Comparison of Schnabel and Lincoln-Peterson Population Estimates Using a Snail Population on Blackburn Fork Creek

John Lewis

Tennessee Technological University

Cookeville, Tennessee 38505

1) Introduction

a) Show differences in the accuracy of two population estimates.

b) Show how one estimate may require less work, but a better estimate is obtained using the lengthier method.

2) Literature Cited

a) Research and Management Techniques for Wildlife and Habitats Edited by Theodore Bookhout, The Wildlife Society, Bethesda, MD 1996 (methods).

b) Forestry Suppliers Incorporated Catalog 52, 2001-2002, Jackson, MS (materials).

c) General Ecology Laboratory Exercises Edited by Daniel L. Combs and Frank J. Bulow, Tennessee Technological University, Cookeville, TN 1998 (methods).

2) Objective

i) The objective of my project will be to compare the precision between the Schnabel and Lincoln-Peterson population estimation methods using a snail population on Blackburn Fork Creek.

3) Hypothesis

i) There will be no difference between the Lincoln-Peterson population estimate and the Schnabel estimate.

4) Materials and Methods

a) Materials

i) Insulated hip waders

ii) Surber-type square foot invertebrate sampler

iii) Collection tray

iv) Marking paint (clear fingernail polish)

b) Methods

i) Randomly place the Surber sampler over an area of substrate with the net trailing downstream.

ii) Substrate within the frame is disturbed, dislodging all gastropods which are swept into the net by the current.

iii) Rocks and all other substrate material are then scrubbed thoroughly within the sampler to remove tightly adhering gastropods.

iv) The snails will be placed in a collecting tray and marked with clear marking paint (this increases the chance that all animals are equally likely to be captured).

v) Results will be marked on the data sheets.

vi) Animals will be randomly redistributed throughout the test area; then another sample will be taken.

vii) This collection will be repeated once more (two recaptures) to satisfy the requirements for the Schnabel estimate(Bookhout 1996).

5) Timeline

a) Research literature 10-15 hrs.

b) Data collection 6-8 hrs.

c) Analysis of data 3-5 hrs.

d) Consult literature 3-5 hrs.

e) Assembling presentation 6-8 hrs.

f) Presentation of results 1 hr.

g) Total 28-41 hrs.

6) Results

a) The Peterson method gave an extremely low estimate for the number of snails in Blackburn Fork.

b) The Schnabel method gave a more realistic population estimate.

c) The accuracy of the estimate increased with the number of samples taken.

7) Conclusions

a) Although it takes more time to do numerous capture events, the estimate one receives is more accurate.

b) Biologists should use the Schnabel method over the Peterson method if at all possible.

c) Time should be the only constraint on the number of samples taken.

d) Accuracy is important making informed management decisions.