Effect of maturation on parr growth and smolt recruitment of Atlantic salmon

Kevin G. Whalen and Donna L. Parrish
Can. J. Fish. Aquat. Sci./J. Can. Sci. Halieut. Aquat. 56(1): 79-86 (1999)

Abstract: We determined the effect of maturation on parr growth and smolt recruitment of Atlantic salmon (Salmo salar) stocked in Vermont tributaries of the Connecticut River. Both among and within tributaries, mature parr ranged between 28 and 52% of the age-1 parr collected and up to 67% of the age-2 parr collected. Percent age-1 parr maturing in October-November was positively related to mean length the preceding June. In October-November, immature age-1 parr were greater in mean length than age-1 mature parr. Data from parr individually tagged in June and recaptured in October showed immature parr exhibited twofold greater individual growth than maturing parr. Smolt recruitment was highly dependent upon state of maturity the preceding fall; fewer individuals that matured as parr recruited to smolt compared with parr remaining immature. Our study shows, over a broad spatial scale, that variation in incidence of maturation is largely explained by parr size among tributaries and river reaches and, furthermore, empirically demonstrates a direct negative effect of maturation on parr growth and recruitment to smolt. Thus, parr maturation is an important consideration for the enhancement and (or) restoration of Atlantic salmon populations via stream stocking programs.