To explore the methylation altering effects of oil on developing fish, we exposed larval Cyprinodon variegatus to oil for 48 h and used immunoprecipitation coupled with high-throughput sequencing (MeDIP seq) to evaluate genome-wide methylation changes. Overall design: In this study, we sought to determine the genome-wide effects of oil exposure on the methylome of larval C. variegatus. To examine the persistence of altered methylation, organisms were exposed to oil for 48h, followed by 48h of depuration to allow stabilization of methylation patterns. We then used immunoprecipitation coupled with high-throughput sequencing (MeDIP seq) to evaluate genome-wide methylation changes.