An assessment of electronic monitoring in Australian tuna longline fisheries

Electronic monitoring (EM) has the capacity to collect fisheries-dependent data to support fisheries management decision-making. In Australia, an integrated EM system was implemented as a replacement for at-sea observers in several managed fisheries, including the tuna longline fisheries from 1 July 2015. In these fisheries, EM is used as an audit tool to independently validate fisheries logbook information. To assess whether the Australian EM system was meeting key objectives we: (i) compared EM analyst and fisher-reported logbook data to examine the level of congruence in reporting of both retained and discarded catch and protected species interactions and; (ii) analysed changes in logbook reported nominal catch and discard per unit effort (CPUE and DPUE) and interactions with protected species per-unit-effort (IPUE) post EM implementation. In general, congruence between fisher-reported logbook and EM analyst data for the tuna longline fishery was higher for retained than discarded catch. However, there was variability among individual species and species groups. Data reported for some species were highly congruent (e.g. tuna, swordfish) but for others there were taxonomic (e.g. escolar and rudderfish), identification (e.g. sharks, marlins) and reporting (e.g. marine turtles, sharks and marlins) issues, which reduced overall congruence. For many species that were discarded, the number reported in the logbook was higher than that reported by the EM analyst due either to species being grouped into a mixed category or individuals not being observed. Our analysis of logbook changes in the tuna longline fishery identified significant increases in fisher-reported logbook DPUE for target, byproduct and bycatch species and IPUE for marine seabirds, mammals and turtles in the two years following the implementation of EM relative to the previous six years. Not discounting possible environmentally-driven shifts in availability and abundance, as well as individual vessel effects, weight of evidence suggests the use of EM as an audit tool has led to significant changes in logbook reporting. We contend that both analyses provide an important insight into the ability of the EM, when used as an audit tool, to lead to improvements in logbook reporting behaviour and to record and report the capture of all species in tuna longline fisheries.