Impacts of fishing, river flow and connectivity loss on the conservation of a migratory fish population

Abstract

1. Migratory species depend on connected habitats and appropriate migratory cues to complete their life cycles. Diadromous fish exemplify species with migratory life cycles by moving between connected freshwater and saltwater habitats to reproduce. However, migration increases the exposure of fish to multiple threats and it is critical that managers integrate habitat connectivity into resource management and conservation.2. The benefit of alternative management actions was assessed for a diadromous fish, the Australian bass Percalates novemaculeata, using a spatio-temporal population model informed by individual-based movement data. The management actions comprise seasonal closures during the spawning season, and controlling fishing pressure by limiting catch or effort.3. The benefits of implementing seasonal closures depend upon interactions among how fishing pressure is controlled, the response of anglers to fishery regulations and river flow regimes.The results indicated that seasonal closures are ineffective if fishing pressure is merely displaced to another location or time of year. In addition, shifting seasonal closures from spawning grounds to feeding grounds increased population abundances under low flow events when fishing effort was also controlled. However, when total annual catch is limited by a fishery closure, changing the location of seasonal closure schemes had little effect.4. The findings in this study highlight the need for flexible management strategies that account for migratory movements and respond both to variations in connectivity (e.g. river flow regime) and direct pressures on survivorship (e.g. exploitation). As the implementation of one management action (e.g. fishing or water regulation) could affect the influence of another management action, this study emphasizes the importance of cooperation between resource managers in conserving migratory species.

The role of connectivity in conservation planning for species with obligatory interactions: Prospects for future climate scenarios

“…From a conservation perspective, the long‐term persistence of these species could be at high risk: even if we manage to cover their last strongholds, they will be less connected and therefore subject to the effects of declining genetic diversity and stochastic natural events that may increase the extinction risk. Accordingly, it is widely recognized that habitat connectivity should be taken into account when selecting priority areas, both in freshwaters (Bush et al., 2014; Hermoso et al., 2018; Hermoso, Clavero, & Filipe, 2021; Hermoso & Filipe, 2021; Hermoso, Vasconcelos, et al., 2021; Lin et al., 2018; Naia et al., 2021), and in other realms (Alagador et al., 2016; Magris et al., 2014, 2016; Triviño et al., 2018).…”

Effective monitoring of freshwater fish

“…However, attaching tracking devices or marking fish, prior to release, can substantially increase the amount of information obtained. For example, biotelemetry using acoustic, radio or passive integrated transponder tags (Cooke, Woodley, Brad Eppard, Brown, & Nielsen, ; Thiem, Taylor, McConnachie, Binder, & Cooke, ) can reveal individual variability in movements and behaviours within and between populations (Lucas & Batley, ; Radinger & Wolter, ), elucidate population mixing and gene flow (Huey, Schmidt, Balcombe, Marshall, & Hughes, ), assess the effects of connectivity and habitat fragmentation on river fishes (Capra et al, ; Lin et al, ), and help evaluate management units for fisheries or conservation (Funk, McKay, Hohenlohe, & Allendorf, ).…”

Toward process‐based conservation prioritizations for freshwater ecosystems

“…Identifying adequate conservation targets in this complex scenario requires a deeper understanding of the ecology of the species. Steps to parameterize these problems have been taken by Lin, Bush, Linke, Possingham, and Brown () and Lin et al (), who quantified the effects of flow regulation, fishing pressure, and connectivity loss by barriers, as well as climate change, on two Australian fish species, and the targets needed for their persistence. An alternative, easier solution is to treat multiple populations as separate evolutionarily significant units and use these as pseudospecies in complementarity‐based algorithms.…”