Shore-Based and Boat-Based Fishing Surveys in Guam, the CNMI, and American Samoa: Survey Design, Expansion Algorithm, and a Case Study

The annual catch is estimated as the product of catch-per-unit-effort (CPUE, from the catch rate survey) and annual fishing effort (from the fishing effort survey). The shore-based effort and catch rate surveys each utilize a “roving survey” design. During the roving catch rate survey, encountered fishers are interviewed to gather data on fishing methods, hours fished, and fish caught. In the roving fishing effort survey, accessible shorelines are visited to record active fishing events, characterizing fishing methods and gear counts. The shore-based survey is stratified by day type (weekday vs. weekend) and shift (different periods in a day) in all three territories. The shore-based CPUE and effort estimates, and thus catch estimates, are made separately for each fishing method.

The boat-based survey is mainly an access point survey by design. Catch rate and effort surveys are conducted at major ports, and the surveys are stratified by day type (in all three territories) and port (except for American Samoa). The catch rate and effort estimates are made separately for different fishing methods and charter statuses (charter fishing vs. non-charter fishing). As for the shore-based survey, total catch is then estimated as the product of CPUE and fishing effort. We use the boat-based survey in Guam as a case study to describe how effort and catch rate estimates for different fishing methods at different ports are combined to estimate total catch. Trolling and bottomfishing are the most common fishing methods on Guam, and trolling accounts for 80% of the boat-based catch. Non-charter fishing dominates the catch, contributing approximately 90% and 95% of the total catch for trolling and bottomfishing, respectively. The three sampled ports on Guam account for 90% of the total catch. Interview pooling is used when insufficient interviews are available for an estimation domain; however, it was needed for no more than approximately 10% of the non-charter trolling and bottomfishing domains at the three sampled ports. The non-charter bottomfishing method was used to detail the expansion steps for producing the total catch for a highly targeted deep bottomfish species.

The catch and effort estimates in these three United States Pacific island territories were historically produced with a series of expansion scripts written in Visual FoxPro (VFP). Recently, scripts in the programming language R were developed to replace and improve upon the VFP scripts. This report describes the current survey design and expansion methods, including some recent modifications incorporated in the R scripts.

The Pacific Islands Fisheries Science Center of NOAA’s National Marine Fisheries Service uses the NOAA Technical Memorandum NMFS-PIFSC series to disseminate scientific and technical information that has been scientifically reviewed and edited. Documents within this series reflect sound professional work and may be referenced in the formal scientific and technical literature.