Does flooding affect spatiotemporal variation of fish assemblages in temperate floodplain wetlands?

Abstract

Summary 1. Floodplain wetlands are productive components of lowland rivers and are thought to be important habitat and nurseries for many fish species. Fish assemblages inhabiting floodplain wetlands vary considerably through space and time and are largely shaped by wetting/drying cycles, although there is little understanding how many aspects of flooding (e.g. magnitude, timing, duration, frequency) influence the fish assemblages. As a consequence, decisions on flooding of wetlands by managers aimed at restoring native fish assemblages are often based on limited knowledge. 2. This study examined the importance of total duration of flooding on the temporal and spatial dynamics of wetland fish assemblages in the Murray River, in south‐eastern Australia. The study examined: (i) how the abundance of 0+ and 1+ fish varied with wetland, season and the duration of wetland filling; (ii) how environmental parameters, including food production changed in relation to the duration of wetland filling; (iii) changes in condition indices for the most abundant species and (iv) changes in species richness and total abundance over time. 3. The 0+ fish assemblage varied more through space and time than the 1+ assemblage. Longer cumulative river–wetland filling was associated with greater total abundances of newly recruited (0+) fish; this was particularly true for common carp (Cyprinus carpio, alien) and carp gudgeon (Hypseleotris spp., native). The body condition of carp gudgeon also increased with the duration of filling, even though static measures of food production declined. The small flooding events that occurred as part of this study did not translate into measurable improvements in the fish assemblage over the longer term (3 years), but did prevent wetlands from drying and thus maintained these habitats as refuges.

Flows for native fish in the Murray‐Darling Basin: lessons and considerations for future management

“…Longer duration river–wetland connections also increase the abundance of young‐of‐the‐year fish in wetlands, in particular Carp Gudgeon and the alien Common Carp (Beesley et al . ; Conallin et al . ).…”

“…; Beesley et al . , ) while others, such as Australian Smelt ( Retropinna semoni ), can increase growth and condition under a range of flows (Tonkin et al . ).…”

Response of a floodplain fish community to river-floodplain connectivity: natural versus managed reconnection

“…For example, certain fishes may rely on floodplain inundation to access critical spawning habitats (Janáč et al 2010;Sommer et al 1997). Subsequently, these habitats may serve as important nurseries for larval and juvenile stages, whereby floodplain habitats provide better refuge from predators, higher food abundance, and more suitable temperatures than the main channel (Beesley et al 2012;Feyrer et al 2006;Jeffres et al 2008;Sommer et al 2001). Fish of all stages of development may migrate to the floodplain during floods to access a rich pulse of trophic resources (Balcombe et al 2007;Puckridge et al 2010), which may in turn result in pulses of increased growth for adult fishes (Schramm and Eggleton 2006).…”

“…Indeed, the floodplains of large rivers in Europe, North America, and Australia have been developed to meet agricultural and domestic needs of humans, prohibiting the reinstatement of a natural overbank flooding regime (Galat et al 1998;Kingsford 2000;Tockner and Stanford 2002). Along these rivers particular floodplain reserves are being selected for the delivery of "environmental water allocations" (EWAs) to sustain critical structural and functional components of river-floodplain systems (e.g., Beesley et al 2012;Galat et al 1998). To deliver EWAs to particular sites, expensive regulation infrastructure may be required.…”

Patchiness in food resources drives fish abundances in emergent macrophytes under field and experimental conditions

“…), within emergent macrophyte stands in a floodplain billabong (oxbow lake) of the River Murray (Dugays 2 billabong) and in experimental billabongs (EBs). These fish are often highly abundant in these billabongs (Balcombe & Closs, 2004;Beesley et al, 2012) and dominate the small-bodied fish assemblage within these dense emergent macrophyte stands (Balcombe & Closs, 2000.…”