Feeding habits of the cyprinid Gymnocypris firmispinatus in the Anning River, China
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ORIGINAL ARTICLE Biology
Feeding habits of the cyprinid Gymnocypris firmispinatus in the Anning River, China Baoshan Ma1 · Bin Xu1 · Kaijin Wei1 · Xiangyun Zhu1 · Jin Xu1 · Jianchao Lu1,2 · Jun Wang3 Received: 22 November 2019 / Accepted: 16 April 2020 / Published online: 19 August 2020 © Japanese Society of Fisheries Science 2020
Abstract The feeding habits and prey selection of Gymnocypris firmispinatus in the Anning River were investigated with respect to fish size, season and sex. Gut contents of 305 individuals ranging in size from 57 to 193 mm total length were analyzed, and 16.0% of the guts were found to be empty. The vacuity index indicated that the feeding intensity of the fish roughly followed a seasonal trend, with minimum food intake in winter. However, statistically insignificant variation in the vacuity index was observed between size classes and sexes. Overall, 46 prey taxa belonging to five orders (Ephemeroptera, Plecoptera, Trichoptera, Coleoptera and Diptera) were identified in the guts of 141 fish. G. firmispinatus fed almost exclusively on aquatic insects, of which Baetis sp. and Simulium sp. were the predominant prey species, followed by Diamesa sp. and Glossosoma sp. G. firmispinatus is a generalist feeder that relies upon a wide trophic spectrum. The multivariate analysis revealed that fish size was the principal factor affecting diet. Small individuals fed primarily on small ephemeropteran larvae and dipteran larvae, whereas larger individuals preferably consumed bigger trichopteran larvae. In terms of its prey, G. firmispinatus showed strong positive selection for dipteran larvae and trichopteran larvae, and negative selection for ephemeropteran larvae, plecopteran larvae and coleopteran larvae in all seasons. This study provides evidence that the observed diet of G. firmispinatus can be explained by prey selection rather than random feeding. Keywords Feeding habits · Diet composition · Macroinvertebrates · Prey selection · Gymnocypris firmispinatus * Kaijin Wei [email protected]
Introduction
Baoshan Ma [email protected]
Species of the Schizothoracinae, which are generally characterized by a long life span, slow growth, late maturity and low fecundity, are dominant in the Qinghai–Tibet Plateau ichthyofauna (Chen and Cao 2000). An endemic species of the Qinghai–Tibet Plateau, Gymnocypris firmispinatus is only distributed in the Jinsha River and its tributaries. This small fish usually resides in rivers at elevations of about 2000–3000 m, where the water temperature is very low, even in summer (Chen and Cao 2000; Ma et al. 2019a). Recently constructed cascade hydropower developments block the continuous flow of water in these rivers and destroy their ecological integrity, e.g., they seriously impact the spawning migration of adult G. firmispinatus and the feeding migration of juveniles (Ru et al. 2016). Sand excavation also destroys the habitats of these fish. Moreover, overfishing has exacerbated the decline in the G. firmispinatus population. A fundamental understanding of the ecolo
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