Broad Diet Composition and Seasonal Feeding Variation Facilitate Successful Invasion of the Shimofuri Goby (Tridentiger bifasciatus) in a Water Transfer System

The diet composition of an invasive population of Shimofuri goby (Tridentiger bifasciatus) was investigated bimonthly during the period from September 2015 through August 2016 in Nansi Lake, a storage lake of the East Route of the South-to-North Water Transfer Project, China. The diet consists of a broad spectrum of prey items, including mollusca (Bellamya sp. and Physa sp.), aquatic insects (Odonata sp., Chironomidae sp., and Cirolanidae sp.), other macroinvertebrates (Nematoda sp. and Rhynchobdellida sp.), shrimp (Palaemon modestus and Gammarus sp.), fish (Rhinogobius giurinus and Tridentiger bifasciatus), fish eggs, and detritus. Dominant diets shifted from Rhynchobdellida sp. and unidentified digested food in July to P. modestus during September and November, and then shifted to both P. modestus and R. giurinus. Additionally, cannibalism was observed in March before spawning season of the goby, during which large males (SL > 70.0 mm) predated on small-sized ones. We suggest that broad spectrum of prey items and apparent seasonal shifting of dominant diets in the invasive goby fish, which might be an important mechanism favoring its successful invasion in water transfer system.