Regionally divergent patterns of grass carp relative abundance, feeding habits and trophic niches in the subtropical Pearl River basin

Abstract

The grass carp is one of the most important herbivore consumers in aquatic ecosystems and plays key roles in controlling macrophyte abundance. To assess the trophic role of grass carp and their potential grazing pressure on macrophytes in their native range, we quantified their relative abundance (RA), diet composition and trophic niches in two major tributaries and the central delta of the Pearl River using a fish capture survey, high-throughput analysis of the 18S rDNA sequences of their gut contents, and stable isotope analysis. The grass carp RA variation among the sampling regions was explained most by river discharge range. The RA was the highest in the West River with high discharge range, and the lowest in the central delta with low discharge range. The grass carp fed primarily on Streptophyta (relative read abundance: 0.40 ± 0.33) and facultatively on Arthropoda, Rotifera, Ascomycota, and Chlorophyta. The Streptophyta proportion increased from the tributaries to the central delta. Such variation contributed most to the dietary difference among regions. Grass carp belonged to the second trophic level. The position and size of isotopic niche of grass carp differed among regions, and their niche breadth decreased from the tributaries to the central delta, as Handling Editor: Se ´bastien Villeger.

Gut microbiomes of cyprinid fish exhibit host-species symbiosis along gut trait and diet

“…The result is consistent with the idea that longer gut length is associated with lower nutrient levels (Olsson et al, 2007;Zandonà et al, 2015;Ghilardi et al, 2021). Related research reveals that intestinal microbes play an important role in host nutrient metabolism, reflecting the host's utilization of an exogenous diet (Huang et al, 2020;Zhu et al, 2021). On the whole, we found discrepancy in the gut microbiota of multiple trophic niches overlapping species, which could potentially reflect exogenous resources utilized efficiency of these species in similar habitat and environments (De León et al, 2014).…”

“…For instance, grass carp is considered an herbivorous fish. However, relevant findings show that the grass carp feeds primarily on Streptophyta and facultatively on Arthropoda, Rotifera, and Ascomycota, indicating that the grass carp is an omnivorous and only partially herbivorous fish ( Zhang et al, 2021 ). Furthermore, the length of the gut determines the duration of food retention, whereas building and maintaining a long gut have high evolutionary and physiological costs.…”

An Observational Study of Skeletal Malformations in Four Semi-Intensively Reared Carp Species

“…In the present study, all the four carp species were reared according to the same protocol; therefore, a possible explanation for the observed different incidences of skeletal malformations is that the same feeding protocol used for fish having different nutritional requirements resulted in different rates of body growth and skeletal anomalies. In the wild, the fish species investigated in this study have different diets: the common carp is an omnivore species that feeds on a variety of plant and animal species, including amphipods, phantom midge larvae, mollusks and ostracods [ 55 ]; the grass carp is an herbivorous species feeding mainly on macrophytes [ 56 ]; the silver carp and the bighead carp are planktivorous species that feed on lower trophic level organisms [ 57 , 58 ].…”

High‐throughput sequencing and fatty acid profile analyses of the Black Amur bream (Megalobrama terminalis) reveal variation in dietary niche associated with geographic segregation

“…In recent studies, the method of DNA-based species identification has been applied to improve the accuracy of diet identification in fish (Zhang et al, 2022). High-throughput sequencing technique can be able to identify the species of gastrointestinal contents, and proves to overcome some shortcomings that occur in traditional morphology-based methods (Watanabe et al, 2021).…”

“…However, quantifying decayed components in gastrointestinal contents proves to be difficult and can be only addressed when a diet component is identified prior to digestion (Buckland et al., 2017 ; Bunch et al., 2021 ). In recent studies, the method of DNA‐based species identification has been applied to improve the accuracy of diet identification in fish (Zhang et al., 2022 ). High‐throughput sequencing technique can be able to identify the species of gastrointestinal contents, and proves to overcome some shortcomings that occur in traditional morphology‐based methods (Watanabe et al., 2021 ).…”