Journal of Ecology and Rural Environment ›› 2022, Vol. 38 ›› Issue (9): 1157-1164.doi: 10.19741/j.issn.1673-4831.2021.0586

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Feeding Habits of Gymnodiptychus dybowskii and the Changes of Its Food Type Caused by the Introducing of Rainbow Trout

ZHANG Yuan-yuan1, SU Hui-ming2, LIU Kai1, HUANG Cheng1   

  1. 1. School of Life Science, Nanjing University, Nanjing 210023, China;
    2. Administration of Fukang Nationalized Forest, Fukang 831500, China
  • Received:2021-09-26 Online:2022-09-25 Published:2022-09-21

Abstract: Gymnodiptychus dybowskii, an ecologically sensitive local economic species, was chosen to assess the environmental risks caused by the introducing of rainbow trout (Oncorhynchus mykiss) into the Tianchi Scenic Area. Niche breadth index, trophic level assignment (TLA), intestine emptying rate, similarity index, Spearman's ρ, and selectivity index were used to assess the trophic niche of the two species. Furthermore, the dangerous level of invasive rainbow trout was assessed by using an invasive species evaluation index. Results reflect that the occurrence frequency of entomic food between young rainbow trout and G. dybowskii was substantially overlapped, with Spearman's rank correlation coefficient to be 0.600 (P<0.01). Chironomidae, Copepods, Caddisfly, Ephemeroptera, Amphipod, Clams, and Coleoptera were shown to be competing diets between the two fish species. Unlike earlier articles "ate Algae sometimes (Chlorophyta, 15.6%)" that were reported in other papers, G. dybowskii primarily foraged Algae (Chlorophyta, 81.82%). Rainbow trout was a top consumer in the food web and its trophic level was higher than that of G. dybowskii (TLA, 2.30 > 2.06). On the other hand, the higher diversity index in G. dybowskii than in rainbow trout (Simpson index, Shannon-Wiener index, P<0.05) might indicate that G. dybowskii was compelled to expand content species items, particularly hunting more algae. After reviewing articles and conducting field research, it is concluded that rainbow trout is a harmful introduced species with a risk score of 0.995 5. The finding demonstrates that rainbow trout encroaches the trophic niches of local species, forcing native species to adjust their diet composition to a certain degree. As a result, activities such as importing and releasing alien species (such as rainbow trout) into Tianchi nature reserve are not recommended and this study also offers protective measures for the protection of endemic biodiversity.

Key words: Tianchi in Xinjiang, rainbow trout, Gymnodiptychus dybowskii, feeding habits analysis, trophic niche

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