Eggs are an essential catalyst to a successful Atlantic salmon aquaculture operation. Embryo survival sets the bar for onsite productivity, fuels local conservation initiatives through multiplier eggs, and provides revenue for the regional aquaculture economy. The USDA’s National Marine Cold Water Aquaculture Center (NMCWAC) located in Franklin, Maine, houses the largest applied S. salar selective breeding program in the United States. The NMCWAC operates with the goal of genetically improving N. American lines of S. salar for aquaculture production. Throughout the past 20 years embryo survival has trended downward, where the USDA could rely upon 85% survival in 2009, reducing to survival of 22.7%, and 17.8% in the years of 2021, and 2022, respectively. Embryo survival is accessed at the point of “eye up” a developmental benchmark, by which the retinal pigment is visible through the chorion. Embryo’s that have reached eye up were successfully fertilized, cleaved, undergone gastrulation, and completed epiboly, thus being less vulnerable to handling.
While accessing viability at eye up offers ease, we lack a true understanding of ceased development prior to this benchmark. Our pilot study revealed reduced survival during stages of mid-late somitogenesis, and vascularization of the vitelline plexus. To further undercover the etiologies of mortality morphometrics tightly linked to developmental state were captured throughout S. salar embryogenesis. A suite of growth metrics; total length, eye diameter, yolk- sac volume, and egg diameter were collected. While physiological morphometrics of percent vascularization, and heart development were tracked to establish a metric that may be indicative of subsequent development, or cohort success. Following the morphological and physiological shifts throughout critical stages in S. salar development will undercover the etiologies of reduced survival while simultaneously defining a suite of morphometrics that inform a biomarker indicative of broodstock success.