Aquaculture, 53 zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA (1986) 313- 320 Elsevier Science Publishers B.V., Amsterdam - Printed in The Netherlands 313 zyxwvutsrqp SELECTION AGAINST PARR MATURATION IN ATLANTIC SALMON RANSOM A. MYERS and JEFFREY A. HUTCHINGS’ Department of Fisheries and O ceans, P.O. Box 5667, St. John’s, New foundland AlC 5X1 (Canada) ‘Department of Biology, Memon’al University of Newfoundland, St. John’s, New foundland AlB 3X9 (Canada) (Accepted 25 August 1985) ABSTRACT Myers, R.A. and Hutchings, J.A ., 1986. Selection against parr maturation in Atlantic salmon. Aquaculture, 53: 313- 320. The feasibility of using scale characteristics to detect maturation as parr of anadromous male Atlantic salmon was examined. Smolt age and growth rate were found to be reliable indicators of prior maturation, whereas scale morphology did not differ between matura- tion phenotypes. Although determination of prior maturation was not 100% efficient, the resulting selection intensities would allow for effective artificial selection against anadromous males which had matured as Parr. INTRODUCTION Maturation of males prior to seaward migration is common among popula- tions of Atlantic salmon, Salmo salar. These small, “precocious” parr fer- tilize eggs in competition with large, anadromous males (Jones, 1959), and can stimulate anadromous females to spawn in the absence of anadromous males (Myers and Hutchings, 1986). Maturation of male parr can have major economic consequences. Increased mortality and delayed smoltifica- tion associated with parr maturation is responsible for the loss of 60% of the male salmon production in Newfoundland (Myers, 1984). As there is additive genetic variability for parr maturation (Naevdal et al., 1976), it would be advantageous to use anadromous males which had not previously matured as parr for broodstock. Selection could take place in hatcheries or when males ascend fishways if there was a method of determining whether males had previously matured. Scale characteristics of smolt (salmon undertaking their first seaward migration) were analyzed to assess the feasibility of using the “ river” zone of scales from anadromous males to identify individuals which had matured as parr. The usual method of determining prior maturation from scale analysis, by identification of spawning marks, cannot be used for deter- 0044-8486/86/$03.50 0 1986 Elsevier Science Publishers B.V.