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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]

Catadromous fish species often use elevated flows to migrate from freshwater to downstream spawning grounds. However, in regulated river systems, artificial barriers and flow alteration can disrupt movement cues, affecting fish migration. Using a combination of acoustic telemetry, passive integrated transponder (PIT) tags and gonad maturity data, we assessed the migratory timing and flow requirements for downstream spawning migrations and upstream dispersal in two co-occurring mullet species in the Logan River, eastern Australia. Over 4 years, 141 adult sea mullet (Mugil cephalus) and 28 adult pinkeye mullet (Trachystoma petardi) were implanted with acoustic transmitters and broad-scale movements tracked using an array of 49 acoustic receivers. Juvenile upstream dispersal was monitored using implanted PIT tags and readers deployed in weir fishways. Sea mullet and pinkeye mullet undertook large-scale downstream migrations from February to March. Movements past weirs only occurred once sufficient flow had occurred and, in the case of pinkeye mullet, when gonads were mature. In contrast, juvenile dispersal into upstream habitats occurred primarily between November and April on low flows. This study advances our understanding of bidirectional movement ecology and flow requirements of two co-occurring mullet species to inform environmental flow management (e.g. to facilitate fish passage) in a regulated river system. We investigated the timing and flow requirements for downstream spawning migrations and upstream dispersal of sea mullet and pinkeye mullet in a regulated river using a combination of acoustic telemetry, passive integrated transponder tags and gonad maturity assessment. Both species undertook downstream spawning migrations from February to March on high-flow events, which enabled passage over large weirs. Juvenile upstream dispersal occurred from November to April mostly during low flows. [ABSTRACT FROM AUTHOR]

Catadromous fish species require adequate flows to migrate between fresh and saltwater habitats to reproduce. However, artificial barriers and flow alteration affect fish populations by reducing habitat connectivity and disrupting movement cues. In regulated rivers, it is critical that migratory flow requirements are quantified to optimise water allocation for multiple users. In the present study, we assessed the migratory timing, flow and estuarine aggregation requirements for Australian bass (Percalates novemaculeata). Over 2 years, 66 bass were tracked using an acoustic receiver array in the Logan River (Qld, Australia). Bass performed large-scale downstream movements in response to elevated winter flows (40 and 108m³ s-1), which facilitated migration to the lower estuary, where salinity conditions were appropriate for spawning. Bass migrations occurred only when gonads were mature, despite large flows providing opportunities for movement outside this period. Experimental flow releases from an impoundment (2.1 m³ s-1) during winter did not elicit a migratory response. Connectivity between upstream and estuarine habitats was reduced by the presence of instream weirs, with downstream movement across weirs occurring only when sufficient flow magnitude was achieved (.76.1 m³ s-1). These findings are relevant for water resource managers formulating environmental flow rules for catadromous fish species in systems with multiple instream artificial barriers. [ABSTRACT FROM AUTHOR]