博士 / 國立臺灣海洋大學 / 環境生物與漁業科學學系 / 93 / Taiwan mauxia shrimp (Acetes intermedius Omori 1975) is a commercially and ecologically important species in the coastal waters of southwestern Taiwan from Jialding to Fangkang. However, the spatio-temporal distribution and the diel vertical migration of this species are still unknown. Hence, the objective of this study is to clarify the above subjects based on the fishery data and the in situ studies.
In summer when the southwest monsoon prevailed, Taiwan mauxia shrimp starts a down-estuary migration in June with the increased river discharge associated with heavy summer rainfall (＞130 mm/day) and fishing season for this species then commences. This species stays in the coastal waters until October. However, the fishing season varies largely year by year, and mainly affected by the changing of monsoon. The distribution of this species does not exceed the dispersion range of the river plume off Tungkang. They mainly swarm in the upper half of the Kaoping Canyon and adjacent areas, the second being the adjoining continental shelf areas of Fangliao Canyon.
Sizes of migrator are mostly larger than 3.90 mm and are not sexual matured individuals. The mean annual catch of A. intermedius in the coastal waters of southwestern Taiwan is 2,700 tons, and the highest is more than 4,000 tons.
Taiwan mauxia shrimp migrates from estuaries to coastal waters and perform a diel vertical migration. It performs a diurnal vertical migration from surface to the bottom in the continent shelf (mainly 40-80 m) and to a middle water depth (50-80 m) in the deep Kaoping Canyon before sunrise. However, A. intermedius in waters of deep Kaoping Canyon can also perform a slow descending migration that coincides with photosythetically active radiation of 4μmol/s/ .
The nocturnal vertical movement of A. intermedius depends on the lunar phase, and can be divided into four patterns. Pattern A: When the moon does not appear during the evening (18:00 to 24:00), A. intermedius ascends directly towards the surface and scatters immediately after sunset. The upward migration of this species does not stop temporarily at 10 m water layer. Pattern B: When the moon rise during the evening (18:00 - 24:00), A. intermedius ascends to the surface at sunset and stays there for a few hours before further descending slowly to the 10 m water layer. The shrimp resumes their descent 10 m depth immediately after the moon has risen. Hence, the duration for remaining at the sea surface depend on the difference between the time the moon rise and sunset. Pattern C: When the moon set during the evening (18:00 - 24:00), A. intermedius moves rapidly to the 10 m water layer and stays there for a few hours before further ascending slowly. The shrimp normally resumes their ascent towards the surface immediately after the moon has set. Pattern D: When the moon appears all the evening (18:00 to 24:00), A. intermedius moves slowly upward to a depth of 10 m and stays there all night.
A. intermedius is a important prey of many marine animals. They are easily found by predators because the character of red pigment spots in their exopods. The feeding activity of this species mainly occurs at night. It is suggested that A. intermedius performs the nocturnal vertical migration for avoiding predators and for safe feeding. The diet of A. intermedius was similar to other Acetes which primarily consume phytoplanktons, and also fed zooplankton and amorphous materials. However, Taiwan mauxia shrimp prefers to feed dianoflagellate instead of diatoms.
| Identifer | oai:union.ndltd.org:TW/093NTOU5451002 |
| Date | January 2005 |
| Creators | Wann-Duen Chiou, 邱萬敦 |
| Contributors | Che-Tsung Chen, Lei-Zong Cheng, 陳哲聰, 鄭利榮 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 154 |
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