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II. Oyster Harvest Simulation

Summary

This activity explores the historical and technological changes in the 

harvest of oysters through the years. It encourages students to 

think about how humans have affected the Bay and the Eastern 

oyster. During the game, dried beans represent oysters, and 

students test out four different types of oyster harvesting tools; 

nippers, hand tongs, skipjack dredges, and power dredges. After 

each round of “harvest”, students observe and discuss how the 

structure of the reef has changed, and how the physical changes 

affect oysters and future populations.

Learning Objectives

Students will be able to:

• Explain three methods of oyster harvest and how each 

method can impact oyster populations and oyster reef 

structure. 

• Explain how a change in reef structure affect oyster 

populations. 

K-12 Oysters in the Chesapeake Bay

Module 2

Grade Level: Middle 

School 

Teaching Time – 1-2 class 

periods

Materials:

• Student Data sheets 1 and 2

• Cookie sheet or watershed 

map

• 1 bag of dry white beans

• 1 bag of dry black beans

• Several pairs of chopsticks

• Several plastic spoons

• Several pairs of salad tongs 

(the kind that is connected 

with a pivoting pin in the 

middle)

• Small measuring cups of 

equal size
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Background Information

At one time, oysters were so abundant in the Chesapeake Bay that their reefs defined the major 

river channels. The reefs extended to near the water surface; to stray out of the center channel 

often posed a navigational hazard to ships sailing up the Bay. The oyster population in the Bay is 

less than 1% of what it once was. This activity will investigate one factor in the oyster population 

decline in the last 130 years, harvesting methods.

Key Words

Nippers – small tong for spotting and plucking one 

oyster. 

Hand tongs – two-handled, double-headed tool that 

can reach down into the water and gather a group 

of oysters.

Dredges – hand or powered tool that is dragged 

across the seabed to scoop up large quantities of 

oysters.

Skipjack – wooden sailing vessel used for more than 100 years to dredge oysters from the 

Chesapeake Bay.

MSX – Oyster disease caused by a single-celled protozoan parasite, Naplosporidium nelsoni. Not 

harmful to humans but affects oyster populations. 

Dermo – Oyster disease caused by a single-celled protozoan parasite, Perkinsus marinus found in 

the Chesapeake Bay since 1949. It affects the blood cells of the oyster but is not harmful to humans. 

Activity Procedure

Adapted from Annapolis Maritime Museum Education Materials (amaritime.org)

Engagement

Show the Maryland Oyster Harvest graph and ask students to generate ideas about the population 

numbers represented in the graph. (These ideas will be revisited in later activities.)

Answer:

1. What do you think the annual oyster harvest was was before 1880? Higher than 7 million 

bushels. Even now we do not have a good handle on the actual oyster population and the 

number of oysters harvested is our best way to judge the size of the population.
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2. What potential reasons have caused the downward trend on oysters on the Chesapeake?

Answers will vary...Increased harvest, disease, pollution, predators

3. What historical event might have caused a slight rise in the oyster population in the 1940’s?

World War II because there were fewer people available to harvest. 

4. What do you think the future trend will show? Answers will vary

Exploration 

1. Students will use Data Sheet 1 to record their data. Use a large cookie sheet or flat surface, or a 

map of the Chesapeake Bay watershed for a better connection, and have the students make a 

mountain of dry beans on the surface to represent an oyster reef. Make sure that most of the beans 

are white, with a small proportion black. A sample table is provided to collect student data for 4 

rounds (years) of harvesting. 

2. In round 1, the students use chopsticks to pick up the beans/harvest the oysters, the chopsticks 

acting like nippers. Only give the students 10 seconds, to represent the oyster season in the winter. 

Discuss how Native Americans used nippers to harvest oysters, and have them record their results 

on Student Data Sheet 1 along with how this method has affected the shape and size of the bean 

mountain/oyster reef on the cookie sheet. Repeat for four “years” of harvest.

3. In round 2, students use a salad tongs to represent hand tongs. Collect data and note change in 

the shape of the underwater oyster mountain. 

4. In round 3, students use spoons to represent skipjacks with hand dredges and how the 

technology of oyster harvest had advanced. Students should record changes in the the shape of the 

underwater mountain due to the use of this new technology.

5. In the 4th and final round, students harvest oysters using small measuring cups to represent 

power dredges and power engines that boats now have. Only allow 7 seconds instead of 10 because 

the oyster population has declined and regulations are tougher. Students should record changes in 

the shape of the underwater mountain resulting from the use of this new technology.

6. Throughout all of the rounds, if any oysters spill off the map, stop the round and have the 

students put them back on the pile. These beans represent oysters that were too small to take (less 

than the 3-inch legal size).

7. At the end of the activity, when the students’ catch is much larger from power dredging than 

from hand tongs, tell them that the white beans are live oysters and the black ones are dead 

because diseases like MSX and Dermo, which have severely affected the oyster populations.
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Explanation 

Students will be using their knowledge of organizing and analyzing data to help come up with some 

conclusions on the data they have collected. This may involve learning how to use Excel to graph the 

data in the appropriate form. They will also have to interpret the data correctly in order to answer 

the discussion questions.

Step 1: Introduce students to the functions in Microsoft Excel that they will need to use throughout 

the project.

• They will have to be able to enter data into the correct cells.

• They will have to be able to highlight the correct cells and use Excel to create 

graphical representations of this data.

• Students will have to understand how to use a “drop down menu” in Excel.

Step 2: Give students some sample data to practice developing an Excel Document. Then have them 

put their own data into a document. 

Step 4: Students should explain their analysis of the sample data by completing the follow-up 

questions in Data Sheet 1. 

 

• Discuss how different types of harvest tools impacted the oyster reef

• Discuss changes in the ability of the oyster population to rebound once it becomes 

depleted due to changes in the reef and harvest methods.

• Discuss sustainable harvest, and what measures might help conserve and restore 

oyster populations in the Chesapeake Bay. 

Extension 

After playing the harvest game, have students review the graph in Student Data Sheet 2 comparing 

the oyster landing in Maryland and Virginia and complete the questions below. The "Chesapeake 

Bay Oyster Landings by State, 1880-2011" graph shows how Chesapeake landings declined over time 

to their current level of less than 1% of historical harvests. Two of the dips were probably caused by 

the spread of two oyster diseases, Dermo (which was first seen in the Chesapeake round 1949) and 

MSX (which appeared around 1959). The graph shows data from both states in each bar. For 

example, the total harvest in 1880 was 122,000 thousand pounds (each hash mark is 4 thousand) 

Maryland contributed 75,000 and Virginia contributed 47,000.

1. Which state typically harvested more oysters between 1880-2011? Maryland

2. The data points are much more numerous in the years 1928 through 2008. What might be a 

reason for this? Better monitoring, state and federal efforts increase because harvests are dropping
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3. There are several years in which there is no data such as 1943. Why? There was a break in 

environmental monitoring because World War II caused many men to leave their jobs and 

monitoring was not a high priority.

4. How many thousands of pounds were harvested in Maryland in 1880? 75,000

5. How many thousands of pounds were harvested in Virginia in 1880? 47,000

6. How many thousands of pounds were harvested in Maryland in 1988? 4,000

7. How many thousands of pounds were harvested in Virginia in 1988? 2,000

8. Compare the harvest in Maryland in 1880 and 1988. The 1988 harvest is 4.9% of the harvest in 

1880.

9. Based on the information of the graph, predict when new harvesting methods were started that 

used more efficient technology. 

10. 2 oyster diseases, MSX and Dermo, were found in the Bay in the mid 1900’s. Can you identify 

what impact these had on the oyster populations? There was a small drop in 1949 and steady drop 

of harvest in the 1950s.

Students may be curious about how oyster diseases (MSX and Dermo) and pollution have also 

played a role the decline in the harvest. This is an area of potential investigation or you can discuss 

as a group. 

Background:

Dermo, caused by the pathogen Perkinsus marinus, was first recorded in the Chesapeake Bay in 

1949, and is more prevalent in lower-salinity waters of the Bay. Another disease, MSX (caused by 

Haplosporidium nelsoni), was first found in the Chesapeake Bay in 1959, two years after it was first 

found in Delaware Bay. It is more common in higher-salinity waters. MSX probably arrived with the 

Japanese oyster, Crassostrea gigas, which was intentionally introduced into Delaware Bay to test its 

growth there (it did not grow well).

Of the two diseases, mortality is generally higher with MSX, which killed most of the oysters larger 

than 2 inches (51 mm) in higher-salinity waters (>15 psu) when it reached the Bay. Because most of 

the higher-salinity waters are in Virginia, this had a dramatic effect on the Virginia fishery. Many of 

the surviving high-salinity oysters recovered in the 1970s with wetter weather and thus lower 

salinity, which reduces the virulence of MSX as well as Dermo. Wet years tend to have higher oyster 

survival (because disease intensity is reduced) but lower oyster reproduction (because spawning 

and settlement require water that has 10-12 psu).
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For oysters grown in aquaculture from hatchery seed, there are two main ways to reduce disease 

effects. One is to use artificially selected strains that have been selected for disease resistance. The 

other is to grow triploid oysters, which are produced in hatcheries to have three sets of 

chromosomes, rather than the naturally occurring pair of chromosomes. Triploid oysters grow faster 

than diploids, and usually reach market size before they succumb to one of the diseases. About 95%

of Virginia oyster growers now grow triploid oysters.

(http://chesapeakebay.noaa.gov/fish-facts/oysters)

Evaluation 

Data Sheets 1 and 2 can be used to review student understanding about the lessons.

Exit/Debrief: How did increasingly better harvesting technology affect the oyster populations?

How was this model effective simulating actual harvest methods? How was it ineffective?

Three Dimensional Learning How the Dimensions are 

Addressed

Disciplinary Core

Idea(s)

LS2.A Interdependent 

Relationships in Ecosystems 

Organisms and populations 

of organisms are dependent 

on their environmental 

interactions both with other 

living things and with nonliving factors.

Growth of organisms and 

population increases are 

limited by access to 

resources. 

Predatory interactions may 

reduce the number of 

organisms. 

Students explore oyster harvesting 

methods and analyze graphs of 

historical oyster landings to determine 

the effect of the harvest methods on 

oyster populations and the health of 

oyster reefs. 

Science/Engineering 

Practice(s)

Analyzing and Interpreting 

Data in 6-8 builds on K–5 

experiences and progresses 

to extending quantitative 

analysis in investigations, 

distinguishing between 

correlation and causation, 

and basic statistical 

techniques of data analysis. 

Students gathered evidence about 

harvest methods through a simulation 

that investigates 4 difference harvest 

methods. They also investigate the 

record of oyster populations in 2 

states. 
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Cross-cutting 

Concepts

Patterns can be used to 

identify cause and affect 

relationships. 

Stability and Change -

Students explain stability 

and change in natural or 

designed systems by 

examining changes over 

time.

Students review graphical information

that they have collected and from a 

scientific source to construct an 

explanation that includes quantitative 

relationships between the oyster 

population and increasingly

technological harvest methods.

Students investigate oyster 

populations over time and the effects 

of harvesting methods on the 

population.

Ties to Common 

Core

WHST.6-8.9: Draw evidence 

from literary or 

informational texts to 

support analysis, reflection, 

and research. (MS-LS2-2)

Students use a number of historical 

records to collect evidence about 

conditions in the Bay and compare 

that to current conditions. 

Ties to MD 

Environmental 

Literacy Standards

Standard 4. Populations, 

Communities, and 

Ecosystems

The student will use 

physical, chemical, 

biological, and ecological 

concepts to analyze and 

explain the 

interdependence of humans 

and organisms in 

populations, communities 

and ecosystems.

The student uses historical and 

current information about populations 

and habitats of the Chesapeake Bay to 

provide evidence for the effects of 

conditions on ecosystem health and 

organism populations. 

Module References 

http://ww2.mdsg.umd.edu/CQ/v08n2/main2/

http://chesapeakebay.noaa.gov/fish-facts/oysters

http://chesapeakebay.noaa.gov/fish-facts/oysters

https://www.amaritime.org/

http://www.cbf.org/document.doc?id=523

Maryland Environmental Literacy Standards

http://marylandpublicschools.org/programs/Documents/Environmental/MDEnvironmentalLitStandards.pdf

Additional Resources

http://www.eoearth.org/view/article/51cbee977896bb431f698ed7/

https://www.marinersmuseum.org/sites/micro/cbhf/oyster/mod007.html