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Science:结束狩猎或难挽救濒危石首鱼

标签:美国 石首鱼
摘要 : 是什么在杀死美国加利福尼亚湾巨大的石首鱼?有传言称,这种长寿鱼类是被下加利福尼亚州的渔民和偷猎者几乎捕捞殆尽的。近日,美国考古学学会会议上的新数据表明,该鱼类生存环境的改变可能更具毁灭性

是什么在杀死美国加利福尼亚湾巨大的石首鱼?有传言称,这种长寿鱼类是被下加利福尼亚州的渔民和偷猎者几乎捕捞殆尽的。近日,美国考古学学会会议上的新数据表明,该鱼类生存环境的改变可能更具毁灭性。

考古学家分析了Rancho Punta Estrella的石首鱼鱼骨,这是位于下加利福尼亚州的一处遗址,分别在距今1万年前和5000年前是人类的栖息地,他们发现石首鱼内耳中的一种特殊骨头——内耳石有助于重建其早期生存环境。

像树轮一样,石首鱼每过一年内耳石就会长出新的一层。每一层内耳石都会以氧同位素的形式保存鱼类当年生活的水中的化学成分。

古石首鱼内耳石揭示,该物种一度曾在咸水中度过早期生活,这种微咸的水经过一条河流注入海洋。在其于20世纪被堵塞之前,科罗拉多河流入加利福尼亚湾并形成一个大河口;现在,那里的淡水已经变为涓涓细流。

古内耳石表明早期石首鱼在生命的前几年曾生活在河口,它们比现代的同类成熟期早5年,体重可达目前100公斤的两倍。

这些结果表明,即便墨西哥政府停止今天的盈利性石首鱼狩猎(一枚鱼鳔在黑市上可售1.4万美元),该物种在墨西哥湾彻底被改变的环境中仍然难以生存。

原文链接:

Ending poaching may not save the doomed totoaba

原文摘要:

What’s killing the giant totoaba of the Gulf of California? The long-lived fish has been hunted nearly to extinction by fishermen and poachers in Baja California—or so you may have heard. Now, new data presented today at the Society for American Archaeology meeting here confirm that changes to the fish’s environment may have been even more devastating. Archaeologists studying totoaba bones from Rancho Punta Estrella—a site in Baja California occupied by humans 10,000 years ago and then again 5000 years ago—used a special bone from the fish’s inner ear, called an otolith, to help them reconstruct the totoaba’s early environment. Otoliths grow a new layer for each year of the fish’s life, like tree rings. Each layer preserves the chemical composition of the water in which the fish lived during that year, in the form of oxygen isotopes. The newly analyzed ancient totoaba otoliths show the species once spent its early years in brackish water, the lightly salty mix found wher a river empties into the sea. Before it was dammed over the course of the 20th century, the Colorado River emptied into the Gulf of California and formed a large estuary; now, the freshwater has been reduced to just a trickle. Earlier analyses of ancient totoaba ear bones show that juveniles once stayed in the estuary for the first several years of their lives. They also matured up to 5 years earlier than their modern counterparts and grew to twice their current size of 100 kilograms. Those results suggest that even if the Mexican government put a halt to today’s profitable totoaba poaching (a swim bladder can go for $14,000 on the black market), the species would still struggle to survive in the gulf’s radically altered environment.

来源: Science 浏览次数:0

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