博士 / 國立海洋大學 / 漁業科學學系 / 87 / Sergestid shrimp, Sergia lucens, is one of the few planktonic shrimp that can be utilized as food by human society. It is found only in the coastal waters of Taiwan and the Suruga Bay of Japan through the world.
The fishery for sergestid shrimp has been developed for more than ten years in Taiwan. Academic studies concentrated mainly on fishing gear mechanism and ecology of fishing ground. Stock assessment and management are yet to be conducted. This study concerns fishing efficiency, optimal effort and optimal yield based on catch statistics. Ecological studies including sea condition, meteorology and nearby river discharge were conducted between 1990 and 1997. Resource management model based on the about results is also constructed.
Analysis on fishing efficiency of the mid-trawl net showed that the sweeping depth is negatively related to warp length and positively to towing speed, respectively. Under the conditions of towing speed of 0.5-1.5 m/sec , the ratio of warp length to towing depth of head line is between 4.78 and 2.18. This implies that the best warp length of the trawl is 2.40-3.58 time of the water depth in which the sergestid shrimp aggregated, under the condition of 0.7-1.0 m/sec towing speed.
The index of fishing efficiency was found closely related to the tonnage as well as engine power of commercial vessels. The 50 percentage selection length (L50) of inner and outer codends of the mid-trawl net for sergestid shrimp were equal to 3.77 cm and 3.38 cm, respectively.
The productivity index was estimated by the monthly CPUE of each fishing blocks and calculated by the equations of Hirayama. The highest value occurred in the area off Fan-liao, followed by the value at the southwestern area off Liu-chiu Yu, and the southeastern Liu-chiu Yu area, respectively. The total range of productivity index is 0.064-2.003. Productivities of fishing ground covering the coastal waters between Fan-liao and Fan-shan were generally higher than those between Tung-kang and Liu-chiu Yu.
The center of gravity of fishing ground was located in the coastal waters between Fan-liao and Fan-shan from early November 1990 to middle February 1991. The stock dispersed from early March to middle May 1991 and moved to the waters off Tung-kang later on.
Stock size, catchability coefficient (q) and fishing nortality coefficient (F) were analyzed by the Leslie''s method. The total stock size in 1993 was estimated equal to 5,846.9×106, with a catchability coefficient of 0.0001104 and a fishing mortality coefficient of F=0.5682. The rate of exploitation is approximately 0.4045, or 40 %.
The methods of Schaefer and Fox were employed for estimating the MSY level of the fishery. The results showed a MSY level of 865.30 tons, under the fishing effort condition of 7,332 hauls. The optimal effort and optimal yield were also estimated by the F0.1 method of Gulland and Boerema, with results being equal to 5,719 hauls and 839.34 tons, respectively.
| Identifer | oai:union.ndltd.org:TW/087NTOU0451012 |
| Date | January 1999 |
| Creators | Chen Shou-Ren, 陳守仁 |
| Contributors | Chow Yao-Shou, Ho Chuan-Hung, 周耀烋, 何權浤 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 134 |
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