of stomachs for that species in the sample (Bowen 1983). The 

 percent by volume of each item (vl a ) was calculated by dividing 

 the total volume of each food type by the combined volume of all 

 food types. Where food items were too small to obtain individual 

 volumes accurately, the total volume of these items was divided 

 by the number of items in the sample. Volumes for each category 

 of food item were then summed and divided by the total volume to 

 obtain the percentage volume of that category in the sample. The 

 percent total numbers (pl a ) is the number of food items in a 

 given type expressed as a percentage of the total number of food 

 items of all types in the sample (Bowen 1983) . 



Core Sampling 



Core samples were removed from each of the six spawning 

 areas for substrate composition analysis. Ten core samples were 

 taken from each site with a standard six-inch corer. The samples 

 were taken randomly from the rifle only, on a transect across the 

 riffle and perpendicular to the flow, if the riffle was well 

 defined and large enough. Otherwise, the ten samples were taken 

 along a transect intersecting the entire stream at the spawning 

 area and perpendicular to the stream flow. Samples were taken at 

 even intervals, or approximately every one-tenth of the riffle or 

 stream width. 



After removing the sample from the corer, depth inside the 

 core and outside the core (stream depth at that position) were 

 measured using a meter stick. Water in the corer was then 



11 



