RELATIONSHIPS AMONG SMOLT SIZE, MARINE GROWTH, AND SEA AGE AT MATURITY OF ATLANTIC SALMON (SALMO-SALAR) IN NORTHERN SPAIN

Scale analysis indicated that two-sea-winter (2SW) Atlantic salmon (Sa lmo salar) had a greater growth increment during the first year at sea than 1SW of the same smelt year in the Rivers Narcea and Esva, but no differences were found between sea age-classes in the River Cares. In terannual variation in marine growth was synchronized among rivers. Va riation among years was greater than variation between sea age-classes , suggesting that marine growth per se does not determine age at matur ity. In the River Narcea, 2SW salmon were larger than 1SW at the end o f the first marine period, but differences between sea age-groups were not significant in the other two rivers. Some of this variability cou ld be attributed to differences in size at smelting; for two rivers (E sva and Cares), 1SW salmon had been larger as smells than 2SW salmon. Length increment during the first marine growth period was inversely c orrelated with smelt size (age-1 smelts); in spite of that compensator y effect, large smelts tended to maintain their size advantage at the time of formation of the first marine annulus, as indicated by positiv e correlations between smelt size and length at the first sea winter.