Population characteristics of yellow catfish (Peltobagrus fluvidraco) along the longitudinal profile of Three Gorges Reservoir, China

摘要

The length-frequency and age distributions, condition factor (K), gonadosomatic index (GSI) and gastrosomatic index (GaSI) of yellow catfish (Peltobagrus fluvidraco) were studied at three sites along the 500-km longitudinal profile of Three Gorges Reservoir. Across all three sites (dam, mid-reservoir and upper reservoir), GSI increased from April through June, with peak values observed in May and June. Mean K and GSI for fish captured near the dam were significantly higher compared to mid-reservoir or upper-reservoir areas. The GaSI index showed no significant variations across sites. However, the length-frequency histogram of yellow catfish in the more riverine upper reservoir was log-normal and skewed towards larger (total length) fish, a pattern that was significantly different from mid-reservoir or near-dam habitats, where fish length data were normally distributed but at a smaller length mode. Age estimations using otolith sagittae revealed that the spawning population was dominated by fish from only two age-classes (1 and 2). This study provides novel insight into population characteristics of fish along the substantial spatial scale of Three Gorges Reservoir. Given the irregular population size-and age-structure and the fact that the species is currently commercially exploited, this population is believed to be susceptible to overfishing. Restricted harvesting during peak reproductive months is recommended and suggested that additional research is needed on recruitment and harvest dynamics of this species throughout Three Gorges Reservoir. Additional research is also required to determine whether the spike in K and GSI at lentic sites is a transient product of recent impoundment or an indicator of optimal hydrologic habitat for the species.