AN EVALUATION OF THE IMPORTANCE OF WITHIN-FAMILY SELECTION FOR JUVENILE GROWTH-CHARACTERISTICS IN ARCTIC CHAR

This study examined the relationship between the juvenile growth of pa rents and offspring in Arctic char (Salvelinus alpinus). The experimen tal design consisted of mating dams, classified as large-as-juvenile d arns (LJD) or as small-as-juvenile dams (SJD) 3 years before breeding, with pairs of sibling sires, one sire classified as a large-as-juveni le sire (LJS) and one as a small-as-juvenile sire (SJS) 3 years before breeding. The offspring of LJDs were significantly larger than the of fspring of SJDs on one of three dates (P = 0.0169 on day 150, 0.8899 o n day 250, and 0.0871 on day 350; N = 26 families on each date), and t he offspring of LJSs were significantly larger than those of SJSs on t wo of three dates (P = 0.1038, 0.0299, and 0.0155 for the same three d ates). At day 350, LJD X LJS offspring had mean weights and coefficien ts of variation of 72 g +/- 44%; LJD X SJS, 64 g +/- 52%; SJD X LJS, 5 9 g +/- 45%; and SJD X SJS, 56 g +/- 60%. Realized heritabilities (+/- SEs) ranged from 0.0502 (+/-0.0833) at day 350 to 0.253 (+/-0.179) at day 250 for dam effects, and from 0.220 (+/-0.106) on day 250 to 0.306 (+/-0.116) on day 150 for sire effects. In addition, the offspring of SJSs were more variable in size than the offspring of their sibling L JSs at a given mean weight. It is believed that selection for fast gro wth at an early age is a good strategy in breeding programs; however, programs should also include studies that identify parents that produc e desirable offspring. Growth differences between juvenile families co uld not be demonstrated to be related to the actual adult sizes of the parents or to the growth history of the parental families.