Net Gain, Net Effect

Note that older students can buddy with younger ones to carry out this activity.

• To prepare the "ocean", mix all beans and grains. Divide the mixture into the four containers to represent four "fishing grounds."
• Ask students to decide what fish species each bean or grain will represent. Make a chart matching the beans or grains with the fish they represent.
• Discuss how fish are caught. If you fish, how do you catch them? Have you seen people catch fish, and how did they do it? What are some ways to catch lots of fish at one time? How did people use to catch fish, and how do they catch them today? Then tell students they will simulate net fishing.
• Divide students into four groups — one group for each fishing ground.
• Pass out nets cut to about 10 by 15 centimetres. One net for three students will work.
• Start with the coarse netting to represent commercial fishermen. Students may use only one hand. They must hold the net so the distance between their thumb and first finger forms the catching area. Ask them each to make one pass with their nets through the fishing grounds.
• Have students dump their "fish" on to a sheet of paper or "boat". Count the fish caught and record numbers. Next, allow students to use both hands. Make one pass through the "ocean". Have students count the fish again and repeat the process several times.
• Discuss results. Most likely, students will catch more fish with two hands. Compare this increase to an improvement in technology.
• Notice the species caught. The smaller lentils and rice will often slip through the netting. You can more easily catch the larger species (limas and pintos). Ask students how they could catch more fish, then discuss the options.
• Next, give them a net mesh of less than 5 millimetres, about 10 by 15 centimetres square. Return all fish to the ocean containers so students can fish with the smaller-meshed nets. Tabulate as before and discuss results.
• Return all fish to the ocean. (Note for teachers of younger students: the activity may end here with a discussion. Ask students to talk about what happens when they use different nets. Is it good to let the smaller fish through the net? Which nets might be better to use in order to conserve the oceans fish?)
• Try a different approach. Tell students that all the fish are the same species. Tell them they cannot catch any fish smaller than the black bean species. Any smaller fish will cost them a point. Explain that a government agency responsible for monitoring fishing will give them 10 seconds to get rid of oil undersized fish after each netting. Appoint two members of each fishing team to this agency.
• The commercial fishermen will again use the fine mesh net to make a catch. They have 10 seconds to empty the net on to the table and return any undersized fish to the ocean. The agency representatives will count the undersized fish left and fine the fishermen one point for each.
• (Optional: discuss the economies involved. Can those fishing afford to return all the undersized fish to the sea? What are their options?
• Repeat with a larger net mesh. Is there an advantage to letting the smaller fish get through the net rather than returning them by hand? Discuss how nets often catch dolphins and sea turtles. Point out that those species have the opposite problem — they are too large to escape. Note: people are using fishing equipment that reduces dolphin and sea turtle deaths.
• Review the history of fishing. Discuss how changes may have affected fish numbers and fish habitats. Conclude with discussion on how, if at all, students think we can develop fishing technologies that minimize long-term harm to fish and aquatic environments.