Carbon and nitrogen isotopes of different native fish tissues from the Santa Ana River, California

Brock M. Huntsman; Matthew J. Young; Kai Palenscar; Kurt E. Anderson; William Ota; Jordan Mae-Jean Buxton; Justin K. Clause; Danielle L. Palm; Jeff Lee Gronemyer; Brett Mills; Kerwin Russell; Rebecca Christensen

doi:10.1093/najfmt/vqaf090

USGS · 70272677

Carbon and nitrogen isotopes of different native fish tissues from the Santa Ana River, California

Brock M. Huntsman·Matthew J. Young·Kai Palenscar·Kurt E. Anderson·William Ota·Jordan Mae-Jean Buxton·Justin K. Clause·Danielle L. Palm·Jeff Lee Gronemyer·Brett Mills·Kerwin Russell·Rebecca Christensen

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Abstract

Objective Stable isotopes are commonly used to understand the role of fishes in aquatic food webs. However, variability in species- and tissue-specific isotopic values can affect the inference that is drawn from a stable isotope study. We evaluated differences in stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) among three tissue types (white muscle, caudal fin rays, and eye lenses) for Santa Ana Sucker Pantosteus santaanae and Arroyo Chub Gila orcuttii to inform the design of a stable isotope study in the Santa Ana River, an urban river that is located in southern California. Methods We used multivariate analyses to test for differences in the stable isotopes of carbon (δ 13 C) and nitrogen (δ 15 N) among the three tissue types that were collected from Santa Ana Sucker and Arroyo Chub. We also summarized the variability in isotopic values that was recorded over time in fish eye lenses and interpreted this variability in reference to the spatial patterns in isotopic values that have been previously reported throughout the Santa Ana River. Results We found that fin ray tissue and white muscle tissue were not significantly different for either isotope or fish species. Fish eye lenses were significantly higher in δ 13 C than muscle tissue, and eye lenses were significantly higher in δ 15 N than fin ray tissue for both fishes. We also found a greater range in δ 13 C and δ 15 N across eye lens layers for Santa Ana Sucker (δ 13 C = 2.01 ± 0.96‰, δ 15 N = 4.93 ± 4.18‰) than for Arroyo Chub (δ 13 C = 0.96 ± 0.65‰, δ 15 N = 4.63 ± 1.45‰). Conclusion Our results indicate that fin rays may be a viable nonlethal alternative to white muscle tissue for use in a stable isotope study of native fish of the Santa Ana River. Additionally, eye lenses could provide a chemical history of fishes within the river, but species-specific correction factors may be needed if stable isotope values for eye lenses are to be compared with more conventional tissue types (e.g., white muscle).

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Source-reported bounding extent: 33.47606375420109° to 34.36492719161251° latitude; -117.95764367109018° to -116.47082959600257° longitude. This indicates report coverage, not an exact sampling location. View area on OpenStreetMap.

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Brock M. Huntsman, Matthew J. Young, Kai Palenscar, Kurt E. Anderson, William Ota, Jordan Mae-Jean Buxton, Justin K. Clause, Danielle L. Palm, Jeff Lee Gronemyer, Brett Mills, Kerwin Russell, Rebecca Christensen. 2025-11-17. Carbon and nitrogen isotopes of different native fish tissues from the Santa Ana River, California. https://doi.org/10.1093/najfmt%2Fvqaf090

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