1、海洋哺乳動(dòng)物, ,海洋哺乳動(dòng)物和陸地哺乳動(dòng)物一樣，都使用肺部呼吸，這一點(diǎn)可能很多人都不了解。而且生物學(xué)家認(rèn)為，所有的海洋哺乳動(dòng)物最早都源于陸地，他們的祖先因?yàn)槭澄镄枰蛘叨惚懿东C者進(jìn)入了海洋，為了適應(yīng)海洋生活，四肢變成了鰭形，身體進(jìn)化成流線形，令游水捕獵時(shí)更便捷。 此外，海洋哺乳動(dòng)物的尾鰭是上下移動(dòng)，并不是和魚一樣左右移動(dòng)，典型的案例就是海豚。,海洋哺乳動(dòng)物與其它海洋動(dòng)物的不同, 使用肺部呼吸，不是鰓。需要上岸或者水面呼吸氧氣； 有毛發(fā)?；蛎?，就算是鯨豚目里的物種也有少量的毛，其分布位置是頭部跟口的附近。 皮下脂肪比較厚，可以防止水份及熱量流失； 全部都是胎生。海洋哺乳動(dòng)物多也只是生一胎，其

2、幼兒開頭的時(shí)候也有喝奶的需要。它們的奶脂肪含量比其他陸上哺乳動(dòng)物都要高，差不多接近四至五成；,海洋哺乳動(dòng)物分類,(約90種),(19種),(5種海獅，9種海狗),(3種),海牛目(Sirenian),特征: 體型較大 (儒艮，3m，420kg；海牛，4.5m，600kg) 毛發(fā)少； 植食性； 有趾甲 (海牛) 包括: 海牛 Manatees (3種) 儒艮 Dugongs (1種),Million of years before present,80,60,40,20,0,Ancestral mammals,Asian elephant,African elephant,tmammoth,tm

3、astadon,Dugong,tStellars sea cow,West Indian manatee,Brazilian manatee,West African manatee,Other mammals,Relationship between Sirenians and elephants (mtDNA),種類： 北美海牛(加勒比海牛)； 西非海牛； 南美海牛(巴西海牛)-淡水 槳狀尾巴 嘴唇可卷曲攝食 體型較儒艮大 少有天敵 威脅: 船舶 生境破壞,海牛 Manatee,Manatee,9.8 ft, 800-1200lbs,3,000 in U.S.,素食主義者，每天攝食50Kg

4、,小海牛跟隨母海牛5年,斯特勒海牛,體長(zhǎng)7.5米以上，體重4噸以上； 白令海西部 Commander群島； 1741年發(fā)現(xiàn)，1768年滅絕。,分布: 西印度洋、西太平洋的近岸和海島水域 專性的海洋生物 叉狀尾，與海豚相似 喜食海草的根狀莖 虎鯊為其攝食者,儒 艮,儒艮分布 東非，西太平洋海島,10,000,食肉目,食肉目共同特征： 具有顯著的犬齒 包括: 海獺Sea otters 北極熊Polar bears 鰭足類(鰭足亞目) Pinnipeds 海象 Walrus 海獅 Seals 海豹 Sea lions/fur seals,Hawaiian Monk Seal,海獺 Sea Otter

5、,分布于北太平洋寒冷水域 394,000 hairs/cm2 皮下脂肪少 雌性 45lbs; 雄性 65 lbs 食物: 海膽、鮑魚、貽貝、蛤、螃蟹、海螺 和其它約40 種海洋生物,會(huì)使用工具 能潛到 330 ft 在近岸的海藻森林休息,Pop size: 22,000 to 27,000 Weight: 550 to 1,700 pounds,北極熊 Polar Bear,Polar Bear,Ursa maritimus United States, Canada, Russia, Greenland and on the Arctic islands of Norway Male: 10

6、 feet tall and weigh over 1400 lbs Female: 7 feet and weigh 650 lbs wild polar bears live up to age 25.,Good swimmers Thick blubber Thick fur,Polar bears Polar bears are the least adapted to the marine lifestyle Land animals that are adapted to the cold,Considered marine mammals because they feed al

7、most exclusively on marine organisms Very good swimmers, but cant dive below surface well Hunt seals and walruses, occasionally cetaceans,Range: Circumpolar in Arctic Range depends on sea ice,normal range occasional range over pack occasional range over permanent ice,Family Phocidae 海豹科,Family Otari

8、idae 海獅科,Family Odobenidae 海象科,Hawaiian Monk Seal,鰭足類 Pinnipeds,鰭足類亞目 (seals, sea lions, & walruses) 海豹科 - true, earless seals 海獅科 - eared seals and sea lions 海象科 - walruses 34 known species Evolved 20 mya from Order Carnivora (ancestors of dogs and bears) Differ in possession of external ears and m

9、ode of locomotion,海豹與海獅的不同,Family Phocidae,Hawaiian Monk Seal,Lack external ears Hind flippers propel them while swimming Front flippers act as rudders Travel on land is difficult (wiggle),Sea Lion,Family Otariidae,Eared seals Front flippers propel animal when swimming Rear flippers act as rudders F

10、airly mobile on land,Walrus,Family Odobenidae,Found in Arctic region Lack external ears Paddle with front flippers Rear flippers act as a rudder Fairly mobile on land,Pacific walrus is in lavender, Atlantic walrus is in rose.,海象分布,Walrus Facts,Location: Bering sea, Pacific Ocean, Atlantic Ocean, Arc

11、tic Ocean Pop Size: 250,000 Size: Weight: 2,000-3,500 lb. Breeding: Sexually mature late females, usually 6-7 years males, 15 years. Produce few offspring,Walrus Facts,Lifestyle Habit: Gregarious, living mainly in herds. Diet: Benthic suction feeders. Feed mainly on bivalve mollusks, but also other

12、invertebrate marine animals, fish, sometimes seals and whales. Predators: polar bears, killer whales, and humans Lifespan: Up to 40 years.,Walrus Facts,Swim speed: 7-35 kph 長(zhǎng)牙 Tusks: Both male these pockets facilitate sleep in the water in an upright position May be used to amplify mating calls,鯨 目

13、鯨魚、海豚與鼠海豚,Age:始新世早期 , 5千萬年前 Location: 巴基斯坦 1979年發(fā)現(xiàn),巴基原鯨 Pakicetus attocki,陸行鯨 Ambulocetus natans,4900萬年前 1994年發(fā)現(xiàn)于巴基斯坦,Whale Evolution,Ambulocetus natans in action. A reconstruction of an early close cousin of whales.,鯨 目,共同特征: 頭頂具有噴水孔； 頭骨壓縮 (流線體型) 毛發(fā)少 包括: Whales, dolphins, and porpoises,鯨的兩個(gè)亞類,齒鯨 Ec

14、holocate (send sound through water) Includes killer whale, sperm whale, dolphins, porpoises, and many others 須鯨 Have rows of baleen plates instead of teeth Includes blue whale, finback whale, humpback whale, gray whale, and many others,海豚: 拉長(zhǎng)的吻 鐮刀狀背鰭 圓錐形牙齒,Killer whale jawbone,海豚與鼠海豚的區(qū)別,海豚與鼠海豚的區(qū)別,鼠海

15、豚: 鈍圓吻部 三角形的背鰭 鏟形牙齒,獨(dú)角鯨海洋中的獨(dú)角獸,45米，1噸重； 23米長(zhǎng)牙,藍(lán)鯨,最大33米，190噸，最大動(dòng)物 聲音155188分貝，發(fā)出最大聲音動(dòng)物,座頭鯨 海上歌唱家,駝背鯨 南北洄游 8000km 氣泡網(wǎng)圍捕魚群 18種不同頻率音調(diào),抹香鯨 Deepest Diver,(3km1.5 miles),虎鯨 海洋之王,集群生活 捕食魚類、烏賊、海龜、企鵝、海獅、海豹、大型須鯨和抹香鯨 沒有天敵 100歲左右壽命 810米，9噸 智力高，表演明星,海洋哺乳動(dòng)物學(xué),游泳 海獅 35kph 藍(lán)鯨和虎鯨 50kph 海豚 64kpn 潛水 海獺 45min，55m 鰭足類 通常 3

16、0min，150250m 北方象海豹 400m 最深1500m 威德爾海豹 1h13min， 575m 長(zhǎng)須鯨 100m 海豚 300m 抹香鯨 2250m或更深,海洋哺乳動(dòng)物對(duì)潛水活動(dòng)的適應(yīng) 單次呼吸空氣交換量大，最高達(dá)90% (人類約20%)； 血液能攜帶更多氧，血紅蛋白； 肌肉中肌紅蛋白含量高； 潛水時(shí)心率減慢，減少耗氧； 血液分流，維持大腦和心臟供氧； 肺可塌陷，潛水時(shí)空氣不接觸血管，避免氮?dú)膺M(jìn)入。,紡錘、流線型體型 趨同進(jìn)化,Echolocation Sensing environment Produce clicks that travel out, hit objects and

17、 reflect back Produced by a structure in the airway called the “monkey lips” Sound received through the lower jaw Low frequency clicks travel further but can only be used for big objects High frequency clicks can discriminate small objects but dont travel as far,鯨的遷移,Whale Carcass Removal,Breaching,

18、When Whales leap in the air and loudly crash on the surface of the water. This can be a warning signal, getting rid of external parasites, fun, or a way of scanning the surface.,海洋哺乳動(dòng)物究竟有多聰明？,條件性學(xué)習(xí) 僅在進(jìn)行某一行為后獲得報(bào)酬（如獎(jiǎng)賞食物）才會(huì)學(xué)習(xí) 許多動(dòng)物包括老鼠、鳥甚至無脊椎動(dòng)物可以進(jìn)行條件性學(xué)習(xí) 鯨類可通過觀察很快學(xué)習(xí)，會(huì)自然地模仿人類活動(dòng)。海豚還會(huì)模仿海豹、海龜甚至沖浪者的行為。,通過對(duì)寬吻海

19、豚分辨和解決困難能力的研究發(fā)現(xiàn)，它們的智力“介于狗和黑猩猩之間”。 但是智力是非常人類化的概念，拿它去評(píng)價(jià)動(dòng)物是不公平的。,一個(gè)世紀(jì)以前，巴西 漁民和海豚建立特殊的伙伴關(guān)系。海豚探測(cè)到魚群，并驅(qū)趕到漁民的網(wǎng)里，然后從漁民處得到捕獲的魚。 1871-1884年，新西蘭海岸一只海豚為經(jīng)過的海船領(lǐng)航。 太平洋海洋基金會(huì)歐文斯博士花了3年時(shí)間，教會(huì)兩只海豚700個(gè)英文詞匯。,約翰.禮萊博士是一名標(biāo)新立異的但是卻非常專業(yè)的神經(jīng)生理學(xué)家），他花數(shù)年時(shí)間試圖教海豚說話和理解英語。 1968年，他宣布他的實(shí)驗(yàn)獲得了部分的成功。然后他釋放了他的海豚，他認(rèn)為他沒有權(quán)利因?yàn)樽约喝⑦@些海豚圈養(yǎng)在集中營(yíng)里。禮萊博士認(rèn)

20、為海豚比人類有更高形式的意識(shí)，并且它們的語言和理解力是非人類的，但卻是高智慧的，帶有邏輯性的。 美國塔夫斯大學(xué)教授巴迪奧博士，發(fā)明了一種通電的翻譯機(jī)，可以將人類的發(fā)音轉(zhuǎn)化成海豚的哨聲。通過人工語言，水兵可以用無線電指揮海豚在水下進(jìn)行工作。,The U.S. Navy Marine Mammal Program（NMMP）,Program was founded in the 1960s Originally studied hydrodynamics of dolphins Trainability, diving ability, and intelligence of dolphins l

21、ed to the Marine Mammal program,The U.S. Navy Marine Mammal Program,Many types of marine mammals were originally used Animals mainly trained for mine-hunting, object recovery, and swimmer detection Each system has a different military designation Program was only recently de-classified by the Navy,海

22、 豚,Only part of the program Used for mine-hunting and swimmer detection Animals are bred within the program Used because of their powerful sonar,海 獅,Used for fleet ops and object recovery Purchased instead of bred Easier to transport than dolphins,食 物,Sea lions and dolphins primarily eat capelin, he

23、rring, squid, and mackerel Each animal has a specific diet Fish are restaurant-quality Average dolphin eats 9 pounds of fish every day,訓(xùn) 練,Dolphins cannot understand vocal signals A trainer communicates with dolphins using learned hand signals Dolphins start training very young The most important an

24、d hardest thing for a dolphin to learn is voluntary beaching This behavior is crucial for deployments and routine checks such as weight checks and medical procedures,訓(xùn) 練,Sea lions are bought rather than bred The bought sea lions are a year old or more and their training starts immediately Sea lions

25、are first taught to sit on a stand and perform a basic med check After this, they are assigned to the system they will continue training with,Mark-4, 7, & 8 Systems,These Mark systems deal with mine-hunting Only dolphins are included in these systems because of their sonar Mark 4 dolphins detect and

26、 mark floating or tethered mines Mark 7 dolphins detect and mark mines on the sea floor Mark 8 dolphins are trained to rapidly mark out a safe passage for the initial landing of troops ashore,Mark-6 System,Mark-6 uses both sea lions and dolphins as sentries They commonly guard harbors and Naval ship

27、s Both animals are trained to patrol designated areas When an unauthorized diver or swimmer is found, the animal marks them so that they can be picked up,Mark-5,Mark-5 is dedicated to the recovery of de-activated mines and objects Only sea lions are used in this system Sea lions are used to do this

28、job because human divers cant compare,運(yùn) 輸,Key part of training Naturally difficult to train dolphins to get used to transportation Sea lions are extremely easy to transport by comparison During deployments, portable pools have to be set up for animals Both dolphins and sea lions can remain out of wa

29、ter,Medical,Medical checks are routine and often the first thing taught to animals Daily checks include a full body overview Less common checks include weight, ultrasound, and blood-taking Every animal is evaluated constantly for dietary changes Animals are kept very healthy and quite possibly recei

30、ve the best care in the U.S,Deployments,和平軍事任務(wù),海豚在和平性的軍事任務(wù)中有很大的價(jià)值：他們可以取回失蹤的武器，可以定位失蹤的炸彈和潛艇，拯救失蹤或者受困的蛙人。 在一個(gè)海軍項(xiàng)目中，一名叫塔夫的海豚定位了七個(gè)失蹤的導(dǎo)彈下水架。 1965年至1967年間，美國在試驗(yàn)“阿斯羅克”反潛火箭和“天獅星”巡航導(dǎo)彈時(shí)，海豚成功 地在60米深處找到了“阿斯羅克”反潛火箭脫落的戰(zhàn)斗部件和“天獅星”導(dǎo)彈的發(fā)射輪架。 1967年至1968年，海豚被首次用于尋找和識(shí)別同樣裝有音響信標(biāo)的教學(xué)水雷，3天內(nèi)，有一只海豚找到了17枚水雷，它們完成任務(wù)時(shí)間比一般潛水員縮短了一半。,

31、越南金蘭灣海豚偵察隊(duì),在1964年的越南戰(zhàn)爭(zhēng)期間，美軍為了對(duì)付經(jīng)常攻擊美方艦船的北越潛水員，成立了特種部隊(duì)。起初美軍曾經(jīng)試過布置陷阱網(wǎng)、利用魚叉和軍用弩等多 種辦法，但均不奏效。于是只好另想妙招，在越南金蘭灣曾部署由12名馴獸員和6只海豚組成的“水下偵察兵”分隊(duì)，用以對(duì)付企圖接近美國軍艦的越南潛水員。 經(jīng)過訓(xùn)練的海豚，一旦發(fā)現(xiàn)越南潛水員后，立即向馴獸員發(fā)出無線電信號(hào)。接到指令后，它就會(huì)飛快地追上前去，把固定在頭部類似注射器的武器插入對(duì)方體內(nèi)，并放出高壓二氧 化碳。被刺傷的人，皮下肌肉綻裂，氣體源源注入，導(dǎo)致結(jié)腸、直腸脫位而集結(jié)在一起向肛門沖去，胃部則被擠向上方，從口腔噴出。尸體因充滿氣體而浮出

32、海面。 據(jù)統(tǒng)計(jì)，在15個(gè)月內(nèi)，海豚共截?fù)袅藢?duì)方60名潛水員。北越潛水員最后只好放棄水下偷襲戰(zhàn)術(shù)。,對(duì)付伊朗海軍,1978年，美國為了維護(hù)其在海灣的利益，先后派遣40多艘艦艇、兩萬多人的軍隊(duì)參加海灣護(hù)航。美軍這一行 動(dòng)，激起了伊朗的強(qiáng)烈反抗。他們不斷派出蛙人和潛艇偷襲美軍艦隊(duì)，設(shè)置水雷等障礙封鎖航道。 美國五角大樓為了“提供水下監(jiān)督和偵察能力”，幫助駐扎在這一 地區(qū)的美海軍艦艇執(zhí)行護(hù)航任務(wù)，于10月13日將6只經(jīng)過訓(xùn)練的海豚送至海灣地區(qū)，除執(zhí)行巡邏、反潛、排雷等任務(wù)外，還執(zhí)行警戒任務(wù)。每只海豚的鼻上裝有 一只重型夾鉗，一旦發(fā)現(xiàn)敵方特工人員蓄意破壞美艦艇，它們便一擁而上，用鼻子猛擊對(duì)方，然后浮出水

33、面吼叫或用嘴拉響警報(bào)器通知艦艇上的哨兵。因此，伊朗特 工人員無法接近美艦艇。,據(jù)英國媒體報(bào)道，美軍還將炸彈固定在海豚這個(gè)“活魚雷”身上，訓(xùn)練海豚對(duì)敵方艦船進(jìn)行正面進(jìn)攻。美國媒體報(bào)道說，美軍還進(jìn)行過把定時(shí)炸彈放入海豚胃里的試驗(yàn)，測(cè)試如何才能避免海豚把炸彈吐出來。但是，這些彈藥威力不大，不能對(duì)敵方艦船予以重創(chuàng)。因此，美國中情局的專家費(fèi)時(shí)數(shù)年研究怎樣利用海豚運(yùn)載特種魚雷：讓海豚推著魚雷或使用約1米長(zhǎng)的繩子牽著魚雷前進(jìn)，當(dāng)它觸及敵方艦船船舷時(shí)，引爆裝置就被啟動(dòng)。 1984年美媒稱，美海軍曾經(jīng)在尼加拉瓜秘密使用過海豚部隊(duì)。有14艘商船在尼 加拉瓜海域受到美國水雷襲擊，其中包括蘇聯(lián)的“魯甘斯克”號(hào)油船。事

34、后，美國里根政府承認(rèn)自己應(yīng)該對(duì)此負(fù)責(zé)，然而卻堅(jiān)稱投射水雷的不是海豚，而是快艇。,海豚士兵“臨陣叛變”,伊拉克戰(zhàn)爭(zhēng)期間，美軍派出了最新的掃雷艦“關(guān)島”號(hào)，該艦裝備了有號(hào)稱水下特種尖兵的海豚和全套的電腦圖像排雷系統(tǒng)，艦長(zhǎng)是莫里斯上校。 一天，艦隊(duì)所有掃雷艦和海豚一起上陣掃雷。全體海豚們保持著戰(zhàn)斗隊(duì)形向雷區(qū)游過去。莫里斯艦長(zhǎng)全神貫注地指揮著掃雷艦工作?？墒牵瑨呃着炦€沒有行駛多遠(yuǎn)，就碰到了大麻煩：一艘正在工作的掃雷艇突然觸雷挨炸，直升機(jī)不得不出動(dòng)救援。莫里斯急忙召見落水后被救的掃雷艇艇長(zhǎng)。艇長(zhǎng)也一頭霧水，明明已經(jīng)掃清左舷的水雷，正在右舷進(jìn)行掃雷作業(yè)，可是突然冒出一個(gè)水雷把船炸出個(gè)大窟窿。 就在此時(shí)，前

35、面的掃雷艦再次傳來警報(bào)，許多官兵都看到了恐怖一幕：有兩只海豚竟然拖著個(gè)重型水雷，向最前面的掃雷艇快速?zèng)_過去。掃雷艇官兵馬上向這兩只海豚開火，它們被迫扔下水雷跑開了。莫里斯艦長(zhǎng)震怒，大罵這兩只海豚是“變節(jié)者”，決定對(duì)它們執(zhí)行戰(zhàn)場(chǎng)紀(jì)律。不久，這兩只海豚像沒事兒一樣歸隊(duì)，值班軍官立刻將它們關(guān)押看管。 美軍軍法條例規(guī)定，戰(zhàn)場(chǎng)叛變者將被處以極刑。經(jīng)掃雷艦軍事委員會(huì)決定：將兩只有叛徒行為的軍事海豚予以處決，并上報(bào)艦隊(duì)司令部。艦隊(duì)司令部立即同意對(duì)兩只海豚執(zhí)行槍決。命令一下，這兩只海豚被拉到海面上，用繩子捆綁著不能游走，當(dāng)即被執(zhí)行槍決。,NMMP，訓(xùn)練海洋動(dòng)物作軍事用途，曾導(dǎo)致牠們?cè)趫?zhí)勤時(shí)死亡，而軍方也會(huì)把動(dòng)

36、物封嘴，以防它們饞嘴誤事，這些都一直被愛護(hù)動(dòng)物組織批評(píng)不人道。動(dòng)物會(huì)被派往偵測(cè)危險(xiǎn)性極高的水域。在波斯灣執(zhí)勤時(shí)，美軍派出六條海豚為軍艦護(hù)航，游過有毒的水域，其中一條因此死亡。海洋動(dòng)物退役后，有沒有獲得美軍的妥善照顧，也備受外界質(zhì)疑。美軍近日公布一項(xiàng)調(diào)查則證實(shí)，海軍訓(xùn)練海洋動(dòng)物時(shí)于海底發(fā)出的聲納，會(huì)影響其他海洋生物，每年導(dǎo)致200只生物死亡。 1976年，美國夏威夷島 發(fā)生了一起轟動(dòng)一時(shí)的案件：因?yàn)榉磳?duì)海豚進(jìn)行軍事訓(xùn)練，當(dāng)?shù)厮屦^的兩名工作人員將兩只海豚(Luther and Buck)放回大海，結(jié)果受到起訴。 1996年，Ric OBarry 將兩只退役海豚放回墨西哥灣，被捕回。,Miscel

37、laneous Pictures,海洋哺乳動(dòng)物面臨的威脅,海洋污染 過度捕撈 纏繞 其它,海洋污染,噪音 石油 化學(xué)污染物 垃圾 塑料之海,噪音污染,Many cetaceans, such as certain whales and dolphins, rely on sound for communication and locating food. They are adversely affected by human-made noise. Noise pollution can come from a wide variety of sources, with some of th

38、ose being ship traffic, seabed drilling, seismic surveys, sonars, oceanographical experiments, recreational activities, and underwater explosions.,噪音污染,低水平噪音會(huì)使鯨魚和海豚感到不適，迫使他們離開棲息地。長(zhǎng)期的壓力將對(duì)健康產(chǎn)生極大影響。 高水平的噪音如水下爆炸，會(huì)直接造成耳內(nèi)結(jié)構(gòu)的損傷。 聲吶作用受到噪音的影響。,石油污染,Oil is another type of pollution that negatively impacts mar

39、ine mammals. It is generally introduced into the environment through accidental spills. Oil is a compound that can destroy the insulating properties of a marine mammals skin.,石油污染,It is often the case that oil is unintentionally eaten during removal attempts. If ingested, the toxic oil can damage a

40、marine mammals organs, which could result in death. If inhaled, which is usually done by whales and dolphins coming up for air, the oil can cause pneumonia. Oil pollution can destroy the habitats of marine mammals, forcing them to travel elsewhere or perish.,化學(xué)污染,Chemical pollution is a type that ca

41、n contaminate the whole of a marine food web. In a contaminated environment, as smaller fish eat plankton, and the larger fish eat the smaller fish, the toxins that exist will greatly accumulate in the bodies of large fish. Since marine mammals are at the top of their food chain, the high levels of

42、chemical pollutants in their food will build up in their bodies, in areas such as fatty tissue and breast milk.,化學(xué)污染,Marine mammals suffer from the increasing concentrations of heavy metals, PCBs, dioxins, DDT, and other persistent organic pollutants that are dumped or leaked into the ocean. Due to

43、the bioaccumulation of chemical pollutants, marine mammals can suffer from a wide array of illnesses and disruptions to their normal body functions. Pesticides and industrial compounds usually have a negative impact on the endocrine, digestive, and nervous systems, which can lead to a decrease in he

44、alth, growth and development issues, a weakened immune system, and diminished reproductive abilities. Chemical pollutants can also cause cancer.,塑料和垃圾,Plastic and other debris in the ocean are a large threat to the wellbeing of marine mammals, especially due to the fact that they take a very long ti

45、me to break down. Studies suggest that over 60% of the debris in the sea is plastic.,塑料和垃圾,Plastic and other debris can easily trap and get tangled on various marine mammals. This can lead to numerous complications. Marine mammals sometimes mistake marine debris for food and accidentally ingest it.

46、This can cause a blocking of the digestive tract, choking, internal injuries, and an accumulation of toxic compounds. All of these implications can be fatal. It is estimated that this plastic sea is the cause of death for over 100,000 marine mammals every year,過度捕撈,什么是過度捕撈？ 對(duì)海洋哺乳動(dòng)物的負(fù)面影響。,過度捕撈,Overfi

47、shing is the act of fishing a body of water so extensively that it depletes the supply of fish in an area. It occurs when the quantity of fish harvested exceeds the amount that can be re-supplied by growth and reproduction, which results in a population collapse of the target species.,對(duì)海洋哺乳動(dòng)物的影響,Whe

48、n fishing, commercial fisheries often compete for the resource of fish with their natural predators. This can make it more difficult for a population of marine mammals to obtain food. Overfishing can also cause an imbalance in an aquatic ecosystem by removing one of the links in the food chain. This

49、 in turn can result in the decline or displacement of marine mammals which depended on the harvested fish as a food source.,纏 繞,What is Entanglement? 漁網(wǎng) 垃圾,纏 繞,Entanglement is a large threat to marine mammals. It occurs when they are accidentally trapped in fishing nets, fishing lines, or other snar

50、es. It is estimated that hundreds of thousands of marine mammals are entangled each year.,漁 網(wǎng),Drift nets are one of the most threatening types of nets used by fisheries. They are essentially nets made of thin strands of nylon that are left to freely drift and catch everything in their path. They can

51、 sometimes be miles long and be left unattended for weeks. Drift nets typically catch a large amount of bycatch, or the non-target species that become tangled in the nets, such as whales, dolphins, and seals.,漁 網(wǎng),Marine mammals that are trapped in these and other nets will often drown if they cannot

52、 escape. Those that do escape usually end up with scars or missing fins as a result of being cut by the thin nylon strands of the nets.,垃 圾,Debris, such as plastic rings and fishing lines, mainly pose a threat to pinnipeds, or walruses and seals. These marine mammals often become trapped with debris around their necks or heads, which can restrict breathing, eating, and even swimming. Debris can also inflict physical wounds. At the very least, these negative impacts will debilitate their target