Do fish isotopic niches change in an Amazon floodplain lake over the hydrological regime?

Abstract

Floodplain lakes are ecosystems characterised by annual flood and dry cycles. Fish ecology is influenced by the flood pulse due to the large influx of allochthonous food resources and diversification of habitats during the flood cycle, while during the dry cycle, fishes tend to be confined in reduced habitat. The aim of this study was to evaluate the seasonal variation in trophic niche width and overlap of four species—Mylossoma duriventre, Prochilodus nigricans, Cichla.pleiozona and Serrasalmus rhombeus—in an Amazonian floodplain lake. Stable isotope analyses were used to estimate trophic niche width and overlap during the flood and dry seasons. We hypothesised broader niche width for all species during the flood cycle and a higher degree of overlap between the two piscivorous fishes during the dry cycle. Isotopic niche width was 72% broader for P. nigricans, 61% for S. rhombeus and 54% for C. pleiozona during the dry cycle, which did not support our hypothesis. Core niche width overlaps were not observed between piscivorous species in either flood or dry cycle. The results indicate that seasonal variation in isotopic niche width is specific to feeding habit. Understanding how fish trophic ecology responds to changes in the hydrological regime during the seasons is crucial for sustainable fishery management in a region where many people rely heavily on fish for nutritional and economic purposes.

Influence of Seasonal Water Level Fluctuations on Food Web Structure of a Large Floodplain Lake in China

“…The extent to which fish species are affected by water level fluctuations depends on their mobility and habitat requirements [14,35]. In tropical floodplain lakes, fish ingest relatively more vegetative food during the high-water period as fish become more dispersed in the vast flooded area [30,36], whereas an increased carnivory is observed during the dry season when fish become confined to the remaining water body and food resources become limited [30].…”

Seasonal Variation in Resource Overlap Between Red Swamp Crayfish (Procambarus clarkii) and Native Species in Poyang Lake Wetland, China

“…Values of MNND and SDNND tended to decline from rising to high to falling water conditions, which implied that aquatic consumers exploited similar resources during falling water season (i.e., higher trophic redundancy) (Wang S. et al, 2021a). Changes in food availability and diversity may result in differences in CR, an indicator for trophic niche diversity (Azevedo et al, 2022). The flood pulse concept predicts that aquatic organisms (e.g., fish) have access to more diverse habitats and food resources during floodplain inundation (Junk et al, 1989;Pool et al, 2017).…”

“…SIA has been used increasingly to estimate resource utilization and trophic interaction among sympatric consumers (García et al, 2020;Ercoli et al, 2021;Wang Y. et al, 2021b). The distribution of consumers in isotopic space has been used as an indicator of trophic niche width and trophic niche overlap (Peel et al, 2019;Azevedo et al, 2022). Previous studies have shown that invasive species had higher trophic plasticity (Correia, 2002;Jackson et al, 2016) and greater ability to exploit local resources than native species (Sakai et al, 2001;Britton et al, 2019).…”