United States

Environmental Protection

Agency

Guidance for Conducting

Fish and Wildlife

Consumption Surveys

EPA-823-B-98-007

November 1998

Office of Water

(4305)
Guidance for Conducting Fish and 

Wildlife Consumption Surveys

Office of Science and Technology

Standards and Applied Science Division

Office of Water

United States Environmental Protection Agency

Washington, DC
CONTENTS

iii

CONTENTS

TABLES .............................................................................. vi

GLOSSARY AND ABBREVIATIONS ................................................... vii

ACKNOWLEDGMENTS ............................................................... x

EXECUTIVE SUMMARY ............................................................ ES-1

SECTION 1: INTRODUCTION ........................................................ 1-1

1.1 Historical Perspective ..................................................... 1-1

1.2 Purpose ................................................................ 1-2

1.3 Objectives .............................................................. 1-3

1.4 Relationship of Manual to Other Guidance Documents .......................... 1-3

1.5 Organization of This Manual ............................................... 1-3

SECTION 2: SURVEY OBJECTIVES AND INFORMATION NEEDS ...................... 2-1

2.1 Overview ............................................................... 2-1

2.2 Definition of Survey Objectives ............................................. 2-1

2.3 Information Needs ....................................................... 2-5

2.4 Summary ............................................................... 2-8

SECTION 3: SURVEY APPROACHES AND SELECTION CRITERIA ..................... 3-1

3.1 Overview ............................................................... 3-1

3.2 Types of Surveys ........................................................ 3-1

3.2.1 Telephone Survey ................................................. 3-1

3.2.2 Mail Survey ...................................................... 3-1

3.2.3 Diary ........................................................... 3-2

3.2.4 Personal Interview ................................................. 3-2

3.2.5 Creel Survey ..................................................... 3-2

3.3 Selection Criteria ........................................................ 3-2

3.3.1 Target Population of Concern ........................................ 3-4

3.3.2 Accuracy ........................................................ 3-5

3.3.3 Time Frame ...................................................... 3-6

3.3.4 Resource Considerations ........................................... 3-7

3.3.5 Characteristics of the Source of the Fish or Wildlife ...................... 3-7

3.4 Summary ............................................................... 3-7

SECTION 4: INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION ............. 4-1

4.1 Overview ............................................................... 4-1

4.2 General Instrument and Study Design Issues ................................... 4-1

4.3 General Statistical Analysis and Data Interpretation Considerations ................ 4-5

4.4 General QA/QC Considerations ........................................... 4-10

4.5 Telephone Survey ....................................................... 4-10

4.5.1 Advantages ..................................................... 4-10

4.5.2 Disadvantages ................................................... 4-11
CONTENTS

iv

4.5.3 Specific Issues for Instrument and Study Design: 

Telephone Survey .............................................. 4-11

4.5.4 Specific Issues for Statistical Sampling and Analysis: 

Telephone Survey .............................................. 4-12

4.5.5 Specific Issues for QA/QC: Telephone Survey ........................ 4-13

4.6 Mail Survey ......................................................... 4-13

4.6.1 Advantages ................................................... 4-13

4.6.2 Disadvantages ................................................. 4-14

4.6.3 Specific Issues for Instrument and Study Design: 

Mail Survey ................................................... 4-14

4.6.4 Specific Issues for Statistical Sampling and Analysis: 

Mail Survey ................................................... 4-16

4.6.5 Specific Issues for QA/QC: Mail Survey ............................ 4-16

4.7 Diary .............................................................. 4-16

4.7.1 Advantages ................................................... 4-16

4.7.2 Disadvantages ................................................. 4-17

4.7.3 Specific Issues for Instrument and Study Design: Diary ................. 4-17

4.7.4 Specific Issues for Statistical Sampling and Analysis: Diary ............. 4-18

4.7.5 Specific Issues for QA/QC: Diary .................................. 4-18

4.8 Personal Interview .................................................... 4-19

4.8.1 Advantages ................................................... 4-19

4.8.2 Disadvantages ................................................. 4-19

4.8.3 Specific Issues for Instrument and Study Design: 

Personal Interview .............................................. 4-20

4.8.4 Specific Issues for Statistical Sampling and Analysis: 

Personal Interview .............................................. 4-21

4.8.5 Specific Issues for QA/QC: Personal Interview ....................... 4-21

4.9 Creel Survey ......................................................... 4-21

4.9.1 Advantages ................................................... 4-21

4.9.2 Disadvantages ................................................. 4-22

4.9.3 Specific Issues for Instrument and Study Design: Creel Survey ........... 4-22

4.9.4 Specific Issues for Statistical Sampling and Analysis: 

Creel Survey .................................................. 4-24

4.9.5 Specific Issues for QA/QC: Creel Survey ............................ 4-24

SECTION 5: SUMMARY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5-1

REFERENCES .................................................................. Ref-1

APPENDIX A: SUMMARY OF SURVEY METHODS

APPENDIX B: EXAMPLES OF SURVEY QUESTIONNAIRES

Telephone Survey: EPA/Delaware Consumption Survey Phone Questionnaire

Mail Survey: 1991/92 Michigan Fish Eaters Survey

Mail Survey: Your Family and Fishing: A Questionnaire for the Children’s Fishing Project

Mail Survey: New York State Fisher Cohort Study

Diary: Fishing Trips and Fish Meals
CONTENTS

v

Diary: Fishing Trips and Fish Consumption

Personal Interview: 1991 Columbia River InterTribal Fish Commission Survey

Creel Survey: San Diego Bay Fisher Survey Questionnaire

Creel Survey: Alabama State-wide Freshwater Fish Consumption Survey

Creel Survey: Hudson River Fisher Survey
TABLES

vi

TABLES

Table 1 Potential Information Requirements for Fish and Wildlife 

Consumption Surveys . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-6

Table 2 Example Development of a Survey . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-9

Table 3 Comparison of Five Fish and Wildlife Consumption Survey Approaches 

Using Various Selection Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-3

Table 4 Characteristics of Creel Survey Methods ...................................... 4-23
GLOSSARY AND ABBREVIATIONS

vii

GLOSSARY AND ABBREVIATIONS

Access Point Survey A survey that is administered at locations where fishers or hunters

gain entry to fishing or hunting areas. Examples include boat ramps,

docks, and wildlife refuge check stations.

Accuracy A measure of agreement, expressed numerically as a percentage,

between a measured value and an accepted or true value.

Aerial Survey Flying over a fishing or hunting area to obtain an estimate of the

total population participating in the activity during the period of

time in which a creel survey or personal interviews are conducted.

This procedure is used to estimate the percentage of the population

interviewed when other sampling strategies (e.g., probability

sampling) cannot be used.

Bias Property of a statistical estimator that consistently overestimates or

underestimates a population parameter. The discrepancy between

the expected value of an estimator and the population parameter

being estimated.

Bioaccumulative Chemical A chemical that is accumulated in the tissue of organisms through

any route, including respiration, ingestion, or direct contact with air,

water, or sediment.

Bivariate Analysis Statistical analysis that involves two variables.

Bus Route Method A method for conducting a creel survey that involves visiting

predetermined fishing sites at predetermined times to interview

fishers.

CATI Computer-assisted telephone interviewing, a method of telephone

interviewing in which a structured questionnaire is programmed

into a computer. The interviewer enters the respondent’s replies

directly into the computer program.

Census A complete enumeration a population.

Confidence Interval The range of values within which it is estimated a population

parameter lies with a defined level of confidence based on sample

data.

Confidence Level The probability that a population parameter lies within a given

range.

Descriptive Statistics The branch of statistics that involves summarizing, tabulating,

organizing, and graphing data for the purpose of describing a
GLOSSARY AND ABBREVIATIONS

viii

sample of objects or individuals that have been measured or

observed.

Frequency Distribution A tabular or graphical presentation of the number of times each

value occurs in the data set.

Inferential Statistics The branch of statistics that involves making inferences about the

value of one or more population parameters, on the basis of sample

statistics. The most common applications of inferential statistical

procedures are estimation and hypothesis testing.

Measures of Central Tendency Descriptive statistics that identify the center or middle of a

distribution. Common measures are the mode, mean, and median.

Measures of Dispersion Descriptive statistics that identify the spread of values of numerical

data. Common measures are the range, standard deviation, and

variance.

Multivariate Analysis The analysis of data consisting of multiple variables and examination associations among variables. (e.g., regression and

correlation analysis, analyses of variance and covariance.)

Nonparametric Test A statistical test of a hypothesis that is not a statement about population parameters and makes no assumptions about the distribution

of the data.

Parametric Test A statistical test of a hypothesis about one or more population

parameters. Parametric tests require a knowledge of the functional

form of the population from which the samples are drawn.

Probability The chance that a given event or result will occur.

QA Quality assurance; the steps and procedures used to review data and

determine whether the data quality objectives of a study have been

met.

QC Quality control; the procedures and practices implemented as part

of a study to minimize errors and ensure the accuracy of data.

RDD Random digit dialing; a method used to select samples for

telephone surveys by random selection of telephone numbers within

working exchanges. This method permits coverage of both listed

and unlisted telephone numbers.

Recall Error A response error resulting from a subject’s inaccurate recollection

of particular events.
GLOSSARY AND ABBREVIATIONS

ix

Rolling Cohort Method A survey method that involves randomly placing survey

participants into groups (cohorts), which are then sequentially

surveyed over equally spaced intervals, for example, intervals of

two or more weeks. Each cohort is asked to provide recall data for

a period of time equal to the interval spacing between cohort

surveys. This method is typically used to provide coverage over an

entire year while avoiding the problems associated with long recall

periods.

Roving Creel Survey A creel survey that is conducted by having the interviewer move

through the survey area in a random or defined pattern to contact

fishers.

Stratified Sample Design Sampling design that separates population elements into nonoverlapping groups (strata) from which samples are to be selected.

The establishment of strata occurs prior to sampling.

Univariate Analysis Statistical analysis involving a single variable.

Weights Weights are needed when sampled unites are selected by unequal

probability sampling. Weights are used to assign greater relative

importance to some sampled elements than to others. Weights are

calculated as the inverse of the probability of selection.
ACKNOWLEDGMENTS

x

ACKNOWLEDGMENTS

This report was prepared by the U.S. Environmental Protection Agency, Office of Water, Office of

Science and Technology. The EPA Work Assignment Manager for this document was Jeffrey Bigler,

who provided overall project coordination as well as technical direction. EPA was supported in the

development of this document by Tetra Tech, Inc., and EVS Environment Consultants, Inc. (EPA

Contract No. 68-C3-0374). Esther Peters of Tetra Tech was the contractor project manager, and

Steven Ellis of EVS was the subcontractor project manager. Mark Fly, Director of Human

Dimensions Research Lab, Department of Forestry, Wildlife, and Fisheries, University of Tennessee,

and Barbara Knuth, Co-Leader, Human Dimensions Research Unit, Department of Natural Resources,

Cornell University, served as expert consultants and assisted the contractors throughout the

development of the document.

Preparation of the final draft of this document was facilitated by the substantial efforts of several

reviewers at EPA Headquarters and the states, who provided technical information, reviews, and

recommendations. The EPA Headquarters reviewers were Dennis Borum, Helen Jacobs, and Robert

Cantilli. Representatives in all 50 states were sent copies of a previous draft, the “External/Peer

Review” version of the document. Participation in the review process does not imply concurrence

by these individuals with all concepts and methods described in this document. Representatives of

state agencies who provided comments on the earlier draft were Margy Gassel, California; Richard

Greene, Delaware; Shannon Winsness, Georgia; Maura Mack, Idaho; Deirdre Murphy, Maryland;

Montressa Jo Elder, Oklahoma; Glen Patrick, Washington; and Jim Amrhein, Wisconsin. These

reviewers’ comments were addressed, and the subsequent final draft was sent out for independent peer

review to the following experts in survey research and/or fish consumption surveys: Patrick C. West,

Associate Professor of Environmental Sociology, University of Michigan; G.P. Patil, Center for

Statistical Ecology and Environmental Statistics, The Pennsylvania State University; and Ellen M.

Werner, Mel Kollander, and Lorraine Porcellini, Institute for Survey Research, Temple University.
EXECUTIVE SUMMARY

ES-1

EXECUTIVE SUMMARY

Concern over potential human health risks associated with chemically contaminated fish and wildlife

has led many states to issue consumption advisories and bans in an effort to limit exposures to certain

organic compounds and metals that can become concentrated in the tissues of these organisms.

However, the processes and procedures by which states issue consumption advisories and bans have

varied. The U.S. Environmental Protection Agency (EPA) has developed a series of four documents

designed to provide guidance to state, local, regional, and tribal environmental health officials who

are responsible for issuing consumption advisories for noncommercially caught fish and shellfish.

The documents are meant only to provide guidance and do not constitute a regulatory requirement.

The documents are Guidance for Assessing Chemical Contamination Data for Use in Fish Advisories,

Volume 1: Fish Sampling and Analysis (released in 1993 and revised in 1995), Volume 2: Risk

Assessment and Fish Consumption Limits (released in 1994 and revised in 1997), Volume 3: Risk

Management (released in 1996), and Volume 4: Risk Communication (released in 1995). The current

document provides additional guidance on methods for obtaining consumption rate data for use in

characterizing exposure in a population when estimating potential risks and determining whether a

consumption advisory is warranted to limit exposure to contaminants in fish (a term that includes

shellfish for the purposes of this document) and wildlife. Consumption rate data are also useful to

states that are in the process of developing or modifying water quality standards.

The purpose of this document is to provide explicit instructions for selecting a survey approach and

designing a survey to obtain consumption rate information. A statistician should also be consulted

to provide advice on the specific sampling and statistical analysis considerations for each fish

consumption rate assessment project. The survey methods presented in this document may be used

by regional, state, tribal, or local agencies to obtain information on the consumption of

noncommercially obtained fish and wildlife. This information can then be used to estimate risks to

persons who could consume organisms that might contain bioaccumulative and potentially dangerous

levels of toxicants, and to develop consumption advisories and water quality standards to protect

human health. Such surveys can also provide demographic information about a population for which

advisories are issued, which might assist in the communication of risks and advisory

recommendations.

The primary objectives of this document are as follows:

• Emphasize the importance of survey objectives in selecting a survey approach and

designing the survey.

• Provide selection criteria for choosing among the various survey approaches.

• Critically evaluate key components in survey design and methods, including question

development, statistical analysis, quality assurance/quality control, and data

interpretation.

Section 1 provides an overview on the history of consumption advisories, the purpose and objectives

of this document, the relationship of this document to other guidance documents, and the organization

of this document. Section 2 presents a discussion of the development of the underlying objectives

for conducting a survey and summarizes the factors that should be considered when articulating
EXECUTIVE SUMMARY

ES-2

survey objectives. Survey objectives should reflect the purpose for which the data will be used.

Because each survey method has unique biases, the specific survey objectives will dictate how the

survey is conducted. For example, if the target population and/or waterbody is relatively small,

surveys will most likely be conducted at access sites rather than by means of mail or telephone

surveys because the latter type of survey is unlikely to capture enough respondents in the target

population for a statistically valid estimate unless they have been specifically identified and their

addresses or telephone numbers are known. Several key factors or variables can influence the choice

or articulation of an objective. These factors include, but are not limited to, types of fish or wildlife

being consumed, geographic location, population of concern, associated behavior, timing,

accuracy/uncertainty, type of decision to be made, and adherence to advisories.

The survey objectives will also help in designing the survey instrument, commonly called a

questionnaire. Information collected in the survey can be placed in one of four categories:

(1) physical and sociodemographic characteristics of fishers and hunters, (2) fishing and hunting

activities and behavior, (3) preparation and consumption patterns, and (4) consumption advisory

awareness, knowledge, attitudes, and beliefs. Each question in the survey instrument should be

designed so that it addresses one information need.

Section 3 reviews the various consumption assessment approaches included in this document and

presents selection criteria to be used in choosing from among the different approaches (i.e., telephone

survey, mail survey, diary, personal interview, and creel survey). The selection of a consumption

survey approach or approaches should be based on carefully assessing each approach in light of the

stated objectives for conducting the survey. Key considerations include the target population or

subpopulations of concern, the degree of accuracy required from the survey results, the time frame

in which the survey information is needed, human and financial resources available to conduct the

survey and analyze the data, and the characteristics of the fish or wildlife populations being evaluated

and their harvesting. 

In Section 4, instrument and study design considerations for each of the survey approaches are

discussed. Many issues are common to all five survey approaches, including issues pertaining to

questionnaire design (question structure, wording, and order), statistical analysis, data interpretation,

and quality control. The selection criteria that can be used to differentiate the survey approaches can

be divided into the following five categories:

• Target population/subpopulation

• Accuracy

• Time frame

• Resources

• Harvest characteristics

This document compares the five survey approaches based on criteria within the five categories listed

above. Often more than one survey approach may provide the required information. In such cases,

the selection of an approach should be based on other considerations such as personal preference, past

experience, available resources (funds and personnel), or consistency with other local, regional, or

national surveys. This last factor is particularly important if the purpose of the survey is to provide

data for comparison with the results of another survey.
EXECUTIVE SUMMARY

ES-3

EPA welcomes your suggestions and comments. A major goal of this guidance document series is

to provide a clear and usable summary of critical information necessary to make informed decisions

regarding the development of consumption advisories and water quality standards. EPA hopes this

document will be a useful adjunct to the resources used by the states, local governments, and tribal

bodies in making decisions regarding the development of consumption advisories and water quality

standards in their jurisdictions.
1. INTRODUCTION

1-1

SECTION 1

INTRODUCTION

1.1 Historical Perspective

Concern over potential human health risks associated with chemically contaminated fish, shellfish,

and other organisms that feed on fish and shellfish has led many states to issue consumption

advisories and bans in an effort to limit exposures to certain organic compounds and metals that may

become concentrated in the tissues of these organisms. However, the processes and procedures by

which states develop consumption surveys and use the survey results as a basis for issuing advisories

or bans and water quality standards have varied. In an effort to evaluate the fish consumption

advisory process in the states, the U.S. Environmental Protection Agency (EPA) provided a grant for

the American Fisheries Society (AFS) to conduct a survey of state fish consumption advisory

practices (Cunningham et al., 1990). In the survey, state representatives were asked to describe their

fish consumption advisory process and procedures, to identify state concerns related to the advisory

process, and to recommend actions that could be undertaken by the federal government to improve

the effectiveness of the consumption advisories.

To follow up on the state recommendations for federal action, EPA invited officials from state

agencies to attend a Federal-State Forum on August 30, 1990, in Pittsburgh, Pennsylvania.

Representatives of agencies from 27 states and the District of Columbia, as well as several federal

agencies, including EPA, the Food and Drug Administration (FDA), the National Oceanic and

Atmospheric Administration (NOAA), the U.S. Fish and Wildlife Service (FWS), the Tennessee

Valley Authority (TVA), and the Agency for Toxic Substances and Disease Registry (ATSDR) were

present. The agenda for the forum contained a list of the federal action items identified in the AFS

survey. Participants were asked to rank proposed federal action items as short- or long-term priorities

and to recommend other action items not previously identified in the survey. Each participant was

also asked to submit the three action items most important to his or her program. The second most

frequently requested short-term action item contributed by forum participants was to conduct surveys

or studies to assess the fish consumption rates of various subpopulations in different regions of the

country (Southerland, 1991). Fish consumption rate data are essential in developing water quality

standards, and they also play an integral role in developing advisories and bans.

EPA recognized that studies of fish consumption patterns should be conducted to update available

information and to focus on geographical or cultural populations potentially at a high risk. For

humans, a technique that has often been used to obtain consumption pattern data is to conduct a

survey in which respondents are asked to estimate how much fish tissue they consume and the

frequency at which it is consumed or to record actual consumption information on a daily basis. To

address this need, EPA implemented a three-phase approach for assisting the states in estimating fish

tissue consumption rates in potential high-risk populations. This approach included the following

steps:

• Review and critically evaluate existing fish tissue consumption rate survey methods and

determine their applicability for estimating consumption rates in recreational and

subsistence fishing populations.
1. INTRODUCTION

1-2

• Conduct a workshop for the states presenting the results of the review and critical

evaluation of fish tissue consumption survey methods.

• Provide direct support to the states in conducting fish tissue consumption surveys

targeting recreational and subsistence fishers.

A 1992 document was prepared to meet the first step in this process (U.S. EPA, 1992). Existing

literature concerning fish tissue consumption was reviewed, and selected surveys were evaluated to

identify approaches (recall vs. diary vs. creel) and methods for survey design and analysis. The

purpose of the document was to assess the attributes and shortcomings of these approaches and to

explore the underlying methods involved in designing and conducting fish consumption surveys. The

report also discussed the types of questions that need to be answered in order to understand fish

consumption patterns in high-risk populations. It did not, however, recommend a specific protocol

for use by the states, nor did it provide selection criteria for states to use to develop surveys.

1.2 Purpose

The purpose of this document is to provide more explicit instructions than those provided in the 1992

EPA document for selecting a survey method and designing a survey to obtain consumption rate

information. Data on exposure and determination of the average daily intake are necessary to assess

risks posed to consumers of fish and shellfish (U.S. EPA, 1997a). Shellfish, including crabs, lobsters,

shrimp, crayfish, mussels, and oysters, have also been included in surveys examining consumption

rates, and consumption advisories and bans have been developed for these organisms in some

localities. In addition to concerns about consumption of contaminated fish and shellfish, recent

studies have indicated that persons who eat wildlife (e.g., frogs, turtles, and waterfowl) that live in

polluted areas and/or consume contaminated fish and shellfish might also be exposed to potentially

toxic levels of bioaccumulative chemical contaminants. For example, consumption advisories have

been issued for snapping turtles and other turtles in New York, Arizona, Massachusetts, and

Minnesota; New York has issued consumption advisories for mergansers because of high levels of

chlordane, DDT, mirex, and polychlorinated biphenyls found in the tissues of these ducks (U.S. EPA,

1996b). 

Consumption patterns, including the types and amounts of fish and wildlife and frequencies of meals

eaten from these organisms and the preparation methods used, can also vary greatly within

populations because of differences in age or gender. They can differ between populations because

of differences in cultural practices and/or socioeconomic status. The survey methods presented in this

document may be used by regional, state, tribal, or local agencies to obtain information on the

consumption of noncommercially obtained fish (a term that includes shellfish for the purposes of this

document) and wildlife (a term that includes other aquatic and terrestrial animals and birds for the

purposes of this document). This information can then be used to determine whether the amounts of

fish and wildlife being eaten are safe in relation to possible chemical contamination, to estimate risks

to persons who could consume fish and wildlife that might contain bioaccumulative and potentially

dangerous levels of toxicants, and to develop consumption advisories and water quality standards to

protect human health. Information presented in this document should also prove valuable in

evaluating the type and quality of data obtained in surveys conducted by others to determine whether

they are suitable for use in planned risk assessments. 
1. INTRODUCTION

1-3

1.3 Objectives

The primary objectives of this document are as follows:

• Emphasize the importance of survey objectives in selecting a survey approach and

designing the survey.

• Provide selection criteria for choosing among the various survey approaches.

• Critically evaluate key components in survey design and methods, including question

development, statistical analysis, quality assurance and quality control, and data

interpretation.

1.4 Relationship of Manual to Other Guidance Documents

To address concerns raised by the survey of state fish advisory practices (Cunningham et al., 1990),

EPA developed a series of four documents designed to provide guidance to state, local, regional, and

tribal environmental health officials who are responsible for issuing consumption advisories for

noncommercially caught fish and shellfish. The documents are meant only to provide guidance and

do not constitute a regulatory requirement. The documents are Guidance for Assessing Chemical

Contamination Data for Use in Fish Advisories, Volume 1: Fish Sampling and Analysis (released in

1993 and revised in 1995), Volume 2: Risk Assessment and Fish Consumption Limits (released in

1994 and revised in 1997), Volume 3: Risk Management (released in 1996), and Volume 4: Risk

Communication (released in 1995). EPA recommends that the four volumes of this guidance series

be used together since no one volume provides all the necessary information to make decisions

regarding the issuance of consumption advisories. The current volume provides additional guidance

on methods for obtaining consumption rate data for use in developing the exposure assessment to

estimate potential risks and to determine whether a consumption advisory is warranted to limit

exposure to contaminants in fish and wildlife. The reader is directed to consult additional references

provided in this document for more detailed information on designing, conducting, and analyzing

consumption surveys. In addition, reviews of consumption surveys, compilations of fish and shellfish

consumption rate data, and detailed discussions of issues pertaining to consumption surveys and the

use of these data in risk assessments are available in Gassel (1997) and U.S. EPA (1997a). 

1.5 Organization of This Manual

Following this introduction, Section 2 presents a discussion of potential survey objectives and

summarizes the factors that should be considered when articulating survey objectives. Section 3

reviews the various consumption assessment approaches included in this document and presents

selection criteria to be used in choosing between the different approaches. In Section 4, instrument

and study design considerations for each of the survey approaches are discussed. The document is

summarized in Section 5, and the literature cited is given in the references section. Appendix A

provides a summary in table form of previous consumption surveys. Appendix B presents example

survey instruments for the five survey approaches discussed in this document. The reader should

note that these survey instruments are provided as examples only and their inclusion in this document

does not imply endorsement by EPA.
2. SURVEY OBJECTIVES AND INFORMATION NEEDS

2-1

SECTION 2

SURVEY OBJECTIVES AND INFORMATION NEEDS

2.1 Overview

Consumption rates for fish and wildlife differ throughout the country and for specific subpopulations

(see, for instance, Hu, 1985; Allen et al., 1996; U.S. EPA, 1996a; Gassel, 1997; U.S. EPA, 1997a).

Several recent studies have attempted to develop consumption rate estimates for high-risk populations.

The four steps in the design and development of a consumption survey are as follows:

1. Identification of the survey objectives.

2. Preparation of a sample design and analysis plan, which includes

• identification of the target population(s) and selection of the sampling strategy for the survey

population(s)

• identification of the specific data to be gained from the survey

• the analytical/statistical methods to be used once the data are collected

3. Selection of the survey approach to be used to obtain the data.

4. Design of the survey instrument(s).

This section describes the objectives and information needs of surveys or censuses targeting populations

of concern. 

2.2 Definition of Survey Objectives

Developing the consumption survey objectives is a critical step in designing the survey. An objective

is “something toward which effort is directed” (Merriam-Webster, 1993). Objectives can flow from a

problem that has been identified (high levels of polychlorinated biphenyls [PCBs] in sport fish) or a

question that has been posed (Will eating the fish in this river, or wildlife in this area, make people

sick?). The reasons for conducting the survey (e.g., the need to know whether fishers at Lake X eat

catfish and how much is consumed) should suggest some or all of the appropriate objectives. For

example, if there is a need for fish consumption data for recreational fishers at a contaminated

waterbody, three specific objectives would be the following: 

1. Identify the population of fishers who catch and eat fish from the waterbody.

2. Obtain information regarding fishing activities at the waterbody for the target population.

3. Determine the fish consumption practices for the target population.
2. SURVEY OBJECTIVES AND INFORMATION NEEDS

2-2

If the target population is relatively small and it is desirable and feasible to survey the entire population

(i.e., take a census), then the results obtained will be observations of the population parameters. The

more typical situation, however, is when a subset of the target population is sampled at random; the

results obtained are sample statistics which, if obtained correctly, are expected to be good

approximations of the population parameters. Census estimates have less error than sample estimates

because they are subject only to the reliability, validity, and measurement error involved in the survey

response (see discussion of Accuracy in Section 3.3.2). The sample estimates are subject to the same

types of error as censuses, but also to sample selection bias and sampling error. 

Survey objectives should reflect the purpose for which the data will be used, one of the reasons for

conducting the survey. For example, in cases where health effects from fish or wildlife consumption are

suspected, an advisory might be implemented to reduce adverse effects or water quality standards might

be established and enforced. Development of an advisory may proceed without site-specific

consumption information (see procedures in U.S. EPA, 1997a) based on contaminant levels in tissue and

a valid EPA risk value (reference dose or cancer slope factor), chronic no-observed-adverse-effect level

(NOAEL), or lowest-observed-adverse-effect level (LOAEL) and an estimated overall average

consumption rate to characterize risk. However, determination of actual consumption levels can improve

the accuracy of the risk estimate. Subsistence fishers or hunters, who rely on noncommercially obtained

fish or wildlife for a major portion of the protein in their diets, might be more at risk than those who fish

or hunt primarily for recreation or sport and thus eat less fish and wildlife. Those who fish or hunt less

frequently but rely on potentially contaminated sources of fish and wildlife from friends or neighbors for

most of their protein needs might be more at risk. Children, women of child-bearing age, and older

persons might be more at risk from exposure to certain contaminants than adult middle-aged males.

Another potential use for fish consumption data is in state ambient water quality standards programs.

For these programs, local fish consumption data are preferred over national default rates.

Consumption rate information is also used in risk management decisions regarding the allocation of

resources and implementation of various public health protection strategies related to consumption of

contaminated fish and wildlife (U.S. EPA, 1997a). Information on methods used by fishers or hunters

to prepare their catch and the extent to which a particular contaminant concentration is likely to be

decreased by trimming and skinning or broiling and frying, for example, are needed to develop dose

modification factors to change the contaminant concentration and the resulting exposure estimate used

as a parameter in the risk equations, for the development of fish advisories, and for risk communication

activities (U.S. EPA, 1997a). Thus, different final uses of the data, in addition to the underlying research

objectives, will also influence the development of the survey objectives and the design and

implementation of the survey.

The objectives for the process of obtaining consumption rate data might be expressed as follows:

• Determine the amount and frequency of noncommercially caught fish consumed by

individual members of households in a target population.

• Determine the amount and frequency of consumption of fish from River X for children.

• Determine the amount and frequency of consumption of frogs caught at Lake Y during the

summer.
2. SURVEY OBJECTIVES AND INFORMATION NEEDS

2-3

• Determine the amount and frequency of consumption of shark, tuna, and swordfish either

caught by the fisher or obtained from other sources.

• Determine the amount and frequency of consumption of whole fish versus fish muscle for

members of different ethnic populations and socioeconomic sub-populations.

• Determine the amount and frequency of consumption of ducks from regions with several

waterbodies containing similar known toxicants. 

Different survey objectives will be needed to address different information needs. Consumption rate data

might be required for developing an advisory at a waterbody based on contaminants in all fish, or just

in certain species of fish. Alternatively, data might be used to develop an advisory to protect human

health from exposure to a specific contaminant from a variety of noncommercially caught fish and

wildlife, and other sources. An advisory might also be developed to guide people in preparing fish in

a manner that removes contaminants and thus reduces exposure.

Because each survey approach has unique biases, the specific survey objectives will dictate how the

survey is conducted. For example, if the target population and/or waterbody is relatively small, surveys

will most likely be conducted at access sites rather than through mail or telephone surveys because the

latter type of survey is unlikely to capture enough respondents in a given population for a statistically

valid estimate unless the target population has been previously identified so that their addresses or

telephone numbers are known. A large number of data points might be needed to minimize the

uncertainty of the fish consumption estimates so as to improve the estimate of risks to the targeted

population. 

The survey objectives will also help in designing the survey instrument (commonly called a

questionnaire). The information to be collected is targeted to address the objectives. One question might

provide data needed for one or more objectives; one objective might require several questions to collect

the data. The survey objectives can also guide the development of the types of questions to be asked and

analyses of the data that might be performed to obtain specific results (e.g., estimated age distribution

of consumers, estimated number of fish dishes [or fish meals] consumed per person per week [or per

month], and estimated age distribution of persons eating more than 10 g per day). The survey objectives

thus serve as a planning tool to ensure that the required information is collected.

Several key factors or variables can influence the choice or articulation of an objective. These factors

include, but are not limited to, type of consumption, geographic location, population of concern,

associated behavior, timing, accuracy/uncertainty, type of decision to be made, adherence to advisories,

and type of adverse health outcomes associated with the contaminants at a site.

The type of consumption that might be targeted in a particular survey could be total (all fish consumed

from all sources, caught or bought, noncommercial or commercial), recreational only (fish consumed only

when caught for sport), recreational as a percent of total fish consumption, subsistence only (fish

consumed year-round as the primary protein source), or species-specific fish consumption (largemouth

bass only, sharks only, snapping turtles only, all bottom-feeding species only), for example.

The geographic location to be investigated is also important, both for fishing and hunting activity and

for consumers of the fish and wildlife caught. Determining the consumption of bluefish (a saltwater fish)

among fishers in the Great Lakes region might be technically feasible, but it would not provide
2. SURVEY OBJECTIVES AND INFORMATION NEEDS

2-4

information useful in developing an advisory for Lake Michigan, which would need to be based on the

consumption of contaminated lake trout, for instance.

Identification of the population of concern is an important objective that should be articulated during the

early stages of the survey design. Surveys can be designed to identify groups that might be at greater

risk of exposure to contaminants in fish and wildlife due to higher consumption rates. For example,

West et al. (1989) described variations in fish consumption in communities in Michigan by ethnicity,

income, and length of residence. This survey determined that, in general, African Americans and Native

Americans ate more fish than Caucasians; individuals with lower incomes ate more fish than individuals

with higher incomes; and older individuals ate more fish than younger individuals. Surveys also can be

designed to target especially susceptible subpopulations. For pregnant and nursing women, women

planning to have children, small children, people with preexisting health problems, and older persons,

the risk from consuming contaminated fish might be greater than for healthy men and healthy nonreproducing women (U. S. EPA, 1997a). Exposure to some contaminants is of particular concern during

prenatal or postnatal development because of the rapid tissue growth and development that infants and

children undergo during those periods (NAS, 1993). Persons with preexisting health problems might

be particularly susceptible to contaminants that interact with their medications or are toxic to organs

already affected by disease (U.S. EPA, 1997a). Older persons might be at greater risk to contaminants

because the aging process can increase the retention of toxic chemicals through a variety of

morphological, organ, and cellular changes (e.g., West et al., 1997). Additional information on the

identification and selection of populations of concern is provided in U.S. EPA (1997a).

Timing is an essential consideration for obtaining consumption rate data. How soon will information

from the study be needed? Over what seasons are the data needed, or is the entire year being considered?

Fishing activity might be undertaken by the majority of fishers only during the summer, and duck hunting

is usually limited to specific time periods; however, the popularity of ice fishing has grown in some areas

of the northern United States. In addition, fish or wildlife caught in one season might be preserved (e.g.,

smoked or frozen) and consumed later, indicating that exposure to tissue contaminants might be equally

important year-round.

Another important concept that can influence the development of the objectives is the required accuracy.

If only a “ballpark” figure is needed for issuing advice, identification of consumption rates for specific

populations or sites might be unnecessary. However, if regulatory or legal challenges to issuance of an

advisory, closure, or water quality standards are anticipated, a highly accurate, legally defensible

consumption rate might be required, indicating a need to address more objectives or very detailed

objectives in the survey. 

The type of decision to be made based on the consumption data can drive the survey process; for

example, risk assessment (predictive/protective) versus diet/health relationships (empirical). Will data

on actual consumption be used in relation to observed health effects, or is potential consumption

information (e.g., in the absence of contaminants) desired to assist in cleaning up a contaminated site so

that fishing or hunting activity can be restored? For whom will the advice be constructed—the general

public or a specific population? 

In some cases, consumption data are desired to evaluate adherence to advisories, i.e., the success of

existing advisory messages recommending certain consumption behavior. The objective of determining

consumption advisory effectiveness should then be included in the list of survey objectives.
2. SURVEY OBJECTIVES AND INFORMATION NEEDS

2-5

The responsibilities and the ethics of conducting the survey should also be considered. Of particular

importance are the requirements for reporting back to the population surveyed so that respondents can

learn the results. In most instances, approval by a human subjects research review board is needed prior

to implementing the survey even when the person to be interviewed is clearly anonymous.

Confidentiality and informed consent are important in any survey process where personal data are

collected and the participant can be identified, as in a personal interview, a listed telephone sample, or

a list of license holders.

2.3 Information Needs

In addition to the overall purpose and objectives of a consumption study, the need for information about

specific aspects of consumption or characteristics of fish and wildlife consumers should be considered.

The extent to which these factors are important or to which information is needed to meet the objectives

of the study will influence what survey approach is selected. These factors include:

• Physical and sociodemographic characteristics of fishers and hunters and/or fish and

wildlife consumers.

• Fishing and hunting activities and behavior.

• Preparation and consumption patterns.

• Consumption advisory awareness, knowledge, attitudes, and beliefs.

Specific information needs within these general categories are given in Table 1. The list was compiled

from recent fishing/shellfishing surveys and comments from representatives of federal and state agencies

and other organizations.

The most important data needed to develop an exposure assessment are the characteristics of the

population that might be exposed and the exposure or consumption rate, usually expressed in grams per

individual per day (g/day) or grams per kilogram of body weight per day (g/kg/day). These information

needs are marked with a diamond in Table 1. Certain population subgroups are known to be more

susceptible to toxic effects from chemical contaminants (U.S. EPA, 1997a). Of particular concern are

children, women of childbearing age, and elderly persons.

The survey objectives might focus on one or more subgroups for which development of a fish

consumption advisory might be warranted, depending on the possible chemical contaminants to which

consumers might be exposed. The information might be obtained by surveying members of that

subgroup only, or by surveying whole households as sample units and later selecting subgroup data for

separate analysis. The subgroups might be identified by asking whether the respondent (or each

household member) is male or female, his or her actual age or age category, or other designation. The

exposure assessment will also require data on the amount of contaminant found in the fish, shellfish, or

wildlife tissue of concern. The reader is referred to U.S. EPA (1995, 1997a) for further guidance in

obtaining such data.
2. SURVEY OBJECTIVES AND INFORMATION NEEDS

2-6

Table 1. Potential Information Requirements for Fish and Wildlife Consumption Surveysa

Physical and Sociodemographic Characteristics of Fishers/Hunters and/or Consumers:

Ç Characteristics of fisher or hunter and each household member (ethnicity, gender, date of

birth, height, weight) 

Ç Pregnancy/lactation status of women in the household

Ç Physical disabilities or medical conditions of each household member

Ç Number and type of permanent and temporary household members (e.g., child or adult,

fish/wildlife consumer or nonconsumer, resident or migrant)

• Occupation/employment status

• Income level

• Education level

• Language spoken at home

• City of residence

Fishing and Hunting Activities and Behavior:

• Location(s) of fishing or hunting activities (specific sites, type of waterbody)

• Distance(s) of fishing or hunting activities from principal residence

• Seasonal and temporal distribution of fishing or hunting activities (total number of days per

season, which months of the year, for each location)

• Fishing or hunting effort (hours/outing, hours/day, outings/month, days/month)

• Purpose for fishing or hunting (consumption, sport only: catch and release, etc.)

• Mode of fishing or hunting (e.g., nets, traps, hook and line; pier, shore, private boat,

charter boat, scuba)

• Type of animal caught (general category such as bottomfish, flatfish, turtle; or identified to

species or group of species)

• Numbers of animals by species caught per outing

• Size ranges of animals caught (minimum and maximum weights and lengths by species)

• How the animals were disposed of (released, consumed by household, sold, given away)

• How long involved in fishing or hunting activities and consuming self-caught animals (new

to sport or years)

Preparation and Consumption Patterns:

Ç Amounts (raw wet weight or cooked weight) of wild-caught fish or wildlife tissue eaten per

meal/day/week/month for each person in household (visual cues are helpful to improve

the accuracy of portion size estimates)

Ç Quantity of fish, or other aquatic organisms, waterfowl, or wildlife that might have eaten

fish from the same sites, consumed during a specified time period

Ç Geographic and seasonal variations in consumption

Ç Parts of animal consumed (may vary with the species)

• Parts of animal used for cooking but not ingested (e.g., boiling of bones or fish heads)

Ç How the animals were prepared for eating (e.g., skinned, fillet, steak, shucked)

Ç How the animals were cooked (e.g., baked, fried, steamed)

Ç Special cultural/ethnic practices in fish or wildlife consumption and preservation

• Consumption of fish or wildlife purchased in supermarkets, fish markets, or roadside

stands; purchased at the dock; or obtained by bartering (amounts, number of meals,

frequency)

• Whether fish or wildlife were frozen or preserved and eaten throughout the year, or eaten

only when fresh
2. SURVEY OBJECTIVES AND INFORMATION NEEDS

2-7

Table 1. (continued)

Preparation and Consumption Patterns (continued):

• Participation in food assistance program

• Source of home water supply

• Risk behaviors (smoking, drinking)

• The level of consumption that would be desired in the absence of contaminants

• If advisory has resulted in reduced consumption of fish or wildlife, what has replaced that

protein/food source in the diet?

Consumption Advisory Awareness, Knowledge, Attitudes, and Beliefs:

• Has the fisher or hunter heard or read from any source (including interpersonal

communication or mass media sources such as announced fishing bans or posted

notices) of the possible contamination of fish or wildlife by chemical or biologic agents in

areas where currently fishing/hunting or where planning to fish/hunt?

• If yes, how has it affected his/her fishing or hunting activities, meat preparation methods,

or consumption patterns?

• What, if anything, would stop the fisher or hunter from eating the animal that he or she has

caught? Is the fisher or hunter in a situation that precludes him or her from finding other

food sources (i.e., is he or she subsistence fishing and hunting?)

• Did the fisher or hunter ever get sick from eating self-caught/self-prepared fish or wildlife?

• Did the fisher or hunter ever observe any abnormalities, internal or external, in captured

animals? If so, were the animals consumed, thrown out, or given away?

• If aware of the advisory, does the fisher or hunter inform the recipient of the gift meat

about the advisory?

• Does the fisher or hunter feel that the health risks indicated in the advisory are relevant to

him or her? If no, why not? If so, why does he or she continue to consume the fish or

wildlife? 

• Does the respondent know the correct advisory content?

• To what extent does the respondent believe the advisory content?

• How important does the respondent feel the advisory is to him or her or other members of

the household?

Information requirements marked with a diamond are of primary importance in determining risk. a 

One of the fundamental issues surrounding the collection of information is identifying the sampling unit

and the methods by which that sampling unit will be surveyed. In fish consumption surveys, the

sampling unit is typically the individual consumer. When sampling (rather than taking a census of) the

population, it would be inappropriate to consider all members of a household in a particular subgroup

(e.g., children) as independent observations of the population because of obvious “household effects.”

If each individual in every household were considered an independent case, the consumption estimates

for the population would be skewed toward those of larger families. If the individual is the sampling

unit, the appropriate design might be to randomly select a household and then randomly select a

household member within the target population. The resulting estimate would represent the average

consumption rate for the target population. Alternatively, if the sampling unit is the household, all

members of the household should be questioned, either individually or perhaps by proxy with the primary

food preparer as the single respondent speaking for all members of the household. The complete

information for a household could then be summarized to produce a single estimate for each subgroup

within the selected household. For example, this single estimate might be the mean or the maximum

consumption for household members in the target population. This household estimate would represent

the average or maximum household consumption rate for the target population. Proxy respondents may

be necessary when the target population is an older person or a child; in these situations, proxy
2. SURVEY OBJECTIVES AND INFORMATION NEEDS

2-8

respondents may actually provide more accurate responses to survey questions regarding fish

consumption and preparation information. When using proxy respondents, the primary concern is to

ensure that the target sampling unit is sampled only once and that all sampling units in the population

have an equal probability of being sampled.

U.S. EPA (1992) noted that fish consumption rates can vary widely in the human population. Different

rates might be obtained for infrequent fish consumers, sport fishers, subsistence fishers, and others who

eat fish frequently or for those who eat wildlife. Also, the rate itself might represent one of several

different possible summary statistics (e.g., mean, median, 95 percent upper confidence limit) of the entire

distribution. Several authors (e.g., West et al., 1993; Gassel, 1997) have noted that a single point

estimate is inadequate to represent consumption rates for a population because of the inherent variability

in the consuming populations; thus the entire distribution or several points in the distribution could be

used to describe the consumption rate or to protect a larger percentage of the overall consuming

population. Various subgroups within these categories might also have different consumption rates

(adults vs. children, children of different ages or sizes, elderly versus middle-aged). Since consumption

rates will “have a significant impact on the risk estimations and on the selection of fish consumption

limits” (U.S. EPA, 1992), it is important to consider carefully how the consumption rate will be

determined from the questions asked. For example, consumption rates will be calculated from speciesspecific estimates of the frequency of fish consumption (“1 meal per week from May through July”),

portion size, and preparation techniques (“approximately half-pound fillet, generally broiled”). These

responses could result in a consumption rate estimate of 225 grams per week for 3 months. Insufficient

delineation on the timing or details of consumption patterns will result in poor estimates of the

consumption rate and consequently inaccurate estimates of risk. The method to be used will also depend

on the survey method selected (see Section 3). See Section 4 for more details on how these estimates

can be obtained for the different survey methods, as well as a discussion of the uncertainties associated

with consumption estimates.

The type and level of detail for the data to be collected will depend on the stated objectives for the survey

and the statistical methods that will be used to meet those objectives. Data (e.g., consumption

information and fishing effort) may be collected as continuous or categorical data types. A survey

question may be constructed to provide categorical answers from which the respondent must choose

(e.g., “none ,” “a few meals ,” “some meals ,” “most meals ,” or “all meals” in response to the question

“How many meals are prepared using method X?”); alternatively, the question may be phrased to force

the respondent to come up with his or her own estimate (“How many meals per month are prepared using

method X?”). The analytical implications associated with these two approaches should be discussed with

an experienced survey researcher and/or statistician before constructing the survey questions. It should

be noted that since the use of categorical response choices can affect the outcome by suggesting

responses or altering memories, the use of categories should be employed judiciously (Wentland and

Smith, 1993).

2.4 Summary

Reasons for conducting a consumption survey can be varied, but it is important to clearly define why the

survey is being conducted and what information can be derived from the survey. This is important so that

those who are using a survey instrument, as well as those participating in the survey, understand what

can and will be done with the information obtained. Consumption survey objectives should be developed

very early in the planning process. The nature of the objectives will dictate what survey method(s) can

be used effectively. Information collected in the survey can be placed in one of four categories (Table
2. SURVEY OBJECTIVES AND INFORMATION NEEDS

2-9

1): (1) physical and sociodemographic characteristics of fishers/hunters and/or consumers, (2) fishing

and hunting activities and behavior, (3) preparation and consumption patterns, and (4) consumption

advisory awareness, knowledge, attitudes, and beliefs. Table 2 presents an example of the development

of a survey from an examination of the problem and selection of an approach to production and analysis

of the results.

Table 2. Example Development of a Survey

Problem: Catfish in Lake A contain high levels of chemical X, a known

carcinogen.

Purpose: Determine whether children would be at increased risk of developing

cancer as a result of eating catfish from Lake A.

Objectives: Determine whether children are eating catfish caught in Lake A.

Determine how much catfish tissue from Lake A children eat.

Survey Method: Personal interviews at Lake A.a

Instrument Questions: Do you catch catfish from Lake A? 

(IF YES) Do you release the catfish or keep them?

(KEEP) How many catfish do you keep per year?

(NUMBER)

How many children do you have in your household, if any?

(NUMBER)

(IF > 0) Do any of the children eat catfish?

(IF YES)

(List each child who eats catfish by age and gender.)

What is the age of each child who eats catfish?

What is the gender of each child who eats catfish?

(For each child listed)

(LIST) How often does (_______) eat catfish, if at all? (per week,

month, etc.)

(IF > 0) How much catfish does (________) eat per meal? (visual

cues)

How is the catfish prepared?

Analysis and Results: Percent of population surveyed that have children in household.

Percent of children in household who eat catfish.

Frequency and amount of catfish consumption by children.

As with all survey instruments, the researcher should be concerned about sampling, recall period, and accuracy, and whether a

the respondent on site at the lake can best answer questions about preparation and portion sizes. This instrument is subject

to the weaknesses described in this document; it should be refined whenever possible to ensure that its design supports the

study objectives and that it maximizes the use of available resources.
3. SURVEY APPROACHES AND SELECTION CRITERIA

3-1

SECTION 3

SURVEY APPROACHES AND SELECTION CRITERIA

3.1 Overview

Currently, most states do not have sufficient data available to calculate local consumption rates or to

identify special populations at risk. As a result, a variety of methods are used for estimating

consumption rates when calculating risk associated with the consumption of chemically contaminated

fish tissue (U.S. EPA, 1989). As states increase their focus on this type of risk assessment, the need

for site-specific fish—and now wildlife—consumption surveys has become more apparent. This

section briefly summarizes some of the available approaches and provides selection criteria that can

be used to choose among the approaches. The discussion of survey approaches applies to both

population censuses and the surveying of a population sample (e.g., a telephone survey could be

applied to both a census and a sample survey).

3.2 Types of Surveys

EPA (U.S. EPA, 1992) has identified five different approaches to conducting surveys of subsistence

and recreational fishers and hunters—telephone survey, mail survey, diary, personal interview, and

creel survey. Some differences among these approaches include whether respondents must rely on

the recall of past or recent activities or behavior (telephone survey, mail survey, and personal

interview) versus a description of current or recent activities (creel survey, personal interview, and

diary) and whether the survey information is collected away from fishing or hunting locations

(telephone survey, mail survey, diary, and personal interview) or at the site of fishing and hunting

activity (creel survey, personal interview, and diary). These approaches are either self administered

(mail survey or diary) or administered by an interviewer. A self-administered questionnaire is one

in which the respondent marks or writes answers on a paper questionnaire from which answers are

later transferred to a database. Recent developments in software and use of the World Wide Web can

permit respondents to enter information directly into an Internet interface that permits transfer of

electronic data to a database. Those approaches administered by an interviewer can be either

computer-assisted or recorded on paper and later entered into a database. Each of the five survey

approaches is briefly summarized below. A more detailed discussion of each approach is presented

in Section 4. The reader should also consult the detailed information on surveys provided in books

and reports such as Salant and Dillman (1994) and Armstrong et al. (1994).

3.2.1 Telephone Survey

The telephone survey consists of telephoning selected respondents and asking them about current or

recent fishing or hunting trips and fish or wildlife consumption. The answers are recorded on

preprinted questionnaires or entered directly into a computer database, usually by interviewers

working from one central location under supervision.

3.2.2 Mail Survey

For a mail survey, a self-administered questionnaire regarding the recent or past fishing or hunting

activities and consumption of selected individuals is mailed to them. 
3. SURVEY APPROACHES AND SELECTION CRITERIA

3-2

3.2.3 Diary

The diary approach involves the use of diaries, logbooks, or catch cards, which are completed by

fishers or hunters, preferably at the end of a day’s fishing or hunting or at the time of consumption

of fish or wildlife. This approach differs from the questionnaire approaches in that there are typically

multiple entries, each of which consists of a smaller amount of information than is typically requested

in a mail or telephone questionnaire. Types of information recorded typically include number and

size of animals caught and by whom, fishing or hunting location, type of fish or wildlife eaten, size

of serving, preparation method (how it was cleaned and cooked), and who ate the fish or wildlife.

3.2.4 Personal Interview

Personal interviews can be conducted at known fishing or hunting sites, at the fisher’s or hunter’s

home, or at a centralized location (see, for example, CRITFC, 1994). In-home interviews ask about

recent fishing or hunting trips and fish or wildlife consumption. On-site interviews have the

flexibility to include questions about the current trip, as well as the respondent’s usual fish or wildlife

consumption. Respondents are asked a fixed set of questions, and the answers are recorded on

questionnaires or entered directly into a computer database.

3.2.5 Creel Survey

The creel survey is a specialized form of personal interview that takes place only at or near the fishing

site during or immediately after the fisher’s fishing trip. In addition to asking a specific set of

questions about fishing activity and fish consumption behavior, an attempt is usually made to identify

and/or measure fish in the fisher’s possession (the “creel”). The creel survey can be conducted at

access points (e.g., boat ramps, docks), along the shoreline, or on the water from a boat. Fish

consumption information obtained from the fishers is hypothetical in the sense that consumption has

not yet occurred.

3.3 Selection Criteria

The selection of which survey approach or approaches to use to gather information from fish and

wildlife consumers should be determined by carefully assessing each approach in light of the stated

objectives for conducting the survey. Key considerations include the target population or

subpopulation of concern, the degree of accuracy required from the survey results, the time frame in

which the survey information is needed, the human and financial resources available to conduct the

survey and analyze the survey data, and the characteristics of the fish or wildlife populations and their

harvest being evaluated.

Table 3 shows these five key considerations that influence the selection of an appropriate survey

approach, with specific selection criteria for each consideration that can be used to discriminate

among the survey approaches. In some cases, more than one survey approach might provide the

required information. In these cases, the selection of an approach should be based on other

considerations such as personal preference, past experience, or consistency with other local, regional,

or national surveys. The key considerations are discussed below separately.
3. SURVEY APPROACHES AND SELECTION CRITERIA

3-3

Table 3. Comparison of Five Fish and Wildlife Consumption Survey Approaches

Using Various Selection Criteria

Selection Criterion

Telephone Mail Personal

Survey Survey Diary Interview Creel Survey

I. Target Population/Subpopulation

Survey sample known prior to yes/no yes yes yes/no yes/no

conducting survey

a b c

Can be used where low literacy yes no no yes yes

rates might be encountered

II. Accuracyd

Reliability

Potential for response reliability moderate/ low/ low/ moderate/ moderate/

high moderate moderate high high

Validity

Validity of consumption low low/high moderate low/ moderate

estimates moderate

e

f

f

Validity of species identification low moderate moderate moderate/ high

highg

Bias

Potential to minimize recall bias moderate low/high moderate moderate/ not e

high applicable g

Potential to minimize prestige moderate low low moderate moderate

bias

Measurement error

Opportunity for respondent to moderate/ low low high high

ask for clarification high

Potential for respondent moderate moderate low high high

participation

III. Time Frame

Immediate data from respondent yes no no yes yes

IV. Resources

Interviewer burden moderate low low high high

Respondent burden low moderate high low low

Relative cost moderate low/ low high high

moderate

V. Harvest Characteristics

Many access points yes yes yes yes/no yes/no b h

High fishing or hunting pressure yes/no yes no yes yes/no i j

Large geographic area yes yes yes no no

Yes if phone numbers are obtained after the sample population has been preselected, no if random-digit a

dialing (RDD) or general directory frames are used, unless geographically delimited using 3-digit prefix.

No for interviews conducted at fishing or hunting access points, yes for off-site interviews. b
3. SURVEY APPROACHES AND SELECTION CRITERIA

3-4

Depends on ability to estimate total site usage using random sampling of all access points (e.g., using “bus c

route method,” aerial survey, or other methods; see Section 4.9.4, or Pollock et al., 1994 for more information

on these methods).

Given sufficient resources, all five survey approaches can generate accurate data. The descriptions given d

here are relative to each other and reflect the typical implementation of each approach.

Depends on recall method used -- six-month recall periods will have lower validity and higher recall bias than e

a 14-day rolling cohort approach (e.g., West et al., 1989; 1993).

On-site interviews result in valid catch estimates, but consumption estimates are hypothetical because they f

measure only the intent to consume (see Section 4.9.2). Off-site interviews result in catch and consumption

estimates with potentially low validity depending on the period of recall (see also footnote d).

Moderate for off-site interviews, high for on-site interviews. g

Yes for roving creel survey, no for access point survey. h

Yes for random telephone numbers, no for known telephone numbers. i

Yes for access point survey, no for roving creel survey. j

3.3.1 Target Population of Concern

The five survey approaches can be used to provide consumption information on the general

population or specific subpopulations of concern. However, the survey approaches differ in the

degree to which the target population must be determined prior to conducting the survey. For

telephone and mail surveys, the diary approach, and personal interviews conducted away from fishing

or hunting areas, the survey sample is typically identified before the consumption survey is conducted.

These survey approaches might be preferable when the objective is to characterize consumption for

an identified population or subpopulation of concern and there is a lack of specific information on

fishing locations. However, when a subpopulation is difficult to reach (e.g., low-income families with

no permanent address or phone number), combining these survey methods with on-site interviews

may be necessary to account for selection biases. Creel surveys, on-site personal interviews, and

random-digit dialing telephone surveys do not necessarily require identification of a target population

of concern, although these approaches do require that a geographic area of concern be identified.

Creel surveys and on-site personal interviews might be preferable when there are concerns about

contaminant levels in a specific waterbody, but little information is available on consumption of fish

or wildlife from the waterbody.

Another criterion that can influence the selection of the survey approach is the likelihood that the

target population of concern will have a low literacy rate or respondents will have difficulty

interpreting or providing responses to written questionnaires because of language or cultural barriers.

Survey approaches that involve direct interaction with respondents (telephone survey, personal

interview, and creel survey) might be more effective when it is suspected that the target populations

could have a low response rate or difficulties with written questionnaires. In some cases, the use of

multilingual questionnaires can assist the target population in providing responses to written

questionnaires. The same question, however, might mean different things to different groups of

people; thus, careful attention must be paid to ensure that responses to questions provide the same

information for all groups. It may be necessary to conduct an initial study of community

characteristics, including preliminary testing of a survey approach on focus groups and individual

cognitive interviews (Biemer et al., 1991). The information obtained can be used to develop effective

survey approaches tailored to the population of concern.

Because it can be difficult to identify subsistence fisher or hunter populations solely through

traditional approaches such as mail or phone surveys, it may be necessary for researchers to use other

methods to target these populations. A couple of methods might be of use. One method involves
3. SURVEY APPROACHES AND SELECTION CRITERIA

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contact with community organizations that represent these populations (e.g., Indian tribal

organizations) and have already established a relationship with community members (see, for

example, CRITFC, 1994). In addition, creel clerks (those who interview fishers at specific fishing

locations) might be good sources of information on fisher demographics because they have direct

contact with people at fishing sites (Shubat, 1993, cited in U.S. EPA, 1997b).

It is important to anticipate cultural and language requirements of each ethnic group in following the

community-based approach indicated above, as well as in other situations when conducting surveys.

Language barriers and literacy rates are important issues that must be addressed. Who is permitted

to ask questions and how the questions are asked can vary within different societies and can affect the

willingness and forthrightness of respondents. Cultural and religious sensitivity on the part of the

interviewer is important to maximize respondent participation and minimize errors or bias in the

consumption estimates of fish and wildlife. For example, Asians and Pacific Islanders are currently

the fastest growing minority population in the United States. For many first- and second-generation

immigrants and refugees, surveys that use creel, mail-in, telephone, or door-to-door approaches are

ineffective in obtaining reliable data characterizing fish and seafood consumption patterns (Nakano,

1996, cited in U.S. EPA, 1997b). Cultural patterns in species preference, preparation techniques, and

parts of the fish that are eaten or used in the cooking process should be understood when developing

the survey questions. Informal studies indicate a preference for bottom-dwelling fish, so Asian and

Pacific Islander surveys should include an appropriate species list (Soukhaphonh et al., 1996, cited

in U.S. EPA, 1997b). Pictures that help persons to identify what species they are catching would also

increase the understandability of the survey instrument. Socioeconomic issues and fear of authority,

particularly among subsistence fishers and hunters, can also adversely affect survey results if these

are not taken into consideration early in the planning process. In these situations, it may be useful to

consult and ask for assistance from community organizations such as churches or tribal organizations

in developing and conducting surveys.

3.3.2 Accuracy

The required accuracy of consumption rates is an important topic to be considered when establishing

the objectives for the survey. The survey study design has the greatest impact on the overall accuracy

with which consumption rates can be estimated. Thus, all five survey approaches can provide

estimates of high accuracy provided resources are sufficient, statistically valid survey designs that

include provisions for surveying an adequate number of respondents are used, and the design is

sensitive to the characteristics of the subject matter and the target population.

There are several different components to accuracy, including reliability (the variability or

repeatability of the response); validity (the ability of the respondent to provide the correct answer,

e.g., the number of fish consumed in the past month); measurement errors (which are associated with

the interviewer, the respondent, the questionnaire, and the mode of data collection); bias (the

consistent overestimation or underestimation due to survey design and sample selection); and random

errors. The measurement errors can be minimized by careful consideration of the target population

to ensure that the survey questions are not phrased in a way that is leading or unclear. Research has

shown that minor changes in a question’s wording can lead to large changes in respondent answers

(Biemer et al. (eds), 1991). Some level of respondent error is unavoidable since such error is a

function of differences in cognitive abilities or differential motivation to answer the questions.

However, sensitivity to these population differences in survey design and question construction can
3. SURVEY APPROACHES AND SELECTION CRITERIA

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help ensure that accurate information is obtained from as many respondents as possible. Interviewer

errors can be minimized using training and quality assurance/quality control (QA/QC) to standardize

interviewing procedures. Some respondent errors are inherent to the mode of data collection. For

example, it has been found that telephone interviews tend to result in shorter answers than do face-toface interviews (Biemer et al. (eds), 1991).

Other factors influencing the accuracy of the survey responses include whether the respondent views

the subject as nonthreatening or sensitive; whether respondents remain anonymous; the length of the

recall period (recall bias); the tendency for respondents to provide responses that conform to ideal

norms or enhance their self-image (prestige bias); the clarity of questions (question

misinterpretation); the familiarity of the respondent with the subject matter; the interest level of the

respondent in the subject matter; and the amount of specificity in the question (e.g., requests for exact

numbers versus approximations or ranges) (Wentland and Smith, 1993).

Selection criteria that can be used to discriminate among survey approaches with regard to accuracy

include the potential for recall bias, prestige bias, question misinterpretation, species misidentification,

and survey participation. Table 3 compares these criteria for the five survey approaches. Survey

approaches having a criterion listed as high have the least potential for inaccurate survey responses

and hence might result in a more accurate survey. Survey approaches based on on-site interviews and

creel surveys, if well designed, might not be affected by recall bias because the fish caught will not

have been consumed yet. Prestige bias is inherent in all survey approaches but might have the least

impact on creel surveys, which directly observe and record fish catch. The potential for question

misinterpretation is lowest for survey approaches that use direct interaction with respondents

(telephone survey, personal interview, creel survey) since the interviewer can clarify topics that are

unclear to the respondents, as well as showing models, photographs, or other visual aids to increase

accuracy of responses.

The potential for misidentification of fish or other species consumed is affected by recall bias, prestige

bias, and the familiarity of the respondent with the subject matter. The potential for fish

misidentification is lowest for creel surveys and on-site personal interviews because the interviewer

can both directly observe fish catch and allow respondents to visually select the species consumed

from displays of fish species. Survey participation affects the accuracy of consumption estimates by

affecting the number and characteristics of respondents that are evaluated in the survey. In general,

surveys that include a larger number of respondents and a low refusal rate provide a more accurate

representative estimate of consumption in the target population. Nonresponse bias resulting from low

respondent participation can be adjusted using various follow-up techniques. Survey approaches

using on-site interviews and creel surveys have the highest potential for survey participation since the

interviewer can directly engage respondents and motivate them to participate. An understanding of

and sensitivity to the characteristics of the target population of concern, as discussed in Section 3.3.1,

can help minimize nonresponse bias due to culture, religion, language, and attitudes toward

government and authority. Experts in the field have developed specific strategies to counter these

problems. The reader is directed to Tarrant and Manfredo (1993) and Vaske et al. (1996) for

additional information.
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3.3.3 Time Frame

The allotted time frame for the study, including survey development, implementation, analysis, and

reporting, might be driven by the need or needs the survey is designed to fulfill, for instance, making

management decisions. The fish consumption surveys listed in Appendix A required lengths of time

ranging from 4 months to 2 years to complete. It is difficult to discriminate among different survey

approaches based on study durations because the length of time to collect and process consumption

survey data depends on the resources available to conduct the study and the study design.

The survey approaches do differ on whether the responses to survey questions are obtained in real

time (telephone survey, personal interview, and creel survey) or over a longer time frame (mail survey

and diary approach). The mail survey and diary approaches might take longer to complete than other

approaches because respondents might not provide timely responses to the questionnaires.

3.3.4 Resource Considerations

The survey approach selected affects the resources (labor and cost) required to complete the survey.

As a general guideline, personal interviews cost at least twice as much as telephone surveys. Both

of these approaches are more costly than mail surveys (U.S. EPA, 1983). Few of the fish

consumption surveys listed in Appendix A include information on the level of effort and costs

expended to complete the survey. Cost and level of effort vary widely depending on the type of

survey and its geographical extent. Personal interviews and creel surveys will in most cases be more

expensive to implement than the other approaches because of the high personnel costs of one-on-one

contacts with respondents. Other costs can be incurred when survey planners consider offering

respondents some type of incentive (monetary or otherwise) for completing and returning the survey

instrument or participating in interviews. Examples of such incentives include reports of the survey

results, cash payments, food vouchers, recipes, or items such as baseball caps. Although some survey

approaches can be implemented for a lower financial cost, there may be an associated loss of data

quality and/or accuracy that can have serious management implications depending on the research

objectives.

3.3.5 Characteristics of the Source of the Fish or Wildlife

The decision about which survey approach to use can depend on the characteristics of the fish or

wildlife populations being evaluated and how the animals are harvested. Three important

characteristics are (1) the number of access points, (2) the fishing or hunting pressure, and (3) the

geographic area. Access points refer to fishing or hunting locations for shore fishers or hunters (e.g.,

beach, river bank, boat dock, fishing pier) and boat ramps for offshore fishers or hunters, as well as

parking lots or preserve entrances where fishers or hunters might begin their activities. In situations

with many different access points, off-site approaches like telephone surveys, mail surveys, and

diaries are preferred. One exception to this trend is the roving creel survey, an on-site approach that

can also yield good results in fisheries with many access points. In fisheries with high fishing

pressure, mail surveys, personal interviews, and access-point creel surveys may be effective because

fishers are concentrated in relatively small areas. Roving creel surveys, in which the interviewer

moves from fisher to fisher and sometimes from site to site, are more applicable to fisheries with low

fishing pressure, where ample time is available for instantaneous counts and for interviewing all

fishers. For fisheries covering a large geographic area, approaches not requiring face-to-face contact
3. SURVEY APPROACHES AND SELECTION CRITERIA

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(e.g., phone and mail surveys, diaries) could be more appropriate. In any case, available personnel

and time resources are also important considerations in selecting the survey approach since, for

example, multiple interviewers can cover larger geographic areas simultaneously.

3.4 Summary

This chapter introduced the five consumption survey approaches covered in this document and

presented selection criteria states and tribes can use to choose the appropriate method for the

objectives of their project. Due to the complexity of estimating consumption in specific

subpopulations, no single method can be recommended in all cases. In fact, a combination of

approaches may be most appropriate in many cases. For example, a mail survey for which the sample

population is taken from fishing license records might not accurately assess consumption for a group

that does not always hold licenses (e.g., subsistence fishers). Thus, a combination of mail surveys

with on-site interviews might provide a more representative picture of consumption. Key

considerations that should be carefully evaluated in selecting a survey approach include the target

population or subpopulations of concern, the level of accuracy required in the survey results, the time

frame in which the survey information is needed, the staff and financial resources available to conduct

the survey and analyze the survey data, and the characteristics of the fishery being evaluated.
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-1

SECTION 4

INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4.1 Overview

This chapter provides specific guidance on designing and implementing consumption surveys using

one of the five approaches introduced in Chapter 3. For the sake of brevity, the reader is referred to

other texts where appropriate for detailed guidance and examples. Because all of the approaches are

aimed at obtaining consumption rate estimates, there are similarities in study design and

implementation. Issues common to all approaches are discussed in Sections 4.2 through 4.4; Sections

4.5 through 4.9 present method-specific issues.

4.2 General Instrument and Study Design Issues

The four steps in the design and development of a consumption survey are as follows:

1. Identification of the survey objectives.

2. Preparation of a sample design and analysis plan, which includes 

• identification of the target population(s) and selection of the sampling strategy for the survey

population(s)

• identification of the specific data to be gained from the survey

• the analytical/statistical methods to be used once the data are collected

3. Selection of the survey approach to be used to obtain the data.

4. Design of the survey instrument.

Study objectives and data needs were discussed in Chapter 2. The issues surrounding the selection

of a particular survey approach were discussed in Chapter 3. This chapter addresses the remainder

of the issues involved in questionnaire design and the preparation of the analysis plan.

Population selection cannot be separated from how the consumption data will be used. If the

consumption data will be used for the assessment of human health risk, surveying the population that

consumes fish or wildlife from a specific region or contaminated waterbody is appropriate. This

population will typically consist of fishers or hunters and perhaps their families if the sample unit is

the entire household. Additional considerations in selecting populations are described under the

specific survey approaches. The reader is advised to consult a statistician at this stage in the process

to ensure a good study design, appropriate selection of the survey population, and confidence that the

research questions can be answered by the survey results. 

Each of the five approaches described in Section 3 requires that questions be answered, verbally or

in writing, by potential consumers of fish or wildlife. The specific questions to be asked in a

consumption survey are dependent on (1) the objectives of the survey, (2) the population being
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surveyed, and (3) the available resources of the interviewer. For most surveys, the questions can be

developed from the list of information requirements given in Table 1.

Each question in the questionnaire should make a contribution to answering a specific information

need. Pollock et al. (1994) suggest creating a data requirement-by-question matrix for the

questionnaire to confirm that each question is relevant to the study objectives. This matrix should

specify all information requirements necessary to adequately describe the consumption patterns for

the target population (Table 1). This matrix will help facilitate the iterative process of constructing

effective questions for the questionnaire.

Of the four issue categories given in Table 1 (personal and demographic characteristics, fishing and

hunting activities and behavior, preparation and consumption patterns, and consumption advisory

awareness, knowledge, attitudes, and beliefs), only questions on demographic characteristics and

consumption patterns are strictly necessary to derive rough consumption estimates. Questions on

fishing and hunting activities and behavior would be asked only of respondents who indicated they

fished or hunted. Advisory awareness questions would be relevant only in areas where there are

advisories; these questions can be especially relevant if epidemiological data will be used to

supplement a risk assessment.

Personal and demographic questions are asked to identify the respondent’s membership in a particular

population group and to allow the researcher to test for correlations between consumption and various

population parameters (see Table 1 for examples). Sociodemographic variables such as age, gender,

community type, educational level of head of household or respondent, ethnic origin or race, family

size and composition, geographic region, income, occupation of head of household, and religion can

influence patterns of intake. Current employment status might affect the amount of time spent fishing

or hunting and the amount of fish or wildlife consumed. Without an adequate demographic base, the

interpretation of the results can be biased in unforeseen ways.

Before specific questions regarding fishing and hunting and consumption can be developed, the

researcher must choose a time period for which respondents will be asked to recall consumption. One

of the most important methodological issues in regional fish consumption surveys is to adequately

address the dual objectives of obtaining accurate recall of consumption estimates and capturing

variation over time (usually a full year cycle). The accuracy of recall is inversely proportional to the

length of the recall period. Recall periods typically range from 7 days to 1 year. One method

developed to meet these dual objectives is the “rolling cohort” method, which minimizes an

individual’s required recall time but maximizes the length of the study. The rolling cohort method

uses statistical random selection techniques to place sample cases into random cohorts and then

surveys the cohorts in waves spaced two or more weeks apart. The results obtained are treated with

standard statistical weighting techniques to represent an even flow of data across the year cycle (West

et al. 1993). Using this method, different groups of people are sampled for portions of a relatively

long study period; for more information on this approach see West et al. (1989, 1993). Alternatively,

using a single cohort approach, the estimation of consumption over an entire year is a relatively

difficult matter. The respondent’s recall over that period of time is likely to be incomplete. Recall

error can occur in any one of the four steps involved in answering a question: (1) comprehension, (2)

retrieval of information, (3) judgment, and (4) response (Eisenhower et al., 1991). The rolling cohort

method is an important surveying method that can be used to reduce recall error based on inaccurate

retrieval of information. Additional ways in which recall error in each of these four areas can be
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reduced are discussed by Eisenhower et al. (1991). Some examples include designing questions that

are easy to comprehend and do not require complicated judgments about whether the response is

representative of others’ responses, and providing visual cues to aid recall and estimation. For some

survey methods (e.g., diary and creel survey), recall period is not an issue.

Questions on consumption are obviously central to the questionnaire, but are often the most difficult

to design in an unambiguous manner. Estimates of meal size are subject to considerable error. This

type of question is more difficult to ask and answer in surveys without personal contact (e.g.,

telephone and mail surveys) because questioning must be done without the help of the models of

portion sizes often used in personal interviews. The use of photos of different-sized fish or other meat

portions in mail surveys (with ruler bars for scale) and reference to familiar objects (e.g., a deck of

cards as approximately the size of a 3-ounce [oz] portion) in telephone surveys can assist participants

in providing accurate responses to inquiries about meal size. A typical fish or wildlife consumer

might have difficulty quantifying the weight of tissue eaten over a specified interval, but might be able

to recall the number of meals eaten over the time period in question. During the analysis of data, the

number of meals can be converted into weights by multiplying the number of meals by the

participant’s estimate of the meal size typically consumed. EPA (1997a) has identified a value of 8

oz (227 g) of cooked fish fillet per 70-kg consumer body weight as an average meal size for the

general adult noncommercial-fish-consuming population and for women of reproductive age. This

meal size, however, does not represent higher-end exposures where persons consume more than the

average amount in a given meal, and it might not reflect meal sizes consumed by children or those

adults who eat smaller portions. For this reason, it is recommended that participants be asked to

estimate meal size instead of assuming default values.

Studies show that the typical weight loss in cooking a fillet or steak of fish is about 20 percent (Jacobs

et al., 1998). Thus, using cooked weights results in a slightly lower intake rate. In researching

consumption surveys, EPA has found that some surveys have reported rates for cooked fish, others

have reported rates for uncooked fish, and many more are unclear as to whether rates for cooked or

uncooked fish were used. For the purpose of developing ambient water quality standards, EPA

intends to use cooked weight assumptions because, by and large, cooked fish is what people consume.

EPA believes, therefore, that these values appropriately reflect the potential exposure from fish

consumption better than uncooked weights. Pictures of cooked fish on a plate in relative size

comparison to other food on the plate, the plate itself, silverware, and napkin help respondents

visualize portion size and lead to enhanced accuracy (Humphrey, 1976, 1983; West, 1989,1993).

However, EPA’s fish advisory program recommends that intake rates in developing risk analyses for

advisories be based on uncooked weights because chemical analysis to determine concentrations of

pollutants in tissue is almost always based on analysis of uncooked portions of fish. Uncooked fish

portions can similarly be compared to a common object, such as a deck of cards, to better estimate

weight. Questions included in the surveys should clearly identify whether weights represent cooked

or uncooked fish.

For a question to be readily understood, it must be simple and straightforward. The design of each

specific question must consider both question structure and question wording. The position of each

question in the overall survey is also important. Each of these topics is discussed below. The reader

is referred to Biemer et al. (1991), Wentland and Smith (1993), Pollock et al. (1994), and the

references cited therein for more information.
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Question structure. Four general types of question structures are available (Pollock et al., 1994): (1)

open-end questions, (2) closed-end questions with ordered response choices, (3) closed-end questions

with unordered response choices, and (4) partially closed-end questions. Open-end questions have

no categories from which the respondent can choose; however, interpretation of all but the simplest

open-end questions can be quite difficult. Closed-end questions provide several answer categories,

which can be ordered sequentially (e.g., numerically) or unordered. The answers to closed-end

questions are easy to summarize quantitatively. Response options must be selected carefully so that

the choices are mutually exclusive, inclusive of all reasonable choices, and easy to understand.

Categories also may provide cues to aid respondents’ recall (Bradburn and Sudman, 1991). Partially

closed-end questions allow an open-ended option such as “other.” This option represents a good

compromise between open-ended and closed-end structures (Pollock et al., 1994), but some research

suggests that the “other” category is rarely selected (Bradburn and Sudman, 1991).

For closed-end questions, the specific ranges for each response alternative can affect the way in which

the question is answered. Values in the middle range of the scale selected are often assumed by

respondents to reflect the “average” or “typical” behavior, whereas the extremes of the scale are

assumed to represent the extremes of the distribution (Schwarz and Hippler, 1991). Thus respondents

will choose a given value more frequently if it is not at either extreme of the range in which it is

placed, and they will select a given range more frequently if it lies closer to the middle of the overall

range.

Question wording. The specific wording of questionnaires on fish consumption must be developed

very carefully to elicit nonbiased responses. Some recommended guidelines for question wording are

listed below (Pollock et al., 1994):

• All alternatives of a multiple-choice question should be given.

• As few words as necessary should be used.

• The units that apply to each response should be given.

• The time frame covered by the survey should be clear.

• Only one concept or issue should be addressed by each question.

Draft questions should be reviewed carefully for ambiguity. In survey approaches that include

personal contact (e.g., telephone surveys and personal interviews), ambiguity can be corrected through

interaction between the interviewer and respondent. It is preferable to minimize ambiguity by testing

the questionnaire on a focus group. Salant and Dillman (1994) also provide a good discussion of

many of the issues surrounding good question wording, such as content, sentence structure, and the

order of response choices. Appendix 6.A of that book provides samples of wording problems and

possible solutions. 

Question order. Topic sections should be arranged for the convenience of the respondent, not that

of the researcher. There is likely a logical order to grouping questions which will aid in respondent

recall. The questions should build on each other. For example, rather than asking “Did you wear

your seatbelt the last time you were a passenger in a car?” the following series of questions may be

more effective: “When was the last time you rode in a car as a passenger? (Today, yesterday, 2 days

ago)” “How long was the trip? (Less than a mile, 1-2 miles, more than 2 miles)” “Did you wear your

seatbelt? (The entire time the car was moving, part of the time, or not at all)” This kind of cognitive

design can be very effective in minimizing respondent error and should be used for important
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questions (Salant and Dillman, 1994). In addition, it might be useful to phrase important questions

a couple of different ways and ask them at different points in the survey to measure respondent

accuracy. In a personal interview, these answers can be compared and if needed, the respondent can

be asked additional questions to help clarify the most accurate response.

The first one or two questions might be the most critical, particularly for mail surveys, since these

might determine whether the respondent chooses to complete the questionnaire. Sensitive questions

or questions that are difficult to answer should be asked near the end of the interview so as not to

threaten the respondent and compromise the rapport between interviewer and respondent. Sensitive

questions include demographic questions such as age, income, and education and questions about

whether the fisher has an applicable fishing or hunting license or is familiar with a particular advisory

or regulation (Pollock et al., 1994).

4.3 General Statistical Analysis and Data Interpretation Considerations

A typical survey will generate a considerable amount of data from each respondent. Although the use

to which the data will be put is established before the survey begins, the same is not always true of

the manner in which the data will be analyzed and interpreted. To the extent possible, however, the

researcher should specify the details of analysis and interpretation methods as early as possible in the

survey design process because they might have a significant bearing on the form and content of the

questions asked. Addressing these issues during questionnaire design minimizes difficulties that arise

during data analysis and interpretation.

Statistical considerations play an important role at both the survey design and results analysis levels.

At the survey design level, statistical methods are used to determine the appropriate number of

sampling units (potential fish consumers) and how those sampling units are to be selected from the

target population. Final sample size will depend on the level of precision required for the estimates.

In some cases, the statistical design might need to be modified based on the resources available to

conduct the survey. The Bureau of the Census may be consulted to obtain information about total

population and/or subpopulation numbers present in a particular area. The Bureau can provide data

files listing demographic information of age, gender, and/or ethnicity by census tract, for a cost.

The probability technique can be used to select subsamples of licensees or other designated groups.

For example, if existing survey data indicate that 20 percent of the general population 16 years of age

and older in a state fish, a researcher could have to contact 5,000 people to have a sample size of

1,000 fishers. If the response rate is 50 percent, however, a researcher could collect data from only

500 fishers. To adjust for nonresponse, the researcher would need to attempt to contact 10,000 people

to collect data on 1,000 fishers. Obviously, this process would be more efficient if the sample were

from a list of fish license holders. This is a process known as stratified sampling, where a target

population is subdivided into subgroups prior to sample selection. With a license holder list,

however, the researcher would not obtain consumption data from those people who fish without a

license, who can account for as much as 25 percent of fishers. This and other issues relating to sample

representativeness are discussed in Pollock et al. (1994), U.S. EPA (1997a), Scheaffer et al., (1990),

and other references cited in this chapter.

An appropriate sampling design is imperative to ensure statistical rigor and minimize bias and

sampling error in the study; the reader is therefore advised to consult an experienced survey researcher
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and/or statistician during the sample selection stage to achieve adequate representation of the survey

population.

Additional problems in sample size selection might be encountered when attempting to look at special

populations, such as those who eat fish or wildlife frequently. The design of population surveys and

sampling techniques for events and populations that are nonuniform or infrequent presents additional

statistical constraints (Kalton and Anderson, 1986; Sudman et al., 1988). A common solution to

determining sample size in these cases is to predict the response frequency of the most constraining

(i.e., rarest) piece of data among the questions to be answered and then calculate the sample size

required to ensure that the minimum number of replies needed for statistically valid results for the

group described by that constraining datum would be received. If fish consumption by pregnant

women (3 percent of the population) represents the rarest piece of data desired and one wanted a

sampling error of plus or minus 5 percent, assuming a conservative 50/50 distribution, a survey of 400

pregnant women would be needed. To reach 400 pregnant women, one would need to contact 53,332

people in the general population: 53,332 people x 0.50 (response rate) x 0.50 (% female) x 0.03 (%

pregnant) = 400 pregnant women. If the percentage of pregnant women in the target population

differs from 3 percent, this calculation would need to be adjusted accordingly. Obviously, this

method would be very inefficient and costly, so alternative methods for contacting pregnant women

would likely be considered, such as working through medical doctors, clinics, or hospitals.

Once data are gathered and prepared for analysis (coded, entered into a database, and checked for

errors), they must be statistically analyzed. Three basic methods of statistical analysis are used with

survey data—univariate, bivariate, and multivariate analysis. Univariate analysis examines one

variable at a time for the purpose of describing a survey sample and is usually presented as frequency

distributions (percentages), measures of central tendency (mean, median, or mode), and measures of

dispersion (range, standard deviation). Measures of central tendency and dispersion are applicable

only to interval or ratio data. Frequency distributions can be used for nominal, ordinal, or interval and

ratio data, although for interpretation and presentation purposes, interval data are often collapsed into

categories, such as age ranges. Subgroups within a sample can be described using univariate analysis

as well. For example, if females were selected in the analysis, this subsample would become the new

“sample” and could be described using univariate analysis on other variables, such as income.

Bivariate and multivariate analyses are used to examine associations among variables. In bivariate

analysis one variable is used to explain the distribution of another variable; for instance, the

relationship between income and subsistence fishing or hunting could be investigated using regression

analysis. In multivariate analysis two or more variables, such as income and education, are used in

combination to attempt to explain the distribution of another variable, such as subsistence fishing or

hunting.

The term descriptive statistics refers to data reduction techniques used to present results in a usable

and comprehensible form. The most common descriptive statistical methods are the estimation of

population parameters such as percentages, means, standard deviations, and correlation coefficients,

all of which are used to summarize data. Care must be taken when summarizing the data because the

statistical methods appropriate for calculating unbiased estimates of the population parameters will

depend on the sampling method (e.g., simple random sampling, stratified sampling, proportional

stratified sampling). There are important statistical issues to consider when making adjustments for

the various types of sampling inaccuracies (see Section 3.3.2). Weights might need to be applied
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

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during the estimation of population parameters where the weights account for different sizes of

subpopulations, for differential nonresponse rates, or for disproportionate sample selection

probabilities. For example, there might be cases where probabilities of respondent selection become

disproportionate in field implementation such that the sample population disproportionately represents

different demographic groups. In those cases where probabilities change between the design and

implementation stages, post-stratified weights are used to estimate population parameters that are

derived from a sample distribution that does not correspond to the known population distribution.

An experienced survey statistician should be consulted to facilitate the appropriate summary of your

data. The term descriptive statistics also includes methods of displaying data graphically. Numerical

and graphical exploratory data analysis techniques (Tukey, 1977) can be used to investigate the data

for trends or patterns that might not be immediately obvious. Interactions between factors such as

class, income, and race can be significant and extremely important in a fish consumption evaluation

(West et al., 1995). Interactions between such factors can mask important characteristics of the data

set unless thorough exploratory techniques are used.

Inferential statistics can be divided into estimation and hypothesis testing. Estimation is probably the

most useful statistical method for analyzing consumption data. The process of estimation entails

calculating, from the data of a sample, some statistic (e.g., the sample mean) that is offered as an

approximation of the corresponding parameter of the population (e.g., the population mean) from

which the sample is drawn. Interval estimates such as a 95 percent confidence interval for the mean

can be constructed. The interpretation is that the probability is 95 chances in 100 that the interval

contains the true but unknown mean. Estimation methods can be helpful in analyzing the relationship

between two or more variables (measures of association). Different statistical tests of association are

used for different types of data, such as nominal and ordinal data (F-test), and interval or ratio

variables (t-test, Pearson’s product-moment correlation, regression, path and factor analysis, analysis

of variance, discriminant analysis, and log-linear models).

Hypothesis testing employs tests of statistical significance that measure the probability that a

parameter falls within a certain range. The most common acceptable level of significance is 0.05 (p

< 0.05), which means “the probability of a relationship as strong as the one observed being

attributable to sampling error alone is no more than 5 in 100” (Babbie, 1990). It is important to note

that although there could be a statistically significant difference in a measure of association between

two groups, the actual difference might be so small as to be irrelevant in the study. Conversely, large

differences in consumption rates might not be statistically significant. When sample sizes are large,

it is particularly important to pay attention to this phenomenon since small differences might appear

to be statistically different. For example, fish consumption (mean g/person/day) might be 17.5 g for

Group A and 18.5 g for Group B and might be significantly different at the 0.05 level. For policy

development and decision-making processes in risk assessment, a difference of 1 g might not be

important. Common tests of significance are chi square for nominal/ordinal data and t-tests and

analysis of variance (ANOVA) for interval data. Note that stated hypotheses (null and alternative)

are required for tests of association. Large differences in consumption rates that are not statistically

different are related to small sample sizes or large variances. If variances are high, it is appropriate

to examine the data for outliers and apply the appropriate nonparametric test.

For parametric tests, however, the underlying assumptions of independent samples, normality, and

equal variances should hold true. If the assumptions of normality and equal variances do not hold,
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4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-8

nonparametric tests should be used. Nonparametric statistics consist of counting or ranking of data

or examination of the sign differences of paired data (Steel et al., 1997).

EPA (1997a) has provided guidance on using fish consumption data to develop estimates of

population exposure to contaminants for human health risk assessments. The document includes

guidance on deriving fish consumption estimates and provides summary results and methods for many

of the fish consumption surveys performed in recent years. The information in the document is

summarized briefly below; the reader is referred to the source for a more complete discussion.

If consumption rates are to be used in a risk assessment, which typically evaluates chronic exposure,

an estimate of average daily consumption for a relatively long period of time (e.g., weeks to a year)

is appropriate. For some chemicals of concern, acute toxicity or developmental toxicity might also

be of concern. In these cases, estimates of maximum individual daily consumption over a shorter

period of time (e.g., 1 week or less) might also be warranted. The most basic equation for estimating

individual consumption rates is as follows:

The averaging period must be carefully selected, keeping its intended use in mind. Consumption

estimates to be used to evaluate acute exposure should be the maximum of the daily consumption

rates calculated, assuming an averaging time of 1 day. The reader should consult U.S. EPA (1997a)

for more information on the calculation and application of averaging periods.

Per capita consumption rate estimates require that days in which fish or other organisms of concern

are not consumed be factored into the calculation. For estimates of daily consumption over a 1-year

period, surveys that include less than a 1-year recall period must include some method of

extrapolation to time periods for which consumption estimates are not available. For example, if a

respondent indicates he eats four fish meals per month from the waterbody in question during the 3-

month fishing season and none during the remaining 9 months, the consumption rate would be one

meal per month for the entire year (4 meals/month x 3 months/12 months). This information could

also be translated into consumption per day if the meal size were known.

Another issue that must be addressed is the treatment of respondents who do not eat fish or wildlife

from the waterbody in question, or do not eat fish or wildlife at all. In a telephone survey, for

example, the number of nonconsumers of fish might outnumber the consumers. The decision on

whether to include these respondents in the consumption estimate or exclude them is dependent on

the specific goal of the risk assessment. Per capita consumption rates by definition would include

nonconsumers and consumers of fish. Including the zero-consumption respondents is a more accurate

representation of the overall fish consumption rate for a population, but it also underestimates the

mean consumption rate of those who eat fish from the target site by diluting the estimated mean

consumption with nonconsumer zeros. Thus using the estimated mean per capita fish consumption

could seriously underestimate the risk to regular consumers of fish. An alternative approach, which

is more conservative with regard to risk, is to use an upper percentile of the per capita fish

consumption distribution, such as the 90 , 95 , or 99 percentile, for risk assessment purposes. If, th th th
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-9

on the other hand, the decision is made to exclude nonconsumers of fish from the analysis of the

survey results, the researcher must be able to distinguish between the respondents who never eat fish

and the respondents who eat fish but did not eat fish during the recall period. The latter should be

included in consumption rate calculations. Many of the fish consumption rate estimates provided by

EPA (U.S. EPA, 1997a) are based on fish consumers only, resulting in higher consumption rates,

which would be more conservative or protective of those persons when estimating risk (see also

Gassel, 1997). Thus, it is important to state explicitly whether the consumption rate derived from the

survey data includes consumers only or both consumers and nonconsumers.

Some of the questions that might be asked in the interview (e.g., preparation methods, tissues

consumed, species, size) do not relate directly to overall consumption estimates but may be used to

modify the dose calculations in a risk assessment. For example, cooking fish almost always reduces

contaminant levels, so reducing the dose by an appropriate correction factor depending on the cooking

method might be appropriate. A detailed discussion of the way in which this ancillary information

on fish consumption can be used is given in U.S. EPA (1997a).

Consumption data can be presented in a variety of ways. Consumption estimates can be given as

point estimates or as distributions illustrating the variability in the population. A point estimate is a

single value such as 50 g/day, whereas a distribution can be summarized by a measure of central

tendency (e.g., mean, median), a standard deviation, and a shape of the distribution curve (e.g.,

lognormal). For many risk assessments, risk estimates for individuals at both the central tendency and

high-end portions of the exposure distribution are made. To preserve the maximum amount of

flexibility for future uses of the data, researchers should present consumption data as a distribution.

Point estimates from within the distribution can be used in deterministic risk assessments, and a

discussion of the distribution can be used in probabilistic risk assessments. The lognormal

distribution has been shown to provide a good fit to consumption data (Murray and Burmaster, 1994;

Ruffle et al., 1994). The choice of a distribution for use in a probabilistic risk analysis should be based

on a thorough evaluation of the data, however, since the lognormal distribution might not always

provide a good fit to food consumption data (Driver et al., 1996). Ideally, the response for each

sampling unit should be retained, thereby providing an accurate description of the observed

distribution of responses without relying on assumptions about the theoretical distribution. It is highly

recommended that consumption data be collected and presented as a distribution, rather than as point

estimates, to provide sufficient information for the decision-making process.

Demographic data collected in the questionnaire can be used in conjunction with the consumption

data in several ways. For diet/health surveys that could result in consumption advisories,

consumption data for various ethnic groups can suggest the form (e.g., languages) in which the

advisory should be available (Allen et al., 1996). Data on age and residence time can be used in risk

assessments to evaluate whether additional subpopulations (e.g., children, older persons, and pregnant

and lactating women) should be evaluated based on their different rates of consumption. In all cases

where demographic data are used in this manner, statistical tests of significance should be employed

to determine whether specific subpopulations have consumption rates significantly different from

those of the rest of the sample population.
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

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4.4 General QA/QC Considerations

Establishing adequate quality assurance (QA) and quality control (QC) procedures during all stages

of a survey is critical for collecting valid data. Both QA and QC procedures are incorporated as part

of the study design and are intended to minimize measurement errors or other biases. QA procedures

are put in place before data collection begins; QC procedures are followed during or after data

collection. Thorough training of the interviewers in fish identification would be considered a QA

activity, while random spot checks of interviewers by a supervisor during data collection would be

a QC activity. QA and QC procedures for reducing interviewer-related errors are discussed by Fowler

(1991).

At the heart of nearly all QC procedures is the simple concept of double checking, for example, of

data collected, data entered into a database, or calculations. Field and/or office audits to ensure that

planned procedures are being followed might be appropriate depending on the survey approach.

For some survey approaches, direct entry into computers might not be practical. In these cases,

secondary entry into some sort of data processing software is typically necessary. The data entry step

has a high potential for errors, but several QC procedures can be implemented to minimize or

eliminate errors of this type. The two most common procedures are (1) proofreading of some or all

the data entered and (2) entry of all data twice into separate files and subsequent comparison of the

two files. Data entry errors can be minimized by designing the survey forms in such a way that they

can be easily read by Optical Character Recognition (OCR) software (Heineman, 1991). Survey

forms that require a considerable amount of hand entry by the interviewer might not lend themselves

readily to this type of scanning. Once the data have been entered into a computer, checks can be

performed to detect inadmissible and out-of-range values.

QC procedures can be implemented to check the internal consistency of the questionnaire responses.

Responses given in one category can be used to check those in another. For a target waterbody,

information on catch rates and locations should be consistent with information on amounts and

species of fish or wildlife consumed. If data from a respondent are not consistent, the researcher may

consider deleting that respondent from the database. A list of specific information needs and crosschecks should be prepared prior to checking the data to ensure that respondents are objectively and

consistently deleted from the database when information is missing or not consistent.

4.5 Telephone Survey

4.5.1 Advantages

• The telephone survey can assess region-specific consumption rates, depending on how

the respondents are selected (for instance, by proximity to a particular waterbody).

• This approach can target specific subpopulations of concern when these populations can

be preselected on some basis or when specific limiting questions are included on the

surveys.

• This approach is generally about half as expensive and less time-consuming than the

personal interview because less training of interviewers is required and travel costs are
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-11

not necessary. Larger numbers of respondents can thus be contacted (see

U.S. EPA, 1984).

• A high rate of success for completing interviews is likely for known phone numbers,

although the success rate is 5 percent lower than that for personal interviews

(U.S. EPA, 1984) because of lack of personal contact. Success rates are lower for

random phone numbers (random-digit dialing) because of the prevalence of unsolicited

phone calls from telemarketers and solicitors.

• Sensitive information can be obtained more easily than with other approaches,

particularly if the respondent remains anonymous.

• Since this approach provides immediate responses to questions, analyses can be

completed more quickly.

4.5.2 Disadvantages

• Interviewers cannot reach people who do not have phones or those with unlisted

numbers. (Only random-digit dialing includes unlisted numbers.)

• Interviews might need to be limited in scope and length, so the number of questions must

be carefully chosen.

• Language and cultural barriers that might be encountered are difficult to compensate for

in telephone surveys.

• It is difficult to verify information given.

• Telephone surveys do not have the ability to show visual aids, which can help in locating

study site boundaries and in standardizing meal sizes; however, a common size reference

such as a deck of cards can still be used.

4.5.3 Specific Issues for Instrument and Study Design: Telephone Survey

Telephone surveys have not been widely used in fisheries, but they might become more common in

the future (Pollock et al., 1994). Selecting the numbers to be dialed is a critical first step that must

be addressed before any other details of the survey. If the sample group includes people who do not

eat fish or wildlife, additional questions will have to be asked to separate this population from the

fish/wildlife-consuming population. 

Various methods have been used to select the individuals to be interviewed. Pollock et al. (1994)

divide the methods into (1) random-digit dialing, (2) directory frames, and (3) special frames.

Random-digit dialing is easy to do, but may be costly and inefficient if done manually because of the

additional effort required to eliminate nonworking or nonresidential numbers. A computer-assisted

telephone interviewing (CATI) system can make random-digit dialing very efficient, particularly if

numbers are purchased from a survey sampling company and are prescreened. Computer dialing

eliminates nonworking and nonresidential numbers quickly. 
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

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Directory frames can be constructed from telephone directories. However, they do not include

unlisted numbers and quickly become out-of-date. Both random-digit dialing and directory frame

methods will include a large proportion of people who do not consume fish or wildlife. Special

frames can be constructed from boat registration lists, angling or hunting club membership lists, and

fishing and hunting license files, for example (Pollock et al., 1994). Such special frames have the

effect of selecting a subpopulation likely to have a consumption profile that differs from that of the

general population. This should be noted in interpreting these results, and care should be taken not

to generalize from such a group to the greater population.

Telephone surveys are often conducted from a single location with the help of several different

interviewers. Interviewers should be told how many callbacks to make and at what times of day

before they abandon a sample unit. With a CATI system, the number of callbacks can be preset for

the whole sample in the supervisor’s computer. Generally, telephone methods are least efficient

during holidays and summer, when people are away from home and more redialing is necessary to

obtain an interview (Pollock et al., 1994). To maximize the cooperativeness of respondents, telephone

surveys should last no longer than 10 minutes.

Estimating consumption over a long time period can be difficult. Ideally, respondents would be

interviewed using the rolling cohort method described in Section 4.2: cohorts would be selected

randomly, and calls and callbacks would be spaced out over the study period to give fairly even time

period coverage. This approach is also effective at minimizing necessary recall time so recall

accuracy is improved.

For a question to be understood verbally, it must be simple and straightforward. For questions that

have a definite number of responses, the possible responses should not be so numerous that they must

be repeated.

4.5.4 Specific Issues for Statistical Sampling and Analysis: Telephone Survey

In addition to determining the number of respondents required, statistical methods should also be used

to select the respondents from the target population. For random-digit dialing, several methods can

be used to select numbers. Phone numbers can be purchased from companies that specialize in the

scientific development of random telephone number lists by geographic area. An alternative twostage sampling method, known as the Mitofsky-Waksberg method, requires that the first six digits

(area code and prefix) be preselected and the last four digits be selected randomly. Multistage

methods are designed to improve the frequency of residential number hits. For example, a two-stage

cluster method treats the sampling frame of telephone numbers as a set of banks of 100 numbers each.

A bank is defined by an area code, a prefix, and the first two digits of the suffix. Within a bank,

numbers are selected randomly. If the first number selected is not a residential number, the entire

bank is rejected because banks usually have no or many residential numbers. If the first selected

number is a residential number, additional numbers are selected until the specified number of

households has been drawn (Pollock et al., 1994).

Directory frames can be created by simple random sampling, stratified random sampling, systematic

random sampling, and add-a-digit sampling. The last method involves adding a number from 1 to

9 to a selected telephone number. This method can select people with unlisted numbers or people
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-13

with numbers put in service after the directory was published. Sampling methods for creating

directory frames are discussed in Pollock et al. (1994) and Salant and Dillman (1994).

Bias can be associated with telephone surveys due to the presence of multiple phone lines in a

household (including cellular phones), households without any phones, or a large number of no

answers due to the prevalence of answering machines. It might not be appropriate to assume that the

results for the responding group are representative of the nonresponding group. This is especially true

in fish consumption surveys, where the lower income, non-telephone households might have a higher

consumption rate than that of other households. In this situation, an alternative mode of

administration would be more appropriate to effectively reach the target population or sub-population.

For more information regarding the analytical treatment of bias, the reader is referred to texts such

as Scheaffer et al. (1990) and Biemer et al. (1991), or a statistician.

4.5.5 Specific Issues for QA/QC: Telephone Survey

If the telephone interviews are conducted from a central location, the supervisor can listen to a portion

of the interviews to ensure that the survey is being completed in accordance with the design quality

control procedure. During these audits, the supervisor should also check the data entry forms that the

interviewer completes for transcription or other errors. The interviewer can also conduct a brief selfreview after each interview or at the end of the day. Data entry errors can be corrected more easily

if they are caught while the events of the interview are still fresh in the interviewer’s memory.

Many telephone surveys incorporate a CATI system, whereby the interviewer keys responses directly

into the computer. This eliminates the error-prone transfer of data from paper to computer. A typical

system is programmed with editing instructions to ensure that only valid responses that are consistent

with the question may be entered. The computer automatically follows complex skip patterns (e.g.,

if answer to number 4 is no, go to question number 9) which reduces both confusion during the

interview and training time for the interviewers.

4.6 Mail Survey

4.6.1 Advantages

• Mail surveys can assess region-specific consumption rates, depending on how the

respondents are selected (obtaining addresses from license applications, fishing

tournament entries, etc.).

• This approach can target specific subpopulations of concern when these populations can

be preselected on some basis or when specific limiting questions are included on the

surveys.

• This approach is the least costly since interviewers are required only for obtaining

follow-up information. Large numbers of respondents can be contacted over a broad area

(see U.S. EPA, 1984).

• Respondents are most likely to provide honest answers and fewer “socially desirable”

responses (U.S. EPA, 1984).
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-14

• More complex data can be obtained because the respondent can take time to consider the

questions asked and consult other sources if necessary.

• The survey can cover more types of questions, so multiple objectives can be evaluated.

• Visual aids (geographic, meal size) can be added to improve accuracy.

4.6.2 Disadvantages

• Mail surveys cannot reach people who lack mailing addresses, such as migrant workers,

homeless people, and other people who move frequently or have informal living

arrangements. These groups might contain a disproportionately high number of

subsistence fishers and thus might be groups at higher risk overall.

• If addresses are obtained from specific sources, such as lists of licensed fishers or

hunters, the survey will miss unlicensed fishers or hunters and others possibly at high risk

from fish or wildlife consumption.

• Questions must be carefully designed to compensate for the lack of social interaction

provided by telephone or personal interviews and must provide adequate instructions to

elicit satisfactory responses and motivate the respondents to cooperate (U.S. EPA, 1984).

• Questions need to be limited in scope and complexity, preferably requiring only short

answers or checking off multiple choices, to maintain cooperation by the respondent.

• Voluntary mail surveys require substantial follow-up efforts or incentives to achieve

reasonable response rates (either by conducting telephone interviews or by offering the

respondents the choice of phoning in their answers).

• Skewed or biased response is possible because there is no opportunity for clarification

through personal interaction.

• A mail survey is likely to produce a higher number of inaccurate and incomplete

responses because it lacks the opportunity to instruct and motivate provided by personal

interview approaches (U.S. EPA, 1984).

• This type of survey may undersample groups with low literacy rates and respondents who

have difficulty understanding the questions or cannot read the language in which the

questions are written.

4.6.3 Specific Issues for Instrument and Study Design: Mail Survey

Mail surveys have often been the preferred off-site approach for collecting fish and wildlife

consumption information because they can be relatively simple to conduct and cost-effective. If the

consumption data will be used for the assessment of human health risk, surveying subpopulations that

consume fish or wildlife from a specific region or waterbody that might be contaminated is
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-15

appropriate. This can be done by selecting addresses within a specified distance from the waterbody

in question.

The population to be interviewed is often selected with the help of fishing or hunting license files.

This method might exclude on-reservation Native American subsistence fishers, who do not need

licenses to fish on tribal waters; however, off-reservation Native Americans would not be excluded

in states where they are required to have state fishing licenses. Also excluded would be those who

fish or hunt illegally and those who do not require a license, such as children and seniors. The sample

population drawn from license files will consist of fishers or hunters and perhaps their families and

friends, but there is no way to preselect respondents who consume fish from a particular waterbody.

A typical mail survey includes an initial mailing to all respondents, followed by one or more followup mailings to nonrespondents after a specified interval. The first mailing should consist of a cover

letter, a questionnaire with a unique respondent number, a postage-paid return envelope, and perhaps

an inducement to participate in the survey. The cover letter should begin with a brief explanation of

the purpose of the survey. The letter should also stress the confidentiality of the response. The

respondent number on every questionnaire should be used to check off the name from the mailing list

so that nonrespondents can be identified for future mailings; for confidentiality purposes, the names

should not be included on the questionnaire itself. In the most common sequence for addressing

nonrespondents, the four-wave Dillman Method, the initial survey is followed by a postcard reminder,

then a second survey with a new cover letter reiterating the purpose of the survey and indicating that

no response was received from the first mailing (Dillman, 1978; Salant and Dillman, 1994). A final

postcard is sent if no response is received. Another approach is to send out a second survey with a

new cover letter to nonrespondents approximately 3 weeks after the first mailing. A third mailing,

which Pollock et al. (1994) recommend be by certified mail, may be sent out 4 weeks after the second

mailing, again only to nonrespondents. Multiple mailings are important for reducing the nonresponse

rate and its associated bias. Shorter time periods than those described above might be desirable

(Knuth and McMullin, 1996).

Nonresponse bias can be checked by using the telephone or by sending a very brief survey on a

postcard with prepaid postage. Another method of evaluating nonresponse bias is to compare data

from surveys returned early with data from surveys returned much later. Greater bias in the

respondents’ profile can result because effort is involved in completing the survey. This means that

respondents can be either more highly motivated for some personal reason, incentive, or interest in

health and contamination issues and more likely to return the completed survey or, conversely, less

motivated because of indifference or mistrust of those conducting the survey, leading to a low

response rate.

Estimating consumption over an entire year by using mail surveys is a relatively difficult matter. The

respondent’s recall over that period of time is likely to be incomplete. Ideally, respondents would be

surveyed during different times of the year to minimize the recall period. This approach might work

relatively well for the mail survey method, particularly if respondents are screened in the first mailing

for their degree of cooperativeness. Alternatively, the rolling cohort approach described in Section

4.2 can be used.

Questions in a mail survey can be more complex and technical than those in interviews because the

answer period is not time-constrained and the respondent can seek answers from other sources. Draft
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

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questions should be reviewed carefully for ambiguity because of the lack of direct personal interaction

(see Section 4.2 for discussion and references).

4.6.4 Specific Issues for Statistical Sampling and Analysis: Mail Survey

Nonresponse bias in mail surveys can frequently be large according to Brown (1991). However, West

(1989) found that nonrespondents ate nearly as much fish as respondents; when the consumption rate

was adjusted for nonrespondents, it was almost equal to the regional average found in numerous other

studies. The magnitude of this bias can be analyzed statistically if information about the

nonrespondents can be obtained. Such a followup survey is commonly conducted by telephone, but

other methods are possible (Fisher, 1996). Nonresponse bias (B) is represented by the following

equation:

B = (W )(Y - Y ) 2 1 2

where W is the fraction of nonrespondents and Y and Y are the population means for respondents 2 1 2

and nonrespondents, respectively. An estimate of Y comes from the mail survey. If an estimate of 1

Y can be obtained through a telephone survey, the results of the mail survey can be corrected for 2

nonresponse bias (Pollock et al., 1994). For information regarding the analytical treatment of bias,

the reader is referred to texts such as Biemer et al. (1991), Scheaffer et al., (1990), or a statistician.

Other types of bias can be associated with poor selection of the survey sample and poor questionnaire

design. The importance of understanding the characteristics of the target population and how this can

affect the survey results is described in Section 3.3.1.

4.6.5 Specific Issues for QA/QC: Mail Survey

An efficient means of tracking the status of all questionnaires and respondents is an important QA

mechanism for mail surveys. Software programs for administering mail surveys are reviewed by

Larson and Jester (1991). QC procedures used during personal contact survey methods, such as field

audits, cannot be used for mail surveys because the respondents “collect” the data themselves by

completing the questionnaire. After the questionnaires are returned, entry into some sort of data

processing software is typically necessary. QC procedures for data entry are described in Section 4.4.

4.7 Diary

4.7.1 Advantages

• The diary approach can assess region-specific consumption rates if respondents are

selected appropriately.

• Diaries can provide data over long periods of time for particular subpopulations of

concern if such subpopulations have been appropriately preselected.

• This approach is less expensive than personal interviews.

• The diary approach can be used for respondents inaccessible by telephone.
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

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• Large numbers of respondents may be included.

• This approach results in minimal recall bias, although other potential sources of error or

alterations in record keeping can occur.

• Visual aids (geographic, meal size) can be added to improve accuracy.

4.7.2 Disadvantages

• Interviewers must be trained to teach the respondents how to complete the diary.

• Using the diary approach requires respondent literacy, a high degree of motivation, and

constant monitoring to maintain consistency in the data collected.

• The act of keeping records can affect dietary practices.

• Depending on respondent involvement, there can be a high degree of failure in daily

recordkeeping.

• There can be language barriers both in setting up respondents and in interpreting their

responses.

4.7.3 Specific Issues for Instrument and Study Design: Diary

The diary approach for measuring fisher participation has been infrequently reported in the literature.

Recently, however, there has been a trend to use the method to measure both fishing participation and

fish consumption (Connelly and Brown, 1996). Various methods have been used to select the fishers

to be surveyed by the diary approach. Fishers can be contacted by mail, by telephone, or at the

fishing site. Even if material is distributed at the fishing site, the diary approach is considered “off

site” because it uses self-reporting of data. Diaries are also used for hunting participation and could

be used for wildlife consumption as well.

The diary approach can be used to collect either single-trip or multi-trip records. Diaries are normally

used when information about more than one trip is needed. Fishers and hunters may be issued diaries

to record their catch and consumption practices over a specified period of time. Diaries are usually

returned by mail at the end of the study period. For single trips, catch cards may be issued to persons

at the fishing or hunting site to record their catch and estimate their consumption based on a single

day of fishing or hunting. They are handed out to fishers or hunters at the beginning of their fishing

or hunting trip and either collected at the end of the day or mailed in later (Pollock et al., 1994).

Because participants are not required to recall fishing or hunting and fish or wildlife consumption but

can record it directly, recall errors are minimized, assuming that diaries are completed on a regular

basis. Some recall period is inevitable, however, because some people will forget to record their data

until reminded. Typically, the diary method yields much lower estimates of fishing and fish

consumption than either mail or telephone surveys (Thompson and Hubert, 1990; Connelly and

Brown, 1995).
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

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The structure of the diary is slightly different from the structure of the questionnaires developed for

other survey approaches. Because entries are usually repeated over time, not all questions need to be

answered for each entry. Demographic questions are asked only once. Charts or tables can be used

to report catch rates and consumption patterns. Because of higher levels of complexity, diary

instructions are more thorough than typical questionnaire instructions.

The study period must be long enough to provide the data necessary for consumption estimates, but

not so long as to burden respondents. Estimating consumption over a entire year by using a diary is

a relatively simple matter if participants are willing to participate for that long. The degree of

cooperativeness can be gauged during initial contact. An alternative to keeping the same participants

for the entire study would be to use the rolling cohort method (Section 4.2) to reduce the time

individuals are asked to keep diaries and eliminate participant burnout.

Questions in a diary can be more complex and technical than those in interviews because the answer

period is not time-constrained and the respondent can seek answers from other sources. However,

the questions should not be so complex that the participant does not want to complete the diary on

multiple occasions. Draft questions should be reviewed carefully for ambiguity because of the lack

of direct personal interaction.

4.7.4 Specific Issues for Statistical Sampling and Analysis: Diary

If catch cards or diaries are handed out at a target waterbody, planning for sampling consists of

determining specific sites and times to hand them out. If the survey instruments are mailed out, living

close to the waterbody could be a criterion for selecting respondents. Sampling frames may be

constructed using a variety of probability sampling methods, including (1) simple random sampling

without replacement, (2) stratified random sampling, (3) systematic random sampling, (4) two-stage

(cluster) sampling, and (5) nonuniform probability sampling. These methods as applied to fisher

surveys are discussed in Pollock et al. (1994). Bias in the diary survey approach can be associated

with poor selection of the survey sample and poor questionnaire design. The importance of

understanding the characteristics of the target population and how they can affect the survey results

is described in Section 3.3.1. For information regarding the analytical treatment of bias, the reader

is referred to texts such as Scheaffer et al. (1990) and Biemer et al. (1991) or a statistician.

4.7.5 Specific Issues for QA/QC: Diary

Field audits and other QC procedures used in personal contact survey approaches cannot be used for

diaries and catch cards because data are self-reported by the respondents. Periodic phone contacts

might be useful to provide oversight and motivation to complete the diaries (Connelly and Brown,

1995). Data obtained on the phone can later be compared with data in the diaries.

Once the diaries are returned, entry into some sort of data processing software will typically be

necessary. QC procedures for data entry are described in Section 4.4.
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-19

4.8 Personal Interview

4.8.1 Advantages

• Personal interviews can assess region-specific consumption rates by targeting the

waterbody or residence of the respondent.

• This approach can also identify specific subpopulations of concern by obtaining data

from known contaminated fishing/shellfishing sites or working with community agencies

to identify potential respondents.

• Interviewees’ responses can be augmented with first-hand observations of the

respondents and the interview sites.

• Literacy and language barriers might be more easily overcome using this approach.

• Recall bias can be minimized by providing appropriate visual aids (for species and

portion or meal size) or by basing the survey on the fish or wildlife caught at the time of

the interview.

• This approach has a high rate of success for completing interviews because of personal

contact. Interviewers can be trained to clarify confusing questions or neutrally probe for

answers.

• Verification of information is comparatively easy, especially if data collected are based

on the actual catch of the day. It is also relatively easy to use special techniques such as

visual aids and probing.

4.8.2 Disadvantages

• The number and complexity of survey questions might need to be limited so that surveys

can be performed quickly, depending on the respondent’s availability and interest.

• Personal interviews are the most costly approach, requiring the coordination, hiring,

training, and close supervision of interviewers and field staff at more than one location,

as well as additional paperwork to control the fieldwork and processing operations

(U.S. EPA, 1984).

• For on-site personal interviews, responses to questions about consumption are

hypothetical because consumption of the catch has not yet occurred and it is unknown

how many fish will be given away and consumed by the friends or family of the fisher.

In addition, these responses measure only the intent to consume, which might not be an

accurate representation of the true consumption rate. Follow-up studies might be needed

to understand the relationship between the intent to consume and actual consumption.

As preliminary estimates, the consumption estimates from creel surveys are conservative

(potentially overestimating consumption for the angling population).
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-20

4.8.3 Specific Issues for Instrument and Study Design: Personal Interview

Various methods have been used to select the fishers or hunters to be interviewed. The sample may

consist only of fishers or hunters or may include members of their households who could later be

separated into subgroups of the sample unit (U.S. EPA, 1983). On the regional or local level, lists

of fishing or hunting license holders might be used to obtain stratified samples based on a particular

type of license or geographic reference, such as counties located close to the waterbody in question.

This method might exclude on-reservation Native American subsistence fishers, who do not need

licenses to fish on tribal waters, or urban subsistence fishers, who might not have obtained licenses.

Intercept or on-site interview approaches may attempt to question everyone, interview only those who

have caught fish or wildlife at the time (nonuniform sampling), or randomly select fishers or hunters

to be questioned. Depending on the objectives of the survey, other strategies might be required to

obtain samples of recreational and subsistence fishers or hunters.

Once the population has been identified, the location of the interviews should be selected. Locations

can be off site or on site, where “site” refers to the waterbody in question (Pollock et al., 1994). Offsite personal interviews are usually based on sampling from a list of fishers or hunters (e.g., license

holders), and such an interview usually takes place in the respondent’s home. Clustering methods can

be employed for off-site surveys to interview a number of respondents in one location. This technique

can lower the costs of the interview survey and may be particularly effective if incentives are offered

to respondents to meet at a central location. On-site approaches are based on sampling from a list of

fishing or hunting places and times. Fishers are interviewed while in the act of fishing or just as they

come off the water. On-site approaches allow more information to be verified by the researcher. For

example, researchers in the field are less likely than fishers to make mistakes about the identification

of fish species. A specialized form of on-site interview, the creel survey, is discussed in Section 4.9.

The accuracy of recall is inversely proportional to the amount of time for which recall is required.

Off-site interviews often include longer recall periods than on-site interviews. For example, fishers

found at fishing sites may, on the average, fish more frequently than fishers contacted off site and

should be able to provide estimates of fish consumption more readily over a shorter period of time

(including the interview day). Ideally, the same respondents would be interviewed during different

times of the year to minimize the recall period. This approach is often not financially practical.

Alternatively, the rolling cohort method (Section 4.2) may be used to interview different respondents

over the course of the year. This method could be financially practical if only a small group of

interviewers were trained and employed over the period of the study, though it might be financially

impractical if trying to cover a large study area. Although the results might be equally reliable, the

consumption rates obtained could differ. Each of these methods presents different problems and

introduces different biases. For example, interviewing the same respondents during a long period

might unconsciously affect their consumption since they know they are participating in a consumption

survey. Again, the reasons for conducting the survey and the survey objectives are important in

determining which approach might be used.

As with all approaches, meal size estimates are subject to considerable error. Questions on meal size

are often accompanied in a personal interview by models of a typical fillet meal (e.g., 3 oz, 5 oz, or

8 oz). These visual cues are very helpful in triggering a more accurate response from the respondent.

It is important to note that the most helpful visual aids represent the species that are being caught or

are being asked about in the questions and the size and shape of the portions being eaten (Save San
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-21

Francisco Bay Association, 1995). For example, commonly eaten portions of eel, shark, and bass

vary greatly in shape, size, and weight. Since fish caught in small or constricted waterbodies do not

grow as large as fish caught in bays and oceans, showing an 8-oz fillet model or picture might not be

appropriate for waterbodies where fish of that size are not routinely caught. An fisher could also be

asked to describe the species and size of fish routinely caught and eaten and approximately how much

of the fish each household member eats (e.g., one-half of the white meat from a 12-inch perch, both

fillets of an 8-inch catfish). For on-site interviews in which the fish can be identified and measured

(length and breadth at belly), it is possible to relate meal size to the size of the fish if it is to be

consumed (Allen et al., 1996). The question wording and responses should be limited so that

reporting of ranges (e.g., 2 to 4 meals per week, 6 to 8 oz per meal), which would be difficult to deal

with in the analyses, is eliminated. The respondent should be asked to provide a best estimate of the

average meal size consumed and frequency for the recall period needed.

4.8.4 Specific Issues for Statistical Sampling and Analysis: Personal Interview

For on-site interviews, sampling consists of determining specific sites and times for interviewing, and

methods for selecting interviewees. For off-site interviews, living close to the waterbody could be

a selection criterion. Sampling frames may be constructed using a variety of probability sampling

methods, including (1) simple random sampling without replacement, (2) stratified random sampling,

(3) systematic random sampling, (4) two-stage (cluster) sampling, and (5) nonuniform probability

sampling. Sampling frames that consist only of sites or times are also possible. These methods as

applied to fisher surveys are discussed in Pollock et al. (1994). Bias in the personal interview

approach can be associated with poor selection of the sample and poor questionnaire design. The

importance of understanding the characteristics of the target population and how these characteristics

can affect the survey results are described in Section 3.3.1. For information regarding the analytical

treatment of bias, the reader is referred to texts such as Scheaffer et al. (1990), Biemer et al. (1991),

or a statistician.

4.8.5 Specific Issues for QA/QC: Personal Interview

For both on-site and off-site interviews, the supervisor can be present with the interviewer for some

of the interviews to ensure that the questionnaire is being completed in accordance with the survey

design. During these field audits, the supervisor should also check the data entry forms that the

interviewer completes for transcription or other errors. The interviewer can conduct a brief selfreview after each interview or at the end of the day. Data entry errors can be corrected more easily

if they are caught while the events of the interview are still fresh in the interviewer’s memory. Data

from personal interviews are typically entered into a computer database. QC procedures for data entry

are described in Section 4.4.

4.9 Creel Survey

4.9.1 Advantages

• Creel surveys, as a personal interview approach, can assess region-specific consumption

rates by targeting specific waterbodies.
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-22

• This approach can also identify specific subpopulations at high risk by obtaining data

from actual fishers at known contaminated fishing/shellfishing sites.

• Creel surveys can provide first-hand observations of the respondents, their fishing

activities and behavior, their catch, and the interview sites.

• Recall bias can be minimized by providing appropriate visual aids (for species and

portion or meal size) and by basing the survey on the fish caught at the time of the

interview.

• The rate of success for completing interviews is high because of personal contact.

• Verification of information is comparatively easy, especially if data collected are based

on the actual catch of the day. It is also relatively easy to obtain sensitive information

and to use special techniques such as visual aids and probing.

• Because creel surveys are often regularly conducted by state and tribal agencies for

fishery management purposes, questions on fish consumption can be added at relatively

little additional cost.

4.9.2 Disadvantages

• The number and complexity of survey questions must be limited so that surveys can be

performed quickly.

• Interviewers might encounter language barriers.

• Creel surveys are costly because they require the coordination, hiring, training, and close

supervision of interviewers and field staff for quality control, as well as additional

paperwork to control the fieldwork and processing operations. Creel surveys consisting

of questions added to ongoing creel survey activities are less expensive.

• Responses to questions about consumption are hypothetical because consumption of the

catch has not yet occurred and it is unknown how many fish will be given away and

consumed by the friends or family of the fisher. In addition, these responses measure

only the intent to consume, which might not be an accurate representation of the true

consumption rate. Follow-up studies might be needed to understand the relationship

between the intent to consume and actual consumption. As preliminary estimates, the

consumption estimates from creel surveys are conservative, potentially overestimating

consumption for the fishing population.

4.9.3 Specific Issues for Instrument and Study Design: Creel Survey

The creel survey approach is used by fishery managers to obtain harvest data collected on site, from

single fishers (hook and line, castnet, clam rake, etc.) or from larger-scale commercial-type operations

(trawl, gill nets, etc.) that obtain fish for a specific community (see Gutherie et al., 1990). Although

questions on fish consumption practices are not normally included in a creel survey, this information
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-23

can be readily obtained if desired. If surveys are regularly conducted as part of agency management

programs, questions on fish consumption may be added for relatively little additional cost.

Two types of creel survey methods can be distinguished—access point surveys and roving creel

surveys. The characteristics of the two types of surveys are given in Table 4. The access point survey

is preferred when entry points into the fishery are relatively few and well defined. When access to

the fishery occurs at too many points to be accommodated in a traditional access point design, the

roving method might be preferred.

Questions on meal size are often accompanied in a personal interview by models of a typical fillet

meal (e.g., 5 oz or 8 oz). These visual cues are very helpful in triggering a more accurate response

from the respondent. It is important to note that the most helpful visual aids represent the species that

are being caught or are being asked about in the questions and the size and shape of the portions being

eaten. For example, commonly eaten portions of eel, shark, and bass vary greatly in shape, size, and

weight. Since fish caught in small or constricted waterbodies do not grow as large as fish caught in

bays and oceans, showing an 8-oz fillet model or picture might not be appropriate for waterbodies

where fish of that size are not routinely caught. An fisher could also be asked to describe the species

and size of fish routinely caught and approximately how much of the fish each household member

eats (e.g., one-half of the white meat from a 12-inch perch, both fillets of an 8-inch catfish). For onsite interviews in which the fish can be identified and measured (length and breadth at belly), it is

possible to relate meal size to the size of the fish if it is to be consumed (Allen et al., 1996). The

question wording and responses should be limited so that reporting of ranges (e.g., 2 to 4 meals per

week, 6 to 8 oz per meal), which would be difficult to deal with in the analyses, is eliminated. The

respondent should be asked to provide a best estimate of the average meal size consumed and

frequency for the recall period needed.

Table 4. Characteristics of Creel Survey Methods

Characteristic Survey Survey

Access Point Roving Creel

Takes place on site, physically on shore or water yes yes

Fishery has countable number of access sites yes no

Specific locations on waterbodies can be targeted no yes

Sampling events are chosen with probability methods yes yes

Fishers using sites are representative of all fishers using the fishery yes no

Fishers fishing longer are sampled disproportionately more than no yes

short-term fishers

Fishers are interviewed as they leave the fishery yes no

Fishers are counted while they are still fishing no yes

Information gathered on effort and harvest is unbiased yes no

Harvest can be examined by the creel clerk yes yes

Source: Pollock et al. (1994).
4. INSTRUMENT AND STUDY DESIGN AND IMPLEMENTATION

4-24

4.9.4 Specific Issues for Statistical Sampling and Analysis: Creel Survey

Access sites must be selected in a statistically sound manner. Statistical considerations are perhaps

more profound for surveys in which fishing effort is calculated, but fish consumption might also vary

with the characteristics of the access site. For waterbodies with a small number of sites, the traditional

one-site-per-day approach might be suitable. For waterbodies with many access sites, the bus route

method might be more appropriate. This method entails numerous access sites being treated as a

group that is sampled during one or more days. The survey route is analogous to a bus route with

stops at designated places (access sites) on a predetermined time schedule. Examples of scheduling

both traditional and bus route access surveys are provided in Pollock et al. (1994).

It should be noted that creel surveys are likely to target persons who consume more fish than the

general population and therefore estimates of fish consumption by fishers obtained from creel surveys

should not be applied to the general population. A number of statistical concerns are peculiar to creel

survey data. The reader is advised to consult Lester et al. (1991) and Pollock et al. (1994) for more

information on this topic.

Bias in creel surveys can be associated with the time of year, time of day, and length of the interview

(affecting the proportion of the angling population that could actually be sampled for a fixed level of

effort). These sources of bias are associated with poor sample selection and poor questionnaire

design. The importance of understanding the characteristics of the target population and how this can

affect the survey results is described in Section 3.3.1. For information regarding the analytical

treatment of bias, the reader is referred to texts such as Biemer et al. (1991), Scheaffer et al. (1990),

or a statistician.

4.9.5 Specific Issues for QA/QC: Creel Survey

For both on-site and off-site interviews, the supervisor can be present with the interviewer for some

of the interviews to ensure that the questionnaire is being completed in accordance with the survey

design. During these field audits, the supervisor should also check the data entry forms that the

interviewer completes for transcription or other errors. The interviewer can also conduct a brief selfreview after each interview or at the end of the day. Data entry errors can be corrected more easily

if they are caught while the events of the interview are still fresh in the interviewer’s memory. Data

from creel surveys are typically entered into a computer database. QC procedures for data entry are

described in Section 4.4.
5. SUMMARY

5-1

SECTION 5

SUMMARY

Fish consumption surveys are typically conducted using one or more of the approaches described in

this document. Each approach has strengths and weaknesses, as described in Tables 2 and 3 and

Section 4. Which survey approach is appropriate depends on (1) the objectives of the survey, (2) the

population being surveyed, and (3) the resources available for the survey. During the planning of the

survey, the trade-offs between data desires, data needs, data quality, survey length, representativeness,

survey cost, and other factors must be taken into consideration. Usually, one or more of these factors

will limit what the survey can expect to accomplish. Understanding these problems early in the

planning process can lead to the development of the most appropriate survey for the problems

presented and the information needed.

A common objective of recent surveys is to characterize subpopulations at the higher end of the

consumption scale. Persons in these groups might be at greater health risk if the fish or wildlife they

consume are from contaminated waterbodies. Ease of access to persons in certain subpopulations

differs in the various methods. On-site interviews are more likely to reach subsistence/recreational

fishers or hunters, who might not be licensed, but more detailed data might be obtained by diaries and

written questionnaires. Pilot studies might be necessary to determine whether the proposed study

design can reach a statistically valid number of respondents in the target population.

The process of developing a consumption survey is time-consuming and might require the help of

various professionals, including fisheries biologists, risk assessors, epidemiologists, statisticians, and

survey and human dimensions specialists. Essig and Holliday (1991) present a case study describing

how the National Marine Fisheries Service developed one survey. States, tribes, and others who are

planning to conduct consumption surveys are urged to solicit help from persons who have previously

performed surveys so that costly pitfalls can be avoided.

Appendix A contains information on a number of consumption surveys (primarily for fish). Several

examples of recent survey instruments are presented in Appendix B. The reader should note that these

are examples only and no endorsement by U.S. EPA is implied. They are provided to illustrate the

diversity in survey approaches, instruments, and information needs that have been addressed in

various consumption surveys. The reader should consult the report cited for each survey to

understand the underlying hypotheses and objectives that survey instrument was developed to meet.

Contact information for obtaining copies of these survey reports is provided in Appendix A.

The reader is again advised that this document and the documents Guidance for Assessing Chemical

Contamination Data for Use in Fish Advisories, Volume 1: Fish Sampling and Analysis (released in

1993 and revised in 1995), Volume 2: Risk Assessment and Fish Consumption Limits (released in

1994 and revised in 1997), Volume 3: Risk Management (released in 1996), and Volume 4: Risk

Communication (released in 1995) are offered as guidance only and are not regulatory requirements.

EPA recommends that these guidance documents be used together since no one volume provides all

the necessary information to make decisions regarding the issuance of consumption advisories.
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Tarrant, M.A., and M.J. Manfredo. 1993. Digit preference, recall bias, and nonresponse bias in self reports

of angling participation. Leisure Sci. 15:231-238.

Thompson, T., and W.A. Hubert. 1990. Influence of survey method on estimates of statewide fishing activity.

North Amer. J. Fish. Manage. 10:111-113.

Tukey, J.W. 1977. Exploratory Data Analysis. Addison-Wesley Publishing Company, Reading,

Massachusetts.

U.S. EPA. 1983. Survey Management Handbook. Volume I: Guidelines for Planning and Managing a

Statistical Survey. EPA-230/12-84-002. U.S. Environmental Protection Agency, Office of Policy,

Planning, and Evaluation, Washington, DC.

U.S. EPA. 1984. Survey Management Handbook. Volume II: Overseeing the Technical Progress of a Survey

Contract. EPA-230/12-84-002. U.S. Environmental Protection Agency, Office of Policy, Planning, and

Evaluation, Washington, DC.

U.S. EPA. 1989. Assessing Human Health Risks from Chemically Contaminated Fish and Shellfish: A

Guidance Manual. EPA-503/8-89-002. U.S. Environmental Protection Agency, Office of Marine and

Estuarine Protection/Office of Water Regulations and Standards, Washington, DC.
REFERENCES

Ref-5

U.S. EPA. 1992. Consumption Surveys for Fish and Shellfish: A Review and Analysis of Survey Methods. EPA

822/R-92-001. U.S. Environmental Protection Agency, Office of Water, Washington, DC.

U.S. EPA. 1996a. Guidance for Assessing Chemical Contaminant Data for Use in Fish Advisories. Volume

II. Risk Assessment and Fish Consumption Limits. Supplement A. Exposure Assessment. EPA-823-B-96-

004. U.S. Environmental Protection Agency, Office of Water, Washington, DC.

U.S. EPA. 1996b. National Listing of Fish and Wildlife Consumption Advisories, Version 2.1. EPA/823-C96-011. U.S. Environmental Protection Agency, Office of Water, Washington, DC.

U.S. EPA. 1997a. Guidance for Assessing Chemical Contaminant Data for Use in Fish Advisories. Volume

II. Risk Assessment and Fish Consumption Limits. 2nd edition. EPA-823-B-97-009. U.S. Environmental

Protection Agency, Office of Water, Washington, DC.

U.S. EPA. 1997b (in prep). Ambient Water Quality Criteria Derivation Methodology for the Protection of

Human Health - Technical Support Document. U.S. Environmental Protection Agency, Office of Water,

Office of Science and Technology, Washington, DC.

Vaske, J.J., et al. 1996. Response strategy, recall frame and digit preference in self-reports of angling

participation. Human Dimen. Wildlife 1(4):54-68.

Vena, J. 1992. Preliminary findings from the New York State Angler Cohort Study. Perspectives Great

Lakes Program 6:1-5.

Wentland, E.J., and K.W. Smith. 1993. Survey Responses: An Evaluation of Their Validity. Academic Press,

Inc., San Diego, California.

West, P.C., M.J. Fly, R. Marans, and F. Larkin. 1989. Michigan Sport Anglers Fish Consumption Survey.

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for fish consumption advisories. Soc. and Nat. Res. 10:87-96.
APPENDIX A

SUMMARY OF SURVEY METHODS
A-1

SUMMARY OF SURVEY METHODS INFORMATION (Page of 7)

Title of Survey Type of Contact Address/ Phone No. Level of Effort Time Cost 

Survey

A Pretest of an Approach Creel census The following information was 6,077 telephone sur- For a total of 18,800 fish to provide Telephone interviews: to Collection of Marine and telephone given in K.A. Chandler and veys, 1,644 fishermen estimates of the proportional $1.50; SC $1.73; TX $1Recreational Fishing survey G.L. Brown, HSR-PR-78/1-C1, interviewed at 3 loca- distribution of fish caught for an cost for intercept intervData on the East and 25 January 1978, prepared for tions to estimate area (not to determine fish con- given but average numGulf Coasts NMFS sample sizes required sumption rates), estimated 132 interviews per hr: RI 2.

1977 $333,236 (1979)

and number of days days to interview 3,003 fishermen 2.29; TX 2.26; assumed 

in Rhode Island, 120 days for 3,087 hours of interviewing peinterviews in South Carolina, 282days to interview 6,373 in Texas Cost for surveys in thes

states estimated to be

Fishing Effort and Mail survey Eric Swanson Sent out 18,000 About 9 months including setup, Funded through federal Harvest by Arizona's and creel Arizona Game and Fish surveys (10% of data gathering and analysisLicensed Resident census Department registered fishermen);Anglers Phoenix, AZ 33% response 

1980 Ext. 608 

(602) 942-3000 

Commencement Bay Creel census Doug Pierce 5 months in the field 1 year $25,000 primarily to pay Seafood Consumption Tacoma-Pierce County Health collecting data; contract staff Study Department 7 months writing report 

1981 (206) 591-5543

Tacoma, WA 

Fisheries Surveys: Creel census Dan Holder 10-month creel survey 10 months of 12-month creel $9,077 (based on $5.50Altamaha River Georgia Dept. Nat. Resources, using college students, survey wage for surveys)St. Mary's River Game & Fish Div. random samples

1982 (912) 285-6094 1986 

Atlanta, GA 

A Study of Toxic Personal Bruce Ruppel 87 interviews on-site 2 years for entire study Estimate: $50,000 Hazards to Urban interview and NJ Dept. Environ. Protection Funded by the State Recreational Fishermen creel census Trenton, NJ and Crabbers (609) 984-6548

1983
A-2

SUMMARY OF SURVEY METHODS INFORMATION (Page of 7)

Title of Survey Type of Contact Address/ Phone No. Level of Effort Time Cost 

Survey

Evaluation of Methods Telephone and Given in report: Collected data by 3 About 2 years About $21 per participaUsed to Determine mail surveys EPA Environmental Research different protocols, 587 each protocol, excludinPotential Health Risks Laboratory respondents analysisAssociated with Organic Duluth, MNContaminants in theGreat Lakes Basin

1983

Recreational and Personal Mary McCallum 1,643 interviews on site Data collection over a 12-month Grant - $100,000 for saSubsistence Catch and interview and Washington State Division of period, 2 years total supervisorConsumption of Seafood creel census Health,from Three Urban Epidemiology SectionIndustrial Bays of Puget Seattle, WASound (206) 753-5964

1983-1984

Low Income Families' Personal Marie Wendt 40 personal interviews Data collection and analysis - 1 Graduate student thesiConsumption of interview KVRHA over a 2-week time- year funded through Sea GrFreshwater Fish Caught 122 State Street framefrom New York State Augusta, ME 04330Waters

1985

Potential Toxicant Personal Dr. Marsha Landolt 1st year - 4,181 angler 2 years $207,000 Exposure Among interview and University of Wash. interviews; 2nd year - (excluding indirect costsConsumers of creel census School of Fisheries 437 interviews on site Recreationally Caught Seattle, WA at boat ramps Fish from Urban (206) 543-7468 Embayments of Puget Sound 

1983-1987
A-3

SUMMARY OF SURVEY METHODS INFORMATION (Page of 7)

Title of Survey Type of Contact Address/ Phone No. Level of Effort Time Cost 

Survey

Study of Sport Fishing Mail survey Beth Fiore 1,600 surveys mailed About 1 year Estimate of $27,250 and Fish Consumption Wisconsin Division of health 801 returned Habits and Body Burden Madison, WI Levels of PCBs, DDE, (608) 266-6914 and Mercury of Wisconsin Anglers 

1985 

Marine Recreational Creel census Mark Holliday 46,000 intercept Data collection 1 year - data ready Collaboration with 5 staFishery Statistics Survey National Marine Fisheries interviews and 74,000 for distribution within 4 months agencies - $2,000,000 Atlantic and Gulf Coasts Service, NOAA, telephone interviews 

1986 (301) 427-2328 

1987-1989 

Washington, DC (1986)

Relationship of Human Personal Mike Greenwell 299 households, follow- About 2 years Done in-house Levels of Lead and interview or Agency for Toxic Substances up study on 33 Cadmium to the telephone and Disease Registry Public individuals Consumption of Fish survey Health ServiceCaught On and Around U.S. Dept. of Health & HumanLake Coeur d'Alene, ServiceIdaho Atlanta, GA

1986-1987

(404) 639-0700

A Survey of Attitudes Creel census John Hesse 5 interviewers con- 4 months for surveys (1 May to 31 $6,500 and Fish Consumption of Michigan Department of Public ducted 703 interviews Aug) Anglers on the Lower Health 

Tittabawassee River, Lansing, MI Michigan (517) 335-8353 

1987 (8350)

Angler Use and Harvest Creel census James C. Congdon 1⁄2 FTE doing creel 11.5 months Funded with state fundson Fox Lake, Wisconsin DNR Madison survey for entire fishing

1987 (414) 485-3003

Wisconsin Bureau of Fisheries season (1 May-15Mgmt. March, 11.5 months)Horicon County
A-4

SUMMARY OF SURVEY METHODS INFORMATION (Page of 7)

Title of Survey Type of Contact Address/ Phone No. Level of Effort Time Cost 

Survey

Michigan Sport Anglers Mail survey Dr. Patrick West 2,600 surveys mailed 1 year $30,000Fish Consumption and telephone Univ. of Michigan out 4 waves of mailingsSurvey survey School of Natural Resources and follow-up phone

1988

(313) 764-7206 calls for nonresponse(313) 763-2200 bias

New York Statewide Mail survey Nancy Connelly 17,000 mailed out 10 months, total time about 18 Funded by Dept. EnviroAngler Survey Cornell University 3 follow-up mailings months Conserv., Bureau of Fis

1988 (607) 255-2830 10,314 quest. returned

NY State College of Agriculture 200 telephone follow- State of New Yorkand Life Sciences, Fernow Hall ups for nonresponseIthaca, NY bias

Risk Perception and Mail surveys Dr. Barbara Knuth Sample of 188 opinion $38,000 Communication and personal Cornell University leaders, 120 adult and Regarding Chemically interviews Department of Natural teenage farm workers, Contaminated Fish in Resources, Fernow Hall 32 low-income Lake Ontario Fisheries Ithaca, NY residents, 70 fishery 

1988-1989 (607) 255-0349 professionals. 

A Study of the Mail survey Chuck Cox 2,100 surveys mailed 4 months for data collection and $1,500 mailing costs, pConsumption Patterns of Ministry of the Environment out, 1,427 returned analysis time for processing resGreat Lakes Salmon and Water Res. Branch (68% response) Trout Anglers Toronto, CANADA 

1989 

Consumption of Mail survey Ellen Elbert 2,500 mailed out 9 months Client confidential Freshwater Fish by ChemRisk 1,612 returned Maine Anglers 1685 Congress St.

1990

Portland, ME(207) 744-0012
A-5

SUMMARY OF SURVEY METHODS INFORMATION (Page of 7)

Title of Survey Type of Contact Address/ Phone No. Level of Effort Time Cost 

Survey

Risk Perception, Mail survey Dr. John Vena 30,000 licensed anglers 2 years $157,220Reproductive Health State University of New York, contactedRisk, and Consumption Buffalo, NYof Contaminated Fish in (716) 829-2975a Cohort of New YorkState Anglers

1990-1992

Great Lakes Fish Mail survey Dr. Barbara Knuth 8,000 licensed anglers 2 years; mail survey conducted $111,280Consumption Advisories: Cornell University over 3 monthsAngler response to Department of Naturaladvisories and Resources, Fernow Hallevaluation of Ithaca, NYcommunication (607) 255-0349techniques

1990-1992

A Fish Consumption Personal Mary Lou Soscia 513 off-site interviews All surveys conducted in November Not available 

Survey of the Umatilla, Interview Columbia River Inter-tribal Fish in fall and winter 1991- at central locations on each Nez Perce, Yakama, and Commission (CRITFC) 1992 reservation; final report produced in Warm Springs Tribes of 729 NE Oregon St. October 1994the Columbia River Portland, OR 97232Basin (503) 238-0667

1991

Effects of the Health Mail survey Dr. Barbara Knuth Sample of 2,000 2 years; mail survey conducted $41,772 Advisory and Advisory Cornell University licensed anglers. over 3 months Changes on Fishing Department of Natural Habits and Fish Resources, Fernow Hall Consumption in New Ithaca, NY York State Sport (607) 255-0349Fisheries

1991-1992

Michigan Sport Anglers Mail survey Dr. Patrick West 2,450 surveys mailed 18 months $50,000Fish Consumption and telephone Univ. of Michigan out 4 waves of mailingsSurvey survey School of Natural Resources and follow-up phone

1991-1992

(313) 764-7206 calls for nonresponse(313) 763-2200 bias
A-6

SUMMARY OF SURVEY METHODS INFORMATION (Page of 7)

Title of Survey Type of Contact Address/ Phone No. Level of Effort Time Cost 

Survey

Estimating the Diary survey Nancy Connelly 516 diary participants, 2 years $83,085 Sportfishing Participating and Cornell University 2,500 licensed anglers and Consumption of mail survey Department of Natural for mail survey Lake Ontario Fish Resources, Fernow Hall 

1991-1993 

Ithaca, NY (607) 255-2830 

Demographic Variability Creel census Jim Allen 1,244 anglers Surveys took place over one year $138,000 in Seafood Consumption Southern California Coastal interviewed at access Rates Among Water Research Project points; 113 field survey Recreationa Anglers of 7171 Fenwick Lane trips takenSanta Monica Bay Westminster, CA

1991-1992

92683(714) 894-2222

A Survey of Fish and Telephone Ann Anderson 405 interviews Interviews conducted in summer; $25,000 Shellfish Consumption survey Tulane University completed out of 587 about one year for entire study by Residents of the School of Public Health and attempted; up to 4 

Greater New Orleans Tropical Medicine callbacks before Area 1501 Canal St. moving abandoning 

1992 edu

New Orleans, LA 70112 number; 10% of each(504) 588-5397 interviewer’s workacanders@mailhost.tcs.tulane. verified by callback

Angler Attitudes and Mail survey Dr. Barbara Knuth 5,000 licensed anglers 2 years $130,276Behavior Associated with Cornell UniversityOhio River Advisories Department of Natural

1992-1993 (607) 255-0349

Resources, Fernow HallIthaca, NY

Results of a Survey of Personal Robert L. Hiatt 1959 anglers screened, Data collected over 6 months; Not available 

Recreational Marine interviews, QuanTech 1339 interviewed Fishermen to Evaluate followed by (Delaware); 3066 an Approach to Collect telephone anglers screened, 260 Per Person Fish contact interviewed Consumption (Alabama/Mississippi) 

1992 
A-7

SUMMARY OF SURVEY METHODS INFORMATION (Page of 7)

Title of Survey Type of Contact Address/ Phone No. Level of Effort Time Cost 

Survey

Fishing for Food in San Personal Keith Nakatani Pilot study included 69 Not available Not available

Francisco Bay interviews Save San Francisco Bay initial interviews

1993 (510) 452-9261

Association supplemented by 3 in1736 Franklin St. depth interviews withOakland, CA 94612 ethnic fishers

Estimation of Daily Per Personal Lynn Sisk 1,586 interviews 12 months $110,000 Capita Freshwater Fish interviews and Alabama Department of Consumption of Alabama logs Environmental ManagementAnglers (334) 271-7700

1993

Seafood Consumption in Telephone Lynn Dellenbarger 1,100 interviews 1 month Not available 

Coastal Louisiana survey Louisiana State University 

1993 

(504) 388-2751 

Hudson River Angler Personal Hudson River Sloop 336 interviews 4 months $22,619Survey Interview Clearwater

1993 office@clearwater.org

112 Market St.Poughkeepsie, NY 12601(914) 454-7673

Patterns of Harvest and Mail survey Dr. Barbara Knuth 2,000 licensed anglers 1 year $25,000Consumption of Lake Cornell UniversityChamplain Fish Department of Natural

1993-1994 (607) 255-0349

Resources, Fernow HallIthaca, NY

Fish Consumption and Personal Joanna Burger 318 interviews 7 months $35,000 Risk Perception in the interview Rutgers University conducted at access New York/New Jersey P.O. Box 1059 points estuary Piscataway, NJ 08855 

1994

(908) 445-4318burger@biology.rutgers.edu
A-8

SUMMARY OF SURVEY METHODS INFORMATION (Page of 7)

Title of Survey Type of Contact Address/ Phone No. Level of Effort Time Cost 

Survey

Fishing for Food in San Creel Survey Andrew N. Cohen 69 interviews 12 months Not available

Francisco Bay Lori Lee completed, 65 declined

1997 1736 Franklin Street, 4th Floor piers

Save San Franciso Bay to participate;Association conducted at fishingOakland, CA 94612(510) 452-926174212.145@compuserve.com

Children’s Fishing and Mail survey Dr. Barbara Knuth 123 families; diary 2 years $31,107FIsh Consumption and diary Cornell University participation by 53Patterns Department of Natural children

1995-1997 (607) 255-0349

Resources, Fernow HallIthaca, NY
APPENDIX B

EXAMPLES OF SURVEY QUESTIONNAIRES
B-1

Telephone Survey

KCA Research, Inc. 1993. Results of a survey of recreational marine fishermen to

evaluate an approach to collect per person fish consumption. Alexandria, Virginia. 

Prepared for the U.S. Environmental Protection Agency, Office of Science and

Technology, Standards and Applied Science Division, Washington, DC, under

subcontract to Tetra Tech, Inc., Fairfax, Virginia.
B-3
B-4
B-5
B-6
B-7

Mail Survey

P.C. West, J.M. Fly, R. Marans, F. Larkin, and D. Rosenblatt. 1993. 1991-1992 Michigan sport anglers

fish consumption study. Final report to the Michigan Great Lakes Protection Fund and Michigan

Department of Natural Resources. Technical Report No. 6, University of Michigan, School of Natural

Resources Sociology Research Lab, Ann Arbor, MI.
B-9
B-10
B-11
B-12
B-13
B-14
B-15

Mail Survey

B.A. Knuth. 1995-1997. Children’s fishing and fish consumption patterns. (Mail survey

of children’s guardians.) Cornell University, Ithaca, New York. Prepared for New York

Great Lakes Protection Fund.
B-17
B-18
B-19
B-20
B-21
B-22
B-23

Mail Survey

J. Vena. 1992. Preliminary findings from the New York State Angler Cohort Study. 

Perspectives Great Lakes Program 6:1-5.
B-25
B-26
B-27
B-28
B-29
B-30
B-31
B-32
B-33

Diary

B.A. Knuth. 1995-1997. Children’s fishing and fish consumption patterns. (Diary for

children.) Cornell University, Ithaca, New York. Prepared for New York Great Lakes

Protection Fund.
B-35
B-36
B-37
B-38
B-39
B-40
B-41
B-42
B-43

Diary

T.L. Brown and N.A. Connelly. 1991-1993. Estimating the sportfishing participation

and consumption of Lake Ontario fish. Cornell University, Ithaca, New York.
B-45
B-46
B-47
B-48
B-49
B-50
B-51
B-52
B-53
B-55

Personal Interview

CRITFC. 1994. A Fish Consumption Survey of the Umatilla, Nez Perce, Yakama, and Warm Springs

Tribles of the Columbia River Basin. Technical Report 94-3. Columbia River Inter-Tribal Fish

Commission, Portland, OR.
B-57
B-58
B-59
B-60
B-61
B-62
B-63
B-64
B-65
B-66
B-67
B-68
B-69
B-70
B-71
B-72
B-73

Creel Survey

San Diego County Department of Health Services. 1990. San Diego Bay Health Risk

Study: An evaluation of the potential risk to human health from fish caught and consumed

in San Diego Bay. Prepared for The Port of San Diego, San Diego, CA.
B-75
B-76
B-77
B-79

Creel Survey

Fishery Information Management Systems, Inc., and Department of Fisheries and Allied

Aquacultures, Auburn University. 1994. Estimation of daily per capita freshwater fish

consumption of Alabama anglers. Prepared for Alabama Department of Environmental

Management, Montgomery, Alabama.
B-81
B-82
B-83
B-84
B-85

Creel Survey

B. Barclay. 1993. Hudson River angler survey: A report on the adherence to fish

consumption health advisories among Hudson River anglers. Hudson River Sloop

Clearwater, Inc., Poughkeepsie, New York.

B-87
B-88
B-89
B-90
B-91
B-92
B-93
B-94
B-95