The Resource Assessment and Conservation Engineering (RACE) Division of the Alaska Fisheries Science Center (AFSC) conducted a survey in the eastern Bering Sea (EBS) to evaluate short-term impacts of bottom trawls on soft-bottom benthic habitats and to describe the recovery process. This was a multi-year project which follows earlier studies of long-term bottom trawling impacts in the same general region. The study area was within the Crab and Halibut Protection Zone 1 in Bristol Bay (management area 512; approximately latitude 58 degrees north and longitude 160 degrees west. In general, at-sea work was divided into three phases: (1) integrated biological and geological sampling before experimental trawling, (2) experimental trawling and (3) integrated biological and geological sampling after experimental trawling. Survey activities were conducted aboard the 47.2 meter (155 ft) chartered vessel Ocean Explorer. This was a commercial fishing vessel modified to support the research activities. Activity during phase 1 consisted of side scan assessments of seafloor morphology with an interferometric Klein 5410 side scan sonar towfish during night wheel watches, and epifauna trawls and collection of infauna and sediment grabs during daylight hours. All samples from a particular gear were collected in succession, so as to minimize time spent installing and configuring gear during phases (1) and (3). Assessment activities after the impact phase were a repeat of activities prior to experimental trawling.

The Resource Assessment and Conservation Engineering (RACE) Division of the Alaska Fisheries Science Center (AFSC) conducted a survey in the eastern Bering Sea (EBS) to evaluate short-term impacts of bottom trawls on soft-bottom benthic habitats and to describe the recovery process. This was a multi-year project which follows earlier studies of long-term bottom trawling impacts in the same general region. The study area was within the Crab and Halibut Protection Zone 1 in Bristol Bay (management area 512; approximately latitude 58 degrees north and longitude 160 degrees west. In general, at-sea work was divided into three phases: (1) integrated biological and geological sampling before experimental trawling, (2) experimental trawling and (3) integrated biological and geological sampling after experimental trawling. Survey activities were conducted aboard the 47.2 meter (155 ft) chartered vessel Ocean Explorer. This was a commercial fishing vessel modified to support the research activities. Activity during phase 1 consisted of side scan assessments of seafloor morphology with an interferometric Klein 5410 side scan sonar towfish during night wheel watches, and epifauna trawls and collection of infauna and sediment grabs during daylight hours. All samples from a particular gear were collected in succession, so as to minimize time spent installing and configuring gear during phases (1) and (3). Assessment activities after the impact phase were a repeat of activities prior to experimental trawling.

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.

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.

In early 1996, Quester Tangent Corporation (QTC) and the National Marine Fisheries Service (NMFS) Alaska Fisheries Science Center (in Seattle) formed a strategic alliance to apply QTC seabed classification technology to the problem of groundfish habitat descriptions. The Bering Sea supports about 300 fish species, many of which are demersal species. This stock supports sizeable fisheries, as indicated by landings at the Bering Sea port of Dutch Harbor in excess of 579 million pounds in 1996 and 678 million pounds in 1999 (the highest in the U.S.). By comparison, in 1981 the landing at Dutch Harbor was 73 million pounds. This rapid increase in catch highlights the need for effective management to ensure sustainability. After connecting the QTC VIEW full waveform acquisition system (ISAH-S) to the Simrad EK-500 scientific echosounder on the NOAA ship Miller Freeman, over 9,000 miles of track line data were collected in the eastern Bering Sea between June and August 1999. The raw data consist of digital echo traces of the full water column and seabed substrate. They were collected at two frequencies, 38 kHz and 120 kHz. Based on an average rate of one ping recorded per second, approximately four million individual echoes at each frequency were obtained. The data within this raster set represent the results of processing channel 38_12, which incorporated the 38 kHz frequency data, using a reference depth of 90 meters and stacks of 50 echoes to create a single classified data point through the PCA analysis. A rasterized grid was created from each Q value and then grid stacked to allow RGB representation of each data point in continous Q- space as opposed to categorical class.

Environmental variables that are ecologically relevant and easily measured over large areas are useful for modelling species distributions and habitats. Continuous acoustic, sonar-backscatter data convey information about physical properties of the seabed, and hence could be a valuable addition to that suite of variables. The potential utility of acoustic backscatter was tested for improving habitat models of marine species using data from a pilot sidescan-sonar survey conducted from 28 June to 3 July 2002 in the Bristol Bay region of the eastern Bering Sea (EBS). Raw digital backscatter data were processed with QTC SIDEVIEW and CLAMS software to objectively segment bedform based on statistical analysis of the echograms. Resultant acoustic variables - Q-values (Q1, Q2, and Q3)-, representing the first three principal components of the data derived from image analysis of backscatter echoes, and a complexity metric (compx) measuring the variance of Q-values in a geographic area - were used in multiple linear regression to model individual species abundance from bottom-trawl survey data.

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.

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.

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.

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.