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<br />o C 08- " <br />II ',I j .!u <br /> <br />DKAi~ j' <br /> <br />FINAL DRAFT. 12/~0/91 <br /> <br />flow should o,"cur during or shortly after fry emergence whkh might strand the fry in <br />isolated pockets of water along the stream banks. <br /> <br />Succe<;.sful rcaring of juvenile !ish is dependent on adequate cover for pwtection from <br />predators. including larger fish. and on the availability of areas with relatively low velodties. <br />su..:h as areas of shallow water along the edges of the channel. As the fj",h grow and can swim <br />in Ill~h~r ,..:Il'';!'!'':;; th..:~ ,"'ill mu.e intv str0n:;er ..:urr..:nb where fe~in; is t.e:~er. A. this <br /><;f;ll;c. the hahitaf Jvailahle III iuvenile Ihh depends nn the aml'um and type of ,;cwer wmhined <br />with the abIlity to escape predation (~teehan. 1991). ~fore fish can occupy a given area and a <br />variety of age classes can coexist if they can not see ea.::h other. Vegetation. woody debris. <br />boulders. and turbulent water provide this type of cover by limiting sight distance. <br /> <br />Maintenance of the numbers of adult fish is largely determined by recruitment of young fish <br />into the adult age classes. Therefore. the instream flow levels and processes which meet the <br />requirements of the critical life stages described above will also ensure the adult component of <br />the fish population. <br /> <br />Adult fish are present in the mainstem and some of the tributaries year-round. Adult trout and <br />other large species require large. deep pools and glides. The pools are used for resting and <br />cover throughout the range of Hows. Glides and the deeper riffles provide feeding areas and <br />living space for less dominant or less competitive fish. Cover provided by houlders. rock <br />ledges. large wood debris and debris darns is also an important aspect of adult habitat. <br /> <br />Macroinvertebrates are animals without backbones which can be seen with the naked eye. <br />Aquatic macroinvertebrates include annelids, crustaceans, flatworms, mollusks. and <br />insects. Aquatic insects play an important ecological role as the link between the sources <br />of primary production, such as algae, riparian vegetation, and other organic material, and <br />fish. Some species are filter feeders, and others are predators (MacDonald et aI, 1991). <br />Some species graze on algae and on terrestrial organic material which falls or is washed <br />into the stream. Deciduous riparian vegetation is an important component of their food <br />base. Alder leaves decompose faster than most other streamside vegetation and are easily <br />colonized by microorganisms that are themselves the food supply for some aquatic insects. <br />Therefore, alder plays an important role in the primary production of the ecosystem. <br /> <br />Based on systematic sampling in 1988 and 1989 plus observations in 1991. there is <br />currently a wide variety of aquatic insects with a variety of feeding habits and habitat <br />requirements in the Piedra River. Mayflies, caddisflies, and slOneflies are the primary <br />food sources for all the fish species in the Piedra River. Members of these groups prefer a <br />mix.ture of coarse sands and gravels (Meehan, 1991) and will not survive in embedded or <br />sl;!diment covered substrates. Stoneflies such as the species Pteronarcvs californica and <br />L1aasenia sabulosa are used as ind ,!.tors of ~ological quality; both species are present in <br />the Piedra. These two species are important in the trout diet because they have two to <br />three year life cycles and provide a food source during the winter when other insects are <br />not available (1o.fangum. 1990). Accumulation of fine sediments in and on the substrate <br />would reduce the abundance of aquatic insects and would have ramitications in the entire <br />food chain. <br /> <br />Page 10 <br />