Pearlshell Problems - LSU AgCenterLSU AgCenter • 4-H Youth Wetlands Program • 2015 • High School • Pearlshell Problems Qualitative data – descriptions of conditions as opposed

LSU AgCenter • 4-H Youth Wetlands Program • 2015 • High School • Pearlshell Problems

Grade level: High school Subject area: Science Duration: One class period Setting: Classroom Vocabulary: Endangered species Habitat Habitat Suitability Index Hydrology Invertebrate Population density Qualitative data Sediment Threatened species Turbidity Watershed

Pearlshell Problems Teacher Instructions

Overview:

This lesson introduces students to the life history, status and preservation

of the endangered Louisiana pearlshell mussel, Margaritifera hembeli.

Students will interpret data form simulated surveys of a series of streams

and determine factors that contribute to maintaining healthy populations

of pearlshells.

Learning Objectives:

The students will:

Become familiar with the life history of Louisiana pearlshell

mussels.

Analyze and interpret sample population data.

Determine factors correlated with healthy populations of mussels

based on evidence presented in the simulated data.

Develop a series of Habitat Suitability Index models for

Louisiana pearlshell mussels

Reflect on beneficial resource management practices for the

Louisiana pearlshell mussel.

Materials List:

Computer with Internet access (optional)

Projection system (optional)

Sample topographic map (optional)

Markers (optional)

Chart paper (optional)

Grade Level Expectations:

Physical Science

Utilize mathematics, organizational tools and graphing skills to solve problems. (SI-H-A3)

Use technology when appropriate to enhance laboratory investigations and presentations of

findings. (SI-H-A3)

Gather and organize data in charts, tables and graphs. (PS-H-A1)

Biology

Describe how investigations can be observation, description, literature survey, classification

or experimentation. (SI-H-A2)

Conduct an investigation that includes multiple trials; record, organize and display data

appropriately. (SI-H-A2)




findings. (SI-H-A3)

Analyze the dynamics of a population with and without limiting factors. (LS-H-D3)

Analyze positive and negative effects of human actions on ecosystems. (LS-H-D4) (SE-H-

A7)

Explain how selected organisms respond to a variety of stimuli. (LS-H-F3)

Explain how behavior affects the survival of species. (LS-H-F4)

Environmental Science

Describe how investigations can be observation, description, literature survey, classification

or experimentation. (SI-H-A2)

Conduct an investigation that includes multiple trials; record, organize and display data

appropriately. (SI-H-A2)



findings. (SI-H-A3)

Explain how species in an ecosystem interact and link in a complex web. (SE-H-A7) (SE-H-

A10)

Give examples and describe the effect of pollutants on selected populations. (SE-H-A11)

Analyze data to determine the effect of preservation practices compared to conservation

practices for a sample species. (SE-H-B2)

Determine the interrelationships of clean water, land and air to the success of organisms in a

given population. (SE-H-C1)

Common Core State Standards:

E5 Read, write and speak grounded in evidence.

E3 Obtain, synthesize and report findings clearly and effectively in response to task and

purpose.

S5 Analyze and interpret data.

S6 Construct explanations and design solutions.

Vocabulary Definitions:

Endangered species – organisms at high risk of extinction through all or part of its range.

Habitat Suitability Index – a graphical, word or mathematical model showing the relationship among

various habitat conditions and the habitat’s suitability for a particular organism.

Habitat – where an organism lives.

Hydrology – the behavior of water as it occurs in the atmosphere, on the surface of the ground and

underground.

Invertebrate – animal without a backbone.

Population density – number of organisms per unit area.


Qualitative data – descriptions of conditions as opposed to measurements.

Sediment – fragmented material from weathering of rocks that is transported by, suspended in or

deposited by water or air, or is accumulated in beds by other natural agents.

Threatened species – organisms at high risk for becoming extinct in the foreseeable future.

Turbidity – cloudiness of water due to sediment or other suspended materials.

Watershed – an area of land that drains water to a particular stream or river.

Background Information: Invertebrate organisms are important and are not often considered components of

ecosystems. In fact, invertebrate organisms account for much of the sheer numbers and diversity of

life on earth. Invertebrates include insects, worms, clams, sponges, starfish, squid and many others.

Invertebrate organisms are very important in ecosystems. For example, insects play a role in plant

pollination and reproduction, snails and worms help recycle nutrients and beetles help control pest

populations. Many marine ecosystems are dominated by invertebrates and the role they play in food

webs.

Louisiana pearlshells, Margaritifera hembeli, are bivalve mollusks in the family

Margaritiferidae. Their origins can be traced back in the fossil record and demonstrate that they have

played role in freshwater ecosystems for several hundred million years. Like many other invertebrate

organisms, the Louisiana pearlshell mussel is currently considered an endangered species at a state

level and is also listed as a threatened species on the Endangered Species Act. (See Protecting and

Conserving Natural Resources in the General Wetlands Information for more details.) Although the

root causes of endangerment are varied, four main areas of concern are often cited: habitat changes

and loss; disruption or fragmentation; displacement by invasive species; and overharvesting. Perhaps

the biggest risk factor for these mussels has been habitat changes. In central Louisiana, where they

are found, much of its original habitat has been altered by the conversion of mixed pine hardwood

forests into agricultural uses such as logging and farming. Both of these practices alter the hydrology

and water quality of the streams that flow through the region.

Currently, the Louisiana pearlshell mussel is limited to 22 headwater streams (small

watersheds) in central Louisiana. Although these bivalves have worldwide relatives, those found in

the Red River watershed are unique and well-adapted to conditions found in the region. Surveys

conducted in the late 1990s discovered two distinct subpopulations of pearlshells on opposite sides of

the Red River. This suggests that these two populations are isolated from each other and are starting

to diverge genetically. The fact that the species currently exists in a few small isolated streams

suggests that the historic range of pearlshells was larger in the past. Data obtained in these surveys

show that pearlshell mussels occur in beds with population densities ranging from 20 per square

meter up to 300 per square meter. Population density appears to be controlled by several factors. For

example, healthy, dense populations of mussels are normally found in small sandy stable bottomed

creeks with clear (low turbidity) fast-flowing, shallow water. In contrast, numbers are low or

nonexistent in deeper stagnate pools with silt or soft bottoms resulting from sediment settling on the

bottom.

Louisiana pearlshell mussels have an oblong brown shell reaching lengths of up to about 4

inches. Louisiana pearlshell mussels have a complex life history with several stages that are


vulnerable to environmental change. During the spawning period, males discharge sperm into the

water. Nearby females collect the sperm by siphoning water. Females are usually fertile in late fall

and release glochidia in early winter. The glochidia are small larvae which attach to the gills of fish.

The larvae are not parasitic even though they attach themselves to a host organism. Rather, they filter

feed on the water that the fish pump over their gills. When they grow too large to remain in the gills

they detach and settle to the stream bottom as juvenile mussels. Fish thus play an important role in

dispersing mussels throughout their range and, consequently, any structure or dam that impedes fish

also impedes mussels.

As juvenile and adult mussels continue to filter feed, removing detritus from water, they rely

on currents to bring them food. Increased sediment caused by erosion from logging or farming

operations limits their ability to pull their food from the water. Changes to the landscape also affect

the volume of runoff received by streams. Practices such as clear-cutting raise stream velocities and

scour stream bottoms of sediment suitable for adult mussels. Ironically, although mussels are found

in streams, their health is tightly linked to activities on surrounding lands within their watershed.

A number of in-stream threats also contribute to the decline in mussel populations. In addition

to water impoundment from development of man-made reservoirs, beaver activity has also caused

fragmentation of populations. For example, a population of almost 1,000 mussels found in 1985 was

flooded by a beaver dam and eliminated within a year. Beaver ponds reduce stream velocity,

therefore decreasing turbidity. Much of the sediment, however, settles on stream or river bottoms,

resulting in a softer, less suitable bottom for the attachment of pearlshells. In addition, beaver dams

create physical barriers to host fish that transport mussel glochidia to new habitats. Stream habitats

also are affected by increased turbidity resulting from cattle crossing and wading in streams. Road

and bridge construction and gravel mining also have played a part in the decline of pearlshell

mussels.

Researchers study effects on fish and wildlife habitat from water or land use changes, such as

in the streams where Louisiana pearlshells live. The reports they develop are called Habitat

Suitability Index (HSI) models. These models put habitat information into a useful format for

understanding the environmental requirements of a species. The models then can be used to

determine whether an area is suitable for maintaining a healthy population. Typically, these models

reference published science sources in an effort to consolidate scientific information on species-

habitat relationships. HSI models are usually presented in three basic formats – graphic, word and

mathematical. The models should be viewed as hypotheses of species-habitat relationships rather than

statements of proven cause and effect relationships. Although the majority of HSI models are built

around quantitative data such as “percent tree canopy” shown in the beaver HIS model (fig. 1), they

also can be constructed from descriptive qualitative data. For example, field researchers may rate

variables such as stream flow and turbidity as low, medium or high. HSI models serve as a basis for

improved decision making and increased understanding of habitat relationships because they specify

hypotheses of habitat relationships that can be tested and improved.


Figure 1. Sample HSI model for beaver. The model shows the relationship between habitat suitability

and percent tree canopy closure. In this case, the best habitat for beaver has canopy closure between

40% and 60%. (Allen, 1982.)


and percent of trees ranging from 2.5 to 15.2 cm in diameter at breast height. In this case, the best

habitat for beaver is composed solely of trees in this size range. (Allen, 1982.)


and average height of shrub canopy adjacent to the stream. In this case, the best habitat for beaver

has a shrub canopy greater than 2.0 meters high. (Allen, 1982.)


Advance Preparation:

1. Make copies of:

A. Rare Animals of Louisiana: Louisiana Pearlshell (one per student)

B. Pearlshell Sampling Location Data (one per student)

C. Habitat Suitability Index Model: Louisiana Pearlshell Mussels Work Sheet (one per

student)

2. Secure computer, Internet access and projection system for image viewing(optional).

3. Secure sample topographic map (optional).

4. Collect chart paper and markers (optional).

5. Print Beaver Habitat Suitability Index (optional, see resources).

Note: Teachers may want to print a complete Habitat Suitability Index model for student

review, such as the beaver model cited in the reference section. Teachers also may want to

print and review topographic maps from the Bayou Rigolette watershed in central Louisiana

in support of this activity. Maps of the watershed can be printed for free from the Louisiana

Department of Natural Resources web-based GIS service called SONRIS. Click on the tutorial

link for instructions for use of that site (see SONRIS maps in resources list). You also may

download GoogleEarth to view the sites.

Procedure:

1. Ask students to list a few types of invertebrates. (Insects, crustaceans, spiders, sponges,

worms, clams, etc.)

2. Ask students to give a few examples of the importance of invertebrates in ecosystems. (For

example, bees’ role in pollination of crops.)

3. Explain to them that invertebrates have greater numbers, mass, diversity and importance than

any other type of life on earth, yet they are sometimes overlooked in ecosystem management.

4. Explain to students that invertebrates often suffer from endangerment for the same reasons as

other organisms that we are more familiar with. The leading causes are habitat destruction,

invasive species, habitat alteration and overharvesting.

5. If Internet access is available show students images of Louisiana pearlshell mussels. Briefly

describe the life history and biology of mussels. (More information is available in the

background and the resource section).

6. Distribute “Rare Animals of Louisiana: Louisiana Pearlshell.” Show students where

Louisiana pearlshell mussels are found using maps (such as the one in the “Rare Animals of

Louisiana: Louisiana Pearlshell” included in the Blackline Masters), Google Earth or other

methods. (Their range is on either side of the Red River at the confluence of Bayou Rapides

and Bayou Rigolette as shown in Blackline Master.)

7. Tell students that they have five minutes to review “Rare Animals of Louisiana: Louisiana

Pearlshell” and will be using their reading and a set of simulated data to determine the factors

that contribute to a healthy Louisiana pearlshell habitat. They will then use these data to

develop graphical models called Habitat Suitability Indexes for Louisiana pearlshell mussels.

8. Define Habitat Suitability Index (HSI) for the students (a graphical, word, or mathematical

model that shows the relationship between various habitat conditions and the habitat’s

suitability for a particular organism). Show examples from the beaver HSI as needed.

9. Distribute Pearlshell Sampling Location Data and Habitat Suitability Index Model: Louisiana

Pearlshell Mussels to each student.


10. Tell the students to read and follow the directions on the Habitat Suitability Index Model:

Louisiana Pearlshell Mussels work sheet. They should use the Pearlshell Sampling Location

Data to answer the questions. Give them 10-15 minutes to complete the work sheet.

(Optional: If class time is limited, you may assign work sheet for homework and discuss the

following class period.)

11. Optional: After students complete the work sheet, if time allows, have individual students

prepare charts showing the HSI models they created on the student work sheet. Prompt the

students to tell the story of the graph in the following form: “As ____________

(increases/decreases) the habitat suitability (increases/ decreases).”

12. Lead a closing discussion and reflection about the students’ observations on the HSI models

they created. Include any other reflection questions that may pertain to the students

understanding.

a. What relationships did you see between habitat suitability and turbidity? (As turbidity

increases, habitat becomes less suitable.)

b. Between habitat suitability and average flow? (Medium flow is most suitable; as it

increases or decreases, habitat becomes less suitable.)

c. Between habitat suitability and stream bottom? (Harder bottoms are more suitable

habitat.)

d. Between habitat suitability and average depth? (As streams become deeper, habitats

become less suitable.)

e. Between habitat suitability and land use? (Forested lands are more suitable habitat.)

f. How might we change our land use practices to lessen the impact on pearlshells?

(Avoiding logging and grazing near stream edges, leaving strips of plants to buffer”

the edges of streams to catch run off, etc.)

g. What is the significance of modeling and the Habitat Suitability Index in the

management of threatened or endangered species? (Identifies the most suitable habitat

conditions for a variety of variables, allowing managers to pinpoint issues and

improve conditions.)

13. After the discussion, collect student work sheets, and score using the Habitat Suitability Index

Model: Louisiana Pearlshell Mussels Key.

Blackline Masters:

“Rare Animals of Louisiana: Louisiana Pearlshell”

Pearlshell Sampling Locations Data

Habitat Suitability Index Model: Louisiana Pearlshell Mussels

Habitat Suitability Index Model: Louisiana Pearlshell Mussels Key

Extension Ideas:

This lesson may be used as an extension of the “Watershed” activity from the Youth Wetlands

2013 Binder, pg. 188. You also can find the lesson online at www.agcenter.lsu.edu/YWW

under the curriculum link. (or directly at

http://www.lsuagcenter.com/en/4H/about_4H/programs/science_engineering_technology/You

th+Wetlands+Week/Curriculum/)

http://www.agcenter.lsu.edu/YWW

http://www.lsuagcenter.com/en/4H/about_4H/programs/science_engineering_technology/Youth+Wetlands+Week/Curriculum/

http://www.lsuagcenter.com/en/4H/about_4H/programs/science_engineering_technology/Youth+Wetlands+Week/Curriculum/


Resources:

Allen, A.W. 1982. Habitat Suitability Index models: Beaver. U.S. Fish and Wildlife Service

publication FWS/OBS-82/10.30. http://www.nwrc.usgs.gov/wdb/pub/hsi/hsi-030.pdf

Habitat Suitability Index models from the National Wetlands Inventory along with sample HIS

models can accessed at: http://www.nwrc.usgs.gov/wdb/pub/hsi/hsiintro.htm

IUCN red list of threatened species, listing information for Louisiana pearlshell mussels:

http://www.iucnredlist.org/details/full/12803/0

Johnson, P.D. and Brown, K.M. 1998. Intraspecific life history variation in the threatened Louisiana

pearlshell mussel, Margaritifera hembeli, pp. 317-329. Freshwater Biology 40:2,

10.1046/j.1365-2427.1998.00356.x:

http://onlinelibrary.wiley.com.libezp.lib.lsu.edu/doi/10.1046/j.1365-2427.1998.00356.x/pdf

Johnson, P.D. and Brown, K.M. 2000. The importance of microhabitat factors and habitat stability to

the threatened Louisiana pearlshell, Margaritifera hembeli (Conrad). Canadian Journal of

Zoology 78:271-277, 10.1139/z99-196:

http://www.nrcresearchpress.com.libezp.lib.lsu.edu/doi/abs/10.1139/z99-196

Louisiana Department of Wildlife and Fisheries. Rare animals of Louisiana: Louisiana pearlshell”.

http://www.wlf.louisiana.gov/sites/default/files/pdf/fact_sheet_animal/32145-

Margaritifera%20hembeli/margaritifera_hembeli.pdf

SONRIS Maps : http://sonris-

www.dnr.state.la.us/gis/agsweb/IE/JSViewer/index.html?TemplateID=181

United States Geological Survey. Science in your watershed.

http://water.usgs.gov/wsc/glossary.html#

http://www.nwrc.usgs.gov/wdb/pub/hsi/hsi-030.pdf

http://www.nwrc.usgs.gov/wdb/pub/hsi/hsiintro.htm

http://www.iucnredlist.org/details/full/12803/0

http://onlinelibrary.wiley.com.libezp.lib.lsu.edu/doi/10.1046/j.1365-2427.1998.00356.x/pdf

http://www.nrcresearchpress.com.libezp.lib.lsu.edu/doi/abs/10.1139/z99-196

http://www.wlf.louisiana.gov/sites/default/files/pdf/fact_sheet_animal/32145-Margaritifera%20hembeli/margaritifera_hembeli.pdf

http://www.wlf.louisiana.gov/sites/default/files/pdf/fact_sheet_animal/32145-Margaritifera%20hembeli/margaritifera_hembeli.pdf

http://sonris-www.dnr.state.la.us/gis/agsweb/IE/JSViewer/index.html?TemplateID=181

http://sonris-www.dnr.state.la.us/gis/agsweb/IE/JSViewer/index.html?TemplateID=181

http://water.usgs.gov/wsc/glossary.html%23

Rare Animals of Louisiana

Louisiana Pearlshell

Margaritifera hembeli Federal Status: Threatened (February 5, 1988; September 24, 1993) State Status: Endangered (December 20, 1989) Rarity Rank: S1/G1 Identification:

The shell of this freshwater mussel is oblong with moderately full beaks without obvious sculpture.

The posterior ridge is low, the anterior end is rounded and the ventral margin is generally straight or slightly curved.

The shell surface has uneven growth lines and, if sculptured on the posterior end, it is very faint.

The epidermis is brown to blackish and the nacre is white to purple with numerous pits. Adults are about 100 mm (3.9 in) long, 50 mm (2 in) high and 30 mm (1.2 in) wide.

Habitat: Small sandy streams within mixed pine hardwood forest. Food Habits:

Adults are detritivore Immatures are parasitic

Threats:

Siltation, pollution, and other factors affecting water quality Beaver dams may also constitute a threat by

changing the water flow in streams. Beneficial Management Practices:

Protect from siltation and pollution the streams where the species occurs

Control beaver population Monitor population Research to identify life cycle and ecology

of the species. U. S. Range: AR, LA References: NatureServe Explorer: An online encyclopedia of life [web application]. 2006. Version 6.1. Arlington, Virginia, USA: NatureServe. Available: http://www.natureserve.org/explorer. (Accessed: Aug 28, 2009).

Gary Lester, La. Dept. of Wildlife & Fisheries

http://www.natureserve.org/explorer


Pearlshell Sampling Locations and Data

Sampling location

Pearlshell density

Turbidity Flow Stream bottom

Depth Land use

1 0 / m2 Low Low Soft Deep Forest

2 150 / m2 Low Med Hard Shallow Forest

3 125 / m2 Low Med Hard Shallow Forest

4 0 / m2 Low Low Soft Deep Forest

5 65 / m2 Low Low Hard Shallow Forest/grazing

6 20 / m2 Med Med Med Shallow Grazing

7 0 / m2 High High Hard Shallow Logging

8 0 / m2 High High Hard Shallow Logging

9 17 / m2 Med Med Med Med Logging/grazing

10 0 / m2 High High Soft Deep Forest/logging

1

9

10

00

0

8

7

6

5

4

3

2

Beaver Dam

Beaver Dam

Wetlands Program provided by LSU AgCenter

Pearlshell Problemsstudent activity sheet

Name ____________________________________ Date_______

Habitat Suitability Index Model: Louisiana Pearlshell Mussel Work SheetTake a few minutes to review the Pearlshell Sampling Locations and Data handout. Use your background reading and infor-mation from the sampling data to answer the following questions:

1. Which sampling location has the highest mussel density? ______________________________

2. What is the density at the location you answered for question 1? _________________________

3. Which sampling locations have the lowest mussel density? ______________________________

4. What is the density at the locations you put answered for question 3? ____________________

5. Describe the ideal habitat for mussels. (This is a type of Habitat Suitability Index model.)

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

______________________________________________________________________________

6. Suggest two reasons turbidity is higher in logging areas.

_______________________________________________________________________________

_______________________________________________________________________________

7. Suggest possible reasons the stream survey detected no mussels upstream from beaver dams.

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

_______________________________________________________________________________

______________________________________________________________________________


Pearlshell Problemshabitat suitability index model

(continued)

Name ____________________________________ Date_______

Look at the three graphs below. They are Habitat Suitability Index models for beaver. On the X axis is a habitat variable. On the Y axis is a rating of how good or “suitable” the habitat is, with a rating of 1.0 being best. Use the graphs to answer the following questions about beaver habitat. Keep in mind that beaver and Louisiana pearlshell mussels are competing for the same streams!

8. What is the best percent tree canopy cover closure for beaver habitat? _________________

9. True or false: A lower percentage of trees in the range of 2.5 to 15.2 cm dbh (diameter at breast height) is better for beaver habitat. _________________________

10. Fill in the blanks: As the average height of shrubs increases, the habitat is _________________until the shrubs reach an average height of ___________________________.


Name ____________________________________ Date_______

Use the HSI models for beaver above and the Pearlshell Sampling Locations and Data handout to develop a series of graphical HSI models for Louisiana pearlshells. To determine the suitability index of a given variable, divide the density of pearlshells in that area by 150m2. The suitability index range is established by the following: 150m2/150m2 = 1, and 0m2/150m2 = 0. (Remember: sampling areas with a higher population density (animals per unit area) are better habi-tat, and therefore have a higher suitability index.)

11. Average Turbidity

12. Average Flow

Low Medium High

Low Medium High

Soft Medium Hard

Shallow Medium Deep

Logging Grazing Forest

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

Low Medium High

Low Medium High

Soft Medium Hard

Shallow Medium Deep


1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0H

abita

t Sui

tabi

lity

1.0

.5

0.0

Hab

itat S

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bilit

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1.0

.5

0.0

Hab

itat S

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y


(continued)


Name ____________________________________ Date_______

13. Stream bottom

14. Average Depth

15. Land Use

Low Medium High

Low Medium High

Soft Medium Hard

Shallow Medium Deep


1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

yLow Medium High

Low Medium High

Soft Medium Hard

Shallow Medium Deep


1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

Low Medium High

Low Medium High

Soft Medium Hard

Shallow Medium Deep


1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

uita

bilit

y

1.0

.5

0.0

Hab

itat S

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y


(continued)


Pearlshell Problemsstudent activity sheet-KEY

Name ____________________________________ Date_______

Habitat Suitability Index Model: Louisiana Pearlshell Mussel Work SheetTake a few minutes to review the Pearlshell Sampling Locations and Data handout. Use your back-ground reading and information from the sampling data to answer the following questions:

1. Which sampling location has the highest mussel density? (2)

2. What is the density at the location you answered for question 1? (150m2)

3. Which sampling locations have the lowest mussel density? (1,4,7,8,10)

4. What is the density at the locations you put answered for question 3? (0m2)

5. Describe the ideal habitat for mussels. (This is a type of Habitat Suitability Index model.) The data in the Pearlshell Sampling Locations and Data handout suggest that the ideal stream habitat (highest population density) is in areas with low turbidity, medium stream flow, a hard stream bottom and shallow depths surrounded by forests.

6. Suggest two reasons turbidity is higher in logging areas. (Increased turbidity results from higher erosion due to removal of forest cover. Faster stream flow and increased turbidity can be caused by in-creased runoff.)

7. Suggest possible reasons the stream survey detected no mussels upstream from beaver dams. (Increased sediment in slow-moving streams resulting from dam construc-tion changes the bottom substrate. Beaver dams can limit the range of pearlshell mussels by preventing the dispersal of glochidia by host fish.)


Pearlshell Problemshabitat suitability index model-KEY

(continued)

Name ____________________________________ Date_______

Look at the three graphs below. They are Habitat Suitability Index models for beaver. On the X axis is a habitat variable. On the Y axis is a rating of how good or “suitable” the habitat is, with a rating of 1.0 being best. Use the graphs to answer the following questions about beaver habitat. Keep in mind that beaver and Louisiana pearl-shell mussels are competing for the same streams!

8. What is the best percent tree canopy cover closure for beaver habitat? (40%-60%)

9. True or false: A lower percentage of trees in the range of 2.5 to 15.2 cm dbh (diameter at breast height) is better for beaver habitat. (False)

10. Fill in the blanks: As the average height of shrubs increases, the habitat is (more suitable) until the shrubs reach an average height of (6.6 ft.).


Pearlshell Problemshabitat suitability index model -KEY

(continued)

Name ____________________________________ Date_______

Use the HSI models for beaver above and the Pearlshell Sampling Locations and Data handout to develop a series of graphical HSI models for Louisiana pearlshells. To determine the suitability index of a given variable, divide the density of pearlshells in that area by 150m2. The suitability index range is established by the following: 150m2/150m2 = 1, and 0m2/150m2 = 0. (Remember: sampling areas with a higher population density (animals per unit area) are better habi-tat, and therefore have a higher suitability index.)

11. Average Turbidity

12. Average Flow

Low Medium High

Low Medium High

Soft Medium Hard

Shallow Medium Deep


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Low Medium High

Low Medium High

Soft Medium Hard

Shallow Medium Deep


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Pearlshell Problemshabitat suitability index model -KEY

(continued)

Name ____________________________________ Date_______

13. Stream bottom

14. Average Depth

15. Land Use

Low Medium High

Low Medium High

Soft Medium Hard

Shallow Medium Deep


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Low Medium High

Soft Medium Hard

Shallow Medium Deep


1.0

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1.0

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Documents

Pearlshell Problems - LSU AgCenterLSU AgCenter • 4-H Youth Wetlands Program • 2015 • High School • Pearlshell Problems Qualitative data – descriptions of conditions as opposed