Mid-level consumers in Puget Sound
A variety of animals, including invertebrates, fish, mammals, and birds, consume the suspension-feeders, filter-feeders, grazers, and detritivores that serve as a link between the primary producers and detrital pathways and the upper levels of the food web.
Fish and birds
The juvenile and adult stages of many fishes and bird species are important mid-level consumers. The diet of these species in Puget Sound can vary dramatically in breadth and complexity and can contain prey from many different habitat types. For example, some juvenile Chinook salmon have eaten (at any one time) terrestrial insects, aquatic insects, amphipods, copepods, polychaetes, fish larvae, and crab zoea (Brennan et al. 2004).
Planktivorous fish
Planktivorous fish feed in water-column habitats associated with nearshore and open marine waters of Puget Sound. Based upon their abundance/biomass, Pacific herring, juvenile salmon, juvenile Pacific sand lance, and northern anchovy are probably the most important planktivores. Other noteworthy species in this group include several important rockfish species (black, canary, widow, and yellowtail rockfish), and some species of marine birds that forage on amphipods and euphausiids (e.g., Bonaparte’s gull). A wide variety of species of copepods, crab larvae, and euphausiids or krill are usually elements of planktivore diets (Strickland 1983). Diets of planktivores can vary over relatively small spatial and temporal scales, which is consistent with the boom-and-bust dynamics of their prey (e.g. barnacle larvae, copepods, and crab larvae).
Invertebrate predators
In contrast to the planktivorous fish, there are many species of birds and fish that eat mostly invertebrate food items found on or in the benthos. There are far more species in this trophic group than in any other groups. What one species eats depends upon many factors, including varying environmental conditions, habitat (e.g., deep versus shallow), and predator and prey morphology (e.g., bill size and shape). Shorebirds such as plovers, yellowlegs, killdeer, and many migrating sandpiper species forage in the sediments left exposed by the ebbing tide – a common scene in sand and mudflats around Puget Sound. Flatfish often eat the tips of bivalve siphons, and there are species that eat their prey off the substrate surfaces such as oystercatchers, gulls, and scoters. Some of the abundant surfperches such as shiner perch primarily also forage on organisms that occupy substrate surfaces.
