By: Jasmine Chan
Famous economist, Jean Baptiste de Lamarck and Thomas Huxley, began an optimistic and misled bioeconomics theory of marine populations being impenetrable that has persisted to this day and influenced policy makers.1 Their idea that human exploitation could never cause the extinction of marine species was founded on a few ideas. Under the idea that marine animals have such wide distributions in such vast water bodies, Lamarck and Huxley thought that the populations were too large to be at risk. Bioeconomic theory added on the thought that once a species becomes depleted it will become too expensive to fish for this species and fishers will move on to different, easier catches. How is it then that 55% of 133 documented local, regional, and global extinctions of marine populations can be attributed to fishing? And now, with the misled fisheries allowed to continue their reckless practices, one of the largest and most iconic fish of the Amazon, the arapaima, is facing extinction.
The arapaima is an extremely unique and iconic fish of the Amazon basin and nearby lakes that has important significance to the ecosystem and to the native populations. The arapaima is an amazing mega fish that can grow to lengths of 9 feet and weights of up to 440 pounds.2 The arapaima is also a resource of indigenous Amazonian communities that use it as a food source and even use the large scales as jewelry. As an air breathing fish, the arapaima spends most of its time near the surface to breathe and hunt as a predatory species. All of these things that make the arapaima so interesting and unique also make it a huge target for fishermen.
In a recent study conducted by Leondro Castello of the Virginia Polytechnic Institute and State University and colleagues, researches sought to disprove the notion of economic pressures preventing overfishing of depleted species through use of the arapaima species. The study brings to light an opposing theory, the “fishing down” theory. This theory describes how larger body size is a risk factor for extinction. Castello’s paper goes on to say that “large-bodied animals tend to be more sought-after and possess life-history traits associated with vulnerability, including late maturity, low intrinsic rates of population increase, behavior that increases catchability and dependence on vulnerable habitats.” The idea is that the easy hunting of large fish will put a pressure on the population that pushes the average size down. The smaller fish are then caught easily in nondiscriminatory nets. The arapaima species fits these criteria and thus was an important candidate for this study that aims to end the misinformation of the original bioeconomic theory of overfishing.
The results were not surprising, the arapaima fish is in great danger in the Amazonian basin. Fishing-down predictions were supported and confirmed. Through all the fishing communities studied, the arapaima populations were ‘depleted’ in 76%, ‘overexploited’ in 17%, ‘well-managed’ in 5%, and unfished in 2%. Almost 1/5 of communities surveyed had fished the arapaima to local extinction. The amazing arapaima fish is in grave danger due to these unsustainable fishing practices.
However, there is hope found in this study. In the communities where the fishermen were actually compliant to their local restrictions on arapaima harvests, the species was healthy in abundance and diversity.
This study proves that overfishing is a real threat to marine species. While the bioeconomic theory makes logical sense, in the context of biology, a species is not as stagnant and straight forward as Lamarck and Huxley see it and extinction is actually a real threat because of fishing down theory. This phenomenon of the fishing down theory is not just occurring in the Amazon river, but has also been recorded in west Africa leading to the disappearance of four more species.3 Bioeconomic theory cannot be accepted anymore in the light of the new fishing down theory and steps must be taken globally to manage fishing practices to protects beautiful and ecologically important species such as the arapaima from disappearing.
- Roberts, Callum M., and Julie P. Hawkins. “Extinction Risk in the Sea.”Trends in Ecology and Evolution 14.6 (1999): 241-46. ScieneDirect. Cell Press. Web. 22 Oct. 2015.
2. “Arapaimas, Arapaima Pictures, Arapaima Facts – National Geographic.”National Geographic. N.p., n.d. Web. 22 Oct. 2015.
3. Castello, Leandro, Caroline Chaves Arantes, David Gibbs Mcgrath, Donald James Stewart, and Fabio Sarmento De Sousa. “Understanding Fishing-induced Extinctions in the Amazon.” Aquatic Conserv: Mar. Freshw. Ecosyst. Aquatic Conservation: Marine and Freshwater Ecosystems 25.5 (2014): 447-58. Web.