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  • Triple Helix

The Door is this Way, My Good Fish: Traps, Escape Gaps, and Sustainable Fishing

Written by Tom Gotsch ‘26

Edited by Josephine Chen ‘24

For many people, the idea of fish traps may conjure the image of lobsters. These 3-dimensional devices are constructed of wire, mesh, and rope, and lowered to the seafloor with bait to lure sea creatures inside and prevent them from escaping (NOAA). Fish traps are especially popular in coral reefs and surrounding shallow areas because of the high concentration of sealife. (NOAA). As a key tool for fishers’ revenues, fish traps have been used prominently in coasts around the world, but as the amount of fishing increases to feed the growing population and to make higher profits, these traps are damaging coastal marine ecosystems (NOAA).

The problem lies in the trap design itself. According to Ayana Elizabeth Johnson, marine biologist and co-founder of the nonprofit organization Urban Ocean Lab, while fish traps are highly effective at capturing the desired high-value fish, they’re also capturing fish that are unpopular in the markets but ecologically important to the region (Johnson, 2010). This “bycatch” is highly destructive. Around the world, population declines of ecologically important species due to bycatch have impacted the entire ecosystem, ranging from endangered seabirds to sea turtles to large marine mammals, such as whales (Lewison & Crowder, 2003; Lewison et al., 2004). Simplified, the decline in the population of important prey species leads to less food for predators, making it difficult for them to survive. Such crucial effects continue to accumulate throughout a community, shaking the structure of the entire ecosystem (Lewison & Crowder, 2003).

So what can be done? Thankfully, there’s an easy, efficient, and cost-effective solution: cut some holes—well, the right ones, at least.

In 2010, Johnson studied different fish trap designs and their impacts on the populations of ecologically important species on the reefs of the Caribbean island of Curaçao. Specifically, she analyzed “escape gaps:” small, vertical, rectangular holes cut in particular spots on the trap to control which fish get trapped (Johnson, 2010). These holes were placed in opposing corners in the traps, enabling smaller, narrower, juvenile, and often herbivorous fish, which are important as foundational members of ecosystems, to escape, but trapping larger and more meaty fish that fishers could be sold (Johnson, 2010). Overall, these traps with escape gaps caught ~77% fewer bycatch fish, ~50% fewer key herbivores, and more than 90% fewer butterflyfish, which are ecologically important fish in the region (Johnson, 2010). The number of high-value fish caught by the traps did not change, and the cost of trap modifications was extremely low (Johnson, 2010).

Escape gaps are a key method that fishers can implement in their traps to increase the sustainability of their fishing methods while maintaining their revenues. These sustainable fish trap practices are already being implemented on a larger scale. Today, fish traps are required to have escape gaps in Curaçao, and more places around the world, like certain parts of Kenya, Tanzania, and Zanzibar, are adopting similar mandates (National Geographic, Johnson). In the quest for more sustainable fishing, escape gaps are one small but crucial tool that can lead us there.



[1] Fishing gear: Traps and pots [Internet]. NOAA Fisheries. NOAA; 2019 [cited 2022Nov27]. Available from:

[2] Johnson A. Reducing bycatch in coral reef trap fisheries: escape gaps as a step towards sustainability. Mar Ecol Prog Ser. 2010 Sep 29;415:201–9.

[3] Johnson A. Solution: Escape Gaps for Fish Traps [Internet]. Ayana Elizabeth Johnson. National Geographic; 2013 [cited 2022Nov27]. Available from:

[4] Lewison R, Crowder L. ESTIMATING FISHERY BYCATCH AND EFFECTS ON A VULNERABLE SEABIRD POPULATION. Ecological Applications. 2003 Jun;13(3):743–53.

[5] Lewison R, Crowder L, Read A, Freeman S. Understanding impacts of fisheries bycatch on marine megafauna. Trends in Ecology & Evolution. 2004 Nov;19(11):598–604.

[6] Schull J, Hill R. Building a better fish trap : Scientists and U.S. Virgin Islands fishers partner to improve fish trap design [Internet]. NOAA Coral Reef Conservation Program (CRCP) Home Page. NOAA; 2016 [cited 2022Nov27]. Available from:

[IMAGE] Johnson AE. Solution: Escape Gaps for Fish Traps [Internet]. Ayana Elizabeth Johnson. National Geographic; 2013 [cited 2022Nov27]. Available from:

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