碩士 / 國立高雄海洋科技大學 / 海洋環境工程研究所 / 96 / Abstract
This study is aiming to investigate the tolerance of milkfish fry (Chanos chanos)exposed to low levels of dissolved oxygen (D.O.) with varied salinity contents, in an attempt to provide ecological basis for further improvement of river water quality, as well as for the restoration of fish community in the estuaries of Taiwan.
Laboratory tolerance experiments on milkfish exposed to low levels of D.O. were conducted in a secluded growth room. The lethal thresholds at 4‰, 8‰, 16‰, 24‰ and 33‰ salinity level were recorded as 24% ~ 45%(1.88 ~ 3.52 mg/l)19% ~ 45%(1.41 ~ 3.35mg/l)15% ~ 29%(1.06 ~ 2.05mg /l)15% ~ 45%(1.01 ~ 3.03mg/l)and 15% ~ 45%(0.96 ~ 2.88 mg/l)air saturation (sat%) , respectively. Median lethal times(LT50)and 48 hours median lethal concentrations（48h LC50）were further estimated. In general, the LT50 tended to increase with increasing D.O. content. The LT50 at 15 sat% and above were significantly greater than those at 12 sat% and lower levels. Comparisons of the LT50 among fish at varied salinity contents were made, and results showed that the LT50 at 16‰ salinity was the greatest, and followed by 24‰, 33‰, 8‰ and 4‰ salinity. Similar results were also obtained for the comparisons of LC50, fish at 16‰ salinity tended to survive better the anoxic condition (LC50 = 20.1 sat%; 1.42mg /l), and followed by those at 24‰ (LC50 = 23.3 sat%; 1.57mg /l), 33‰ (LC50 = 25.3 sat%; 1.62mg /l), 8‰ (LC50 = 27.5 sat%; 2.08mg /l) and 4‰ (LC50 = 27.9 sat%; 2.18mg /l) salinity. Based on the results of current study, the DO level of river water is suggested to be maintained above 2.87 mg/l (36.6% air saturation, 48h LC10 of milkfish at 4‰ salinity). In case of that DO occasionally fall to the above level, it is strongly recommended that a manual aeration system is strongly recommended to achieve a sustainable environment for the present fish community.
| Identifer | oai:union.ndltd.org:TW/096NKIM8282006 |
| Date | January 2008 |
| Creators | Yu, Li- Cheng, 余立誠 |
| Contributors | Chen, Chiee- Young, 陳志遠 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 102 |
Page generated in 0.0019 seconds