Effects of winter temperature and feeding regime on the rate of early maturation in Atlantic salmon ( Salmo salar) male parr

Individually identified Atlantic salmon parr were submitted to different combinations of temperature and feeding regime during their first winter. These treatments were designed to test for causal relationships between winter growth, body lipid level in spring as measured by the condition factor, and subsequent maturation. Maturation was observed almost exclusively in the lower modal group (presumptive 2-year-old smolts). Large and significant differences in winter growth performance and condition factor in spring were observed among treatments. Some variation in the rate of male parr maturation was observed among treatments as well, but the differences were not significant. The pattern of growth and change in condition factor before male parr maturation were different from that which had been observed before grilse and post-smolt maturation. The results of this study suggest that the threshold for lipid storage which initiates male parr maturation might be very low, and male parr maturation is thus not very dependent upon winter growth and spring lipid storage level.