Pilot study of an electronic monitoring system on a tropical tuna purse seine vessel in the Atlantic Ocean

Abstract

One challenge of the implementation of observer programs is the difficulty of ensuring an adequate statistical coverage of whole fleets, and this may hamper the usefulness of the data for management purposes. These constraints make it necessary to find alternative cost-effective methods. Electronic monitoring (EM) systems are being used in some fisheries as an alternative, or a complement to human observers. The overall objective of this study was to test the use and reliability of EM on a tropical tuna purse seiner in the Atlantic Ocean. To achieve this objective 61 free and FAD sets of a tuna purse seiner were closely monitored to compare information provided by EM and onboard observers to determine if EM can reliably document fishing effort, set-type, tuna catch, and bycatch. Set-type was correctly identified using EM for 60 of the 61 sets. Total tuna catch per set was not significantly different between EM and observer data sets; however, species composition did not match for all the species between EM and observers. Overall, bycatch species were underestimated by EM, but large bodied species such as billfishes were well documented. The analyses in this study showed that EM can be used to determine the fishing effort (number of sets), set-type, and total tuna catch as reliably as observers can. In order to be fully comparable with observer data, improvements for accurately estimating the bycatch will need to be developed in the EM system. Operational aspects that need to be improved for an EM program to be implemented include standardising installation and onboard catch handling methodology, as well as improvements in video technology deployment.