byCatch – NOAA Teacher at Sea Blog

August 4, 2026August 6, 2026

Jo Slavitz: Expect the Unexpected, July 30, 2026

NOAA Teacher at Sea

Jo Slavitz

Aboard NOAA Ship Oscar Dyson

July 19th – August 10th

Mission: Summer Pollock Acoustic-Trawl Survey, Leg 3

Geographic Area of Cruise: Bering Sea, Alaska

Date: July 30, 2026

Weather Data from Bering Sea

Latitude: 58° 38.303’ N

Longitude: 176° 17.674’ W

Winds: SW at 9 mph

Air Temperature: 46.94° F (8.3° C)

“It is that range of biodiversity that we must care for – the whole thing – rather than just one or two stars.” – David Attenborough

Science and Technology Log

NOAA scientists conducting the Acoustic-Trawl survey are skilled at finding pollock, but even, so tiny amounts of other species also sometimes slip into the net. These unexpected creatures are called “bycatch.” Although not targeted, it doesn’t mean that these species are not important. A healthy pollock population depends on a complete and healthy ecosystem, so the science team also measures and takes data on these creatures before releasing most of them back to the water. Sometimes, the science team also gathers information about these species for other scientists on land conducting special projects for other programs. Here are some of the interesting fish that came in with trawls aboard Oscar Dyson on Leg 3.

Jellyfish

Outside of pollock, jellyfish have been the most frequent visitor to the trawl. Existing before dinosaurs, jellyfish trace their origin back over 500 million years, their closest relatives being corals and anemones. They are invertebrates (meaning they do not have a backbone) in the phylum Cnidaria, subphylum Medusozoa. Jellyfish are found around the planet in the world’s oceans and even in some fresh water ponds/lakes. Not a fish at all, jellies contain no brain, bones, gills or hearts. They are considered a keystone organism, one that holds the ecosystem together because it interacts with so many other species within the food web. Jellyfish’s main diet consists of tiny animals and plankton. They serve as food for sea turtles, fish, crabs, birds and even humans. Even though they can often sting, small animals will swim among jellies to hide from predators. So far we have seen 3 species of jellyfish in the trawls in the Bering Sea:

Chrysaora: The most common jellyfish found in the trawls this trip are by far Chrysaora. These stunning animals get their name from mythology. Chrysaor was the warrior child of Poseidon the sea god and Medusa, and his name means “adorned in gold” or “golden warrior.” It’s the perfect name for this golden beauty. Chrysaora are in the family commonly referred to as sea nettles. They can grow to reach up to 2’- 3’ in diameter. Chrysaora is typically found at depths up to 100 meters in the Bering and Arctic Seas. Since the 1990’s the total biomass of this species has been increasing. Biomass is the total amount of mass of an animal population in a specific area.

Jo, wearing overalls, long yellow gloves, and sunglasses, leans forward over a sorting table in the wet lab. On the table in front of her is a yellow-orange jellyfish that may be 3 feet in diameter. — Chrysaora Jellyfish

Aequorea: Less showy and bright than Chrysaora, Aequorea jellies are predominantly clear with a flat smooth disk-shaped bell. Its name is taken from the Latin words aequor “from the sea” and aequus “even, flat or level.” Their family is commonly known as crystal jellies. This family of jellyfish fascinates scientists because they contain photoproteins that allow them to fluoresce with bioluminescence. Bioluminescence is the ability for animals to create their own light. Animals such as backyard lightning bugs and deep-sea fish are also capable of this unique adaptation.

close-up view of a completely translucent jellyfish spread out on a white plastic measuring board. we can read the measuring line through the jellyfish; it extends from about 2.5 cm to about 13.5 cm. — Aequorea Jellyfish

Aurelia: Aurelia or moon jellyfish are one of the most widely distributed family of jellies. A. limbata, or brown moon jellies are native to the Bering Sea and coastal Alaska. They range in size from about 9 to 12 inches in diameter. They have a clear cup-shaped bell with brown to orange organs arranged in a circle around the center.

Fish

Pacific Cod: A relative of the Alaskan pollock, Pacific cod are also a cold water whitefish. Also similar to pollock, many people like to cook and eat cod, so this fish ended up as our guest in the mess later that night for dinner.

cooked fish filet plated with vegetables, topped with a lemon slice

A Pacific cod in sample basket; later, plated for dinner in the mess hall

Northern Rock Sole: As a bottom dweller, the northern rock sole has both eyes on a single side of its head. His topside is a splotchy brown color, while his underside is a translucent white.

mottled brown right-eyed flatfish laid out against a white surface — Northern Rock Sole

Chum Salmon: Though this one is not so big. Chum salmon are the second largest pacific salmon after chinook. Males of this species develop large canine-like fangs

one salmon in a green plastic basket — Chum Salmon

Smooth Lumpsucker: A deep-sea fish, the smooth lumpsucker has a slippery, scaleless skin. Look closely to see the circle on its underside. The pelvic fins in this species are modified to form a disk used to help secure the fish to ocean surfaces in fast moving waters.

a remarkably round fish held up in someone's glove hand tilted toward the ceiling to reveal the suction disk on its underside — Smooth lumpsucker

Try It on Dry Land

Although you may not be able to hitch a ride out to the Bering Sea for the pollock acoustic survey, you can create your own trawling simulation with a box of Trix cereal and a few kitchen materials.

Trix Trawl

Materials:

1 box Trix Cereal
1 cookie sheet or shallow baking pan
A ruler
Tape
1 Tbs measuring spoon or scoop
Data chart (downloadable pdf)

* Optional small kitchen scale

Instructions

Use ruler to measure and mark with tape both long sides of the cookie sheet in 2” segments. These are your transects lines that you will sample from.
Drag the tablespoon from the mark on one side to the corresponding mark on the opposite side. This is your trawl net. You may not touch the cereal with anything but the spoon.
Sort the cereal into groups of the same shape/color type and record on data sheet.
Repeat until all steps until transects are complete.

Did you get the same number for each shape/color?
Do you feel like it was an accurate representation for all the cereal in the box?
Did you find anything unexpected in the cereal box?
NOAA scientists also gather the weight for each species group. If you have a small kitchen scale you can weigh each shape/color group and record. Is the set with the most individual pieces also the heaviest?

Trix Trawl data Download

Happy Sampling!

Jo, wearing overalls, yellow gloves, and sunglasses, stands in the wet lab in front of stacks of plastic sample bins. She stretches her arms toward the camera to show off a large, yellow-orange chrysaora jelly. a few pollock are visible on the sorting table off to the side. — Jelly Love

August 21, 2019

Callie Harris: Lots to See While at Sea, August 20, 2019

NOAA Teacher at Sea

Callie Harris

Aboard NOAA Ship Oscar Dyson

August 13-26, 2019

Mission: Fisheries-Oceanography Coordinated Investigations

Geographic Area of Cruise: Gulf of Alaska

Date: 8/20/19

Weather Data from the Bridge

Latitude: 58° 27.67 N
Longitude: 152 ° 53.00 W
Wind Speed: 5.96 knots
Wind Direction: 152°
Air Temperature: 12.4°C
Sea Temperature: 15°C
Barometric Pressure: 1008 mbar

Science and Technology Log

I feel the need to start off by stating that the shark did in fact swim away. During our mid-afternoon trawl haul back, Chief Boatswain Ryan Harris called over the radio that we had caught a shark in the trawl net. We quickly put on our boots, hard hats, and life preservers and headed to the back deck. Unfortunately, a 3.2m female Pacific Sleeper Shark had gotten caught in our trawl as bycatch. Thanks to the quick response of our NOAA deck crew, we were able to release the shark back into the water alive.

Pacific Sleeper Shark
Pacific Sleeper Shark

Unlike most sharks, the Pacific Sleeper Shark is predominantly a scavenger and rarely hunts. They are slow swimmers, but move through the water quite gracefully without much effort of body movement. This lack of movement allows them to catch prey easy since they don’t make much noise/ vibrations in the water. They feed by cutting and suction. The sleeper shark’s large mouth allows it to suck its prey in. Its spear-like teeth help cut prey down into smaller pieces. It then swallows its prey by rolling its head. For more info about this cool shark, visit: https://www.sharksider.com/pacific-sleeper-shark/ .

Bycatch is defined as the unwanted fish and other marine creatures caught (e.g. hooked, entangled or trapped) during commercial fishing for a different species. Bycatch is both an issue ecologically and economically. Bycatch can slow the rebuilding of overfished stocks. Organisms that are discarded sometimes die and cannot reproduce. These mortalities put protected species such as whales and sea turtles even further at risk. Bycatch can change the availability of prey and cause cascading effects at all trophic levels. Bycatch can also occur when fishing gear has been lost, discarded, or is otherwise no longer being used to harvest fish (aka marine debris).

Releasing shark from net — Releasing the shark from our trawl net.

NOAA Fisheries works hand in hand with fishing industries to better understand fishing gear, and to develop, test, and implement alternative fishing gear. For example, NOAA Fisheries and their partners developed turtle excluder devices to reduce sea turtle mortality in the southeastern shrimp trawl fishery. NOAA Fisheries funds the Bycatch Reduction Engineering Program that supports the development of technological solutions and changes in fishing practices designed to minimize bycatch. Laws like the Marine Mammal Protection Act and the Endangered Species Act also uphold the reduction of current and future bycatch of species.

Personal Log

It’s hard to believe that today is already day eight at sea. To be honest, I don’t even notice that I am on a ship anymore. We have been very lucky weather wise and the seas are still very calm. I have been spending more time on the bridge assisting with the ‘marine mammal watch’. As I said in blog two, we must keep an eye out for any marine mammals in the area before conducting any water surveys. The bridge is amazing because not only do you get the best view, but you also get to observe how the ship operates in terms of headings, maneuverability, and navigation.

The Shelikof Strait is breathtaking. Chief Electronics Technician Rodney Terry pointed out the white ‘cloud’ above one of the snow-capped mountains was actually an active volcano with a smoke plume rising above it. It was incredible to be able to look out and see a glacier and an active volcano in the same panorama.

Map of Kodiak Island and Shelikof Strait. Credit: Kodiak archipelago images.

During one of my marine mammal watches on the bridge, I noticed an oddly flat area of land in the middle of the mountain range that ran along the shoreline. NOAA Corps Officer LT Carl Noblitt explained to me this was actually where a glacier had once weathered down part of the mountain range over time. The glacier has since melted so now all that remains today is its glacial trough.

Animals Seen Today

Besides our unexpected visitor today in the trawl, I was thrilled to hear Chief Boatswain Ryan Harris call out from the scientific deck for Orcas on the horizon. Orcas (aka Killer Whales) have always been a dream of mine to see in the wild. They were pretty far away from the boat, but I was able to see the trademark black dorsal fin rising and sinking at the surface for a few minutes. Hoping to get a photo of one of these pods before our expedition ends.

orca dorsal — Orca dorsal fin. Photo Credit: gowhales.com

Another fun organism I got to see in person today was a Lanternfish that was caught in one of our deeper bongo net surveys. Lanternfish are a deep-water fish that gets its name from its ability to produce light. The light is given off by tiny organs known as photophores. A chemical reaction inside the photophore gives off light in a chemical process known as bioluminescence.

lanternfish v pencil — This laternfish is full grown. Adults measure 5cm to 15cm in length typically.

April 1, 2017April 1, 2017

Emily Sprowls: Shark Bait, March 28, 2017

NOAA Teacher at Sea

Emily Sprowls

Aboard NOAA Ship Oregon II

March 20 – April 3, 2017

Mission: Experimental Longline Survey

Geographic Area of Cruise: Gulf of Mexico

Date: March 28, 2017

Weather Data from the Bridge

RedSnapper — Red snapper (*Lutjanus campechanus*)

13:00 hours

29°09.3’ N 88°35.2’W

Visibility 10 nm, Scattered clouds

Wind 8 kts 170°E

Sea wave height <1 ft.

Seawater temp 22.9°C

Science and Technology Log

In addition to experimenting by sampling deeper, we are varying the fishing gear and using different kinds of bait. We have switched to hooks on a steel leader so that even a strong, big shark cannot bite through the line. We are rotating through squid and mackerel as bait in order to see which species are more attracted to different bait. In addition to many species of sharks, we have also caught and measured eels, large fish and rays.

Nick hooks — Nick prepares hooks for longline gangions.

One of the scientists on board specializes in fishing gear, and helps keep maintain all our gear after it gets twisted by eels or looped up on itself. He also works on turtle exclusion devices for trawling gear.

Personal Log

Last night the line pulled in a huge tangle of “ghost gear.” This was fishing line and hooks that had been lost and sunk. It would have been much easier to just cut the line and let the mess sink back to where it came from, but everybody worked together to haul it out so it won’t sit at the bottom tangling up other animals.

This is just one example of the dedication the scientists and crew have to ocean stewardship. I have been so impressed by the care and speed with which everybody handles the sharks in order to get them back in the water safely.

Kids’ Questions

Is there any bycatch of dolphins?

Deep seastar — A few seastars come up with uneaten bait as bycatch.

Today we saw dolphins for the first time! They were only a few of them pretty far from the boat, so they did not affect our sampling. Had they decided to come play by riding in our wake, we would have postponed our sampling to avoid any interactions between the dolphins and the gear. One of the reasons that we only deploy the fishing gear for one hour is in case an air-breathing turtle or mammal gets tangled (they can hold their breath for over an hour). However, since dolphins hunt live fish, they don’t try to eat the dead bait we are using.

Can sharks use echolocation? How do they find their food?

Sharks do not use echolocation like marine mammals, but they do have an “extra” sense to help them find their food. They can detect electrical current using special sense organs called ampullae of Lorenzini.

What are the chances of getting hurt? Why don’t they bite?

While there is a chance of the sharks accidentally biting us as we handle them, we are very careful to hold them on the backs of their heads and not to put our fingers near their mouths! “Shark burn” is a more likely injury, which occurs when a shark wiggles and their rough skin scrapes the person handling them. Sharks do not have scales, but are covered in tiny, abrasive denticles that feel like sandpaper.

July 21, 2016August 21, 2021

Cathrine Prenot: Lights in the Ocean. Thursday, July 21, 2016

NOAA Teacher at Sea
Cathrine Prenot
Aboard Bell M. Shimada
July 17-July 30, 2016

Mission: 2016 California Current Ecosystem: Investigations of hake survey methods, life history, and associated ecosystem

Geographical area of cruise: Pacific Coast from Newport, OR to Seattle, WA

Date: Thursday, July 21, 2016

Weather Data from the Bridge
Lat: 46º18.8 N
Lon: 124º25.6 W
Speed: 10.4 knots
Wind speed: 12.35 degree/knots
Barometer: 1018.59 mBars
Air Temp: 16.3 degrees Celsius

Science and Technology Log

The ship’s engineering staff are really friendly, and they were happy to oblige my questions and take me on a tour of the Engine Rooms. I got to go into the ‘belly of the beast’ on the Oscar Dyson, but on the tour of the Shimada, Sean Baptista, 1st assistant engineer, hooked us up with headsets with radios and microphones. It is super loud below decks, but the microphones made it so that we could ask questions and not just mime out what we were curious about.

I think the job of the engineers is pretty interesting for three main reasons.

On the way to see the bow thruster below decks

One, they get to be all over the ship and see the real behind-the-scenes working of a huge vessel at sea. We went down ladders and hatches, through remotely operated sealed doors, and wound our way through engines and water purifiers and even water treatment (poo) devices. Engineers understand the ship from the bottom up.

One of four Caterpillar diesel engines powering the ship

Second, I am sure that when it is your Job it doesn’t seem that glamorous, but an engineer’s work keeps the ship moving. Scientists collect data, the Deck crew fish, the NOAA Corps officers drive the ship, but the engineers make sure we have water to drink, that our ‘business’ is treated and sanitary, that we have power to plug in our computers (the lab I am writing in right now has 6 monitors displaying weather from the bridge, charts, ship trackers, and science data) and science equipment.

Finally, if something breaks on the ship, engineers fix it. Right there, with whatever they have on hand. Before we were able to take the tour, 1st Assistant Engineer Baptista gave us a stern warning to not touch anything—buttons, levers, pipes—anything. There is a kind of resourcefulness to be an engineer on a ship—you have to be able to make do with what you have when you are in the middle of the ocean.

The engineers all came to this position from different pathways—from having a welding background, to being in the navy or army, attending the U.S. Merchant Marine Academy, or even having an art degree. The biggest challenge is being away from your family for long periods of time, but I can attest that they are a pretty tight group onboard.

In terms of the science that I’ve been learning, I’ve had some time to do some research of some of the bycatch organisms from our Hake trawls. “Bycatch” are nontargeted species that are caught in the net. Our bycatch has been very small—we are mostly getting just hake, but I’ve seen about 30-40 these cute little fish with blue glowing dots all over their sides. Call me crazy, but anything that comes out of the ocean with what look like glowing sparkling sapphires is worthy of a cartoon.

So… …What is small, glows, and comprises about 65% of all deep-sea biomass? Click on the cartoon to read Adventures in a Blue World 3.

Adventures in a Blue World, CNP. Lights in the Ocean

Personal Log

The weather is absolutely beautiful and the seas are calm. We are cruising along at between 10-12 knots along set transects looking for hake, but we haven’t seen—I should say “heard” them in large enough groups or the right age class to sample. So, in the meanwhile, I’ve taken a tour of the inner workings of the ship from the engineers, made an appointment with the Chief Steward to come in and cook with him for a day, spent some time on the bridge checking out charts and the important and exciting looking equipment, played a few very poor rounds of cornhole, and have been cartooning and reading.

I was out on the back deck having a coffee and an ice cream (I lead a decadent and wild life as a Teacher at Sea) and I noticed that the shoreline looked very familiar. Sure enough—it was Cannon Beach, OR, with Haystack Rock (you’ll remember it from the movie The Goonies)! Some of my family lived there for years; it was fun to see it from ten miles off shore.

Chart showing our current geographic area. Center of coast is Cannon Bean, Oregon. — Chart showing our current geographic area. Center of coast is Cannon Beach, Oregon.

View of Tillamook Head and Cannon Beach. It looked closer in person.

Did You Know?

One of the scientists I have been working with knows a lot about fish. He knows every organism that comes off the nets in a trawl down to their Genus species. No wonder he knows all the fish—all of the reference books that I have been using in the wet lab were written by him. Head smack.

One of the books written by Dan Kamikawa, our fish whisperer

Resources

My sister (thank you!) does my multi media research for me from shore, as I am not allowed to pig out on bandwidth and watch lots of videos about bioluminescence in the ocean. This video is pretty wonderful. Check it out.

If you want to geek out more about Lanternfish, read this from a great site called the Tree of Life web project.

Interested in becoming a Wage Mariner in many different fields–including engineering? Click here.

June 19, 2016April 22, 2021

Donna Knutson: Dredging, June 16, 2016

NOAA Teacher at Sea Donna Knutson
Aboard R/V Hugh R. Sharp
June 8 – June 24, 2016

2016 Mission: Atlantic Scallop/Benthic Habitat Survey
Geographical Area of Cruise: Northeastern U.S. Atlantic Coast
Date: June 16, 2016

Dredging

Mission and Geographical Area:

The University of Delaware’s ship, R/V Sharp, is on a NOAA mission to assess the abundance and age distribution of the Atlantic Sea Scallop along the Eastern U.S. coast from Mid Atlantic Bight to Georges Bank. NOAA does this survey in accordance with Magnuson Stevens Act requirements.

Science and Technology:

Latitude: 40 32.475 N

Longitude: 67 59.499 W

Clouds: overcast

Visibility: 5-6 nautical miles

Wind: 7.4 knots

Wave Height: 1-4 ft.

Water Temperature: 53 F

Air Temperature: 63 F

Sea Level Pressure: 29.9 in of Hg

Water Depth: 103 m

Science Blog:

Paired with the HabCam, dredging adds more data points to the scallop survey and also to habitat mapping. Various locations are dredged based on a stratified random sampling design. This method uses the topography of the ocean bottom as a platform and then overlays a grid system on top. The dredged areas, which are selected randomly by a computer program, allow for a good distribution of samples from the area based on topography and depth.

Vic and Tasha sewing up the net on the dredge.

A typical dredge that used for the survey is similar to those used by commercial fisherman, but it is smaller with a width of 8 ft. and weight of 2000 lbs. It is towed behind a ship with a 9/16 cable attached to a standard winch. Dredges are made from a heavy metal such as steel and is covered in a chain mesh that is open in the front and closed on the other three sides making a chain linked net made of circular rings.

A fisherman’s dredge has rings large enough for smaller animals to fall through and become released to the bottom once again. The dredge in a survey has a mesh lining to trap more creatures in order to do a full survey of the animals occupying a specific habitat.

There are three categories of catch received in a dredge: substrate, animals and shell. A qualitative assessment on percent abundance of each is done for every dredge. Not all animals are measured, but all are noted in the database.

A length measurement is taken for every scallop, goosefish (also called monkfish), cod, haddock, as well as many types of flounder and skate. A combined mass is taken for each species in that dredged sample. Some animals are not measured for length, like the wave whelk (a snail), Jonah crab, and fish such as pipefish, ocean pout, red hake, sand lance; for these and several other types of fish, just a count and weight of each species is recorded.

Other animals may be present, but not

counted or measured and therefore are called bycatch. Sand dollars make up the majority of bycatch. Sponges, the polychaete Aphrodite, hermit crabs, shrimp and various shells are also sorted through but not counted or measured.

All of the dredge material that is captured is returned to the ocean upon the required sorting, counting and measuring. Unfortunately, most of the fish and invertebrates do not survive the ordeal. That is why it is important to have a good sampling method and procedure to get the best results from the fewest dredge stations needed.

Goosefish, often called Monkfish, eat anything.

The dredge is placed on the bottom for only fifteen minutes. There are sensors on the frame of the dredge so computers can monitor when the collection was started and when to stop. Sensors also make certain each dredge is positioned correctly in the water to get the best representation of animals in that small sample area.

Entering the name of the animals to be measured.

Even with sensors and scientists monitoring computers and taking animal measurements, the dredging can only give a 30-40% efficiency rating of the actual animals present. Dredging with the aid of the HabCam and partnerships with many scientific organizations, along with data from commercial fisherman and observer data, create a picture of abundance and distribution which can be mapped.

Adductor muscle the "meat" of the scallop. This on is unhealthy. — Adductor muscle the “meat” of the scallop. This one is unhealthy.

In the scallop survey the emphasis is on where are the most scallops present and this aids fisherman in selecting the best places to fish. The survey also suggests where areas should be closed to fishing for a period, allowing scallops to grow and mature before harvesting.

This management practice of opening closed areas on a rotational basis has been accepted as beneficial for science, management, and fishermen. This method of balancing conservation and fishing protects habitats while still supplying the world with a food supply that is highly valued.

Personal Blog:

Being part of a dredging team is exciting. It is a high energy time from the moment the contents are dropped on the sorting platform to the end when everything is rinsed off to get ready for the next drop.

Katryn "Kat" Delgado — Kateryn “Kat” Delgado

I wanted to take pictures of everything, but with gloves on it was hard to participate and help out or just be the bystander/photographer. Kateryn Delgado from Queens NY, a volunteer/student/scientist/yoga instructor/photographer, was very helpful. She was involved in other surveys and often took pictures for me.

I did find it sad that the animals we sorting were not going to live long once returned to sea, but that is a part of the dredging that is inevitable. Raw data needs to be collected. After measuring, a percentage of the scallops were dissected to get their sex, abductor muscle (meat), and stomach. Shell size was compared to the meat and gonad mass and is also used to age the scallop. The stomach was removed to test for microplastics. Dr. Gallager and his research team are studying microplastics in the ocean. Scallops filter relatively large particles for a filter feeder, and therefore are a good species to monitor the abundance of plastics at the bottom of the ocean.

The weather has been nice, not very warm, but the waves are low. Just the way I like them. We are making our way back to Woods Hole to refuel and get groceries. I didn’t realize we would split up the leg into two parts. We should be in around 10:00 a.m. I’m going to go for a long walk since there is not a lot of opportunity for exercise on the ship. Hope it’s sunny!