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

We determined the effect of maturation on parr growth and smelt recruitment of Atlantic salmon (Salmo salar) stocked in Vermont tributaries of the Con necticut River. Both among and within tributaries, mature parr ranged betwe en 28 and 52% of the age-1 parr collected and up to 67% of the age-2 parr c ollected. Percent age-1 parr maturing in October-November was positively re lated 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 i ndividually tagged in June and recaptured in October showed immature parr e xhibited twofold greater individual growth than maturing parr. Smelt recrui tment was highly dependent upon state of maturity the preceding fall; fewer individuals that matured as parr recruited to smelt compared with pan: rem aining immature. Our study shows, over a broad spatial scale, that variatio n in incidence of maturation is largely explained by parr size among tribut aries and river reaches and, furthermore, empirically demonstrates a direct negative effect of maturation on parr growth and recruitment to smelt. Thu s, parr maturation is an important consideration for the enhancement and (o r) restoration of Atlantic salmon populations via stream stocking programs.