FISHERY BULLETIN: VOL. 77, NO. 3 



raises the question: What proportion of the fry 

 population migrates out of the Nanaimo River 

 each year? Information on sex and age of the 1974 

 and 1975 spawning population in the Nanaimo 

 River is not available so egg deposition can only be 

 surmised. If one assumes, however, that of the 

 2,400 escapement in 1974, 800-1,000 were 

 females, and that of the 525 spawners in 1975, 

 200-225 were females, and that the fecundity of 

 Nanaimo River chinook salmon is in the range 

 6,000-8,000 (Godfrey'-''; Schutz'-*), then potential 

 egg deposition in 1974 was on the order of 6-6.5 

 million, and in 1975 on the order of 1.2-1.6 million. 

 (The female population was estimated to be <50% 

 of the escapement because of the "jacks.") In the 

 winters of 1974 and 1975 there were no extreme 

 freshets, so survival was probably quite good, 

 perhaps as high as 15-207f (Lister and Walker 

 1966; Coots "^). Fry production may be estimated to 

 be, therefore, on the order of 0.9-1.3 million in 

 1975 and 0.18-0.32 million in 1976. These values 

 are similar to the estimated fry migration each 

 year and indicate that a high proportion of 

 Nanaimo River chinook salmon left the river as 

 recently emerged fry. 



9 16 23 30 6 13 20 27 4 II 18 25 I 8 15 22 29 6 13 20 

 MARCH APRIL MAY JUNE J(JLY 



Figure 4.— Catch of chinook salmon fry per beach seine set at 

 Stations 28-30 on the Nanaimo River estuary in 1975 (dots), 

 1976 (circles), and 1977 (triangles). 



Distribution and Relative Abundance of 



Chinook Salmon in the Estuary- 

 Sampling in the intertidal area of the estuary 

 revealed chinook salmon were abundant there in 

 spring and early summer of each year (Figure 4). 

 Juvenile chinook salmon were first captured at the 

 beginning of April 1975, were most abundant in 

 May, and had declined in abundance by early June 

 when sampling terminated (Figure 4). Chinook 

 salmon were captured from mid-March until late 

 July 1976 but increased in abundance later than 

 in 1975, and were generally less than half as 

 abundant as in 1975. Juveniles were already 

 abundant in the estuary when sampling began in 

 late March 1977 and reached maximum abun- 

 dance in early April, 3 wk earlier than in 1975 and 

 1976 (Figure 4). 



"Godfrey, H. 1968. Ages and physical characteristics of 

 maturing chinook salmon of the Nass, Skeena, and Fraser rivers 

 in 1964, 1965 and 1966. Fish. Res. Board Can. Manuscr. Rep. 

 967, 38 p. 



"Schutz, D. C. 1975. Rivers Inlet chinook sport fishery, 

 1971-1974. Environ. Can Fish. Mar. Serv. Tech. Rep. PAC/T- 

 75-9, 24 p. 



"Coots, M. 1957. The spawning efiBciency of king salmon 

 ^Oncorhynchus tskawytscha) in Fall Creek, Siskiyou County 

 1954-55 investigations. Calif. Dep. Fish Game, Inland Fish. 

 Branch. Inland Fish. Adm. Rep. 57-1:1-15. 



Greatest catches of chinook salmon were in the 

 east channel of the Nanaimo River and Holden 

 Creek. Catches in other stream channels crossing 

 the intertidal mud flat and along the delta front at 

 low tide were small by comparison. Catches in the 

 stream channels in the center of the mud flat aver- 

 aged only two fish/set, and on the west side of the 

 delta only one chinook salmon was captured in 

 eight sets. 



Catches across the delta front at low tide aver- 

 aged eight fish/set. At the same time catches in the 

 east channnel and Holden Creek averaged 20-40 

 chinook salmon, set. Catches along the edges of the 

 salt marshes at high tide were lower than in the 

 east channel in 1975, but of similar size in 1977. 

 Purse seine sets over the intertidal flats at high 

 tide, even near locations 29 and 30 where chinook 

 salmon were abundant at low tide, produced no 

 chinook salmon (Figure 1). 



Catches at Stations 28-31 in 1 976 and 1977 indi- 

 cated that the area of greatest concentration of 

 juvenile chinook salmon moved seaward along the 

 channel as the season progressed (Table 3). The 

 difference in time of maximum abundance be- 

 tween Station 31 and Station 28 was about 5 wk. 



Physical conditions during low tide at the sam- 

 pling stations along the east channel and Holden 



660 



