Effects of anthropogenic noise on marine mammal abundances informed by mixed methods

This mixed-methods study examined the decline of a Harbor Seal (Phoca vitulina) colony’s abundance in Pacific Grove, California, USA, documented by community scientists. We combined generalized additive modeling (GAM) of abundance trends from 2003 to 2023 with qualitative analysis of Local Ecological Knowledge (LEK) obtained through interviews. LEK identified various anthropogenic disturbances that may have contributed to the colony’s decline. Statistical analysis revealed that, in 2022 and 2023, Harbor Seal abundance was 29.81% lower than expected, given the availability of prey fish in their forage range. Notably, roadwork near the colony during the 2022 pupping season likely impacted reproductive success and reduced habitat suitability, potentially impacting abundance. This study underscores the demographic impacts of human disturbances on marine mammals, the effectiveness of mixed-methods and community science in ecological research, and the critical need to mitigate disturbances to protect sensitive marine mammal populations, especially during critical periods like pupping seasons.