Response of coastal ichthyoplankton assemblages off northern California to seasonal oceanographic and climate variability

Author

Blair M. Winnacott, Humboldt State UniversityFollow

Graduation Date

Fall 2021

Document Type

Thesis

Program

Master of Science degree with a major in Natural Resources, option Fisheries

Committee Chair Name

Dr. Eric Bjorkstedt

Committee Chair Affiliation

HSU Faculty or Staff

Second Committee Member Name

Dr. Andrew Kinziger

Second Committee Member Affiliation

HSU Faculty or Staff

Third Committee Member Name

Dr. Jose Marin Jarrin

Third Committee Member Affiliation

HSU Faculty or Staff

Keywords

Ichthyoplankton, Trinidad Head line, Northern California, Climate variability, Sebastes spp., Marine heatwave

Subject Categories

Fisheries

Abstract

This study analyzed samples collected along the Trinidad Head Line (41°N) to characterize variability in the ichthyoplankton assemblage in coastal waters off northern California from late 2007 through 2019, a period during which a major marine heatwave (MHW; late 2014-16) strongly perturbed the ecosystem. I augmented visual identification with genetic techniques to resolve the species composition of visually cryptic larval rockfishes (Sebastes spp.). While taxonomic composition off northern California was largely similar to studies off Oregon and Washington, and cross-shelf structure and seasonal patterns in species’ abundance were generally consistent with the distribution and phenology of parental stocks, interannual variability in assemblage structure responded strongly to basin scale climate forcing. Specifically, a sharp and persistent increase in the overall abundance of larval fishes (despite declines in a few species with cool-water affinities) and species richness coincided with the unprecedented late 2014-16 MHW that manifested first with the arrival of the “Warm Blob” in coastal waters in late 2014 and was subsequently reinforced by a strong El Niño event in 2015-16. During this event, several rare or previously unrecorded taxa occurred in our collections. Our observations suggest onshore advection of larvae of oceanic species and reduced offshore dispersion of coastal species’ larvae, but the starkest changes in assemblage structure appear to be associated with poleward shifts in the spawning distribution of adult stocks marked by the appearance (at high abundance) of several species that typically spawn well to the south of our sampling region (e.g., Genyonemus lineatus, Merluccius productus, and Sardinops sagax). Resolving aggregate Sebastes to species highlights similar patterns, including the arrival of new species (e.g., Sebastes jordani) with the 2015-16 El Niño that would have otherwise gone undetected. These results lay the foundation for extending the use of larval fish assemblages as indicators of ecosystem responses to climate forcing in this important transitional region of the California Current.

Citation Style

Transactions of the American Fisheries Society

Recommended Citation

Winnacott, Blair M., "Response of coastal ichthyoplankton assemblages off northern California to seasonal oceanographic and climate variability" (2021). Cal Poly Humboldt theses and projects. 531.
https://digitalcommons.humboldt.edu/etd/531