抗焦慮藥物導致水質污染，影響鮭魚洄游（2/2）

 Recently Yahoo News on-line reported the following:

Salmon migration affected by drug pollution in water from antianxiety medication (2/2)

By Mindy Weisberger, CNN

Updated 12:08 PM EDT, Wed April 16, 2025

CNN

(continue)

Just keep swimming

For the new study, the scientists performed trials with more than 700 young salmon, or “smolts,” in the laboratory and in the field. The research team used sound-transmitting tags to remotely track hundreds of smolts in 2020 and 2021 as the fish navigated the Dal River in central Sweden.

Migrating smolts swim downriver into a reservoir, hurtle over rapids and crest two dams before finally reaching the Baltic Sea. The journey takes 10 to 13 days.

Two major classes of pharmaceuticals — benzodiazepines and opioids — “are commonly detected in rivers and streams worldwide, including in Sweden, where our study was conducted,” Michelangeli said.

Time-release implants in the smolts dispensed two drugs from these classes: clobazam and tramadol. Fish received clobazam, or tramadol, or both. A control group of smolts received implants with no drugs in them at all.

“These two drugs are known to interact chemically when taken together in humans, and they often co-occur in the environment,” Michelangeli said. “This made them a good test case to explore how pharmaceutical mixtures might affect animal behaviour.”

Along with the field trials, the scientists ran a laboratory-based study on 256 smolts to confirm that the implants worked as intended and that the drugs were lingering in the fishes’ bodily tissues and brains.

When the researchers tracked the migrating salmon with transmitters, they found that more clobazam-exposed salmon reached the Baltic than any of the other fish. Compared with the control group, more than twice as many salmon with clobazam implants made it to the sea.

Lab experiments showed that clobazam affected shoaling behavior, in which smolts stick close together to evade predators. Under the influence of clobazam, fish swam farther apart even when a predator was near, “suggesting that the drug may reduce natural fear responses,” Michelangeli said.

An in-lab demonstration shows that juvenile Atlantic salmon under the influence of clobazam were less likely to stick together, in what’s known as shoaling behavior, to evade predators. Marcus Michelangeli

Less fear, more risk

Fish with clobazam implants were also faster at getting past two hydropower dams along their migration route — about two to eight times faster than fish in the other groups. These dams are notorious death zones, where churning turbines can swiftly reduce smolts to salmon tartare.

By diminishing fear in smolts, clobazam might briefly benefit the fish by boosting their migration success. But the drug could also increase their vulnerability to ocean predators, decreasing their chances of surviving long enough to return home to spawn, Caudill said.

“The transition from freshwater to saltwater is one of the most dangerous times in the life of a salmon because they experience many new predators in the ocean,” he said. Drug-exposed and risk-taking salmon may be more likely to reach the Baltic, but less likely to ever leave it alive.

Caudill’s research investigates how environmental change affects fish ecology and evolution. In future work, he said, “I do plan to consider the potential for behavioral effects from pharmaceutical pollution.”

Further study will clarify how behavioral changes from drug pollution affect long-term survival, reproduction and how populations change over time — in salmon and in other wildlife that are vulnerable to pharmaceutical contaminants.

“While more drug-exposed salmon may reach the sea, it doesn’t mean they’re healthy or that the population benefits in the long term,” Michelangeli said.

“The bottom line is we need to be cautious with this interpretation. Changing behaviour with pharmaceuticals — even unintentionally — could reshape whole populations in ways we don’t yet understand.”

Translation

抗焦慮藥物導致水質污染，影響鮭魚洄游（2/2）

CNN

（繼續）

不停繼續游

在這項新研究中，科學家在實驗室和在實地對 700 多條幼鮭魚（或稱為「鮭魚苗」）進行了試驗。 2020 年和 2021 年，當數百條鮭魚遊過瑞典中部的達爾河時，研究小組使用聲音傳輸識別標籤對進行了遠程追蹤。

遷徙的鮭魚順流遊入水庫，衝過急流，越過兩座水壩，最後到達波羅的海。旅程需要10至13天。

Michelangeli 說，苯二氮䓬類藥物和鴉片類藥物這兩大藥物「在世界各地的河流和溪流中都很常見，包括我們進行研究的瑞典」。

植入鮭魚體內的緩釋物釋放了這兩類別中的兩種藥：氯巴占和曲馬多 (tramadol)。魚類接收了氯巴占或曲馬多, 或同時接收兩者。對照組的鮭魚不植入任何藥物。

Michelangeli說： “眾所周知，這兩種藥物一起在人體時會相互發生化學作用，而且藥物經常在環境中同時出現”; “這使它們成為探索藥物的混合物如何影響動物行為的良好測試案例。”

除了實地試驗外，科學家還對 256 條幼鮭進行了實驗室研究，以確認植入物是否發揮了預期作用，以及藥物是否在魚類的身體組織和大腦中殘留。

當研究人員利用發射器追蹤遷徙的鮭魚時，他們發現接觸過較多氯巴占的鮭魚到達波羅的數目比其他魚類都多。與對照組相比，有植入了氯巴占的並成功進入大海的鮭魚數量多了一倍。

實驗室實驗表明，氯巴占會影響群體游遊行為，即鮭魚緊緊聚集在一起以躲避掠食者。在氯巴占的影響下，即使掠食者就在附近，魚也會分開地游，Michelangeli 說: 「這表明這種藥物可能會減少自然的恐懼反應」。

 Michelangeli 說, 實驗室演示表明，受到氯巴占影響的幼年大西洋鮭魚不太可能聚在一起，即所謂的群聚行為，以躲避掠食者。

 

恐懼越少，風險越大

植入了氯巴占的魚在遷徙路線上通過兩座水力發電大壩時也表現得更快 - 比其他組的魚快了大約二到八倍。這些水壩是臭名昭著的死亡區，攪動中渦輪機的可以迅速將幼少鮭魚打成鮭魚碎肉。

透過減少鮭魚的恐懼感，氯巴占可能在短時間內為魚類帶來好處，提高它們的遷徙成功率。但Caudill 表示，這種藥物也可能使它們更容易受到海洋掠食者的攻擊，從而降低它們可存活足夠長時間以返回產卵的機會。

他說：「從淡水到鹹水的轉變是鮭魚一生中的最危險時期之一，因為它們在海洋中會遇到許多新的掠食者。」接觸過藥物且敢於冒險的鮭魚可能更有可能到達波羅的海，但可活著離開的可能性卻較小。

Caudill 的研究, 調查了環境變化如何影響魚類生態和演化。他說，在未來的工作中， “我確實計劃思考藥物污染對行為的潛在影響。”

進一步的研究將闡明, 藥物污染導致的行為變化如何去影響鮭魚和其他易受藥物污染影響的野生動物的長期生存、繁殖, 以及其族群隨著時間的變化。

Michelangeli 說： “雖然更多接觸過藥物的鮭魚可能會進入海洋，但這並不意味著它們是健康的，也不意味著魚群從長遠來看是會受益。”

「歸根結底，我們需要謹慎對待這種解讀。藥物改變行為 - 即使是無意的 - 也可能以我們尚未了解的方式, 改變整個群體」。

              So, researchers discover that when a drug called clobazam accumulates in salmon’s brains, the fish’s normal animal migrating behavior will change. However, this deviation from normal behavior due to human activity in drug pollution is a red flag. The full extent of how pollution may alter salmon health, behavior and reproduction is still unknown to us. Apparently, we need more research to investigate how environmental changes caused by pharmaceutical pollution may affect fish ecology and evolution.