Quantification of “observer effect” in the United States Atlantic pelagic longline fishery

Fishers in the United States pelagic longline fishery are required to self-report all fishing interactions (captures) on a per-set basis to the National Oceanic and Atmospheric Administration (NOAA) to quantify catch, increase conservation efforts, and allow for an accounting of international quota-managed species. Additionally, trained fisheries observers are deployed on commercial vessels to produce a statistical subset of pelagic longline fisheries data. Generalized additive mixed models were used to compare vessel captain-reported versus observer-collected datasets for fishing occurring in the western North Atlantic Ocean. Results showed a general consistency in logbook reporting for most target species, but potential under-reporting from 1.4× to 5.4× for lesser-valued and bycatch species. These discrepancies among catch rates of targeted species, species of bycatch concern, and species of minimum economic value showed an under-reporting in the logbook versus observer data, indicating the level of accuracy for self-reported data is lower than data collected by pelagic fisheries observers for a number of species. Additional analyses are needed to examine how varying management measures through time may influence reporting accuracy at the species level.