What’s as big as a polar bear, swallows its prey whole, and swims at 40 miles an hour? It’s not a shark or a killer whale, it’s the Atlantic bluefin tuna, the largest and longest-lived of the 15 tuna species. The Atlantic bluefin has a unique set of adaptations that make it one of the most dominant predators in the ocean.
It starts as a tiny hatchling in the Gulf of Mexico or the Mediterranean Sea, no bigger than a human eyelash. Within its first year of life, it develops something known as regional endothermy – the ability to regulate its body temperature. An Atlantic bluefin gets oxygen from cold ocean water using its gills, this process cools its blood. Then, heat the tuna generates swimming and hunting warms the blood.
In most fishes, this heat would be lost back out into the ocean through the gills. But in the Atlantic bluefin, a mechanism called countercurrent exchange traps the heat. Cold blood on its way to the large swimming muscles, passes close to warm blood leaving those muscles, in a specialized network of blood vessels known as a rete mirabile. Here the heat “jumps” to the cold blood and stays in the body.
This makes bluefin one of the few warm-blooded fishes, a huge advantage in the marine environment. Cold-blooded animals whose body temperature depends entirely on the environment become sluggish in colder waters. But a bluefin’s ability to keep warm means it has sharper vision, can better process information, and can swim faster than its prey.
It thrives in cold, deep, subarctic water. Thanks to their warm bloodedness, their powerful muscles, and their streamlined torpedo shape with fins that fold into grooves to reduce drag, bluefin tuna can reach speeds few other animals can match. Their maximum speed of 40 miles per hour is faster than that of a great white shark or orca whale, and even at their comfortable cruising speed, they can cross the Atlantic in a couple months.
All this swimming requires a great deal of oxygen, but the bluefin is adapted for this as well. The faster it swims, the more water passes over its gills, and the more oxygen it can absorb from that water.
This need for a constant flow of water means the tuna must always remain on the move. It also means bluefin cannot suck prey into their mouths the way most other fishes do. Instead, they must chase down their prey with their mouths open. They eat smaller prey than most predators their size, including squid, crustaceans, and smaller fish species like mackerel.
The bluefin’s temperature-regulating ability doesn’t just make it a superior hunter – it gives it nearly unlimited range. As soon as they’re strong enough to swim against the current, Atlantic bluefin leave the warm waters of their spawning grounds and spend their lives hunting all over the Atlantic Ocean.
Tunas from both the Gulf of Mexico and the Mediterranean Sea frequent the same feeding grounds and range from Brazil and Texas to Iceland and Senegal and beyond. But when the time comes to reproduce around age 10, they always return to their sea of origin. Here, groups of males and females release millions of eggs and sperm into the water. They’ll migrate back and forth between feeding and spawning grounds annually for the rest of their lives.
Atlantic bluefin can live for over 40 years, growing all the while. The largest specimens are tens of millions of times heavier than when they hatched. The same huge size that makes bluefin tuna indomitable in the ocean has made them vulnerable to one predator in particular: us.
Humans have a long history of fishing Atlantic bluefin – it’s even stamped on ancient Greek coins. But in recent decades, demand has skyrocketed as bluefin are hunted for sashimi, sushi, and tuna steaks. An individual fish can sell for $10,000 or more, promoting overfishing and illegal fishing.
But if recent conservation efforts are redoubled and quotas are better enforced, bluefin populations can begin to recover.
WORD BANK:
swallow /ˈswɒl.əʊ/ [B2] (v): nuốt
prey /preɪ/ [C2] (n): con mồi
killer whale /ˈkɪl.ə ˌweɪl/ (n): cá voi sát thủ
Atlantic bluefin tuna /ətˈlæn.tɪk ˌbluː.fɪn ˈtʃuː.nə/ (n): cá ngừ vây xanh Đại Tây Dương
adaptation /ˌæd.əpˈteɪ.ʃən/ [C1] (n): thích nghi
dominant /ˈdɒm.ɪ.nənt/ [C1] (adj): vượt trội/nổi bật
predator /ˈpred.ə.tər/ [C1] (n): động vật săn mồi
hatchling /ˈhætʃ.lɪŋ/ (n): mới sinh/mới nở
the Gulf of Mexico /ˌɡʌlf əv ˈmek.sɪ.kəʊ/ (n): Vịnh Mexico
the Mediterranean Sea /ˌmed.ɪ.tərˈeɪ.ni.ən/ (n): Biển Địa Trung Hải
endothermic /ˌen.dəʊˈθɜː.mɪk/ (adj): hấp thụ nhiệt
regulate /ˈreɡ.jə.leɪt/ [C1] (v): điều hòa/điều chỉnh
gill /ɡɪl/ (n): mang cá
generate /ˈdʒen.ə.reɪt/ [B2] (n): tạo ra
mechanism /ˈmek.ə.nɪ.zəm/ [C1] (n): cơ chế
countercurrent exchange (n): trao đổi ngược dòng
muscle /ˈmʌs.əl/ [B2] (n): cơ băp
specialized /ˈspeʃ.əl.aɪzd/ (adj): chuyên dụng/chuyên môn
blood vessel /ˈblʌd ˌves.əl/ (n): mạch máu
rete mirabile (n): phức hợp động mạch và tĩnh mạch
marine environment /məˈriːn ɪnˈvaɪ.rən.mənt/ (n): môi trường biển
depend /dɪˈpend/ [B1] (v): phụ thuộc
entire /ɪnˈtaɪər/ [B2] (adj): hoàn toàn/toàn bộ
environment /ɪnˈvaɪ.rən.mənt/ [B1] (n): môi trường
sluggish /ˈslʌɡ.ɪʃ/ (adj): chậm chạp
thrive /θraɪv/ [C1] (v): phát triển/lớn lên
subarctic /sʌbˈɑːk.tɪk/ (adj): cận Bắc Cực
torpedo /tɔːˈpiː.dəʊ/ (n): ngư lôi
fin /fɪn/ (n): vây
fold /fəʊld/ [B1] (v): gập lại
groove /ɡruːv/ (n): rãnh
drag /dræɡ/ (n): lực cản
orca whale /ˈɔː.kə/ (n): cá voi sát thủ
cruising speed /ˈkruː.zɪŋ ˌspiːd/ (n): tốc độ
absorb /əbˈzɔːb/ [B2] (v): hấp thụ
constant /ˈkɒn.stənt/ [B2] (adj): liên tục/thường xuyên
suck /sʌk/ [C2] (v): hút (bằng miệng)
crustacean /krʌsˈteɪ.ʃən/ (n): loài giáp xác
mackerel /ˈmæk.rəl/ (n): cá thu
superior /suːˈpɪə.ri.ər/ [C1] (adj): xuất sắc/vượt trội
unlimited /ʌnˈlɪm.ɪ.tɪd/ [B2] (adj): không giới hạn
the current /ˈkʌr.ənt/ (n): dòng chảy/dòng hải lưu
spawning ground /ˈspɔː.nɪŋ ˌɡraʊnd/ (n): nơi sinh đẻ/nơi sinh ra
Atlantic Ocean /ətˈlæn.tɪk/ (n): Biển Đại Tây Dương
reproduce /ˌriː.prəˈdʒuːs/ [C2] (v): sinh sản
origin /ˈɒr.ɪ.dʒɪn/ [B2] (n): nguồn gốc/nơi sinh ra
release /rɪˈliːs/ [C1] (v): thả ra
sperm /spɜːm/ (n): tinh trùng
migrate /maɪˈɡreɪt/ (v): di cư
specimen /ˈspes.ə.mɪn/ [C2] (n): con mẫu/mẫu vật
indomitable /ɪnˈdɒm.ɪ.tə.bəl/ (adj): không thể bị chế ngự/khuất phục
vulnerable /ˈvʌl.nər.ə.bəl/ [C2] (adj): dễ bị tấn công/dễ tổn thương
stamp /stæmp/ [B2] (v): đóng dấu
skyrocket /ˈskaɪˌrɒk.ɪt/ (v): tăng vọt
individual /ˌɪn.dɪˈvɪdʒ.u.əl/ [B2] (n): cá thể
promote [B2] (v): thúc đẩy
overfishing /ˌəʊ.vəˈfɪʃ.ɪŋ/ (n): khai thác (đánh bắt) cá quá mức
illegal /ɪˈliː.ɡəl/ [B2] (adj): bất hợp pháp
conservation /ˌkɒn.səˈveɪ.ʃən/ [B2] (n): bảo tồn
effort /ˈef.ət/ [C2] (n): nỗ lực
redouble /ˌriːˈdʌb.əl/ (v): tăng cường
quota /ˈkwəʊ.tə/ (n): hạn ngạch
enforce /ɪnˈfɔːs/ [C1] (v): thực thi
ỦNG HỘ READ TO LEAD!
Chào bạn! Có thể bạn chưa biết, Read to Lead là một trang giáo dục phi lợi nhuận với mục đích góp phần phát triển cộng đồng người học tiếng Anh tại Việt Nam. Chúng tôi không yêu cầu người đọc phải trả bất kỳ chi phí nào để sử dụng các sản phẩm của mình để mọi người đều có cơ hội học tập tốt hơn. Tuy nhiên, nếu bạn có thể, chúng tôi mong nhận được sự hỗ trợ tài chính từ bạn để duy trì hoạt động của trang và phát triển các sản phẩm mới.
Bạn có thể ủng hộ chúng tôi qua 1 trong 2 cách dưới đây.
– Cách 1: Chuyển tiền qua tài khoản Momo.
Số điện thoại 0947.886.865 (Chủ tài khoản: Nguyễn Tiến Trung)
Nội dung chuyển tiền: Ủng hộ Read to Lead
hoặc
– Cách 2: Chuyển tiền qua tài khoản ngân hàng.
Ngân hàng VIB chi nhánh Hải Phòng
Số tài khoản: 012704060048394 (Chủ tài khoản: Nguyễn Tiến Trung)
Nội dung chuyển tiền: Ủng hộ Read to Lead
