Check Formation on the Scales of Hatchery-Reared Lake Trout Prior to and SoonAfter Release into Lake Superior

摘要

The authors investigated two assumptions about scales of hatchery-reared laketrout Salvelinus namaycush stocked as yearlings into Lake Superior: (1) only one check is formed during hathery life and (2) a 'stocking check' forms when the fish are released. The authors examined four scales from each of 176 fish prior to release from five hatcheries and 55 fish soon after release. Prior to release, 91% of the lake trout had only one check. This percentage was 81-100% for individual hatcheries. Evidence for a stocking check was observed only on fish whose scales had grown substantially between release and subsequent recapture. All measures of variability were less and check conspicuousness was greater for fish raised in hatcheries with seasonal cycles of temperature and photoperiod than for those reared wih nearly constant water temperatures and darkness. The authors conclude that the assumption of only one check prior to stocking was not grossly violated when several scales from the same fish were interpreted and that there was some evidence for a 'stocking check'.