Juvenile fish response to wetland inundation: how antecedent conditions can inform environmental flow policies for native fish

Abstract

Summary1. One of the greatest threats to lotic ecosystems is flow regulation. The impacts of flow regulation on native fish are often mitigated using periodic water allocations, termed environmental flows. The effectiveness of environmental flows has been studied in some systems, but the role of flow conditions prior to water allocation (i.e. antecedent conditions) has rarely been quantified. 2. We evaluated the effects of floodplain inundation due to variable river flows on fish abundance in wetlands of the mid-Murray River, Australia, using a hierarchical multi-species model parameterized to estimate fish abundance while accounting for variable detection. We evaluated the effects of antecedent conditions on three time-scales, including patterns in long-term (5 years prior), medium-term (1 year prior) and short-term (3 months prior) wetland inundations. 3. While species-specific responses to antecedent conditions varied, we found a general divergence in the responses of native and non-native species. Native fish tended to respond positively to consistent frequent inundation of wetlands, while non-native fish tended to respond positively to long-or medium-term dry periods and short-term wet periods. 4. Fish detection probability varied among species, sampling gears, wetland areas and wetlands, indicating that accounting for variable detection can be critical when evaluating patterns in fish abundance. 5. Synthesis and applications. We found that antecedent conditions can be important for determining environmental water allocation policies. Our results indicated that native fish generally responded positively to frequent inundation of wetlands, while non-native species generally responded positively to long dry periods followed by short-term inundation events. For some non-native species, long dry periods not only generated a positive response in abundance, but enhanced the positive response to short-term inundation events. The divergence between native and non-native fishes' responses to antecedent conditions provides opportunities for managers to allocate water to favour native fish assemblages. Future research of environmental flows for managing fish assemblages should consider antecedent conditions and apply models that account for incomplete detection, such as the one developed here, to better inform the management process.

Using abiotic drivers of fish spawning to inform environmental flow management

“…; Beesley et al . ). This procedure gives similar results as more complex methods such as modelling parameter inclusion probabilities with Bayesian mixture models.…”

“…Furthermore, few studies explicitly link flow–biota relationships to the decision process experienced by flow managers, hindering the development of targeted management strategies (but see Beesley et al . ). These limitations reduce managers' ability to predict the outcomes of environmental flow strategies and, thus, the effectiveness of management actions, exposing the discipline to criticism (Poff et al .…”

Hierarchical multi‐taxa models inform riparian vs. hydrologic restoration of urban streams in a permeable landscape

“…There are several benefits of this modeling approach over traditional and more common multi-variate methods (e.g., Olden 2003, Iknayan et al 2014, Warton et al 2015a. Finally, taxa-specific models as opposed to traditional multivariate methods (e.g., Legendre and Legendre 2012) can be used to resolve uncertainty among competing management options through explicit prediction, providing a direct link between ecological research and management (e.g., Beesley et al 2014, King et al 2016. This model behavior occurs because the community-level hyper-distributions act as priors for taxa-specific estimates.…”

“…Information theoretic approaches to variable selection, such as AIC and DIC, are often unreliable when applied to complex Bayesian hierarchical models with multiple random effects (Celeux et al 2006, Millar 2009, Hooten and Hobbs 2015, Broms et al 2016); therefore, we applied a simplified procedure based on credible interval overlap with zero that is common in the ecological literature (e.g., White et al 2013, Beesley et al 2014, King et al 2016. Information theoretic approaches to variable selection, such as AIC and DIC, are often unreliable when applied to complex Bayesian hierarchical models with multiple random effects (Celeux et al 2006, Millar 2009, Hooten and Hobbs 2015, Broms et al 2016); therefore, we applied a simplified procedure based on credible interval overlap with zero that is common in the ecological literature (e.g., White et al 2013, Beesley et al 2014, King et al 2016.…”

Flow‐mediated predator–prey dynamics influence fish populations in a tropical river

“…Mechanistically, the long-term flow regime imposes evolutionary selective pressures that may favour or select for particular life-history traits, community structure, and behaviours that exploit particular aspects of the flow regime, such as predictable seasonal flow patterns (Hoeinghaus, Winemiller, & Birnbaum, 2007;Lamouroux, Poff, & Angermeier, 2002;Lytle & Poff, 2004;Poff & Allan, 1995). floods), altered habitat availability and connectivity, resource provision, and by providing opportunities for movement and migration, and conditions suitable for spawning and recruitment (Beesley et al, 2014;Kennard et al, 2007). floods), altered habitat availability and connectivity, resource provision, and by providing opportunities for movement and migration, and conditions suitable for spawning and recruitment (Beesley et al, 2014;Kennard et al, 2007).…”