Parasites as Indicators of English Sole (Parophrys vetulus) Nursery Grounds

Juvenile English sole (Parophrys vetulus) utilize Yaquina Bay, Oregon as a nursery during at least a portion of their first year of life, but the possibility of the existence of additional nursery grounds offshore has not previously been examined. During 1971, young-of-the-year first appeared in Yaquina Bay in February, were abundant from April to September, and most emigrated to offshore areas in October. Examination of English sole, collected both in the estuary and offshore, revealed certain parasites that appeared to be acquired by the fish only while in the estuary. The acamhocephalan Echinorhynchus lageniformis proved useful in determining the extent of estuarine utilization. The incidence of infection in bay fish before emigration (29.9%) was similar to the incidence in 0-group English sole collected offshore after emigration (28.5%). This result suggests that there was little or no influx of young from other than estuarine nursery grounds to the offshore study area and that on the Oregon coast, estuaries are very likely the exclusive nursery grounds for this species. Other parasites were not useful in determining the extent of estuarine utilization, but two, the nematode Philometra americana and a microsporidan Glugea sp., were considered to be indicators of residence in the upper estuary. The trematode Zoogonus dextrocirrus and metacercaria of the trematode Otodistomum veliporum were found almost exclusively in fish collected offshore, indicating little or no back-and-forth movement between estuary and open