FISHERY BULLETIN VOL. 77, NO. 1 



mately one-third of the total Leavenworth Hatch- 

 ery stock was marked. In each year except the 

 first, a circular net pocket with a metal sleeve and 

 a tub sampler were used to obtain a sample offish 

 for marking. Two types were employed: a 

 3-pocket sampler which gave an approximate 

 33.3'7( sample for marking, and a 10-pocket sam- 

 pler (Worlundetal, 1969; Wahleetal. 1974) which 

 provided a 10% sample for population estimate. In 



1961, the one-third sample was obtained by mark- 

 ing every third pond, and in the other 3 yr the fish 

 to be marked were selected as described above. 



In 1961, hatchery personnel marked 1,008,310 

 1960-brood sockeye by removing the adipose fin 

 (Ad) and part of the right maxillary bone ( RM). In 



1962, the 1961-brood fish (600,036) were marked 

 by removal of the adipose fin and part of the left 

 maxillary bone (LM). The 1962-brood fish 

 (1,146,485) were marked the same as the 1960- 

 brood, and the 1963-brood (606, .578) repeated the 

 1961-brood mark. 



In 1961 the marked and unmarked fish were 

 kept in separate ponds and mortality records kept 

 for each group. The number of unmarked fish for 

 release was estimated by using the number of eggs 

 and the percentage of hatch, and subtracting the 

 number marked plus pond mortality. As the fish 

 were stocked, in order to avoid bias, the marked 

 and unmarked fish were mixed in each truck load. 



In the three following years, by knowing the 

 actual number offish marked for each brood year, 

 and the postmarking mortality, the total popula- 

 tion at release time was estimated. Using the 10- 

 pocket sampler on a random group of fish from a 

 pond, a 10% sample was obtained. Repeating this 

 procedure on the 10% sample provided a 1% sam- 

 ple, and a Peterson index of sample size was calcu- 

 lated (Table 1). The fingerlings were transported 

 by tank truck and released into Lake Wenatchee 

 each fall. 



Table l. — Numbers of socke.ve released into Lake Wenatchee, 

 Wash., during marking program. 



'Ad - adipose fin; RM = rigiil maxillary bone, LM = left maxillary bone 



In the spring of 1962 and 1963, a trap was oper- 

 ated at the lake outlet to monitor the outmigra- 

 tion. Data obtained at the trap indicated that 



<50% of the marked fish migrated downstream. 

 This amounted to 38.4% of the marked fish of the 

 1960-brood and 47. 9^/^ of the 1961-brood. 



Marked Fish Recovery 



Sampling for returning marked adults began in 

 1964 and continued through 1968. Earlier returns 

 were not expected because prior studies at Lake 

 Wenatchee indicated that few, if any, adults would 

 return in their third year (Major and Craddock 

 1962). The search for marks was confined to the 

 two commercial fishing areas in the lower Colum- 

 bia River: zones 1-5, the gill net fishery below 

 Bonneville Dam, and zone 6, the Indian set net and 

 dip net fishery above the dam (Figure 3). Other 

 fisheries were not sampled as Columbia River 

 sockeye salmon rarely occur in the ocean commer- 

 cial catch and are seldom taken by sport anglers 

 (Koski 1964). 



We looked for marked fish during the commer- 

 cial seasons. The zone 6 catch was monitored at 

 Washington and Oregon Indian fishery buying 

 stations. Commercial canneries in the lower river 

 were sampled for the zones 1-5 gill net catch. Un- 

 fortunately for the study, the commercial gill net 

 season in zones 1-5 was closed in 1965 and 1966, 

 and opened only for 5 days in 1964 (Fish Commis- 

 sion of Oregon and Washington Department of 

 Fisheries 1968). The zone 6 catch was also limited 

 by this restriction, severely reducing the total 

 catch (see Table 4). The catch in the 7 yr previous 

 to the study averaged 90,900 fish. During the 

 study period the average was only 22,500 ranging 

 from 4,361 to 56,200 (Figure 4). 



Sampling Results 



Nearly one-half of the Columbia River commer- 

 cial sockeye salmon catch was inspected for marks 

 each year, except in 1966 when only a 4.2% sample 

 was obtai ned because of the erratic nature of 1 and- 

 ings. The extremely small sample undoubtedly 

 biased the estimation of catch for the brood years 

 involved. For most brood years, the majority offish 

 were caught in their fourth year (Table 2). For all 

 broods except the 1962 group an average of 94% 

 was caught at age 42 (4 - total age, 2 - seaward 

 migration age). This age-group represented only 

 4% of the total 1962-brood fish caught in 1966, 

 evidence that the age 4^ fish were almost entirely 

 missed by the fishery, although undoubtedly 

 available. 



234 



