Take the long way home: Minimal recovery in a K-selected freshwater crayfish impacted by significant population loss

Whiterod, Nick S.; Zukowski, Sylvia; Asmus, Martin; Todd, Charles R.; Gwinn, Daniel C.

doi:10.1016/j.ecolind.2018.02.042

Cited by 16 publications

(15 citation statements)

References 59 publications

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“…As hypothesised, the abundance of Macquarie perch showed an increasing trend in the years following the millennium drought, with population increases in most waterways not evident until 2−3 yr after drought conditions had subsided. Considering that our abundance estimates included fish ≥1 yr of age, the recovery rates of adult fish, which reach full maturation at 3+ yr (Appleford et al 1998), is likely to extend well beyond this time frame, with such gradual rates of recovery adhering to K-selected nature of the species (Hutchings et al 2012, Whiterod et al 2018. Of course the true extent of the impacts of the drought, and subsequent progress towards recovery, remain unknown, which unfortunately requires population data that preceded any impacts by the disturbance (e.g.…”

Section: Discussionmentioning

confidence: 99%

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Climate variability regulates population dynamics of a threatened freshwater fish

Tonkin¹,

Sharley²,

Fanson³

et al. 2019

Endang. Species. Res.

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Section: Discussionmentioning

confidence: 99%

“…Pavlova et al 2017) and/or Allee effects (Courchamp et al 2008), or if existing management practices such as fishery regulations are inadequate (e.g. Whiterod et al 2018). Whilst the rates of decline in the Yarra River did not appear to exceed those in the other study waterways, the latter pathway impairing recovery is plausible.…”

Section: Discussionmentioning

confidence: 99%

Climate variability regulates population dynamics of a threatened freshwater fish

Tonkin¹,

Sharley²,

Fanson³

et al. 2019

Endang. Species. Res.

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“…The influence of climate change on flow could be assessed, along with impacts of altered thermal regimes on different life stages ( sensu Todd, Ryan, Nicol, & Bearlin, ), as well as other threats to life history such as pollution, sedimentation, and eutrophication. Importantly, given the documented declines across its range, the model can be used to assess trajectories of recovery (McCusker, Curtis, Lovejoy, & Mandrak, ; Whiterod et al, ), as well as to explore management strategies, including translocations, which may be needed to restore degraded populations.…”

Section: Discussionmentioning

confidence: 99%

“…The model represents the best knowledge available, accounting for regional variation in biology, on the impacts on both male and female populations resulting from recreational fishing regulations and allowing for catastrophic population declines caused by hypoxic disturbance. Collaboration has been a feature of the recent management of the E. armatus recreational fishery, with the engagement of recreational fishers and conservation managers (Zukowski et al, ), and with research conducted both on environmental disturbances (McCarthy et al, ; Noble & Fulton, ; Whiterod et al, ) and on the impacts associated with harvest (Zukowski et al, , ) helping to inform a review of fishery regulations. The outcomes of population modelling have been conveyed to fishery managers and recreational fishers (e.g.…”

Section: Discussionmentioning

confidence: 99%

“…Euastacus armatus is now threatened across much of its range and, despite some threats having ceased (commercial harvesting and removal of females), populations continue to decline (Alves, Coughran, Furse, & Lawler, ). For instance, recent significant losses have been documented in some upland populations (Noble & Fulton, ), and in large lowland sections of the Murrumbidgee River (M. Asmus, unpublished data) and the Murray River (King, Tonkin, & Lieshcke, ; 81% decline in abundance, McCarthy et al, ; Whiterod, Zukowski, Asmus, Todd, & Gwinn, ), with the latter resulting from extreme hypoxic blackwater disturbance during 2010–11 (Whitworth, Baldwin, & Kerr, ).…”

Section: Introductionmentioning

confidence: 99%

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Integrating fishing and conservation in a risk framework: A stochastic population model to guide the proactive management of a threatened freshwater crayfish

Todd

Whiterod

Raymond

et al. 2018

Aquatic Conservation

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Numerous freshwater species are recreationally harvested, yet conservation concerns are often ignored. This may lead to conflict between fisheries and conservation management for a species. Approximately one‐third of freshwater crayfish species globally are threatened with extinction, including the Murray crayfish, Euastacus armatus (von Martens, 1866) in south‐eastern Australia. There has been substantial commercial and recreational fishing of E. armatus since European settlement, as well as other threats such as poor water quality (e.g. hypoxic ‘blackwater events’ during floods). A stochastic population model was developed for three regional populations of male and female E. armatus, and was used to examine the effects of fishing and hypoxic blackwater disturbance on a Murray crayfish population in a lowland region. The results indicate that the Murray crayfish population in the lowland region faces increasing risks from increasing fishing pressure, together with low frequencies of hypoxic blackwater disturbance only. Testing various fishery regulations, the modelling demonstrated that recent changes to the ‘slot size’ in occipital carapace length of 10–12 cm for legally harvesting crayfish was a suitable protection measure given the background levels of hypoxic blackwater disturbance, balancing fishing and conservation concerns. Although higher slots (11–13 cm and 12–14 cm) were less sensitive to higher fishing pressures, the recreational harvest declined. The model was most sensitive to early life‐history survival rates; however, sensitivity analysis of model variability also indicated that E. armatus may be susceptible to highly variable environments (not to be confused with highly variable flows). This study demonstrates the successful integration of fishing and conservation in a flexible risk framework for this threatened freshwater crayfish species; furthermore, fisher expectation can be managed by assessing the impact on harvest of potential changes to fishing regulations. This approach is easily transferable and would improve the management of other recreationally fished species facing multiple threats.

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A population model provides support for management decisions, enables ongoing research and reinforces strong partnerships to manage a threatened freshwater crayfish

Whiterod¹,

Todd

Zukowski³

et al. 2020

Aquatic Conservation

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Many freshwater crayfish are threatened with extinction owing to varied threats such as urban development, pollution, over‐harvest, and climate change, as well as invasive species. A recently published manuscript in Aquatic Conservation: Marine and Freshwater Ecosystems described a stochastic, age‐based population model for the large freshwater crayfish Murray crayfish, Euastacus armatus, which is now threatened across much of its range in the Murray–Darling Basin in south‐eastern Australia. The model was constructed for three regional populations using the best available knowledge of life‐history traits such as longevity, size at onset of sexual maturity, fecundity, and survival, along with an account of density dependence. The model provides a framework to explore aspects of the conservation and management of the species, including assessing the influence of recreational harvest and environmental disturbance such as hypoxic blackwater, which affected the species significantly in 2010–2011. The application of the model provided retrospective justification for regulation amendments and highlighted biologically realistic timeframes for the recovery of impaired populations. This knowledge has assisted multi‐jurisdictional fisheries management agencies to undertake routine reviews of fishery regulations, as well as to inform stakeholders of the benefits of the regulation amendments. Refinement of the modelling framework has already provided additional insight and it is anticipated that future application will help to address other important management questions. The modelling outcomes are at present informing conservation assessment of the species under the Australian Government's Environmental Protection and Biodiversity Conservation Act 1999. The benefit of the population model can be summarized as: providing a framework to inform and justify management decisions; enabling additional research; and guiding conservation assessment. This has strengthened strong partnerships (between ecologists, managers, and recreational fishers) required to manage the species effectively.

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Take the long way home: Minimal recovery in a K-selected freshwater crayfish impacted by significant population loss

Cited by 16 publications

References 59 publications

Climate variability regulates population dynamics of a threatened freshwater fish

Climate variability regulates population dynamics of a threatened freshwater fish

Integrating fishing and conservation in a risk framework: A stochastic population model to guide the proactive management of a threatened freshwater crayfish

A population model provides support for management decisions, enables ongoing research and reinforces strong partnerships to manage a threatened freshwater crayfish

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