Temporal Uncoupling between Energy Acquisition and Allocation to Reproduction in a Herbivorous-Detritivorous Fish

Abstract

Although considerable knowledge has been gathered regarding the role of fish in cycling and translocation of nutrients across ecosystem boundaries, little information is available on how the energy obtained from different ecosystems is temporally allocated in fish bodies. Although in theory, limitations on energy budgets promote the existence of a trade-off between energy allocated to reproduction and somatic growth, this trade-off has rarely been found under natural conditions. Combining information on RNA:DNA ratios and carbon and nitrogen stable-isotope analyses we were able to achieve novel insights into the reproductive allocation of diamond mullet (Liza alata), a catadromous, widely distributed herbivorous-detritivorous fish. Although diamond mullet were in better condition during the wet season, most reproductive allocation occurred during the dry season when resources are limited and fish have poorer body condition. We found a strong trade-off between reproductive and somatic investment. Values of δ13C from reproductive and somatic tissues were correlated, probably because δ13C in food resources between dry and wet seasons do not differ markedly. On the other hand, data for δ15N showed that gonads are more correlated to muscle, a slow turnover tissue, suggesting long term synthesis of reproductive tissues. In combination, these lines of evidence suggest that L. alata is a capital breeder which shows temporal uncoupling of resource ingestion, energy storage and later allocation to reproduction.

Spatial and temporal variation of fish community biomass and energy flow throughout a tropical river network

“…The elevated community‐level allochthonous to autochthonous energy ratios during the early dry season indicate that the majority of fish biomass was supported via energy produced during the wet season. This result aligns with a large body of tropical research that links both wet season flood pulses that increase habitat area (inundated floodplains) and the warmer wet season temperatures with higher rates of energy production that fuel accelerated fish growth rates, gonad development, and increases in body condition (fat reserves) (Balcombe, Bunn, McKenzie‐Smith, & Davies, 2005; Villamarín et al, 2016; Yang & Dudgeon, 2009). However, wet season flow duration and intensity is highly variable (both inter‐ and intra‐annually) for Australian wet–dry tropical rivers, which results in extended periods of time when wet season energy is not available (Jardine et al., 2015; Kennard et al., 2010).…”

Opportunistic top predators partition food resources in a tropical freshwater ecosystem

“…In aquatic systems, the use of isotopic approaches has been integrated with spatial analyses to allow characterisation of dietary patterns by consumers in different habitat types (Jardine et al., ; Villamarín et al., ). In the Amazon basin, remote‐sensing images have been increasingly used to answer ecological questions over large geographical scales (Melack et al., ; Villamarín et al., ).…”

Fragmentation of Andes-to-Amazon connectivity by hydropower dams

“…Therefore, dams far upstream may influence the migratory behavior of these fishes by disrupting the hydrological signals to which they have responded for thousands of years. Further, water temperature changes associated with dams have the potential to affect viability of larval fishes for both migratory and nonmigratory species ( 31 ).…”