Here’s one for you: when is a critically endangered, maneating, freshwater shark a common, fish‐eating, marine creature that never bit anyone? Answer: when it’s a Ganges shark (Glyphis gangeticus) (Figure 1). But don’t let that name fool you. While it might turn up anywhere from Pakistan to Borneo, the last place to look for it is in the Ganges. If you like your elasmobranchs enigmatic, you’ve come to the right place!

In Volume 1 of his vast work, The Fishes of India (1878; London, UK: William Dawson and Sons Ltd), pioneering 19th‐century ichthyologist Francis Day wrote, “This is one of the most ferocious of Indian sharks, and frequently attacks bathers even in the Hooghly at Calcutta, where it is so dreaded that a reward is offered for each that is captured”. Certainly, shark attacks in the Bay of Bengal – into which the Ganges flows via its many distributaries, including the Hooghly River – were once not uncommon. Until some 200 years ago, people would gather on Sagar Island where the tidal Hooghly meets the salty Indian Ocean, for grim festivals in January and November. There, around the full moon, elderly men and women would walk into the murky water with the purpose of being devoured. And devoured they often were. Some families would even cast their fifth‐born child to the sharks as a sacrifice to the Ganges. Harrowing accounts of the practice (see Travels of Fray Sebastien Manrique 1629–1643, Vol 1, 2016; Abingdon, UK: Routeledge, or Papers etc: Third Part, Vol IX, 1812–1813; London, UK: East India Company), which was frowned upon by the greater population and sanctioned by no religious code, eventually led to its prohibition – at least the part concerning children. But were the executioners Ganges sharks? While these fish can reach well over 2.5 m in length, many authors highlight that their slender teeth are far more suited to grabbing fish than humans. A much more likely culprit is the similar‐looking bull shark (Carcharhinus leucas), which has all the right equipment.

Day also wrote of the Ganges shark “ascending rivers to above tidal influence”, an assertion last backed up in 2001 by some jaws collected 84 km upstream from the mouth of the Hooghly. And certainly, you don’t have to work hard to gather a bunch of modern references that describe this fish as a true freshwater/estuarine shark, with some claiming there to be no marine records for the species at all. One author even cites it having overcome rapids to inhabit the upper reaches of the Agusan River in the Philippines, 150 miles from the sea. But wouldn’t the ability to enter the ocean proper help explain how the Ganges shark got to the Philippines? Or to Sri Lanka, where one might also have turned up? And wouldn’t a seafaring capability also help explain the genetic evidence identifying a shark that inhabits the lower reaches of the Kinabatangan River in Borneo as G gangeticus?

Swimming hard against the freshwater‐lifestyle current, one well‐known ichthyologist cites the creature as an entirely brackish water/marine animal. In 2006, Tyson Roberts reported how, after years of fieldwork, he was unable to find any record of the Ganges shark in the Ganges itself, or in any body of freshwater he examined from India to Myanmar, “debunking the mythology of the Gangetic freshwater shark” (Nat Hist Bull Siam Soc 2006; 54: 261–78). Neither did he find any freshwater fisherman, fisheries biologist, or riverbank fishmonger who had seen one. He even went on to show that the first description of the fish by Augustin Lamare‐Picquot as a beast of the Ganges was probably due to a confusion of field notes and errors in translation. In contrast, Roberts found plenty of Ganges sharks hauled in by sea fishermen; he even cited them as the species of large shark most commonly captured by the villagers of Sittwe in Myanmar. It is “a common groundshark in the Bay of Bengal”, he declared, “rather than any endangered freshwater shark of the Ganges”.

And yet the Ganges shark is still generally regarded as extremely rare, with its numbers in decline. The IUCN records it as critically endangered, and when one turns up at a fish market it’s enough to get ichthyologists dashing for their cameras. Not something you’d expect if you had first read Roberts’ paper, which emphatically states that “there is no evidence of [a] historical decline in the range of the species or in its population numbers. It is not critically endangered or even threatened”. Of course, the fortunes of the Ganges shark may have changed since Roberts’ paper put the cat among the Hooghly pigeons, but even in 2006 it was generally considered to be very scarce.

So there you have it. The Ganges shark: a rare, deadly, freshwater fish found only in marine/brackish habitats, commonly in the Bay of Bengal, that never hurt a fly, and with a “Hooghly” inappropriate common name. Got that everyone? Good! I’m glad we got that cleared up.

这是给你的：什么时候濒临灭绝，操纵有力的淡水鲨鱼是一种常见的，食鱼的海洋生物，从来没有咬过任何人？答案：当它是恒河鲨（Glyphis gangeticus）时（图1）。但是，不要让这个名字愚弄你。从巴基斯坦到婆罗洲，它可能会出现在任何地方，但最后找的地方是恒河。如果您喜欢神秘的弹性分支，那就来对地方了！

在他的巨著《印度的鱼》第1卷中（1878年；英国伦敦：威廉·道森父子有限公司），开创性的19世纪鱼类学家弗朗西斯·戴（Francis Day）写道：“这是印度鲨鱼中最凶猛的鲨鱼之一，即使在加尔各答的胡格里（Hooghly），也经常袭击沐浴者，因此害怕为每一个被捕获的人提供奖励。” 当然，孟加拉湾的鲨鱼袭击曾经屡见不鲜。恒河通过其许多支流（包括霍格利河）流入孟加拉湾。直到大约200年前，人们会聚集在潮汐的Hooghly与咸印度洋相遇的萨加尔岛（Sagar Island），在1月和11月举行严酷的节日。在那里，满月前后，年长的男人和女人会走进昏暗的水中，以被吞噬。经常被他们吞噬。一些家庭甚至把他们的第五胎孩子丢给鲨鱼，作为对恒河的牺牲。令人痛心的做法说明（请参阅Fray Sebastien Manrique的旅行1621-1643，第一卷，2016年；英国，阿宾登：Routeledge或论文等：第三部分，第IX卷，1812年至1813年；英国伦敦：东印度公司（East India Company）受到广大人口的反对，并没有受到任何宗教法规的制裁，最终导致了禁令的产生-至少涉及到儿童方面。但是the子手是恒河鲨鱼吗？虽然这些鱼的长度可以达到2.5 m以上，但许多作者强调说，它们的细长牙齿比人类更适合抓鱼。看起来类似的斗牛鲨（Carcharhinus leucas）是最可能的罪魁祸首，该鲨鱼拥有所有合适的设备。

戴还撰写了恒河鲨鱼“将河流提升到潮汐影响之上”的说法，该主张最后一次被2001年由胡格里河上游84公里处收集的下颚所支持。当然，您不必费劲收集大量现代参考文献，将这条鱼描述为真正的淡水/河口鲨鱼，有些人则声称根本没有该物种的海洋记录。一位作者甚至引用它克服了急流，栖息在距大海150英里的菲律宾阿古桑河上游。但是，进入海洋的能力不能正确地解释恒河鲨鱼如何到达菲律宾吗？或去斯里兰卡，还有可能出现在哪里？而且，航海能力也不能帮助解释遗传证据，从而确定一条鲨鱼栖息在婆罗洲的京那巴当岸河下游。G gangeticus？

一位著名的鱼类学家在逆着淡水生活方式的潮流努力游动时，将这种生物称为完全咸淡的水/海洋动物。2006年，泰森·罗伯茨（Tyson Roberts）报告说，经过多年的田野调查，他如何无法在恒河本身或从印度到缅甸考察的淡水中找到任何关于恒河鲨鱼的记录，“揭穿了恒河淡水的神话鲨鱼”（Nat Hist Bull Siam Soc 2006；54：261–78）。他也没有找到曾见过的任何淡水渔民，渔业生物学家或河岸渔民。他甚至继续表明，奥古斯丁·拉马雷-皮克多（Augustin Lamare-Picquot）对这条鱼的首次描述是恒河的野兽，这可能是由于田野记录的混乱和翻译错误所致。相比之下，罗伯茨（Roberts）发现海钓者拖着大量恒河鲨鱼。他甚至将它们列为缅甸实兑村民最常捕获的大鲨鱼种类。他宣称，这是“孟加拉湾的常见鲨鱼，而不是恒河中任何濒临灭绝的淡水鲨鱼”。

然而，恒河鲨仍被普遍认为是极为罕见的，其数量在下降。IUCN将其记录为极度濒临灭绝，当有人在鱼市场上露面时，这足以使鱼眼学家为他们的相机而奔波。如果您初读罗伯茨的论文，那不是您所期望的，该论文着重指出：“没有证据表明该物种的范围或种群数量出现历史性下降。它没有受到严重威胁，甚至没有受到威胁”。当然，自从罗伯茨（Roberts）的论文将这只猫列为Hooghly鸽子以来，恒河鲨鱼的命运可能已经发生了变化，但即使在2006年，人们也普遍认为它是非常稀缺的。

所以你有它。恒河鲨鱼：一种稀有，致命的淡水鱼，仅在孟加拉湾内的海洋/咸淡生境中发现，从来没有伤及苍蝇，并带有“好”的俗称。每个人都有吗？好的！我很高兴我们解决了这个问题。