Whale – NOAA Teacher at Sea Blog

July 10, 2023July 19, 2023

Lisa Carlson: One Fish, Two Fish, Rockfish, Hake fish! July 10, 2023

NOAA Teacher at Sea

Lisa Carlson

NOAA Ship Bell M. Shimada

July 5, 2023 – July 19, 2023

Mission: Fisheries: Pacific Hake Survey (More info here)

Geographic Region: Pacific Ocean, off the coast of California

Date: July 10, 2023

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Weather Data from the bridge:

July 7 (1200 PT, 1500 EST)
Location: 36° 00.4’ N, 122° 05.9’ W
16nm (21mi) West of Big Sur, CA

Visibility: 10 nautical miles
Sky condition: Overcast
Wind: 20 knots from NW 330°
Barometer: 1013.1 mbar
Sea wave height: 3-4 feet
Swell: 6-7 ft from NW 320°
Sea temperature: 14.0°C (57.2°F)
Air temperature: 14.4°C (57.9°F)
Course Over Ground: (COG): 323°
Speed Over Ground (SOG): 10 knots

July 8 (1200 PT, 1500 EST)
Location: 36° 34.5’ N, 122° 05.3’ W
17nm (20mi) Southwest of Monterey, CA

Visibility: 10 nautical miles
Sky condition: Few clouds
Wind: 19 knots from NW 330°
Barometer: 1013.8 mbar
Sea wave height: 5-6 feet
Swell: 6-7 ft from NW 330°
Sea temperature: 14.0°C (57.2°F) 13.7
Air temperature: 14.4°C (57.9°F) 14.3
Course Over Ground: (COG): 089°
Speed Over Ground (SOG): 10 knots

July 9 (1200 PT, 1500 EST)
Location: 37° 06.8’ N, 123° 00.5’ W
30nm (35mi) West of Pigeon Point Light Station, Pescadero, CA

Visibility: 10 nautical miles
Sky condition: Overcast
Wind: 13 knots from NW 332°
Barometer: 1016.0 mbar
Sea wave height: 2-3 feet
Swell: 4-5 ft from NW 310° 4-5
Sea temperature: 14.3°C (57.7°F)
Air temperature: 15.2°C (59.4°F)
Course Over Ground: (COG): 093°
Speed Over Ground (SOG): 10 knots

July 10 (1200 PT, 1500 EST)
Location: 37° 26.7’ N, 123° 06.4’ W
32nm (37mi) West of Pescadero, CA

Visibility: 8 nautical miles
Sky condition: Overcast, fog in vicinity
Wind: 20 knots from NW 330°
Barometer: 1015.9 mbar
Sea wave height: 2-3 feet
Swell: 3-4 ft from NW 320°
Sea temperature: 14.5°C (58.1°F)
Air temperature: 13.6°C (56.5°F)
Course Over Ground: (COG): 314°
Speed Over Ground (SOG): 3 knots

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Science and Technology Log

Lisa poses for a photo in the wet lab with a hake fish. She's wearing heavy-duty orange overalls and large orange gloves. With her right hand, she grasps the fish by its open mouth, and her left hand holds on to the tail. We can see metal tables and equipment in the background. — Me holding a Hake before sorting. After observation, we determined this was a developmentally mature female, measuring 50cm (20in) long!

In my July 6 blog post, I explained how NOAA Ship Bell M. Shimada is equipped to collect acoustic data in the form of echo grams. The acoustics team uses the data to determine if there are enough return signals to suggest fish are present and attempt a trawl. In this blog post, I will explain how we get the fish onboard, and what we do with the sample of marine life once it is collected from the net.

One question I had after learning about the acoustics and environmental DNA (eDNA) pieces of the survey mission was, “How does physically collecting and researching Hake samples fit into the puzzle of understanding their ecosystem and supporting sustainable fisheries?” (NOAA Fisheries quick facts and video here)

“While echosounders are useful, they do not provide certain quantitative data that researchers need to understand the ecology of these organisms and the midwater zone. To collect quantitative data, such as biomass, length and weight, and age class distributions, researchers must gather representational samples and take direct measurements of them. The best way to do this is by employing trawls.”
NOAA Ocean Exploration: “Trawls”

So, although acoustics and eDNA research is important to the overall survey, they are only pieces of the puzzle, and the puzzle is not complete without conducting trawls and physically researching samples. NOAA Ship Bell M. Shimada uses a midwater trawl net that is deployed from the stern over the transom, and towed behind the vessel. As the name suggests, midwater trawls occur in the middle section of the water column, versus surface and bottom trawls. The net is conical in shape and uses two metal Fishbuster Trawl Doors, and two sets of heavy chain links called Tom weights, in order to keep the trawl in the middle of the water column.

a simple and stylized monochrome illustration of a fishing vessel towing a midwater trawl behind it. The net in tow is conical, attached at four points to two bars that hold the opening apart, and these bars are attached to lines (ropes) extending back from the vessel. This net is capturing two fish and missing a third. — NOAA Fisheries: “Fishing Gear: Midwater Trawls”

“The midwater region is especially important because the creatures that inhabit it constitute the majority of the world’s seafood. Understanding the ecology of midwater organisms and their vast environment can provide us with better information to manage these important natural resources and prevent their overexploitation.”
NOAA Ocean Exploration: “Trawls”

Deck department assisting in recovering the trawl net after a successful deployment.

Two deck crewmembers work with an orange and white fishing net on the aft deck of NOAA Ship Bell M. Shimada. They are wearing foul weather gear, life vests, and hard hats. At right, one leans over the net, searching for remaining captured fish. The other approaches from the left, looking down at the net, to assist. We can see a cloud-capped mountain range in the distance beyond the water.

Once the net is onboard, the net is emptied one of two ways depending on the size of the sample. For large samples, marine life is deposited into a hopper and subsequent conveyor belt. For smaller samples, the Hake will be put into a large basket then divided into smaller baskets of approximately 100 Hake each. Any other marine life like Salps, Myctophids, Pyrosomes, Rockfish, King of the Salmon, and small bony fish, etc. are recorded in the database and returned to the ocean.

“The ship’s wet lab allows scientists to sort, weigh, measure and examine fish. The data is entered directly into the ship’s scientific computer network.”
NOAA Office of Marine and Aviation Operations (OMAO): “Bell M. Shimada”

a large black plastic bin filled with fish - mostly hake, but a few splitnose rockfish (eyes bulging from the pressure change) stand out for their red color. An orange-gloved hand reaches toward the basket from the upper left corner of the image.

Large basket containing a sample of Hake with a few (red) Splitnose Rockfish.

a view of NOAA Ship Bell M. Shimada’s Wet Lab with multiple scales, Ichtystick electronic measuring boards, trawl camera, vials for otolith (ear) bones, disposal chute, and tools including scalpels, tweezers, and knives. — NOAA Ship *Bell M. Shimada’s* Wet Lab with multiple scales, Ichtystick electronic measuring boards, trawl camera, vials for otolith (ear) bones, disposal chute, and tools including scalpels, tweezers, and knives.

Maddie, in the wet lab, holds a hake fish up for a photo. She is wearing a long-sleeved shirt, heavy-duty orange overalls, and large orange gloves. Her hair is tied back in two double braids and topped with a teal bandana. She holds the fish in two hands, horizontally, at the level of her mouth, so we cannot see her smiling, but we can see her arch her eyebrows as she looks straight at the camera. — NOAA Ship *Bell M. Shimada’s* Wet Lab with multiple scales, Ichtystick electronic measuring boards, trawl camera, vials for otolith (ear) bones, disposal chute, and tools including scalpels, tweezers, and knives.

With our boots and bright orange rubber pants and gloves on, our first task is to distribute the sample of Hake into baskets of about 100 each. Based on how many baskets we fill, a random selection of baskets will be kept, and the others will be returned to the ocean. With the remaining groups of Hake, we determine their sex and length.

In order to do this, we use a scalpel to make an incision on the underside/belly of the Hake. Once open, we are able to examine their organs, including the gonads to determine if the fish is male or female, and if they are developmentally immature or mature. Young Hake are difficult to sex, and it takes practice to get over any initial fears of cutting into an animal; let alone being able to locate and identify the gonads. Hake usually spawn in early winter, so many of the smaller Hake we sample from during the summer are age one or younger.

Our largest Hake thus far was a developmentally mature female, measuring 50cm (20in). In order to accurately and consistently measure the length of the sample, we use a waterproof, magnetic plastic board with metric (centimeter and millimeter) markings called an Ichthystick (think: high-tech meter stick). The fish is placed on the board with its mouth touching the black board at 0cm, then a magnetic stylus is placed at the fork of the fish’s tail. Once the magnetic stylus is placed on the board, the length to the nearest millimeter is displayed on the LCD screen and automatically entered into the database program. The length data is grouped with the date, time, and identified sex for later observation and comparison.

Additional information, abstracts and outline about Ichthystick here

Ichthystick’s LCD display, motherboard, magnetic board, and magnetic stylus. Digital scale in background.

An even smaller subgroup is then selected and examined to record weights of individual Hake, collect ear bones called Otoliths for aging, stomach samples for diet, liver for RNA, and ovaries for maturity development. Otolith bones help determine the age of the Hake because they grow a new “layer” of bone each year, similar to coral structures and annual tree rings. Organs and bones removed from the Hake are sent to NOAA Fisheries centers for analysis and included in databases with the date, identified sex, length, weight, and location in which they were collected.

This data is used to build more of the puzzle, along with acoustical information, water samples, and eDNA data in order to further understand the ecosystem, biomass, diet, and

“support sustainable populations of Pacific hake on the West Coast.” (…)
“It provides vital data to help manage the migratory coastal stock of Pacific hake. The hake survey, officially called the Joint U.S.-Canada Integrated Ecosystem and Pacific Hake Acoustic Trawl Survey, occurs every odd-numbered year.”
NOAA Fisheries: “Joint U.S.-Canada Integrated Ecosystem and Pacific Hake Acoustic Trawl Survey”

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Personal Log

Although this subtopic of explaining the Integrated Ecosystem and Pacific Hake Acoustic Trawl Survey is a bit easier to understand than my July 6 Acoustics Lab post, it certainly does not mean it’s an easy task!

When I had a tour on July 4, I remarked how clean and organized the Wet Lab is. I hadn’t see it in action yet, but noticed how everything had its place and use. On July 6 we conducted our first trawl and collected a sample of 11 baskets of Hake (approximately 1,100 Hake since we group about 100 Hake together in each basket.) From that sample, we kept four baskets and counted, sexed, and measured 541 Hake.

Five of us were working together in the Wet Lab for that haul. I’ll admit I probably didn’t sex 100+ Hake. It took a few minutes of watching the others carefully and swiftly cut into the underside of a fish, open the two sides, and know what to look for to determine the sex of very young Hake. Eventually I found the courage to slice in and take a look. By the fourth or fifth Hake, the uneasiness had subsided and I found the process very interesting and educational. Although young samples are hard to sex as they are often undeveloped, the others encouraged me and answered my questions and guesses with enthusiasm and support.

While working on measuring the lengths of our samples, one Science Team member paused and remarked how beautiful he found the fish. Although they do not have vibrant, bold colors, shimmering scales, or anything else particularly remarkable, he found the beauty in them. He digressed into a conversation of their role in the ecosystem, how they are living and breathing creatures, and how they probably all have their own personalities and slight physical differences. I noticed some of their eyes were shiny and sparkling, and how their faces and expressions were noticeably unique the more you looked. That “down to earth”, heartfelt discussion was very special and demonstrated how the crew respects the process of catching and sampling Hake, while keeping each other and marine mammals safe.

From the NOAA Corps Officers, to the deck department, to the engineers, electronics, science team, survey team, galley crew, volunteers, and everyone in between; the crew on NOAA Ship Bell M. Shimada is special. They take pride in their vessel and job, and always seem to have a smile and kind greeting. Being away from land and loved ones for weeks and months at a time will certainly take a toll on the body and mind, but this team is there for each other. To all of the crew, thank you for making me feel so welcomed and appreciated. We’re almost halfway through the mission, and as tired as I may get after (sometimes) 12+ hour days, I sleep well knowing the crew trusts their vessel and each other; and look forward to learning and becoming more and more acquainted each day with the people that make this mission possible. Thank you!

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Did You Know? (FAQs)

1. Are you finding schools of them?

We’ve had seven successful trawls out of nine attempts for Pacific Hake fish. They often come with pyrosomes (Sea Pickle) myctophids (Lanternfish), and salps in the net too. Some trawl attempts are successful without a hitch, but more often than not we have to restart our Marine Mammal watches a few times before deploying in order to keep our ocean life safe and not get tangled in the net. Two trawl attempts have been abandoned because of the amount of persistent marine mammal life and playfulness near the ship. (I think they know we’re watching and show off for our cameras.)

2. What’s your average depth?

The transects (Set and numbered longitudinal east-west lines NOAA Ship Bell M. Shimada navigates on while collecting acoustic data) usually range from 50m – 1,500m (164ft – 4,921ft) in depth.

However, right now one of the displays in the Acoustics Lab, the depth reading is 3,240m which is about 10,630ft or just over two miles deep!
This depth is only 1,870ft shallower than the wreck of the RMS Titanic!
(We were on a long transect, we do not often see depths this great.)

3. Have you gotten seasick? Seasickness should subside after about 3 days.

I’ve never gotten seasick thankfully! Knock on wood and all the other premonitions, please.

4. What is the Hake role in the ecosystem?

More info on this coming in later posts after explaining our Chemistry lab and technology aboard!

However, as predators, they can be cannibalistic towards their own kind.
As far as their role in human consumption: They are often used as a substitute for Cod and Haddock, and in fish sticks and imitation crab meat.

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Animals seen July 5-July 10:

Mammals: Sea Lions, Harbor Seals, Dall’s Porpoise, Risso’s Dolphins, Pacific White-Sided Dolphins, Northern Right Whale Dolphins, Humpback Whales

Birds: Gulls, Black-Footed Albatross

Bony Fish: Hake, Lanternfish (Myctophid), Flatfish, King of the Salmon, Split Nose Rockfish, Chili Pepper Rockfish

Other Marine Life: Giant or Humboldt Squid (15 foot tentacles in trawl), Spiny Dogfish Shark, Shrimp, Plankton, Krill, Sea Pickle (Pyrosome), Salp, Eel Larva

a spiny dogfish - a species of small shark - placed on a fish measuring board atop a metal table. a scale is visible next to the measuring board. — Spiny Dogfish Shark (42cm or 16in long)

three impressively long squid tentacles laid out on the floor; they are orange-brown on top, and white underneath, lined with white suckers (suction cups) of varying size — Spiny Dogfish Shark (42cm or 16in long)

July 10, 2019July 13, 2019

Erica Marlaine: Happy Fourth of July from the 49th State, July 4, 2019

NOAA Teacher at Sea

Erica Marlaine

Aboard NOAA Ship Oscar Dyson

June 22 – July 15, 2019

Mission: Pollock Acoustic-Trawl Survey

Geographic Area of Cruise: Gulf of Alaska

Date: July 4-5, 2019

Weather Data from the Bridge:

Latitude: 55º 48.9 N
Longitude: 159º 2.3 W
Wind Speed: 4.2 knots
Wind Direction: 186.5º
Air Temperature: 14.7º Celsius
Barometric Pressure: 1022.12 mb
Depth of water column 84.5 m
Surface Sea Temperature: 10 º Celsius

History

On March 30, 1867, Secretary of State Seward purchased Alaska from the Russian Empire for 7.2 million dollars (or 2 cents per square mile). It was deemed a territory for many years until January 3, 1959 when President Eisenhower signed a proclamation admitting Alaska into the United States. The word “Alaska” comes from an Aleut-language idiom that means “object to which the action of the sea is directed.” It is the northernmost and westernmost state in the United States. It is also the largest state. By comparison, it is twice the size of Texas.

Celebrating the Fourth of July, NOAA style

My usual Fourth of July at home includes a bar-b-que, swimming, and attending a fireworks show at night. The Fourth of July celebration on the NOAA ship Oscar Dyson was completely different, and literally a BLAST. At noon, an announcement was made for “all hands” to report to the galley for Fourth of July “mocktails” or fun non-alcoholic drinks. (There is no alcohol on a NOAA ship.) I had a delicious “mimosa” made of orange juice and sparkling cider. Later, we were taken on a wonderful ride past Mitrofania Island.

Photographs do not do it justice. It was my first time up on the fly bridge (the “roof” of the boat) and I loved being able to take in the 360 degree views. Many people never get to see this part of Alaska as it is not a route commonly taken by cruise ships. The “fireworks” part came the next morning, when “all hands” were again called to the deck to light off expired flares. While some made a popping noise, the one I did produced thick orange smoke for at least 30 seconds. It was, as I said, a literal blast!

Science and Technology

Later, we were back on the bridge but for a sadder reason. A dead whale was floating in the water right near the boat. I asked if anyone comes to pick up dead whales. It was explained to me that if a dead whale washes ashore, it will be picked up and taken for a necropsy to see if the cause of death could be determined. However, if they are at sea, they will be left to decompose and become part of the sea once again.

On a happier note, I was sent to the bridge later in the day to see if there were any whales in the vicinity as we do not fish if whales are nearby. It turned out that there were 5 whales in the distance (but close enough to see with binoculars). Whales are somewhat easy to spot as they must come to the surface often to breathe. When they exhale, they produce a spout of moist air from their blowhole. Since different species of whales produce different shape or size spouts, the spout is one way to identify the type of whale you are seeing. Other identifying features are size, color, fin shape, and whether they are alone or in a group. Some whale species travel in groups or pods, while others are more solitary. For example, killer whales (which are really dolphins) spend much of their time in large groups that travel and hunt together. Sometimes 4 generations of killer whales will be found together. In contrast, humpback whales are more often found alone or with their calf.

Whale Fun Facts

While many people think that whales spout water, it is actually mostly air. The spout is their exhale. Since they are mammals, and not fish, they do not have gills, and must come to the surface to breathe through their blowhole.

A baby whale is called a calf.

A group of whales travelling together is called a pod.

The blue whale is the largest animal in the world. It can grow to be as long as 3 buses, and its heart is as big as a car. Despite being so large, blue whales eat some of the smallest marine life, such as the krill discussed in an earlier blog.

A blue whale’s call is so loud, it can be heard underwater for hundreds of kilometers.

Whales are warm-blooded, so they need to develop a layer of fat (called blubber) to stay warm in cold water.

Whale blubber experiment for parents and kids to do together

Make a blubber glove by filling 2 ziploc-type plastic bags with shortening (such as Crisco) and taping them together to form a pocket.

Fill a bowl with water and ice cubes.

Allow your child to quickly touch the cold water in the bowl with their bare hand.

Then have your child put his or her hand in the blubber glove, and then put their gloved hand into the cold water.

July 16, 2013August 13, 2021

Amie Ell: A Whale of Tale, July 13, 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 13, 2013

Location Data from the Bridge:
Latitude: 57.21N
Longitude: 152.32 W
Ship speed: 10.7 kn

Weather Data from the Bridge:
Air temperature: 11 degrees centigrade
Surface water temperature: 11 degrees Centigrade
Wind speed: 7.14 kn
Wind direction: 90 degrees
Barometric pressure: 1018 mb

Science and Technology Log:

The scientists on the Oscar Dyson are using several different types of cameras and sensors. I have already mentioned the CamTrawl. This camera is attached to the trawl net and takes pictures as the net is being dragged behind the ship. The pictures are time stamped. These pictures help to identify at what time and depth things were entering the net. This is very helpful if you have a haul with a variety of different fish. Also attached to the net is the FS-70 Netsond sensor, also known as the third wire.

A CamTrawl Picture with pollock and capelin.

This third wire uses sound and its echo to see what is entering the net. One more sensor attached to the net reads temperature and depth this is the SeaBird Electronics SBE-39 Bathythermograph.

From left to right: DropCam, winch, CTD (Conductivity, Temperature, Depth),

Sometimes sensors and cameras are dropped from the side of the ship. These are not attached to a net. Instead, these are on frames that are dropped over the side and lowered using thick cable wire on a winch. The CTD sensor measures water conductivity, temperature, and depth.

The Drop Camera also is dropped from the side of the ship and lowered using a winch. This also has a depth sensor and takes time stamped pictures. This device can help scientists identify fish present in areas that they are not able to trawl in.

The compilation of information gathered from these sensors, cameras, and haul data will help scientists get a good picture of what type and how many fish are present in different areas around Alaska and in varying ocean conditions. The analysis of this data will be used to help determine the quota for commercial fishermen looking for the Alaskan walleye pollock in different areas.

There are sensors on the hull of the ship that are always gathering information. On the NOAA website Ship Tracker you can see some of this information in real time.

Depths recorded and graphed for this trip.

Personal Log

Yesterday was an excellent day for whale watching. We spent our afternoon and evening surrounded by a pod of Humpback whales. At times they were so close that I could hear them breathing. They were much closer and more plentiful than the first whale sighting. Last night in the mess hall I got up to look out the porthole (window) and a whale came up less than 50 feet from me. It was amazing!

We continue to trawl pulling up on average 2 to 3 hauls an evening. In our hauls the majority of the fish are pollock. This week I have also seen, more capelin, rock fish, and lumpsuckers. We have also pulled up dog salmon, arrow tooth flat fish, krill, cod, and a spiny lumpsucker.

From bottom: Dog Salmon, Arrow Tooth, Pacific Ocean Perch (POP)

I was given a tour of the engine rooms below by the Chief Engineer. It was very loud. There is a lot of machinery on board to make the ship self-sustainable while at sea. One of the machines is called the “water maker”. This takes salt water and heats it to 140 degrees Fahrenheit. The machine then captures the steam, leaving behind salt and other non desired items in the water. The steam is then condensed to make all for the fresh water for the ship.

Water Maker distills salt water to make fresh

July 10, 2013August 11, 2021

Adam Renick, Searching for Cetaceans and Wrapping Up, June 25, 2013

NOAA Teacher at Sea
Adam Renick
Aboard NOAA Ship Oscar Elton Sette
June 12–26, 2013

Mission: Kona Integrated Ecosystems Assessment http://www.pifsc.noaa.gov/kona_iea/
Geographical area of cruise: The West Coast of the Island of Hawaii
Date: Tuesday, June 25, 2013

Weather Data
Current Air Temperature: 77° F
Sea Surface Temperature: 77° F
Wind Speed: 3 knots

Finding the Cetaceans…

In the final days of our research cruise we set out to get an assessment of cetacean activity in the Kona area that we have been studying. In addition to the ongoing active acoustics, CTD and DIDSON sampling, we have added two new tasks to the science team to find as many cetaceans as possible. We have set up a hydrophone, which is a sound recorder that sits in the water and is pulled by the ship, to listen for the clicks, whistles and any other sounds dolphins and whales might make.

For examples of sounds cetaceans make please check out this website. When the sounds from the cetaceans are received the wave frequencies are recorded using some very interesting software that helps us determine the type of marine mammal it is and where it is located. Specifically locating and identifying the cetaceans requires the cooperation of many people and is not necessarily as simple as I am making it sound here.

Melons — The recording of a pod of approximately 150 Melon-Headed Whales. Credit: Ali Bayless

The sounds of Pilot Whales. Credit: Ali Bayless

While the acoustics team and the ship’s crew are listening and seeking out the animals we also assist in the effort by making visual observations from the highest deck of the boat called the “flying bridge”. Here one or two people who are in communication with the science team below use binoculars and “big eyes” to visually find and identify marine mammals.

Blog5 013 — Looking through the “big eyes”

Some of my personal observing highlights of this operation include a sperm whale, a pod of approximately 150 melon-headed whales and smaller pods of spinner dolphins, rough-toothed dolphins, rough-toothed dolphin and pilot whales.

SE 13-04 Melon Heads — Visual observations of the Melon-Headed Whales.
Photo: Chad Yoshinaga

Rough-toothed_Dolphins — Rough Toothed Dolphins
Photo: Ali Bayless

Wrapping Up the Journey…

I cannot express enough gratitude to the members of the science team and the crew of the Sette for making my NOAA Teacher At Sea experience so rewarding. There are so many elements of this trip that are worth pause, reflection and appreciation. My emotions ranged from excitement just being at sea for 15 days and living a lifestyle that is unique and different than my own, the contemplative awe of the vast and complicated ocean ecosystem and the exhilaration when one of its own breaches the surface to give us a peek at it. In the end, I think my greatest appreciation gained along this journey was learning to slow myself down to the pace of nature in order to better observe and understand it.What’s next for me? NASA Teacher In Space… 2014 here I come!

Just kidding (is that even possible?) Until then I guess I should practice my moon-walking on Kilauea crater until I head back to my amazing wife and life in San Diego. Thanks for reading and, whatever you are doing out there in the world today, make a memory.

July 8, 2012August 11, 2021

Amanda Peretich: CTD and XBT – More Acronyms? July 8, 2012

NOAA Teacher at Sea
Amanda Peretich
Aboard Oscar Dyson
June 30 – July 18, 2012

Mission: Pollock Survey
Geographical area of cruise: Bering Sea
Date: July 8, 2012

Location Data
Latitude: 57ºN
Longitude: 172ºW
Ship speed: 11.2 knots (12.9 mph)

Weather Data from the Bridge
Air temperature: 6ºC (42.8ºF)
Surface water temperature: 7ºC (44.6ºF)
Wind speed: 2.5 knots (2.9 mph)
Wind direction: 156ºT
Barometric pressure: 1020 millibar (1.0 atm, 765 mmHg)

Science and Technology Log
Today’s post is going to be about two of the water profiling devices used on board the Oscar Dyson: the CTD and XBT.

CTD
CTD stands for Conductivity, Temperature, and Depth. It’s actually a device that is “dropped” over the starboard side of the ship at various points along the transect lines to take measurements of conductivity and temperature at various depths in the ocean. On this leg of the pollock survey, we will complete about 25-30 CTD drops by the end. The data can also be used to calculate salinity. Water samples are collected to measure dissolved oxygen (these samples are analyzed all together at the end of the cruise). Determining the amount of oxygen available in the water column can help provide information about not only the fish but also other phytoplankton and more. Although we are not doing it on this leg, fluorescence can also be measured to monitor chlorophyll levels.

*From left to right*: getting the CTD ready to deploy, the winch is used to put the CTD into the water, the CTD is lowered into the water – notice that the people are strapped in to the ship so they don’t fall overboard during deployment

DYK? (Did You Know?): What exactly are transect lines? Basically this is the path the ship is taking so they know what areas the ship has covered. Using NOAA’s Shiptracker, you can see in the photo where the Oscar Dyson has traveled on this pollock survey (both Leg 1 and Leg 2) up to this point in time.

Deploying the CTD — I was lucky enough to be able to operate the winch during a CTD deploy. The winch is basically what pulls in or lets out the cable attached to the CTD to raise and lower it in the water. Special thanks to the chief boatswain Willie for letting me do this!

The CTD can only be deployed when the ship is not moving, so if weather is nice, we should just stay mostly in one place. The officers on the bridge can also manually hold the ship steady. Or they can use DP, which is dynamic positioning. This computer system controls the rudder and propeller on the stern and the bowthruster at the front to maintain position.

Here is a video from a previous Teacher at Sea (TAS) about the CTD and showing its “drop” into the water: Story Miller – 2010. Another TAS also has a video on her blog showing the data being collected during a CTD drop: Kathleen Harrison – 2011.

XBT

Thermocline — The thermocline is the area where the upper isothermal (mixed) layer meets the deep water layer and there is a decline in temperature with increasing depth.

XBT is the acronym for the eXpendable Bathymetric Thermograph. It is used to quickly collect temperature data from the surface to the sea floor. A graph of depth (in meters) versus temperature (in ºC) is used to find the thermocline and determine the temperature on the sea floor.

DYK? Normally, temperature decreases as you go farther down in the sea because colder water is denser than warmer water so it sinks below. But this is not the case in polar regions such as the Bering Sea. Just below the surface is an isothermal layer caused by wind mixing and convective overturning where the temperature is approximately the same as on the surface. Below this layer is the thermocline where the temperature then rapidly decreases.

The MK-21IISA is a bathythermograph data acquisition system. This is a portable (moveable) system used to collect data including ocean temperature, conductivity, and sound velocity and various depths using expendable probes (ones you can lose overboard and not get back) that are launched from surface ships. The depth is determined using elapsed time from surface contact and a known sink rate.

There are three different probes that can be used with this data acquisition system:
1. XBT probe – this is the probe that is used on OD, which only measures water temperature at various depths
2. XSV probe – this probe can measure sound velocity versus depth
3. XCTD probe – this probe measures both temperature and conductivity versus depth

On the XBT probe, there is a thermistor (something used to measure temperature) that is connected to an insulated wire wound on two spools (one inside the probe and one outside the probe but inside the canister). The front, or nose, of the probe is a seawater electrode that is used to sense when the probe enters the water to begin data collection. There are different types of XBT probes depending on the maximum depth and vessel speed of the ship.

XBT Canister and Probe — This shows a sideview (*left*) and topview (*middle*) of the canister that houses the probe (*right*) released into the water during an XBT.

There are really four steps to launch the XBT probe using the LM-3A handheld launcher on board:
1. Raise contact lever.
2. Lay probe-containing canister into cradle (make sure to hold it upwards so the probe doesn’t fall out of the canister!).
3. Swing contact level down to lock in canister.
4. Pull release pin out of canister, aim into ocean, and drop probe.
Important: the wire should not come in contact with the ship!

Launching an XBT — “Launching” an XBT probe from starboard side on the *Oscar Dyson*. There is no actual trigger – you just make a little forward motion with the launcher to allow the probe to drop into the water.

Be sure to check out the video below, which shows what the data profile looks like as the probe is being dropped into the water. An XBT drop requires a minimum of two people, one at the computer inside and one outside launching the probe. I’ve been working with Scientist Bill and ENS Kevin to help out with the XBT launches, which also includes using the radios on board to mark the ship’s position when the probe hits the water.

Personal Log

It’s been a little slow on the trawling during my shift recently, so I’ve had some extra time to wander around the ship and talk to various people amidst researching and writing more blog posts. I think one of my favorite parts so far has been all of the great information I’ve been learning up on the bridge from the field operations officer, LT Matt Davis.

DYK? When looking at the map, you’d think the quickest route from Seattle, Washington to Japan would be a straight line across the Pacific Ocean. But it’s not! Actually, ships will travel by way of Alaska and it is a shorter distance (and thus faster).

View from the Bow — View from the bow of the *Oscar Dyson*.

Vessels use gnomonic ocean tracking charts to determine the shortest path. Basically a straight line drawn on the gnomonic projection corresponds to a great circle, or geodesic curve, that shows the minimum path from any two points on the surface of the Earth as a straight line. So on the way to Japan from Seattle, you would travel up through Alaskan waters, using computer software to help determine the proper pathway.

I’ve also had some time to explore a few other areas of the ship I hadn’t been to before. I’ve learned some new lingo (look for this in an upcoming post) and plenty of random facts. One of the places I checked out is the true bow of the ship where, if I was standing a bit higher (and wearing a PFD, or personal flotation device), I’d look like I was Rose Dawson in one of the scenes from Titanic.

Animal Love
All of the time I spend on the bridge also allows for those random mammal sightings and I was able to see a few whales from afar on July 7!

Whale Sighting — Whale sighting from the bridge! You have to look really closely to see their blow spouts in the middle of the photo.