"The Influence of Maternal Size/Age Effects On the Physiological Responses of Adult Female Gopher Rockfish (Sebastes carnatus) to Ocean Acidification and Hypoxia"
A Thesis Defense by Dylan Sarish
Live-Stream | May 1st, 2025 at 4:00 pm PDT
Abstract
Climate change is rapidly reshaping the chemistry of the ocean. Fishes living in California coastal waters experience ocean acidification, elevated pCO2, and hypoxia (OAH) in response to upwelling of deep water, and this process may increase in frequency and intensity with climate change. Nearshore rockfish may be particularly threatened by increasingly frequent OAH conditions due to their long lifespans and late maturation. Maternal effects, whereby larval condition is influenced by non-genetic components of the maternal phenotype (e.g. size, age) or environment, is one process that may allow rockfish to rapidly adapt to climate change. To understand the physiological effects of OAH on pregnant rockfish during gestation, adult female gopher rockfish, Sebastes carnatus, were collected and exposed to four different combined OAH stress treatments, from fertilization to parturition. A second group was exposed to two combined OAH stress treatments. Routine metabolic rate (RMR), maximum metabolic rate (MMR), blood chemistry, including hematocrit (Hct), hemoglobin (tHb), pCO2, HCO3-, ions (Na+, K+, Cl-), and metabolites, were measured to assess physiological responses to OAH stress. Ovarian oxygen levels were measured to examine the potential capacity of females to buffer their developing broods against changing ocean chemistry. Fish exposed to higher OAH stress displayed elevated Hct and tHb, higher blood pCO2 and HCO3-, and decreased MMR, indicating they attempted to compensate for low pH and hypoxia exposure. Only partial compensation was achieved as blood pH was not always maintained near ambient levels. Fish showed signs of buffering their ovaries against hypoxia under OAH exposure. Lastly, pregnancy altered Hct and MMR under OAH exposure and size/age did not have a consistent effect on maternal physiology. By evaluating the responses of maternal physiology to OAH stress, which directly impact larval physiology, we can better understand how climate change affects, fecundity, larval condition, and survival which will influence the management of nearshore fisheries in an ever-changing climate.
Bio
Dylan earned her B.S. in Marine Biology with a minor in Environmental Science from UC San Diego in 2019. While at UCSD, when not practicing as a member of the varsity fencing team, she volunteered for Dr. Andrew Nosal, where she helped with the tagging of sevengill sharks in La Jolla cove, and was in charge of the care and feeding of a tank of juvenile horn sharks in the Scripps Institute of Oceanography’s experimental aquarium. She was also a member of the Coral Ecology Lab under Dr. Stuart Sandin, where she contributed to the 100 Island Challenge. After graduating, Dylan spent some time working for the California Department of Fish and Wildlife, where she contributed to the California Recreational Fisheries Survey (CRFS) as a sampler, assisting with the mission to collect fishery-dependent data on California’s marine recreational fisheries and to accurately estimate catch, effort, and stock.
Dylan joined the Ichthyology lab in Fall of 2022, and examined the effects of ocean acidification and hypoxia on the reproductive success of female gopher rockfish. In her spare time, Dylan enjoys being around animals, baking, and traveling