海洋生物链

20 years ago, Christensen designed a computer tool called Ecopath to study complex marine ecosystems. Now Ecopath has 6,000 users in 155 countries.

Christensen used 200 marine models from the Ecopath database for the analysis released at the Washington meeting. "We are estimating that the predatory fish, the large fish that eat other fish, have declined by 2/3 in the last 100 years and the decrease is accelerating. In the last 40 years alone, 54% of that decline is estimated to occur."

Over the same 100-year period, prey fish like anchovies, herring and sardines have more than doubled. "We've never had numbers of that before. We expected that might be the case. Now we have numbers documenting it. What has happened here is really we changed the wild ocean. We removed the big fish."

20年前，克里斯滕森设计了一个叫做“生态轨迹”的电脑程序来研究奥妙无穷的海底生态系统。如今,世界上155个国家在使用“生态轨迹”，全球用户已经达到6,000人。

在华盛顿会议上发表的分析报告里，克里斯滕森利用了“生态轨迹”数据库中的200个海洋生物模型。“我们估计掠食性鱼类——也就是那些会捕食其他鱼类的大鱼——它们的数量已经在过去的一个世纪内减少了三分之二，并且还在加速减少。据估计，其中有54%是在过去的这区区40年中消失的。”

同在这一百年内，像凤尾鱼、鲱鱼以及沙丁鱼这样小鱼的数目却翻了一倍不止。“这些小鱼的数量从未达到过如此之多的地步，但是由于这些大鱼数量的急剧减少，这种剧增也是在所难免。我们现在有在不断记录这些数目。其实事实上是我们改变了整个海域，我们把大鱼都消灭了。”

More prey and fewer predators could throw the ecosystem out of balance, Christensen says. That could promote the growth of algal blooms which deplete oxygen in the water column. Christensen fears that marine animals and plants would then begin dying off in huge numbers.

"If we look ahead we are going to see less stable ecosystems in the oceans. There would be forage fish, there would be very few of the organisms that let us control the ecosystem. We need the predators to keep the populations healthy of all the prey fish. And it will continue unless we change the way we manage the oceans."

What's driving these trends? Jacqueline Alder, coordinator of the Marine and Coastal Ecosystem Branch of the United Nations Environment Program, believes it's overfishing and pollution, complicated by global climate change. She says the future health of the ocean depends on fishing less, reducing wasteful bycatch, and taking action on multiple threats to marine ecosystems.

克里斯坦森说道，猎物数量激增而掠食动物不足会导致生态系统失衡。这会促进藻花繁生继而耗尽水体中的氧气。克里斯坦森担心海洋生物及植物会因此大规模相继死亡。

“我们预计，将来的海洋生态系统将变得脆弱不稳，饲料鱼居多，能够控制生态系统的生物少之又少。我们需要猎食动物来保持鱼群数量的健康。在我们改变我们驾驭海洋的方式之前，

这种海洋生态恶化的现象还将持续。”

究竟是什么在推动这一趋势？联合国环境署海洋与海岸生态部协调员杰奎琳·亚尔德认为原因在于过度捕捞及海洋污染，而全球气候变化使得一切雪上加霜。她说要让海洋有一个健康的未来，人类应减少海洋捕捞和误捕渔获物的浪费，以及对影响海洋生态的种种威胁采取行动。

"We need to think about expanding our marine protected area systems and also better management of those systems. We are reducing pollution, reducing the amount of pollutants coming in, including things like agricultural runoff. We'll also have to think about restoring some of our habitats like mangroves and coral reefs. And therefore, their nursery habitats will be able to have fish that will grow up into adults that will be available for the fishing community in 2050."

Fish now provide more than 3,000,000,000 people with at least 15% of their animal protein diet. According to the U.N. Food and Agriculture Organization, fish farms are set to overtake wild ocean catch as a primary source of food fish. Villy Christensen says the aquaculture industry currently relies on a variety of prey fish to feed its farm-raised species and that practice is not conducive to a healthy ocean. "So I woud say instead of fishing down the food web we have to eat chew the food web. We need to eat the sardines and anchovies."

Suggesting that by changing our eating habits - eating more prey than predators - we could help restore a more healthy balance to the ocean ecosystem.

“我们需要好好考虑扩大海洋保护区的制度，以及更好地管理这些制度。我们减少污染，减少污染物的排放量，包括诸如农业污染的排放。我们同时也需要考虑修复我们的一些居住地，诸如红树林和珊瑚礁。这样一来，它们就可以成为鱼苗生长的温床，到2050年的时候，就能长成鱼群了。”

鱼类为三十多亿人的饮食提供了至少百分之十五的动物蛋白质。据联合国粮食和农业组织透露，设立养鱼场的目的是为了超过野生捕鱼数量而成为食用鱼的主要来源。威利?克里斯滕森称，水产养殖业通常是用各种各样的饵料鱼来喂养鱼场饲养的品种，而这种方式不利于海洋健康。“我们需要的是沙丁鱼和凤尾鱼，而不是要破坏食物链。”

建议人们改变饮食习惯—少吃捕食性鱼类、多吃饵料性鱼类，我们可以帮助重建一个更平衡的海洋生态系统。