Effects of Total Dissolved Gas on Chum Salmon Fry Survival, Growth, Gas Bubble Disease, and Seawater Tolerance

• Published in: North American journal of fisheries management Vol. 33; no. 1; pp. 200 - 215
• Main Authors: Geist, David R, Linley, Timothy J, Cullinan, Valerie, Deng, Zhiqun
• Format: Journal Article
• Language: English
• Published: Taylor & Francis Group 01.02.2013
• Subjects: alevins; bubbles; confidence interval; gas bubble disease; gastrointestinal system; gravel; guidelines; habitats; mortality; nose; Oncorhynchus keta; salmon; seawater; smolts; water quality; Columbia River
• ISSN: 1548-8675; 1548-8675
• DOI: 10.1080/02755947.2012.750634

Chum Salmon Oncorhynchus keta alevins developing in gravel downstream of Bonneville Dam on the Columbia River are exposed to elevated total dissolved gas (TDG) when water is spilled to move migrating salmon smolts to the ocean. We studied whether alevins that were exposed to six levels of dissolved gas ranging from 100% to 130% TDG at three development periods between hatch and emergence (hereafter, early, middle, and late stages) experienced differential mortality, growth, gas bubble disease, or seawater tolerance. Each life stage was exposed for 49 d (early stage), 28 d (middle stage), or 15 d (late stage) beginning at 13, 34, and 47 d posthatch, respectively, through emergence. Mortality for all stages was estimated to be 8% (95% confidence interval [CI] = 4–12%) when dissolved gas levels were less than 117% TDG. Mortality increased as dissolved gas levels rose above 117% TDG; the lethal concentration producing 50% mortality was 128.7% TDG (95% CI = 127.2–130.3% TDG) in the early and middle stages. There was no evidence that gas exposure affected growth. The proportion of fish with gas bubble disease increased with increasing gas concentrations, and bubbles occurred most commonly in the nares and gastrointestinal tract. Early stage fish exhibited higher ratios of filamental to lamellar gill chloride cells than late-stage fish, and these ratios increased and decreased for early and late-stage fish, respectively, as gas levels increased; however, there were no significant differences in mortality between life stages after 96 h in seawater. The study results suggest that water quality guidelines for dissolved gas (≤105% TDG) offer a conservative level of protection to Chum Salmon alevins incubating in gravel habitat downstream of Bonneville Dam.