The body scale relationship for adult sockeye oncorhynchus nerka pink oncorhynchus gorbuscha chum salmon oncorhynchus keta and chinook salmon oncorhynchus tshawytscha
Canadian Technical Report of Fisheries and Aquatic Sciences 1353: I-IV, 1-19
The body-scale relationship for adult sockeye, pink, chum and chinook salmon of different ages, brood years and locations was examined. Generally, the correlation coefficients between fish length and total scale radius or total number of circuli for each age of each species were low, ranging from a low of 0.191 for age 1.3 sockeye to a high of 0.606 for age 0.3 chinook. Even when ages were combined, the correlation coefficients for sockeye, pink, and chum salmon remained low, ranging from a low 0.386 for pinks (length versus number of circuli) to a high of 0.571 for chums (length versus circuli). Only the correlation coefficients for chinook salmon were moderately high at 0.857 and 0.794 for length and scale radius, ane length and circulus number, respectively. Hence, with exception of the chinooks, only very gross estimates of prior growth of the other 3 spp. can be made from examination of their scales. The reasons for the low correlations may be associated with the fact that scale samples from adult sockeye, pink, and chum salmon caught in the net fishery near river mouths had begun resorption of their scales with the beginning of maturity. The chinook samples on the other hand, were mainly collected from troll caught fish sometime prior to the onset of the process of maturity, hence resorption of their scales probably had not begun to occur. This would account for the higher correlation coefficients. The lines of best fit describing the relationships for sockeye and pink salmon tended to change from one brood year to the next. Similar comparisons could not be made for chinook and chum salmon as only fish from one brood year were examined. Analysis of variance testing for differences in the regression lines for sockeye, pink and chum salmon from different locations indicated, in some cases, significant differences among fish from different locations. Such differences must be related to either genetic or environmental factors, or a combination of both.