Mark Lintermans

Human‐assisted dispersal of alien freshwater fish in Australia

Abstract Approximately 34 alien fish species have established populations in Australian freshwaters with a further 53 native fish species translocated within the country. Twelve pathways of human‐assisted dispersal for freshwater fish have been identified in Australia, and each is discussed with examples given. The major pathway has been the aquarium or ornamental fish industry, with 22 of the 34 alien species originating from this source. Management actions to date have largely focused on eradication or mitigation, with little national or interstate coordination of efforts. Future management actions are suggested, with priorities being public and industry education and the development of coordinated strategies based on pest management principles.

Climate change and its implications for Australia's freshwater fish

Freshwater environments and their fishes are particularly vulnerable to climate change because the persistence and quality of aquatic habitat depend heavily on climatic and hydrologic regimes. In Australia, projections indicate that the rate and magnitude of climate change will vary across the continent. We review the likely effects of these changes on Australian freshwater fishes across geographic regions encompassing a diversity of habitats and climatic variability. Commonalities in the predicted implications of climate change on fish included habitat loss and fragmentation, surpassing of physiological tolerances and spread of alien species. Existing anthropogenic stressors in more developed regions are likely to compound these impacts because of the already reduced resilience of fish assemblages. Many Australian freshwater fish species are adapted to variable or unpredictable flow conditions and, in some cases, this evolutionary history may confer resistance or resilience to the impacts of climate change. However, the rate and magnitude of projected change will outpace the adaptive capacities of many species. Climate change therefore seriously threatens the persistence of many of Australia’s freshwater fish species, especially of those with limited ranges or specific habitat requirements, or of those that are already occurring close to physiological tolerance limits. Human responses to climate change should be proactive and focus on maintaining population resilience through the protection of habitat, mitigation of current anthropogenic stressors, adequate planning and provisioning of environmental flows and the consideration of more interventionist options such as managed translocations.

Recolonization by the mountain galaxias Galaxias olidus of a montane stream after the eradication of rainbow trout Oncorhynchus mykiss

The introduced salmonid Oncorhynchus mykiss was eradicated by use of the piscicide rotenone from a section of small montane stream upstream of an impassable barrier. Recolonization of the stream both above and below the barrier by the native Galaxias olidus was monitored annually for four successive years. Following trout eradication, G. olidus recolonized the trout-free stream section above the barrier but was never detected below the barrier where trout still occurred. Initial colonization was by juvenile G. olidus but a successful breeding population had established three years after trout eradication. The implications of the use of barriers and targeted eradication programmes are discussed for the management of small, threatened fish species.

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.

Identifying the influence of channel morphology on physical habitat availability for native fish: application to the two-spined blackfish (Gadopsis bispinosus) in the Cotter River, Australia

The impact of channel morphology and flow on physical habitat availability for the two-spined blackfish (Gadopsis bispinosus) was assessed in the Cotter River, ACT, Australia. Physical habitat requirements for three life stages were identified based on previous field sampling in the Cotter River. Two sites were selected with contrasting channel morphology: Spur Hole, with a moderate gradient and runs and glides, and Vanity’s Crossing, with a steeper gradient, rapids, and fast-flowing pools. Physical Habitat Simulation System (PHABSIM) was used to simulate the flow v. physical habitat availability relationship for each life stage at both sites. Clear differences were apparent between sites, with Spur Hole characterised by increasing habitat with increasing flow and Vanity’s Crossing showing the opposite relationship. The nature of the channel morphology determined this difference, with Spur Hole characterised by marginal zones becoming inundated at higher flows and providing additional suitable physical habitat as discharge increases. Vanity’s Crossing does not contain similar marginal zones. Further analysis demonstrated that high water velocity was the most important factor limiting physical habitat availability at both sites. This approach demonstrates the importance of channel morphology in determining physical habitat availability and an alternative use of PHABSIM to highlight limiting factors for target species.

Threatened Fishes of the World: Macquaria australasica Cuvier, 1830 (Percichthyidae)

Common names: Macquarie perch, white-eye, silver-eye, mountain perch, bream. Conservation status: Endangered (ANZECC 1999). Identification: D VIII–XII, I + 11–14, A III + 8–11, P 14–17, V I + 5, LL 42–60, gill rakers 17–21, vertebrae 28–31. Moderate-sized percoid fish (max. 460 mm, 3.5 kg), almost black or dark silvery grey to light or off-white silvery grey in colour, eye large, jaws equal (Harris & Rowland 1996). The species status is unresolved since investigations indicate that there are putatively two species (‘eastern’ and ‘western’) of Macquarie perch separated by the Great Dividing Range and possibly two sub-species within the ‘eastern’ species. Distribution: Formally widespread throughout the more southerly tributaries of the Murray-Darling River system of south-east Australia, as well as the Hawkesbury and Shoalhaven River systems on the eastern seaboard (Cadwallader 1981, Harris & Rowland 1996). Current distribution is fragmented and only small discrete populations remain. ‘Western’ populations are restricted to the upper reaches of some tributaries of the Murray-Darling River system, in particular, the Mitta Mitta River system above Darmouth Dam, the Goulburn, Murrumbidgee and Lachlan river systems, and one translocated population in the Yarra River. ‘Eastern’ populations are confined to the Shoalhaven and Hawkesbury river systems (Ingram et al. 1990, Harris & Rowland 1996). Abundance: No reliable population estimates exist for either the ‘eastern’ or ‘western’ forms. Habitat and ecology: Macquarie perch occupy a range of habitats from riffle and boulder areas in relatively small upland streams to larger deeper rivers with sand and clay substrates and submerged timber and snags as well as impounded waters. Their diet includes aquatic invertebrates, especially insects and crustaceans. Reproduction: Spawning, which occurs in shallow upland streams, is apparently triggered by increasing daylength and water temperatures and occurs in October to late December when temperatures range between 14◦C and 18◦C. Spawning Macquarie perch (‘western’ form) are oviparous and the demersal and slightly adhesive eggs (2.0–4.0 mm in diameter) appear to be shed into the water upstream of riffle areas. Hatching commences approximately five days after fertilisation and continues for up to six days (at water temperatures of 18–20◦C). Newly-hatched embryos are approximately 4.5–6.5 mm in length. Feeding commences on zooplankton about 3–5 days after hatching is completed (Gooley 1986, Ingram et al. 1994). Threats: A general degradation of the riverine environment caused by a number of contributing factors including modifications to rivers for hydro-electric, flood mitigation and irrigation schemes, increased pollution from domestic, agricultural and industrial sources, sedimentation, over-fishing, and impacts of introduced species, such as competition, predation and spread of disease (Cadwallader 1978, Ingram et al. 1990). Conservation action: Total bans on the capture of Macquarie perch exist in the Australian Capital Territory (ACT) and New South Wales (NSW). The capture, keeping and trading of Macquarie perch is controlled by legislation in Victoria. Captive breeding programs have been undertaken at government fish hatcheries in NSW and Victoria to produce and release juveniles of the ‘western’ form into selected sites within its former range to re-establish natural populations (Gooley 1986, Ingram et al. 1990). However, these programs have ceased due to difficulties associated with inducing spawning in both captive broodfish and mature fish in spawning condition captured from the wild. Between 1986 and 1997 approximately 456 000 juveniles were released into nine sites throughout the Murray-Darling basin. Early results indicate survival at some of these sites only. Attempts to re-establish populations of the ‘western’ form by translocation of mature fish have occurred in Victoria, New South Wales and the Australian Capital Territory (ACT Government 1999) with mixed success (Lintermans 2000). Conservation recommendations: Improve state and federal legislation to further protect Macquarie perch and preserve and rehabilitate riverine habitats where both existing and re-introduced (stocked) populations occur. Much basic biological information still needs to be collected for both ‘eastern’ and ‘western’ forms including resolution of species status, habitat requirements, life history patterns in the wild and surveys of existing populations to determine size, distribution and breeding status. Remarks: Since the status of Macquarie perch was upgraded to endangered, fisheries regulations have increased the level of protection from recreational fishing in Victoria, and a three year project has been instigated to investigate the Lake Dartmouth population.

A review of on-ground recovery actions for threatened freshwater fish in Australia

Freshwater fish are a highly threatened group and recovery of these threatened species is an increasingly difficult ecological and social challenge. There are many different on-ground recovery actions available to managers, but no synthesis of what, how or why these recovery actions have been deployed. The present paper reviews 428 reported on-ground recovery actions from a survey of practitioners of threatened freshwater-fish recovery in Australia. Recovery actions were grouped into 12 categories, with the most commonly utilised recovery categories being harvest control, translocation, habitat enhancement and stock enhancement. Major drivers of recovery actions were general conservation concern, recovery plans and emergency responses. The number of recovery actions grew significantly in the decade beginning 2000 as the impacts of prolonged drought in south-eastern Australia intensified. In all, 58% of recovery actions occurred in the Murray–Darling Basin, although this region holds only 27% of the 74 listed threatened freshwater fish in Australia. Few or no recovery actions were reported for many species, and few actions occurred in northern or western parts of the country. More than 80% of recovery actions reportedly had some form of monitoring. The diversity of management interventions is reviewed, and patterns and issues are identified to guide future recovery efforts.

A cautionary tale: surrogates for radio-tagging practice do not always simulate the responses of closely related species

Telemetry is useful for monitoring rare and threatened species if they can be effectively tagged. Relatively abundant, closely related species are sometimes used as surrogates in refining tagging methods or testing the suitability of methods before transfer to rare and threatened species. A decision framework for developing a radio-tagging method of an endangered fish (Macquaria australasica; Percichthyidae) is presented based on experiences with tagging a closely related, surrogate species (Macquaria ambigua). Aquaria and field-based trials demonstrated the suitability of internally implanting a radio-tag with an externally exited antenna on the surrogate species. However, transferring this method to the endangered species under field conditions was unsuccessful in terms of mortality and/or radio-tag rejection. In this case, a surrogate species served to refine radio-tagging methods, but did not successfully indicate the suitability of these methods for a closely related species. This cautionary tale illustrates that surrogate species are not always effective and extrapolation of methods, even across closely related species, may be perilous.

Radio-tagging and tracking of translocated trout cod (Maccullochella macquariensis: Percichthyidae) in an upland river

Radio-tracking provides an effective means of studying the spatial ecology of threatened fishes where almost inaccessible habitats and species rarity render conventional mark-recapture methods impractical. Initially, validation of an effective radio-tagging method is required; in the present study, an aquaria trial based on nine hatchery-reared, adult male Maccullochella maquariensis (Percichthyidae) was conducted. Fish resumed feeding within days of being internally implanted with a radio-tag, and tag rejection was not observed (0%, n = 9) based on a 2-month observational period. Following release into an upland stream, individual-specific movements resulted in upstream (n = 1) and downstream (n = 6) dispersal as well as fidelity to the release site (n = 2) at the completion of the study. Individuals established small home-ranges (mean length of river used by an individual per diel period ranged from 47 to 292 m) and were most active in the early morning and evening (n = 6). Complete survivorship of individuals bearing active radio-transmitters (n = 8) was recorded up until 4 months after release. However, an estimated zero or one individual was alive when the last active radio-tag expired 11 months after release (n = 8). The present study highlights the use of radio-tracking in monitoring the dispersal and survivorship of small numbers of hatchery-reared threatened fish released into natural habitats as part of species re-introduction programs.

Recovery of the endangered trout cod, Maccullochella macquariensis: what have we achieved in more than 25 years?

Recovery of threatened species is often necessarily a long-term process. The present paper details the progress towards the recovery of trout cod, Maccullochella macquariensis, an iconic, long-lived fish species first listed as threatened in the 1980s. The objectives, actions and progress over three successive national recovery plans (spanning 18 years) are assessed, documenting changes to population distribution and abundance and updating ecological knowledge. Increased knowledge (especially breeding biology and hatchery techniques, movements, habitats and genetics) has greatly influenced recovery actions and the use of a population model was developed to assist with management options and stocking regimes. Key recovery actions include stocking of hatchery-produced fish to establish new populations, regulations on angling (including closures), education (particularly identification from the closely related Murray cod, M. peelii) and habitat rehabilitation (especially re-instatement of structural woody habitats). In particular, the establishment of new populations using hatchery stocking has been a successful action. The importance of a coordinated long-term approach is emphasised and, although there is uncertainty in ongoing resourcing of the recovery program, much has been achieved and there is cautious optimism for the future of this species.