Date of Award

Summer 8-2023

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)


Ocean Science and Engineering

Committee Chair

Dr. Eric Saillant

Committee Chair School

Ocean Science and Engineering

Committee Member 2

Dr. Eric Powell

Committee Member 2 School

Ocean Science and Engineering

Committee Member 3

Dr. Bill Walton


Summer mortalities in Gulf of Mexico eastern oysters have been linked to excessively high temperatures, and chronic exposure to low salinity. In this study, the feasibility of improving tolerance to these two stresses by selection was evaluated in common garden experiments employing a pool of 160 families. Heat stress tolerance was evaluated in seed (3.5 months) and adults (14 months) by applying a sustained temperature of 38-39 °C until all oysters expired. Low salinity challenges on juveniles (9 months) and adults (15 months) applied a salinity of 2.5 psu. Survival duration of individual oysters during challenges was recorded and tissue samples were taken for genotyping and parentage assignment. The condition index was recorded at the end of the juvenile salinity challenge.

Parentage was recovered using a 192 SNP array and the heritability (h2) of tolerance traits and genetic correlations were estimated using linear mixed models. Heritability of heat stress tolerance in seed was low and did not differ significantly from zero (0.216±0.199). Heat stress tolerance in adults and condition index in juveniles were both heritable (h2 estimates 0.749±0.086 and 0.275±0.096 respectively). The estimate of heritability of salinity stress tolerance in adults was intermediate (0.326±0.274) but did not differ significantly from zero. Significant genetic correlations were estimated between seed and adult heat stress tolerance (0.672±0.205), and between adult salinity and adult heat stress tolerances (0.418±0.165). Additional studies are needed to understand the mechanisms of tolerance to heat and salinity stress and develop reliable early predictors of breeding values for these traits.

Available for download on Saturday, June 21, 2025