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Stock assessment of dolphinfish (Coryphaena hippurus) in the eastern waters off Taiwan using age-structured production model
|Authors: ||Lin, Yu-Yong|
|Contributors: ||NTOU:Department of Environmental Biology and Fisheries Science|
Dolphinfish;Coryphaena hippurus;Eastern waters off Taiwan;Catch per unit effort (CPUE);Stock assessment;Age-structured production model
|Issue Date: ||2020-07-02T07:40:31Z
|Abstract: ||鬼頭刀(Coryphaena hippurus)為臺灣沿近海漁業資源中重要的經濟性魚種之一，其中以臺灣東部海域為鬼頭刀漁獲為大宗，是臺灣東部海域重要之目標魚種。本研究使用歷年宜蘭縣、花蓮縣及台東縣之鬼頭刀總漁獲量、鬼頭刀體長與每日拍賣資料，以年齡結構生產量模式(age-structured production model, ASPM)對臺灣東部海域鬼頭刀資源量變動進行分析。資源量相對指標是根據每日拍賣資料計算之單位努力漁獲量(catch per unit effort, CPUE)配合泛線性模式(general linear model, GLM)進行標準化後帶入模式進行評估。標準化CPUE趨勢顯示於1990至1999年之間跌幅較大，而2000至2006年間呈現逐年增加，但近年來仍呈現減少的趨勢。根據ASPM基礎模式分析結果顯示，臺灣東部海域之漁獲年齡結構以1歲魚為主，歷年產卵群生物量隨著漁獲死亡率增加而逐年下降，但目前漁獲死亡率仍在最大持續生產量(maximum sustainable yield, MSY)水準以下且產卵群生物量略高於MSY水準。在敏感度分析方面，模式結果會受到自然死亡率與曲度的假設而有所影響，在大多數假設條下模式估計之漁獲死亡率仍維持在MSY水準之下，但產卵群生物量為接近或略高MSY水準。綜合本研究結果表示，臺灣東部海域的鬼頭刀資源目前屬於適度開發機率較高，但產卵群生物量卻可能具有無法維持在MSY水準的風險。為維持該資源之永續利用，需持續加以評估與關切鬼頭刀的資源動態與漁業利用。|
The dolphinfish (Coryphaena hippurus) is one of the most important economic species for Taiwanese offshore and coastal fishery and most catches were caught in the eastern waters of Taiwan. Therefore, dolphinfish is an important target species for fishery in the eastern waters of Taiwan. The data used in the study were historical total catches, length-frequency and daily auction data of dolphinfish from Yilan, Haulien, and Taitung. In this study, the population status of dolphinfish in the eastern off Taiwan was evaluated using age-structured production model (ASPM). The relative abundance index was based on the catch per unit effort (CPUE) standardized using general linear model (GLM) based on daily auction data. The base-case results of ASPM indicated that the catches were mainly consisted of fishes with 1-year-old. The spawning stock biomass decreased gradually with increase of catch, but the current fishing mortality was still below the maximum sustainable yield (MSY) level and the spawning stock biomass was slightly higher than the MSY level. The result of the sensitivity analysis indicated that the results of assessment model are sensitive to the values of natural mortality and steepness. The current fishing mortality was below the MSY level in most of cases, but the spawning stock biomass was close to or slightly higher than the MSY level. Based on the results of this study, there is a higher probability that the dolphinfish in the eastern waters of Taiwan was moderately exploited currently, but there is also a risk that the spawning stock biomass may not maintain at the MSY levels. Therefore, in order to maintain the sustainability of this stock, it is necessary to continuously evaluate and monitor the stock dynamics of the resource and exploitation for the fishery.
|Appears in Collections:||[環境生物與漁業科學學系] 博碩士論文|
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