Geographic variation in natal and early larval trace-elemental signatures in the statoliths of the market squid Doryteuthis (formerly Loligo) opalescens

We found distinct geographic differences in trace element concentrations in both the core and early larval areas of the statoliths of paralarval market squid Doryteuthis (= Loligo) opalescens at sites throughout the Southern California Bight, USA, Laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) of individual statoliths indicated detectable levels of Mg, Mn, Sr, and Ba, with marginal levels of Cr and Pb. While these paralarvae showed considerable within-sample differences in elemental concentrations, there was significant between-site discrimination of natal (core) and early larval signatures for collection sites up to 100 km apart. In 2002 and 2003, levels of Ba and Sr in the statolith cores were significantly different among sites, suggesting differences in the natal environment or local maternal effects. Site specific differences in elemental signatures were also apparent for Mg and Mn in samples taken from outside the core in the early post-hatching period. These same portions of the statolith can be analyzed from adult squid collected on spawning grounds. We showed that concentrations of trace elements in the statolith cores of adults closely resembled the core signatures of squid paralarvae, which opens the possibility of identifying the source populations for stocks of this commercially important species.