碩士 / 國立中興大學 / 生命科學系所 / 104 / The cause of fish mass mortality in Taiwan remains dispute. From July 18 to 25, 2013, suspended sediment (SS) concentration of downstream Keelung River increased from 0.05 g/L to 1.94 g/L. Meanwhile, a massive river mullet (Mugil cephalus) die-off event occurred. The media and government attributed the cause of the die-off event to high SS according to the phenomenon that fish gills were severely clogged with fine sediments. Information of SS effects on fishes is not well documented. There is no study on river mullets. The tolerance of fishes to stimulus varies largely among species, so we decide to use kaolin as sediments to examine the effects of SS on river mullets. The mechanisms of effects were investigated by four measurements: quantities of accumulated sediment on the gills, morphology of lamellae, lesions of lamellae, and inter-lamellar cell mass (ILCM). We performed 14 trials using a total of 84 fishes. SS concentrations in this experiment ranged from 0 to 79.3 g/L with 13 specific concentrations. The results of linear regression revealed that the 120 hour maximum non-mortality concentration of SS was 11.1 g/L. The 24, 72 and 120 hour LC50 were approximately 129, 56 and 49 g/L, respectively. The highest mortality was 83%, recorded at a concentration of 79.3 g/L. The body lengths between dead and live fishes were similar, which implies that the body length does not influence tolerance of SS. We didn’t observe any kind of pathological changes on the lamellae. However, in the highest concentration groups, the inter-lamellar cell mass was reduced which may imply the impaired osmoregulation. Unfortunately, the number of sample is so limited that we can’t investigate it any further. We confirmed that the sediments actually clogged in the gill filaments, but the rate of accumulation was speed up after the death of individual fish. In summary, the river mullet’s tolerance concentration to SS was 5.7 times higher than the observed SS peak concentration where the die-off event occurred, which suggests that the high SS was not the main cause of the river mullet die-off event on July 25, 2013, and the quantity of accumulated sediment on the gills of dead fish is not a proper indicator for determining the cause of fish death.
| Identifer | oai:union.ndltd.org:TW/104NCHU5105004 |
| Date | January 2016 |
| Creators | Chia-Chang Kuo, 郭家暢 |
| Contributors | 林幸助 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 71 |
Page generated in 0.0122 seconds