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Estimation of growth parameters and biological reference points for the East Asian fourfinger threadfin (Eleutheronema rhadinum) in waters off western Taiwan
|Authors: ||Cheng, Chun-Ya|
|Contributors: ||NTOU:Department of Environmental Biology and Fisheries Science|
East Asian fourfinger threadfin;length frequency analysis;gear selectivity;yield-per-recruit
|Issue Date: ||2020-07-02T07:40:36Z
|Abstract: ||多鱗四絲馬鮁(Eleutheronema rhadinum)又名午仔魚，屬臺灣沿近海域重要高經濟價值魚種，近年沿近海漁業漁獲量有明顯上升趨勢，然而國內外對多鱗四絲馬鮁的研究成果有限，探討生活史與生物參數等研究缺乏。本研究於2016年至2018年，按月至苗栗龍鳳漁港進行採樣，共量測得5,364筆體長資料進行分析，結果顯示四絲馬鮁主要漁期為每年十月底至隔年二月，十一月蒐集所蒐集體長樣本為多，主要在20至28公分尾叉長；七、八月樣本數較少，僅288尾體長樣本。體長頻度分析結果顯示有明顯季節性推移現象，推估von Bertalanffy成長參數: K=0.469 yr-1，極限體長L∞ = 73.559 cm，零體長時理論年齡t0 = -0.067 yr，50%漁具選擇率體長為21.516 cm。從樣本中可分離出5個年齡群，年齡別平均體長為：L0 = 2.28 、L1 = 28.95、L2 = 45.64、L3 = 56.09、L4 = 62.62 cm，1歲魚為優勢年齡群，估計最大壽命(tmax)為6.4 yr，瞬時全死亡率Z = 1.775 yr-1，瞬時自然死亡率M = 0.703~0.815 yr-1，瞬時漁獲死亡率F = 0.960~1.072 yr-1，開發率E = 0.541~0.604，單位加入生產量在211.53~291.90公克，目前最適初捕年齡為1歲，惟目前漁獲死亡率已大於最大漁獲死亡率(Fmax)，須密切注意此資源的變動。|
East Asian fourfinger threadfin (Eleutheronema rhadinum) is an economically important species, especially in coastal waters off western Taiwan, with an increasing trend showed in the catch in recent years. However, little studies related to life history and biological parameters have been conducted for this species. Port sampling was made randomly every month from 2016 to 2018 to obtain length data; in total 5,364 individuals were measured. Result showed that the major fishing season started from late October until next February. A large sample size of length samples was collected in November in this study, ranging from 20 to 28 cm in fork length, while only few size samples were available during July and August. Obvious seasonal shifts in length frequency distribution were observed. Five age classes were identified in the size samples and the age 1 fish were dominant among age classes. The von Bertalanffy growth parameters for the East Asian fourfinger threadfin were estimated at L∞ = 73.559 cm , K = 0.469 yr-1, and t0 = -0.067 yr. Size at 50% selectivity was estimated at 21.516 cm. Instantaneous rates of total mortality (Z) and natural mortality (M) were derived at 1.775 yr-1 and 0.703-0.815 yr-1, respectively, with that for fishing mortality (F) ranging from 0.960 to 1.072 yr-1 and the exploitation ratios (E) from 0.541 to 0.604. Yield-per-recruit (YPR) were calculated from 211.53 to 291.90 g, suggesting a suitable age at first capture to be 1 yr. The stock needs to be monitored carefully as a result of current fishing mortality higher than Fmax.
|Appears in Collections:||[環境生物與漁業科學學系] 博碩士論文|
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