Group = experimental group, defined by the strain(s) of the mother and the father, where Resistant = both parents resistant, Sensitive = both parents sensitive, Hybr = hybrids (SxR: sensitive father and resistant mother; RxS: resistant father and sensitive mother) and Unknown = both parents unknown. Couples = initial number of L. salmonis couples from each group; maximum number of potential families. Egg strings = number of egg string pairs incubated from each group, differ from ‘couples’ if the female was lost during the experiment or did not carry egg strings. No hatching = number of egg string pairs that did not hatch within 11 days in incubation. Hatchlings excluded = number of groups of hatchlings containing few, or inactive, copepodids (rejected from further use in the experiment). No male = number of families excluded due to loss of the male in the single-tank. Families produced = number of families meeting the requirements for further use in the experiment. Single egg strings were also collected and incubated. *: one female carried only one single egg string. **: two females carried only one single egg strain each.