Abiotic factors vary spatially and temporally in marine environments and during anomalous sea surface temperature events, marine food webs often experience significant changes through the food web. Highly mobile and abundant predators have demonstrated foraging responses to anomalous sea surface temperature events, and their responses can indicate the ecological impacts through the food web to such events; but studying mobile predators through extended periods of time is usually met with financial and logistical constraints. Salvaged vibrissae provide a cost-effective way to sample an individual once and collect a multi-year record of foraging. We opportunistically collected vibrissae of 25 dead female California sea lions from San Miguel Island, California USA. We sampled across the vibrissae in three-month increment segments and analyzed for stable isotopes of delta carbon (δ13C) and delta nitrogen (δ15N). We tested for trends through time and found significant decreases through years of δ13C intra-individual variability and δ15N; both of which had a negative relationship with sea surface temperature particularly on the regional scale at waters encompassing and adjacent to the rookery.