Using the chemical composition of otoliths to evaluate the nursery role of estuaries for English sole Pleuronectes vetulus populations

Juvenile English sole Pleuronectes vetulus were collected from estuaries and shallow, sandy, coastal habitats along the central California coast between 1996 and 2000, and adult English sole were collected from the Monterey Bay region in 2001 and 2002. The chemical composition of (1) whole juvenile otoliths and (2) the juvenile portion of adult otoliths was determined using inductively-coupled plasma mass spectrometry (ICPMS). The concentration of Sr and Li in juvenile otoliths consistently differed between fish collected from estuarine and coastal habitats, Linear discriminant-function analysis (LDFA) based on the Sr and Li content of juvenile otoliths was used to assign juvenile and adult fish to either the estuarine or coastal habitat group. Juveniles were assigned to the habitat type where they were captured with an accuracy of 77% for the 'All Sites' model and 82% for the 'Monterey Bay' model. The proportion of adult fish that were assigned to the estuarine habitat group was estimated to range between 45 and 57% depending on the model used. This level of estuarine contribution to adult English sole populations is much higher than would be expected based on the relative area of estuarine and sandy coastal habitats in central California. These results indicate that estuarine habitats are an important source of recruits for adult flatfish populations, and that conservation of estuaries may help maintain high levels of recruitment to harvested populations in central California.