Acoustic Scattering Patterns in Puget Sound Over the Summer Period

Food web interactions are strongly influenced by heterogeneity of prey and consumers across time and space. We describe distribution patterns in acoustic backscatter from epi-pelagic fishes over the critical summer growth period in Puget Sound during 2011.  This period is critical for growth of ESA-listed Chinook salmon (Oncorhynchus tshawytscha); summer growth has been linked to survival at sea. Nearshore and offshore transects were conducted at 14 consistent sampling sites monthly from April to September 2011, providing data that span the entire summer period.  A towed body with a downlooking 200 kHz Biosonics transducer was deployed at each site.  Sites were distributed across four areas of the Sound: South Puget Sound, Central Puget Sound, Admiralty Inlet, and Whidbey Basin.  Schooling biomass was classified and separated from non-schooling biomass.  These data illuminate movement patterns of biomass over the summer period and provide critical background for population studies of juvenile salmon and research into potential competitive interactions within and among salmon species, Pacific herring (Clupea pallasi), and other forage fishes in Puget Sound.