Density and distribution of potential prey for larval fish in the main channel of a floodplain river: pelagic versus epibenthic meiofauna

Abstract

Fish larvae require high densities of appropriately sized prey items for their survival and recruitment. It has been widely assumed that inundated floodplains are the major source of high densities of prey in floodplain rivers. This study examined the density and distribution of both pelagic and epibenthic meiofauna in a range of potential larval fish nursery habitats within the main channel of an Australian floodplain river. Although sufficient densities of meiofauna were found in the main channel environment to sustain fish larvae, the prey source was predominantly in the epibenthic zone, where the density of meiofauna was on average 100 times greater than in the pelagic zone. There was no apparent relationship between the density of meiofauna, both epibenthic and/or pelagic, and the preferred nursery habitats of fish larvae. This study suggests that an abundant prey resource for developing fish larvae may exist in main channel environments without inputs from the inundated floodplain. However, further studies are required to determine the relative contributions and importance of prey resources on inundated floodplains compared to the main channel environment for larval survival and cohort strength between successive years. Additionally, this study highlights the importance of sampling the epibenthos, and suggests that the significance of epibenthic meiofauna has been severely underestimated in many previous studies.

Coping with hydrogeomorphic variations in a prairie river: resiliency in young‐of‐the‐year fishes

“…The second competing hypothesis, the low-flow recruitment model, emphasizes the importance of low discharge periods for spawning and larval recruitment because prey populations are denser at this time (King, 2004a). Dettmers et al (2001) and King (2004a) found that densities of potential invertebrate prey were sufficient primarily in the epibenthic zone of some large Australian and North American rivers to sustain larval fish in the main channel, while littoral and backwater habitats had only slightly greater densities of meiofauna.…”

“…The flood recruitment model (King, 2004a), which was heavily influenced by the flood pulse concept (FPC; Junk et al, 1989), maintains that flooding is beneficial to fish populations because it allows access to food and habitat in the highly productive and structurally complex floodscape (Thorp et al, in press) of large, unregulated rivers. Although flooding increases horizontal connectivity to the floodscape and may also enhance longitudinal connectivity up-or downstream via ephemeral reaches (Dodds et al, 2004), studies have shown that for species relying on littoral resources, the FPC has only held true in areas with long periods of floodscape inundation (Gutreuter et al, 1999;Bartosova and Jurajda, 2001;Penczak et al, 2003).…”

“…YOY fish should reside in those river habitats that optimize growth and survival. While potentially crucial environmental factors, such as temperature, exposure to UV radiation and oxygen concentration, vary among river habitats, it is widely accepted that flow velocity and food availability are the most important ecological mechanisms regulating the distribution and vitality of larval and juvenile fish populations (King, 2004a). A river's geomorphic structure creates hydrologic retention areas (Schiemer et al, 2001), or slackwaters (Thorp and Casper, 2002), which are vital to fish growth and which retard downstream export of YOY fish during hydrologic spates.…”

Evaluation of freshwater invertebrate sampling methods in a shallow aridland river (Rio Grande, New Mexico)

“…Meiofauna often dominate benthic invertebrate as semblages and play important roles in assemblage and ecosystem processes (Palmer et al 2006), such as providing a food source for larval fishes (King 2004a,b). However, meiofauna are not sampled effectively using traditional sampling methods that focus on the water column (King 2004b).…”

Identification of fish nursery areas in a free tributary of an impoundment region, upper Uruguay River, Brazil

“…High availability of food, low water speed, and reduced predation pressure are some of the main characteristics of these areas (ReynalteTataje et al, 2008a). Environments that are most commonly used by freshwater fish larvae as nurseries include bays, channels, marginal lagoons, pools, margins without currents (Scott & Nielsen, 1989;Agostinho et al, 1993;King, 2004;Reynalte-Tataje et al, 2008a), and floodplains (Daga et al, 2009;Gogola et al, 2010). Floodplain environments are of great importance for the initial stages of Neotropical fish development (Paiva, 1982;Gogola et al, 2010).…”