HEALEY: UTILIZATION OF THE NANAIMO RIVER ESTUARY 



Table 3. — Catch of juvenile chinook salmon per beach seine set at different points 

 along the east channel of the Nanaimo estuary during 1976 and 1977. Station locations 

 are shown in Figure 1. 



Creek varied considerably with season in 1977. 

 Temperature ranged 9.5°-26.0' C and salinity 

 2-24%o (Table 4). In general, temperature in- 

 creased at all stations from April through June, 

 but this was strongly influenced by variations in 

 river discharge and weather conditions on the day 

 of sampling. Salinity increased throughout the 

 season, but was also dependent on river discharge 

 and local conditions. Large, local variation in 

 physical conditions was indicated by measure- 

 ments of temperature and salinity at two locations 

 at Stations 28 and 30 in May and June. At Station 

 28 a small steam channel joined the main east 

 channel. Temperature of the river above where 

 this stream entered was usually lower, and on one 

 occasion 4.5° C lower, than below the entrance. 

 Salinity above the entrance of this stream channel 

 was sometimes higher and sometimes lower than 

 below the entrance, the greatest observed differ- 

 ence being 6%i, (Table 4). At Station 30. Holden 

 Creek joined the east channel of the river. The 

 river was usually cooler than Holden Creek, al- 

 though on one occasion it was warmer, and salinity 

 of the river was usually lower than Holden Creek. 

 Temperature and salinity values reported, there- 

 fore, should be taken as indications of the kind of 

 conditions in which the fish lived at low tide, with 

 considerable latitude for selection by the fish. 



The appearance of juvenile chinook salmon in 

 the intertidal area of the estuary was coincident 

 with the buildup of the downsteam run and the 

 rate of increase in catch on the estuary was similar 

 to the cumulative increase in the number of 

 chinook salmon which had moved downstream. In 

 both 1975 and 1976 the estuary population con- 



TaBLE 4.— Temperature (° C) and salinity (%o) at sampling loca- 

 tions for juvenile chinook salmon on the Nanaimo estuary dur- 

 ing 1977. Station locations are shown in Figure 1. 



'Upper measurement above small tributary, lower below small Inbutary 

 'Uppef measurement in Holden Creek, lower m mam river channel 



tinued to increase after the peak in the down- 

 stream run. These observations indicated that the 

 fry which migrated downstream remained in the 

 estuary for some time. 



At low tide the chinook salmon population in the 

 estuary was clearly concentrated in the east chan- 

 nel of the river and Holden Creek. Some juveniles 

 were found in stream channels crossing the center 

 of the mud fiat, and some also found their way 

 down to the delta at low tide. The channels cross- 

 ing the western side of the mud flat, however, were 

 little used by juveniles. 



With the incoming tide the chinook salmon 

 moved to the landward margin of the mud flat and 

 at high tide were found in scattered schools all 



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