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Understanding movement and habitat requirements of endangered species is critical to conservation management. We evaluate fine-scale acoustic telemetry to study breeding-related movement and habitat use of the endangered Mary River cod Maccullochella mariensis in a riverine environment and, in relation to key environmental variables, to inform management. Movement activity varied significantly in relation to water temperature and diel period, and spatial occupancy and habitat selection varied substantially in relation to the nesting behaviour of Mary River cod. Important nesting habitat included a large hollow log mid-channel and well-shaded logs and log jams adjacent to the river bank. Extrapolating this information to the general population was inhibited by relatively small sample sizes, due in part to the restricted spatial scale of the hydrophone arrays and longitudinal movements of tagged fish beyond the acoustic range of our array. Notwithstanding this, our results demonstrate that (1) fine-scale acoustic telemetry can quantify complex biological behaviours in riverine environments; (2) Mary River cod require specific environmental stimuli and habitat to support the reproductive cycle; and (3) changing environmental conditions may influence Mary River cod behaviour, and understanding this response is necessary for sustainable management. Findings from this study can inform future applications of this methodology in riverine environments and contribute to the development of management strategies and habitat restoration activities supporting the recovery of Mary River cod populations.

Context: Dryland rivers are unique ecosystems, where drought and flood play an important role in shaping the ecosystem. River regulation has altered the natural flow regime in many of these systems, affecting migration cues and connectivity for many species. Aims: To quantify the discharge-related movements of Murray cod and golden perch within the Condamine–Balonne River subject to differing levels of river regulation. Methods: We quantified flow regime variability, river regulation and fish movement to develop generalised additive mixed models to predict movement probability for Murray cod and golden perch. Results: Both species showed strong positive relationships between discharge and movement. Murray cod did not show any association with river regulation; however, medium-sized individuals were significantly more likely to move than were smaller or larger fish. Golden perch movements varied among levels of regulation, were more likely to move as body weight increased and showed seasonality of movement, moving less during winter. Conclusions: This study presents the largely unobserved movement behaviours of fish across a gradient of river regulation and environmental conditions in the northern Murray–Darling Basin. Implications: This information is valuable for informing policy and management decisions that may affect species' life-history requirements in analogous river systems. Quantifying flow-related movements of Murray cod and golden perch subject to differing levels of flow regulation is important for water management decision-making. Our study observed that movement patterns for either species were driven by combinations of discharge, river regulation, season, and body size. Tailored management strategies for these fish species should be developed on the basis of location, river regulation and flow regime. This article belongs to the collection Environmental Flows in Northern Murray–Darling Basin: what we know about the science and management after a decade of practice. [ABSTRACT FROM AUTHOR]

Aquatic macrophytes, especially Vallisneria nana, provide essential spawning habitat and food resources for the threatened Australian lungfish (Neoceratodus forsteri). The availability of V. nana for lungfish has been dramatically reduced in some areas due to flood disturbances and macrophyte recovery is inhibited by reduced hydrochory due to river fragmentation by dams. Active transplanting of macrophytes may be a feasible restoration strategy to increase abundance of macrophytes, however, in the presence of macro-herbivorous aquatic animals, replanted beds may not persist due to intensive grazing. In this study, we analyzed the effects of environmental conditions on growth and expansion of transplanted V. nana in six 60 m 2 herbivore exclosures in the mid-Brisbane River in subtropical south-east Queensland. Following establishment, we also quantified the impact of aquatic herbivores on different patch sizes (15 m 2 or 45 m 2 ) of restored V. nana to test the hypothesis that larger patch sizes may confer greater resistance to grazing using a paired control/treatment design. After initial planting, V. nana grew and spread rapidly throughout the exclosure plots, with mean % cover increasing from 5% to 71% on average and mean leaf length increasing from 20 cm to 54 cm on average over 161 days. Transplanted V. nana cover was significantly positively associated with water depth and finer substrate sizes and leaf length was significantly positively associated with water depth and water velocity but was unrelated to substrate size. Exposure to grazing significantly reduced cover of V. nana, however there was no significant effects of macrophyte patch size, grazing intensity, or environmental factors on changes in V. nana cover. Complete removal of exclosure fencing resulted in near complete loss of macrophytes within 7-22 days at all plots, indicating the macrophyte beds (15 m 2 -60 m 2 ) were of insufficient size to resist grazing pressure. Our findings suggest that transplanting is a viable restoration method with exclusion of grazing, which is critical for creating resistant beds to disturbances and driving future macrophyte recovery. Further research is required to evaluate the feasibility and efficacy of alternative macrophyte restoration strategies in rivers to foster hydrochory and natural regeneration processes following flood disturbance., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

The Yangtze River Basin, the world's third-largest river basin and a hot spot for global biodiversity conservation, is facing biodiversity crisis caused by reduced river connectivity. The deterioration arises from four dimensions: longitudinal, lateral, vertical and temporal. However, limited research has quantified the spatiotemporal connectivity of the Yangtze River Basin and further evaluated the consequent impact on fish biodiversity. In our study, a multi-index evaluation framework was developed to assess the variations in the four-dimensional connectivity of the Yangtze River Basin from 1980 to 2020, and fish biodiversity affected by reduced connectivity was detected by environmental DNA metabarcoding. Our results showed that the Yangtze River Basin suffers from a pronounced connectivity reduction, with 67% of assessed rivers experiencing deteriorated connectivity in recent years. The lost fish biodiversity along the river reaches with the worst connectivity was likely attributed to the construction of hydropower plants. The headwaters and the downstreams of most hydropower plants had a higher fish biodiversity compared with reservoirs. The free-flowing reaches in the downstream of the lowest hydropower station, had higher lotic fish abundance compared with that in the upstream. As for the entire Yangtze River Basin, 67% of threatened fish species, with 70% endemic species, were threatened by reduced river connectivity. Our result indicates that the massive loss of river connectivity changes the spatiotemporal patterns of fish community and threatens protected fish. More effective measures to restore the populations of affected fish in rivers with reduced river connectivity are required., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Despite providing considerable benefits to society, dams and weirs threaten riverine ecosystems by disrupting movement and migration of aquatic animals and degrading riverine habitats. Whilst the ecological impacts of large dams are well studied, the ecological effects of low-head weirs that are periodically drowned out by high flows are less well-understood. Here we examine the effects of a low-head weir on fine- and broad-scale movements, habitat use, and breeding behaviour of three species of native freshwater fish in the Nymboida River in coastal eastern Australia. Acoustic telemetry revealed that eastern freshwater cod (Maccullochella ikei) and eel-tailed catfish (Tandanus tandanus) made few large-scale movements, but Australian bass (Percalates novemaculeata) upstream of the weir were significantly more mobile than those below the weir. Within the weir pool, all three species displayed distinctive patterns in fine-scale movement behaviour that were likely related the deeper lentic environment created by the weir. No individuals of any species crossed the weir during the study period. Tandanus tandanus nesting behaviour varied greatly above and below the weir, where individuals in the more lentic upstream environment nested in potentially sub-optimal habitats. Our results demonstrate the potential effects of low-head weirs on movement and behaviour of freshwater fishes.

Ectothermic vertebrates face many challenges of thermoregulation. Many species rely on behavioral thermoregulation and move within their landscape to maintain homeostasis. Understanding the fine-scale nature of this regulation through tracking techniques can provide a better understanding of the relationships between such species and their dynamic environments. The use of animal tracking and telemetry technology has allowed the extensive collection of such data which has enabled us to better understand the ways animals move within their landscape. However, such technologies do not come without certain costs: they are generally invasive, relatively expensive, can be too heavy for small sized animals and unreliable in certain habitats. This study provides a cost-effective and non-invasive method through photo-identification, to determine fine scale movements of individuals. With our methodology, we have been able to find that male eastern water dragons (Intellagama leuseurii) have home ranges one and a half times larger than those of females. Furthermore, we found intraspecific differences in the size of home ranges depending on the time of the day. Lastly, we found that location mostly influenced females' home ranges, but not males and discuss why this may be so. Overall, we provide valuable information regarding the ecology of the eastern water dragon, but most importantly demonstrate that non-invasive photo-identification can be successfully applied to the study of reptiles.