鯊魚遭過度捕獵 已面臨瀕臨絕種危機 | 環境資訊中心

鯊魚遭過度捕獵 已面臨瀕臨絕種危機

2008年02月21日
摘譯自2008年2月19日ENS美國,麻州,波士頓報導;蔡秦怡編譯;蔡麗伶審校

悠遊在海洋中的雙髻鯊。圖片來源:courtesy USGS美國科學促進協會(AAAS)的年會於18日閉幕,一名鯊魚研究專家在會期間告知院士,數量一度豐沛的鯊魚正逐漸從全球的海洋中消失,部分種類並面臨瀕臨絕種的危機。

目前全球大型鯊魚的生存狀態,由主張《瀕危物種紅皮書》的國際自然保育聯盟進行評估的工作。

評估報告中發現,許多大型鯊魚物種的數量,較前減少了一半以上。此種狀況導因於對魚翅與鯊魚魚肉需求的增加、娛樂性的鯊魚捕獵行動、以及鮪魚與箭魚的捕撈,同時每年有數以百萬計的鯊魚因混獲(bycatch)而遭到捕獵。

任職於世界自然保育聯盟轄下的鯊魚保育特別小組成員,同時身兼斯克雷普斯海洋研究所(Scripps Institution of Oceanography,SIO)博士後研究員的包姆(Julia Baum)對此表示,「在幾乎無法遏止捕獵鯊魚的高度壓力之下,許多鯊魚都面臨了瀕臨絕種的危機。」

包姆補充,「我們特別憂心的是,屬於沿岸常見物種的雙髻鯊,因過度捕獵、同時其魚翅在魚翅貿易市場的高度需求,將列入2008年《瀕危物種紅皮書》名單中,並編列為全球性瀕臨絕種的等級。」

包姆此外並指出,在公海裡捕鯊是不受限制的,她同時也支持近期正式通過的、關於即刻限制捕鯊的聯合國決議。此外,她也支持關於鯊魚鰭的一項禁令,也就是只除去鯊魚鰭,卻將奄奄一息的鯊魚棄置於海中使其等待死亡。

由包姆與其後的麥爾斯(Ransom Myers),在過去5年於達爾豪斯大學(Dalhousie)所進行的研究,顯示大西洋西北部的鯊魚數量已有減少的趨勢。以全部種類觀之,從70年代早期迄今,鯊魚數量降至原本的50%。對很多大型的沿海鯊魚種類來說,其數量減少得更多—如虎鯊、雙髻鯊與黑鯊減少的數量已超過95%。

第一份關於地中海海域的鯊魚與魟魚生存狀態的《瀕危物種紅皮書》評估報告於2007年11月公布,報告顯示,有42%的物種面臨瀕臨絕種的可能。除了混獲之外,過度的捕獵也被視為數量減少的主因。

鯊魚保育特別小組計畫研究員吉伯森(Claudine Gibson),同時為此評估報告的共同作者,其表示,「從魔鬼魟到天使鯊,牠們在地中海海域的數量之少,已經成為一個嚴重的問題了。」

吉伯森補充,「研究分析顯示,對於鯊魚與魟魚來說,地中海是全球最危險的海域。同時,因人類在海床的捕撈活動極為頻繁,底棲動物在地中海域生存的風險也就越高。」

AAAS年會上公布的最新研究建議,鯊魚應沿著調整過的路徑,往設置良好的棲息地遷徙。

美國加州大學戴維斯分校生物遙測技術實驗室主任克里姆立(Peter Klimley),其使用電子標籤來追蹤雙髻鯊在東太平洋熱帶地區的遷徙路徑。實驗結果顯示,在鯊魚遷徙的途中出現數個中繼站,包括從墨西哥到厄瓜多的沿岸群島。

Fishing Pressure Pushing Sharks Towards Extinction
BOSTON, Massachusetts, February 19, 2008 (ENS)

Once plentiful sharks are vanishing from the world's oceans, and some species are even at risk of extinction a shark expert told fellow scientists at the annual conference of the American Association for the Advancement of Science, which concluded on Monday.

The global status of large sharks has been assessed by the IUCN-World Conservation Union, which maintains the Red List of Threatened Species.

The assessment finds that many large shark species have declined by more than half due to increased demand for shark fins and meat, recreational shark fisheries, as well as tuna and swordfish fisheries, where millions of sharks are taken as bycatch each year.

"As a result of high and mostly unrestricted fishing pressure, many sharks are now considered to be at risk of extinction," said Julia Baum, a member of the IUCN's Shark Specialist Group and a postdoctoral fellow at Scripps Institution of Oceanography in San Diego.

"Of particular concern is the scalloped hammerhead shark, an iconic coastal species, which will be listed on the 2008 IUCN Red List as globally 'endangered' due to overfishing and high demand for its valuable fins in the shark fin trade," said Baum.

Baum pointed out that fishing for sharks in international waters is unrestricted, and she supports a recently adopted United Nations resolution calling for immediate shark catch limits. Baum also supports a ban on shark finning - the practice of removing only a shark's fins and dumping the still live but helpless shark into the ocean to die.

Research at Dalhousie University over the past five years, conducted by Baum and the late Ransom Myers, demonstrated the magnitude of shark declines in the northwest Atlantic Ocean.

All species the team looked at had declined by over 50 percent since the early 1970s. For many large coastal shark species, the declines were much greater - tiger, scalloped hammerhead, bull and dusky shark populations have all plummeted by more than 95 percent.

The first complete IUCN Red List assessment of the status of all Mediterranean sharks and rays has revealed that 42 percent of the species are threatened with extinction. Overfishing, including bycatch, was identified as the main cause of decline by the study, which was released in November 2007.

"From devil rays to angel sharks, Mediterranean populations of these vulnerable species are in serious trouble," said Claudine Gibson, Programme Officer for the IUCN Shark Specialist Group and co-author of the report.

"Our analyses reveal the Mediterranean Sea as one of the world's most dangerous places on Earth for sharks and rays," Gibson said. "Bottom dwelling species appear to be at greatest risk in this region, due mainly to intense fishing of the seabed."

New research unveiled at the AAAS conference suggests that sharks migrate along fixed routes between well-established gathering places.

Peter Klimley, director of the Biotelemetry Laboratory at the University of California-Davis, has used electronic tags to track scalloped hammerhead sharks along their migration routes in the tropical Eastern Pacific Ocean. Their results suggest that these sharks speed between a series of "stepping stone" sites, near coastal island groups ranging from Mexico to Ecuador.

全文及圖片詳見:ENS