Non‐diadromous recruitment in coastal populations of common bully ( Gobiomorphus cotidianus)

Otolith microchemistry of common bullies (Gobiomorphus cotidianus) collected from the lower reaches of the Mataura, Clutha, and Taieri/Waipori River systems of New Zealand was examined using particle induced X‐ray emission (PIXE). High strontium:calcium (Sr:Ca) ratios in otolith cores relative to otolith edges suggested either diadromous or estuarine‐reared common bullies are present in all three systems, including fish collected from Clydevale (50 km inland) on the Clutha River. However, constant or slightly variable Sr:Ca ratios from otolith core to edge, suggesting a non‐diadromous life history, were also observed in fish from the lower Mataura and Taieri/Waipori systems, even where access to the sea was continuously available. The results suggest that diadromy in common bully may be facultative, and that a proportion of the common bully population may be non‐diadromous in river systems where suitable larval/juvenile rearing habitat is present.