Modeling embryo survival: Genetic and environmental influences on eye-up rate

Authors: Legacki, Erin; Peterson, Brian; Milligan, Melissa; HALLI, BAIR - University Of Maine; Delomas, Thomas; Cross, Gretchen

Submitted to: Aquaculture
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2024
Publication Date: 8/14/2024
Citation: Legacki, E.L., Peterson, B.C., Milligan, M.T., Halli, B., Delomas, T.A., Cross, G.U. 2024. Modeling embryo survival: Genetic and environmental influences on eye-up rate. Aquaculture. 595. Article 741461. https://doi.org/10.1016/j.aquaculture.2024.741461.
DOI: https://doi.org/10.1016/j.aquaculture.2024.741461

Interpretive Summary: Abstract The U.S. Department of Agriculture–Agricultural Research Service National Cold Water Marine Aquaculture Center (NCWMAC) in Franklin, Maine maintains a North American Atlantic salmon breeding selection program focused on improving commercially important traits. However, the program has experienced a significant decline in the percent of eyed embryos over the 14 years of operation. NCWMAC staff have been collecting data on eye-up percentage, pedigrees, and water quality parameters may offer answers to this decline. This massive data set was used to determine the genetic x environmental factors effecting the declining eye-up rates of North American Atlantic salmon on the east coast of the United States. In specific the aims are to 1) model the eye up rate as a heritable trait utilizing pedigree data and 2) correlate eye-up rate with external environmental parameters. Counts of eyed embryos and parentage pedigrees were fit to a maternal trait model to determine the heritability estimates for eyed embryo percentage. Additionally, water quality parameters collected over the same 14 year time period were correlated with the percentage of eyed embryos to determine environmental factors. Overall, the model indicated that the decrease in eyed embryos over time was not a result of genetic selection but, instead due to increases in water temperature and water nitrogen concentrations in the systems. Further work into the biology behind these environmental induced decline and mediations to prevent decline are needed.

Technical Abstract: The U.S. Department of Agriculture–Agricultural Research Service National Cold Water Marine Aquaculture Center (NCWMAC) in Franklin, Maine maintains a North American Atlantic salmon breeding selection program focused on improving commercially important traits. However, the program has experienced a significant decline in the percent of eyed embryos over the 14 years of operation. NCWMAC staff have been collecting data on eye-up percentage, pedigrees, and water quality parameters may offer answers to this decline. This massive data set was subjected to a maternal trait model of inheritance to determine the genetic x environmental factors effecting the declining eye-up rates of North American Atlantic salmon on the east coast of the United States. In specific the aims are to 1) model the eye up rate as a heritable trait utilizing pedigree data and 2) correlate eye-up rate with external environmental parameters. Counts of eyed embryos and parentage pedigrees were fit to a maternal trait model to determine the heritability estimates for eyed embryo percentage. Additionally, water quality parameters collected over the same 14 year time period were correlated with the percentage of eyed embryos to determine environmental factors. The direct genetic effect had a small heritability (0.059 ± 0.009) as did the maternal genetic effect (0.039 ± 0.013). Comparatively, the maternal environmental effect accounted for a moderate amount of the phenotypic variance (0.165 ± 0.012). The percent of eyed embryos were negatively correlated with yearly unionized ammonia (mg/L, -0.56, p = 0.04,), nitrate concentrations (mg/L r= -0.65, p=0.01) and temperature (°C, r = -0.61, p = 0.02). Overall, the model indicated that the decrease in eyed embryos over time was not a result of genetic selection but, instead due to increases in water temperature and water nitrogen concentrations in the systems. Further work into the biology behind these environmental induced decline and mediations to prevent decline are needed.