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3
Removal Estimation: Alternative Survey
Design and Analysis Method
Angler surveys that are well designed, soundly executed, and care-
fully analyzed with modern statistical methods are crucial for providing
high-quality information on total fisheries-related removals and related
parameters (fishing effort) on which to base sound fisheries management
decisions. As stated in Chapter 2, and now iterated, the important
parameters to estimate from a recreational fishing survey are total
recreational fishing effort, total recreational harvest (kept catch), and
total recreational released catch. Effort (E) is often estimated from one
survey and harvest per unit effort (HPUE) and released catch per unit
effort (CPUE)Released from a second survey with total harvest (H = A +
B1) estimated as:
H = E × HPUE
and total released catch (CR) as:
CR = E × (CPUE)Released
In addition, the fraction of the released catch that dies needs to be esti-
mated in "hooking" mortality (MH) studies. This enables the estimation
of total recreational fishing removals (R), which consists of the kept
catch plus the released catch that dies as:
R = H + CR × MH
57
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58 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
This then becomes the basis of stock assessment models. (See Chapter 1
for the definitions of harvest terms.)
Harvest and total removals need to be measured for species and
species complexes, specific spatial regions, and temporal periods, de-
pending on the management needs involved. Further, total removals need
to be assigned to age or size classes. Also, due to the very different
nature of the for-hire and general fishing sectors, these sectors also have
to be sampled separately using different methods for efficient estimation.
SMALL- TO LARGE-SCALE SURVEYS
FOR SOUND FISHERIES MANAGEMENT
To estimate primarily angler effort and harvest, angler survey design
has received much attention since the 1990s when the American
Fisheries Society commissioned a symposium and a detailed monograph
on the subject (Guthrie et al., 1991; Pollock et al., 1994). The traditional
access and roving surveys developed in the 1960s (Robson, 1960, 1961;
Malvestuto, 1983) for small water bodies (e.g., lakes, reservoirs, trout
streams) were just not suitable for the larger spatial-scale surveys, which
are so crucial in fisheries management. This is especially the case in
marine fisheries management where the unit of management may range
from coastal waters of a small state, to a region involving groups of
states, or even up to the national level.
One traditional survey is the access-point intercept survey. Robson
and Jones (1989) developed a modification called the "bus route design"
and applied it to a small regional-scale fishery in Lake Ontario tributaries
in New York. Related access-point marine surveys at the regional scale
are run in Texas and Oregon, among others that came under the mandate
of this report (see Appendix B). Unfortunately, there are several prob-
lems with using these designs, and without major modification and
enhancement, these problems limit the usefulness of these surveys. There
may be a large number of access points and some may be very small in
size; often there is private access that cannot be sampled using only
public access points, and the spatial scale may be so large that cost
savings may be achieved by using an offsite contact method (e.g.,
telephone). Roving surveys using agents on foot or in boats also become
impractical when it comes to larger spatial scales.
An active area of research involves the design of complex surveys
for even larger regional and national marine fisheries (Dauk and
Schwarz, 2001; Lyle et al., 2002; Henry, 2002; Pollock, 2002; Volstad et
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REMOVAL ESTIMATION 59
al., in press). Often these surveys require a design that uses one survey
for effort and another survey for catch rate. Examples include the pairing
of aerial surveys of effort with access surveys of catch or telephone
surveys of effort with roving surveys of catch. These paired surveys are
known as complemented surveys (Pollock et al., 1994).
One example of a regional survey that uses an important comple-
mented design (aerial and access) is the Georgia Strait Creel Survey.
This survey has been run since 1980 by Fisheries and Oceans Canada for
the Georgia Strait area near Vancouver, British Columbia. It uses aerial
flights to estimate angler effort by taking aerial counts of boats fishing
and expanding these counts. This effort estimate is combined with data
collected by clerks stationed at access points to record catch rates of
individual anglers to estimate total catch. Catch and effort statistics for
this tidal sport fishery are calculated for each month and statistical area,
and for individual species. According to survey results, catch of salmon
species has shown serious declines since 1980 (Hardie et al., 1998; Dauk
and Schwarz, 2001). Surveys with this design also are used by Michigan
on many of its Great Lakes Surveys (Lockwood et al., 2001) and also in
the Delaware River Creel Survey (Volstad et al., in press). The latter
survey was designed to estimate catch for important anadromous species
(e.g., shad, striped bass) in Delaware and Pennsylvania.
Unfortunately, in many settings, there is a need for more information
at much larger regional and even national scales that will require the
abandonment of direct onsite estimation of fishing effort for total cost
reasons. This suggests the possible use of telephoneaccess and
telephonetelephone survey designs (Pollock et al., 1994). This com-
mittee was formed because of a concern for the reliability of a large
spatial-scale telephoneaccess survey, which is what the Marine Recre-
ational Fisheries Statistics Survey (MRFSS) uses (Essig and Holliday,
1991; see Chapter 2). Another national survey run recently in Australia
used a telephonetelephone survey design with anglers contacted repeat-
edly using a panel diary approach (Henry, 2002; Lyle et al., 2002).
The objectives of the Australian survey were to describe the
characteristics of anglers (participation rates, sociodemographics); eval-
uate effort and catch by species, mode, and region; assess economic
impacts in terms of investment and expenditure associated with fishing;
and evaluate awareness and attitudes to fishing-related matters. All salt-
water and freshwater fishing activities were included within the scope of
these surveys, which were comprised of the following components:
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60 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
1) A screening survey designed to identify fishing households and
to invite anglers to participate in the follow-up diary survey
2) The diary survey in which fishing and expenditure activity was
monitored over 12 months through regular telephone contact by
survey interviewers
3) An attitudinal survey administered as a final telephone interview
at the completion of the diary survey
In general, an advantage of the use of telephone surveys is that one
can obtain information on effort and catch rates for anglers not easily
reachable in an onsite survey (typically an access survey). These could
include night anglers and anglers fishing from private docks and jetties.
However, a key concern is that effort and catch-rate data that are self-
reported may contain large measurement errors. These errors may be due
to willful deception, recall bias, prestige bias, or lack of knowledge (e.g.,
species identifications). Lyle et al. (2002) discuss these potential prob-
lems and review the methods that they used to attempt to reduce these
errors to a low level. In the Australian context, it was not feasible to go
to the telephoneaccess design for cost reasons. It is widely known that
there are tradeoffs between survey costs and the precision of the
estimates, but it is also true that methods that reduce bias in the estimates
may be much more expensive. Onsite catch-rate estimates are much
more expensive than offsite self-reported catch-rate estimates (Pollock,
2002). An access survey for catch rate would get around these problems
(Essig and Holliday, 1991), and this was an important reason for the
current MRFSS design.
What are some appropriate combinations of contact methods to use
in particular situations? The spatial scale of fisheries management
decisions will be a crucial component. For some local or regional fish-
eries, the accessaccess surveys may be optimal; whereas, for other
regional surveys, the aerialaccess design may be preferred, and at larger
scales, the telephoneaccess (augmented with special studies) is often the
only practical option for both the general angler and the for-hire sector.
Telephonetelephone surveys, while useful in Australia, will not be
useful in the U.S. marine setting to estimate removals for management
decisions, as there is the need for an onsite interview component in all
surveys. However, telephonetelephone surveys may be useful in special
studies of night and private-access fishing because these modes cannot
be well assessed in the MRFSS (Chapter 2). General questions that
involve policy and economics also could employ telephone panel surveys
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REMOVAL ESTIMATION 61
(Chapter 5). Augmentation of telephone contacts by internet surveys
needs to be considered and will be discussed later in this chapter.
ANGLER SURVEY FRAMES
For estimation of removals and related parameters (effort and CPUE)
for marine recreational fisheries, frame problems are extremely
challenging. A frame is a set of units that are somehow linked to the
population elements of interest. Estimation of a population characteristic
is carried out by sampling units from the frame, identifying the
population elements linked to the sampled units, and measuring the
variable(s) of interest on the population elements. Two standard types of
frames, also discussed in Chapter 2, are list frames and area frames.
A list frame with known undercoverage, but that is inexpensive to
sample, may be combined with an area frame or another complete list
frame that is expensive to sample. Such surveys are called dual-frame
surveys. To illustrate, consider the simplest dual-frame estimator, called
the screening estimator (Hartley, 1962). The general idea is that the list
frame is incomplete; whereas, the area frame is complete, and therefore,
there are two components. The overlap domain (OL) is the list frame,
and the nonoverlap domain (NOL) consists of those members of the area
frame that are not on the list frame. Therefore, assuming simple random
sampling in each frame, an estimate of the population total () would be
the sum of the population estimates for the two domains:
Y^ = Y^OL +Y^NOL
where the usual population total estimator for the list frame is used for
the overlap domain. All units that are on the list frame are screened out
from the area frame, and only the remaining units are used in a standard
estimator to get the nonoverlap domain estimator. There are many
complications when dual frames are used in real surveys, but this
illustrates the general principles. In some of the applications of most
interest here, the complete frame would be a random digit dialing (RDD)
telephone frame (instead of an area frame), and the incomplete list frame
would be a telephone list frame from an angler license file that suffers
from incompleteness.
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62 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
Possible Frames for Effort Estimation
The population characteristic of interest for effort estimates is total
angler effort (e.g., number of angler days, number of angler trips). While
the description of the unit of effort might vary somewhat among angler
modes, the following discussion uses angler days as a surrogate for all of
these units of effort. Angler effort can be assessed by either defining the
population as all fishing days and then counting anglers active on those
days or by defining the population as all anglers and then counting the
days they fished.
The first option is problematic because there is usually no simple
way to count active anglers on a given day. There are a huge number of
ways in which anglers can access the water, though this varies greatly
from region to region. Sampling from area frames of coasts and coastal
waters could be very inefficient, except in certain constrained waters
(e.g., bays, estuaries) in which fishing effort could be assessed through
aerial surveys, as mentioned earlier in this chapter, or other direct
observations (e.g., bar crossings from the Columbia River in the Oregon
Recreational Boat Survey; see Appendix B). Sampling from access-site
list frames is used in some smaller regional surveys to get at effort
through on-the-ground assessments, such as counting boat trailers or
empty marina slips. However, many surveys cover such a large spatial
area that this becomes completely impractical. Other difficulties with
using access-site list frames are discussed further when considering
CPUE estimation through angler intercepts.
The second option of sampling the population of all marine anglers
is currently problematic but offers the best hope for sound future surveys.
It depends on the availability of a list (frame) of the population of all
marine anglers. Such license file lists are available in some states but not
others; in general, states in the northeastern United States (New Jersey
northward) do not have saltwater licenses at all. At the inception of the
MRFSS, license frames were not available in many states and the
MRFSS designers were forced to use a different list frame. Through its
RDD sample, the MRFSS uses a frame of all working landline telephone
numbers in coastal counties. This frame suffers from overcoverage since
not all households contain anglers, undercoverage since some anglers do
not live in coastal counties or they live in coastal counties but do not
have landline telephones (a problem likely to grow as more households
move to only cellular telephones), and duplications since some anglers
live in households with more than one working landline. Overcoverage
leads to severe inefficiency in the RDD sampling effort. Undercoverage
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REMOVAL ESTIMATION 63
in the coastal county frame may lead to serious bias since anglers from
noncoastal counties are likely to have different effort characteristics than
those from coastal counties. An attempt has been made to adjust for this
potential bias using information collected via field intercepts in a pro-
cedure much like a dual-frame survey; however, as mentioned in Chapter
2, this procedure is ad hoc and likely biased.
Other list frames used in sampling the population of marine anglers
include state- or regional-level licensing systems (Washington, Oregon,
and California surveys use such frames). Licenses are linked directly to
the angler population of interest, but license frames can suffer from
overcoverage (e.g., due to out-of-date licensing information), under-
coverage (due to license exemptions or poaching), and duplications.
Overcoverage in the license frame is much less than with RDD so
sampling is potentially far more efficient. Undercoverage is reduced if
license exemptions are minimized. Undetected duplications could be
problematic because anglers with more than one license listing may be
more avid anglers and would be overrepresented in the sample. Clearly,
there is a need for a complete angler registry in all states; these should be
designed rigorously to minimize under- and overcoverage. If license
frames suffer from substantial incompleteness, then dual-frame ap-
proaches could be and should be used to adjust for this incompleteness
rigorously, but this will be more expensive and make the surveys more
complex than if a complete license (registry) file frame were available.
In the for-hire sector, list frames of operators (based on licenses) are
available and being used in telephone surveys in many regions of the
country. The same issues of making sure that these lists have minimal
under- and overcoverage problems are important.
Frames for Catch per Unit Effort Estimation
The population of interest for CPUE estimation is the population of
angler days or trips. This population is, on occasion, accessed through an
area frame of coastal waters, with roving boats visiting fishing vessels,
but this is expensive and impractical in large spatial-scale surveys and
also may be seen as intrusive. As a result, it can be difficult to count and
measure the fish caught accurately. The population is accessed primarily
through a list frame of site days, where sites are documented fishing
access points. (Such site lists are used on occasion for assessing effort, as
noted above.) Site days are selected with guidance from a "pressure
matrix" that indicates expected fishing intensity across site days. Once a
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64 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
site day is selected, field personnel visit the site on that day and attempt
to intercept returning anglers. The field personnel have considerable
latitude in how they go about intercepting anglers. Errors in estimating
the expected fishing intensity and failure to account for expected fishing
intensity in the estimation process can lead to both increased variance
and bias in the CPUE estimates.
The major problem with site list frames is undercoverage. Some
public access points may be missed in the listing procedure, and private
access points are not listed at all. Estimates of CPUE may be biased if
anglers accessing the water from private access points or from little-
known public access points differ in their fishing (e.g., fishing modes,
areas and species targeted, effort and success rate) from those accessing
the water from well-documented public access points. In the for-hire
sector, access-point interviews of anglers also are required, and the same
issue of inaccessible private marinas may apply.
Since expertise on local geography, fishing modes, and species
variation is critical, maintenance and sampling of access-point list frames
for CPUE estimation is best done at a local level. Even with outstanding
local expertise, access-point list frames have a number of potentially
serious deficiencies, as outlined above, and need to be supplemented
with area samples or other dual-frame techniques to get at CPUE for
anglers not accessing the water from listed public access points.
National Registry Frame
This discussion of difficulties with existing frames means that,
barring major advances in technology (such as remote sensing) that
would allow assessment of fishing effort day by day, a much improved
frame for interviewing anglers is needed. Use of the RDD approach in
coastal counties is inefficient, potentially biased, and likely to grow even
worse over time, but it is the only currently viable option in states
without a complete registration of marine anglers to provide a license
frame.
A national registry database built on existing state angler licenses
and augmented with new licenses would be an ideal frame for sampling
marine anglers if it minimized duplications through rigorous and
nationally consistent registration standards, minimized overcoverage
with regular database updates, and minimized undercoverage by
disallowing exemptions. Such a national registry database would yield
considerable efficiency for sampling effort over the current RDD frame.
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REMOVAL ESTIMATION 65
There would be enormous management benefits, cost and interview
savings, and increased quality of the catch estimates obtained.
Some states currently require a license to fish in marine waters but
do not use the associated angler information to conduct effort or CPUE
surveys. This happened in states where the license was developed
principally as a means of revenue generation with little application to
data collection. Because of the associated fee component, these licenses
frequently have numerous exemptions, which reduce their usefulness for
frame development and sampling. For example, in Florida,1 only anglers
fishing from a boat in state waters (or traversing state waters to land fish
caught in the exclusive economic zone) must buy a Florida saltwater
fishing license. Anglers fishing from shore and those over 65 and under
16 are exempt and therefore would not be contacted if the license frame
were used for data collection. Saltwater fishing license requirements vary
by state, as do the exemptions. Therefore, many current license programs
would need to be modified substantially to be suitable as a complete
sampling frame.
The recognized need for a national list frame of anglers is not new,
and several previous reviews have offered similar recommendations
(National Research Council, 2000), but there has been significant resis-
tance from some states to federal involvement in this issue (Box 3.1).
Some fear that the additional cost associated with purchasing a license
will dissuade people from becoming anglers, and those that are now
exempt from license fees likely will resist imposition of the fee if they
are required to purchase a license. Further, in the northeast in particular,
there appears to be a cultural aversion to the basic idea of saltwater
licensing. Still, there are many reasons why a state-level saltwater angler
license would benefit data-collection efforts. Cooperation between the
federal and state governments on a mandatory salt-water angler registry
(or license), with attention to eliminating exemptions in states with
current saltwater licensing and with encouragement to other states to
implement such licenses as quickly as possible, would lead to realization
of those benefits.
The national registry and state survey programs would need addi-
tional funding to establish and maintain this type of database. However,
there also would be large cost savings associated with sampling from this
frame as compared with RDD, where a small proportion of the contacts
reach an angler. An updated, complete registration list would greatly
1 Refer to Florida Fish and Wildlife Conservation Commission (2005) for a full
list of Florida's exemptions.
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66 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
Box 3.1
Lessons Learned from Boating Registration
State fisheries agencies generally believe that the federal govern-
ment lacks sufficient authority for requiring saltwater licenses for those
who land their fish in state sovereignty waters. Because of the delicate
balance of state and federal interests in marine fisheries, implementing a
national saltwater fishing registry continues to be a contentious issue and
significant political will may be needed. However, there are important
lessons to be learned from recreational boating, most notably, boat regi-
stration and numbering. Previous legislative actions for this sector can
serve as model for the statefederal cooperation that will be needed in
establishing a national angler registration.
At one time, some states had recreational boating registration
systems while others did not. Likewise, there were differences in how
each state registered boats, the data they collected from owners, and the
interval in which information was updated. The Federal Boating Act of
1958 (46 U.S.C. 527-527h) gave states the responsibility for registration
and numbering of all undocumented boats after years of benign neglect
by the U.S. Coast Guard. Furthermore, national standards for registration
and numbering were instituted, including what data were to be collected
from boat owners. Deficiencies in boat coverage for numbering and
registration purposes were remedied in follow-up federal legislation
(Federal Boat Safety Act of 1971 [46 U.S.C. 1451 et seq.]). This statute
provided incentives in the form of additional funding for states that
adopted uniform laws; states that failed to do so were penalized by
having a federal numbering and registration system implemented in their
respective state.
Thus, to improve the quality and quantity of survey data on marine
recreational fisheries, there is a need to establish national standards for
existing and proposed state-level saltwater angler licenses or for even-
tually generating a national universe of marine anglers. It is not auto-
matically necessary to establish a national saltwater fishing license to be
administered by the National Marine Fisheries Service (NMFS). There
are notable differences here, and the words are important. Some states
with saltwater licenses may only have to modify the types of data they
collect or expand licensing coverage to anglers previously exempted;
other states may need more convincing. Federal standards should deal
with the exact types of data collected from anglers and should require
that exemptions be eliminated or kept to an absolute minimum.
improve efficiency both in terms of time and cost. It is not assumed that
these savings would cover the entire cost of maintaining such a database.
However, the benefit from the increased quality and quantity of the data
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REMOVAL ESTIMATION 67
will be well worth the extra cost, especially if there is an associated
increase in public confidence with the final estimates. Also, the creation
of such a list will be essential to implementing some of the other
recommendations found in this report.
It is critical that the licensing requirements eliminate exemptions and
noncompliance by segments of the fishing public. Significant efforts to
enforce these registration requirements will be necessary. The statistical
problems arising from any unavoidable incompleteness of the frame can
be addressed in various ways, with the most important one being the use
of a dual-frame approach. This will add additional expense so it is crucial
to minimize undercoverage of the saltwater license frame. Also, the
benefits associated with the angler list frame would be diminished if this
list also included freshwater anglers. Including freshwater anglers in the
same database would reduce the efficiency gained by the implementation
of the registration--unless the data about each angler identifies them
either as a freshwater angler, a saltwater angler, or both.
OTHER SURVEY DESIGNS
Panel Surveys
A panel survey is another methodology that has been used in
collecting recreational fisheries data. One example is the telephone diary
panel survey used in Australia to assess recreational fishing (Henry,
2002; Lyle et al., 2002). This survey used multiple contact telephone
interviews to get both fishing effort and harvest rate over a one-year
period. Panel surveys should be considered for the telephone survey
portion of the MRFSS (National Research Council, 2000). A rotating
panel design, with membership in the panel lasting one year (six waves),
might be a reasonable approach for the MRFSS.
Panel surveys collect data from the same individuals at regular
intervals of time. This design also is referred to as rotation sampling. The
main purpose of such a design is that it produces more efficient estimates
of change from one time period to the next. To see this, yt is defined as
the parameter of interest at time t (e.g., total fishing effort in a given
wave) and yt+ as the total in the next time period. These totals are esti-
1
mated by y^t and y^t , and the change (t^
+1 ,t+1) is:
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72 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
methods to estimate the number released are needed. Use of observers in
boat-based fisheries to get direct estimates of numbers released could be
explored. However, there are problems with releases being different if
observers are present. Also, released catch are usually not incorporated
into catch estimates, even though there is the potential that high hooking
mortality could result in high mortality of the released catch. Released
fish mortality estimation from cage studies and tagging studies needs
more attention because auxiliary data on depth caught and release
condition are hard to collect but are important.
For-Hire Sector Survey Design
For some fisheries, the for-hire sector is responsible for taking most
of the recreational catch, which is, in some cases, the majority of the total
catch (Coleman et al., 2004). There are at least 10,000 registered charter
vessels in the United States. In Alaska, 1,400 charter vessels landed over
60 percent of the reported recreational catch of halibut and lingcod in
recent years, with this percentage reaching over 70 percent in southeast
Alaska.2 In the Gulf of Mexico, charter vessels land an average of 70
percent of the recreational red snapper catch (35 percent of the total
directed catch), and as a result, a charter vessel moratorium program is
being implemented to limit the potential catch from this sector (Gulf of
Mexico Fishery Management Council, 2004a). Due to the large potential
contribution of this sector to total removals, it is important that it be
monitored accurately.
Several years ago, it was recognized that the MRFSS was not
effective for assessing the for-hire sector, and consequently, there are
now alternative surveys in place in most states for collecting data from
the for-hire sector. The most important of these are the For-Hire Survey
and the Party Charter Survey (see Appendix B). Both of these surveys
are designed to ascertain fishing effort and CPUE data, just as the
original MRFSS aims to do. However, the major change is that effort is
determined from boat directory telephone lists instead of the RDD frame.
Use of these list frames is much more efficient than use of the RDD
frame. This allows for a greater sample size specific to this sector. In
addition, the potential for bias is eliminated since fishing effort for both
2 Personal communication, Allen Bingham, Alaska Department of Fish and
Game, Sportfish Division, Anchorage.
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REMOVAL ESTIMATION 73
local and nonlocal anglers can be estimated directly from the charter
companies. There is no need to adjust for effort by out-of-frame anglers.
The current surveys are capable of monitoring the for-hire sector
better than what was achieved through the MRFSS. However, design
issues associated with these surveys still exist. The estimation of CPUE
still relies on intercept sampling at points of landing; therefore, they are
still subject to the problems discussed in the previous chapter about
interviewer choice. In fact, intercept issues for this sector may be an even
bigger problem since cluster effects arise from multiple anglers partic-
ipating in the same fishing experience. These effects can be significant
and must be accounted for in the estimation for this fishing mode.
Another difficulty in surveying the for-hire sector is that operations range
from very small to very large, with some being transient. License frames
for this sector are likely to suffer from some incomplete coverage,
especially for the small or transient operations.
An alternative to the current sampling surveys is the use of
mandatory logbooks or diaries of all the fishing effort and catch on for-
hire boats, as a condition of the vessel's license. The captain would be
responsible for filling out the logbooks as fishing progressed each day,
and he or she would be required to turn the logbooks in on a timely basis
as a condition for continued licensing. Having the license of the vessel
tied to the logbook requirement would be the mechanism to achieve a
complete list frame for this sector. Therefore, a census of this sector
theoretically is possible because the population of charter and head boats
is defined more easily than that of the total angler population. Also, the
captains and crew generally have a greater knowledge of the local fish
species and could provide more reliable catch data, including species
identification and the location of catch.
The question of whether to use a survey or census for the for-hire
sector is not a new one. In 2001, the Recreational Technical Committee
(RTC) of the Atlantic Coast Cooperative Statistics Program (ACCSP)
undertook a one-year assessment of three programs designed to measure
the fishing activity of the for-hire sector of the South Carolina marine
fishery (Ditton et al., 2002). The purpose was to provide information for
determining the best and most acceptable method of collecting data from
the for-hire sector that could be adopted as a standard by ACCSP. They
reviewed (1) the MRFSS; (2) the mandatory South Carolina Charter
Logbook Survey, combined with the NMFS Headboat Logbook Survey;
and (3) the NMFS Vessel Directory Telephone Survey (VDTS), com-
bined with the MRFSS intercept component (with augmented sampl-
ing)--the precursor design for the For-Hire Survey.
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74 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
RTC noted marked improvements with VDTS and the South
Carolina logbook methods when compared to the MRFSS (Ditton et al.,
2002). RTC found that the advantages of the logbook program were that
it had the most credibility of the three methods with the public, it had the
best timeliness of data availability, and it had the most complete
sampling frame and coverage. It also found that the logbook program
sampled 99 percent of the for-hire vessels in South Carolina and was
successful because it was mandatory, enforceable (with measurable
enforcement actions), and financially sustainable. The disadvantages of
the South Carolina Charter Logbook Survey were the possibility of an
incomplete sampling frame because of potential rogue vessels,
underreporting on vessels, and lack of biological sampling dockside.
RTC provisionally recommended the VDTS program over the logbook
program because of implementation issues it anticipated for a coastwide
program--primarily lack of funding and commitment of agencies to
enforcement and validation. At least some of the potential problems
identified for the South Carolina Charter Logbook Survey could be
addressed through a logbooklicense linkage, as described above.
Although RTC was concerned that there could be implementation
issues for logbook programs, this will be true with any fundamental
change in sampling protocol. Given the magnitude of the for-hire sector
in some regions and the potential scale of fishery removals for this
sector, the committee finds compelling arguments for the use of
mandatory logbooks as the source of catch and effort data for the for-hire
sector. Furthermore, ACCSP found that recreational and charter fishing
constituents along the Atlantic coast have a strong desire to participate
more actively in data collection (Loftus et al., 1999), and the committee
heard similar comments during public testimony.3 Not only can
mandatory reporting from the for-hire sector increase the public's
acceptance of the credibility of recreational catch statistics, it may help to
facilitate "ownership" of these data by the for-hire sector. If the data they
are supplying are a component of the final estimation, there may be
fewer criticisms of these final estimates.
The use of logbook data is particularly important for fisheries in
which fishery-independent surveys are conducted infrequently or not at
all because these data will be an essential component of stock assessment
calculations. The committee recognizes that logbooks should not be re-
3The testimony from a small number of individuals on this topic may not repre-
sent the whole fishing community; however, this testimony originated from the
largest national organization of charter boat operators.
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REMOVAL ESTIMATION 75
quired by more than one level of government (state, regional, federal,
and international), and agencies must be coordinated to avoid the burden
of duplicate reporting. The committee sees the state as the appropriate
level of implementation for this requirement, with adherence to national
reporting standards and program coordination at the national level.
Validation of data acquired through any source is an issue of
concern, and it would be no less so for a mandatory logbook program.
The data collected through logbook programs will be reliable only if
there are strict verification and enforcement components of the program.
Since the information obtained from the logbooks is owner supplied,
there is the need for verification for both CPUE and effort. Effort and
kept catch could be checked by dockside inspection of angler parties and
their catch. However, accurate and timely logbook submission as a
condition of license is important. While the normal process of validation
through creel surveys and random sampling of individual clients on the
vessels could still be used, there would be direct and effective
accountability because of the legal requirement for the logbooks, as well
as the economic incentive associated with continued licensing of the
charter operation. Also, the logbook program will serve as a participation
record for any more detailed allocation discussions (e.g., the use of
individual quotas for charter vessels, which is being contemplated in
some jurisdictions). Finally, a mandatory logbook program provides a
comparison vehicle for data acquired independently via offsite, random,
individual angler-based or panel-based surveys.
A for-hire logbook program represents a significant step in mon-
itoring of this sector, but it will not solve all problems of monitoring. For
example, accurate accounting and verification of catch-and-release
activity will be addressed only partially through such a program.
Alternative verification of catch and release via observers or electronic
monitoring may be required. However, the committee views the for-hire
sector as a business enterprise--the business being the connection of
people and fishing opportunity. Therefore, this sector should be subject
to a greater level of reporting than independent anglers, as a corollary of
conducting business based on a public resource.
Such a program will require additional resources to maintain a
logbook-based data infrastructure. However, the substantial benefits of
the program, as recognized in previous reviews and some existing
programs, argue for its adoption and the commitment of resources to its
implementation. Also, there are significant design issues associated with
stratification by size of charter operation and geographic locality. These
design issues are further addressed in Chapter 6.
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76 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
ANALYSIS AND ESTIMATION TECHNIQUES
Below is a detailed overview of analysis and estimation issues re-
lated to the MRFSS that could revolutionize the way the survey is
analyzed, especially at smaller spatial scales. It is deliberately presented
at a higher technical level than some of the other sections because of the
complexities involved. Generally, the analysis issues are focused on the
use of auxiliary information to increase precision and the special prob-
lems with estimation of subpopulations. In virtually all surveys, esti-
mates are required not only for the population as a whole but for various
subpopulations, called domains. For human populations, domains may be
demographic groups (e.g., age, race, sex), occupational groups, or geo-
graphic groups. For natural resource inventories, domains are typically
geographic (e.g., county, state, state waters, federal waters) or ecological
subdivisions (e.g., ecoregion, watershed). Geographic subpopulations are
called areas. In fisheries, domains could be geographic areas or temporal
periods.
Often domains are not sampling strata so the sample size within
domains is not pre-allocated but is determined randomly from the
sampling. Three useful classes of domains are large domains, medium
domains, and small domains, based on the sample sizes attained in those
domains.
Large Domains and Direct Estimation
Large domains are likely to be sampling strata (i.e., predefined
subpopulations that are sampled independently using predetermined
sample allocations), but even if they are not, they are large enough to
have a high probability of a large sample size. This large sample size
ensures that standard design-based survey estimation procedures yield
estimators of adequate precision. These standard estimators are called
direct estimators because they use data only from the study units in the
domain and time period of interest. These estimators have good design
properties, and they are typically unbiased (or asymptotically unbiased),
asymptotically normal, and allow for statistically consistent variance
estimation and valid confidence intervals. All of these good statistical
properties are justified by the randomization used in the probability
sampling design and do not depend on the validity of any statistical
model. This is the approach usually used in the current MRFSS analyses.
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REMOVAL ESTIMATION 77
Medium Domains and Survey Regression Estimation
Direct estimation is not reliable if the sample size is too small. In
medium domains, the sample size is moderate but not extremely small.
For such domains, if auxiliary information is available at both the
population level and the sample level, it is often possible to construct a
survey regression estimator (e.g., Cochran, 1977) with greater precision
than that of the simple direct estimator. Such an estimator fits a global
regression model to all of the survey data and predicts the responses for
unsampled population elements using the fitted model. Survey regression
estimators may be either model-based or model-assisted. Model-based
survey regression estimators estimate the total for a domain by adding
the responses for the sampled elements to the predicted responses for the
unsampled elements. Such estimators are highly efficient if the model is
right but can be biased and even inconsistent if the model is wrong. On
the other hand, a model-assisted survey regression estimator predicts all
elements using the fitted model and adds them up over the domain of
interest. Since this prediction may be biased if the model is not specified
correctly, the model-assisted estimator adds on a design-bias adjustment
computed as the weighted difference between the observed and predicted
responses over the domain. If the model is right, the estimator is highly
efficient. The key result is that whether or not the model is right, the
model-assisted estimator retains the good design properties of a direct
estimator (i.e., it is asymptotically unbiased, asymptotically normal, and
allows for consistent variance estimation and valid confidence intervals)
(Särndal et al., 1992).
The type of survey regression estimator depends on the types of
available auxiliary information. With categorical covariates only, the
survey regression estimator is a post-stratified estimator. With a single
continuous covariate, the survey regression estimator could be a ratio
estimator, classical regression estimator, or even a kernel or spline-
based nonparametric survey regression estimator (e.g., Breidt and
Opsomer, 2000). Generalizations to multiple covariates are also possible.
To ensure the quality and timeliness of any of these survey regres-
sion estimators, all covariates that enter the regression must be of high
quality and must be readily available in a timely manner. Definitions of
the covariates and protocols for their measurement should change as little
as possible over time. Missing covariate information should be minimal.
Indeed, all of the quality standards applicable to responses in the original
survey are applicable to the covariates as well.
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78 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
In the context of fisheries surveys, possible covariates for effort
could include business-related covariates (e.g., bait sales, boat rentals)
and weather-related covariates (e.g., precipitation, temperature, wave
height). The business-related covariates could be difficult to obtain and
use in an ongoing survey. Establishments vary in size and in the
resources they devote to maintaining accounting records. Quality can
vary considerably from establishment to establishment and from year to
year. Definitions would need to be standardized, and cycles of data
compilations would need to be synchronized. Thus, tracking down and
compiling sales or rental data could be as difficult as conducting the
original survey. The weather-related covariates, on the other hand, are
readily available in a timely and consistent manner from a centralized
source--the National Oceanic and Atmospheric Administration itself.
Use of these weather data should involve minimal additional cost.
Small Domains and Small Area Estimation
The final domain classification is the small domain, called a small
area in a geographic context (Ghosh and Rao, 1994; Rao, 2003). Here,
direct estimators or model-assisted survey regression estimators are not
sufficiently precise for the inferential problems of interest. Typically, the
random sample size in a small domain or area is small and may be zero
in some cases. There is no hope for direct estimation with such small
sample sizes so small domain estimation problems lead to indirect
estimators. Unlike direct estimators, indirect estimators use data from
outside the domain or time period of interest to "borrow strength" across
time or space, and the validity of these indirect methods depends on the
correctness of the model specification.
Perhaps the simplest small area estimator is the synthetic estimator in
which all elements in a domain are predicted from a fitted global model
relating the response variable to the covariates. The model borrows
strength from the entire sample in the fitting of the regression model,
which typically has common coefficients for all domains in the pop-
ulation. The synthetic estimator can be computed for a given small do-
main even if there are no samples in that domain and usually has very
low variance since it is fitted on the basis of the entire sample, but it may
have large bias if the model is incorrectly specified.
A composite estimator attempts to trade off the low bias but high
variability of a direct estimator with the high bias but low variability of a
synthetic estimator by computing a combination of the two estimators.
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REMOVAL ESTIMATION 79
The weights in this composite estimator can be chosen in an ad hoc
way, such as by making the weight on the direct estimator larger if the
sample size in that domain gets larger. The weights also can be chosen
on the basis of a formal statistical model. The standard approach to
formal composite estimation is to choose the composite weights as
functions of the parameters from a fitted model. Two classes of models
appear in the literature, depending on the type of available auxiliary
information. Element-level models require auxiliary information for
every sampled element (e.g., Battese et al., 1988), while area-level
models require auxiliary information only for each small area. In either
case, the small area model is hierarchical. In area-level models, much of
the complexity of the survey design is averaged out, and nonnormality in
responses tends to average out as well.
Here, the focus is on the area-level model. Assuming that auxiliary
information is available for each small area, the model describes the
distribution of the direct estimates given the true domain parameters, and
the distribution of the true domain parameters given the covariates.
Usually, the direct estimate is modeled as truth + sampling error where
the sampling error has a mean of zero and known variance. The true
domain parameters are modeled with a global regression function of the
covariates, plus domain-specific deviations from the global model. The
domain-specific deviations are random effects that may have some
correlation structure, such as temporal correlation structure in a time-
indirect context or spatial correlation structure in a domain-indirect
geographic context.
The small domain model has two ways to borrow strength: globally
through the regression fitted to all the data and locally through the
temporally or spatially correlated random effects. Temporal correlation
structure can be described with a state space model, special cases of
which can include autoregressive moving average models (e.g.,
Brockwell and Davis, 1991). State-level unemployment estimates from
the Current Population Survey, for example, combine a regression mod-
el, a basic structural model for stochastic trend and seasonality, and an
autoregressive moving average model for the correlated sampling errors
(Tiller, 1992). Spatial correlation structure in an area-level model can be
described with a lattice model, such as a conditional autoregression
model (Cressie, 1993).
Small area estimation models are fitted using standard statistical
procedures, such as through estimation of variancecovariance
parameters by restricted maximum likelihood or other methods followed
by joint estimation and prediction of the fixed and random effects in the
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80 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
model. This approach is known as empirical best linear unbiased
prediction and has relatively straightforward computation that may be
implemented using standard statistical software (e.g., the PROC MIXED
function in SAS software, the lme function in S-Plus software), but these
methods do not account fully for uncertainty since they treat the
estimated variancecovariance parameters as known. Hierarchical
Bayesian analysis is also possible. Prior distributions for all unknown
parameters (including variancecovariance parameters) are assigned, and
then numerical techniques, such as Markov Chain Monte Carlo, are used
to compute posterior distributions of the unknown parameters given the
direct estimates. Computation is more complex, but now these methods
are routinely taught to statisticians in graduate school and routinely
implemented in many government agencies that employ statisticians.
Use of These Techniques in Angler Surveys
In the context of angler surveys, use of auxiliary variables and small
area estimation techniques might be applied to the effort estimates, the
CPUE estimates, or the final catch estimates, perhaps after some
transformation. Suitable auxiliary information for effort modeling may
include weather-related covariates; suitable auxiliary information for
CPUE may or may not be available. Identification of suitable covariates
and specification of an appropriate regression model or models would be
a critical part of a small area analysis.
Even without suitable covariates, estimation of both effort and CPUE
might be assisted by temporal, spatial, and multivariate correlation. The
data are collected in temporal waves, and wave-to-wave or year-to-year
correlation might be helpful in predicting current wave values. Also, the
data are spatially explicit, so borrowing information from similar, nearby
areas might help to improve predictions. Finally, the data are multivariate
(catch by species), and the correlation structure among the different
species might help in predicting individual species components.
To conclude, the current estimation methodology used in the MRFSS
is primarily direct estimation for large domains. Auxiliary information
and survey regression estimation methods enter in minor ways, such as in
some simple ratio adjustments and temporal pooling of estimators. It
appears that with relatively modest additional resources, the MRFSS
could add more formal survey regression methods, extending the
inferential scale to medium-sized domains. Small area estimation would
require a much greater investment of resources. This estimation method-
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REMOVAL ESTIMATION 81
ology would require stronger assumptions, more sophisticated model
specification (both in the regression model and in the covariance struc-
ture), more detailed diagnostics, and heavier computations. However, the
potential pay-off is enormous in that it extends the inferential scale to
finer spatial resolutions, which seems to be what managers currently
require. These recommendations will require a rethinking of the program
management of angler surveys (see Chapter 6 on program management
and support).
CONCLUSIONS AND RECOMMENDATIONS
The committee concludes that the current methods used in the
MRFSS for sampling the universe of anglers and for determining
their catch and effort are inadequate. Sampling of each group of
anglers (i.e., private, guided, head boat, and charter boat) presents chal-
lenges that can differ across the groups. Two complementary methods of
sampling angler catch and effort are used in the MRFSS. One is onsite
(i.e., intercepting anglers while they are fishing or at their access
[landing] points). The other is offsite, which includes a variety of sampl-
ing techniques for contacting anglers after they have completed their
trips. Both onsite and offsite methods suffer from weaknesses that may
lead to biases in catch and effort estimation. This necessitates major
changes in both the design and analysis procedures.
A comprehensive, universal sampling frame with national
coverage should be established. The most effective ways to achieve this
are through a national registry of all saltwater anglers or through new or
existing state saltwater license programs that would allow no exemptions
and that would provide appropriate contact and information from anglers
fishing in all marine waters, both state and federal. Any gaps in such a
program (e.g., a lack of registration in a particular region or mode, ex-
emptions of various classes of anglers) would compromise the use of the
sampling frame and, hence, the quality of the survey program. Future
telephone surveys should be based on the above universal sampling
frame.
Dual-frame procedures should be used wherever possible to
reduce sample bias. For example, if a state has an incomplete list frame
based on licenses, the use of an additional sampling frame of the state's
residents (e.g., RDD) would reduce the bias. The existence of a universal
frame described above would make this approach unnecessary for offsite
sampling, provided there are no exemptions. Complemented surveys
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82 REVIEW OF RECREATIONAL FISHERIES SURVEY METHODS
should be used more widely in regional surveys where reliable esti-
mates are required for management of a small suite of very im-
portant species at small regional scales.
Panel surveys, which contact individual anglers repeatedly over
time, should be considered in recreational fishing surveys to gather
angler trend data and to improve the efficiency of data collection.
This is especially true for the telephone portion of the MRFSS.
Internet surveys should be considered for their potential use in
recreational fishing surveys, especially in panel surveys, as a way for
anglers to submit information. They could be used in the for-hire
surveys, in private angler surveys like the MRFSS, or in social and eco-
nomic surveys.
In most cases, charter boat, head boat, and other for-hire
recreational fishing operations should be required to maintain log-
books of fish landed and kept, as well as fish caught and released.
Providing the information should be mandatory for continued operation
in this sector, and all the information should be verifiable and made
available to the survey program in a timely manner. Onboard observers
could be used on a sample of vessels to verify logbook information. A
sample survey may be more appropriate in fisheries where the for-hire
sector is a small component of the catch or where verification and
enforcement are particularly problematic.
The reported release alive of captured fish (catch and release) is
increasingly common in many marine recreational fisheries. Although
released fish suffer lower mortality than retained fish (the mortality of
retained fish is, of course, 100 percent), there still is some mortality, and
in some cases, it can exceed 50 percent. The survey fails to provide a
valid and reliable method of adequately accounting for fish caught
and not brought to the dock (including fish released alive or dead, as
well as fish caught for bait or given away before reaching the dock).
This shortcoming affects estimates of catch and total removals.
Current analysis procedures used in estimation for the MRFSS
do not exploit the current knowledge of finite population sampling
theory. The current estimates are particularly deficient when applied to
small areas because they do not use information in adjoining areas or
time periods, nor do they consider relationships between species that
occur together. Therefore, they are of lower precision than would be
possible if this information were used. Improvements in these estimates
would be of great use to managers who need to make quick decisions
concerning spatial areas that are smaller than typical in the early years of
the MRFSS.
Representative terms from entire chapter:
marine recreational
