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<br />;)iI::l8d9 <br /> <br />DRAt'1' <br /> <br />FINAL DRAFT - 12/19/91 <br /> <br />. Aquatic insects are the primary food source for fish. Organic material, including that from <br />vegetation. is the base of the aquatic food chain. The amoum and type of organic material <br />determines the productivity of the microorganism and aquatic insect communities . <br />Riparian vegetation is a key component in the lifecycle of aquatic imects <br />. Winter survival of fish and aquatic insects depends upon maintenance of pool and glide <br />depths and upon sufficient velocity to limit ice formation and to maintain oxygen <br />concenuarions in the water column. in roods. and in interstitial substrates. To prevent <br />desiccarioD of brown and brook trout eggs, streamflow should be m.aintalned at levels <br />which occur naturally during the winter low flow months. <br />. Survival of juvenile fish is in part determined by the availability of adequate rearing babitat <br />provided by areas of shallow water near the edge of the stream channel. <br />. The tributaries to the Piedra River are important as spawning babitats for both trout and <br />native species; therefore, there must be adequate water depths in both the tributaries and <br />the Piedra to maintain migration access during spring and fall spawning periods. Flows <br />must be of sufficient volume and duration to prevent the accumulation of organic or <br />inorganic debris which would binder or bloclc passage at the mouths of these tributaries. <br />. The late summer and fall increases in runoff are imponant for flushing trout fry from the <br />tributaries into the mainstem of the river. These peaks also move addition.1l organic <br />material such as alder and willow leaves into the system. <br />. In addition to meeting the annual biological and functional requirements of fish and aquatic <br />insect!, their habitat must be maintained over the long term. Removal of fine sediments, <br />rearrangement and recruitment of spawning gravels and woody debris. maintenance of <br />pool/riffle/glide sequences, and maintenance of effective pool size and depth may be <br />dependent upon flows of sufficient volume and duration to transpon organic and inorganic <br />debris. <br /> <br />Page 12 <br />