| Summary: | 碩士 === 國立臺灣海洋大學 === 海洋環境資訊學系 === 100 === The region over the Keelungyu Sill is characterized by ripple mark due to tidal currents and often crowed with fishing vessels in a row along the Sill. Therefore, the relation of the local water quality or fishing catch to the corresponding tides should be explored. For that, the water sampling was conducted in the flood or ebb tides on the days of high or low tide. Meanwhile, the CTD hydrographic surveys were implemented. The fishing status in the region of the Sill was achieved by questionnaires for fisher- men.
The ripple mark over the Sill displays in different jumping upon the southeast ebb current or the northwest flood current, causing the subtrac- tions of the temperature and salinity fields varying in four ways regularly in the flood/ebb for high/low tides. The six water quality parameters of phos- phate, silicate, nitrite, nitrate, ammonia nitrogen and chlorophyll-a have their own distribution trend in space for various tides. Since their subtrac- tions of the four different tides do not reveal the influence of the bottom topography of the Sill, further analyses rely on their summations instead. And the growing or decaying in total indeed relates to various tides. Nev- ertheless, regarding the primary productivity, the chlorophyll-a has no clear relation to the ascending or descending of nutrients.
There is seasonal difference in species for local prevailing fish over the Sill. Fishermen are aware of employing timely fishing method. They also know the current along the Sill so well to catch fish with freely drift. Ac- cording to the cross investigation among the hydrography, water quality and tides, it is found that fish clustering near the Sill is nothing to do with the nutrients or the primary productivity over there. Thus it should be a re- sult of the jumping waters at the Sill that fish come for food by mistake as in the current rip or the artificial reef.
Studies on the physical, chemical, biological and geological oceanog- raphy for the Keelungyu Sill should be complete. Such a fascinating topic could be continued with the perspective of regional tourism developed for marine interests.
Keywords: Keelungyu Sill, water quality, fisheries, tides, variability.
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