9781888569605-ch38

Benthic Habitats and the Effects of Fishing

Discovery of 100-160-Year-Old Iceberg Gouges and Their Relation to Halibut Habitat in Glacier Bay, Alaska

Paul R. Carlson, Philip N. Hooge, and Guy R. Cochrane

doi: https://doi.org/10.47886/9781888569605.ch38

Abstract.—Side-scan sonar and multibeam imagery of Glacier Bay, Alaska, revealed complex iceberg gouge patterns at water depths to 135 m on the floor of Whidbey Passage and south to the bay entrance. These previously undiscovered gouges likely formed more than 100 years ago as the glacier retreated rapidly up Glacier Bay. Gouged areas free of fine sediment supported greater biodiversity of Pacific halibut Hippoglossus stenolepis than nearby sediment-filled gouges, probably due to increased habitat complexity. Small Pacific halibut were found more frequently in sedimentfree gouged areas, presumably due to higher prey abundance. In contrast, large Pacific halibut were found more frequently on soft substrates such as sediment-filled gouges, where they could bury themselves and ambush prey.