Commercial broodstock programs are sometimes not able to effectively use genotyping to determine relatedness amongst individuals communally reared with all families in a year class. In such cases, families are held in individual tanks until such time that siblings are assessed and PIT tagged for identification before pooling within communal rearing tanks. This was the case for a n Atlantic salmon breeding program for Northern Harvest Sea Farms, now Mowi Canada East, which maintained families in individual tanks at the Huntsman Marine Science Centre for the 2010-2018 year classes .
Over this period, every effort was made to standardize environmental conditions amongst individual family tanks and recirculating systems, with a focus on density, feed/feeding, temperature, oxygen saturation, mg per liter of oxygen, pH, CO2 , alkalinity, total ammonia, nitrite, nitrate, and total gas pressure. It is imperative to ensure that the culture environment was not providing a performance advantage to specific families that might otherwise be attributed to the genetic capacity of the family siblings. However, conditions and parameters can vary over time and the effect on prevalence of deformities within tanks must be quantified . A comprehensive deformity/abnormality code was developed to collect robust data on 240,733 individual fish (ranging from 15,747-35,799 per year class) for 765 families (482 sires, 504 dams) within each of the nine year classes.
Progeny from the families of each year class were randomly
assessed and a portion PIT tagged when individuals reached a minimum size to make up the controlled challenge groups and future breeding nucleus. Atlantic salmon having any type of deformity or extreme abnormality were
assessed but not tagged. Skeletal deformities assessed included : short opercula, jaw, head and spinal curvature. Abnormalities or irregularities, such as eye abrasions , fin erosion etc., were also recorded but, in some cases, these individuals were still PIT tagged (e.g., slight fin erosion). These abnormalities were recorded as potential environmental effects that could be attributed to tank density or other factors and might impact prevalence or severity of deformity .
This presentation will discuss the deformity/abnormality coding used (e.g., effect of technician calling severity) , significance of environmental variables with attribution to differences in location of deformities, variation or lack thereof in percentages of deformities between year classes and over a generation(s), and estimated heritabilities of various deformities with discussion of the fixed and random effects (h 2 ± SE = negligible to 0.23±0.03 across all year classes evaluated).