Chironomid diversity in the diets of Ponto-Caspian gobiids in a freshwater habitat: Implications for resource partitioning

Abstract

Chironomid taxa in the diets of six co-occurring gobiids (Caucasian dwarf goby Knipowitschia caucasica; monkey goby, Neogobius fluviatilis; racer goby, Babka gymnotrachelus; round goby, Neogobius melanostomus; bighead goby, Ponticola kessleri; and western tubenose goby, Proterorhinus semilunaris) were investigated in a freshwater habitat in Ukraine. Overall, 32 chironomid morphotypes were identified, among which the most abundant were Polypedilum convictum, Cricotopus sylvestris, Glyptotendipes spp., and Endochironomus albipennis. The racer and monkey gobies were characterized by the highest diversity of chironomid morphotypes in their diets, while the bighead goby by the lowest diversity. Highest similarities of chironomid assemblages in gut contents were observed among the monkey, racer, and round gobies as well as between the bighead and tubenose gobies, while the lowest similarity was observed between the monkey goby and Caucasian dwarf, tubenose, and bighead gobies. Mean sizes of chironomids in the gut contents of different gobiids varied; Caucasian dwarf and tubenose gobies consumed significantly smaller chironomids. Diversity of chironomid taxa in the diets of gobies depended on the type of each fishes’ habitat. Tubenose and bighead gobies preyed mainly on phytophilous chironomids; the monkey and round gobies preferred bottom-dwelling, burrowing chironomids; while Caucasian dwarf and racer gobies consumed both phytophilous and bottom-dwelling, burrowing taxa.