Date of Award

Fall 2016

Project Type


Program or Major

Natural Resources

Degree Name

Master of Science

First Advisor

Marian K. Litvaitis

Second Advisor

Yvette L. Garner

Third Advisor

Larry G. Harris


Heterozygote deficiencies have been noted in both wild and farmed populations of Mytilus edulis Linnaeus 1758, yet the underlying causes for this deficit remain unclear. This is especially surprising considering that advantageous fitness traits (i.e., increased fecundity, reduced basal metabolism, higher growth rate in farmed mussels) as well as decreased mortality under environmental stressors (i.e., air exposure, increased water temperature) are positively correlated with heterozygosity in these mussels. The dislodgement hypothesis states that more heterozygous mussels are migrating to the periphery of a rope culture or mussel bed to gain an energetic advantage where they become more susceptible to drop-off. To test this hypothesis, wild and farmed blue mussels were assessed for motility, size, byssal thread attachment strength, byssogenesis, and heterozygosity. There was no correlation between heterozygosity and byssal thread attachment strength or motility in wild or farmed mussels. Consequently, the dislodgement hypothesis is rejected. Instead, shell size was significantly correlated with several byssal thread variables. Size had a positive effect on attachment strength; larger mussels were more firmly attached to the substrate. Smaller mussels abandoned more plaques and produced more byssal threads than large mussels in the wild and farmed populations. Farmed mussels exhibited greater heterozygosity than wild mussels, possibly due to differences in predation risk, population density and size class. Neither heterozygosity nor size had significant effects on motility in either population.