Estuarine Subtidal Sand and Mud: Channels
Estuarine “intertidal” channels (described above) combine into larger and deeper channels and eventually into the mainstem channels of river mouths. These rich habitats are extremely important as feeding and nursery areas for diverse bird and fish assemblages. Wading and surface-foraging birds use the edges of channels, while surface and diving birds such as grebes, cormorants, mergansers, scoters, waterfowl, and even auklets and murrelets feed and roost in open channels. Kingfishers, osprey, eagles, terns, and others dive for fish from the air. Raccoon, beaver, nutria, river otter, and marine mammals (sea lions and seals) feed in channels. Substratum composition (relative abundances of sand and mud) and salinities vary with flow rate and distance from the estuary mouth.
A wide variety of polychaetes, including Magelona spp, Capitella capitata, Paraonella platybranchia, Eteone spp., Hobsonia florida, and numerous spionids. Amphipods include phoxocephalids (river mouths), Corophium salmonis, Paramoera columbiana, and Eogammarus spp. Other common species are Macoma balthica, Cancer magister, and the shrimp Crangon spp. Fishes include shiner perch, peamouth, Pacific tomcod, snake prickleback, sculpins, speckled sanddab, English sole, starry flounder, and juvenile salmon.
Coastal estuarine channels.
Simenstad, 1983; Albright and Borithilette, 1982; C. Staude unpubl. data.