Traits
Individual body weight data at 10 months (BW10; 295 d ± 18.8) and 13 months (BW13; 386 d ± 12.9) post-hatch were recorded as part of the selective breeding program (Leeds et al., 2016) and were available from 2002 to 2014 (Table 1).
Table 1  Number of observation (n), mean, standard deviation (SD), and coefficient of variation (CV, %) of the analyzed traits and weight at harvest.
Trait   Acronym   Trait type   N   Mean   SD   CV (%)
10-month BW, g  BW10  Biometric  17,174  416.5  153.7  36.9
13-month BW, g  BW13  Biometric  15,810  896.3  328.8  36.7
Weight at harvest, g  Co-variable  Biometric  1447  1472.7  438.4  29.8
Eviscerated BW without head, g  CAR  Biometric  1445  1122.9  336.6  30.0
Weight of fillet, g  FW  Biometric  1447  739.4  235.2  31.8
Weight of fillet/Weight at harvest (%)  FY  Yield  1447  49.82  2.7  5.4 Five fish from each 2010, 2012, and 2014 year class full-sib family were identified for characterization of FY. The aim was to sample fish that represented the range of body weights within each family, with the exception that the largest and smallest fish from each family were excluded. Most families had 15 fish available for sampling at 13 months of age (range = 8–17 fish per family). Thus, to identify fish for FY characterization, the dataset was sorted by family and in descending order of body weight and every 2nd or 3rd fish was selected so that the distribution of body weights was uniformly centered around the median of the family. Selected fish were assigned to one of five harvest groups each generation (~100 fish per harvest group) with the aim of having one fish per family per harvest group. One harvest group per week was processed in each of five consecutive weeks, with the exception that year class 2012 fish were harvested over a 6-week period due to scheduling conflicts. Fish were taken off feed 5 days before harvesting. Fish were harvested between 410 and 437 days post-hatch (mean body weight = 985 g; SD = 239 g), between 446 and 481 days post-hatch (mean body weight = 1803 g; SD = 305 g), and between 407 and 435 days post-hatch (mean body weight = 1617 g; SD = 255 g) for the 2010, 2012, and 2014 hatch years, respectively. At harvest, fish were euthanized using a lethal dose of tricaine methanesulfonate (Tricaine-S, Western Chemical, Ferndale, WA), weighed, eviscerated, and placed on ice overnight. The next day, carcasses were beheaded, weighed, and hand-filleted by a single, experienced technician. The same technician filleted all fish from the 2010 and 2012 year class families, and a different technician filleted all fish from the 2014 year class families. Fillet weight was recorded as the sum of both fillets for each fish; fillet weights excluded the skin in 2010 and 2012 year class families but included skin in 2014 year class families. A summary of the records available, mean, standard deviation and coefficient of variation for each trait is presented in Table 1.