Review of the Marine Recreational Information Program (2017) / Chapter Skim
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2 Study Design and Estimation Considerations for the MRIP
2 Study Design and Estimation Considerations for the MRIP
Pages 31-42
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From page 31... ...
The purpose of this chapter is to provide perspective on data collection, sample design, and estimation relevant to the MRIP to help the reader who is not familiar with statistical methods for survey sampling of recreational fisheries. CONTACT METHODS Surveys of recreational fishing to obtain metrics of catch and effort rely on seven possible methods of contacting anglers (Pollock et al., 1994; Jones and Pollock, 2013; see Box 2.1 for discussion of the distinctions between censuses and sample surveys)
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From page 32... ...
The complexity of the sample design depends on the type of survey and the information available prior to sampling. Complex sampling designs usually involve stratification and clustering.
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From page 33... ...
CHALLENGES WITH DATA COLLECTION The choice of survey method is dependent on the time frame in which data are needed and the funds available to conduct the survey; both timeliness and funding issues were raised as concerns by state agencies during the committee's current review of the MRIP. Offsite methods using telephone and mail surveys are generally less expensive than onsite methods because the latter require trained personnel in the field (Groves, 1989; Jones and Pollock, 2013)
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From page 34... ...
and lack coverage of anglers using private access when interviews are generally conducted at public-access sites. The lack of intercept information from most private access means that the use of CPUE requires the strong assumption that catch and effort are equal between anglers using public and private access (Ashford et al., 2010, 2011, 2013)
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From page 35... ...
SAMPLING FRAMES Recreational angler surveys use sampling frames to randomly select, with known probabilities of selection, households or fishing sites and times to contact. To contact households with anglers offsite to determine effort, two approaches have been commonly used in marine fisheries (Jones, 2001)
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From page 36... ...
This complemented approach is based on the assumption that anglers missed by the intercept survey (e.g., fishing on private piers) have the same average CPUE as those included on the intercept survey, which can be an incorrect assumption depending on the target species.
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From page 37... ...
For stock assessment, an additional fraction of the catch released alive that subsequently dies is estimated by multiplying the fish discarded by a separately determined discard mortality rate to obtain component (3) -- fish discarded alive that subsequently die from capture effects.
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From page 38... ...
k = boat/angler and, if applicable, angler group within boat (see Chapter 4) Estimated effort obtained from the FES, the Coastal Household Telephone Survey, and the like ˆ Estimated effort = E, defined as the estimated total number of single-day angler trips spent saltwater fishing E = ∑ ∑ w hi ehi , ˆ (2)
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From page 39... ...
for species f per SSU hjk (f δ hjk = zero-one variable indicating membership in domain d wk|hj = SU-level final analysis weight conditional on selection of S site hj whj = final analysis weight for PSU hj (b) Estimated total discard per unit effort for species f for domain d = !
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From page 40... ...
The resulting weights are often referred to as final weights and the corresponding weighting system as the final weighting system. In some cases, the weighting process involves an additional stage during which the final weights undergo further modification.
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From page 41... ...
standard error also uses the final weights but with a more complex formula than is appropriate for this report -- see, for example, Wolter (2007) for additional material on variance calculations.
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