Figure 2, --Metal fry trap used in enumerating pink and 

 chum salmon fry in Prince William Sound streams, 

 1957. 



On April 4, fishing began at Cannery Creek 

 (fig. 4) and Pigot Bay and continued until June 

 19. The first traps installed were submerged 

 by tides, and both installations were moved 

 upstream on May 18. 



On April 9, traps were installed at Whale 

 Bay (fig. 5). They were secured with a steel 

 cable and were placed about 30 feet down- 

 stream from a 10-foot bank of snow and ice 

 that completely covered the stream. The in- 

 stallation was removed on May 12 when it be- 

 came necessary to curtail activities because 

 of manpower limitations. 



Trapping began at Port Chalmers on April 

 10, and on May 22 the traps were moved about 

 150 yards upstream from the initial site. They 

 were fished in the new location until June 20. 



At Fish Bay traps were fished in one location 

 from April 13 through June 19. 



Ice in Beartrap Bay prevented establishing 

 a camp until April 27. Traps were installed 

 on that date and fished until May 17. 



Even though we assumed that pink and chum 

 salmon fry migrated only between 2000 and 

 0800 hours, all station attendants were in- 

 structed to operate traps continuously until 

 the migration pattern was determined, and 

 to check traps daily at 0100, 0800, and 2000 

 hours. Traps were fished for 24 hours a day, 

 except when they were being moved or cleaned, 

 or when the attendant decided not to fish for 

 brief periods because of high fry mortality 

 in the traps. 



Large amounts of debris washed into the 

 traps by the increased waterflows resulting 

 from melting snow and ice were responsible 

 for fry mortalities. Special attention was 

 necessary to keep the traps clean so as to 

 insure free flow of water through them. The 

 highest mortalities, which ranged up to about 

 25 percent of the fish taken, occurred atOlsen 

 Bay where streamflows were very high and fry 

 migrations large. Daily catches ran as high 

 as 8,279 during the peak of the run when traps 

 were lifted eight times a day at 25- to 3j-hour 

 intervals. 



Method of Estimating Migration 

 from Trap Catches 



The method of calculating total fry migration 

 from above the trap installation for each stream 

 sampled was as follows: 



where a= number of fry captured by traps at a 

 station, 



b = percent of fry captured by traps, 



c = percent of fry migration between 

 original installation date and dis- 

 mantling date, 



d - percent of time traps were not fished 

 while being cleaned, repaired, or 

 moved to a better location, 



T= estimated total fry migration from 

 above traps. 



