INVESTIGATION OF GREAT LAKES LAKE WHITEFISH EGG FERTILITY AND HEALTH

<p>Lake whitefish (<em>Coregonus clupeaformis</em>) recruitment in the Great Lakes has declined, and it remains unclear whether early failure at fertilization and during embryo development varies among spawning stocks. I tested whether fertilization differs among locations and which biological covariates best explain any patterns. Over two years, I spawned 67 wild pairs from four sites (Fox River, Whitefish Bay, northern Lake Huron, and Little Traverse Bay) using a standardized split-clutch design comparing untreated eggs with iodophor-disinfected eggs. Embryos were incubated under controlled conditions; I quantified fertilization and eye-up and screened adults, gametes, and eggs for bacterial pathogens. Fertilization differed significantly by site, with Little Traverse Bay consistently lowest. Iodophor applied after fertilization during water hardening left fertilization unchanged, but reduced eye-up, indicating a developmental cost. Regression identified visually scored egg quality at spawn as the dominant predictor, with female condition (Wr) showing a modest positive association and location still influencing outcomes. Pathogens did not explain site differences once egg quality and other traits were considered. Together, the results show that spawning locale (a proxy for population) influenced early outcomes, and that when and how eggs were collected strongly affected success. These findings support site-specific broodstock timing, routine egg-quality scoring, careful optimization of iodophor exposure, and continued disease surveillance in older stocks.</p>

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Biology

Year dc:date.available

2025

Author dc:creator

• Diefenbach, Michael L

Contributors dc:contributor

• Dr. Jill Leonard

• lake whitefish
• Coregonus clupeaformis
• fertilization rate
• egg quality
• eye up
• iodophor disinfection
• condition Wr
• spawning site variation
• Great Lakes
• Biology

Repository record dc:identifier

https://commons.nmu.edu/theses/905

OAI identifier oai:identifier

oai:commons.nmu.edu:theses-1970