Efficacy of Inducing Sr Marks in Otoliths of Larval Viviparous Fishes: Comments on the Utility of Larval Otolith Marking in Determining Dispersal of US Fishery Resources

Dispersal and retention fish larvae are among the least understood aspects of marine fish ecology. The extent of larval movements away from source populations is rarely known but is vital for effective applications of management interventions, particularly marine protected areas (MPAs). Captive testing and field trials have shown that mass marking of larvae in vivo is induced by intra-muscular injection of elemental strontium to gestating female rockfishes (Scorpaenidae) and surfperches (Embiotocidae), and trans-generational transfer of the strontium to otoliths of developing larvae via matrotrophic viviparity. The efficacy of the in vivo transfer of strontium to larval otoliths in highly fecund rockfishes was tested in brown rockfish (Sebastes auriculatus). All otoliths of larvae produced from Sr injected females showed enriched strontium:calcium ratios near the otolith edges, while otoliths from control larvae did not. Further, the strontium signatures did not appear to be affected by larvae position within the ovary. These results indicate that induced trans-generational chemical marking is a highly reliable technique for mass marking large numbers of extremely small viviparous fish larvae. Differing results in studies using both trans-generational larval otolith marking and genetic parental analyses revealed the need to test the utility these techniques when applied to larval fish dispersal questions. The US temperate marine fishery management need for information on larval fish dispersal cannot be satisfied by findings from tropical reef fish studies that marked larval otoliths using chemicals not allowed by the Food and Drug Administration.