When and where are catfish fat fish? Hydro‐ecological determinants of energy reserves in the fork‐tailed catfish, Neoarius graeffei, in an intermittent tropical river

Abstract

The cultural and ecological importance of fork‐tailed catfish, Neoarius graeffei, in northern Australia is linked to its energy stores, or how fat fish are. Water resource development that alters river flow has the potential to impact the energy stores of fork‐tailed catfish. We investigated the influence of flow and habitat on the energy reserves of fork‐tailed catfish during the dry season in an intermittent wet–dry tropical river using data collected in three years with different flow volumes from a variety of habitats, i.e. different mesohabitats (tributary, main‐channel) and pool sizes. Julian day was included to describe seasonal trends. We used mesohabitat and pool size to reveal where fork‐tailed catfish had the most energy reserves and flow‐year and Julian day to reveal when reserves were greatest. Body condition and the quantity of intramuscular and coelomic fat were used to describe energy reserves. Predictive models created for each metric revealed that fork‐tailed catfish body condition and intramuscular fat were greater in years following moderate to high wet‐season flow, smallest in a year following very low flows and decreased as the dry season progressed. Coelomic and intramuscular fat of fork‐tailed catfish was also lower in smaller pools. There was no association between mesohabitat and energy store. These when and where hydro‐ecological patterns highlight the importance of wet season flows and groundwater‐fed refuge pools for fork‐tailed catfish energetics in this wet–dry tropical river. Intermittent rivers flowing through wet–dry tropical savanna habitats are under increasing threat globally and the results of the present study illustrate how flow variation may impact on biota and influence their continued survival and functional roles.

Inter‐decadal variation in diadromous and potamodromous fish assemblages in a near pristine tropical dryland river

“…The high productivity booms from large floods are likely to increase food availability and quality, allowing for higher growth rates of fish during the wet season as well as the early dry season. Similar trends have been observed in previous studies which have found larger individuals or better body condition of individuals following larger floods in dryland rivers (Balcombe et al, 2012; Beesley et al, 2021; Lear et al, 2021). It is interesting that the opposite pattern was distinctly observed in C. lentiginosus ; it is possible that this dry season specialist does not forage well under conditions typically observed in years with larger wet seasons, including higher flow rates and deeper pools, and therefore has reduced growth rates or reduced survival of large individuals during wetter years.…”

Morphological changes and reproductive costs in brooders of two mouthbrooding freshwater fishes

“…Mouthbrooding in fishes is likely to be a particularly costly parental care investment for the caring parent, where the ability of brooders to ingest food and conduct normal gill function is likely to be af- (Jakob et al, 1996;Le Cren, 1951) can be influenced by season, reproductive state (spawning), morphological factors and the availability of resources in the environment (Abecia et al, 2018;Beesley et al, 2021;Luiz et al, 2019). In our study, brooders of both species showed a general reduction in at least one body condition index relative to nonbrooders.…”

“…The diversion of body energy resources from tissue maintenance to caring for young is an important potential reproductive cost to the adult care giver (Alonso‐Velando & Alvarez, 2012). Variations in relative body condition (often used a proxy measure of body fitness in fishes (Jakob et al, 1996; Le Cren, 1951) can be influenced by season, reproductive state (spawning), morphological factors and the availability of resources in the environment (Abecia et al, 2018; Beesley et al, 2021; Luiz et al, 2019). In our study, brooders of both species showed a general reduction in at least one body condition index relative to nonbrooders.…”

When to Use Transdisciplinary Approaches for Environmental Research

“…This project used scientific knowledge from the ecological and hydrological disciplines to determine the water requirements for the significant aquatic fauna and riparian plants (e.g., Beesley et al, 2020;Burrows et al, 2020;Beesley et al, 2021;Canham et al, 2021). Two main groups of non-academic actors were involved in the project: government scientists and planners, and Traditional Owners and Indigenous rangers.…”