Neustonic feeding by juvenile salmonids in coastal waters of the Northeast Pacific

Abstract

The near-surface macrozooplankton fauna off the Washington and Oregon coasts is described from a series of quantitative neuston hauls collected during June, July, and September 1984. Euphausiids, decapod larvae, hyperiid amphipods, and larval fishes were the dominant marine taxa represented. Insects of terrestrial origin were very common and occurred in high abundances, especially during the July and September cruises off Oregon, and their occurrence was coincident with unusual wind patterns. The neuston catches were quantitatively compared with the diets of juvenile coho (Oncorhynchus kisutch) and chinook (O. tshawytscha) salmon collected at the same stations and within the same cruises. There was an overall resemblance between the taxa in the neuston and stomachs of these salmon juveniles, although the larger organisms appeared to be consumed preferentially. Predominantly neustonic taxa also occurred in the diets of other juvenile salmonids and adult coho salmon collected concurrently, but these other predators did not appear to utilize neustonic prey to the same extent as coho and chinook juveniles.