were not mentioned in Nixon and Oviatt (1973) or Cammen (1976) , al- 

 though both Maooma hdlthica and Mya arenavia occur in Atlantic coast 

 estuaries. 



The trophic structure of invertebrate communities in the Oregon 

 marshes is strongly oriented to the detritus food chain. In the marsh 

 soil, low vegetation, debris line, tidal creek substrate, and tidal 

 flat habitats, numbers of detritivores and scavengers far exceeded 

 the number of herbivores (Figs. 13 to 18). Only the upper vegetation 

 sampled by sweep net contained a large proportion of herbivores, and 

 this proportion increased from low marsh to high marsh. Herbivores 

 were concentrated on growing plant tissues where their food resources 

 are greatest; detritivores and scavengers were abundant in surface 

 debris and in the soil where their food accumulates. Overall animal 

 abundance appears to favor detritivores and scavengers and thus the 

 detritus food chain. This is consistent with the observation that 

 energy flow in salt marshes is greater through detritus than through 

 grazing food chains (Teal, 1962), and that marsh plants produce sur- 

 pluses of organics that are both incorporated into marsh food chains 

 and exported to other estuarine food chains (Teal, 1962; Cameron, 1972; 

 Eilers, 1979). 



As in other studies (Davis and Gray, 1966; Cameron, 1972), spiders 

 were found to be the dominant invertebrate carnivore in terrestrial 

 food chains. 



Few fish species were collected in the marsh habitats. Three- 

 spine stickleback, staghorn sculpin, and fewer numbers of prickly 

 sculpin {Cottus asper) , coastal sculpin (C. ateutious) , shiner surf- 

 perch, surf smelt, and chum salmon were found in the tidal creeks. In 

 tidal creeks of marshes in the Fraser River estuary, Dunford (1975) 

 collected juvenile chum and chinook salmon, threespine stickleback, and 

 small numbers of prickly sculpin. In slough habitats he collected a 

 much greater variety of fish, including juvenile salmon, starry 

 flounder, threespine stickleback, prickly sculpin, staghorn sculpin, 

 peamouth {Mylooheilus aaurinus) , squawfish (Ptyohoaheilus ovegonensis') , 

 and several species of the minnow family ( Cyprini-dae) . Although the 

 two studies agree that fish diversity is higher in sloughs than in 

 tidal creeks, species composition tended toward freshwater species in 

 the Fraser River sloughs and marine species in the Siletz River slough. 



Daiber (1977), working in Delaware marshes, and Shenker and Dean 

 (1979), working in South Carolina marshes, observed high usage of 

 Atlantic coast tidal creeks by larval and juvenile fishes. Their 

 results emphasize the high diel and seasonal variability in catch com- 

 position. Also, while more species used creeks in the lower more 

 marine parts of the estuary, variation in use from creek to creek was 

 high (Daiber, 1977). A total of 22 species and 16 families of larval, 

 juvenile, and adult fish used the South Carolina Creeks. Many of 

 these are marine species. 



Based on Dunford's (1975) study and the Oregon study, the fish 

 fauna of marsh tidal creeks in the Pacific Northwest estuaries are 

 low in diversity and does not include large or diverse larval and 



48 



