The ocean has hammerheads, sawsharks and even spadenose sharks. It seems there’s a shark for every task. Indeed, these predators each have specific roles to play in their ecosystems. A healthy ocean requires sharks of different shapes and sizes.

海洋里有双髻鲨、锯鲨，甚至还有糖鲨。似乎每个任务都有一个鲨鱼。事实上，这些掠食者在各自的生态系统中都扮演着特定的角色。健康的海洋需要不同形状和大小的鲨鱼。

Unfortunately, sharks’ diverse contributions are under threat from overfishing, climate change, habitat loss, coastal development, shipping activities and more. That’s why an international team of scientists contend that shark conservation must go beyond simply protecting shark populations — it must prioritize protecting the ecological roles that sharks fill. These findings come from a study published in Science that sheds new light on the role sharks play in healthy oceans, and why size should be a factor in conservation decisions.

不幸的是，鲨鱼的多样性正受到过度捕捞、气候变化、栖息地丧失、沿海开发、航运活动等因素的威胁。这就是为什么一个国际科学家团队认为，鲨鱼保护必须超越简单地保护鲨鱼数量——它必须优先保护鲨鱼所扮演的生态角色。这些发现来自发表在《科学》杂志上的一项研究，该研究揭示了鲨鱼在健康海洋中扮演的角色，以及为什么大小应该是保护决策的一个因素。

The largest individuals of apex species like tiger sharks and great whites play an oversized role in healthy oceans. But they are often the most affected by fishing. Big sharks help maintain balance through their eating habits. Sometimes their sheer size is enough to scare away prey that could over-consume seagrass and other plant life needed for healthy oceans.

像虎鲨和大白鲨这样的顶级物种的最大个体在健康的海洋中扮演着巨大的角色。但它们往往是受捕鱼影响最大的。大鲨鱼通过它们的饮食习惯来维持平衡。有时，它们的体型足以吓跑那些可能过度消耗健康海洋所需的海草和其他植物的猎物。

“Despite the fact the sharks are well recognized and appreciated in popular media and lore, their importance in maintaining ecosystem health was understudied and underappreciated,” said co-author Jennifer Caselle, a marine biologist at UC Santa Barbara. “We show that sharks are critical components to ecosystem function, making their global population declines particularly worrisome. Conservation measures to protect sharks are urgently needed.”

“尽管鲨鱼在大众媒体和爱情中得到了很好的认可和赞赏，但它们在维持生态系统健康方面的重要性却没有得到充分的研究和重视，”加州大学圣巴巴拉分校的海洋生物学家珍妮弗·卡塞勒说。“我们表明鲨鱼是生态系统功能的关键组成部分，使它们的全球数量下降特别令人担忧。我们迫切需要采取保护鲨鱼的措施。”

Besides playing critically important roles within the food web, reef sharks feed in offshore waters and bring nutrients back to the reef. Others move around nutrients that are used at the base of the food chain. Sharks can also serve as food for other species and even as scratching posts for fish to remove parasites. The problem is that shark abundance, for oceanic species, has plummeted by 71 percent in the past 50 years. Populations of the top five reef shark species have declined by 63 percent. As their numbers nosedive, their important roles in ocean health are also lost.

除了在食物网中扮演至关重要的角色外，礁鲨还在近海水域觅食，并将营养物质带回珊瑚礁。其他的则是在食物链的底部移动营养物质。鲨鱼也可以作为其他物种的食物，甚至可以作为鱼类清除寄生虫的抓挠柱。问题是，在过去的50年里，海洋物种的鲨鱼数量下降了71%。排名前五的礁鲨种群数量下降了63%。随着它们数量的锐减，它们在海洋健康中的重要作用也随之消失。

“It’s time to have a conversation about everything sharks are doing to maintain ocean health so we can better prioritize conservation efforts and have the biggest impact,” said lead author Simon Dedman, a researcher at Florida International University, which led the study team.

“现在是时候谈谈鲨鱼为维持海洋健康所做的一切了，这样我们就能更好地优先考虑保护工作，产生最大的影响，”该研究的主要作者、佛罗里达国际大学的研究人员西蒙·戴德曼说。

The researchers built upon a variety of datasets and previous studies to estimate global shark population trends. For instance, former UC Santa Barbara doctoral student Erin Dillon discovered that she could use fossil shark scales excavated during digs in prehistoric reefs in the Caribbean to estimate the region’s shark populations. The shape and prevalence of different shark scales enabled her to estimate the type and abundance of sharks going back almost 6,000 years. By comparing data from multiple sites in this new report, she was able to document that shark abundance in the region declined by approximately 70 percent since prehistoric times.

研究人员基于各种数据集和以前的研究来估计全球鲨鱼数量的趋势。例如，加州大学圣巴巴拉分校的前博士生艾琳·狄龙发现，她可以利用在加勒比海史前珊瑚礁挖掘中挖掘出的鲨鱼鳞片化石来估计该地区的鲨鱼数量。不同鲨鱼鳞片的形状和流行程度使她能够估计近6000年前鲨鱼的类型和数量。通过比较这份新报告中多个地点的数据，她能够证明该地区的鲨鱼数量自史前时代以来下降了大约70%。

Fortunately, it is not bad news for all sharks. There are a few promising instances where smart and responsible management appears to be helping sharks — and the jobs they perform in nature — to recover. Co-author and UC Santa Barbara professor Douglas McCauley, who studies white sharks in Santa Barbara using drones and AI, cites their situation as a hopeful example. In addition to laying out a roadmap to see more such shark success stories, this new research also provides advice on how we can share our ocean backyards with sharks. “We’ve learned a lot about how to co-exist with ecologically important species that we’ve brought back on land, like bears and wolves, that can help us better share space with these recovering ocean wildlife,” he said.

幸运的是，这对所有的鲨鱼来说都不是坏消息。有一些有希望的例子表明，明智和负责任的管理似乎正在帮助鲨鱼——以及它们在自然界中所做的工作——恢复。合著者、加州大学圣巴巴拉分校教授道格拉斯·麦考利(Douglas McCauley)利用无人机和人工智能研究圣巴巴拉的白鲨，他把它们的情况作为一个充满希望的例子。除了为看到更多这样的鲨鱼成功故事制定路线图外，这项新的研究还为我们如何与鲨鱼分享我们的海洋后院提供了建议。他说:“我们已经学到了很多关于如何与我们带回陆地的生态重要物种共存的知识，比如熊和狼，这可以帮助我们更好地与这些正在恢复的海洋野生动物共享空间。”

The issue of shark conservation becomes all the more critical as global temperatures increase, leading some sharks to head into new areas where they can find the temperatures they can thrive in.

随着全球气温的升高，鲨鱼保护的问题变得更加重要，导致一些鲨鱼前往新的区域，在那里它们可以找到它们可以茁壮成长的温度。

“This study verifies what we’ve long suspected – sharks are critical to ocean health,” said Lee Crockett, executive director of the Shark Conservation Fund, which funded the study. “This landmark study serves as confirmation that marine conservationists, philanthropists, policymakers and the public alike need to recognize that sharks are keystone species that have a now-proven significant effect on marine environments.”

“这项研究证实了我们长期以来的怀疑——鲨鱼对海洋健康至关重要，”资助这项研究的鲨鱼保护基金的执行董事李·克罗克特说。“这项具有里程碑意义的研究证实，海洋保护主义者、慈善家、政策制定者和公众都需要认识到，鲨鱼是 关键物种，现已被证明对海洋环境有重大影响。”

With the expansion of blue economy industries like aquaculture and tourism, people’s encounters with sharks will likely increase. Finding a balance that protects the sharks most needed for healthy oceans is hitting a critical point.

随着水产养殖和旅游业等蓝色经济产业的扩张，人们与鲨鱼的接触可能会增加。找到一种平衡，保护健康海洋最需要的鲨鱼，这已经到了一个临界点。

“National and international policy must focus on actions that rebuild populations and restore sharks' functional roles,” said Mike Heithaus, study co-author and FIU marine ecologist. “That requires action to increase both spatial measures like marine protected areas and fisheries management measures like catch/size limits and gear limitations. If people want healthy oceans, we need healthy shark populations.”

“国家和国际政策必须把重点放在重建种群和恢复鲨鱼功能角色的行动上，”该研究的合著者、国际海洋研究所的海洋生态学家迈克·海瑟斯说。“这需要采取行动，增加海洋保护区等空间措施和渔业管理措施，如捕捞量/大小限制和渔具限制。如果人们想要健康的海洋，我们就需要健康的鲨鱼种群。”