Academic literature on the topic 'Mountain galaxias'

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.

Patterns of feeding in the mountain galaxiid (Galaxias olidus) were examined at dawn and dusk during low flow in April and high flow in September in an intermittent stream. During April (low flow), feeding rates were relatively low and aperiodic, whereas in September (high flow), the fish were clearly feeding diurnally at a relatively high rate. These results suggest that feeding in G. olidus in intermittent streams may vary on a daily and seasonal basis, possibly as a consequence of changes in light availability and stream flow. Light determines the ability of fish to find their prey, and seasonal changes in flow may determine the availability of prey (i.e. drifting invertebrates). This pattern suggests that the predatory impact of drift-feeding fish, such as G. olidus, is likely to be considerably less during low-flow periods when drifting invertebrates are not available than during high-flow periods when such prey may be abundant.

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.

The Tasmanian Wilderness World Heritage Area encompasses an area of 1.38 million hectares, or approximately 20% of the island state of Tasmania. The World Heritage Area plays a significant role in the conservation of Tasmania's fauna and natural biological processes. The area supports 30 species of terrestrial mammal including three endemic species (91% of total Tasmanian species), 120 species of terrestrial bird including 10 endemic species (76% of state total), 14 species of terrestrial reptile including seven endemic species (67% of state total), seven species of frog including three endemic species (64% of state total), 16 species of freshwater fish including four endemic species (64% of state total), and 68 species of marine fish including one endemic species (14% of state total). A number of vertebrate species are entirely restricted to the World Heritage Area (Moss Froglet, Pedra Branca Skink, Mountain Skink, Pedder Galaxias, Swamp Galaxias and Western Paragalaxias, while the migratory Orange-bellied Parrot breeds only within the World Heritage Area. A number of other species have the majority of their Tasmanian range within the World Heritage Area (Broad-toothed Rat, Ground Parrot, Southern Emu-wren, Tasmanian Tree Frog, Northern Snow Skink, Southern Snow Skink, Bathurst Harbour Skate and the Clarence Galaxias). The World Heritage Area also supports a range of threatened mammal, bird, reptile and fish species. Of the 44 species of introduced vertebrates which have established feral populations in Tasmania, only seven species (16% of state total) have a significant presence within the World Heritage Area and pose a potential threat to the area's integrity. The diversity and endemism of the vertebrate fauna of the World Heritage Area reflects the Gondwanan origins of much of the fauna of western Tasmania, the repeated glaciation of the area during the Pleistocene, and subsequent pulses of speciation among certain taxa.

Regionalisations based on species assemblages are a useful framework for characterising ecological communities and revealing patterns in the environment. In the present study, multivariate analyses are used to discern large-scale patterns in fish assemblages in the Murray–Darling Basin, based on information from the Murray–Darling Basin Authority’s first Sustainable Rivers Audit (SRA), conducted in 2004–2007. The Basin is classified into nine regions with similar historical fish assemblages (i.e. without major human intervention), using data that combine expert opinion, museum collections and historical records. These regions are (1) Darling Basin Plains, (2) Northern Uplands, (3) Murray Basin Plains, (4) Northern Alps, (5) Central East, (6) Avoca Lowland, (7) Southern Slopes, (8) Southern Alps and (9) South-Western Slopes. Associations between assemblages and physical variables (catchment area, elevation, hydrology, precipitation, temperature) are identified and used to reinforce the definitions of regions. Sustainable Rivers Audit data are compared with the historical assemblages, highlighting species whose range and abundance have changed since the early 19th century. Notable changes include declines in native species such as silver perch, river blackfish, mountain galaxias, Macquarie perch, trout cod and freshwater catfish, and the advent of alien species including common carp, eastern gambusia, goldfish, redfin perch, brown trout and rainbow trout. Less significant declines are evident for native carp gudgeons, golden perch, two-spined blackfish, bony herring and flathead gudgeon. Changes are evident even in regions where habitats have been little disturbed in the past 200 years.

AbstractGalaxy nuclei are a unique laboratory to study gas flows. Their high-resolution imaging in galactic nuclei are instrumental in the study of the fueling and feedback of star formation and nuclear activity in nearby galaxies. Several fueling mechanisms can now be confronted in detail with observations done with state-of-the-art interferometers. Furthermore, the study of gas flows in galactic nuclei can probe the feedback of activity on the interstellar medium of galaxies. Feedback action from star formation and AGN activity is invoked to prevent galaxies from becoming overly massive, but also to explain scaling laws like black hole (BH)-bulge mass correlations and the bimodal color distribution of galaxies. This close relationship between galaxies and their central supermassive BH can be described as co-evolution. There is mounting observational evidence for the existence of gas outflows in different populations of starbursts and active galaxies, a manifestation of the feedback of activity. We summarize the main results recently obtained from the observation of galactic inflows and outflows in a variety of active galaxies with current millimeter interferometers such as ALMA or the IRAM array.

There is now mounting evidence that the intrinsic shape of elliptical galaxies and bulges of disk galaxies may generally be triaxial. There are different signatures of non–axisymmetric structures observed: velocity gradients along the minor axis (e.g. Davies & Birkinshaw 1986), twisting of the isophotes (e.g. Williams & Schwarzschild 1979) and misalignment between bulge and disk major axes (e.g. Bertola, Vietri & Zeilinger 1991). Therefore, a framework of reliable algorithms for the dynamical modelling of such triaxial potentials is needed.

Six rivers within the upper Mumbidgee catchment were sampled for larval and juvenile fish. The rivers represented both regulated and unregulated flow regimes and varied widely in size. There was wide variation in the larval fish communities supported by each river, both in terms of the species diversity and total abundance of fish sampled. The highly regulated reach of the Mumbidgee River sampled during this study had the highest numbers of native species and native individuals of any river sampled. In the two rivers selected for further study, the Murmmbidgee and Goodradigbee, there was a high level of inter-annual consistency in the species composition within the reaches sampled, despite considerable change in the temperature and flow regimes of both rivers. This indicates that at least some spawning of those species sampled may occur each year, regardless of environmental conditions. Estimates of the relative abundance of each species sampled changed markedly between years, and it is argued, on the basis of growth information contained in the otoliths, that differential survival of larvae and juveniles was largely responsible for this shift in relative abundance. Otolith microstructure provided information on the date of spawning and early growth patterns of all species sampled in the upper Mumumbidgee catchment. In addition to determining the age and thus 'birth-date' of an individual, the effect of a particular event or series of events has on growth, and subsequent survival, is permanently recorded in the otolith microstructure. This enables accurate back-calculation and correlation to management actions or natural events. No other research tool has this ability to retrospectively assess, on a daily basis, the impacts of management actions on condition and subsequent survival of fish larvae. Species sampled could be separated into three groups based on spawning requirements; those linked with flow, those linked with temperature and generalist species that appear to have river independent cues, such as photoperiod or moon phase. Patterns in growth rate during the early life history stages enabled quantification of the consequences of variation in environmental conditions on the survival and recruitment of various species. Growth was not always highly correlated with water temperature, in fact, for mountain galaxias, high temperatures appear to negatively affect larval condition and subsequent survival. Conversely, carp exhibited a strategy more consistent with common perceptions, with growth and survival increasing with increasing temperature. The study uncovered spawning and growth patterns that were unexpected. Age analysis of western carp gudgeon demonstrated that they had undertaken a mid-winter spawning, when the water temperature in the main channel was far lower than that at which spawning was previously recorded for this species. Redfin perch from the unregulated Goodradigbee River exhibited growth rates exceeding the published upper limits for this and other closely related species. This growth could not be correlated with either temperature or flow, indicating that there are additional factors that dominate growth rates of redfin perch in the Goodradigbee River. The proportion and abundance of native species alone is not necessarily indicative of a 'healthy' or pristine system; some native species may be positively affected by river regulation, at least as juveniles. Comparison of the current larval fish community with likely pre-European fish communities does provide an indication of change to the system. The results of this study suggest that larval fish growth rates can be strongly influenced by environmental conditions, thus providing a powerful tool for monitoring future change and the factors which cause it. This study has demonstrated the value of larval and juvenile fish age and growth information, derived from otolith microstructure techniques, for many aspects of river management. Current river management priorities for which these techniques provide unique information include the determination of environmental flow regimes and the control of undesirable exotic species such as carp.

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