marshlands (British Columbia) in the spring and summer. The salmon consumed 

 a variety of terrestrial, planktonic, and benthic foods. Dunford identified 

 13 other fish species in these habitats. 



Junvenile salmonids in nonmarsh habitats may exploit marsh-based food 

 chains. In the Squamish River estuary (British Columbia), Cliff and 

 Stockner (1973) discovered heavy feeding by salmon on amphipods (principally 

 Anisogammarus spp.) which are largely marsh-dependent. Juvenile chum 

 salmon in the Nanaimo estuary (British Columbia) heavily exploit harpacti- 

 coid copepods and thus have a food chain that depends on detritus from the 

 marshlands (Healey, 1979) . 



Although past studies of Pacific coast salt marshes have been limited, 

 the data collected suggest similarities of structure and function between 

 these marshes and the Atlantic coast marshes; e.g., levels of primary 

 production, contribution to detritus-based food chains, and some aspects of 

 community composition. Important questions remain regarding the value of 

 Pacific coast marsh habitats and food chains for various fish species, 

 especially juveniles. The trophic structure and function of these marshes 

 should be determined, especially to evaluate the human use of marshlands. 



This study characterizes the animal communities and food chains of 

 marshes in Siletz and Netarts Bays, Oregon. The objectives were to develop 

 taxonomic lists, to characterize the trophic structure of marsh invertebrate 

 communities, and to identify the principal fish species using the marsh and 

 marsh-related habitats. In addition, food habits of these fish were studied 

 to determine marsh food-chain relations. 



II. DESCRIPTION OF STUDY AREAS 



1 . General . 



Salt marshes of the Pacific Northwest are of recent origin and, in 

 comparison to the Atlantic marshes, are limited in size and distribution. 

 The steep and rocky coastlines of Washington, Oregon, and California restrict 

 suitable marsh habitats to a few bays, estuaries, and lagoons. These 

 marshes generally lack the thick peat layers which reflect long-term 

 accretion (MacDonald, 1969) . 



In Oregon, interglacial deposits filled river mouths, and post- 

 Pleistocene drowning produced extensive tidelands in the northern and 

 central bays. More rapid sediment deposition in the southern bays matched 

 rises in sea level and thus restricted tideland development. All the 27 

 estuaries in Oregon are presently accumulating sediment. Fires in the mid- 

 19th century and the Tillamook fire in 1933, augmented by logging and other 

 detrimental land-use practices, have increased the erosional sources of 

 bay deposits (Jefferson, 1974). 



The climate of the Oregon coast is wet-temperate. Annual precipi- 

 tation averages about 180 centimeters and temperature about 10° Celsius. 

 The frost-free season lasts 250 to 300 days, and freezing weather is 

 infrequent. Pacific winter storms accompanied by gale-force winds are 

 common, but generally lack the destructive force of tropical and convective 

 storms common to the Atlantic coast. Winter freshets in coastal rivers 



