Seasonal occurrence and food habits of larvae and juveniles of the threatened goby Gymnogobius castaneus in a salt marsh in Lake Hinuma, eastern Japan

Abstract

Seasonal occurrence and food habits of larvae and juveniles of the threatened goby Gymnogobius castaneus were investigated using monthly seine-net samples in two salt marsh microhabitats (a small creek and marsh edge separated from the creek) in Lake Hinuma, eastern Japan from April 2011 to March 2012. A total of 1,425 G. castaneus individuals (5-55 mm in body length, BL), comprising mostly larvae and juveniles, were collected during the study period. The larvae and juveniles occurred mainly in the creek from April to June, thereafter growing gradually in the same habitat and attaining minimum adult size (42 mm BL) by December. In contrast, extremely few larvae and juveniles (9 individuals) and no adults occurred on the marsh edge during the study. The major food items of larval and juvenile G. castaneus in the creek changed progressively from calanoid and cyclopoid copepods to chironomid larvae and mysids. These results suggest that the goby remains in the salt marsh creek throughout early life stages, with a role as the dietary-shift area of the creek.