Graduation Date
Spring 2024
Document Type
Thesis
Program
Master of Science degree with a major in Biology
Committee Chair Name
Dawn Goley
Committee Chair Affiliation
HSU Faculty or Staff
Second Committee Member Name
Paul E. Bourdeau
Second Committee Member Affiliation
HSU Faculty or Staff
Third Committee Member Name
Ho Yi Wan
Third Committee Member Affiliation
HSU Faculty or Staff
Fourth Committee Member Name
Christine Cass
Fourth Committee Member Affiliation
HSU Faculty or Staff
Keywords
Feeding ecology, Predator prey interaction, Marine mammals, Marine invertebrates, Home range
Subject Categories
Biology
Abstract
As opportunistic foragers, the Eastern North Pacific population (~20,000) of gray whales (Eschrichtius robustus) feed on diverse benthic and planktonic invertebrates in northern Alaska foraging grounds before they undertake one of the largest yearly migrations of any mammal to breed in Baja California, Mexico. While most of the population travels to the summer foraging grounds in Alaska, a sub-group of whales (~230) called the Pacific Coast Feeding Group (PCFG) summer between British Columbia, Canada, and northern California. The diet of PCFG whales typically includes high-density and/or high-caloric prey items like mysids and diverse species of amphipods, yet a few studies reported from northern California show evidence of whales foraging for a different relatively low-density invertebrate prey community. I observed gray whale frequency in northern California by conducting weekly land-based and monthly boat-based surveys across four known PCFG foraging locations from May to December 2022 and April to December 2023. Further, I concurrently assessed PCFG prey quality and quantity in northern California by systematically and opportunistically (in the presence of foraging whales) collecting planktonic and benthic prey species at these four locations. I confirmed that gray whales continue to use northern California as the southern edge of their summer foraging range, and found that these whales consume relatively low quantity and quality planktonic and benthic prey, primarily made up of porcelain crab larvae and the cumacean Diastylopsis dawsoni, respectively. Future data collection is needed to determine any long-term patterns in PCFG distribution and potential changes in prey variability in northern California, especially under the threat of rapid environmental change.
Citation Style
APA
Recommended Citation
Norman, Robyn E., "Characterizing the habitat use of Pacific Coast Feeding Group gray whales (Eschrichtius robustus) and the spatial and temporal variability of their benthic and planktonic invertebrate prey in Northern California" (2024). Cal Poly Humboldt theses and projects. 745.
https://digitalcommons.humboldt.edu/etd/745