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California

California. For-Hire Review December 2008. Logbooks. Potential to provide an effort census, but not currently used for effort estimation. Logbook response is unreliable. Validation does not appear to be done in an organized manner.

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California

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  1. California For-Hire Review December 2008

  2. Logbooks • Potential to provide an effort census, but not currently used for effort estimation. • Logbook response is unreliable. • Validation does not appear to be done in an organized manner. • Consistent data quality over time must be ensured for logbook data to be useful at monitoring trends.

  3. Logbooks • Verification of logbooks should be based on probability sampling at dockside. • Logbook and dockside sampling can be coordinated using double sampling techniques to adjust logbook estimates.

  4. CRFS: PCPS • Sample allocation is based on percentage of vessels basis. • Allocation should be based on controlling sampling error for key domains of interest. • Optimal allocation to control variance will likely lead to sampling in proportion to expected number of angler trips.

  5. CRFS: PCPS • A serious effort must be made to improve response rates: • Only 50% of vessels respond, including a large number of refusals. • Non-response adjustment must be applied to reduce non-response bias. • Estimation procedures do not appear to account for stratification of sampling frame.

  6. CRFS: CA-PC • Selection of CPFV trips described as a three step process: • Selection of landing sites. • Selection of day type, CPFV type and areas fished. • Selection of CPFV at the landing. • Difficult to evaluate without frame construction and probabilities of selection at each stage. • Trip selection at landing site: • Described as systematic and proportional to past effort for day type. • Unclear how this can be implemented as vessels are returning to the landing site.

  7. CRFS: CA-PC • There is a need to formalized the sampling process: • There appears to be some probability proportional to size sampling built in, but this should implemented in a formal selection algorithm. • On large vessels, a sample of anglers may need to be taken, but there is no formal process for doing this. • Similarly, the method for sampling from an angler’s catch should be formalized.

  8. CRFS: CA-OSP • General approach is to increase sample size and reduce sampling error. • Too little attention given to controlling coverage and measurement biases. • Procedures for estimating effort and CPUE for missed boats not based on probability sampling. • Too much discretion is left to data collectors. • Documentation of landing port-day sample required.

  9. CRFS: AT-SEA • Limited to larger vessels. • No rigorous use of probability sampling. • There is a need to document procedures for combining at sea sampling with other intercept data.

  10. CRFS: General comments • Population definitions must be clearly stated: • Must clarify whether area fished or area landed is basis for reporting. • Frame undercoverage needs to be documented and examined: • Is it negligible or should coverage be extended?

  11. CRFS • The telephone survey response rate is poor but it is the major source of effort data. • Validity checks are made, but in unspecified ways. • No effort is made to systematically combine data from different sources. • A long term effort is required to: • Eliminate duplication • Get log-type data on time (perhaps on sample basis) • Increase response rates

  12. CRFS • Respondent sample is treated as the selected sample in estimation: • Selection of CPUE sample by site introduces extra stage into sampling process. • Large cluster sizes lead to higher variance. • Sampling for CPUE: • Appears based on site and time assignments with quotas for numbers of vessels and fish. • Data collectors have too much discretion in selecting the sample.

  13. CRFS • Probability proportional to size sampling could be used to control workload and improve precision. • Make greater use of optimal allocation • Probability sampling should be used at all stages of sample collection. • Estimation should be based on the probability sampling design, with correct weighting and adjustments for non-response bias and undercoverage.

  14. CRFS • Similar data are obtained from multiple sources. • It should be possible to provide timely preliminary estimates, and revise these using more reliable data or multiple-frame estimation.

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