為什麼吃魚翅可能不是一個好主意 / Why it might not be a good idea to consume shark fins soup

在我之前的帖與Biuiam 行博物館
我向你們展示香港海事博物館所舉辦的鯊魚與人類展覽。這次展覽是為了引起我們對鯊魚的保育關注，因為鯊魚的濫捕使其魚量大幅度下降。

鯊魚有相對較長的繁殖週期，意味著在達到性成熟之前需要很長時間。因此，使鯊魚捕魚成為鯊魚數目的重大問題。不同的地方都有把鯊魚作為其美食的一部分，但涉及製作魚翅的中菜則對鯊魚過度捕撈的帶來主要驅動力。魚翅被認為是一種豪華菜餚，這進一步推動了將鯊魚鰭變成鯊魚最有價值的一部分 。因此，鯊魚被捕獲，魚鰭被切除，魚身隨後被釋放回大海，因為鯊魚的肉類和其他部分的價值遠低於其魚鰭。

這種獵殺鯊魚方法不僅是不人道的，而且也危及了生態金字塔。在生態金字塔中，它基本上是每個營養級別的生物量代表，主要生產者如浮游植物和藻類在太陽光的幫助下生產生物質（太陽光通常是驅動生態系統的能源），那些浮游植物和藻類依次被浮游動物或小魚等大型生物體所吃掉, 小魚再被海豚吃掉 海豚又再被鯨魚吃掉←只是開玩笑，大魚被鯊魚吃掉。對於捕食者和獵物關係的每一個進展，能量都會丟失，因此為了支持大量的鯊魚，需要大量的大型魚類，而且需要大量的小型魚群來支持大魚，這就解釋了為什麼對於所有的生態系統來說，初級生產者總是在環境中最豐富的。

考慮到生態金字塔，這就解釋了為什麼當我們獵殺鯊魚時，它對生態系統造成更大的傷害。如果漁民在每次釣魚行程中要收穫整個鯊魚，他們將迅速達到他們的載重極限。鯊魚鰭約佔整個鯊魚體重的1.4％左右。因此，通過只把鯊魚鰭留下，他們可以殺死更多的鯊魚。這種殺死較高層的捕食者(鯊魚)會導致較低級的捕食者(大魚類)失去人口控制。這將導致對較小的魚的被大量捕獵。生態系統中的整個食物鏈將通過消除較高階層捕食者等重要群體而受到影響。

生態金字塔也解釋了為什麼據報導，對我們來說，吃魚翅有潛在的風險。這是食物鏈中有害/有毒物質生物放大效應的結果。來自不同來源的汞或其他重金屬可以通過浮游生物進入食物鏈。重金屬和一些毒素一旦進入生物的體內就很難被去除。因為小魚會長大，所以過程中會吃掉大量的浮游生物，再之後來被更大的魚吃掉。在每個捕食者和獵物相互作用期間，越來越多的下層生物將被吃掉，因此在較高的捕食者中有越來越多的重金屬或有毒物質的積累。鯊魚是頂級捕食者將含有高濃度的這些有害物質。在鯊魚鰭中可以檢測到高汞濃度以及可能與阿爾茨海默病相關的神經毒素中。

所以下次吃魚翅時想一想.

沒有買賣,就沒有殺害

In my previous post Museum with Biuiam I showed you guys around the Hong Kong Maritime Museum on the exhibition of Sharks and Humanity. That exhibition was to arouse our focus on sharks conservations, as over fishing for sharks has caused a drastic drop.

Sharks have relatively long reproductive cycles, meaning they require a long period of time before reaching sexual maturity. Therefore making over fishing of sharks a significant problem to the sharks population. Different place consumes sharks as part of their cuisines but the Chinese cuisines involving the making of shark fins soup is held responsible for major driving force for sharks over-fishing. This is further driven by the fact that the shark fin soup is considered as a luxury dish, turning the shark fins into the most valuable part of the shark. Thus, sharks are captured, with fins removed and later released back to the sea, as the meat and other parts of the sharks holds much less significant value.

This shark finning practice is not only inhumane but also dangerous in terms of ecological pyramid/ trophic pyramid. In an ecological pyramid, it is basically a representation of biomass at each trophic level, primary producers like phytoplanktons and algaes produce biomass with the help of sun light (sun light is usually the energy source driving the ecosystem), those phytoplanktons and alages in turn gets consumed by large organisms like zooplanktons or small fish, then minnows get consumed by dolphins and dolphins get consumed by whales ← just kidding, and larger fish get eaten by sharks. For each progression of the predator and prey relationship, energy are lost, that’s why in order to support a large population of sharks, a larger population of large fish are required, and a much larger population of small fish are needed to support the population of large fish, this explains why for all ecosystems, primary producers are always the most abundant players in the environment.

Having that ecological pyramid in mind, this explains why when we are finning sharks it is dealing much more damage to the ecosystem. If fisherman were to harvest the whole sharks during each fishing trip, they will be reaching their carrying limit rapidly. Shark fins occupies roughly around 1.4% of the whole shark’s body mass. Thus by shark finning, much more sharks could be killed. This over killing of the higher predator sharks lead to less predators to control the large fish population. This will lead to the over hunting of the smaller fish. The whole food chain in the ecosystem will be affected by removing a significant population of a higher hierarchy predator.

The ecological pyramid also explained why it is being reported that it is potentially dangerous for us to consumer shark fin soup. This is the result of the biomagnification of harmful/ toxic substances in the food chain. Mercury or other heavy metal from different source can easily enter the food chains via planktons. Heavy metals and some toxins are difficult to be removed once they enter an organism’s body. As small fishes will consume a lot of planktons as they grow up, which later get eaten by larger fishes. During each predator and prey interactions, more and more of the lower level organisms will be eaten, thus there are more and more accumulation of the heavy metal or toxic substance in the higher predators. Sharks being top predators will contain high concentration of those harmful substances. High mercury concentrations were detected in shark fins as well as neurotoxins that could link to Alzheimer’s and Lou Gehrig Disease.

So next time when you eat shark fin soup, please keep in mind.

When the buying stops the killing can too

Ref:
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3297012/
https://www.sciencedaily.com/releases/2012/02/120223182516.htm
http://www.wwf.org.hk/en/whatwedo/oceans/saying_no_to_shark_fin/
https://en.wikipedia.org/wiki/Shark
https://zh.wikipedia.org/zh-hk/%E7%94%9F%E6%85%8B%E5%A1%94
https://www.theguardian.com/science/blog/2016/mar/10/shark-fin-soup-a-dangerous-delicacy-for-humans-and-sharks-alike

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