FISHERY BULLETIN: VOL 77. NO. 3 



STRAIT OF GEORGIA 



KILOMETERS 



Figure 2. — Map of the Nanaimo area, Vancouver Island, show- 

 ing the locations where beach seine and purse seine sets were 

 made for juvenile chinook salmon (circled numbers). 



locations ( 1, 2, 4, 5, 8, 9, 15, 16, 17; Figure 2) were 

 sampled during the second and third week of May 

 by beach seine! 18 x 3 m). Twelve locations! 1,2,5, 

 6, 7, 8, 9, 10, 11, 13, 15, 17; Figure 2), were sampled 

 weekly from March to July by hand-hauled purse 

 seine (90 x 7 m). Sixteen locations ( 1, 2, 3, 4, 5, 6, 

 7a, 8, 9, 10, 1 1, 12, 13, 2 1, 22, 23, 24; Figure 2) were 

 sampled weekly from April to July by drum seine 

 !216 ■' 18 m), except locations 21-24 which were 

 sampled at 2-wk intervals from late May until 

 early July. In 1976 seven locations !1, 2,4,5, 6, 16, 

 17; Figure 2) were sampled weekly from April to 

 June by beach seine. Ten locations II, 2, 4, 5, 6, 

 7a, 10, 23, 24, 27; Figure 2) were sampled by drum 

 seine weekly from early April until the end of 

 July, then approximately monthly until March 

 1977. In 1977, Area 10 was sampled weekly from 

 late April to late August by the 90 m hand-hauled 

 purse seine. 



Sample Processing 



Fork length and weight of preserved fish were 

 measured in all years, and in 1976 and 1977, 

 stomach analyses were also performed. The 

 lengths offish in small catches at sea were occa- 

 sionally measured at the time of sampling and the 

 fish released. This was especially true of early 

 catches in 1975. In 1977, fish captured by the 

 hand-hauled purse seine in Area 10 were all mea- 



sured for length, and a subsample of 15-20 was 

 preserved for weight and stomach analyses. Scales 

 of some of the preserved fish from both 1976 and 

 1977 were examined under 20 » magnification to 

 determine age structure of the catch. Preserved 

 samples were sometimes not analyzed until weeks 

 or months after capture so preserved weights are 

 likely to overestimate live weights. Length, how- 

 ever, is only slightly affected by preservation 

 ! Parker 1963). 



Wet weights of the stomach contents of indi- 

 vidual fish from the intertidal area of the estuary 

 were measured in 1975. Sample size was small 

 except for the 9 May sample !see Table 6). In 1976 

 and 1977, dry weight of the stomach contents of 

 10-20 fish from the estuary and a similar sample 

 from off the estuary was recorded each week and 

 converted to percent of body weight by assuming 

 that preserved fish were 20^? (average of >20 de- 

 terminations) dry matter. 



Detailed taxonomic analysis of stomach con- 

 tents was not made. However, in 1976 and 1977 

 the dominant components of the stomach contents 

 of each sample were recorded. 



DESCRIPTION OF STUDY AREA 



The Nanaimo River discharges into the Strait of 

 Georgia just south of the City of Nanaimo on the 

 east coast of Vancouver Island (Figure 2). It sup- 

 ports spawning populations of chinook; coho, O. 

 kisutch; and chum, 0. keta, salmon as well as 

 steelhead, Salmo gairdnerii, and cutthroat trout, 

 S. clarki. Since 1950, chinook salmon escapement 

 has averaged 2,100 spawners, and there has been 

 a gradual decline in abundance from 3,700 spawn- 

 ers between 1950 and 1954 to 1,400 between 1972 

 and 1976 (Aro^; Canada, Fisheries and Marine 

 Service'"). Adult chinook salmon enter the river 

 between April and October, and spawn from Sep- 

 tember to November ( Aro see footnote 9). In 1974, 

 1975, and 1976 (the brood years reported in this 

 study) escapement was estimated to be 2,400, 525, 

 and 1,100 respectively. 



The delta estuary of the river occupies about 9 

 km^ of which about 6 km^ is intertidal mud flat 

 (Figui-e 1). At the southern margin ofthe delta the 



'Aro, K. V. 1973. Salmon and migratory trout of the 

 Nanaimo River and adjacent streams (Revised 1973). Fish. 

 Res. Board Can. Manuscr. Rep. 1284, 15 p. 



'"Amiua! stream bank estimates of spawning escapement 

 available from Fisheries and Oceans. Canada, Field Services 

 Branch, 1090 West Pender Street. Vancouver, B.C.. 



656 



