Otolith chemistry of triplefin Forsterygion nigripenne indicates estuarine residency

Understanding the role different habitats play in the life histories of fishes is important for the development of holistic aquatic ecosystem management plans. We used otolith trace element analysis to reconstruct the life history of estuarine triplefin Forsterygion nigripenne and infer its habitat use. Analysis of otoliths using laser ablation inductively coupled plasma mass spectrometry showed an elemental profile without prominent changes in elemental concentration. The otolith elemental profiles were not indicative of movement between waters with substantial Sr:Ca and Ba:Ca differences. The Sr:Ca and Ba:Ca profiles were indicative of within—and near—estuary movements encompassing short time periods. Overall, the otolith microchemical profile was likely indicative of a life history closely associated with estuaries. However, it is difficult to rule out brief excursions to the marine environment given that may not have been of sufficient duration to be recorded in the elemental composition of the otolith. This suggests that F. nigripenne is the only species in southern New Zealand known to be closely associated with estuarine habitat for its entire life cycle.