Search

Aim Changing preferences regarding which species humans have transported to new regions can have major consequences for the potential distribution of alien taxa, but the mechanisms shaping these patterns are poorly understood. We assessed the extent to which changes in human preferences for transporting and introducing alien freshwater fishes have altered their biogeography. Location Australia. Methods We compiled an up‐to‐date database of alien freshwater fishes established in drainages in Australia before and after the number of established alien fish species doubled (pre‐1970 and post‐1970, respectively). Using metacommunity models, we analysed the influence of species traits and drainage features on the distribution of alien fishes that established pre‐ and post‐1970. Results Alien fishes in Australia were introduced via four main transport pathways: acclimatization, aquaculture, biocontrol and ornamental trade. The relative importance of each pathway changed substantially between the two periods, accompanied by changes in the distribution of alien fishes and the variables predicting their distribution. Pre‐1970, most species (64%) were introduced by acclimatization societies for purposes such as angling and biocontrol, and these fish have established in inland drainages more heavily impacted by human activities. In contrast, most of the post‐1970 introductions (69%) were ornamental fishes, with most species established in small, north‐eastern, tropical and subtropical coastal drainages. Main conclusions Substantial changes in introduction preferences and transport pathways over time have altered both the patterns and underlying processes shaping the biogeography of alien fishes in Australia. Our findings highlight the need for caution when using historical data to infer potential future distributions of alien species. The continuing spread of alien species means traditional biogeographical units may no longer be identifiable in the foreseeable future.

Este artículo contiene 16 páginas, 6 figuras, 5 tablas., Non-native fish invasions threaten native fauna and ecosystem functioning, not least in isolated island lakes. In Tasmania, where the native fish are mostly galaxiids, 9 non-native freshwater fish species have been introduced over the past 150 years, with uncertain ecological outcomes. We evaluated the effects of non-native predatory fishes (NNPF) and various environmental and biological variables on the trophic niche of native fish (galaxiids) and potential cascading effects. We analysed Layman’s food web metrics based on both stable isotope (δ15N and δ13C) values and fish stomach contents in 14 shallow Tasmanian lakes along a NNPF abundance gradient. The food web metrics calculated were (1) range of δ13C (CR) and δ15N (NR) centroid distance (CD) and (2) standard ellipse area. Our results showed that NNPF relative abundance in the fish catch per unit effort was negatively related to the galaxiids’ trophic niche metrics (e.g., CRG, NR G, and CDG), trophic position, and the pelagic contribution to the diet. Moreover, the proportion of galaxiids in the diet of NNPF was higher in turbid lakes. The zooplankton standard ellipse area was negatively correlated with the pelagic contribution to the NNPF diet, and NNPF relative abundance was positively correlated with the maximum body size of calanoid copepods. While our results suggest a negative effect of NNPF on the trophic niche of galaxiids, the cascading effect on phytoplankton biomass was weak. Non-native predatory fish affect native fish prey, and the outcome of these interactions should be considered for conservation purposes, particularly for island lakes, such as those in Tasmania., The project was funded by Galathea 3, Carlsberg, Research Council of Nature and Universe (272-08-0406), the TK Foundation, Dronning Margrethes og Prins Henriks Fond, Torben og AliceFrimodts Fond, Christian og Ottila Brorsons Rejselegat, University of Copenhagen and Aarhus University. MM and NV were funded by SNI-ANII and the L’Oréal UNESCO Women for Science national award with support of DICYT, Uruguay. MV was supported by a Marie Curie post-doctoral grant (MEIF-CT-2005-010554) and TB by a Beatriu de Pinós post-doctoral grant (2005 BP-A 1004). EJ was supported by the MARS project (Managing Aquatic Ecosystems and Water Resources Under Multiple Stress) funded under the EU 7th Framework Programme, Theme 6 (Environment including Climate Change), Contract No.: 603378 (http://www.mars-project.eu), CIRCE and CRES. LAB was supported by the Australian Research Council (LP130100756). CT is a CONICET (Argentinean Council of Science) researcher; Fondation L’Oréal; Sistema Nacional de Investigadores (UY).

Flagship species, especially mammals and birds, are commonly used to increase awareness of conservation issues in marine and terrestrial ecosystems. However, flagship species oriented programs are often ad hoc with initiatives scarce in the freshwater context. Here, we aim to identify potential flagship candidates that would appeal to a broad cross section of society at a continental scale where freshwater ecosystems are under threat from human impacts. We identified 19 species from a list of 299 Australian freshwater fishes on the basis of body size, trophic guild and threatened species status assuming these characteristics of flagship species are transferable from previous work on terrestrial flagship species. We considered the potential of species to be of international appeal but focused mostly on eight relevant interest groups within Australia. This followed the rationale that public engagement with conservation issues in freshwater systems might be more effective if the link between fish species and the decisions people make were better understood, and we acknowledge the diverging interests of stakeholders. This scoping work contributes towards addressing the challenges of connecting societies to the principles of sharing water resources with ecosystems, and represents the first continental-scale assessment of its kind.

In comparison with other habitats, the littoral zone can be disproportionately important to lentic fishes, especially for species that rely on it for reproduction. Impoundment of lentic waters can alter hydrological regimes, littoral inundation patterns and hydrodynamic processes, which can affect the quantity and quality of littoral habitats. This study examined the effects of water-level fluctuations on the quantity and quality of rocky littoral spawning habitat for the threatened Galaxias auratus in the Crescent–Sorell lake system, Tasmania (Australia) using GIS analyses, sediment measurements and observations of the composition and condition of littoral substrates under varying hydrological conditions. The extent of littoral rocky substrate was found to be limited in Lake Crescent (

The scientific basis for setting environmental flows is still hampered by our incomplete understanding of flow–ecology relationships and how river ecology varies with flow regime. We conducted a study of six rivers in Tasmania (Australia), three perennial and three intermittent, measuring a range of abiotic, biotic and ecosystem process attributes over 2 years. Our intentions were to identify: (i) whether they had an ecology characteristic of their flow regime and (ii) whether certain ecological attributes were more responsive to flow regime than others, and therefore represented candidate indicators (for environmental flows or flow alteration) specific to each flow regime. Only a few abiotic variables showed any relationship with flow regime: banks were higher, pools shallower and sediments finer in perennial rivers, and water temperature was generally lower in perennial rivers. Although rarely measured, we found that productivity and net ecosystem metabolism were strongly related to flow regime, whereas food chain length did not vary between perennial and intermittent rivers. Multivariate, rather than univariate, metrics of biotic assemblages were more effective at distinguishing perennial and intermittent flow regimes, and this was consistent among riparian and instream vegetation, biofilm and macroinvertebrate assemblages. In contrast to expectations from the literature, fish assemblages were not strong indicators of flow regime, largely due to the relatively low diversity and abundance of the Tasmanian fish fauna. Our findings demonstrate that rivers with different flow regimes can support a distinctive ecology, and conventional metrics of ecological character may not be the most sensitive to flow regime. We provide a set of ecological attributes that can: (i) support extrapolation of flow–ecology relationships across rivers to regional scales, (ii) provide benchmarks for environmental flow and flow restoration objectives, (iii) indicate alterations to natural or existing flow regimes and (iv) be used to monitor and evaluate flow management actions.

Defining the ecological impacts of water extraction from free-flowing river systems in altered landscapes is challenging as multiple stressors (e.g., flow regime alteration, increased sedimentation) may have simultaneous effects and attributing causality is problematic. This multiple-stressor context has been acknowledged in environmental flows science, but is often neglected when it comes to examining flow-ecology relationships, and setting and implementing environmental flows. We examined the impacts of land and water use on rivers in the upper Ringarooma River catchment in Tasmania (south-east Australia), which contains intensively irrigated agriculture, to support implementation of a water management plan. Temporal and spatial and trends in river condition were assessed using benthic macroinvertebrates as bioindicators. Relationships between macroinvertebrate community structure and environmental variables were examined using univariate and multivariate analyses, focusing on the impacts of agricultural land use and water use. Structural changes in macroinvertebrate communities in rivers in the catchment indicated temporal and spatial declines in the ecological condition of some stretches of river associated with agricultural land and water use. Moreover, water extraction appeared to exacerbate impairment associated with agricultural land use (e.g., reduced macroinvertebrate density, more flow-avoiding taxa). The findings of our catchment-specific bioassessments will underpin decision-making during the implementation of the Ringarooma water management plan, and highlight the need to consider compounding impacts of land and water use in environmental flows and water planning in agricultural landscapes.

Golden galaxias Galaxias auratus (31-235 mm fork length, LF) were collected monthly from littoral habitats in Lakes Crescent and Sorell, Tasmania, Australia, between July 2000 and December 2002. Spawning habitats were identified and monitored in both lakes, and surveyed in Lake Crescent. Trends in gonado-somatic indices and reproductive stages of development indicated that gonad development in both sexes begins in midsummer and peaks in late autumn to early winter. Males mature at smaller sizes (50% at 52 mm LF) than females (50% at 76 mm LF), larger individuals are predominately females (95% of fish ≥138 mm LF), and overall male to female ratios are female biased (c. 1:2). Spawning occurs late autumn to early spring (water temperatures = 1.4-9.7°C) with peaks in spawning activity in winter (mean water temperatures

The occurrence of golden galaxias Galaxias auratus with dermal fungal lesions in two populations was effectively modelled by the progression of gonadal stages of development. Skin lesions were found to be characteristic of fungal dermatitis and a Saprolegnia sp. was identified as the causative agent. Infection is probably linked to spawning-related factors and it is probable that saprolegniasis is associated with seasonal mortality.

The littoral zone of small off-stream water storage containing a translocated population of Galaxias auratus was sampled fortnightly at day and night with fyke nets, electrofishing and snorkelling over 3 months. Variation in population data provided by each method, including relative abundance indices, size structure, and habitat preferences, were examined. Aspects of behaviour and activity patterns were also investigated. Night sampling using all methods consistently yielded larger catches than day sampling. The size structure of catches varied, with electrofishing at night and fyke netting during the day having higher proportions of juveniles, whilst snorkelling at night and electrofishing during the day had higher proportions of adults. Fyke netting at night yielded by far the largest catches (~3-fold more than other methods) and also captured balanced proportions of juveniles and adults. Galaxias auratus had a strong diel activity pattern and were most active at night. The majority of the population migrated into the littoral zone during the night and back into deeper water during the day. A small number of juveniles remained in the littoral zone and some adults sheltered in the dense cover of species-rich littoral vegetation during the day. Shores with shallow depth profiles appeared to be preferred due to higher catches in these areas using all methods. Based on the results of this study, fyke netting at night in littoral habitats is recommended for monitoring populations of G. auratus. Fyke netting is likely to be an effective method for monitoring other lacustrine galaxiid species; however, further work is required to investigate the effects of habitat variables and fish community structure on activity patterns of galaxiids, and hence their catchability with various methods, in more extensive lentic environments.

1. Fish of the family Galaxiidae are restricted to the southern hemisphere where they occupy a diverse array of habitats ranging from over 2000m in elevation to sea level. Some species are diadromous and, hence, freshwater, estuarine and marine habitats are used during their life-cycle; other species complete their entire life-cycles in freshwater environments. 2. Tasmania has a diverse galaxiid fauna that accounts for 64% of native freshwater fish species found on the island. The Tasmanian galaxiid fauna is characterized by high species richness (5 genera and 16 species), endemism (11 species), restricted distributions, and non-diadromous life histories (11 species). 3. The galaxiid fauna of Tasmania has significant conservation status with 69% of species considered ‘threatened’. The conservation status of the fauna is recognized at State, national and international levels. 4. The key threats to galaxiids in Tasmania are exotic species, hydrological manipulations, restricted distributions, general habitat degradation and exploitation of stocks. 5. Although work has recently been undertaken to conserve and manage Tasmanian galaxiid populations, the fauna is still thought to be imperilled. Knowledge gaps that need to be addressed include the biology and ecology of most species (e.g. reproductive biology, life histories, habitat use and requirements) and impacts of habitat manipulations, as well as mechanisms and impacts of interactions with exotic species. Techniques to monitor accurately the status of galaxiid species and their populations need to be developed and the coexistence of some galaxiids with introduced salmonids should also be examined.

Fishes belonging to the family Galaxiidae are relatively small (usually

Hydrological alterations threaten freshwater fishes globally, with infrastructure-related modification of inland waterways (e.g. dams, water diversions) having profound impacts on many species. Adapting existing water-management systems can provide opportunities for undertaking hydrological manipulations to assist management of threatened fishes. The present study conducted two hydrological manipulations in an impounded highland lake system in Tasmania, Australia, under differing hydrological conditions in 2007 and 2009, to assist recovery of an endemic species, Galaxias auratus, following a prolonged drought. Monitoring at egg, larvae, juvenile and adult life stages revealed a positive response by G. auratus in Lake Crescent (recipient of water release), with no adverse impact on the species in Lake Sorell (source of water release). In both years, reproductive constraints imposed by water level-related availability of sediment-free rocky substrata delayed spawning (~1 month) of G. auratus in Lake Crescent. Despite this, spawning and recruitment occurred in 2007 (drought year) and 2009 (drought-breaking year), and the 2007 manipulation resulted in a two-fold increase in the seasonal density of larvae in Lake Crescent and an abundant cohort of YOY fish. Given knowledge of life histories and eco-hydrological relationships, manipulating (or re-instating) hydrologic conditions is a powerful tool for assisting recovery of threatened lacustrine fishes.

Common name: Golden galaxias. Conservation status: Rare – (Tasmanian Threatened Species Protection Act 1995); Endangered – ASFB (2003). Identification: D 7–10, A 11–12, P 14–18, vertebral count 53–56 (McDowall & Frankenberg 1981). Small scaleless salmoniform fish, maximum size: 240 mm TFL, 130 g (Hardie 2003). Colouration: golden to olive-green on dorsal surface and sides, silvery-grey on ventral surface. Back and sides are covered with round to oval black spots (McDowall & Frankenberg 1981). Drawing by Carol Kroger in Fulton (1990).