Two Fish, One Fish, No Fish

So let’s say that you and your friends are at a tailgate where free food was being given out. The free food is being distributed at multiple locations, and you see that at one location, food is running low while there is still plenty to go around at the other locations. What do you do? Even with a couple of beers in you, it can be certain that you would make the nearly automatic decision to simply go to one of the locations that still had plenty of food. This notion parallels that of the bioeconomic theory, which assumes that fishing cannot lead to extinction because depleted fish populations would naturally deter any further fishing efforts. It’s all about the economics; if there’s no fish, there’s no money to be made, so why would fishers continue fishing in a place with no fish?

The answer? Because there ARE still fish, just not a lot. As long as there is still SOME food in that line, people will still line up to get food from that vendor until there is absolutely no food left. We sometimes forget that humans are inherently selfish and greedy, and we’re perpetrators of the tragedy of the commons. Even if we’re aware that a fish population is depleting, we think, “Well it won’t make too much of a difference if I catch a few more of these.” But one “I” turns into a lot of “I’s, and then we are left with zero fish. As much as we would like to trust ourselves with being able to assess population statuses and have enough self-control to take conservation into our own hands, stronger regulations and stricter enforcements of the rules are necessary to protect species from extinction.

In the article, “Understanding fishing-induced extinctions in the Amazon,” the study on the Arapaima fish populations in the Amazon Basin disproved the bioeconomic theory and supported the counter that fishing-induced extinctions can indeed occur and is occurring as you are reading this essay. A model that was discussed in the study called “fishing-down” explains that the body size of fish species determines the extinction risk when it comes to fishing. The model predicts that large-bodied species have more vulnerable traits (such as late maturity, behavior that increases catchability, etc.) and are thus the more targeted species and are the ones to deplete and go extinct first. However, smaller-bodied fish species still remain and are thus available to be fished. Essentially, in the fishing-down theory, fishing continues after a population has been depleted, whereas in the bioeconomic theory, fishing does not continue after a population has been depleted, or at least that is what is assumed.

The studies on the Arapaima species revealed that fisheries in Brazil did have minimum size and closed season regulations in place for the harvesting of the fish, however poor enforcement and low compliance of those regulations proved them to be ineffective. Also, since the Arapaima species is a non-migratory fish, it is easily targeted by commercial schemes due the fish’s ease of catchability. Without any quantitative evidence, these two observations alone should be enough to disprove the argument that fishing has nothing to do with the depletion or extinction of fish. Not unsurprisingly, results of the study did in fact show that the Arapaima populations were “depleted” in 76% of the fishing communities, “overexploited” in 17%, “overmanaged” in 5%, and “unfished” in only 2% (Castello, 452).

"110lb Arapaima" by Andrew Hosegood is licensed under CC 2.0

110lb Arapaima” by Andrew Hosegood is licensed under CC 2.0

Despite fishers themselves reporting that Arapaima abundance has declined in recent years, an average of 23% of fishers in each fishing community continued to fish this species of fish regardless of their population status. The Arapaima population was defined as “depleted” in 76% of the fishing communities and “locally extinct” in 19%, yet they were still being harvested. These results directly refute the bioeconomic theory while supporting the fishing-down model that fishing still persists even when the fish population has depleted or is in danger of depletion. The reason for the decline and near-extinction? Unsustainable fishing practices…facilitated by the lack of regulations and enforcement.

The solution that the study proposes to this fishing-down problem is to introduce “management policies that are multi-pronged to address issues related not only to size and season of target species but also to gear and poverty” (455). Implementing size and season regulations were something that the study had addressed early on in its identification of the problem, but addressing poverty of the fishers themselves is an interesting concept, though more difficult to achieve. Humans are selfish, sure, but it’s normally for good intentions, like to make sure one’s own children won’t go to bed hungry. In some cases, local communities can form collaborative efforts to protect a species from further depletion, like in the case of the sage-grouse, but in most cases, it is unlikely that economic and nutrition value of these resources can be controlled without stricter regulations and policy enforcement. You want tailgaters to stop lining up for food that’s running out? Rope off the area and put a sign up that says CLOSED FOR SERVICE.


Castello, L., C. C. Arantes, D. G. McGrath, D. J. Stewart, and F. S. De Sousa, 2015. Understanding fishing-induced extinctions in the Amazon. Aquatic Conserv.: Mar. Freshw. Ecosyst. 25: 447-458.

This entry was posted in Conservation Biology Posts, Conservation Editorials 2015. Bookmark the permalink.

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