Publication Date

Spring 2025

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Moss Landing Marine Laboratories

Advisor

Scott Hamilton; Cheryl Logan; Maxime Grand

Abstract

Climate change is rapidly reshaping the chemistry of the ocean. Fishes living in California coastal waters are experiencing increased ocean acidification and hypoxia (OAH) due to more frequent and intense upwelling. Nearshore rockfish may be particularly threatened by these conditions due to their long generational times. However, it is unknown how OAH may impact maternal physiology and reproduction in these viviparous fish. To understand the physiological effects of OAH during gestation, adult female gopher rockfish, Sebastes carnatus, were exposed to a variety of combined OAH stress treatments during different gestational stages. Routine metabolic rate (RMR), maximum metabolic rate (MMR), blood hematocrit (Hct), hemoglobin (tHb), pCO2, HCO3-, Na+, K+, Cl-, and metabolites, were measured to assess physiological responses to OAH stress. Ovarian oxygen was measured to examine the ability to buffer embryos against low oxygen. Fish exposed to higher OAH stress displayed elevated blood Hct, tHb, pCO2 and HCO3-, and decreased MMR, indicating attempted compensation for low pH and hypoxia (with varying levels of success), at increased physiological costs. Fish showed signs of buffering their ovaries against hypoxia. Lastly, pregnancy altered Hct and RMR under OAH exposure and size/age did not have a consistent effect on maternal physiology. By evaluating responses of maternal physiology to OAH stress, we can better understand how climate change affects fecundity, larval condition, and survival, influencing nearshore fisheries in an ever-changing climate.

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