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Rapid increases in native riverine fish populations associated with trophic upsurge immediately following reservoir construction are well documented. Repeated upsurge periods and extended benefits to populations are, however, less understood. We used sclerochronology to investigate fish growth and netting surveys to estimate recruitment and abundance of a lacustrine population of an Australian riverine fish, the Macquarie perch (Macquaria australasica) in Lake Dartmouth. Record low inflows from 1997 to 2008 caused the reservoir to shrink to its lowest volume since construction. Refilling began in 2008, reaching 99% capacity in 2013. We hypothesized that fish growth, recruitment, and abundance would increase in response to the refilling of the lake, reproducing a similar response to the initial filling period. Our findings supported this hypothesis. Macquarie perch growth, recruitment, and abundance were enhanced during the refilling of Lake Dartmouth. Growth, best explained by the effects of dam height, change in dam height, temperature (and their interactions), and recruitment, were highest during the first years of refilling when lake levels and temperatures were low. We propose one or a combination of varying levels of intraspecific competition (low during initial filling and high following population expansion) and improved riverine conditions for reproductive success as the most plausible explanation. Our results suggest extended periods of low lake levels followed by rapid inundation events are likely to enhance recruitment and population growth opportunities for this species. While reservoir construction in general impacts negatively on native fish populations, the potential to offset these impacts for conservation management purposes should be considered. Les augmentations rapides de populations de poissons de riviere indigenes associees a la poussee trophique qui suit immediatement la construction d'un reservoir sont bien documentees. La comprehension de periodes de poussee trophique successives et de leurs avantages pour les populations demeure toutefois plus limitee. Nous avons utilise la sclerochronologie pour etudier la croissance des poissons et des releves au filet pour estimer le recrutement et l'abondance d'une population lacustre d'un poisson de riviere australien, la perche de Macquarie (Macquaria australasica) dans le lac Dartmouth. Des debits entrants d'une faiblesse record de 1997 a 2008 ont fait diminuer le volume du reservoir jusqu'au point le plus bas enregistre depuis sa construction. Le nouveau remplissage a debute en 2008, pour atteindre 99% de la capacite du reservoir en 2013. Nous avons postule que la croissance, le recrutement et l'abondance des poissons augmenteraient en reponse a ce nouveau remplissage du lac, une reaction semblable a celle observee durant le remplissage initial. Nos constatations appuient cette hypothese. La croissance, le recrutement et l'abondance des perches de Macquarie ont augmente durant le nouveau remplissage du lac Dartmouth. La croissance, qu'expliquent le mieux les effets de la hauteur du barrage, des changements de cette hauteur et de la temperature (et leurs interactions), ainsi que le recrutement etaient a leur plus fort durant les premieres annees du nouveau remplissage, quand les niveaux et les temperatures du lac etaient faibles. Nous proposons que les variations du degre de concurrence intraspecifique (faible durant le remplissage initial, plus eleve apres l'expansion de la population) et (ou) l'amelioration des conditions fluviales necessaires au succes de reproduction constituent l'explication la plus plausible. Nos resultats donnent a penser que de longues periodes de faibles niveaux du lac suivies par des inondations rapides sont susceptibles d'accroitre les possibilites de recrutement et de croissance de la population pour cette espece. Si, en general, la construction de reservoirs a une incidence negative sur les populations de poissons indigenes, la compensation possible de ces impacts aux fins de gestion et de conservation devrait etre prise en consideration. [Traduit par la Redaction], Introduction The construction of large dams and subsequent creation of reservoirs has been a major driver of reductions in the range and abundance of native riverine fishes globally. The detrimental [...]

Abstract: Freshwater ecosystems and their associated biota are under increasing threats from multiple stressors including climate and land‐use change. The conservation of these ecosystems must be based on an integration of data including species physiological tolerances, the biotic and abiotic drivers of the distribution of populations, and demographic processes, to provide the comprehensive ecological information necessary for management. This study used a Bayesian belief network (BBN) to synthesize research on northern river blackfish, a threatened species in the upper Condamine River, Australia, into a probabilistic framework capable of predicting the complex relationships that exist between environmental conditions and population success. This study tested how predicted air temperature scenarios for the years 2050 and 2080, and catchment restoration scenarios, would be expected to affect three indices of population success: adult abundance, juvenile abundance, and juvenile recruitment. Compared with current climatic conditions, climate warming scenarios reduced the probability of future population success by between 0.4% and 1.6%. These shifts were almost completely offset, and even improved, when riparian zones were restored at the catchment scale, where changes ranged from an overall decrease of 0.2% to an increase of 1%. To achieve the highest probability of population success, the impacts of warming stream temperatures and the degradation of riparian zones must be mitigated. However, the model showed that there is still a possibility of complete population failure under a wide range of conditions, even when conditions appear to be suitable. To maximize the future population success of river blackfish we recommend targeting the restoration of hydrologically active catchment areas where grazing strongly influences stream biota. The use of a BBN allowed the combination of multiple sources of information to solve complex ecological problems, including how multiple stressors may affect threatened freshwater species. [ABSTRACT FROM AUTHOR]

The endorheic Lake Eyre Basin drains 1.2 million square kilometres of arid central Australia, yet provides habitat for only 30 species of freshwater fish due to the scarcity of water and extreme climate. The majority are hardy riverine species that are adapted to the unpredictable flow regimes, and capable of massive population booms following heavy rainfall and the restoration of connectivity between isolated waterholes. The remainder are endemic specialists from isolated springs with very restricted ranges, and many are listed under relevant state and national endangered species legislation and also by the International Union for Conservation of Nature (IUCN). For these spring communities, which are sustained by water from the Great Artesian Basin, survival is contingent on suitable habitat persisting alongside extractive mining, agriculture and the imposition of alien species. For the riverine species, which frequently undertake long migrations into ephemeral systems, preservation of the natural flow regime is paramount, as this reinstates riverine connectivity. In this study, fish were sampled from the Bulloo River in the east to the Mulligan River in the west, along a temporal timeframe and using a standard set of sampling gears. Fish presence was influenced by factors such as natural catchment divides, sampling time, ephemerality and the occurrence of connection flows and flooding. Despite the comparatively low diversity of species, the aquatic systems of this isolated region remain in good ecological condition, and as such they offer excellent opportunities to investigate the ecology of arid water systems. However, the presence of both endangered species (in the springs) and invasive and translocated species more widely indicates that active protection and management of this unique area is essential to maintain biodiversity and ecosystem integrity. [ABSTRACT FROM AUTHOR]

Eleotrid fish (gudgeons) commonly dominate the small-fish fauna throughout much of the Indo-Pacific region. Eleotrids frequently occupy habitats comprised of dense emergent macrophytes, making estimation offish abundance difficult. In this study, the suitability of unbaitedfish traps to measure carp gudgeon (Hypseieotris spp.) abundance in giant rush habitats was studied in a River Murray floodplain billabong using depletion trapping. Traps were repeatedly set at ten locations within giant rush beds over a two-day period. There was no significant variation in carp gudgeon catch rate over time within locations, but variation between locations was significant. It was not possible to deplete fish from any location over two days of trapping, suggesting rapid replacement of trapped fish in sampled locations. Patch specific variation in the gudgeon catch rate among different traps in macrophyte beds may reflect small-scale variation in habitat quality. [ABSTRACT FROM AUTHOR]