A preliminary spatial comparison of fisheries data from several sources in a Gulf of Alaska trawl fishery.

David Ackley
Alaska Region, NMFS

A pilot project was undertaken this summer which tested the feasibility of an alternate method of deploying observers in a small Gulf of Alaska fishery. Normally vessels are allowed to choose when they carry an observer during each quarter of the year, however, this can result in areas or periods for which little or no observer data is available. In this project, a simple model deployed observers to ensure that there was coverage of all areas at all times.

Data from several sources has allowed cross-validation of fisheries information received from this project. All vessels in the project were required to carry VMS (Vessel Monitoring System) units which broadcasted the vessel location at 30 minute intervals. Observers recorded the location and species catch information from each observed haul, with approximately 60% - 70% of all hauls on a trip actually sampled by the observer. Processing plants reported delivered catch and the statistical area from which the catch was taken, information comparable to that recorded in State of Alaska fish tickets. In addition, several vessels submitted records from an electronic vessel logbook system detailing information from each haul.

Preliminary analysis of the data from this project has offered insight into the accuracies of self-reported data, both in catch composition and in reported catch location. The actual vessel location as provided by VMS has allowed comparison and verification of reported locations. The combination of VMS with observer data has also allowed the exploration of patterns in species catch which could then be compared to reported catch. In addition, data from previous years has revealed some interesting differences in fleet behaviour prior to and during the project.