

Figure 5.- -Fry trap installation at Whale Bay showing method of securing traps by cable, and spring snow 



conditions. 



The percent of the fry migration that the 

 traps captured was estimated by (1) measuring 

 the volume of water strained by the traps and 

 (2) determining the average percentage of 

 marked fry captured by the traps after release 

 in each stream. 



Streamflow studies. — Prior to thefieldwork 

 reported here, we assumed that fry drifted 

 downstream helplessly in the current and that 

 the percentage of fry migration taken in traps 

 would be directly relatedtothe volume of water 

 flowing through the traps. We also assumed that 

 the volume of water strained by traps in rela- 

 tion to total streamflow was the same as the 

 ratio of the total submerged trap area to the 

 stream cross-sectional area. 



To determine the validity of these assump- 

 tions, fry behavior in relation to traps was ob- 

 served, and water velocities were measured 

 with a Price Pigmy current meter at regular 

 intervals across the stream and within the 

 traps. The average velocity was determined 

 by using the 0.2- and 0.8-depth method. In 

 general, the assumptions were found to be 

 valid. 



Fry marking and recovery experiments: — 

 Pink salmon fry were anesthetized with 

 chlorobutanol, marked by clipping the dorsal 

 fin, and released about 150 to 250 feet above 

 the traps. Before their release marked fry 

 were held in the stream in boxes made of 

 screen (fig. 6) for several hours, and only 

 fry that appeared to be swimming normally 

 were released. Marked fry were released in 

 units of 500 and were distributed across the 

 stream. Repeated releases were made when 

 fry were available. 



Fry captured at the first trap lift after the 

 release were examined for clipped fins. A 

 few fish were placed in a glass jar, and the 

 clip marks were observed as the fish swam 

 around. Dead fish were also examined for clip 

 marks. 



Method of Estimating Abundance 

 in Intertidal Areas 



Studies of ways to enumerate fry in intertidal 

 spawning areas (fig. 7) did not start until late 

 in May, after most fry had emerged from the 

 gravel. In the preliminary phases it was 



