Inheritance of bluesac disease for hatchery charr of the genus Salvelinus

Synopsis Bluesac disease is one of the major causes of post-hatching embryo mortality in salmonids. The incidence of bluesac is strongly inherited in splake (Salvelinus fontinalis × S. namaycush hybrid) under hatchery conditions. Lake charr, F₂ splake, F₆ splake, and lake charr backcrosses of F₆ splake had incidences of 7%, 23%, 5% and 40% respectively. For the backcrosses, which are of practical interest because they are used for experimental plantings in the Great Lakes and northern Ontario inland lakes, the variation among families in the incidence of bluesac is primarily determined by the splake parent. Hence the incidence of bluesac disease in the progeny of splake and lake chair is considered to be a character of the splake parent. The heritability of this character in the splake is about 0.74. The level of bluesac in the backcrosses can, therefore, be significantly reduced in one generation by selecting as breeders those splake that produce low levels of bluesac in test backcrosses to lake charr.