Should I stay or should I go: Hydrologic characteristics and body size influence fish emigration from the floodplain following an atypical summer flood

Abstract

Floods play an important role in regulating ecological patterns and processes in river–floodplain ecosystems. Yet, the hydrologic connectivity between many river–floodplain ecosystems has been severed by anthropogenic activities that have markedly altered these ecological processes. Superimposed over anthropogenic reductions in river–floodplain connectivity, climate change is also shifting flood characteristics to produce more intense, unpredictable floods. To more efficiently manage river–floodplain ecosystems, additional research characterising the ecological consequences of unpredictable floods on fish movements is required. In this study, we used a modified fyke net to characterise the patterns and identify the important drivers of lateral movements of fish emigrating from the floodplain during contraction of a high‐magnitude, late‐summer flood in the Fourche LaFave River, Arkansas, in 2007. We captured approximately 43,200 fish emigrating from the floodplain over an 8‐day period, representing 38 distinct species from 12 families. We related fish‐emigration patterns to different stages of flood contraction and linked species‐specific emigration to water‐level fluctuations and associated changes in floodplain habitat availability and quality. We also show that some species exhibit body‐size emigration patterns, where larger individuals emigrated from the floodplain earlier than smaller individuals. To meet conservation goals for maintaining healthy riverine ecosystems and the biodiversity they support, it will be necessary to continue characterising and identifying the ecological consequences of shifting flood characteristics within river–floodplain ecosystems.

Escaping the dry: Native and non‐native fish outmigration from a receding floodplain following managed inundation

“…By contrast, carp gudgeon density increased as the floodplain transitioned from stable flows to managed recession flows and this species complex still rapidly outmigrated during the managed recession. Similar ecologies were noted on the floodplains of central California (Moyle et al, 2007;Ogaz et al, 2022) and western Arkansas (Walker et al, 2022).…”

“…Built infrastructure, such as floodplain regulators, are a global conservation challenge, especially to riverine and river–floodplain connectivity (Grill et al., 2019; Walker et al., 2022). As water resources become increasingly scarce due to overallocation and climate change, a more encompassing vision about the nature of recovering highly stressed aquatic ecosystems is needed.…”

Assessment of the floodplain fishery of Tonle Sap Lake in Cambodia

“…Differences in fish abundance, richness, and diversity we found between years could be related to differences in environmental requirements and life‐history cues that promote boom‐and‐bust cycles for different species (Arthington & Balcombe, 2011; Chan et al., 2020). For example, many fishes rely on timing or magnitude of water‐level changes as a cue to initiate movement to and from the floodplain for spawning (Poulsen & Valbo‐Jørgensen, 2000; Walker et al., 2022). Higher water levels provide access to a greater diversity of floodplain habitats that serve as nurseries with more protection and feeding opportunities for fishes among inundated forest vegetation (Balcombe & Arthington, 2009; Górski et al., 2011; Halls & Hortle, 2021; King et al., 2003).…”

Tributary streams provide migratory fish with access to floodplain habitats in a regulated river: evidence from alligator gar, Atractosteus spatula

“…Floodplains accessible to fishes during higher flows provide a wide range of benefits, including habitat for spawning, recruitment, foraging, and refuge (Junk et al 1989). Consequently, fishes have emerged as model organisms and ecological indicators for riverscape connectivity, yet there is still limited understanding of fish migration into floodplains (Lasne et al 2007;Castello 2008;Walker et al 2022). This information is critical as fish species that rely on floodplains are among the most imperiled (Tockner and Standford 2002).…”