AFSC/RACE/GAP/McConnaughey: South Arctic Reconnaissance

A custom designed Klein 7180 towed sonar was deployed from the NOAA Ship FAIRWEATHER to determine its value of acoustic backscatter as a habitat defining character. A Sonardyne Fusion USBL system was used to estimate underwater positioning of the towfish using an omnidirectional Wideband submini beacon operating in external trigger mode. Navigation data were logged in QINSy and exported into a text file. The towfish positions were then smoothed in Matlab using a custom script that implemented a weighted Hamming filter, using a window of 11 data points. These points represent the smoothed USBL navigation data for the Klein 7180 towfish during the Arctic reconnaissance transit from Dutch Harbor to Kotzebue. These smoothed towfish navigation data, however, will NOT ultimately be reinserted back into the sonar files for mosaicking and analysis. Rather, another navigation smoothing routine will be used for the final product.

The broad scope of the Essential Fish Habitat (EFH) mandate requires an efficient process for describing and mapping the habitat needs of federally managed species. For example, research indicates surficial sediments affect the distribution and abundance of many groundfish species, yet traditional sampling with grabs and cores is impractical over areas as large as the Bering Sea shelf. Acoustic tools are suitable for large-scale surveying and show great promise as a substitute for direct-sampling methods, but they have not been proven useful for EFH purposes. Acoustic seafloor surveys using different sonar systems were conducted along strong gradients of groundfish abundance, as determined from many years of RACE bottom trawl survey catches at fixed stations. Ultimately, the value of acoustic backscatter as a habitat defining character will be judged based on the statistical association between normalized backscatter and fish density. The benefits and costs of the different acoustic systems will be compared with data from multiple passes along the survey tracklines. Sediment samples, video and infauna collected along each trackline will provide additional biological and geological information for the analyses. Immediately following the Fishpac project during the summer of 2012, a single trackline was made between Dutch Harbor and Kotzebue Sound and various types of data were collected along the transit to get a glimpse at the seafloor habitat along the way.

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see Process Steps