All Caught Up: Bycatching and Design

In the first lesson, Caught in the Net, students learn about bycatch—how commercial fishing nets trap large amounts of unintended and unprofitable animals while catching their target species. In the associated activity, All Caught Up, students learn about fishermen's challenge in trying to isolate a target species when a variety of animals are found in a marine habitat of interest. They discuss the large magnitude of the problem, practicing data acquisition and analysis skills by collecting and processing information to deduce target species distribution trends.

In the second lesson, Sound for Sight, the concept of echolocation is introduced as well as how dolphins use this sense to perceive environmental threats in their marine habitat, such as gillnets set by commercial fishing vessels. In the first associated activity, Can You Hear It?, students use marbles and a box made by the teacher to simulate echolocation and experience how much sound can tell us about an object. This helps to illustrate dolphins' use of echolocation, their difficulty in identifying nets, and resulting net entrapment. In the second associated activity, Your Ears Do the Walking, students play a modified game of "Marco polo" to understand the difficulty of using only the sense of sound to observe their environment. They experience an echolocation simulation by walking along a path while blindfolded. What students learn from these activities suggests the engineering approach of taking advantage of dolphins' echolocation ability in the design of bycatch avoidance methods.

Students study bycatch from an engineering perspective with the idea to design technological solutions to better address the problem. Many current devices and equipment designed by engineers, such as acoustic alarms, breakaway links, gear modification and time-area closures, are helpful but not enough to alleviate the problem. After learning how echolocation works, students discuss how net designs can be made easier for dolphins to "see" using echolocation and therefore less likely for dolphins become entangled.