Tarmo A. Raadik

Alien salmonids in Australia: impediments to effective impact management, and future directions

Abstract Salmonids, mainly brown and rainbow trout (Salmo trutta and Oncorhynchus mykiss) were introduced into Australia in the mid 1860s and early 1890s respectively, and now support economically valuable recreational fisheries. These alien species have established self‐sustaining populations in many aquatic environments in south‐eastern and southwestern Australia, and stocking of hatchery‐produced or wild‐caught fish in larger systems is undertaken when fisheries targets are not met (e.g., fish numbers or appropriate size). Salmonids have established self‐maintaining populations in many waters not targeted or managed as fisheries, colonising the entire catchment in cooler upland areas of Australia. These populations usually comprise a high abundance of small fish in small first‐to‐third‐order tributaries. These waters are infrequently targeted by anglers, and populations may not contribute individuals to downstream fisheries. Negative impacts of alien salmonids on native aquatic fauna (including fish, frogs, spiny crayfish), mainly through direct predation and to a lesser degree competition for resources, have been noted for over 140 years. Impacts on some faunal groups have been severe enough to eliminate entire populations and severely fragment species across their range. Despite these impacts, salmonid management is focused largely on providing improved recreational angling opportunities, whereas management of their impacts is almost non‐existent. Management of the symptom of salmonid impacts, i.e., declining native species, begins only after native species have become imperilled. This paper focuses on impediments to effective management of salmonid impacts, existing and potential management or control options, and future directions and research needs.

Evidence of diadromous movements in a coastal population of southern smelts (Retropinninae: Retropinna) from Victoria, Australia

Understanding the migratory behaviour of fishes is critical to the conservation and management of fish assemblages in coastal rivers. We analysed the otolith chemical signatures of smelt, Retropinna sp., from inland and coastal populations in mainland south-eastern Australia to determine whether individuals within coastal populations of the species were diadromous. Assessments of otolith chemical composition combined with water chemistry data were used to make inferences about the migration histories of individual fish. A proportion of the smelt collected from the freshwater reaches of a coastal river exhibited diadromous movements, with the majority of fish analysed showing evidence of estuarine or marine occupation as larvae/juveniles and a minority inhabiting freshwater throughout their life histories. A broad range in the daily ages of upstream migration into freshwater (15-106 days) and the timing of these migrations suggest that spawning and migration occur over several months during the summer/autumn period. The results of this study suggest that southern smelts are an ecologically variable taxonomic group and that conservation and management actions should take into account the range of migratory behaviours exhibited both within populations and across regions.

Microsatellite markers and mtDNA data indicate two distinct groups in dwarf galaxias, Galaxiella pusilla (Mack) (Pisces: Galaxiidae), a threatened freshwater fish from south-eastern Australia

Galaxiella pusilla is a small, non-migratory freshwater fish, endemic to south-eastern Australia and considered nationally threatened. To assist in the conservation of the species, microsatellite markers were developed and used to characterize genetic variation in 20 geographically distinct populations across its range. Substantial genetic differentiation was found between an eastern (Victoria east of the Otway Ranges and Tasmania) and western (South Australia and Victoria west of, and including, the Otway Ranges) region. This major separation was also observed in data from a mitochondrial gene and supports a previously proposed split. Populations from the eastern region had overall lower genetic diversity for both the microsatellite and mtDNA markers. There was substantial genetic differentiation between populations within the two regions, suggesting that gene flow is limited by the isolation of freshwater streams. Genetic structure, consistent with an isolation-by-distance model, was also evident in both regions. Patterns of genetic variation in this threatened species are compared to those obtained for other taxa across the same region. The need to consider separate conservation strategies for the two sets of populations is emphasized.

Migration history and stock structure of two putatively diadromous teleost fishes, as determined by genetic and otolith chemistry analyses

Abstract: Migratory life cycles and population structure of 2 putatively diadromous Australian fishes were examined using otolith chemistry (87Sr/86Sr) and genetics (microsatellites and mitochondrial deoxyribonucleic acid [mtDNA]). Australian whitebait (Lovettia sealii) is widely considered to be one of only a few anadromous fish species in the southern hemisphere. The congolli or tupong (Pseudaphritis urvillii) is reported to undertake an unusual form of sexually segregated catadromous migration, where females switch habitats between marine and freshwater, while males remain in marine or estuarine environments. Sr-isotope profiles of L. sealii showed this species does not move into fully freshwater habitats during its life cycle, suggesting it should be considered semianadromous or estuarine-dependent, rather than truly anadromous. This life-history strategy is unique among the Galaxiidae. Lovettia sealii is regionally divided into at least 3 well differentiated genetic stocks: northern and southern Tasmanian coasts and mainland Australia. Sr-isotope profiles of P. urvillii showed that females are catadromous, with the early life history spent in the marine environment and a single migratory transition from marine to freshwater occurring at an early point in the life history. Lack of bidirectional adult migration between freshwater and the sea suggests that female P. urvillii are semelparous, returning to the marine habitat to mate with resident males after an extended period of freshwater residence. Pseudaphritis exhibit weak genetic structure across their mainland range. An isolation-by-distance relationship describes the genetic structure of this species, a pattern it shares with several other nearshore-restricted catadromous fishes.

Threatened fishes of the world:Galaxias fuscus Mack, 1936 (Galaxiidae)

Conservation status: Endangered ANZECC (supercedes CONCOM) list of endangered vertebrate species; CITES Schedule I; Australian Society for Fish Biology (Wager & Jackson 1993). Identification: A small (maximum 160 mm TL, 40 g), scaleless, orange-yellow salmoniform fish with up to 10 complete or partial black vertical ovoid bars on the flanks from just above the gill cover to just behind the pelvic fins; ventral surface creamy yellow. D 11 (9-12). A ll (lO-13) P 15-16 (14-17) V 7 (6-8) C 16 (15-17). Gill rakers on first arch 9-14. Head short and bulbous, body stocky, and caudal peduncle short and thick. Drawing by John Las Gourgues. Distribution: Described in 1936, and to date collected from a total of 16 streams (Raadik 1993, Raadik unpublished). Currently breeding populations occur in only 11 small streams located in three areas in the upper reaches of the Goulburn River system, central highlands area of the state of Victoria, south-eastern Australia (37” 08-37” 32’ S, 145” 20’-146” 33’ E). It appears that these populations represent the fragmentation of a previously much wider distribution. Abundance: Quantitative assessments of population abundance have been conducted at only four sites on four streams. Densities ranged from 0.11 to 0.17 fish m-* at sites with no salmonid predators (Raadik 1993) and from 0.003 to 0.027 fish m-* at sites with predators (Shirley 1991). No estimated total abundance data are available for each population. Habitat and ecology: Non-migratory and occur in cool, clear flowing, small (14 m wide) shallow streams with boulder, pebble, gravel and sand substrates, now restricted to above 500 m in altitude. No work has been conducted on diet though terrestrial insects may be an important component. Shirley (1991) suggested instream cover was important with preferred habitat being slow-flowing deep pools adjacent to areas of faster flow. Reproduction: Gonad development appears to begin as early as January (Raadik 1993) and spawning appears to be triggered by an increase in day length and water temperature (Shirley 1991) which occurs during late Winter-early Spring (August to October). Mean fecundity is approximately 500 eggs (mature ova) (n = 14), eggs are adhesive and large (unshed ova 2.2 mm diameter) and are thought to be demersal (Raadik 1993). Data on incubation time of eggs is unavailable, but young (12 mm TL) are present in the population by December (Raadik 1993). Spawning sites have not been located, though this species is possibly an opportunistic egg scatterer, utilising demersal cobbles and instream timber debris as well as gravel beds. Threats: The barred galaxias has undergone a serious decline over most of its range. Predation on both adults and juveniles by introduced Oncorhynchus mykiss and Salmo trutta is the major threat to the persistence of this species (Raadik 1993). To a lesser extent, competition between rainbow trout for limited space and resources, and habitat degradation associated with processes which damage aquatic systems, also pose a threat to this species. Conservation action: The capture, keeping and trading in barred galaxias is controlled by legislation in Victoria. A national recovery plan has been prepared for the species (Raadik 1993) and predator control and exclusion measures have been conducted on two populations, incorporating barrier construction and predator removal. On-going funding is available to include six more populations in this programme and to monitor effectiveness. Conservation recommendations: Further surveys should be conducted to locate additional extant populations, and research should be conducted into the biology and ecology of this species, though only after existing populations are made secure. Remarks: The implications of genetic isolation on the viability of existing populations also needs to be investigated and considered, as all populations can be regarded as being geographically isolated.

Fifteen from one: a revision of the Galaxias olidus Günther, 1866 complex (Teleostei, Galaxiidae) in south-eastern Australia recognises three previously described taxa and describes 12 new species

The systematics of the Galaxias olidus hyper-species complex from freshwater habitats in south-eastern, mainland Australia is revised. Galaxias olidus Günther 1866 is redescribed, Galaxias fuscus Mack 1936 and Galaxias ornatus Castelnau 1873, previously synonymised with G. olidus (sensu lato), are reinstated as valid taxa and redescribed, and 12 taxa are described as new: Galaxias aequipinnis sp. nov., Galaxias arcanus sp. nov., Galaxias brevissimus sp. nov., Galaxias gunaikurnai sp. nov., Galaxias lanceolatus sp. nov., Galaxias longifundus sp. nov., Galaxias mcdowalli sp. nov., Galaxias mungadhan sp. nov., Galaxias oliros sp. nov., Galaxias supremus sp. nov., Galaxias tantangara sp. nov., and Galaxias terenasus sp. nov. These species are morphologically similar and, whilst there is extensive overlap in meristic counts and morphometric characters, each can be diagnosed by unique combinations of characters, including allozyme loci and colour pattern; morphological diagnosis is improved greatly if based on freshly formalin-fixed material. Galaxias schomburgkii Peters 1868, Galaxias bongbong Macleay 1881, Galaxias kayi Ramsay & Ogilby 1886 and Galaxias oconnori Ogilby 1912 are retained as junior synonyms of G. olidus (sensu stricto). The types for Galaxias findlayi Macleay 1882 are lost and no specimens matching its description were collected or examined from the Mt. Kosciuszko region; it is also currently retained as a junior synonym of Galaxias olidus s.s. The species G. terenasus sp. nov. and G. arcanus sp. nov. are the most morphologically specialised in the complex and G. olidus s.s remains the most morphologically variable species. It also remains the most widespread taxon, though its previously known distribution is reduced, particularly in the south-west of its range. Nine species are narrow-range endemics, known from one, or only a few, locations, and these restricted distributions most probably reflect the fragmentation and reduction of former ranges caused by the effects of alien salmonids. Eleven species are of conservation concern, most are considered critically endangered.

Genome-wide SNPs resolve a key conflict between sequence and allozyme data to confirm another threatened candidate species of river blackfishes (Teleostei: Percichthyidae: Gadopsis)

Conflicting results from different molecular datasets have long confounded our ability to characterise species boundaries. Here we use genome-wide SNP data and an expanded allozyme dataset to resolve conflicting systematic hypotheses on an enigmatic group of fishes (Gadopsis, river blackfishes, Percichthyidae) restricted to southeastern Australia. Previous work based on three sets of molecular markers: mtDNA, nuclear intron DNA and 51 allozyme loci was unable to clearly resolve the status of a putative fifth candidate species (SWV) within Gadopsis marmoratus. Resolving the taxonomic status of candidate species SWV is particularly critical as based on IUCN criteria this taxon would be considered Critically Endangered. After all filtering steps we retained a subset of 10,862 putatively unlinked SNP loci for population genetic and phylogenomic analyses. Analyses of SNP loci based on maximum likelihood, fastSTRUCTURE and DAPC were all consistent with the previous and updated allozyme results supporting the validity of the candidate Gadopsis species SWV. Immediate conservation actions should focus on preventing take by anglers, protection of water resources to sustain perennial reaches and drought refuge pools, and aquatic and riparian habitat protection and improvement. In addition, a formal morphological taxonomic review of the genus Gadopsis is urgently required.

Threatened fishes of the world: Craterocephalus fluviatilis McCulloch, 1913 (Atherinidae)

Brendan Ebner, Tarmo Raadik & Walter Ivantsoff Cooperative Research Centre for Freshwater Ecology, Lower Basin Laboratory MDFRC, P.O. Box 3428, Mildura, Vic. 3502, Australia Current address: Wildlife Research and Monitoring, Environment ACT, P.O. Box 144, Lyneham, ACT 2602, Australia (e-mail: brendan.ebner@act.gov.au) Cooperative Research Centre for Freshwater Ecology, Freshwater Ecology, Arthur Rylah Institute for Environmental Research, P.O. Box 137, Heidelberg, Vic. 3084, Australia School of Biological Sciences, Macquarie University, NSW 2109, Australia

Is climate change driving recruitment failure in Australian bass Macquaria novemaculeata in southern latitudes of the species range

Flow regimes have been fundamentally altered in many of the world’s river systems. There is a need to restore components of natural flow variability to protect freshwater biodiversity. The Australian bass is a long-lived, catadromous percichthyid endemic to coastal drainages of south-eastern Australia. Little is known of the timing and magnitude of flows considered important for recruitment and growth of individuals in southern latitudes of the species range. Herein we generate nearly 50 years of otolith-derived recruitment and growth histories for Australian bass and relate these to hydrologic, climatic and demographic variables. We found that younger Australian bass grew fastest in years following a cooler spring, whereas the growth of older fish exhibited little response to temperature. Australian bass year class strength was positively related to high flows in spring and in a negative curvilinear way to spring temperature. A lack of suitable natural flows in spring may be responsible for little to no recruitment of Australian bass in the Genoa River over the past two decades. Based on our findings, the continuing trend of lower rainfall and higher temperatures, coupled with river regulation in some systems in the region, will likely result in depressed juvenile growth and prolonged periods of recruitment failure over the medium to longer term, with significant implications for the viability of populations.

Taking advantage of adaptations when managing threatened species within variable environments: the case of the dwarf galaxias, Galaxiella pusilla (Teleostei, Galaxiidae)

Native fish are threatened globally by invasive species, and management actions largely focus on detecting and eradicating invaders before they become established. However, once established, invaders might also be controlled by taking advantage of adaptations of threatened species to local conditions. This strategy was explored in dwarf galaxias (Galaxiella pusilla) a freshwater-dependent species of national conservation significance in Australia, threatened by invasive eastern gambusia (Gambusia holbrooki). Most habitats occupied by G. pusilla experience a seasonally variable and unpredictable hydrologic regime, where water levels substantially contract during dry periods and expand during wet periods. It was hypothesised that they are likely to have developed adaptations to surviving in these habitats by persisting without surface water. In contrast to G. holbrooki, we found that G. pusilla could withstand longer periods without surface water, including air breathing and higher respiration rates in air, than could G. holbrooki. We showed, within a single G. pusilla population, large inter-annual variability in fish densities linked to natural wetting and drying regimes. These findings indicate that periodic drying provides a way of protecting G. pusilla in water bodies where G. holbrooki has invaded, representing a strategy that takes advantage of local adaptation and metapopulation structure of G. pusilla.