碩士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 93 / Abstract
Estuary region of Tan-Shui River is one of the most important fish habitat in Taiwan. Due to the inter-influence from tidal current, river-water and metropolis waste-water discharges, biomass distribution in the region fluctuate dynamically. In this study, we attempt to monitor the dynamic process through acoustic surveys. Nine tracklines parallel to the shore were designed for the survey. During 2003 ~ 2004, we totally carried on four acoustic surveys to simultaneously collect echo data using Split-beam Scientific Echosounder and ADCP in the region. Both of the data were then post-processed through synoptic processing, a post-calculation method for ADCP data, to obtain hourly current and biomass distribution of the whole region. The results are summarized as follow:
(1) The distribution of SV values simply processed by traditional method showed that high-value region mainly distributed among those tracklines off the shore and near the estuary. The SV value averaged for the tracklines near estuary were always higer than -45dB without any exception among the surveys.
(2) The hourly distribution of SV values calculated by using synoptic processing method suggested that high biomass distributed in the region off the shore, near the estuary and northeast areas. Region with high biomass were compressed or expanded from time to time. However, non of them the state can last for more than 6 hours. The hourly state of coastal current field indicated that the dynamic in the estuary of Tan-Shui River were mainly affected by tide with dominant current direction of northeast-southwest.
(3) According to the comparison between hourly images of echosounding and ADCP, the biomass distributions were related to the current field. The higher agreement of the directions of the current field, the more evenness of the distribution in biomass. When the tidal current stated transit to flood, it usually had a high value of biomass (5dB higher). The hourly variogram’s range, frequency distribution of current speed and direction also suggested that the spatial distribution patterns of biomass were linked to the coastal current state.
In this study, we have successfully applied ADCP synoptic processing method to echosounder data processing. Based on both of the results from echosounder and ADCP, and on the observation of hourly biomass distribution dynamic, we observed a tight connection between tidal current and biomass distribution in the estuary regions of Tan-Shui River. The synoptic processing of echosounder and ADCP data that used and developed in the study are helpful to explain the tidal current and biomass displacement in the coastal zone.
Key words：synoptic processing, echosounder, ADCP, biomass
| Identifer | oai:union.ndltd.org:TW/093NTOU5451044 |
| Date | January 2005 |
| Creators | Tung-Hsieh Chiang, 江東協 |
| Contributors | Hsueh-Jung Lu, 呂學榮 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 111 |
Page generated in 0.0019 seconds