Maintaining Strong Fisheries
Click here to download & print the Blue Crab Gameboard and Fact Sheet in Adobe Acrobat format.*

• To learn the environmental threats to a species
• To understand the need for regulation of fishing and protection of the organism’s habitat
• To identify the different points of view of fishers and resource managers

Vocabulary

• carrying capacity

Background

Sophisticated technology has made it possible to use satellite imagery to find and capture fish, to use lines and nets that are miles long, and to stay out in the open sea for months at a time. But will the ability to catch more fish now mean that there will be less fish to catch later? In 1989, the amount of fish caught worldwide was greater than it had ever been. Since then, the global fish catch has declined.

No population of fish can increase indefinitely, but a fish population will grow until limited by its environment. The major influences on population growth for animals are competition for food, presence of predators, and availability of suitable habitat. The size of the population will remain the same when the birth rate (number of births in a given time period) equals the death rate (number of deaths in a given period). This is called the carrying capacity of a population.

Fish and shellfish must have an adequate food supply, shelter for breeding, protection from predators, a livable water temperature, and appropriate salinity to survive. Many fish and shellfish produce a large number of eggs to assure that some of the eggs will become adults. Only when the female fish or shellfish reaches the adult stage can she reproduce. Natural predators as well as man-made problems like the destruction of habitat limit the numbers of eggs that complete the life cycle. Harvesting juveniles and females may allow fisherman to catch more fish today, but will certainly limit the numbers of fish available to be caught in the future.

For a fisher, these changes in fish population lead to an unstable livelihood. Ecological events, such as El Niņo, can cause fish populations to change. Political events, such as a new president appointing new directors of the government agencies, can lead to changes in fishing regulations.

Fishermen need a source of income year round, though the fishing season for most species is only for part of the year. Usually they can compensate by fishing for more than one species. Fishermen have to think of both their short-term and long-term needs. In the long term, fishers want to be able to rely on fishing as a source of income. In the short term, they need to be able to earn enough money to survive.

Resource managers are the people in the middle. They are trying to keep the fish populations healthy enough to assure that the fishers will be able to continue fishing generation after generation. Managers use many kinds of regulations to control the exploitation of the fishery. There might be restrictions on the type of gear fishers can use, the number of boats allowed out on the water, and the size of the fish caught. There may be seasons when fishers cannot harvest a species, an area where they cannot fish, and catch quotas which limit the number of fish that can be caught each day. Managers can try to decrease the number of people fishing by taxing gas, oil or the fish they catch. They can give a group of people exclusive rights to one species of fishing or one area, thus keeping all others out.

Materials

• different kinds of paper clips or other place markers (one for each student)
• coin
• Blue Crab Gameboard (download*)
• Blue Crab Fact Sheet (download*)

Preparation

1. Make a copy of the Blue Crab Fact Sheets for each student.

Activity

1. Ask students what organisms need to maintain a stable population.
2. Distribute the Blue Crab Fact Sheets to students. Have students read information silently. Ask students what the blue crabs need to survive. Make a list under the title "needs." Ask students what threatens the blue crabs. Make a another list, under the title "threats."
3. Explain to students that they will be playing a game where they will go through the life cycle of the blue crab by moving their marker around the gameboard. Tell students that they will flip the coin to see how to advance from the block labeled Start. Heads is one square; tails is two squares. They will start out with 500 blue crab eggs and the goal is to get to the block labeled Adult/Finish.
4. After the game is over, ask students: What causes changes in the crab population? What could a resource manager do to keep a stable crab population? To increase the crab population?
5. Have students create a game entitled "The Life of a Fisherman." You may want to share the information in the Background with the students to help them get started. For example, blocks on the gameboard could read "New Net Works—Caught 50 Fish;" "Fishing Season Ends—Lose One Turn;" or "Fish Quota Increases—Caught 10 More Fish." After creating the game, students can make a gameboard and play the game. At the end of the game, the students can compare how many fish each player caught.

Extend the Activity

Have students create another game based on the life cycle of another marine animal of Magdalena Bay.

* If you do not have Adobe Acrobat reader, download it for free from www.adobe.com