7.The Yellowfin Tuna

7.黄鳍金枪鱼

This tuna is a member of the same family as the Bonito and schools in waters of both northern and southern hemispheres. Reaching an average weight of nearly 400 pounds in less than eight years, these schooling¹ fish are popular with fishermen. Pelagic in preference, the Yellowfin is designed for long distance migrations² and sustained speed. It's been clocked at speeds of nearly 50 miles per hour for prolonged periods of time. A biological design feature makes this possible. By resting their pectoral fins³ in special grooves⁴ along the sides of their bodies, they present a streamlined profile to the current. This helps to reduce drag, so that their torpedo-shaped bodies cut through the water with greater ease and less loss of energy.

黄鳍金枪鱼和鲣鱼隶属于同一种类，都是群居型鱼类，南北半球都能看到它的身影。这种鱼可在8年的时间里长到400英镑，广受渔民欢迎。另外为了适应深海的情况，黄鳍金枪鱼能够长途迁徙，并在途中全程保持高速游行。它可以长时间以每小时50英里的速度游动，这要得益于它独特的生理结构：在它们身体两侧的凹槽中长有胸鳍，当黄鳍金枪鱼在洋流中游动时胸鳍可以使身体呈流线型来减少游动时产生的阻力。这样一来，它们那鱼雷型的鱼身就可以轻而易举的穿透水流，进而减少游动时的体力消耗。

While they seem to favor squid and crustaceans⁵, Yellowfins are not picky eaters. They will often forage⁶ on whatever is readily available in their vicinity. Because they put on weight quickly and grow to a respectable size of about 200 kilograms, they're a favorite target for fishing companies. They tend to school strongly and can be found in the open tropical or subtropical waters of oceans, though they avoid the more closed environments of the Mediterranean⁷ and Black Seas. They have been placed on a list of possibly endangered species—meaning that if culling⁸ continues apace, their numbers will soon be depleted⁹ beyond their ability to sufficiently¹⁰ spawn¹¹ replacements¹². In the 1950s, purse seines were used to harvest massive numbers of Yellowfin, by exploiting the tendency for dolphins to travel with the schools. The careless tactics of fishers led to hundreds of thousands of dolphins drowning each year, due to net entanglement¹³. Hence, both legislation prohibiting the death of dolphins and the development of dolphin safe nets was put forward several decades later.

虽然黄鳍金枪鱼看起来更喜欢吃乌贼和甲壳类动物，但其实它们什么都吃。它们通常会竭尽所能地寻找身边一切可以吃的东西。因此，它们的体重会以惊人的速度增长，可达200公斤，这也使它们也成为了其他捕食者们的最爱。黄鳍金枪鱼通常是群居性鱼类，生活于热带及亚热带水域，在地中海及黑海等封闭性水域中鲜有它们的身影。黄鳍金枪鱼被列为潜在濒危物种。这意味着如果继续维持现状，它们的消亡速度会超过繁殖速度。20世纪50年代，人们利用海豚会追寻鱼群的特点通过围网捕鱼法来捕捞大群的黄鳍金枪鱼。但当时的渔民们疏于考虑，导致每年有成百上千的海豚因被渔网缠住而丧生。因此，在之后的几十年中，人们双管齐下，一方面通过立法保护，另一方面研制防纠缠渔网，共同保护海豚。

6.The Pilot Whale

6.巨头鲸

zThese ocean mammals are also closely related to dolphins, much like the killer whale. They exhibit advanced intelligence and social skills, making them the unfortunate targets of human whaling endeavors. Although they're known to feast upon cuttlefish¹⁴, octopus¹⁵, and small fish, their favorite prey¹⁶ is squid. They also have fewer teeth than other members of the dolphin family—40 to 48 as opposed to the usual 120. Scientists believe that this may be an adaptation to their feeding niche—because they subsist¹⁷ almost exclusively on squid and related animals.

巨头鲸和海豚是近亲，但更像虎鲸一点。它们表现出超群的智慧以及社会能力让它们不幸地成为捕鲸人的狩猎目标。人们都熟知巨头鲸以墨鱼、章鱼以及一些小鱼为食，但是它最喜欢的还是乌贼。它们的牙齿较海豚科其他成员要少一些——通常其他成员有120颗，但巨头鲸只有40到48颗。科学家们认为这是为了适应它们的捕食习惯——因为它们几乎只依靠乌贼和一些其他同类生物维生。

Their highly social nature is evident in the size of their living groups—up to 90 related individuals who work together to subsist—which may be found in every ocean of the world. Working together, they track and corral their prey before feasting. Because they must often travel long distances, and require bursts of speed to close in on prey species, they have been observed diving to incredible depths at speeds that seem counterintuitive. This is significant when you consider that, although both air and water are technically¹⁸ classified as liquid mediums, water is 750 times denser¹⁹ than air. While they have been clocked at 47 miles per hour when leaping, what's truly astonishing is that they perform bursts of speed when they close in on their prey at great depths—read that as up to 3200 feet beneath the surface. Researchers from La Laguna University in Tenerife tagged 23 short finned²⁰ Pilot Whales with suction cup monitors to discover their behavior so far below the surface, and found to their amazement²¹ that the whales behaved more like cheetahs²². The researchers were able to record average speeds of 19.2 feet per second, with amazing an 28.8 feet per second speed achieved just before the whales reached the deepest parts of their dives. So while these incredible speeds are not sustained, they are, nonetheless, amazing.

巨头鲸高度的社会性在其生活群体的规模大小上得以体现——每个大洋都能看到90头左右的巨头鲸一起捕食生存。它们会齐心协力追踪围捕猎物，通常要游很久，又需要爆发力追捕，人们曾经观察到巨头鲸可以极速下潜到令人难以置信的深度，这简直逆天了。仔细想想你就会觉得这太不可思议了，虽然从学术上来说空气和水都是液体传播媒介，但是水的密度可是空气的750倍。它们跳跃时的速度可达到47英里每小时，真正让人震惊的是，它们可以在三千英尺的深海中突然全速追捕猎物。来自内特利费语言大学的研究学者给23头短鳍巨头鲸安上吸盘监视器观察它们在深海的一举一动。他们惊奇地发现这些巨头鲸就像一头猎豹。研究人员记录显示是平均游速可达每秒19.2英尺，但是在巨头鲸在到达它能够潜到的最深的地方之前速度已经达到了28.8英尺每秒。虽然这惊人的速度没有保留下来，但是不管怎么说，巨头鲸真的太神奇了。