Estuarine Intertidal Mixed-Fines and Mud: Channel/Slough

Undisturbed channels and sloughs are troughs within a tidal flat that drain slowly throughout the tidal cycle. They are usually lined with marsh plants, contain numerous invertebrates and fishes, and are used by shorebirds, herons, raccoons, otter, mink, and other organisms as important foraging areas. Dunlin, sanderling, and western sandpipers are especially abundant.  Most resident and migratory birds, especially waterfowl, that use estuaries for feeding or roosting occupy channels at various times.  Precise invertebrate and plant assemblages probably vary with salinity, flow rate, and substratum type, but common species of blind and subsidiary (shallow, intertidal) channels can be enumerated.  The drift line commonly is covered with organic debris.

Common Species

Zostera marina is found in some channels.  Common animals include chironomid (insect) larvae, the amphipods Corophium salmonis, Paramoera columbiana, and Eogammarus spp.; the polychaetes Hobsonia florida and Manayunkia aestuarina, the clam Macoma balthica, the shore crab Hemigrapsus oregonensis, tanaids, and mysids. Fishes found in channels include fry of chum, coho, and pink salmon, three-spined stickleback, starry flounder, and staghorn sculpin.

Sites Surveyed

Skagit flats, coastal estuaries.


Congleton, 1978; Smith, 1980; Simenstad, 1983; C. Staude unpubl. data.