Tag: acoustics lab

NOAA Teacher at Sea: Margaret Stephens
NOAA Ship: Pisces
Mission: Fisheries, bathymetric data collection for habitat mapping
Geographical Area of Cruise: SE United States continental shelf waters from Cape Hatteras, NC to St. Lucie Inlet, FL
Dates of log: Thursday, 19 May through Saturday, 21 May, 2011

Weather Data from the Bridge
Position: Latitude 27.87, Longitude -80.16
Wind Speed 11.06 kts
Wind Direction. 131.46 º
Surface Water Temperature 26.88 ºC
Surface Water Temperature
Air Temperature 27.10 ºC
Relative Humidity 78.00 %
Barometric Pressure 1015.50 mb
Water Depth 28.05 m
Sky conditions: clear

Science and Technology Log

General Description of the Scientific Work Aboard Pisces
While at sea, the ship’s operations and scientific crews work in shifts 24/7 – yes, that’s twenty-four hours, every day, with ship operations, maintenance, data collection and gear deployment continuing day and night.
The scientific team, headed by Chief Scientist, Dr. Nate Bacheler, includes researchers who are mostly marine biologists specializing in fisheries. Each team member has complementary specialized skills such as acoustics (use of sonar for sea floor mapping), physical or chemical oceanography, underwater video camera operations, data management and analysis, and many aspects of fish biology.

The main mission of this research cruise is to study red snapper and related grouper species, fish that are of great importance economically and to the marine ecosystem in near shore areas off the southeastern coast of the United States. In particular, the team is studying where the fish are likely to be found (their spatial distribution patterns) and their numbers, or abundance, and population dynamics (how the populations change over time).

This work expands the knowledge needed to guide decisions about how to protect and manage fisheries in a sustainable manner. Healthy, sustainable fish populations are essential to the economy, to the function of healthy ecosystems, and as high-protein (and tasty) food sources. In the past, many fish species have been overfished, resulting in dangerous declines in their populations.
The scientific work on board Pisces for this project is divided into three main areas. This log entry gives an overview of each of the three main areas of work, with a more detailed account of the acoustics, or mapping portion. Upcoming logs will describe the other phases in more detail.

1. Acoustics – Using the science of sound with advanced sonar and computer technology, the acoustics team maps the sea floor and identifies areas likely to be good fish habitat.
2. Fish survey – The survey team sets baited traps to catch fish, then collects them, identifies the species, and records essential data about the species of most interest.
3. Underwater videography – The video team attaches cameras to the traps to view the kinds and activities of fish in the water and assess the type of sea bottom, such as sandy or hard, flat or “bumpy”, regular or irregular.
4. After all this information is collected in the field, much of the painstaking, detailed analysis takes place back in the home labs and offices of the researchers.

Acoustics Work
Since acoustics is the first step used to identify specific sites to set traps for the fish survey, we’ll start here.
Throughout a long night shift, from 6 p.m. until the work is complete, often 7 a.m. or later the following day, the acoustics team uses sonar (SOund NAvigation and Ranging) and computer analysis to map the sea floor and identify promising areas to set traps for the fish survey. See a detailed description of the sonar equipment and procedures below.

At 5 a.m., the acoustics team meets with Chief Scientist Nate to report any sites they identified overnight and select the stations to sample with fish traps and underwater cameras during the day. The team then converts their data into a kind of route map that the helmsman (the ship’s “driver”) uses to steer the ship along the designated survey route.

The acoustics team members possess extensive knowledge about fish habitats, geography and geology of the sea floor, and computer and sonar technology. They also need to be aware of the interactions among wind, weather and currents and understand charts (marine maps) and ship’s navigation. They constantly communicate with the ship’s bridge via the internal radio network.

The acoustics lab houses work space large enough for five to ten people, banks of computer screens, servers, and large-scale display monitors projecting images from the sonar devices, real time navigation, and views from cameras positioned in work areas on deck.

Once the now-very-sleepy acoustics lab team wraps up its nocturnal work, the team members turn in for a day’s (or night’s?) sleep, just as the other teams’ daylight tasks begin in earnest.

Fish Survey Work
By 6 a.m., in the predawn darkness, the rear deck becomes a hub of concentrated activity, with sounds muffled by the early ocean haze and drone of the engines and generators. The four or more members of the fish survey team, still rubbing sleep from their eyes, assemble on the stern deck (rear of ship or fantail) to prepare the traps to catch fish for the day. Before the sun rises, floodlights illuminate the work of cutting and hanging menhaden, whole fish bait, in the traps, securing the underwater cameras in place, tagging each piece of equipment carefully and checking that everything is ready for deployment.

Chief Scientist Nate directs the deployment of the traps from the dry lab, where he faces a bank of computer screens displaying maps of the identified sampling route, the ship’s course in real time, and camera shots showing the personnel and operations on deck. By radio, Nate directs the deck crew to lower the traps at each of the designated sites.

The ship is steered along the sampling route, dropping traps in each of six locations. Each trap is left in place for approximately ninety (90) minutes. Once the last trap is lowered, the ship returns to the first location and raises the traps, usually following the same order. The deck crew members, together with the fish survey team, empty any catch and ready the traps for redeployment.
Chief Scientist Nate Bacheler directs trap deployment from the dry lab

Then the fish survey team, coordinated by Investigator Dave Berrane, sets to work sorting, weighing and measuring any catch and immediately releasing any fish not needed for further study.

Videography Work
As soon as the traps are hauled aboard by the deck crew, the wet lab team detaches and dries the cameras and hands them to the dry lab, where the videography team, headed by Investigator Christina Schobernd, removes the memory cards and transfers and makes duplicates of the video files on computer drives. All the teams take extreme care to label, catalog and back up everything carefully. Data management and redundancy are essential in this business. The scientists view some of the footage immediately to see if the cameras are working properly and to make any adjustments necessary. They also look for anything unusual or unexpected, any fish captured on camera other than those that made it into the trap, and they assess how closely the sea floor type matched what was expected from the acoustic team’s mapping work.

Christina works well into the night to back up and catalog all the day’s video recordings.

Detailed Description of Fisheries Acoustics Surveys

Fisheries Acoustic Surveys: Acoustic surveys help determine the relative abundance of target species and provide information to determine catch rates and guidance for fisheries management.

The equipment aboard Pisces includes two types of sonar devices that use sound waves to measure the water depth, shape or contours of the sea floor, and to a limited extent, fish groupings, or aggregations. Sonar operates using established knowledge about how fast sound travels in water under different conditions to develop a three-dimensional image of the shape of the sea floor. The first type is known as split-beam sonar, which uses sound waves at different frequencies to provide a picture of the underwater environment. Pisces has a Simrad EK60 echosounder.

The second, more sophisticated and expensive system involves Multibeam sonar mapping. Aboard Pisces is a Simrad ME70 device. Multibeam devices emit sound beams that forms an inverted cone, covering a larger area and providing a more complete picture of the sea floor than the series of vertical or horizontal sound signals that the split beam sonar provides. As described above, the bathymetric mapping surveys are conducted primarily during the night, from sundown until dawn, when fish sampling and other ship operations are not taking place. Ideally, this allows the science team to map out a route of sampling sites for the next day’s fish trapping work. At the end of the overnight shift, the acoustics team presents its findings to the Chief Scientist, who then coordinates the day’s activities with the fish team, the ship’s bridge, and the deck crew headed by the chief boatswain.

It’s called “multibeam” because unlike the first single-beam sonars, which sent out one signal or ping, multibeam sonar sends out a whole group of pings at once. Multibeam sonar can cover a larger area than a single beam can. Here’s a Quicktime movie of multibeam sonar: http://oceanservice.noaa.gov/education/seafloor-mapping/movies/multi_240.mov

Personal Log

I cannot say enough about how friendly and helpful everyone on board has been to this neophyte. It takes a while to adjust to any new environment, but being on a ship at sea has its own learning curve. Pisces, at 209 feet long, operates like a small town. Because it is out at sea for weeks at a time, all supplies and systems must be operating 24/7 to keep the ship and crew focused on the appointed mission and keep everyone on board safe, comfortable, and able to do their jobs.

I spent the first two days getting acclimated to the layout of the ship, safety practices, meeting the members of the scientific crew, adjusting to the rigorous schedule, and doing my best not to commit any grave offenses or make big mistakes that would make the work of this very patient group of dedicated professionals any more difficult than it is already.

Sleep Time Because the ship’s work continues round the clock, sleep time varies, depending on the person’s position and duties. It is important for everyone aboard to be mindful that at any hour of the day or night, it’s likely that someone is sleeping. The mapping crew began a 6 p.m. to 6 a.m. shift (or later, until the work is finished) on our second day at sea, and most of them will keep that difficult schedule for the entire cruise. Since I’m the lucky one to experience every aspect of the work, I’ll rotate through the various jobs and schedules. For the first few days, I’ll work with the fish survey team, from 6 a.m. until their work is completed, which may mean a break for supper at 5 p.m. followed by a few more hours of lab work to process all the day’s catch. My first day on the acoustics team, I’m scheduled to start at 4 a.m. assisting their nightly wrap up, as by the last few hours of their shift, they are quite tired.

Dining and Comforts Aboard Ship

Chief Steward Jesse Stiggens and Assistant Steward Michael Sapien create a terrific, appetizing menu for the three main meals and plenty of extras and snacks available at any hour.

The stewards are very accommodating, so anyone who will miss a main meal because of their work or sleep schedule can sign up in advance for the stewards to set aside a full plate of delicious food for them. The mess (dining room on a ship) is open all day and night, with coffee, cold beverages, an array of sandwich fixings, cereals and assorted leftovers kept chilled for anyone to microwave anytime they get a hankering for a nibble or a bigger bite. And…very important for morale … there’s a freezer stocked with ice cream, even Blue Bunny (a favorite in the South that I had not seen before) and Häagen-Dazs. There’s also a big screen television in the mess. The lounge area has computers, a conference or game table, a small library of books, a large screen television and several hundred movie titles, even new releases, for the crew to enjoy in their off time. Also available are wonderful reclining chairs, so comfortable, I wish I had time to use them. The one and only time I tried one out, the fire alarm went off for our first drill, and I haven’t had a free moment since.

Doomsday Came and Went: Saturday, 21 May, 2001….and Pisces work continues
CNN reports: After months of warnings and fear, the Day of Rapture, as predicted by apocalyptic Christian broadcaster Harold Camping, passed without apparent calamity. Judgment Day was to have started at 6 p.m., but as darkness fell on many parts of the world, it appeared that heaven could wait. At this writing, there have been no reports of people soaring upward to the skies, but plenty of folks are talking about it.

That includes those of us on Pisces. The possibility that Doomsday was approaching generated some good-natured kidding and gallows humor. We had some debate about when the end would begin. Since most of the ship’s instruments use Greenwich Mean Time (GMT) as a reference, we speculated that our end time might occur four hours later than east coast Daylight Savings Time (DST).

Everyone had their eyes on the clock and the horizon as first, the predicted doomsday hour of 6 p.m. DST came and went, and then, four hours later, 6 p.m. GMT passed without incident. Any apprehensions were put to rest, and now we have new fodder for discussion.

Special Challenges for Research at Sea
Many people have the idea that science is neat, pretty and conducted in sterile lab environments by other-worldly thinkers in clean white lab coats. That is decidedly not the case in fisheries work at sea. This section lists the special challenges (or, as, some optimists would say, “opportunities”) of conducting shipboard research. Each log will focus on or give examples of one or more challenges.

• Limits of “shooting in the dark” – Imagine a vast, dark, deep, ever-changing, difficult-to-penetrate area, with living organisms moving about in and out, with all kinds of surface, bottom, and in-between conditions. That’s what underwater research involves. Examples: The mapping team thinks it has found great habitat for red snapper and grouper, so the survey team expects a bountiful trap. But up comes nothing but a trap still full of untouched bait. Or, the habitat conditions look promising, but the current is too strong to set the traps safely.
• The Unexpected – It is often said that the only thing predictable in field research of this kind is unpredictability! You just never know….
• Curiosity-seekers and just plain business – recreational and commercial boats – Not surprisingly, the areas of interest for NOAA fisheries research are often favorite fishing grounds for recreational fishermen, scuba divers, and active routes for commercial ships. Therefore, Pisces crew and helm (the person steering the ship) must always be on alert for other boat traffic. Example: On Saturday, a small recreational boat occupied by partiers pulled up nearly alongside Pisces. Despite polite cautions and requests from our bridge for the small boat to move away to a safer distance, the visitors just kept waving and cheering for a while.

Challenges to come in next logs:

• Changing sea conditions, weather, waves and current
• Fatigue
• Limited daylight hours
• Emergencies
• More unpredictables

Links & Resources

• Photos of Life at Sea from the Pisces
• Pisces Ship Specifications
• NOAA Fisheries Service http://www.nmfs.noaa.gov/
• NOAA Career Fields
• FishWatch – What you need to know to choose safe, sustainable seafood
• NOAA Opportunities for Students – scholarships, internships and fellowships for undergraduate and graduate students
• Careers in Marine Sciences http://www.marinecareers.net/
• Colleges and Universities with marine science-related programs http://www.marinecareers.net/links_degrees.php
• Internship and Volunteer Programs in marine and environmental sciences
• Seafloor mapping NOAA Ocean Service Education