Pollock – Page 10 – NOAA Teacher at Sea Blog

July 28, 2013August 20, 2021

Melissa George: Do You Hear What I Hear? July 28, 2013

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: Sunday, July 28, 2013

Current Data From Today’s Cruise

Weather Data from the Bridge
Sky Condition: Cloudy
Temperature: 14° C
Wind Speed: 4 knots
Barometric Pressure: 1025.1 mb
Humidity: 90%

Sun and Moon Data
Sunrise: 5:57 am
Sunset: 10:34 pm

Moonrise: 11:52 pm (July 27, 2013)
Moonset: 2:35 pm

Geographic Coordinates at

Latitude: 59° 53.3′ N
Longitude: 149° 00.0′ W

The ship’s position now can be found by clicking: Oscar Dyson’s Geographical Position

False Point on Kenai Peninsula (viewed this morning through the fog)

Science and Technology Log

How do scientists use acoustics to locate Pollock (and serendipitously other ocean creatures)?

Scientists aboard the NOAA Research Vessel Oscar Dyson use acoustic, specifically hydroacoustic data, to locate schools of fish before trawling. The trawl data provide a sample from each school and allow the NOAA scientists to take a closer look by age, gender and species distribution. Basically, the trawl data verify and validate the acoustics data. The acoustics data, collected in the Gulf of Alaska in systematic paths called transects, combined with the validating biological data from the numerous individual trawls, give scientists a very good estimate for the entire Walleye pollock population in this location.

This screen is showing the echogram from the EK 60 echosounder during a trawl at 83.13 meters. The red line in the middle of the screen is the ocean floor. The colorful spikes above the red line indicate “backscatter” that is characteristic of capelin, a small fish that pollock feed on.

Hydroacoustics (from Greek words: hydro meaning “water” and acoustics meaning “sound”) is the study of sound in water. Sound is a form of energy that travels in pressure waves. In water, sound can travel great distances without losing strength and can travel fast, roughly 4.3 times faster in water than in air (depending on temperature and salinity of the water).

Click on this picture to see how sound travels from various ocean creatures through water. (Photo from sciencelearn.org)

The Oscar Dyson has powerful, extremely sensitive, carefully calibrated, scientific acoustic instruments or “fish finders” including the five SIMRAD EK60 transducers located on the bottom of the centerboard, the SIMRAD ME70 multibeam transducer located on the hull, and a pair of SIMRAD ITI transducers on the trailing edge of the centerboard.

Image of acoustic instruments on the Oscar Dyson. (Photo courtesy of NOAA Teacher at Sea Program)

This “fish-finder” technology works when transducers emit a sound wave at a particular frequency and detect the sound wave bouncing back (the echo) at the same frequency. When the sound waves return from a school of fish, the strength of the returning echo helps determine how many fish are at that particular site.

The green ship’s transducer is sending out sound waves towards the fish. The waves bounce back echoes towards the ship that are received by the transducer. (Photo courtesy of Oracle Thinkquest)

Sound waves bounce or reflect off of fish and other creatures in the sea differently. Most fish reflect sound energy sent from the transducers because of their swim bladders, organs that fish use to stay buoyant in the water column. Since a swim bladder is filled with air, it reflects sound very well. When the sound energy goes from one medium to another, there is a stronger reflection of that sound energy. In most cases, the bigger the fish, the bigger the swim bladder; the bigger the swim bladder, the more sound is reflected and received by the transducer. The characteristic reflection of sound is called target strength and can be used to detect the size of the fish. This is why fish that have air-filled swim bladders show up nicely on hydroacoustic data, while fish that lack swim bladders (like sharks) or that have oil or wax filled swim bladders (like Orange Roughy), have weak signals.

The above picture shows the location of the swim bladder. (Photo courtesy of greatneck.k12.ny.us)

These reflections of sound (echoes) are sent to computers which display the information in echograms. The reflections showing up on the computer screen are called backscatter. The backscatter is how we determine how dense the fish are in a particular school. Scientists take the backscatter that we measure from the transducers and divide that by the target strength for an individual and that gives the number of individuals that must be there to produce that amount of backscatter. For example, a hundred fish produce 100x more echoes than a single fish. This information can be used to estimate the pollock population in the Gulf of Alaska.

The above picture shows a computer screen with dense red “backscatter” characteristic of large amount of fish. The yellow lines above and below the backscatter show the location of the trawl lines. — The above picture shows a computer screen with dense red “backscatter” characteristic of large amount of fish, most likely pollock. The yellow lines above and below the backscatter show the location of the trawl lines.

Personal Log:

Safety

Continuing with Maslow’s hierarchy of needs, I will continue up the pyramid (see below) and discuss some ways that the basic need of safety is met on the ship. The safety and security of all staff (as well as sea animals we encounter) are top priority on the Oscar Dyson. There are constant reminders of this priority during ship life.

: A Version of Maslow’s Hierarchy of Needs

Safety Drills

On the first day of our travel, before the Oscar Dyson was far from port at Kodiak, we had three drills. 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 (the scientist team) 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. On the ship, every person is assigned to a life boat (mine is Lifeboat 1). When the drill commenced, I reported to my muster, the portside of the trawl deck, with survival gear: jacket, hat, survival suit and life preserver. We will have drills weekly at anytime.

Safety Gear

When working in the lab, the scientists wear orange slickers, boots, and gloves, not only to keep clean, but to protect us from anything that might be dangerous (fish spines, jellyfish tentacles, and so on). When on deck, we must wear hardhats (to protect from falling objects from the crane or trawl) and life preservers like the rest of the crew.

Water Tight Doors

Watertight doors are special types of doors found on the ship which prevent the flow of water from one compartment to other during flooding or accidents. These doors are used onboard in areas, such as the engine room compartment, science and acoustics labs, and control bridge, where chances of flooding are high.

These are just a few examples of how safety is emphasized on the ship. There are reminders in one’s line of vision constantly.

Safety, Everyone's Responsibility — Safety, Everyone’s Responsibility

Did You Know?

There are various seafarer or crew positions on the Oscar Dyson. A ship’s crew can generally be divided into three main categories: the deck department, the engineering department, and the steward department. Rob and Greg are members of the deck department; both men hold Merchant Mariner Credentials as “Able Bodied Seamen” or ABS. Rob is from Boston, Massachusetts and went to school for seamanship in Fairhaven, MA. He considers his NOAA position as a good job with a good income, but his main profession is lobstering which he does on the open sea when he is not working for NOAA. Rob says, “The ocean is in my blood” and always wanted to work on it. Greg, on the other hand, chose to be a Merchant Mariner after a voyage at sea. He moved to Texas from Louisiana in his 20’s, went fishing for the first time, and got seasick. He considered battling seasickness a challenge, and thus pursing seamanship as a career. In his free time he is a free-lance photographer and journalist. Below are some pictures of Greg and Rob on the job. Notice they are always wearing their safety gear.

Greg and Rob Bringing in the Trawling Net

Greg and Rob, Preparing for a Camera Drop

Something to Think About:

Since I will begin teaching Zoology later in August, I have decided to highlight some of the animals that the scientist team has found in our trawls. Today’s feature will be one of the simplest multicellular animal families, the Porifera. Porifera is a word formed from combining the Latin words porus which means “passage-way” and fera meaning “bearing.” Porifera, commonly referred to as sponges, have tiny pores in their outer walls that filter water to get nutrients.

Various Porifera (Sponges) from a Bottom Trawl

Teacher (me) Demonstrating How Water Flows out the Osculum (opening) of a Poriferan

To learn more about the Porifera Family, click the Porifera on the picture below, and stay tuned for further exploration of this animal Tree of Life.

Tree of Life: Can you spot the Poriferan?

July 20, 2013August 20, 2021

Melissa George: Contemplating Kodiak, July 20, 2013

NOAA Teacher at Sea
Melissa George
Aboard NOAA Ship Oscar Dyson
July 22–August 9, 2013

Mission: Alaska Pollock Survey
Geographical Area of Cruise: Gulf of Alaska
Date: July 20, 2013

Introductory Blog

Greetings from Lafayette, Indiana, where I recently moved back after spending two years in Washington, D.C. as an Albert Einstein Distinguished Educator Fellow at the National Science Foundation in the Division of Environmental Biology. In my recent position, I learned of many of the interesting research projects that ecosystem ecologists, population and community ecologists, systematic biologists, and evolutionary biologists are working on in various parts of the world. Beginning this fall, I will be returning to the Lafayette School Corporation to teach Biology and Zoology at Jefferson High School in Lafayette, Indiana. I am excited to integrate aspects of the research I have learned about into my classroom.

Enhancing my understanding will be the authentic research experience in the Gulf of Alaska as a NOAA Teacher at Sea. I will fly to Kodiak Island and board NOAA Ship Oscar Dyson, a support platform to study and monitor various aspects of the ocean: environmental conditions, habitat assessments, and marine mammal, fish, and bird populations.

This particular mission will be surveying the population of a species of fish called Alaskan pollock or scientifically speaking, Theragra chalcogramma. These fish belong to the cod family and are one of the United States’ most valuable fisheries; they are typically sold as fish sticks, fish patties, or imitation crab, scallops, or shrimp. Pollock populations vary from year to year, thus fish surveys, help to enact management practices as well as monitor the effects of climate change.

This adventure is exciting to me for several reasons. First, growing up on the Pacific Coast in Santa Cruz, California I fell in love with the ocean at a young age. I realize the importance of respecting the ocean and the ecosystems within it and around it. Having spent the second half of my life in the Midwest, I have missed its calming effect as well as the wealth of ecological wonders it holds. I escape to the ocean whenever I have the chance. Below is a picture of me resting on the beach at Halawa Bay on the east end of Molokai, one of the Hawaiian Islands.

Second, I hope to incorporate what I learn about how ocean scientists monitor various animal populations into my high school classes. There are so many aspects to this endeavor, I think my students will be excited to learn about many, if not all, of them.

Fun Fact:

I have four traveling companions. They are in the photo below. One of them will be accompanying me on the Teacher at Sea mission. See if you can find pictures of this traveling companion in future posts and please comment when you do!

My Four Traveling Companions: Manny, Molly, Mini Me, and Bust of Einstein

July 12, 2013August 13, 2021

Amie Ell: Deadman’s Bay, July 11, 2013

NOAA Teacher at Sea
Amie Ell
Aboard NOAA Ship Oscar Dyson (NOAA Ship Tracker)
July 7 – July 11, 2013

Mission: Alaska Walleye Pollock Survey
Geographical Area: Gulf of Alaska
Date: July 11th, 2013

Location Data from the Bridge:
Latitude: 56.56 N
Longitude: 152.74 W
Ship speed: 11.3 kn

Weather Data from the Bridge:
Air temperature: 10.7 degrees Centigrade
Surface water temperature: 8.6 degrees Centigrade
Wind speed: 18 kn
Wind direction: 250 degrees
Barometric pressure: 1016 mb

Science and Technology Log:

OLYMPUS DIGITAL CAMERA — Full net on deck

So now that you know what we do with the fish after they are caught, let’s go back and see how the fishermen trawl. There are two large nets at the stern of the ship. Today we used both nets for the first time. The scientists, crew, and fishermen all work together to catch the fish. In the acoustics lab Paul is reviewing and scrutinizing the data he receives from the echo locators mounted on the hull of the ship. There are many factors he must evaluate in order to have a good trawl. There are places in our area that have been marked as “untrawlable”. This is usually due to a sea floor that is rocky. Trawling in these places may ruin the nets. We have completed at least one trawl a day since we have been out to sea. Today we completed two during my watch. The first was with a larger net and was not sent all the way to the bottom. The second trawl was sent to the bottom with a smaller net. The bottom trawl brought up the largest pollock I have seen so far. The longest pollock was 75 cm. We also brought up a salmon, cod, rock fish, and a whole lot of herring.

Crane lifting the net to be dumped into the bin.

The nets are both on large spools and are released or returned with the help of a very large winch. Before the net is released into the water the CamTrawl is attached to it. This is a camera that takes pictures that help the scientists see at what point in the trawl fish were entering the net.

Example photo from the CamTrawl. A Salmon Shark caught on the first leg.

The time that the net is in the water depends on the information about the amount of fish coming from the acoustics lab. Scientists watch the echo information to determine how much time the net should be in the water to catch enough fish to sample. We must have at least 300 pollock to make a complete survey.

The fishermen bring the nets back to the trawl deck and wind them back onto the spools. They then will use a crane to lift the catch and dump it into a bin. From the fish lab we can lift this bin to dump the fish onto the conveyor belt.

Personal Log

Entering Deadman's Bay — Entering Deadman’s Bay

On Monday, we had our weekly fire and abandon ship drills. After the drills I practiced putting on my survival suit. This suit is designed to keep you afloat and warm in the event that you have to go into the water.

On Tuesday, we surveyed up into Deadman’s Bay. It was a beautiful sun shiny day and the scenery was amazing. We were very close to the shore on both sides. I sat out on the trawl deck and scanned the hillsides with my binoculars. I was told that it is common to see bears here, but I did not see any.

June 13, 2013August 11, 2021

Marla Crouch: Checking Out the Fish! June 12, 2012

NOAA Teacher at Sea
Marla Crouch
Aboard NOAA Ship Oscar Dyson
June 8-26, 2013

Mission: Pollock Survey
Geographical area of cruise: Gulf of Alaska
Date: June 12, 2013

Weather Data from the Bridge: as of 2300
Wind Speed 12.30 kts
Air Temperature 6.10°C
Relative Humidity 98.00%
Barometric Pressure 1,009.6mb

Latitude: 54.22N Longitude: 164.65W

Science and Technology Log

Here I am all decked out in my rain gear in the wet lab, ready to sort the catch of our first bottom trawl. Quite a fashion statement, don’t you think?

Walleye Pollock (latin name Theragra chalcogramma), a fish that lives both on and above the seafloor, is the main target of the Pollock survey, but information about other sea life is also collected. When we start sorting the catch from this bottom trawl, the primary population is Pacific Ocean Perch (POP, Sebastes alutus). The POP is a member of the Scorpaenidae or scorpionfish family and has poisonous spines. When handling the fish I have to be really careful of the very sharp spines to avoid injury. Fortunately, the POP’s teeth are not as formidable as their spines, so I can grab them by the mouth to safely move them around.

Every point on the dorsal fin (top fin) is a poisonous spine. Graphic courtesy of http://akfishinfo.alaskaseafood.org/main/pages/white-rockfish

After we sort the catch the total weight of each species is recorded. We collect additional biological data on the POP, by first sorting them by “Blokes” or “Sheilas.” I’ll let you figure out what characterizes Blokes and Sheilas. After the sorting, each fish in the sample is laid on an electronic measuring board (mm) to determine and record the length of the fish. In this survey the length of the fish is measured from the tip of the mouth to the center of the “v” in the tail, this is know as the fork length.

Other populations being sampled are plankton and the jellyfish that were collected in a Methot trawl. Here Abigail McCarthy is sorting two types of zooplankton krill (also called euphausiids) and jellyfish that were collected. Once the sorting is completed, then the quantity and weight of the krill and the jellyfish is recorded. One of the areas Abby is investigating is if there is a correlation between the krill population and the location of baleen feeding whales. Abby wonders how far away the whales can smell or sense dinner? Who can tell me which species of whales are baleen feeders?

Another tool the scientists use to collect data is a tethered stereo camera that takes 10 pictures/second. Using the pictures I am counting and sorting fish by species. Look at the pictures and you’ll see a Gorgonia sea fan and a basket star. The camera has a stationary photo length, so objects closer to the camera appear bigger. In the picture with the sea fan, you are also seeing krill. You can use the pairs of images from the stereo cameras to measure the size of the organisms that appear in the images.

The two cylinders in the center are the cameras and the four other cylinders are strobe lights.

The sea fan is a member of the soft coral family. Krill can be seen in front of the sea fan. Picture provided by NOAA.

The basket star is a type of sea star. Here the basket star is open waiting for dinner to drift by. — The basket star is a type of sea star. Here the basket star is perched on top of a sea sponge open waiting for dinner to drift by. Picture provided by NOAA

Personal Log

When the Oscar Dyson sailed from Dutch Harbor we head west to the Islands of Four Mountains, a cluster of volcanic isles. On one isles is Mt. Cleveland, which on May 5^th was actively spewing lava. As we pass, Mt. Cleveland is quietly shrouded in dense cloud cover. Darn, cannot check eruption off my “Want to see” list. I don’t think I’ll see an aurora either as the cloud cover has been thick.

This is the south side of Onalaska. Dutch Harbor is on north side facing the Bering Sea. — This is the south side of Unalaska. Dutch Harbor is on north side facing the Bering Sea.

Science aboard the Oscar Dyson runs 24/7. Both the Dyson’s crew and the science team work in twelve hour shifts. For the Dyson’s crew the day is broken into two shifts, from midnight to noon and noon to midnight. The science team shifts are from 4 a.m. (0400 hrs.) to 4 p.m. (1600 hrs.) and 1600 hrs. to 0400 hrs. I am on the 1600hrs to 0400hrs shift; morning and night run all together. A note here, when the scientists collect data the time stamp is Greenwich Mean Time (GMT). GMT is eight hours ahead of us here in Alaska.

Did You Know?

I’ve discovered that you can slosh in your berth. Check out the next blog for “Surf Your Berth.”

August 11, 2012August 11, 2021

Allan Phipps: Looking Ahead: The Future of NOAA Fish Surveys? August 10, 2012

NOAA Teacher at Sea
Allan Phipps
Aboard NOAA Ship Oscar Dyson
July 23 – August 11, 2012


Mission: Alaskan Pollock Mid-water Acoustic Survey
Geographical Area: Bering Sea
Date: August 10, 2012
.

Location Data
Latitude: 53°54’41” N
Longitude: 166°30’61” E
Ship speed: 0 knots (0 mph) In Captains Bay at Dutch Harbor during calibration.

Weather Data from the Bridge
Wind Speed: 17 knots (19.5 mph)
Wind Direction: 184°
Wave Height: 1-2 ft
Surface Water Temperature: 10.2°C (50.4°F)
Air Temperature: 12.5°C (54.5°F)
Barometric Pressure: 1005.9 millibars (0.99 atm)

Science and Technology Log:

Imagine a time when fish surveys could be done through remote sensing, thus eliminating the need to catch fish via trawling to verify fish school composition, length, weight, and age data. During our “Leg 3” of the Alaska Pollock Acoustic Midwater Trawl Survey, we caught, sorted, sexed, and measured 25 tons of pollock! While this amounts to only 0.002% of the entire pollock quota and 0.00025% of the pollock population, wouldn’t it be nice if we could determine the pollock population without killing as many fish?

Introducing the “Cam-Trawl,” a camera-in-net technology that NOAA scientists Kresimir and Rick are developing to eventually reduce, if not eliminate, the need to collect biological specimens to verify acoustic data. Cam-Trawl consists of a pair of calibrated cameras slightly offset so the result is a stereo-camera.

The importance of setting up a stereo-camera is so you can use the slightly different pictures taken at the same time from each camera to calculate length of the fish in the pictures. Eventually, a computer system might use complex algorithms to count and measure length of the fish that pass by the camera. If the kinks are worked out, the trawl net would be deployed with the codend open, allowing fish to enter the net and flow past the camera to have their picture taken before swimming out of the open end of the net. Some trawls would still require keeping the codend closed to determine gender ratios and weights for extrapolation calculations; however, the use of Cam-Trawl would significantly reduce the amount of pollock that see the fish lab of the Oscar Dyson. On this leg of the survey, the NOAA scientists installed the Cam-Trawl in a couple of different locations along the trawl net to determine where it might work best.

Below are some photos taken by Cam-Trawl of fish inside the AWT trawl net. Remember, there are two cameras installed as a stereo-camera that create two images that are taken at slightly different angles. In the photos below, I only picked one of the two images to show. In the video that follows, you can see how scientists use BOTH photos to calculate the lengths of the fish captured on camera.

pollock — Pollock (Theregra chalcogramma) as seen by Cam-Trawl.

salmonherringjelly — A Sea Nettle (Chrysaora melanaster) jellyfish at top right, Chum Salmon (Oncorhynchus keta ) at bottom right, and Pacific Herring (Clupea harengus) on the left as seen by Cam-Trawl installed in the AWT trawl net.

Another NOAA innovation using stereo cameras is called “Trigger-Cam.” Trigger-Cam is installed into a crab pot to allow it to sit on the ocean floor. For this type of camera deployment, the NOAA scientists removed the crab pot net so they would not catch anything except pictures.

The real innovation in the Trigger-Cam is the ability to only take pictures when fish are present. Deep-water fish, in general, do not see red light. The Trigger-Cam leverages this by using a red LED to check for the presence of fish. If the fish come close enough, white LEDs are used as the flash to capture the image by the cameras.

The beauty of this system is that it uses existing fishing gear that crab fishermen are familiar with, so it will be easily deployable. Another stroke of brilliance is that the entire device will cost less than $3,000. This includes the two cameras, lights, onboard computer, nickel-metal hydride batteries, and a pressure housing capable of withstanding pressures of up to 50 atmospheres (500 meters) as tested on the Oscar Dyson! Here is a short animated PowerPoint that explains how Trigger-Cam works. Enjoy!

Here are a couple of picture captured by the Trigger-Cam during trials!

TriggerCampics — Two pictures taken from Trigger-Cam during testing.

While these pictures were captured during tests in Dutch Harbor, they do provide proof-of-concept in this design. With a cheap, easily deployable and retrievable stereo-camera system that utilized fishing gear familiar to most deck hands, Trigger-Cams might contribute to NOAA’s future technology to passively survey fish populations.

three stooges — NOAA scientists Kresimir Williams (in center), Rick Towler (on right), and me, after assembling and testing another stereo-camera system for a NOAA scientist working on the next cruise. Kresimir and Rick designed and built Trigger-Cam!

Personal Log:

A little fun at sea! We needed to do one last CTD (Conductivity, Temperature, Depth), and decided to lower the CTD over deep water down to 500 meters (1,640.42 ft)! Pressures increases 1 atmosphere for every 10 meters in depth. At 500 meters, the pressure is at 50 atmospheres!!! We wondered what would happen if… we took styrofoam cups down to that depth. We all decorated our cups and put them in a net mesh bag before they took the plunge. Here is a picture showing what 50 atmospheres of pressure will do to a styrofoam cup!

We missed the Summer Olympics while out on the Bering Sea. T-T We did get in the Olympic spirit and had a race or two. Here is a little video in the spirit of the Olympics…

All for now… We are back in Captains Bay, Dutch Harbor, but are calibrating the hydroacoustic equipment at anchor. Calibration involves suspending a solid copper sphere below the ship while the NOAA scientists check and fine-tune the different transducers. This process will take about 7 hours! We have been out at sea for 3 weeks, are currently surrounded by land, but must wait patiently to finish this last and very important scientific task. If the calibration is off, it could skew the data and result in an inaccurate population estimation and quotas that may not be sustainable! This Landlubber can’t wait to have his feet back on terra firma. The thought of swimming crossed my mind, but I think I’ll wait. Then we will see if I get Land Sickness from being out at sea for so long…