Today’s post is written by a guest blogger, Dr. Bob McConnaughey. Bob is the FISHPAC project chief scientist, with NOAA’s Alaska Fisheries Science Center.
Fishery biologists and hydrographers in NOAA are working together to solve two very important problems in the eastern Bering Sea. This area is one of the richest and most productive fishing grounds in the world. Careful management of harvest levels is one part of the effort to sustain these populations into the future. However, it is also important to understand the habitat requirements of the managed species so we can protect the foundation for these high levels of production.
To this end, a team of scientists at the Alaska Fisheries Science Center (AFSC) is developing mathematical models to explain the distribution and abundance of groundfish, such as pollock and cod, and benthic invertebrates, such as red king crab, in order to determine their essential habitats. The research team gathers new environmental data at locations where other AFSC scientists sample fish populations during annual bottom-trawl surveys. In many cases, existing habitat information is very limited, but studies will identify useful variables and the best tools for measuring them over large areas of the continental shelf.
NOAA hydrographers working in Alaska are likewise challenged by the sheer size of the offshore areas and the dearth of recent depth measurements. This region includes over 47,000 miles of coastline and roughly 70% of the nation’s continental shelf. Soundings data for nautical charts are usually quite old and coverage is incomplete. Similar to the habitat studies, there is a great need to gather new data, efficiently and cost-effectively.
A diverse team of NOAA personnel and external partners are collaborating to address the critical need for new habitat data and new hydrographic data from the eastern Bering Sea. Beginning in 2006, NOAA Ship Fairweather has conducted multi-mission cruises to simultaneously achieve these two objectives. The so-called FISHPAC project has developed procedures to collect acoustic backscatter data to characterize seafloor habitats while also collecting high-quality bathymetric data for updating nautical charts.
This joint effort has been a great challenge for two groups that have typically worked alone, generally focusing on a single specialized activity. The successful integration of these activities makes efficient use of valuable ship time and will ultimately increase the amount of data collected for both purposes in a single survey season.
The prototype long-range side scan sonar is prepared for deployment. An emergency locator beacon is activated to help locate the towfish if it becomes detached from the double armored tow cable.
The AFSC scientists have introduced new types of equipment on Fairweather for this work, including a prototype side scan sonar capable of very broad coverage (up to 1 km) at a fast tow speed (up to 12 kts), an acoustic underwater tracking system that provides accurate positions for towed instruments, and several “groundtruthing” instruments to help interpret the backscatter data for habitat purposes. The partners have worked out safety and deployment details, and now the ship can simultaneously acquire acoustic data from the ship’s two multibeam echosounders and a towed side scan sonar, while underway and collecting sound velocity profiles and geotechnical data from the seafloor with a free-fall cone penetrometer! Operating this way, the ship does not need to stop; they can conduct survey operations around the clock during the entire time at sea.
Fairweather hosted a major FISHPAC cruise during July-August 2012. A team of 12 scientists joined the Fairweather’s standard crew of officers, physical scientists and seamen to conduct a combined fish-habitat and hydrographic-survey effort in the eastern Bering Sea. The group worked together ‒ night and day ‒ to acquire the multi-purpose data. They tested five different sonar systems in an experiment designed to identify the most cost-effective system for characterizing the seafloor and improving the existing fish-habitat models. At the same time, the ship collected over 1,000 nautical miles of hydrographic data in an area with outdated or non-existent information.
Technicians from the Naval Undersea Warfare Center (Keyport, Washington) and a retired NOAA engineer and hydrographer provided valuable assistance.
Neither high seas, nor fatigue, nor equipment problems stopped the intrepid group. The project was fully successful in the end and Fairweather safely returned to port in Dutch Harbor, Alaska to discharge some scientists and then head back out on her Arctic Reconnaissance voyage.
The towed auto-compensating optical system (TACOS) is a two-part towed video system consisting of a weight sled connected to the ship’s fiber optic winch, with a camera sled trailing approximately 20 meters behind the weight sled. The camera sled includes an analog video camera, a digital video camera, six high intensity discharge lights as well as an acoustic release/buoy for emergency recovery. TACOS creates high-quality downward-looking video mosaics.
Before we get to the Fairweather logs, we need to update the last post, NOAA Ship Fairweather zigzags her way to accurate and precised depth soundings. Cmdr. Crocker reports that the “normal” zigzagging won’t start until they head further north, starting near Point Hope. It was not planned for the trip to Kotzebue, and he would have run a straight course if he could have. This log by Ensign Hadley Owen explains why they zigzagged earlier than planned, as well as what they are doing for their first scientific project. We apologize for the error in the last post. -DF
Fairweather Log Entries, August 2 and August 5
by Ensign Hadley Owen, NOAA, Junior Officer, NOAA Ship Fairweather (S-220)
2400 hours, Thursday, August 02, 2012: 57°04.9’N 167°05.5’W, underway, Dutch Harbor to Kotzebue Sound
We left Dutch Harbor on the NOAA Ship Fairweather on August 1, to begin our 30-day reconnaissance trip bound for the Arctic. Our departure had been delayed until 1800 on Wednesday in order to let pass a 988 MB low-pressure system moving northeast through the Aleutians. Our initial plan was a straight line running generally west by north, on which we would acquire seafloor data using the ship’s hull-mounted multibeam echo sounder and a towed Klein 7180 long-range side scan sonar (a one-of-a-kind device designed to maximize the effectiveness of broad-scale fish habitat studies using acoustic “backscatter”). However, a persistent 8’ swell on the ship’s beam resulted in a more than 20-degree roll that kept many crewmembers in their beds and made useful data acquisition nearly impossible. Cmdr. James Crocker, commanding officer of the Fairweather, made the call to alter course in order to pass over the acquisition stations in a tacking motion – zigzagging our way north in order to minimize the effects of the swell on our ship’s data collection activities.
The first leg of our Arctic cruise is focusing on work conducted for NOAA’s National Marine Fisheries Service, and led on the Fairweather by Dr. Bob McConnaughey. He and his team of NOAA scientists and Navy technicians have been studying and mapping benthic regions in the eastern Bering Sea since 1996, addressing a congressional mandate to understand the habitat requirements of the nation’s managed fish and crab populations. Their recent work has focused on using a variety of sonars to identify seafloor properties that affect the distribution and abundance of fish, including the Fairweather’s multibeam echosounders (traditionally used for hydrographic surveying) and side scan sonars that can continuously survey a swath of seafloor up to a kilometer-wide, at a maximum speed of 12 knots. The project goal is to measure backscatter from the ocean’s bottom, rather than to simply produce images of it, and to use this information in combination with other environmental data and estimates of fish abundance from annual bottom trawl surveys to improve the team’s mathematical models that identify the habitat requirements of individual species. At the same time, we are taking care to produce hydrographic-quality bathymetric data for updating nautical charts in areas with outdated or non-existent information – a great example of NOAA’s integrated ocean and coastal mapping strategy.
The NOAA team onboard Fairweather during the NMFS fish research project
The NMFS team’s broader interest in the Fairweather’s reconnaissance mission is to be at the forefront of activity documenting the areas that are opening up as the region’s ice-cover retreats. By this work, NOAA’s intention is to be well prepared to support fishery management decisions related to emerging uses: commercial fishing, large-scale shipping and navigation, and oil exploration interests. The team aims to document similarities and differences in the seafloor habitats found along the more than 1,000 km reconnaissance line extending from Dutch Harbor in the Aleutian Islands to the Kotzebue Sound area above the Arctic Circle. The data collected from the eastern Bering Sea, the northern Bering Sea and the Chukchi Sea will provide insights about possible outcomes if fish populations redistribute northward due to environmental change. It will also help us to understand the susceptibility of these areas to new forms of human disturbances.
Fairweather deploys the Klein side scan sonar
As of the end of Thursday, August 2, the seas have settled down and allowed the Fairweather to deploy the long-range side scan sonar and begin acquiring data. Depending on conditions, the sonar’s towfish will remain in the water until the northern end of the survey line near Kotzebue. In addition to backscatter data, the side scan sonar is also acquiring data about water column properties such as chlorophyll.
We are keeping a close eye on ice conditions for the latter part of our route. The current ice edge runs to Barrow, and will at present prevent us from completing the last leg of our track in the Beaufort Sea – along the north coast of Alaska and east to the Canadian border. However, any data obtained during this reconnaissance mission will initiate a new large-scale systematic study of the region’s benthic habitats, will provide new bathymetric data for nautical charts, and will ultimately create a foundation for appropriate management and safe navigation in the region’s future.
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1800 hours, Sunday, August 5, 2012: 67°00.8’N 165°35.5’W, heading east, Kotzebue Sound, north of the Arctic Circle
We have been transiting increasingly shallow water since we passed Nunivak Island. As the Klein 7180 operates best in depths greater than 20 fathoms, we were able to take advantage of improved weather and relatively calmer seas to bring the towfish on board yesterday morning. However, data acquisition continues with the ship’s multibeam echo sounder.
At 1400 hours we crossed the Arctic Circle (66°33’N), heading northeast towards the town of Kotzebue. Dr. Bob and his crew will disembark the Fairweather early Monday morning and we will shift focus with a new team of scientists as we continue north. As we transit to our anchorage near the head of the Sound this evening, we will navigate using the newest chart (16161) of the area. NOAA produced Chart #16161 in May, using survey work conducted on the Fairweather last summer; it will be an inspiration for the work to come.