Sequence | Background | Objectives | Materials | Activity | Extensions | Evaluations

TOPIC-TITLE Marine & Aquatic Resources Activities - Understanding By-Catch AUTHOR Kathy Westerman GRADE SUITABILITY Middle School SCOPE Life Science

Sequence This activity should follow a unit on commercial and recreational fisheries in the United States. Concepts of maximum sustainable yield, by-catch, and reduction of by-catch should be introduced. Students need to be provided with background information on shrimp and sea turtles. Students should also be familiar with food webs and the concept of natural balance within an ecosystem. You may enhance this background information by showing students videos such as Magnificent Fish by the New England Aquarium. < < go top

Background Summary Many resources are derived from the sea, both living and nonliving. Examples of some nonliving resources are oil and gas. Examples of living resources include recreational fishing, commercial fishing/shrimping, and SCUBA diving. The oceans produce the largest amount of organic matter on Earth. Food from the sea, however, amounts to only 1 percent of the world's total food consumption. Even with the small percentage of consumption, finfish and shellfish provide 10 percent of the protein to the world's population. Consumption of seafood in the United States is dramatically increasing. Shrimping is the most economically viable fishery in the Gulf of Mexico. The type of shrimp harvested from these waters is the penaeid shrimp, which include white, brown, and pink species. Shrimping is such a rapidly growing industry that many fishermen use two trawl nets to increase their catches. These trawls must have a fairly small mesh size to capture these organisms. Because of the small mesh size, many other types of marine organisms, such as finfish and sharks, become trapped in these nets. Anything caught and perceived to be of no value to the fishermen is considered by-catch. This by-catch is merely removed from the nets and thrown into the water. Most of these by-catch species die because of the stress caused from the trawl. Often the amount of by-catch will be greater than the amount of shrimp caught. In fact, the ratio of by-catch to shrimp in the Gulf is 5.25:1. This can have an adverse effect on the populations of species being caught as by-catch. Another animal that is threatened by the shrimp fishery is the sea turtle. All eight species of sea turtles are currently endangered or threatened in the United States. In the Gulf of Mexico, the Kemp's Ridley sea turtle is severely affected by shrimping trawls. It is the most endangered of the sea turtles. The United States government recently passed regulations 97 percent effective. Some shrimpers complain they lose too much of their catch when using the TEDs. The TED law is difficult to enforce because the ocean is so vast and there are too few enforcement officers. Hopefully, the turtle populations will replenish with time. Research has recently been completed for the development of a By-catch Reduction Device (BRD). Many of our marine resources are being negatively impacted by shrimp trawls. The shrimping industry is important to the economy. However, adequate care must be taken to ensure the conservation and preservation of other resources taken during shrimping activities. < < go top Objectives Students will be able to do the following: Calculate the percentage of shrimp caught during the shrimp trawling. Calculate the percentage of by-catch caught during the shrimp trawling. Calculate the percentage of sea turtles caught during the shrimp trawling. Suggest several (at least three) ways in which the by-catch and turtle death rate may be reduced. < < go top Materials Each cooperative learning group of students will need the following: Paper bag containing a mixture of beans you have prepared (100 split peas, three lima beans, 500 pinto beans) Small aquarium net The 100 split pea beans represent the shrimp (desirable harvest). The three lima beans represent the sea turtles, and the 500 pinto beans represent the by-catch. < < go top Activity Have the students create hypotheses they believe will happen when they go "fishing." Obtain a paper bag with a mixture of beans from the teacher. Dip the aquarium net into the bag. Count and record the number of split pea beans (representing the shrimp). Count and record the number of lima beans (representing the turtles). Count and record the number of pinto beans (representing the by-catch). Determine the percentage of shrimp caught (# of shrimp divided by # of total beans) x 100. Determine the percentage of by-catch caught (# of by catch divided by # of total beans) x 100. Determine the percentage of turtles caught (# of turtles divided by # of total beans) x 100. < < go top Possible Extension Design your own turtle excluder device for "trawling." Design your own by-catch reduction device for "trawling." You can accomplish this activity with a different species of live fish representing the shrimp, turtles, and by-catch. < < go top Teacher Evaluation Students should be able to answer the following: Calculate the percentages of each type organism caught (shrimp, by-catch, and turtles). Make several (at least three) suggestions as to ways by-catch might be reduced. How might the turtle death rate be decreased? How do you think the by-catch and turtle deaths are affecting the rest of the marine ecosystem? < < go top