The Effects Of Hormones On Development Of Embryonic And Post Embryonic Salmonids And Hormone Metabolism During These Stages

Author : Annelise Mary Del Rio
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.6/5 (912 download)

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Download or read book The Effects of Warming and Hypoxia as Individual and Combined Stressors on the Survival, Physiology, and Development of Early Life Stage Chinook Salmon written by Annelise Mary Del Rio and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Chinook salmon (Oncorhynchus tshawytscha) populations in the Central Valley of California are the most vulnerable to climate variability within the species (Crozier et al., 2019). Major threats include climate change, habitat loss, and water management infrastructure. Early life stages of salmon are particularly susceptible to stressors related to these threats because they have little to no ability to swim away from sub-optimal conditions within the incubation environment. Instead, they must rely on internal physiological responses to cope with stressors. Developing salmon thrive in cool, well-oxygenated water; however, warming and hypoxia (low dissolved oxygen) are two stressors that are prevalent within the gravel redds. Few studies have examined the effects of multiple, co-occurring stressors on salmon embryos, but warming and hypoxia are likely to interact because of opposing effects on metabolic rate and physiological performance. The interaction between warming and hypoxia may have contributed to recent high embryo mortality in an endangered population of Sacramento River salmon, where low flows and resulting hypoxia are hypothesized to have reduced the thermal tolerance of salmon embryos (Martin et al. 2017). In this dissertation I examined the effects of warming and hypoxia on the survival and physiology of early life stage Chinook salmon in laboratory and field studies. Rearing embryos under chronic hypoxia resulted in higher mortality, especially in combination with warming, and affected upper thermal tolerance and hypoxia tolerance (Chapter 2). In Chapter 3, I investigated how the timing of exposure to warming, hypoxia, or both stressors affected early life stages during the exposure and found that exposure to both stressors had the greatest effect on hatching, growth, and metabolic rate if embryos were chronically exposed to these stressors during their entire embryogenesis or if they were only exposed late in embryogenesis, shortly before hatch. Furthermore, salmon developmental rate, metabolic rate, and acute stress tolerance continued to be affected in the alevin and fry even though they were transferred to control conditions following hatch, suggesting there are lasting effects of early stress exposure on the physiological performance of juvenile salmon. In Chapter 4, I conducted a field experiment to study how natural water quality variables, with a focus on dissolved oxygen and temperature, affected salmon embryo hatching and survival within artificial redds on the American River near Sacramento, California. Overall, hatching success was low, in part because of poor egg quality. Intergravel dissolved oxygen was highly variable and contributed to differences in embryo survival among the redds, along with intergravel temperature and water flow above the redds. Overall, these studies indicate that the interactions between temperature and dissolved oxygen affect key aspects of early salmon development and physiology in different ways than the individual stressors. My dissertation should help to inform management strategies to improve early life stage salmon survival in Central Valley rivers such as dam management plans for river flows that consider dissolved oxygen and water temperature for salmon.