ABSTRACT Native freshwater fish of Australia have a diverse but largely undescribed endemic pathogen and parasite fauna. However, due to long-shared evolutionary histories and virulence/transmissibility trade-offs, effects of these endemic pathogens and parasites appear to be subtle: significant impacts are rarely observed and epizootics have not been recorded. In contrast, a number of alien pathogens and parasites are now established across southern Australia, causing manifestly harmful effects to native fish species and known or suspected epizootics in native fish populations. Undetected and/or undescribed alien viral pathogens are also suspected of being present. Alien pathogens and parasites were introduced to Australia with imports of live alien fish or their fertilised eggs. A review of the scientific and historical evidence indicates that they have had, and continue to have, greater impacts on native fish species than previously realised—especially for freshwater species. This review also documents a previously unknown, Murray-Darling-Basin-wide epizootic of Murray cod Maccullochella peelii in 1929–30, which may have contributed to strong declines in the related eastern freshwater cod Maccullochella ikei . A serious Chilodonella epizootic of M. peelii in 1982 is also examined. In addition, a possible role for alien viruses of the family Iridoviridae ( Ranavirus and Megalocytivirus ) in the general decline of the critically endangered silver perch Bidyanus bidyanus , and the rapid collapse of two specific native fish populations—upper Murrumbidgee River B. bidyanus and Shoalhaven River Macquarie perch Macquaria australasica —is suggested. It is argued that the severity of the impact of the virulent alien oomycete Saprolegnia parasitica , both historical and present day, has been underestimated. Finally, action is recommended against emerging new pathogen and parasite threats, and the extreme risk current alien fish importations pose in introducing them. These will further threaten already stressed native fish populations in southern Australia, particularly across the Murray-Darling Basin.

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.

The use of small mesh size gill and drum nets in the inland fishery until around 1950 probably had a considerable impact on platypus populations in most New South Wales rivers. The prohibition of nets in the capture of introduced salmonid species by the Fisheries Act , 1902 and the current fishing regulations have provided a good deal of protection to the species in most water bodies of the State. However, it is probable that the present overlap of commercial (and illegal) fishing operations with the distribution of platypuses in the lower Murray and Murrumbidgee rivers, and their affluent streams, are suppressing platypus numbers. An experiment indicated that the legal drum nets used in the industry are less of a threat to platypuses than the use of gill nets and the illegal nets used by poachers. Banning of gill nets from the industry and stringent law enforcement would largely protect platypus populations in the inland rivers. The current regulations of the eel fishery in New South Wales should minimize the impact of this fishery on the platypus.

Length - weight relationships for 29 fish species occurring in the Murray-Darling River System in inland NSW were determined using data collected principally between 1957 and 1970. In Golden Perch Macquaria ambigua , this relationship is examined with regard to locality, year and sex. In the Murrumbidgee River large females were more rotund than males. In the Murray River fish caught in November appeared to be more rotund than those caught in September supporting an increase in ovary size to be expected at this time of year, and 1960 fish were more rotund than fish from 1963 and 1964 also reflecting time of year and river heights. Twenty one of the species were examined with regard to all fish and sex differences. The remaining eight were examined for all fish combined only. In most cases a single curve adequately describes the relationship for each species, except when the population includes large numbers of maturing females or when substantial sexual dimorphism occurs, such as in Philypnodon grandiceps and Mogurnda adspersa . The relationships provided support for using shape to sex some species.

The common stingaree, Trygonoptera testacea , is abundant on the continental shelf of eastern Australia but little is known of its ecology and reproduction despite it being a common component of the demersal trawl fishery. Specimens of T. testacea were collected from bycatch to investigate the species' reproductive biology. Males were found to mature at a disc width of 22 cm, while females reached sexual maturity at 26 cm disc width. Of all the T. testacea examined, 53% of males (n=159) and 16% of females (n=62) were sexually mature. Only the left uterus and ovary were found to be functional in female T. testacea. One gravid female carrying two near term embryos was sampled in February 2004. Many other females caught during the same trawl were observed aborting embryos providing a tentative estimate parturition period, which appears to be between the months of February and April. Although further investigation is required to determine if T. testacea populations are threatened by fishing pressures, the current study has provided key demographic parameters vital for the design of a management plan for T. testacea and similar populations.

The New South Wales South Western Slopes bioregion has been significantly altered by agricultural development and is likely to experience additional significant impacts as a result of anthropogenic climate change. A simple inventory survey of the vertebrate fauna of Currawananna State Forest, a small woodland remnant on the Murrumbidgee River in the south of the bioregion, over the period 2002-2010 identified 172 vertebrate fauna species. This included three species of national conservation concern (the Trout Cod Maccullochella macquariensis , Murray Cod Maccullochella peelii and Superb Parrot Polytelis swainsonii ) and another 16 species (5 fishes, 8 birds and 3 mammals) of state-level concern, as well as diverse frog, reptile, woodland and wetland bird and microchiropteran bat assemblages. This study demonstrates that even small remnants play an important role in supporting biodiversity in agricultural landscapes.

A tagging and recapture program was carried out between 1959 and 1970 on large freshwater fish species in the Murrumbidgee and Murray Rivers to determine the patterns of their movement. Tagging was carried out at four main sites Stoney Crossing, Hattah, Hay and Narrandera. At the time internal body tags were found to be the most reliable method of tagging. Adequate numbers of Golden Perch, Macquaria ambigua, and low numbers of Murray Cod Maccullochella peelii peelii and Silver Perch Bidyanus bidyanus were recaptured. It is concluded that up - and downstream movement of M. ambigua from these sites varied. The western two sites at Stoney Crossing and Hattah on the Murray River showed a marked net upstream movement; movement from Hay on the Murrumbidgee showed dispersal both up and downstream, while movement from Narrandera showed a net downstream movement. Within the size range sampled 309-563mm, the larger fish moved significantly less than the smaller fish; when split into upstream and downstream movement, this was only significant for upstream movement. B. Bidy anus, tagged in the upper two sites, showed a net downstream movement from Narrandera with a single upstream movement from Hay. M. peelii peelii showed only minor movements (up to 141 km) up and downstream from Narrandera, with only one long distance movement from Balranald to Gundagai. Net downstream stream movement of M. ambigua declined as one moved downstream closer to the mouth of the Murray River.

The piscicolid leech Austrobdella translucens was found on a single specimen of the eastern Australian salmon, Arripis trutta, and 22% of specimens of yellowfin whiting, Sillago schomburgkii , in Port Lincoln, South Australia between August-September 2004. In 2005, the number of yellowfin whiting parasitized by the leech increased to 71%. The appearance of this large, conspicuous ectoparasite is intriguing because it was thought to be an exclusive parasite of three closely-related species of inshore sillaginid fishes (the ‘sand whitings’, S. schomburgkii in Western Australia, S. analis in Queensland, and S. ciliata in Queensland and New South Wales), and also to be endemic to marine waters of tropical Australia (to as far south as the Shoalhaven River, south of Sydney). Up to 8 leeches were found on specimens of yellowfin whiting, covering most of the surface of their tail fins. Austrobdella translucens has been associated with mortalities of pond held whiting, and its appearance in temperate waters of South Australia on a non-sillaginid is potentially concerning because of the high concentration of cagebased finfish aquaculture. The taxonomy of leeches based on morphological features is difficult, and molecular analyses are needed to confirm the taxonomic affinity and origin of the piscicolid leech reported here.

A survey of fish species occurring in the marine waters of northern New South Wales was conducted at five sites between October 1988 and February 1996. The principal study site was at Julian Rocks, located approximately five km north of Cape Byron, Australia's most easterly mainland point. The other study sites included: Windarra Bank, located 16 km east of Mooball; Wilsons Reef, located 2 km south-west of Julian Rocks; Lennox Head Moat located at the southern extreme of Seven Mile Beach, Lennox Head and Belongil Creek, located two km west of Byron Bay township. A total of 530 fish species in 293 genera and 115 families was recorded from the study area. The total was composed of 394 (74.3%) tropical species, 103 (19.4%) temperate species and 31 (5.8%) subtropical species. The remaining two (0.4%) species have circum-global or circum-Australian distributions. Eighty-four (15.8%) of the species recorded are restricted to the South-Western or South Pacific Oceans and 96 (18.1%) are endemic to Australia. The endemics comprised: 19 (3.6%) tropical species; 48 (9.1%) temperate species; and 29 (5.5%) subtropical species. Two (0.4%) of the species recorded occur in both tropical and temperate seas and two species are primarily freshwater fish, one of which, Gambusia holbrooki (mosquito fish) is introduced. The 394 tropical species dominated the fish assemblage at the study sites. However, when the relative abundances of tropical, subtropical and temperate fish species are compared, the percentage of “common” tropical species (6.3%) was significantly less than the “common” subtropical (38.7%) or “common” temperate (19.4%) counterparts. The most speciose families were: Labridae (74 species); Pomacentridae (43); Chaetodontidae (26); Serranidae (24); Acanthuridae (19); Monacanthidae (16); Carangidae (16); Scorpaenidae (14); Pomacanthidae (13); Scombridae (13) and Tetraodontidae (13). A total of 114 (21.5%) tropical species in 31 families had not previously been recorded from New South Wales. Similarly, 12 (2.2%) temperate species in 10 families had not previously been recorded as far north as the study area.

G. rostratus the Murray Jollytail bred in earthen ponds at the Inland Fisheries Research Station, Narrandera, NSW, when surface and bottom water temperatures were above 10.5oC during August and September. Flooding was unnecessary but there was water flow through the pond. Eggs were demersal, transparent, spherical, telolecithal and slightly adhesive; possessed a cluster of oil globules; varied from 1.35mm to 1.66mm in diameter; and appeared to be scattered randomly on the pond bottom during spawning. Eggs hatched after 8½ to 9½ days. The length of recently-hatched larvae ranged from 5.7mm to 8.1mm. The pro-larval stage terminated at around 5days after hatching. Water temperatures varied between 13.8 and 20.0oC during development. The largest adults collected were 15.0cm and weighed 22.5gm. Marked colour differences between the sexes were not obvious, but sex could be determined by the appearance of gonads through the transparent window anterior to the vent close to the breeding season. Fecundity of the females varied from 2300 eggs at 86mm body length and 4.7gm body weight to 7000 eggs at 136mm length and 19gm weight. The gonosomatic index rose to 40.0 and 31.2 in females and males respectively prior to breeding. The breeding and larvae of G. rostratus are compared to other Australian mainland Galaxiidae, and other freshwater fish larvae of inland NSW.

The developmental ontogeny and morphology of the eggs, larvae and early juveniles of the endangered Nannoperca oxleyana is described based on collections of preserved wild fish, and preserved and live captive specimens reared at 25 ± 1° C. Eggs are telolecithal, spherical, average 1.02 ± 0.004 (± S.E.) mm in diameter, have a smooth, slightly adhesive chorion without filaments, a translucent homogeneous yolk, display meroblastic cell division and follow the general pattern of teleost embryogenesis. Early, middle and late stages of embryonic development were completed on average at 16, 28 and 50 hours post fertilisation. The larvae have generalised perciform morphological development with no apparent larval specialisations. The body is moderately deep bodied and compressed laterally. Head spination is limited to the development of an opercular spine in postflexion larvae. Pigmentation is relatively heavy and uniform over the head and body. Large melanophores occur on the dorsal, lateral and ventral midlines. Squamation commenced in postflexion larvae from 7.5 mm preserved body length (BL) and was complete in all specimens greater than 10.3 mm. Live captive, translucent larvae become pale green within two days of hatching and then light brown during the preflexion and postflexion stages. Juveniles are typically light brown laterally, darker dorsally and have a silvery-white belly. Growth of live, captive larvae and juveniles up to 6-months post hatching was described by the equation: Log10 live BL = 0.6043 + 0.0042A (r 2 = 0.917, P<0.00l, n = 323). Ranges for body length and age (days post hatch) of live captive fish were: preflexion 2.80-6.70 mm, 0-40 days; flexion: 6.35-7.70 mm, 21-61 days; postflexion: 6.40-10.30 mm, 43-118 days; and juveniles: 9.60-20.60 mm, 70-188 days. Live captive larvae commenced exogenous feeding at five days post hatching. Comparisons of N. oxleyana early developmental ontogeny and morphology are made with related percichthyids and sympatric species and implications for the conservation of the species are discussed.

Ambassis agassizii (Agassiz's Glassfish) collected from Barren Box Swamp was bred in ponds at the Narrandera Fisheries Centre on ten occasions between 1968 and 1971 when surface water temperatures were 19.0 - 27.0°C, between November and early January, and again in February. Breeding conditions and limited embryological development were determined. A single, demersal, transparent, spherical, telolecithal and slightly adhesive egg was collected on 9.xii.70 at 23.0°C. It possessed a single oil globule; and measured 0.61mm in diameter. Eggs hatched in about a day at temperatures between 20.0 and 29.0°C. The smallest larva collected was 2.59mm, and was about 1.6mm at hatching. The pro-larval stage terminated at under 10 days after hatching. The largest male and female adults were 60.0 and 68.0mm (TL) and 2.51 and 3.88g respectively. Egg counts were 380 to 9966 (mean 3257) with higher counts in larger fish. Ovaries generally had two size ranges of oocytes. Spawning was multiple. The GSI rose to 10.50 and 8.86 in females and males respectively. The breeding of A. agassizii was compared with the coastal population and some other ambassids, and some comparisons are made with other inland NSW species.

Wild Wet Tropics tandan Tandanus tropicanus were collected from the Bloomfield River, Queensland, for examination by histopathology and bacteriology. This provided an opportunity to establish baseline information on the general health and parasite fauna of native freshwater catfish in a pristine river. Histology of gill tissue revealed epitheliocystis in one fish. This is the first report of epitheliocystis in T. tropicanus . Bacterial culture showed light growth of bacteria from the kidney of only two fish, and these were identified as Aeromonas veronii , A. jandaei and Bacillus / Lactobacillus spp. An unidentified monogenean infection was observed in the gills of four fish, and trematode metacercariae were observed in the extra-ocular tissue of four fish. Nematodes were observed in the tissues of nine fish, and sequence and preliminary phylogenetic analysis of PCR products using an ITS primer suggest that these parasites may be a previously unreported Contracaecum species.

An intertidal rock pool at Seal Rocks, New South Wales, was repeatedly defaunated during summer or autumn between 1969 and 1987 using the ichthyocide rotenone. The fish assemblage was of moderate diversity, dominated by juveniles of subtidal species. Changes in the composition and numbers of species of this assemblage were assessed on both a long-term and short-term basis. The long-term study covered a period of 19 years; the short-term study was from March to May 1986. While considerable variation was observed in the numbers of the component species over the long-term collections, species composition remained relatively constant. In short-term studies recolonization of the area was initially rapid. Initial recolonization was dominated by intertidal species, such as Torquigener pleurogramrna , while subtidal species were more numerous in the long-term. This study is a preliminary observation of the fauna composition in one selected tide pool subjected to repeated defaunation.

The Central West and Lachlan Catchments lie west of the Great Dividing Range in central NSW and have been subjected to extensive land clearing, grazing and agricultural pressures beginning in the 1820s. Many vertebrate species are known to have disappeared from these catchments but reliable data for species diversity, distribution, abundance and conservation status are not available. For this assessment of the diversity and status of the vertebrate fauna in these catchment areas a comprehensive database of vertebrate records was established, species distributions mapped, faunal communities determined by pattern analysis and conservation status determined at a regional level. The extent of post-European human-induced landscape change was evaluated by assessing the degree of habitat loss, loss of landscape function and resilience through changes to the water cycle, soil and energy flow and the impact of invasive species, diseases and agricultural pollution. Of the 595 vertebrate species verified for these catchments, 6% are introduced, 12% have been listed in NSW under the Threatened Species Conservation Act 1995 , 4% by the Commonwealth Environment Protection and Biodiversity Conservation Act 1999 , 40% are regionally vulnerable, 20% regionally endangered and 2% likely to have become extinct in the region. Overall we estimate that 64% (382) of species are declining. These statistics present a grim picture of the survival of vertebrates in these catchments and potentially for the sheep-wheat belt of eastern Australia. The extreme loss of habitat and its poor condition across much of these catchments followed by serious changes to the functioning of the landscape provide clear reasons for the catastrophic decline of vertebrates in this landscape. If this serious decline in the Central West and Lachlan catchments is to be halted, strategies aimed at habitat and landscape restoration must be developed. Current strategies based on Threatened Species management plans and ad hoc planting for revegetation have not produced results. We need a radical rethink.

The Purple-spotted Gudgeon, Mogurnda adspersa , is widespread occurring in coastal drainages in northern NSW and Queensland, and an endangered western population in the Murray Darling System. This paper reports a study at the Inland Fisheries Research Station, Narrandera in the 1960s using fish from the western population. M. adspersa bred in ponds and aquaria at temperatures between 20.0 and 29.9oC (34.0oC at water surface), and in ponds between December and February. An abundant food supply was essential but rising water levels were not required. The elaborate spawning behaviour and embryological development of the eggs, larvae and juvenile fish were recorded. The eggs were demersal, transparent, telolecithal and elliptical, and they possessed an adhesive disc at one of the pointed ends, although the chorion was essentially non-adhesive. They measured 1.07 - 1.33mm by 2.03 - 3.78mm, and were attached in a cluster to solid objects. Their oil globules were small and numerous. The eggs hatched 3 – 8d after fertilisation, at temperatures of 20.2 - 29.0oC. The length of larvae at hatching varied from 3.44 - 4.15mm. The prolarval stage terminated approximately 61?2d after hatching at temperatures between 19.0 and 29.0°C, when the larvae measured 5.30 - 5.85mm in length. Opercular stripes appeared on juveniles between 12 and 20mm in length, and males and females were mature at 44.7 and 49.0mm respectively. Adult males often had a pronounced bulge on top of the head. The longest fish from the western population was 99.0mm. Fecundity varied from 284 to 1300 eggs. The gonosomatic index of females and males ranged from 1.26 - 11.74 and 0.18 - 2.16 respectively. The mean length of fish reared in an aquarium measured 33.0 and 50.0mm at one and two years old, respectively. Eggs, larvae, and breeding biology are compared with other Murray Darling species. The breeding biology of Mogurnda species in Australia is discussed which emphasises the taxonomic confusion.

Several species of the Australo-Papuan genus Mixophyes (barred frogs) have declined markedly and are now considered threatened. During field investigations into the possible causes of declines, we observed oviposition and numerous egg masses (700+) of the four species from southeast Australia. From these and published observations there are two markedly different ovipositional processes within Mixophyes . In M. coggeri, M. fasciolatus and M. iteratus eggs are laid in water then deposited terrestrially, propelled from the foot of the floating female onto a near-vertical or overhanging stream bank (Ovipositional Process 1). In M. balbus and M. fleayi eggs are deposited aquatically in the shallow riffle zones of small streams, either into a rounded nest depression in the substrate (Ovipositional Process 2A), or occasionally directly onto bedrock (Ovipositional Process 2B). These observations of ovipositing and egg masses show that there are three reproductive modes in the genus: mode 2 - eggs and exotrophic tadpoles in lotic water ( M. fleayi ), mode 4 - eggs and early larval stages in constructed basins, exotrophic tadpoles in streams subsequent to flooding – ( M. balbus and M. fleayi ), and mode 18 (terrestrial eggs above water, exotrophic hatchlings move to water ( M. carbinensis , M. coggeri, M. fasciolatus, M. iteratus and M. schevilli ). Mixophyes fasciolatus was the only species to use both lentic as well as lotic waters for larval development. For the Australian species amplexus was axillary, occasionally shifting during the process of oviposition to inguinal. Amplexus for the New Guinean M. hihihorlo , is unknown, as is the ovipositional process and reproductive mode. The phylogenetic significance of our observations is that Mixophyes species have non-foamy egg masses, which accords with their recent placement in the family Myobatrachidae. However, no other members of this family show either of the described processes of oviposition, and furthermore we observed amplexus in Mixophyes to be axillary whereas all other reports for myobatrachids are of inguinal amplexus. Our findings have consequences for management of the habitat of barred frogs, three of which are considered threatened. The construction of creek crossings (for vehicles, bikes, horse riding, pedestrians) in riffle zones, the trampling of creek banks by cattle, horses, pigs and humans and changes to the hydrology of creeks by damming or regulating flows that alter the connection between hydrology and stream bank structures, are all likely to have a negative impact on reproductive success.