Marine mammal stranding patterns in northern California: Linking effort-controlled baselines and environmental drivers (2012-2023)

Author

• Allison Brie Lui, California State Polytechnic University, HumboldtFollow

Graduation Date

Spring 2026

Document Type

Thesis

Program

Master of Science degree with a major in Biology

Committee Chair Name

Dr. Dawn Goley

Committee Chair Affiliation

Cal Poly Humboldt Faculty or Staff

Second Committee Member Name

Dr. Julia Parrish

Second Committee Member Affiliation

Community Member or Outside Professional

Third Committee Member Name

Dr. Ho Yi Wan

Third Committee Member Affiliation

Community Member or Outside Professional

Fourth Committee Member Name

Dr. Susan Chivers

Fourth Committee Member Affiliation

Community Member or Outside Professional

Keywords

Marine mammal strandings, Carcass encounter rates, Northern California, Effort-controlled baselines, Baseline thresholds, Unusual mortality events, Generalized additive models, Marine heatwaves, Sea surface temperature annomalies, Harmful algal blooms, Habitat compression, Chlorophyll-a, Harbor seal, Harbor porpoise, California sea lion, Guadalupe fur seal

Subject Categories

Biology

Abstract

Marine mammal strandings are important indicators of population and ecosystem health, yet distinguishing between background and anomalous strandings remains challenging. Climate-driven changes in ocean conditions are expected to increase in frequency and intensity, further complicating the interpretation of baseline stranding patterns. Here, effort-controlled carcass encounter rates (carcasses/km) were used as a standardized index of stranding mortality for four species along 114 km of remote coastline in northern California (2012–2023). Focal species included two resident species, harbor seal (Phoca vitulina richardii) and harbor porpoise (Phocoena phocoena), and two migratory species, California sea lion (Zalophus californianus) and Guadalupe fur seal (Arctocephalus townsendi). Across species, 67 events exceeded baseline carcass encounter thresholds, with the majority of peaks occurring during extreme marine heatwaves, documented Unusual Mortality Events, and periods of seasonal abundance. Generalized additive models revealed nonlinear, species-specific responses to key environmental drivers, linking carcass encounter rates to sea surface temperature anomalies, productivity, habitat compression, and harmful algal blooms. These results demonstrate the utility of effort-controlled baselines and underscore the importance of standardized long-term monitoring programs in remote coastal areas to support evidence-based management and policy decisions.

Citation Style

APA

Recommended Citation

Lui, Allison Brie, "Marine mammal stranding patterns in northern California: Linking effort-controlled baselines and environmental drivers (2012-2023)" (2026). Cal Poly Humboldt theses and projects. 2546.
https://digitalcommons.humboldt.edu/etd/2546