Effects of Hypoxia on Embryonic Development, Larval Mortality and Growth in Rockfishes (Sebastes spp.)

Viviparous rockfishes (Sebastes spp.) are exposed to varying oxygen levels during gestation in the dynamic oceanographic environment of the California Current. For species reproducing in spring, upwelling drives productivity by delivering nutrient rich water to nearshore habitat paired with low levels of oxygen. With climate change upwelling may vary in timing, frequency and intensity with the potential for rockfishes to have increased exposure to hypoxic waters both temporally and spatially. To learn more about the effects of hypoxia on rockfish reproduction we exposed female fishes with unfertilized eggs to 2, 4 and 8 mg/l oxygen treatments – levels known to occur in their natural environment. Exposure continued for the duration of gestation and embryonic development was monitored every three days. After parturition larvae were placed in treatment tanks at the same three oxygen levels to evaluate depletion rates of lipid reserves, growth and mortality rates. Mothers in low dissolved oxygen treatments had higher incidence of embryo mortality and deformity. Information about the effects of oxygen on early life history of rockfishes will be valuable in informing future fisheries management.