Research Publication No. 47

An Investigation of Optimum Methods and Unit Sizes for the Visual Estimation of Abundances of Some Coral Reef Organisms

B D Mapstone
Department of Marine Biology
James Cook University

A M Ayling
Sea Research

March 1998

COVER PAGE & VERSO [Adobe Acrobat Format 82.05KB]
TABLE OF CONTENTS [Adobe Acrobat Format 196.30KB]
EXECUTIVE SUMMARY [Adobe Acrobat Format 107.73KB]
- Acknowledgments ...
INTRODUCTION [Adobe Acrobat Format 337.00KB]
MATERIALS AND METHODS [Adobe Acrobat Format 1329.28KB]
- Location and Time of Field Work
- Organisms Counted
- Sizes and Allocation of Sampling Units..
- Transect Sizes
- Allocation of Sampling Units..
- Counting Procedures..
- Different Methods of Survey..
- Data Handling and Analysis
- Characteristics of the Data
- Biases in Estimates of Population Density
- Preliminary Multivariate Analyses..
- Univariate Analyses..
- Site and Pass Effects..
- Effects of Transect Length and Width..
- Analyses of Auxiliary Variables
- Effects of Migration of Fish Across Transect Borders
- Variations in Counting Times..
- Effects of Depth of Transects..
- Effects of Time of Day on Estimated Density
- Effects of Observer and Methods of Surveying Large Transects..
- Precision and Cost-Efficiency of Sampling
- Precision from Transects of Different Dimensions
- Cost-efficiency of Transects of Different Dimensions
RESULTS [Adobe Acrobat Format 3348.75KB]
- Characteristics of the Data
- Biases in Estimates of Population Density
- Preliminary Analyses - Multivariate Data
- Large Transects - Univariate Analyses
- Site Variation and Effects of Pass
- Effects of Transect Length and Width
- Small Transects - Univariate Analyses..
- Analyses of Auxiliary Variables
- Migration of Fish Across Transect Margins
- Estimated Densities After Correction for Migration
- Variations in Counting Times..
- Effects of the Depth of Transects..
- Effects of the Time-of-Day of Sampling..
- Effects of Observer and Methods of Surveying Large Transects..
- Comparisons of Observers
- Comparisons of Counting Methods
- Precision and Cost-Efficiency of Sampling..
- Precision from Transects of Different Dimensions
- Cost-efficiency of Transects of Different Dimensions
DISCUSSION [Adobe Acrobat Format 1206.19KB]
- Characteristics of the Data and Analytical Methods
- Sources of Bias
- Transect Dimensions..
- Search intensity..
- Depth and Time of Day
- Observers and Counting Methods
- Precision and Cost Efficiency..
- Optimum Transect Dimensions..
- Suggested Procedure for Routine Survey..
- Concluding Remarks
REFERENCES [Adobe Acrobat Format 450.76KB]