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NOAA Technical Memorandum NMFS-AFSC-213

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Bycatch characterization in the Pacific halibut fishery: A field test of electronic monitoring technology


The increasing focus on the ecosystem approach to fisheries management and the requirement to include all sources of fishing mortality in single species stock assessments heightens the need for accurate and comprehensive catch data from all fisheries.  In the waters off Alaska, Pacific halibut (Hippoglossus stenolepis) is harvested by longline in an individual fishing quota (IFQ) fishery.  In general, the species composition of at-sea discards in this fishery is poorly characterized because the majority of vessels operating in this fishery are not required to have at-sea observer monitoring; hence, estimates of bycatch are not based on direct observation of the fishery.  Current information on bycatch in the halibut fishery off Alaska is neither comprehensive nor representative and is derived primarily from unverified logbook reports, survey catches, or other indirect sources.

In this study, we compared estimates of bycatch (numbers of fish) based on dedicated fishery observer (hook-status) documentation of numbers of species hooked with estimates of bycatch based on review of electronic monitoring (EM) video recordings, and where possible, with estimates based on standard Alaska Fisheries Science Center (AFSC) Observer monitoring. 

Participation from the halibut industry was lower than expected.  Although many vessel owners expressed support for the project, we encountered reluctance by some vessel owners to bring either EM or observers aboard their vessels.  We did successfully recruit four vessels to the study, one of which had not previously been subject to observer coverage requirements.  We installed EM systems on these vessels and collected EM and observer data during fishing activities in the Bering Sea and the Gulf of Alaska. 

During the study, we experienced unanticipated technical problems that resulted in data capture rates that were lower than expected.  These issues were rapidly resolved in all cases.  Lapses in EM data capture tended to encompass large portions of, or entire, fishing trips while lapses in observer data capture tended to be interspersed within individual trips.

Comparison of species identification of catch between standard observer estimation, complete hook-status observer coverage, and EM coverage showed statistically unbiased and acceptable comparability for almost all species except for some that could not be identified beyond the species grouping levels used in management.  Similarly, comparisons of total species-specific numbers of fish estimated using EM-collected and hook-status observer-collected data showed few statistically significant differences.

Based on this study, although limited in scope, EM can provide an additional tool for catch monitoring in the commercial halibut fishery.  However, the potential uses of EM need to be determined by the specific monitoring requirements of each management application.  EM is not an alternative to observers for the collection of certain biological specimens (e.g., otoliths, scales, etc.) from the catch.  With the further development of EM systems and procedures, estimation of bycatch species composition in numbers of fish in the Pacific halibut fishery could be achieved with a high degree of accuracy.

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