the Exploration of the Sea Do not cite without permission of author Visualizing Alaska Pollock (Theragra chalcogramma) Aggregation Dynamics

• Main Authors: Steven J. Barbeaux, Martin Dorn, James Ianelli, John Horne
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Bering Sea; alaska pollock; Theragra chalcogramma; Alaska
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.183.5169; http://www.fakr.noaa.gov/sustainablefisheries/sslmc/may-06/fit/Barbeauxetal2005.pdf

Commercial echosounders are used to collect acoustic data from fishing vessels during normal fishing operations. In the winter of 2003 we collected approximately 32,000 km of backscatter data from three commercial fishing vessels participating in the southeastern Bering Sea Alaska pollock fishery. Although these data were not collected on a systematic grid, their broad temporal extent combined with a high spatial resolution facilitates investigations on the distribution and behavior of fished aggregations. Threedimensional Kriging was used to produce snapshots of Alaska pollock (Theragra chalcogramma) distributions over the fishing season. Fleet movement and effort was tracked using vessel monitoring system data and on-board observer catch data. Integration of these data allows an unprecedented look at four-dimensional distributional changes in Alaska pollock aggregations and how aggregation behavior is reflected in the dynamics of the fishing fleet. Our snapshots reveal that Alaska pollock have a highly dynamic small-scale spatial structure, diurnally congregating to patchy, dense aggregations and nocturnally dispersing to a few uniform low-density aggregations. Changes in trawl tow duration and search patterns coincide with diel and successive changes in Alaska pollock distributions. Qualitative results suggest that rapid changes in distributions and local densities of Alaska pollock aggregations occur in areas of high fishing pressure.