Fish Habitat Characteristics Sample Clauses

Fish Habitat Characteristics. As described by Xxxxxx and Xxxxx (1994) and others, salmonids are highly responsive to changes in five variables: water supply, temperature, nutrients, LWD, and sediment. In this regard, the habitat is largely a function of the interaction of flowing water, sediment, and structures in stream channels and the adjacent riparian area. Stream channels encompass the area where water flows most of the time and the floodplain and former terraces above the bankfull channel margin that are sporadically inundated at higher flows. Along the river continuum from headwaters to lowland reaches, the terrestrial influences on the channel lessen as flow and sediment load increase and physical structures become less common (Xxxxxx and Xxxxxx 1991). • Steep, headwater channels are tightly confined by valley walls and shaped by bedrock, boulders, LWD, coarse sediments, and riparian vegetation. • Moderate to low gradient mid-reach channels are less confined and are shaped by bedrock, boulders, LWD, sediments, and riparian vegetation. At this point along the river continuum, the degree to which LWD forms and maintains channel features is often a function of gradient, with LWD-formed features more common in lower than steeper gradient reaches. • Lowland reaches have channels which commonly meander freely across floodplains of fine sediments and are shaped by scour and deposition at meander bends. Pools are seldom strongly influenced by bedrock, boulders, or LWD. Key interactions and variables of salmonid habitat are described below in terms of stream and channel features, riparian zone contributions, and other habitat factors.