For some of the lakes where they are clipping, you might be able to tell exactly how old the fish are by how they were clipped:
http://www.gofishbc.com/r3.htm. In Roche lake for example you can tell the year and strain of trout from the type of clip it has. (Brian Chan was doing this on a WFN flyfishing show at Roche). For more detailed info though you have to use the fish wizard, but from it you can get detail like this:
Date Species Strain Genotype Stage Released Grams Mark
2008-05-09 Rainbow Trout PENNASK Diploid Yearling 14993 16.7 Right Maxillary
2008-05-09 Rainbow Trout PENNASK All Female Triploid Yearling 7496 14.7 Adipose
2007-05-07 Rainbow Trout PENNASK All Female Triploid Yearling 7500 12.8 Right Ventral
2007-05-07 Rainbow Trout PENNASK Diploid Yearling 15000 12.8 Adipose, Left Ventral
2006-06-28 Rainbow Trout PENNASK All Female Triploid Yearling 10000 4.2
2006-05-01 Rainbow Trout PENNASK Diploid Yearling 15000 11.8 Right Maxillary
2006-05-01 Rainbow Trout PENNASK All Female Triploid Yearling 7500 12.5 Adipose
2005-04-22 Rainbow Trout PENNASK Diploid Yearling 15000 12.3 Adipose, Left Ventral
2005-04-22 Rainbow Trout PENNASK All Female Triploid Yearling 7500 14.3 Adipose, Right Ventral
2004-06-24 Rainbow Trout BLACKWATER R Triploid Yearling 5000 22.8
2004-05-04 Rainbow Trout PENNASK All Female Triploid Yearling 7500 10.7 Adipose
2004-05-04 Rainbow Trout PENNASK Diploid Yearling 15000 12.5 Right Maxillary