On a hillside overlooking False Bay [South Africa] – shark spotters are keeping a close watch on the waves.

在俯瞰南非福尔斯湾的山坡上，鲨鱼观察者们正在密切关注着海浪。

After all, this coastline near Cape Town has long been home to hundreds if not thousands of the world's most famous predator. Until now.

毕竟，开普敦附近的这片海岸线长期以来都是数百甚至上千头举世闻名的食肉动物的家园。然而，今非昔比。

South Africa's great white sharks – the stuff of nightmares and of nature documentaries – have gone mysteriously missing.

南非大白鲨，这种通常出现在噩梦和自然纪录片中的动物，神秘地失踪了。

Monwabisi Sikweyiya, Shark Spotters

Wherever you go, if you put your feet into the water, you expect to encounter white shark, but that's not the case no more. I don't even remember the last time I saw the shark.

蒙瓦比西·锡克维耶亚    鲨鱼观察者组织（Shark Spotters）

“过去，不管你走到哪里，如果你把脚伸入水中，你可能就会遇到大白鲨，但现在情况不同了。我都不记得最后一次看到鲨鱼是什么时候了。”

It's two years now since they vanished, and the economic impact has been devastating. The great white tourism industry has collapsed.

自大白鲨消失以来，已经两年了，对经济造成了毁灭性打击。该地区靠大白鲨吸引游客带动的旅游业已经崩溃。

But why did they disappear? This amateur footage shows the arrival of two suspects, a pair of orcas – killer whales – could they have scared off all those great whites?

但大白鲨为什么会消失呢？这段由业余人士拍摄的录像记录了两名嫌疑犯的到来，一对虎鲸，别名逆戟鲸，是它们把大白鲨都吓跑了吗？

Sarah Warries, CEO, Shark Spotters

To us, the arrival of these orcas and then the reduction in shark activity does all seem to be correlated. It appears that the orcas arrived and the sharks just are aware that they are no longer the apex predator any more.

莎拉·沃瑞斯     鲨鱼观察者组织首席执行官

“对我们来说，这些虎鲸的到来和鲨鱼活动的减少似乎都是相关的。看来是虎鲸一来，鲨鱼就意识到自己不再是食物链顶端的掠食者了。”

But here is another theory. Local fishermen have been catching smaller sharks to export to fish and chip shops in Australia. Those sharks formed part of the great whites' diet.

但还有另一种理论。当地渔民一直在捕捞较小的鲨鱼，出口到澳大利亚的炸鱼和薯条店。而这些鲨鱼正是大白鲨的食物之一。

But other shark detectives see a more complicated crime scene. Dr Sarah Andreotti used to study great whites here. Now she's using a harpoon to scrape DNA from smaller species.

但其他的鲨鱼侦探认为犯罪现场的真相更复杂。莎拉·安德烈奥蒂博士曾经在这里研究大白鲨。她正在用鱼叉从较小的鲨鱼物种身上刮取DNA。

Her view is that the great white population has been shrinking unnoticed for many years because of climate change, pollution, overfishing – a range of human activities.

她的观点是，大白鲨的数量多年来一直在悄声无息地减少，原因是气候变化、污染和过度捕捞这一系列人类活动。

Dr Sara Andreotti, University of Stellenbosch

It is not just frustrating, it's the feeling that that happened under our watch, you know, we saw the sharks, we saw the numbers were not great, and the work we did wasn't enough to get the environment better protected in a way, or maybe it was just too late.

莎拉·安德烈奥蒂博士     斯坦陵布什大学

“大白鲨的消失不仅令人沮丧，同时也给人一种事情就发生在眼皮底下，却无能为力的感觉，我们看到鲨鱼数量的下降，但所做的工作却不足以让环境得到更好的保护，也许一切为时已晚。”

Her conclusion is that the great whites didn't move elsewhere, they simply died out – their turf taken over by these copper sharks.

她的结论是：大白鲨并没有迁徙到别处，只是在这个地区灭绝了，它们的地盘被这些短尾真鲨占领了。

Nothing in this great white mystery is certain, except for the knowledge that we humans are, as usual, prime suspects.

在大白鲨消失的谜团中，一切都是未知数，但有一点可以确定的是，一如既往，人类是头号嫌疑犯。