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<br />9 <br /> <br />METHODS <br /> <br />Fish microhabitat <br /> <br />.. <br /> <br />Microhabitat definition <br /> <br />Microhabitat of fish is normally considered to be those' phy- <br />sical (and occasionally chemical or biological) variables which <br /> <br />define the precise location occupied by a fish, and which would <br /> <br />or could change with small changes in a fish's location. <br /> <br />Microhabitat is usually used in this paper to refer to those var- <br /> <br />iables which appear to be used by the fish in determining its 10- <br /> <br />cation. VariabJes which are normally constant over a large por- <br /> <br />tion of a fish's environment (such as flow level, temperature, <br /> <br />conductivity, etc.) are considered macrohabitat variables, and <br /> <br />were not measured in this study. Determination of a species' mi- <br /> <br />crohabitat preferences is limited to our human ability to con- <br /> <br />ceive of and m~~sure variables important to a fish. <br /> <br />Observation technique <br />A modified scuba method was used to observe fi sh (Gosse and <br /> <br />Helm 1979, Gosse 1981, Gosse and Helm 1982). The diver wore an <br /> <br />I <br />I <br /> <br />exorbitant amount of weight to facilitate remaining stationary on <br /> <br />the stream bottom in the strong currents. The diver moved in an <br /> <br />~ J <br />l' <br />"~I <br />I <br /> <br />upstream direction to approach the fish from below and behind. <br /> <br />A surface~to diver sonic transceiver allowed the diver to <br /> <br />! <br />i <br />b <br />" <br />I <br />" <br />!" <br />, <br /> <br />communicate with the surface personnel. Variables that could be <br /> <br />measured by the diver without assistance were relayed to the sur- <br />