養殖場でのザトウクジラの絡まりは稀 – その原因は甘さかもしれない(Entanglements of humpback whales in fish farms rare – and naivety could be to blame)

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2024-03-21 カナダ・ブリティッシュコロンビア大学(UBC)

ブリティッシュ・コロンビア州の養殖施設でのザトウクジラの絡みつきに関する初の研究では、13年間に8件が報告され、若いクジラの好奇心が一因と考えられている。これはBC水域に年間約7000頭が戻る中、稀な出来事である。大部分のクジラは、捕食者と養殖網の間で絡まる。これに対し、経験豊富な対応者が網を下げ、クジラが逃れることができた。絡まりの要因には施設の設計、解剖学、年齢が含まれ、すべてのクジラは若かった。漁業などの産業は、絡まりの94%を占める他の要因を最小限に抑えるために努力する必要があると述べられた。

<関連情報>

2008年から2021年までのブリティッシュ・コロンビア州沿岸海域における養殖に関連したザトウクジラのもつれ Aquaculture related humpback whale entanglements in coastal waters of British Columbia from 2008–2021

Rhea L. Storlund,Paul E. Cottrell,Brendan Cottrell,Myron Roth,Taylor Lehnhart,Heindrich Snyman,Andrew W. Trites,Stephen A. Raverty
PLOS One  Published: March 20, 2024
DOI:https://doi.org/10.1371/journal.pone.0297768

養殖場でのザトウクジラの絡まりは稀 – その原因は甘さかもしれない(Entanglements of humpback whales in fish farms rare – and naivety could be to blame)

Abstract

Over the past two decades, increasing numbers of humpback whales have been returning to feed in the inshore waters of British Columbia (BC) where marine aquaculture farms are situated. This has led to growing concerns that the presence of aquaculture farms may pose an entanglement threat to humpback whales. However, it is not known whether aquaculture facilities attract humpback whales, or whether there are factors that increase the likelihood of humpback whale, becoming entangled and dying. We examined eight reports of humpback whales interacting with Atlantic salmon farms in BC from 2008 to 2021 to evaluate the conditions that may have contributed to their entanglements. Of the eight entangled humpbacks, three individuals died and five were successfully disentangled and released. All were young animals (1 calf, 7 subadults). Multiple factors were associated with two or more of the reported incidents. These included facility design, environmental features, seasonality, humpback whale age, and feeding behaviour. We found that humpback whales were most commonly entrapped in the predator nets of the aquaculture facilities (6/8 incidents), and were less often entangled in anchor support lines (2/8). The presence of salmon smolts did not appear to be an attractant for humpback whales given that half of the reported entanglements (4/8) occurred at fallowed salmon farms. Almost all of the entanglements (7/8) occurred in late winter (prior to the seasonal return of humpbacks) and during late fall (after most humpbacks have migrated south). Overall, the number of humpback whales impacted by fish farms was small compared to the numbers that return to BC (> 7,000) and accounted for <6% of all types of reported entanglements in BC. Human intervention was required to release humpback whales at fish farms, which points to the need to have well-established protocols to minimize entanglements and maximize successful releases.

1401漁業及び増養殖
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