EFFECT OF SMOLT SIZE ON SMOLT-TO-ADULT SURVIVAL FOR CHILKO LAKE SOCKEYE-SALMON (ONCORHYNCHUS-NERKA)

Three approaches were used to test the hypothesis that smolt-to-adult survival is independent of smolt size for Chilko Lake sockeye salmon (Oncorhynchus nerka). The mean distance between the focus of the scale and the first annulus, a reliable indicator of smolt size, was greater for adult scales than for smolt scales from the same brood year in two of the three years we examined. This indicated a higher smolt-to-adult survival for larger smolts in these brood years. The abundance of smolts of different fork lengths, based on back-calculation procedures from adult scales, was compared with the abundance of smolts of different fork lengths at the time of outmigration within brood years. In all three years studied, there was a two- to threefold increase in smolt-to-adult survival as smolt length increased. However, there was no significant relationship between smolt-to-adult survival and mean annual smolt fork length based on a 34-yr time series; this lack of relationship was probably caused by limited variation in mean annual smolt fork length over the 34-yr period and other variables, independent of smolt size, that affect survival and exhibit considerable interannual variation,