Posted on by lisacarlson2023

Lisa Carlson: Come Out, Come Out, Wherever You Are, Hake! July 6, 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 6, 2023

Weather Data from the Bridge:

— July 5 Departure
(1800 PT, 2100 EST)
Location: 37° 44.9’N, 122° 39.2’W
Docked at Pier 30/32
San Francisco, CA

Visibility: 10 nautical miles
Sky condition: Overcast
Wind: 17 knots from NW 300°
Barometer: 1012.8 mbar
Sea wave height: 1-2 feet
Swell: 2-4 ft from W 270°
Sea temperature: 14.2°C (57.6°F)
Air temperature: 14.7°C (58.5°F)
Course Over Ground: (COG): N/A
Speed Over Ground (SOG): N/A

— July 6 (1200 PT, 1500 EST)
Location: 35° 38.2’ N, 121° 18.9’ W
16nm (18mi) West of San Simeon, CA

Visibility: 10nm
Wind: 6 knots from 330°
Barometer: 1013.9
Sea wave height: 1-2ft
Swell: 2-4ft from 280°
Sea wave temperature: 14.4°C (57.9°F)
Air temperature: 14.9°C (58.8°F)
Course Over Ground: (COG): W 270°
Speed Over Ground (SOG): 10 knots

– – ⚓ – –

Science and Technology Log

On July 6, our first full day at sea, we gathered in the acoustics lab to observe and keep watch on data from various screens. Data includes our current course plotted on a digital chart, a camera showing current sea state, measurements of the wind speed and direction, and displays of the multiple frequencies at which the Simrad EK80 transmitter emits sound. The EK80 is used while traveling on numbered longitudinal east-west lines called transects. NOAA Ship Bell M. Shimada navigates on these lines while collecting acoustic data along the west coast of the U.S. and into Canada, in hopes of finding schools of Hake to collect for surveying.

A topographic map of a portion of the coast of California. The topographies of the both the land (beige and green scales) and water (blue scale) are depicted. Black dots mark the locations of three coastal cities: Crescent City, near the top of the map; San Francisco, a little more than halfway down; and Morro Bay, toward the bottom of the map. Black horizontal lines mark transects extending west from the coast line. The black lines are marked with red or black x's (showing previous sampling locations, perhaps) and a couple have green triangles.
Map showing transects 1-45 off the coast of California. Transect 1 is south of Morro Bay, CA and transect 45 is near Crescent City, CA.
(We hope to survey transects 8-35 by Cape Mendocino, CA before traveling north to dock in Newport, OR.)

“For acoustic surveys, the ship uses a multibeam echo sounder (MBES) that projects a fan-shaped beam of sound that bounces back to the ship. The ship’s MBES—one of only three systems of its type worldwide—acquires data from both the water column and the sea floor.”

NOAA Office of Marine and Aviation Operations (OMAO): “Bell M. Shimada”

The Simrad EK80 emits sound waves from the hull of the vessel down to the sea floor. The process is very similar to a dolphin or bat using echolocation to find prey. Any object the signal hits that has a different density and reflectivity than the surrounding water will cause the waves to bounce back to the ship. An image, called an echo gram, is pieced together each time this occurs and the acoustics team is able to use this information to determine if there are enough return signals that suggest fish are present to attempt a trawl.

photo of a computer screen depicting data
EK80 displaying returned sound waves at two different wave frequencies.
photo of a computer screen showing sonar readings
Display from sonar camera showing the outer edge of the net (between ring 2 and 3)
illustration of a ship at the surface of the ocean, with the ocean cut away to show a cone (representing sound pulses) extending from the ship's hull, toward the seafloor, over a school of fish
Image demonstrating the use of a MBES
“The sound pulses travel down into the water column, illustrated by the white cones here, and bounce back when encountering resistance.”
NOAA Fisheries: “Acoustic Hake Survey Methods on the West Coast”

Fish that have swim bladders, like bony fish, reflect or echo the sound wave back to the vessel very strongly. Other marine life such as myctophids and zooplankton also have a different density than the sea water, and reflect sound, although not as strongly as fish with air-filled swim bladders. The sea floor itself also reflects sound very strongly, because of the density difference between water and rocks, sand, and mud.

Marine life that have swim bladders (represented in blue) reflect or echo the sound wave back to the vessel. Examples of such marine life include bony fish, myctophids, and zooplankton, as well as the sea floor itself, which has a different density than the sea water.

Image: Cross section example of a Black Sea Bass to show a swim bladder.

an illustrated diagram of the internal anatomy of a bony fish (perhaps a black sea bass). Labels mark the locations of the gills, kidney, swim bladder, urine bladder, gonad, intestine, spleen, stomach, liver, and heart.

If the acoustics team determines there is enough marine life (that they are interested in surveying) to attempt a haul, they will notify the bridge deck and officers that they would like to have the fishing net deployed.

Before an attempted haul, the science team conducts a marine mammal watch for ten minutes. In this time window, several pairs of eyes are observing from the bridge deck and stern for any signs of dolphins, whales, sea lions, seals, and any other marine mammals that are within 500 meters of the vessel. If any marine mammals are spotted within the ten minute observation, we will stand down and wait ten minutes before restarting the marine mammal watch. Net deployment cannot occur until the full observation window has completed.

First haul July 6:
1422-1432 Mammal watch, no marine mammals spotted.
The net deployment started, at which time the vessel continues forward at two knots. Vessel speed increases to three knots when the net is fully deployed with doors and weights in the water, which assist in opening the conical shaped net outwards linearly and laterally. During this time the science team watches displays of the EK80 frequencies and observe the linear width and depth of the net. Scientists can compare these displays to determine if the net is in the correct position to have the best chance of collecting fish.

A man and a woman stand looking down at a row of computer monitors on the bridge. In the background, we see a map table, additional control panels, and the back of a NOAA Corps officer who is likely driving the vessel. A line of windows (only white visible through them) tells us this is the bridge.
Chief Scientist Steve de Blois monitoring EK80 frequencies and net information.
a view over the aft deck of NOAA Ship Bell M Shimada from a high point, perhaps the flying bridge. We can see a large A-frame with a big pulley; a large spool with yellow cables pays out to deploy a net (not visible) into the water. Several crewmembers, wearing life vests and hard hats, attend the operation. In the distance, beyond the water, there is a line of coastal mountains, topped with clouds.
Deck department deploying fishing net.
Two men wearing orange fish gloves lean down to sort through a large black bin full of sampled fish. One is reaching for a fish; the other is moving a handful of fish over to a smaller plastic green basket. Another pair of gloved hands is visible.
Wet Lab team takes over sorting Hake and other marine life.

Hauling back the net occurs after several minutes, at which time the vessel returns to a speed of two knots, and we estimate how many fish were collected. The amount of time in which the net is submerged depends on the depth of the water and acoustic information about the size of the school of fish the net is (hopefully) sampling. After recovery, the haul is deposited into a hopper which feeds onto a conveyor belt in the wet lab, then into large baskets and the wet lab team takes over.

During the first attempt, two sea lions were spotted which required the haul attempt to be paused. We restarted the ten minute marine mammal watch from 1500-1510, the deck department retrieved and reset the net, and the vessel was turned around to return to the start of the noted longitudinal transect. With no marine mammals spotted during the observation period, the second attempt was successful and resulted in:

– 1604-1634: 30 minute haul at 350m depth.

– 11 baskets of Hake collected.

– 4 sample baskets kept at random.

– 541 Hake counted and studied in the wet lab.

Photo: Two deck department members about to open the net to allow the sample to drop into a large collection basket.

Two crewmembers, dressed in orange paints and black and neon yellow coats, face away from the camera, toward a large orange net suspended from above. They may be working to empty the net.

– – ⚓ – –

Personal Log

On July 4 I arrived to pier 30/32 in San Francisco, CA to board NOAA Ship Bell M. Shimada. Although I grew up volunteering on the 441’ WWII Liberty Ship SS John W. Brown in Baltimore, MD, seeing a new ship still resulted in a mix of emotions, nervousness, adrenaline, excitement, and everything in between. After five and a half years, finally seeing the 208’ vessel that would become my home for the next two weeks was a core memory and feeling I will always remember.

NOAA Ship Bell M Shimada in port, as seen from a point on the dock beyond the bow. We can see the NOAA logo and read: NOAA R 227. The water is calm and turqoise; the sky is blue with clouds. A portion of what may be the Golden Gate Bridge is visible in the background.
NOAA Ship Bell M. Shimada docked at Pier 30/32 in San Francisco, CA on July 4

Once onboard, I met Chief Scientist Steve de Blois and Wet Lab Lead Ethan Beyer. I was given a tour of the acoustic, chem, and wet labs and shown to my cabin. After dinner ashore, I joined some of the crew on the flying bridge to watch the July 4th fireworks. I met additional science team members and enjoyed a long night’s rest.

In the morning on July 5, we had a welcome aboard meeting, various trainings, a safety meeting and orientation, fire and abandon ship drills, and a science team meeting. We introduced ourselves, took an official team photo, and soon departed pier 30/32 for our 14 day mission. After passing under the Golden Gate Bridge and heading to the Pacific Ocean, our cold hands were warmed by a wonderful hot dinner of chicken, steak, fresh veggies, salad, and desserts from our galley crew. After dinner, we settled in for our first night at sea, waiting with anticipation for our first trawl on July 6.

Lisa Carlson, wearing her Teacher at Sea t-shirt, stands on the pier in front of NOAA Ship Bell M Shimada
Last morning on land: July 5 at Pier 30/32 in San Francisco, CA!
view down the starboard side of NOAA Ship Bell M Shimada shows a wooden nameplate (reading Bell M Shimada) on a railing, the fast rescue boat mounted aftward, and the Golden Gate Bridge in the background.
Just after taking in lines and leaving Pier 30/32 on July 5
a group photo of the science team (including Lisa, in her Teacher at Sea shirt) aboard the ship, with the Golden Gate Bridge visible in the background
Science Team!
Back: Maddie, Ethan, Toby, Jamie, Beth
Front: Myself, Steve, Abi
a view of San Francisco buildings from behind a railing of NOAA Ship Bell M Shimada
San Francisco, CA Skyline
View over the aftdeck of NOAA Ship Bell M. Shimada from an upper deck, showing the wake of the ship in blue water through the A-frame that will deploy the nets
Heading out to the open sea of the Pacific Ocean

– – ⚓ – –

Did You Know?

an orange-gloved hand holds a hake (fish) up so that it faces the camera. We can see the another smaller hake hanging limply across its open mouth

– Hake can be cannibalistic!
– Some larger Hake we have collected have had a smaller Hake in their mouth, throat, or stomach!
– Their very sharp teeth often stick to our thick rubber gloves.

– – ⚓ – –

New Terms/Phrases:

“Salp: Barrel-shaped, planktonic tunicate in the family Salpidae. It moves by contracting, thereby pumping water through its gelatinous body.”

Wikipedia: “Salp”

“Myctophid: Lanternfish (or myctophids, from the Greek μυκτήρ myktḗr, “nose” and ophis, “serpent”) are small mesopelagic fish (…) Lanternfishes are aptly named after their conspicuous use of bioluminescence.”

Wikipedia: “Myctophid”

Simrad EK80: Multibeam Echo Sounder (MBES) transducer that emits sound waves from the hull of the vessel down to the sea floor. It allows scientists to observe and study returned sound wave signals that may suggest marine life is present.

Transect: Set and numbered longitudinal east-west lines NOAA Ship Bell M. Shimada navigates on while collecting acoustic data.

Leave a Reply

%d bloggers like this: