NOAA Teacher at Sea Melissa George Aboard NOAA Ship Oscar Dyson July 22 – August 9, 2013
Mission: Pollock Survey Geographical Area of Cruise: Gulf of Alaska Date: Thursday, July 25, 2013
Current Data From Today’s Cruise
Weather Data from the Bridge (at 6:00 am Alaska Daylight Time) Sky Condition: Fog
Temperature: 12° C
Wind Speed: 11 knots
Barometric Pressure: 1017.5 mb
Humidity: 87%
Sun and Moon Data
Sunrise: 5:51 am
Sunset: 10:40 pm
Moonrise: 10:57 pm (July 24, 2013)
Moonset: 10:37 am
Geographic Coordinates (at 6:00 am Alaska Daylight Time)
How can you determine the population size of species? You could count every member of the population. This would be the most accurate method, but what if the individuals in the population move around a lot? What if the population is enormous and requires too much time to count each individual? For example, krill is a small crustacean (usually between 1 and 6 cm long) that accounts for 400-500 million metric tons of biomass in the world’s oceans. Would you want to count all of the krill in the Gulf of Alaska?
Krill (and a Few Capelin)
Often, ocean populations of animals are just too large to count. Sampling, or collecting a manageable subset of the population and using the information gathered from it to make inferences about the entire population, is a technique that ocean scientists use. There are a variety of ways to sample.
One method is called mark and recapture. In this method, one catches individuals from the population, tags them, and releases them in a certain area. After a set amount of time, an attempt is made to recapture individuals. Data are compiled from the recaptures and the population is mathematically calculated. Tuna populations in some areas are monitored this way; fishermen are required to report any fish that are recaptured. (Photo courtesy of Western Fishboat Owners’ Association)
Tuna with Tag Locations
Another method is quadrat sampling. The organisms in a subset area (quadrat) are counted and then the overall population in the entire area is calculated. For example, in the picture below, one quadrat would be randomly selected and the organisms counted. From this count the overall population would be extrapolated. (Photo courtesy of BBC Bitesize Biology)
Quadrat Sampling
The sampling method used on the Oscar Dyson employs the use of a transect line. The picture below illustrates the use of a transect line. On various increments along the transect line, samples of populations are taken. Imagine the Oscar Dyson’s path on the sea as the measuring tape and the trawl net is the sampling square. (Photo courtesy of Census of Marine Life Organization)
Transect Line Sampling
The overall survey area of the pollock study this summer is the northern Gulf of Alaska between the shore and the continental break. Within this area transect lines were established. These are pathways that the Oscar Dyson will travel along and periodically take samples of the fish.
The current set of transects are 25 nautical miles apart and are parallel, but transects in other areas may be 2 or 5 nautical miles apart. One nautical mile is equal to 1/60 of a degree (or 1 minute ) of latitude. Transects that we are following now are located on the shelf and are perpendicular to the coastline. Transects in inlets and bays may run differently, perhaps even zigzag.
Screen Shot of Oscar Dyson Transect Line Travel
If fish are located through acoustics monitoring off the transect line, the ship might break transect (a mark is made on the map), circle around to the desirable position, and collect a sample by trawling. The population of pollock can then be mathematically calculated from counting the sample. After trawling, the ship will return to the break and continue along the transect line.
Most days, scientists hope that the Oscar Dyson will finish a transect line by nightfall and then the ship can be at the next transect by sunrise. This maximizes the time for detecting fish acoustically and trawling to collect samples.
Personal Log:
In his 1943 paper “A Theory of Human Motivation,” Abraham Maslow, a developmental psychologist, proposed a hierarchy of needs which focus on describing the stages of growth in humans. The largest, most fundamental needs are at the bottom, and as those are satisfied, individuals are able to progress up the pyramid. So, I am going to use this diagram (somewhat tongue-in-cheek) to discuss how basic needs are met on the ship. In today’s blog, I will begin the discussion at the bottom level (where else?).
A Version of Maslow’s Hierarchy of Needs
The bottom layer includes the most basic physiological needs one requires for survival: food, water, warmth, and rest. (We might also include exercise in this level). So, let us begin at the beginning.
Food
Food is available in the galley. It is planned for and shopped for before the mission. Chief Steward, Ava, and Second Cook, Adam, do an excellent job preparing and executing delicious, healthy meals at set times during the day (Breakfast: 7 to 8 am, Lunch 11 am to noon, Dinner 5 to 6 pm). Since the staff on the ship are working around the clock, there is always food available (salad bar, cereal, yogurt, peanut butter and jelly sandwiches) if meal time is missed for sleeping. Below is a photo of the galley. (What are those neon yellow things on the bottom of the chair legs for, do you think?)
Oscar Dyson Galley
Water
Water is needed for in several capacities on the ship. The staff on the ship needs potable water to drink and to cook with. Additionally, water is needed for washing dishes, bathing, flushing toilets and doing laundry.
To get clean drinking water, we pump the salt water from the ocean into a desalination unit (a distiller). The distilled water is then sent to a 10,000 gallon holding tank. When water is needed, it is pressurized so that it will move to the faucets, drinking fountains, showers, and so on.
Water is also needed on the ship in the lab and on the deck to clean up after the catch is hauled in and processed. The water used here is salt water and is pumped onto the boat directly from the ocean.
Rest
Half of the staff on the ship is working around the clock; the other half is resting. For the science staff, there are two shifts, a morning shift (4 am to 4 pm) and an evening shift (4 pm to 4 am). The shifts are staggered at these hours so that the evening shift will be able to share two meals with the rest of the staff (usually lunch and dinner). In most cases, two people share a stateroom: one works days and the other works nights. Because the quarters are close on a ship, this gives each person some time alone in the room to sleep, bathe, and take care of other personal needs. A stateroom consists of a bunk bed, a desk, two lockers, and a bathroom/shower. Below are some photos of the stateroom that I share with my roommate, Abby. (Note: Because rooms are small and space is shared, it is not advisable to bring a large purple suitcase that won’t fit inside one’s locker.)
Oscar Dyson StateroomOscar Dyson Stateroom Bath
Exercise
There are two workout areas on the ship. One workout area has a treadmill, an elliptical machine, a bike, and a yoga mat; the other has a treadmill, a rowing machine, and some free weights. There are limited walking spaces on the ship, so these machines provide a way to stretch one’s legs, so to speak.
Oscar Dyson’s Exercise Room
Did you Know?
With a bachelor’s degree in science, math, or engineering and a 6 month training program at the US Coast Guard Academy in New London, CT, one can serve the United States as a member of the National Oceanic and Atmospheric Administration’s Commissioned Officer Corps (NOAA Corps). Members of the NOAA Corps serve as operational experts, taking researchers to sea and helping to generate environmental intelligence. My roommate, Abby, serves as a member of the NOAA Corps.
Abby Controlling the Oscar Dyson
This is Abby’s second cruise with the NOAA Corps. She has a bachelor’s degree in chemistry and just completed her NOAA officer basic training. One of her tasks is to be ready to deploy specific measures in case of a fire on board. Below, she is reviewing all of the locations on the Oscar Dyson with fire response equipment. For more information on NOAA Corps, click on the link.
Abby Locating Fire Response Equipment
Something to Think About
Knowing geography is essential to various positions on the ships such as scientific exploration and navigation. Many types of maps are seen on board, for example, computer generated bathymetric maps show the contour and depth of the ocean. Equally valuable are the “old school” tools (paper maps, compasses, straight edges, and pencils) used to plot the ship’s course.
Navigation ToolsPlotting Transects
Fun Fact
Etymology is the study of the origin of words. Many of the words in science originate from ancient languages such as Greek or Latin. For example, the word etymology comes to us from two Greek words: etymon meaning “the true sense of a word“ combined with logia meaning “doctrine, study.” Combining these two roots gives us “the study of the true sense of words,” which can be said to be the meaning of the word etymology.
Here are some root words I came across today all originating from Greek words:
zoo-from zoion meaning “animal”
phyto-from phyto meaning “plant”
plankton-from planktos meaning “drifting” or “wandering”
vorous-from vorous meaning “eating”
In the blogs thus far, I have discussed two species: walleye pollock and one of their prey, krill. Krill are classified as zooplankton, literally “animals that drift. ” Krill eat phytoplankton, or “animals that drift.” Pollock are considered to be zooplanktivorous, or “drifting animal eaters.” An award winning short video explaining The Secret Life of Plankton can be viewed by clicking on the link.
NOAA Teacher at Sea Avery Marvin Aboard NOAA Ship Rainier(NOAA Ship Tracker) July 8 — 25, 2013
Mission: Hydrographic Survey Geographical Area of Cruise: Shumagin Islands, Alaska Date: July 22, 2013
Current Location: 54° 55.6’ N, 160° 10.2’ W
Weather on board: Broken skies with a visibility of 14 nautical miles, variable wind at 22 knots, Air temperature: 14.65°C, Sea temperature: 6.7°C, 2 foot swell, sea level pressure: 1022.72 mb
Science and Technology log:
Rainier motto, painted in the stern of the ship above the fantail, the rear lower outside deck where we have our safety meetings.
“Teamwork, Safety First”, is inscribed boldly on the Rainier stern rafter and after being aboard for more than 2 weeks, it is evident this motto is the first priority of the crew and this complex survey operation at hand.
This is one of the survey launches that we use to gather our survey data. In this case, the launch is shown approaching the Rainier, getting ready to tie up.
It’s a rainy overcast morning here in SW Alaska and we are circled around the officers on the fantail for the daily safety meeting. Weather conditions, possible hazards, and the daily assignment for each launch are discussed. Per the instructions on the POD (Plan of the Day), handed out the previous evening, the crew then disperse to their assigned launches. The launches are then one-at-a-time lowered into the water by the fancy davit machinery and driven away by the coxswain to their specific “polygon” or survey area for the day. A polygon surveyed by a launch on average takes 2-3 hours at 6-8 knots to survey and usually is an area that is inaccessible by the ship. Many polygons make up one large area called a “sheet” which is under the direction of the “sheet manager”. Several sheets make up an entire survey project. Our hydrographic project in the Shumagins has 8 sheets and makes up a total of 314 square nautical miles.
The CO, XO, and FOO lead the safety meeting for the day, discussing weather conditions, water conditions, and the assignments for each launch.This is a chart of the Shumagin Islands showing the 8 sheets (highlighted in green) that we are surveying.East side of Chernabura Island divided into survey “polygons”, each labeled with a letter or word. Notice how each polygon is a small subset of the larger sheet.
On board each launch we have a complex suite of computer systems: one manages the sonar, another manages the acquisition software, and the third records the inertial motion of the launch as it rocks around on the water (pitch, heave, roll). The acquisition system superimposes an image of the path of the launch and the swath of the sonar beam on top of a navigational chart within the polygon. Starting at one edge of the polygon, the coxswain drives in a straight a line (in a direction determined by the sheet manager), to the other end of the polygon, making sure there is some overlap at the boundaries of the swaths. He/she then works back in the other direction, once again making sure there is some overlap with the adjacent swath. We call this “mowing the lawn,” or “painting the floor” as these are visually analogous activities. Throughout the day, we pause to take CTD casts so that we have a sound velocity profile in each area that we are working.
Typical launch dispersal for a survey day. Launches are signified by “RA-number”. You can also see the location of our tide measurement station and GPS control station, both of which we use to correct our data for errors.This image shows the software tracking the path and swath of the launch (red boat shape) as it gathers data, driving back and forth in the polygon, or “mowing the lawn.” The darker blue shaded area shows overlap between the two swaths. The launch is approaching a “holiday”, or gap in the data, in an effort to fill it in.
You might be wondering, why the swath overlap? This is to correct for the outer sonar beams of the swath, which can scatter because of the increased distance between the sea floor and the sonar receiver below the hull of the boat. The swath overlap is just one of the many quality control checks built into the launch surveying process. Depending on the “ping rate”, or the number of signals we are able to send to the bottom each second, the speed of the boat can be adjusted. The frequency of the sound wave can also be changed in accordance with the depth. Lower frequencies (200 khz) are used for deeper areas and higher frequencies (400 khz) are used for shallower areas.
Rosalind working the surveying computers in the launch
Despite what might seem like mundane tasks, a day on board the launch is exhausting, given the extreme attention to detail by all crew members, troubleshooting various equipment malfunctions, and the often harsh weather conditions (i.e. fog, swells, cool temperatures) that are typical of southwest Alaska. The success of the ship’s mission depends on excellent communication and teamwork between the surveyors and the coxswain, who work closely together to maximize quality and efficiency of data collection. Rain or shine, work must get done. But it doesn’t end there. When the launches arrive back at the ship, (usually around 4:30 pm), the crew will have a debrief of the day’s work with the FOO (field operations officer) and XO (executive officer). After dinner, the survey techs plunge head first (with a safety helmet of course) into the biggest mountain of data I have EVER witnessed in my life, otherwise known as “night processing”. We are talking gigabytes of data from each launch just for a days work. It begins with the transferring of launch data from a portable hard drive to the computers in the plot room. This data is meticulously organized into various folders and files, all which adhere to a specific naming format. Once the transferring of data has finished, the “correction” process begins. That’s right, the data is not yet perfect and that’s because like any good science experiment, we must control for extraneous factors that could skew the depth data. These factors include tides, GPS location error, motion of the launch itself, and the sound velocity in the water column.
Our chief surveyor works in the plot room cleaning and correcting data.Data showing the consequences of the tide changing. The orange disjointed surface shows the data before it was adjusted for the tide changing. You can see how the edges between swaths (i.e. red and olive green) do not match up, even though they should be the same depth.This image shows the edge effects of changing sound speed in the water column. The edges of each swath “frown” because of refraction owing to changing density in the water column. This effect goes away once we factor in our CTD data and the sound speed profile.
In previous posts, I discussed how we correct for tides and the sound velocity. We also correct for the GPS location of the launch during a survey day, so that any specific data point is as precisely located as possible. Although GPS is fairly accurate, usually to within a few meters, we can get even more precise (within a few centimeters) by accounting for small satellite errors throughout the day. We do this by determining the location of a nearby object (our Horizontal Control, HorCon, Station) very precisely, and then tracking the reported position of this object throughout the day. Any error that is recorded for this station is likely also relevant for our launch locations, so we use this as the corrector. For example, if on July 21, 2013, at 3pm, the GPS location of our Bird Island HorCon station was reported 3cm north of its actual location, then our launches are also probably getting GPS locations 3cm too far north, so we will adjust all of our data accordingly. This is one of the many times we are thankful for our software. We also account for pitch, heave, and roll of the launch using the data from the inertial motion unit. That way, if the launch rolled sideways, and the center beam records a depth of 30 meters, we know to adjust this for the sideways tilt of the launch.
This shows the set up of our Horizontal Control and tide gauge station. The elevated rock position was chosen to maximize satellite visibility.
After all correctors have been applied (and a few software crashes weathered), the survey technicians then sort through all the data and clean out any “noise.” This noise represents sound reflections on sea life, air bubbles, or other items that are not part of the seafloor. Refraction of sound waves, as mentioned in the last post, is caused by density changes in the water due to changes in the temperature, pressure, or salinity.
This shows sonar data with “noise”. The noise is the seemingly random dots above and below the primary surface. On the surface itself, you can see data from four different swaths, each in a different color. Notice the overlap between swaths and how well it appears to be matching up.This shows sonar data after the “noise” has been cleaned out. Notice how all data now appears to match a sea floor contour.
Many of the above correctors are applied the same day the data is collected, so the sheet manager can have an up-to-date record of the project’s progress before doing final planning for data collection the next day. After a sheet has been fully surveyed and ALL correctors applied, the sheet manager will complete a “descriptive report”, which accompanies the data and explains any gaps in the sonar data (“holidays”) and/or other errors present. This report, along with the data, is sent to the Pacific Hydrographic Branch for post-processing, and in 1-2 years, we will have a corrected and updated navigational chart. During this time the data is reviewed for quality and adherence to hydrographic specifications and then is distilled into a cartographic product (nautical chart) consisting of points, lines, and areas.
Personal Log:
So I am going to hold off in talking about an animal that has recently fascinated me and instead devote this personal log to some cool things I have been doing on the ship.
Most recently I got to be the helmsman and steer the ship. This involved me following orders from the “conning officer” who told me various steering commands such as: “Left ten degrees rudder”, “steady on course 167°”, “ease 5° right”, “helm in auto” (auto-pilot). To acknowledge the command, I repeated what the conning officer said followed by “aye”. For example: “Left ten degrees rudder, aye” or “course 167°, aye”. When the boat is actually on the course that was requested by the conning officer, I repeated the command with the word “steady”. For example: “Steady on course 167°”
Avery at the helm
You might be wondering why all of the commands involve degrees. Well that is because this ship is steered by the rudder, similar to how you manually steer a small sailboat. So changing the angle of the rudder will change the direction of the ship. To change this angle, you turn the steering wheel a desired amount of degrees beyond zero in the direction the conning officer instructed. So if he said “right 5 degrees rudder”, I would turn the steering wheel right, and stop at the 5 hash mark.
Once the boat actually turns 5°, I will make sure I am at the correct “heading” or degree mark that the conning officer instructed. A heading can be any number between 000-360 (where 000-deg = North, 045 = Northeast, 090 = East, etc.) as this boat can turn in a complete circle and be navigated in any direction. (There is 360° in both a compass and a circle.) Once I am steady at the correct heading, I will put the steering wheel back to 0° which means the rudder is completely straight and parallel with the boat. At this point the boat is going straight. If this were a car, you could just stay straight no problem.
But because this boat moves in water and is affected by ocean conditions such as swells, it is easily knocked off course of the heading. So as helmsman I am constantly making tiny adjustments with the steering wheel by a few degrees in either direction to maintain my heading. This adjustment is done using the steering wheel if I am driving manual, or using a dial on the gear panel if the boat is in “auto” (auto-pilot). Because the ship rudder must “push water out of the way” in order to steer the boat, there is a delay between when I turn the steering wheel to when the ship actually moves that amount of degrees. This is not a car which turns instantaneously by the movement of axles. So I need to account for that “lag time” as well as ocean conditions and the speed of the boat when turning the ship. For example, if the boat is going slow (3 knots) and I need to turn quickly, I will have to use a greater rudder angle. Throughout this process I have several digital screens that show me my current position and course, current heading and desired heading as well as other navigational aides. When I was helmsman, I was closely monitored and assisted by Jason, a former Navy Chief Boatswain, who is one of the best helmsman on the ship. To be a good navigator you need to know the fundamentals but you also need a lot of practice and exposure to various navigational situations.
Helm stand
Yesterday, Rosalind and I got to work on deck and help the Chief Boatswain with various deck tasks such as lowering the anchor and assisting with the davit to hoist the launches from their day of surveying out on the water. Assisting with the job of lifting a 16,000 lb launch with 3 people aboard using the davit winch was by far the most exhilarating experience thus far on the ship. I handled the task with extreme caution. As with being a helmsman, there are many factors I must consider as a davit operator. For example, if there is a significant swell, I need to be more aggressive with the davit movements to get the boat lifted fast to avoid any excessive swaying in mid-air. Most importantly, I must attentively follow the gestures of the deck boss below who is able to see the launch very clearly and is directing me on every davit movement. Even an experienced davit operator like Jason, who probably can predict the next davit movement in his sleep, must never assume and then act. He ALWAYS follows the exact orders of the deck officer below because he never knows what they are seeing that he cannot from the above deck. Overall, with Jason’s close attention and assistance, I think I did a good job of assisting with the davit. The boat made it safely aboard, and my heart returned to a normal beating pattern. 🙂
Getting the davit positioned and ready to lift the launch out of the water.
On a lighter note I learned how to play the good ole’ mariner pastime favorite, Cribbage. Rosalind (the other Teacher at Sea and my delightful roommate) taught me how to play. We had a cribbage tournament here aboard the ship in which about 12 people competed. I did not advance to the finals but had a lot of fun nonetheless. I am looking forward to gaining more Cribbage strategies so I can be a more competitive player for future matches.
First round of Cribbage tournament
Just for fun:
An adorable sole I caught on the fantail of the Rainer (I released him/her). 🙂
Fun factoid: A fathom which is a maritime measurement equal to 6 feet, was originally based on the distance, fingertip to fingertip of a man’s outstretched arms. Fathom that!
Mission: Walleye Pollock Survey Geographical Area of Cruise: Gulf of Alaska Date: July 22, 2013
Weather Data from the Bridge: (7/23/13 at 11 pm) Wind Speed = 13 knots
Air Temperature = 12.7 C
Humidity = 93%
Barometric Pressure = 1017 mb
Science and Technology Log:
There is a great deal of hope to complete the survey, which is supposed to end near Yakutat in the southeast of Alaska. It began near the islands of Four Mountains during leg 1. We are on leg 3, the final leg this summer. Leg 3 began in Kodiak. Three Legs of the Survey
Kodiak Island is the green marker and Yakutat Bay is the red.
The purpose of this cruise is to survey the walleye pollock (Theragra chalcogramma)in the Gulf of Alaska. Pollock is a significant fishery in the United States as well as the world. Pollock is processed into fish sticks, fish patties and imitation crab. Last year, about 3 million tons of pollock were caught in North Pacific. The scientists on board will collect data to determine the pollock biomass and age structure. These data are used with results from other independent surveys to establish the total allowable pollock catch.
Walleye Pollock from the Latest Trawl
According to the Alaska Fisheries Science Center, pollock can grow to about 3 ½ feet and weigh about 13 lbs. More typically the pollock are approximately 50 cm (20 in) and weigh .75 kg (1.7 lbs). They live in the water column and feed on krill, zooplankton and other crustaceans. As they age they will eat juvenile pollock and other small fishes such as capelin, eulachon and herring as well. Sexual maturity is reached around age 4. Spawning and fertilization occurs in the water column in early spring. The eggs stay in the water column and once hatched are part of the zooplankton until they are free swimming.
The general process used to catch the pollock involves multiple parts. I will break down those steps in a series of blogs. But basically, acoustics are used to locate fish in the water column. Once the scientists have located the fish along the transect (transects are the paths that the ship will travel on so the scientists can collect data), the Oscar Dyson sets out a trawl equipped with a camera. The trawl is brought in and data from the catch is documented. And then the ship continues on.
Trawling Nets on the Oscar DysonFish Lab on the Oscar Dyson
Trawling is usually completed only during daylight hours. Fortunately the sun does not set here in Alaska right now until after 10 pm. When it is dark, work aboard the Oscar Dyson continues. Jodi is documenting the sea floor with a drop camera. She is looking at life that is there as well as potential threats to the trawl nets for the bottom trawl surveys.
Questions:
How do scientists use acoustics to locate pollock?
How are the transects locations determined?
How are pollock and the rest of the catch processed?
What information is retrieved from the trawl camera?
What is a bottom trawl and how is it different from a mid-water trawl?
Personal Log:
We left Kodiak at 1 pm on July 22 heading southwest.
Goodbye Kodiak Island
We had 8 hours of travel time before we would reach our first transect. But before we got too far away from Kodiak, we needed to practice the three drills for the safety of everyone. The fire drill and man overboard drill required me to report to the conference room and meet up with the rest of the science team. Patrick, the lead scientist, then reported that we were all accounted for. The crew had more complex tasks of deploying a small boat and retrieving “the man overboard”.
The other drill was the abandon ship drill. We are assigned to a lifeboat and I reported to my muster on the portside of the trawl deck with my survival suit, long sleeve shirt, hat and life preserver. We will have drills weekly at anytime.
For the last two days I have been becoming oriented to the ship and to my responsibilities to the science team. Jodi, a post doctorate from Juneau gave us a tour of the boat on the first day we arrived in Kodiak. I then practiced finding all of the key parts of the ship I will need to access. I now am confident that I can find my stateroom, the mess, laundry room, both exercise spaces, acoustics lab, and fish lab. For other sites, I wander around for a while until I locate it.
Many doors on the the Oscar Dyson are water tight. They must be latched after passing through them.
My first shift began at 4 pm on Monday. There are two shifts for scientists. Some work 4 am to 4 pm and the others work 4 pm to 4 am. I work the night shift. I never drink coffee but today I realized that I needed it. My shift includes scientists Paul, Jodi and Darin as well as a survey tech named Vince. We all share staterooms with people who work the opposite shift.
The night shift science team includes Paul, Darin and Jodi (left to right). They monitor the fish in the acoustics lab also known as “The Cave”.
The ocean is very calm but most of us took Bonine (a seasickness medication) anyway to acclimate to the movement. Hopefully we will be adjusted to the motion before the seas get very rough if it does. The rocking of the boat does make one very sleepy.
The sea have been very calm for us.
Did You Know?
The requirements for joining the NOAA Corps include a bachelor’s degree in science, math or engineering and a 5 month program at the US Coast Guard Academy in New London, CT. This is Abby’s second cruise with the NOAA Corps. She has a bachelor’s degree in chemistry and just completed her NOAA officer basictraining.
Something to Think About:
What is a day in the life aboard the Oscar Dyson like?
NOAA Teacher at Sea Avery Marvin Aboard NOAA Ship Rainier (Ship Tracker) July 8-25, 2013
Mission: Hydrographic Survey Geographical Area of Cruise: Shumagin Islands, Alaska Date: July 19, 2013
Current Location: 54° 49.684 N, 159° 46.604 W
Weather Data from the Bridge: Foggy and overcast, wind 21 knots, air temperature: 11.5° C
Science and Technology Log:
As the fog horn sounds every two minutes and we sail solitary through the ocean, we are now in full swing surveying the Shumagin Islands, between and around Nagai, Bird, and Chernabura Islands. Unlike the old-time surveyors who used lead lines (lead weight attached to a long string), we are using a multibeam sonar system, which enables us to gather a large quantity of very accurate data in a more efficient and timely fashion.
Processed sonar data showing 3D image of the sea floor.
Sonar, (SOund Navigation And Ranging)uses the principle of sound wave reflection to detect objects in the water. Just as our eyes see the reflection of visible light off of the objects around us to create a visual image, when a sound wave hits something, it reflects off that “thing” and returns to its starting point (the receiver). We can measure the time it takes for a pulse to travel from the Sonar device below the boat to the ocean floor and then back to the receiver on the boat. Using a simple distance=speed * time equation, we can get the water depth at the spot where each beam is reflected.
The skiff that we use for the shoreline activities discussed in the last post has a single-beam sonar system that directs a pulse straight down beneath the hull to get a rough depth estimate. However, for our hydrographic work on the ship and launches, we use a multibeam system that sends 512 sound pulses simultaneously towards the sea floor over a 120° angle. When many sound waves or “beams” are emitted at the same time (called a pulse) in a fan like pattern (called a swath), the reflected information creates a “sound picture” of the objects or surface within that swath range. The actual width of this swath varies with the depth, but with 512 beams per pulse, and sending out between 5-30 pulses every second, we acquire a lot of data. If you piece together many swaths worth of data you get a continuous topographical or physical map of the ocean floor, and thus the depth of the water. For more information about the specific sonar system used aboard the Rainier and its launches, check out the ship page or the NOAA page about their hydrography work.
Graphic showing an example of the multibeam swath below a launch. Notice how the swath gets wider as the depth increases.Cross section of sea floor data showing dot or “ping” for each multibeam measurement. Notice how many individual measurements are represented in this one section.Cross section of sea floor data. Each color represents data from one swath. Notice the overlap between swaths as well as the width for each one.Processed sonar data showing 3D image of the sea floor.
In order to understand the complexities of sonar, it is important to understand the properties of sound. Sound is a pressure wave that travels when molecules collide with each other. We know that sound can travel in air, because we experience this every day when we talk to each other, but it can also travel in liquids and solids (which whales rely on to communicate). As a general rule, sound travels much faster in liquids and solids than in air because the molecules in liquids and solids are closer together and therefore collide more often, passing on the vibration at a faster rate. (The average speed of sound in air is about 343 meters every second, whereas the approximate speed of sound in water we have been measuring is around 1475 meters every second). Within a non-uniform liquid, like saltwater, the speed of sound varies depending on the various properties of the saltwater at the survey site. These properties include water temperature, dissolved impurities (i.e. salts, measured by salinity), and pressure. An increase in any of these properties leads to an increase in the speed of sound, and since we’re using the equation distance = speed * time equation, it is crucial to consistently measure them when seeking depth measurements.
Data from CTD showing temperature vs. sound speed from one data set. Notice how the temperature and sound speed seem correlated.
To measure these properties, a device called a CTD (Conductivity-Temperature-Depth) is used. Conductivity in this acronym refers to the free flowing ions in salt water (Na and Cl, for example), which are conductive and the concentration of these ions determines the salinity of the water. The CTD measures these three properties (Conductivity, Temperature and Depth) so the speed of sound in the water can be calculated at every point in the water column
To use the CTD, lovely humans like Avery and I will drop it into the water (it is attached to a winch system) at the area where we are surveying and as it travels to the sea floor, it takes a profile of the three saltwater properties mentioned before. Back in the computer lab, software takes this profile data and calculates the sound velocity or speed of sound through the water in that region. As a crosscheck, we compare our profile data and sound velocity figures obtained at the site to historical measured limits for each property. If our measurements fall significantly outside of these historical values, we might try casting again or switch to a different CTD. However, because we are surveying in such a remote area, in some cases, data outside historical limits is acceptable.
Graph of our sound speed vs. depth data showing comparison to historical data.
Given that we are trying to determine the water depth to within centimeters, variations in the sound speed profile can cause substantial enough errors that we try to take a “cast” or CTD reading in each small area that we are gathering data. The software the survey team uses is able to correct automatically for the sound velocity variations by using the data from the CTD. This means that the depth profile created by the sonar systems is adjusted based on the actual sound velocities (from the CTD data) rather than the surface sound speed. We are also able to account for speed changes that would cause refraction, or a bending of the beam as it travels, which would otherwise provide inaccurate data about the location of the sea floor.
Avery lowers the CTD into the water for a “cast”. The CTD needs to sit in the water for a few minutes to acclimate before being lowered for a profile.Avery successfully hauls in the CTD out of the water.
Personal Log:
You can’t go to Alaska without fishing its waters, rich with a variety of delectable fish species. So I decided to get my Alaskan recreation fishing license and try my hand at it on the fantail (stern) of the Rainier, while we were anchored in Bird Island cove. Carl VerPlanck, an experienced fisherman with arms like Arnold Schwarzenegger, had coached me on the best jigging techniques for catching a halibut and with my eyes (and mind) on the prize I followed his instructions diligently. It paid off as I landed several fish my first night on the fantail, with one halibut being a true keeper. John Kidd, NOAA Corps. Officer, gaffed my meaty fish over the steep rail of the Rainier and hauled it aboard. He was impressed with my catch (and hidden fishing talent), stating “This is the biggest fish caught so far this season.” Woohoo! Most impressive was the amount of meat the fish yielded (4 large filets) which I proudly donated to the kitchen and John. (Three big filets to the kitchen and one filet to John for his camaraderie, the use of his high-tech rod set-up and filleting skills). The following night, we all ate delicious baked Pacific Halibut filets, coated in a creamy Caesar glaze, prepared by chef-extraordinaire, Kathy. It’s pretty cool that I got to feed the ship!!
Avery’s meaty catch, a Pacific Halibut.John Kidd (NOAA Corps. Officer) filleting my halibutLook at all that meat!4 large fillets from the halibut
This was my first time catching a halibut and after close examination (and dissection) of this large, rather bizarre looking flatfish I became very intrigued and had several questions: How and why do the eyes migrate to one side? How do you tell the age of a halibut? What does the word “halibut” mean?
Like any good scientist, I proceeded to find the answers to these questions, and in doing so, learned many more interesting tidbits about Halibut. (The other species of halibut is the Atlantic Halibut which is very similar to the Pacific Halibut and is named as such for the ocean it occupies.)
So lets start with the name “halibut.” It’s origin is Latin (hali=haly=holy, but=butt=flat fish) and literally translates to “holy flat fish” because it was popular on Catholic holy days. Now what’s with the eye migration and why are both eyes on the same side? Well to understand this question thoroughly we must look at the conditions under which the halibut is born. Female halibut are sexually mature at age 12, spawning from November to March in deep water (300-1500 feet). Depending on their size, females release several thousand to several million eggs which are fertilized externally by the males. After the eggs are fertilized by the males, they become buoyant and start to float up the water column, hatching into free floating larva at about 16 days. As the larva mature, they continue to rise to the surface. At this larval stage they are upright, like any other “regular” fish, with one eye on each side of their head. This eye placement makes sense, considering they are in the open ocean with water on all sides of them. When at or near the surface, the larvae drift towards shore by ocean currents. As they get closer to shore and at about 1 inch in length, they undergo a very unique metamorphosis in which the left eye moves over the snout to the right side of the head. At the same time their left side fades in color eventually becoming white and their right side becomes a mottled olive-brown color. By 6 months, they are ready to settle to the bottom in near shore areas, hiding under the silt and sand, with just eyes exposed. Their mottled side will be face up, blending into their surrounds and their white side will face down, creating a “countershading” coloration, which helps keep them hidden from predators.
Halibut development: from halibut larvae to adult halibut. Notice the migration of the left eye to the right side and the pigmentation at the last stage.
The Pacific Halibut I caught was by no means a monster or “barn door” as the huge ones are called. But it also was not a “chicken”, slang for a small halibut. Female halibut can reach lengths of 8 feet and a weight of 500+ pounds. Males rarely exceed 100 pounds. Halibut are generally not picky eaters and will pretty much eat anything that lives in the ocean. Carl joked that a halibut would even eat an old shoe dangling from a fishing pole.
I was surprised to learn that halibut can live as long as 55 years. Scientists can accurately age a halibut by counting the rings in their ear bone or “otolith”, similar to dating a tree using its annual growth rings. So next time you catch a halibut and plan on keeping it, try to find the ear bone, grab a microscope and age the fish. If that fails, don’t forget to cut the cheeks out of the halibut (along with the 4 regular meaty fillets), for I am told that is the best part to eat. 🙂
Halibut otolith or ear bone that can be used to age the fish by counting the rings on the otolith (under a microscope).
Fun factoid: Sonar works a lot like the echo sounding of a bat, and its development was partially prompted by the Titanic disaster.
NOAA Teacher at Sea Chris Peters Onboard NOAA Ship Oregon II July 10 – 19, 2013
Mission: SEAMAP Summer Groundfish Survey Geographic Area of Cruise: Gulf of Mexico, leaving from Pascagoula, MS Date: July 3, 2013
Welcome to my NOAA blog!
A little about my background…
Christine Peters
I am Christina (Chris) Peters, from Farmland Elementary School in Rockville, Maryland. I have been a fourth grade teacher at Farmland for the past eight years, after trying out some other careers. While my past teaching has included all subjects, I am excited to get to focus more on science this coming year as my team will be departmentalizing and I will be teaching two classes of science. We spend half the school year learning about life sciences and the environment.
I grew up only a few miles from where I teach today, and was the third of ten children in my family. My father loved to fish and used to take us fishing, in turns of course, in his seventeen foot motor boat. Most often we fished in the Atlantic Ocean, off the coast of New Jersey, where my family frequently visited. We also fished in the Chesapeake Bay on occasion. One of my favorite summer meals was fresh bluefish. These experiences taught me to love the water, and to care about protecting that environment.
My father and I after a fishing trip. I was about ten, the same age as many of my students.
In addition to learning about and participating in the SEAMAP Summer Groundfish Survey, I will be learning something else completely new to me – how to blog! While I consider myself pretty technologically informed, I am new to blogging and am very excited, and a little nervous, about writing my own blog describing my Teacher at Sea experience.
Our mission on Oregon II
I will be flying to Mississippi next week and will be joining the crew of Oregon II on July 10 to participate in the SEAMAP Summer Groundfish Survey. To see pictures of the Oregon II, and to learn more about the ship, you can visit the website that describes details of the ship, as well as the different past and present projects for which Oregon II has been used. We will be departing from Pascagoula, Mississippi and measuring data on groundfish in the Gulf of Mexico. The Southeast Area Monitoring and Assessment Program (SEAMAP) is a state/federal program designed to collect, manage and disseminate fishery-independent data in the southeastern U.S. I am excited to learn more about how the scientists and crew actually complete the surveys and record data. One of my goals is to pass along what I learn to everyone who reads my blog.
Furthermore, while the Groundfish Survey is the mission of the scientists and crew onboard Oregon II, I will have an additional goal of learning all about the jobs of the crew, and sharing much of that information with the readers of my blog. Hopefully, when you read about these exciting and important careers, many of you will consider the possibility of pursuing one similar to those described.
To all my upcoming fourth grade students, I am looking forward to adapting the data collection tools I learn about to our science activities in the coming year. I hope my past students will visit my blog and think about connections they can make to our fourth grade science units where we created and observed our own model ecosystems.
