UNSW,
so reduction in the frequency of river flooding pers. comm. 1994). It has been found that
may lead to substantial reductions in recruit- irrigation water released during spring and
ment success. summer depresses water temperatures in the
river by at least 10"C, and depressed water
temperatures can be found downstream as far
REASONS FOR THE DECLINE as the river reach between Dubbo and Warren
(Swales 1994).
IN NATIVE FISH POPULATIONS
River regulation, water diversion and
River Regulation
abstraction (Fig. 5), have caused the Murray
River to become a series of connected pools
Not only the coastal species, but nearly all
with stable water levels. As a result the eco-
freshwater fish species in New South Wales
logical processes in the river have been grossly
need to migrate at some specific period in
altered (Walker and Thoms 1993). It has been
their life-cycle for breeding, recruitment
estimated that two-thirds of the flow of the
processes andlor redistribution. The more
Murray River is diverted to supply irrigation
obvious effect of dam and weir building is to
water for agricultural land (Fig. 6). Together
physically prevent such movement. Less
with this, floods are suppressed, and there is
obvious effects of river regulation include the
a phase shift (Fig. 7) in the seasonal flows and
loss of environmental cues (such as surges in
flood patterns (see section on Murray Cod).
Further downstream, near the South Austra-
lian border, the phase shift disappears
because of the extraction of irrigation supplies
but flow volume and variability are reduced
(Fig. 8).
Loss of Riparian Vegetation
The widespread loss or degradation of
riparian vegetation in most New South Wales
streams has many direct and indirect effects
on fish. These effects are mostly related to the
FIgur~4 . Percentage composition of Murray Cod (open
losses of shelter, or stream-bank stability and
circles), Golden Perch (solid circles) and Carp (solid line) in
the commercial catch from inland waters irr New South of the filtering effect of riparian buffer strips.
Wales from 1940 to 1981. Nore rhac the dramatic increase Chief amongst these are the loss of preferred
in Carp occurred well after the decline of Murray Cod (From habitat for many native fish, associated with
Rorvland 1989). The earlier reports of Carp in commercial
increased sunlight and temperature, increased
carches could possibly include some Goldfish Cnracrio
auratw. algal growth, increased predation, reduction
Australian Zoologist, Vol 29(34) 171
. .ll Gtructures in place .lI.tructures in place .Il.tNctur.. la pl.ce
. .t€ady uptEE p@l levela 6to.dt/ u[rIEr poo], I.val. etdely v.rytng (l@6 and levels
. flqctuling Levcl. larg€r level f luctuatl.onr Dy Ntr near b.nkf ull
d@3trear dmstrear tlr.n ln Scction I Ievel. .oetl.e6 .f (ected by
. {l@ velclty lncre.r€d flw and tlrtlclc velocLtle3 EC hl.dro olEratlons
. Frtlcle_ veLoclty Iittle ch.nged utor dLvcrrlon.
dccr6as€d lev€1. Ell bel@ bantfqll
. dlt.r dlvea.lon. th.n Dror dlveralons
uPstrqr
FloodtlE
all structures in place
. rc6t atnctures rercved fE@ lhe nirigation of flood p€aks
!lver to fEss floodvdters f lood inf loe hydrographs
. no rlrtg.tton of ftd tsdt. by preserwd dohstrean,
.tncturc. crce9t ar xcnind€€ .t Ddrt@uth &n
hta. .nd ljo*r bt€6. hyd.o oper.tions 6(fect
Figure 5. Summary of water level and flow behaviour of the Murray River (From Jacobs 1988).
in terrestrial food input and loss of spawning and may not become manifest for decades"
and nursery habitat (seeB unn et al. 1993). (Courtenay 1989).A s noted earlier, 16.9 per
cent of the New South Wales freshwater fish
fauna is alien to Australia, having been intro-
Catchment erosion
duced by people. These introductions have
Accelerated erosion of stream banks and almost invariably caused adverse effects on
river catchments has led to instream siltation native fish.
and the loss of suitable substratesf or spawn-
ing, shelter and food production. In most For example Carp Cyprinusc arpio have been
grazing areas stock (sheep and cattle) are in Australia for over 100 years but it is only in
allowed unlimited access to stream banks, the last 30 years that an illegal import of a
increasing erosion of banks, siltation and new strain caused their spread throughout
nutrients (cattle numbers in Australia south-east Australia (Morison and Hume
increasedf rom 3.9 million in 186l to 23.6 1989).A lthough they have becomea bundant
million in 1991,C astles1 993). in many areas,a study of Victorian populations
failed to prove that Carp causede nvironmental
The previously widespread practice of de-
damage.M orison and Hume (1989) concluded
snagging submerged timber from the river, to
that "the true extent of its undoubtedly
increase flow and navigation, also destroys
deleterious effect on the aquatic environment
fish habitats by changing habitat structure
remains open to speculation". New studies by
and the flow characteristicso f the river and
the Co-operative ResearchC entre for Fresh-
reducing sites for shelter, food-production
water Ecology, CSIRO and New South Wales
and spawning.
Fisheries ResearchI nstitute are being under-
taken to clarify the ecologicali mpacts of Carp,
Alien Species
and their extent and distribution in New South
"Any and every fish introduction will result Wales. Central to their possible ecological
in changest o the native biota, often negative, effects are the destruction of beds of aquatic
172 Australian Zoologist, Vol. 29(34) December 1994
(Lloyd 1989). Thirty-five fish speciesw orld-
- Nes South Hales wide have declined in abundance or range as
-- ___. vicloria (net oI a result of introductions of Gambusia (Lloyd
SouEh Ausrralia 1989).
+ Drt. not.wail.bl. Rowland (1989) suggestedt hat it is possible
. Rcrlrns not .wail.bl.
that Redfin Perch Percaf .uaia#/fs, introduced
from Europe last century, have contributed to
the decline of Murray Cod in the southern
sections of the Murray-Darling basin. As
Redfin Perch spawn in early spring, juveniles
may prey on Murray Cod larvae, and possibly
compete for food with them. Redfin Perch
o rzoo also caffy the epizooitic haematopoietic
necrosis( EHN) virus which is acutely virulent
o for a number of native fish speciesi ncluding the
"Potentially Threatened" species, Macquarie
v Perch Macquaria australasica.
A major threat facing New South Wales
TI waterways is Tilapia Oreochromism ossambicus,
a noxious species which its
,iv/tW i' -may ,expand
t' current range in central and southern
Queensland and move into the Murray-Darling
ii
basin or coastal waters in northern New South
L\^t
/+'\'r'7
r".-'' f
r925 rrlo l9l5 t9{0 r9{5 1950 r955
YEN
q9
Figure 6. Trend in state diversions of water from the River
Murray. Note the large increase of diversions after World
War II and also that New South Wales is the largest user of q;
water (From Jacobs 1990).
plants, marked increases in turbidity which
appear related to Carp feeding behaviour,
il
and re-suspensiono f nutrients associatedw ith
cyanobacterial blooms (Gehrke and Harris
1994). Figure 7. Flow at Albury. Natural (above Hume Dam, broken
line) versus existing conditions (below the dam, solid line).
Carp are now widespread and abundant Note the phase shift in seasonal flow patterns (From Jacobs
throughout most of the Murray-Darling basin 1988).
and in some coastal systems following their
introduction in about 1970.I n the New South
Wales inland commercial fishery after 1970
the proportion of Carp in the commercial
catch gradually increased until 1980-8l,
99
when they formed the majority of the catch
(Fig.a ). Fish samplingi n 1992a nd 1993u sing
fyke-nets and panel-nets at sites in the that
!t
Carp comprised 98.3 per cent and 91.9 per
cent respectivelyo f the total catch (P. Gehrke,
pers. comm.).
t\A
Gambusia Gambusia holbrooki (previously il wrw_\.1/ tV \,/ L/lJ\ Jl vJi\,J\/ \_J',ul
inaccurately titled "mosquito fish") have had rs/-3 rs74 r97s
profound effects on small aquatic fauna in Figure 8. Flow at Euston - Natural versus existing patterns
many parts of the world. The speciesi s very (GUMth). Note that at Euston the phase shift is no longer
present because of diversions from the river during summer
widely distributed in Australia and similar
and the influx of floods from tributaries mainly in winter
profound effects have been reported here (FromJacobs 1988).
December 1994 AustralianZ oologist, Vol. 29(34) 173
A Tallowa Dam A Eastern Cod M. ikei
V car^ Cv4rinu.s carbio V Australian Greyling Prototroctes maraena
Trout, mainly Brown Trout Salmo trutta and
Rainbow Trout Oncorhynchus mykiss, released
late last century, quickly became established
in suitable areas and have been implicated in
eliminating some Australian native species
such as galaxiids through competition and
predation (Crow1 et al. 1992; Tilzey 1976,
1977; Wager and Jackson 1993).
The impacts of other widely distributed
alien species, especially Goldfish Carassius
auratus, are not known but may contribute to
the general decline of native fish in New
South Wales.
REMEDIES
Ftgure 9. Temperature in the River Murray upstream and
downstream of Hume Dam. Because of decreased water The causes of the decline in fish abundance
temperatures below the dam, Golden Perch are absent from
and distribution are varied and often
the river downstream to Yarrawonga weir (From Mackay
and Shafron 1988). poorly documented (Mallen-Cooper 1993)
but research into fish habitat restoration
(Swales 1993) has started to redress some
Wales. This species can rapidly establish large, of the problems, in particular that of fish
dominant populations. Tilapia become sexually passage.
mature at 1-2 years old, grow to a maximum
Fish ways
size of 350 mm, and can form stunted popula-
tions in nutrient-poor waters (Bluhdorn et al. Fishways installed to aid fish attempting to
1990). migrate apast artificial barriers in New South
174 Australian Zoologist, Vol. 29(34) December 1994
Wales rivers were designed, before 1985, THE FUTURE
on European or North American models.
Depending on the cause of declining
Although suitable for salmonids, they were
abundance of the fish communities in each
largely ullsuitable for native species (Rlallen-
river system, separate strategies al-e necessary
Cooper 1993). In recent years better fishways,
for re-establishment. Research on restoring
especially the vertical-slot fishway design,
habitat has begun in several areas. There is
have been installed at locations on the
greatly increased emphasis on the need for
Nepean, Crawford, Murray and Maclntyre
suitable environmental floxvs in rivers, and
Rivers, on rveirs less than 6.5 m high. The
fish passage around and over barriers has
fishrvay at Torrumbarry on the Murray River,
improved considerably allowing fish to greatly
monitored since 1991, has so far been used by
extend their available habitat. Fishway designs
14 000 fish, including all sizes and species of
are potentially available to allow fish over high
mirating native fish. Currently, some of the
level dams and it remains to establish the
original ineffective lishways are being
benefit in each case to justify the large con-
modified to improve fish passage by fitting
struction costs. Similarly, eradication of alien
prefabricated inserts of improved fishway
species has been attempted at specific sites
designs. Several other modified designs have
and although often unsuccessful in achieving
been installed on existing weirs. A recent
total eradication (Burchmore et al.) can be of
experimental system for fish passage over low-
local benefit. Biological control methods are
level weirs (up to about 1 m high) involves a
feasible for control of even large-scale invasions
relatively low-cost solution, the rock-ramp
(such as Carp) but a potential for significant
fishway, in which a ramp of rocks is built from
community benefit must first be demonstrated
the weir crest downstream in a pool-riffle
(Harris 1994) as such methods are both costly
combination at a slope of 1:20. Several of
and require considerable trial and develop-
these are being built and evaluated around
ment times.
New South Wales. Another recently approved
type of fishway is the fishlock installed at
Yarrawonga Weir which is designed to
provide fish passage over a higher weir (10 m ACKNOWLEDGEMENTS
or more).
We would like to thank the Murray-Darling
Basin Commission for permission to use
several of the figures, and Dr Stuart Rowland
Restoring Fish Species and Communities for the Murray Cod material and figures.
Thanks to Drs Steven Swales and Peter
River rehabilitation and catchment improve-
Gehrke for helpful comments on the manu-
ment work have recently begun in New South
script.
Wales. This work includes limiting desnagging
operations in many rivers which remove sub-
merged logs, important as breeding and shelter
sites. Education of land-users to limit access to
REFERENCES
the river by livestock which cause erosion and
siltation in the rivers is also ongoing. Research Allen. G. R., 1989. Freshwnter firhes of ilrrrtraba. 'U.F.H.
Publications, 240 pp.
activities currently underway in New South
Wales Fisheries include studies of the distribu- Berra, T. M., 1987. Speculations un the evolutiun of life
tion and abundance of fish species, including histori tactics of the Australian srayling. Amer. Fish.
Symp. 1: 519-30.
threatened species (Eastern Cod, Trout Cod,
and Grayling). The development of successful Berra, T. M., 1982. Life history of the Australian grayling
breeding techniques for both Trout Cod and P~ololrocfesm urueno (Salmoniformes: Prorotrocridae) in
rhe Tarnbo Ri\,er, Victoria. Cnprio 1982: 795-805.
Eastern Cod has enabled re-establishment of
populations of these species in suitable areas. Bluhdorn, D. R., Arthingron, A. H. and Mather, P. B., 1990.
A major study commencing in 1994, will The introduced cichlid Oreochromis rnarsombicu in
Australia: A review ofdistribution, population genetics,
study the fish resources of New South Wales
ecology, management issues and research priorities.
rivers to better understand the health of the Pp. 83-92 in Inlroduced and Trnnrlocaled Fbhes and ihrir
rivers. The study will examine the status of Ecological Efeffeco ed by D. A. Pollard. P~ocredings.\ 'a. R
Bureau of Rural Resourcer. Bureau of Rural Resources:
fish resources, the effects of Carp and other
Canberra.
alien species, and the ecological effects of
river regulation. It will also establish and Bunn, S. E. Pusey, B. 1. and Price, P., 1993. Ecology and
test a standardized predictive model for management of riparian zones in Australia. Dlnd and
Water Resofrrces Occarionnl Paper No. 05/93, I ~ n d
monitoring river health using fish community
and Water Resources Research and Development
assessmenu. Corporation: Canberra.
Australian Zoologist, Vol 29(3-4) 175