By: Chenyang Wu

Coined by Daniel Pauly and other marine scientists, the phenomenon that describes the way fisheries are changing the aquatic ecosystem is called fishing down the web, a loop in which, by selectively fishing for larger fishes, the fishing industry has dramatically depleted the amount available to them, forcing them to approach smaller and smaller fish to generate profit. These larger types of fish are often found at the highest trophic levels in the ecosystem, meaning that they are mainly carnivorous and require the most energy to maintain, giving them their size. Because of their size, it is harder for them to escape from fishing techniques such as trawler nets, and they are valued at higher prices, making them primary targets for fishermen and fishing vessels. Furthermore, their high energy consumption and higher age of fertility means that they aren’t able to produce enough offspring to compensate for the damage fishing can do to their population. As the fish from these trophic levels eventually become overfished and harder to find, the industry looks towards their prey: the fish in the trophic level below them. This leads to the vicious cycle of fishing down the web, a loop that forces industries to turn to lower and lower trophic levels of marine organisms as their population in higher trophic levels becomes unsustainable. 

We can look at trends happening worldwide that point to our overfishing of these higher trophic level fish; in the Pacific Northwest, several species of salmon are facing extinction due to higher water temperatures and overfishing. In Japan, the price of the freshwater Japanese Eel multiplied as it became classified as endangered in 2014 and saw lower domestic catch rates. Sharks have become “functionally extinct” from 19% of the world’s coral reefs as the demand for shark fin soup, a delicacy in Asian countries, has increased. Sardines, one of species of fish found in lower trophic levels, have seen an increase in demand as larger fish have become less affordable and harder to catch.

Within each trophic level itself, it’s not just the population of fishes that are decreasing; their bodies are shrinking in size as well. This makes sense; smaller fish are more likely to escape from objects such as trawler nets and thus reproduce more, leading to future generations being more likely to inherit the parts of their genetic makeup that code for their smaller size. Furthermore, global warming has led to increases in ocean temperatures, lowering the oxygen-absorbing capabilities of water and increasing the need for oxygen in fishes, stunting their growth. This growth in ocean temperatures has also directly altered the metabolism of fishes, increasing their mortality rate. UC Berkeley provides just a few examples of the most dramatic changes in fish sizes across the world. We have been changing the makeup of our environment not just on an ecological level, but on a genetic and molecular level. Through our anthropogenic impact, we have been artificially selecting for smaller fish through our fishing techniques and our contribution to climate change.

So, how can we prevent a future where jellyfish and plankton become the only creatures that roam our seas? Many problems such as our generally apathetic views on fish welfare leading to subsequent lack of action and our negative effect on the environment are factors that impact the sustainability of our oceans. Considering this article’s focus on the effect of the fishing industry, I would like to focus on informing others of key aspects that surround the issue of overfishing and how they can be resolved. Poor oversight by fisheries and lack of regulation surrounding fishermen is a major factor; establishing fishing rights could help control the amount of catches per day through enforcing a daily cap and designating specific areas to separate fishermen to reduce competition, resolving any “tragedy of the commons'' situations that might take place. The idea of implementing a Maximum Sustainable Yield (MSY), introduced in the 2002 World Summit of Sustainable Development, promotes efficient fishing practices that also minimize population loss through leaving a select amount of fish untouched so they can repopulate and sustain their population. Though this is a solution that seeks to both benefit fishermen and reduce harm to the environment, its implementation has been a rocky road due to poor regulations in the industry. Being informed of the issues surrounding fisheries and their environmental impact will help us find a place where we can start to take action, whether it be social media or a community-led campaign. For our oceans to prosper as they have before, we must make use of our time now to prevent its collapse and protect the bounties it has given us. 

Chenyang Wu is an undergraduate biology major based in New York City and a writer for the Factory Farm Awareness Coalition