Combining expertise makes for better nautical charts and better understanding of fish habitats in Alaska   Leave a comment

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.

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