Graduation Date
Spring 2026
Document Type
Thesis
Program
Master of Science degree with a major in Natural Resources, option Fisheries
Committee Chair Name
Dr. Rafael Cuevas Uribe
Committee Chair Affiliation
Cal Poly Humboldt Faculty or Staff
Second Committee Member Name
Dr. Andre Buchheister
Second Committee Member Affiliation
Cal Poly Humboldt Faculty or Staff
Third Committee Member Name
Dr. Cynthia Le Doux-Bloom
Third Committee Member Affiliation
Cal Poly Humboldt Faculty or Staff
Keywords
Sacramento Pikeminow, Trojan Y, Sex reversal
Subject Categories
Fisheries
Abstract
The Sacramento Pikeminnow (Ptychocheilus grandis), an invasive predator in California’s Eel River, contributes to predation pressure on native salmonid populations despite ongoing suppression programs. This study assessed the feasibility of hormonal sex reversal as an initial step toward implementing the Trojan Y Chromosome (TYC) strategy as a novel tool for managing invasive Sacramento Pikeminnow populations in the Eel River, CA. Objectives were to 1) determine the size when gonadal differentiation occurs 2) identify an effective estradiol dosage for producing phenotypic XY females, and 3) identify sex-reversed fish using a sex-specific genetic marker. Histological examination of juvenile fish was used to estimate the size at which gonadal differentiation becomes detectable. In preliminary samples, gonadal sex could be identified in fish ≥14 cm fork length, whereas differentiated gonads were observed in individuals as small as 6.5 cm in the hormone feeding trial. Juvenile fish were exposed to estradiol at 50 mg/kg and 100 mg/kg between 46 to 56 days, and gonadal sex was determined histologically. Among individuals that could be confidently sexed, control fish exhibited an approximately 1:1 sex ratio, while estradiol treated groups showed female biased sex ratios (71.7% at 50 mg/kg; 82.1% at 100 mg/kg). Genetic analysis indicated that most phenotypic females in estradiol treated groups carried the male associated genotype (XY), consistent with sex reversal. Some samples could not be classified due to histological processing limitations, however, classification success was similar between estradiol treatments. These results indicate that dietary estradiol can shift gonadal differentiation in Sacramento Pikeminnow. Although 100% feminization was not achieved, the observed response supports further investigation of hormonal sex reversal as a step toward implementing a TYC strategy for invasive population control.
Citation Style
AFS
Recommended Citation
McAdams, Raven, "Foundations for Trojan-Y chromosome development in Sacramento Pikeminnow (Ptychocheilus grandis): A novel strategy for invasive species management in the Eel River, CA" (2026). Cal Poly Humboldt theses and projects. 2555.
https://digitalcommons.humboldt.edu/etd/2555