Evaluation of Electronic Monitoring Pre-implementation in the Hawaiʻi-based Longline Fisheries

November 04, 2019

The Pacific Islands Fisheries Science Center (PIFSC) is currently evaluating how to effectively use electronic monitoring (EM) systems in Hawaiʻi-based pelagic longline fisheries as a data collection tool.

The Pacific Islands Fisheries Science Center (PIFSC) is currently evaluating how to effectively use electronic monitoring (EM) systems in Hawaiʻi-based pelagic longline fisheries as a data collection tool. These fisheries are comprised of two sectors, a deep-set fishery targeting bigeye tuna (Thunnus obesus) and a shallow-set fishery targeting swordfish (Xiphias gladius), with fisheries-dependent data collected from three sources: captain logbooks, dealer reports, and at-sea observers. Each data set has limitations. Logbook data consist of industry reported data, which historically underreport bycatch1 that are discarded, such as sharks (Camhi et al. 2009). Dealers report weights for marketable fish; consequently, average weights calculated from these data do not represent discards. At-sea observer data provide information on both discarded and retained catch, including subsamples of lengths which are limited to estimates for animals not brought aboard. At sea observer data are collected on about 25% of fishing trips (100% of shallow-set trips and 20% of deep-set trips); whereas logbook and dealer data sets provide data from all fishing trips. EM provides a method to supplement these data streams to reduce potential sources of bias and inform management of the Hawaiʻi longline fisheries.

To evaluate the efficacy of EM as a monitoring tool, 18 systems were installed on Hawaiʻi longline vessels for this pre-implementation study. These EM systems included video cameras to capture footage for fish and protected species (sea turtles, seabirds, and marine mammals) identification, global positioning systems (GPS) for fishing location, and fishing gear sensors that help detect catch events (i.e., reel rotation, hydraulic pressure, and vessel speed generally decline when large fish are brought aboard) and trigger video cameras to record during gear retrieval.  

Comparison of data collected by at-sea observers with post-cruise review of EM data indicate EM systems provide an additional means to accurately enumerate fish. A total of 89% of all catch enumerated by at-sea observers (retained and bycatch) were detected in EM data during video review. For retained fish only, EM reviewers located 98% of the fish enumerated by at-sea observers in the shallow-set fishery and 100% in the deep-set fishery. EM data also provided accurate enumeration over broad taxonomic groupings (e.g., tunas, billfishes, sea turtles) and for many economically valuable fish species. However, compared to at-sea observers, EM reviewers were not able to provide identifications to the species level for some species, including those subject to management implications, such as bigeye tuna and hardshell sea turtles. For bigeye tuna, there were significant differences (p < 0.001) between EM and at-sea observer enumerations. Sea turtle identifications were limited to the broader categories of hardshell or softshell sea turtle. Specific modifications to the current EM systems and catch handling are recommended in this technical memorandum to improve enumeration and identification to species that can be used for monitoring in the Hawaiʻi longline fisheries (e.g., identification of tunas, sharks, and sea turtles to species). 

Finally, this PIFSC pre-implementation project demonstrated that EM could be a cost-effective method to augment fisheries-dependent data collection. EM data review may be completed with a 76% reduction in the time needed to collect similar data by at-sea observers.


Carnes MJ, Stahl JP, Bigelow KA. 2019. Evaluation of electronic monitoring pre-implementation in the Hawaiʻi-based longline fisheries. NOAA Tech Memo. NMFS-PIFSC-90.

Last updated by Pacific Islands Fisheries Science Center on 11/04/2019