In my last post, we left off our acoustics 101 with the emergence of the first modern echosounders in the 1990s. Today, we will look at the current system aboard Oscar Dyson and learn how the science team can use their knowledge of acoustics to estimate fish populations. First, let’s look at the physical components that make up the EK80 echosounder system.
Each frequency requires its own transceiver. These six transceivers are the heart of the EK80 echosounder.
Transceiver – a combination of a transmitter and a receiver; in other words, it both produces an electrical pulse to be sent to the transducer and converts the backscattered signal into usable data a computer can understand. You can think of the transceiver as the electronic brain that manages all of the signal inputs and outputs.
Transducer – Just like you might plug a microphone into your laptop to record audio, each transceiver needs a transducer to first convert the electrical pulse into an acoustic pulse that is transmitted into the water, and to measure the acoustic backscatter that returns. You can actually see the transducers in the photo of the centerboard below. The transceivers measure frequencies ranging from 18 kHz (those really annoying mosquito ringtones that only young people can hear are around 18 kHz) to 330 kHz.
A) The red circles on the bottom of the centerboard are the faces of the transducers. These sensitive instruments are mounted at the lowest point of the ship to isolate them from the vessel’s noisy hull. (Photo credit: NOAA)
B) The acoustic centerboard protrudes well below the noisy hull-water interface.(Image: Annotation of illustration by The Scow.)
The Echogram
Once the transceivers process the acoustic backscatter, the data is displayed on a screen for interpretation.
There’s quite a lot going on here! Let’s break it down into smaller pieces so we can learn to look at the data like a scientist.Each of the six frequencies appears as a vertical section that scrolls from right to left as the vessel moves. The top of each plot represents the ocean surface, and the thick red layer near the bottom shows the seafloor. The space in between lets us look at what is below the ship! Weak backscatter appears blue; stronger backscatter appears yellow and even red.
Our old friend munge is making an appearance in this echogram! It is the heavy backscatter layer just beneath the surface that is strongest at 18 kHz. Lower in the water column, we see that most backscatter occurs at higher frequencies, with only sparse backscatter in the lower-frequency plots. Backscatter that is observed only at higher frequencies indicates smaller organisms, such as krill or copepods. Backscatter that appears across all frequencies is likely generated by fish.
As you spend more time looking at this scrolling echogram, you can begin to recognize patterns and draw reasonable inferences. Below are some examples of the variety you can see in just a few hours in the cave.
Younger pollock can gather in schools 20-40 meters tall that appear as very thin red ellipses.You can clearly see occasional reflectors on the 18 & 38 kHz channels; these may well correspond to adult fish. The only way to be certain is to trawl in an area that looks like this and see what the net brings up!We know that large fish like pollock return a relatively even acoustic signal across every channel that we look at; there do not appear to be any significant pelagic fish present in this echogram.
Now that we can read echograms, we are ready to call for our first trawl! Come back next time to see what we data we can scoop up in “The Anatomy of a Midwater Trawl”.
Personal Log
Things aboard Oscar Dyson have settled into a routine. We travel along acoustic transects during daylight hours, stopping 2-3 times a day to do a midwater trawl. Routine doesn’t mean boring, though! Maintaining a ship of this size and complexity is more than enough to keep everyone busy. The checklist for this leg included checking on the smaller craft that service and support Oscar Dyson on her mission. Conditions cleared on 06/29, and the Peggy D, the workboat that lives on the starboard hero deck, was given a thorough check and taken for a 30-minute voyage.
Peggy D secured to the aft hero deck of Oscar Dyson. ENG Connor Rauch and ENG Chelsea Gostomski on the aft deck of Peggy D.LCDR LeeAnn Keener and I enjoying the scenery.Bosun Alex Steele instructs me in the safe operation of Peggy D.
Safety drills and practice are a part of the routine as well. ENGR Connor Rauch practices recovery during a man-overboard drill on Peggy D. In the case of an actual man overboard, the smaller vessels are used for recovery, as they can respond much more nimbly and are far safer in close quarters with a swimmer.
Wildlife
This smooth lumpsucker (Aptocyclus ventricosus) is just as surprised to see me as I am to see him.Lumpsuckers have a unique feature: a ventral suction disk that allows them to firmly attach themselves to rocks in rough conditions.
So, we’ve taken a chilly dive into the why behind the focus on the pollock. Today, I will take you into “The Cave,” where we can learn how scientists use sound to locate and count pollock. On the port side of the main deck sits a dark, windowless room lit only by the dozen or so monitors adorning its aft wall. A gentle, constant humming fills the room from racks and racks of electronics, servers, and support equipment that dominate the center of this space. While the OOD on the bridge steers this vessel, “The Cave” calls the scientific shots by determining the ship’s course as well as the timing and location of all science operations.
Abigail McCarthy and Mike Levine discuss plans for the day shift. Time at sea is precious; this vessel operates 24/7 in all conditions. For the past two days, a very quiet, fishless northern extension has limited opportunities. But remember, even a null result is a result!
Acoustics 101
Since the early 20th century, scientists have used the unique ability of sound waves to transmit very efficiently through water for remote sensing. “Pings” of acoustic energy are generated by a transmitter, and then the backscatter (or reflected sound) is detected by a receiver. Early pioneers used sonar to better understand the physical geography of ocean basins in a process called bathymetry.
USS Stewart first tested an early form of echosounder in 1922 as part of preparations for the installation of the Transatlantic cable.
Not long after the first echosounders made their way aboard ships, scientists realized that as the quality of the instrument increased, they could measure the backscatter (or reflected sound) off of other objects besides the seafloor. Large backscattering layers far above the seafloor were targeted by fishing vessels using the new technology, demonstrating the effectiveness of echosounders at locating marine organisms throughout the water column.
Early innovators in Norway and England reported success in using echosounders to detect large schools of fish and began actively monitoring their behavior (Balls, 1948).
The following decades of acoustic research relied on analog, single-beam systems, which were often towed behind or below a vessel and recorded a narrow swath directly below the ship onto a paper echogram.
A 3d porcelain rendering of this now-famous echogram (the recorded chart of an echosounder) from the Shelikof Straight adorns the entry to the NOAA Alaska Fisheries Science Center in Seattle. The strong red and yellow reflections that sweep gently across the bottom represent the strong backscatter from the seafloor, and the large red cloud represents a large school of pollock.
The 1990’s welcomed a new era in echosounder technology with the release of the SIMRAD EK-500. This landmark digital echosounder combined multi-frequency operation with improved data processing and integration tools, enabling much better estimates of fish population density and biomass.
Larger acoustic targets, such as the swim bladder of a large fish, produce strong backscatter at relatively low frequencies, whereas smaller organisms, such as krill and copepods, reflect sound only at much higher frequencies. Multi-frequency echo sounder measurements allow scientists to discriminate between acoustic targets of different sizes and target strengths and more accurately estimate the biomass of individual organisms as they scroll across the screen.
Next time, we will look at the echograms produced aboard Oscar Dyson and receive a crash course in interpretation from the Cave!
Personal Log
Work hard, play hard is an unofficial motto aboard Oscar Dyson. The officers, crew, and science team are keeping a fierce eye on the World Cup when off duty (Colombia’s goal call-back was a travesty!!).
The “Inaugural Collin McMillan Memorial Biannual Oscar Dyson Amateur Cribbage Tournament” is underway; stay tuned for updates and potential video coverage of the championship match!The future gyotaku model, Northern rock sole (Lepidopsetta polyxystra), posing for a picture before her big debut.Gyotaku is the traditional Japanese art of collecting fish prints. Engineer Victoria Southwick, ENS Josh Bennett, and Lt. Jesse Pierce captured the print of a Northern rock sole (Lepidopsetta polyxystra) brought up on haul 71, 06/28/26.
Wildlife sightings
A Short-tailed albatross (Phoebastria albatrus) follows us during trawling operations, hoping for a fishy treat. This threatened marine bird is a tale of cautious conservation success. Their population in the 1950s dwindled to as low as 25 individuals. Today, roughly 4,200 individuals are known to exist.
Fun Fact
In the Cave, it is not uncommon for the shallow layer to be filled with a mix of non-fish backscatter. Everyone has their pet theories as to what may be the source of these shallow acoustic targets (we know they aren’t fish), but they have all agreed to call it by one name… munge. Below is my artist’s interpretation of Munge as a heavy metal album.
MUNGE album cover
Sources
Balls, R. 1948. Herring fishing with the echometer. Journal du Conseil International pour l’Exploration de la Mer, 15: 193–206.
Korneliussen, R. J. (2018). Acoustic target classification.
Benoit-Bird, K. J., & Lawson, G. L. (2016). Ecological insights from pelagic habitats acquired using active acoustic techniques. Annual review of marine science, 8, 463-490.
Mordy, C. W., Bond, N. A., Cokelet, E. D., Deary, A., Lemagie, E., Proctor, P., … & Wisegarver, E. (2023). Progress of fisheries-oceanography coordinated investigations in the Gulf of Alaska and Aleutian Passes. Oceanography, 36(2/3), 94-100.
De Robertis, A., McKelvey, D. R., & Ressler, P. H. (2010). Development and application of an empirical multifrequency method for backscatter classification. Canadian Journal of Fisheries and Aquatic Sciences, 67(9), 1459-1474.
Simmonds, J., & MacLennan, D. N. (2008). Fisheries acoustics: theory and practice. John Wiley & Sons.
Holliday, D. V., & Pieper, R. E. (1995). Bioacoustical oceanography at high frequencies. ICES Journal of marine Science, 52(3-4), 279-296.
NOAA Teacher at Sea Nick Lee Aboard NOAA Ship Oscar Dyson June 29 – July 20, 2024
Mission: Pollock Acoustic-Trawl Survey
Geographic Area of Cruise: Eastern Bering Sea
Date: July 6, 2024
Weather Data from the Bridge:
Latitude: 61° 15.0 N
Longitude: 174° 56.8 W
Wind Speed: 13 knots
Air Temperature: 5.3° Celsius (41.5° F)
Science and Technology Log:
On NOAA Ship Oscar Dyson, the science party’s mission is to understand the population of walleye pollock in the Eastern Bering Sea. To collect data, scientists rely on two main tools: acoustics and targeted trawling. Before any trawling can happen, scientists must first locate fish using acoustics, so I’ll be focusing on acoustics in this blog post – stay tuned for a post on trawling next time!
Scientists use two kinds of acoustics: active and passive. Many of my students are familiar with how bats use echolocation to navigate in the dark – active acoustics relies on the same principle. First, the echosounder on the ship emits a pulse of sound, or ping. This sound travels through the water and bounces off of objects that have different densities than water (such as fish, krill, or the ocean floor). The echosounder then “listens” for and records these echoes, also known as backscatter. Passive acoustics work similarly, except the echo sounder only listens for sound and doesn’t emit any itself.
The echosounder emits a pulse of sound, which gets reflected by objects of different densities, like pollock.Image Credit: Wieczorek, Schadeberg, Reid (2021) “How do Scientists Use Sound to Count Fish in The Deep Sea?” Frontiers for Young Minds. https://kids.frontiersin.org/articles/10.3389/frym.2021.598169
The greater the distance between the echo sounder and the object reflecting the pulse, the greater the amount of time between when the signal was emitted and backscatter. Based on this time, echosounder can determine the depth of the object producing the backscatter. This information is represented visually in an echogram:
Screenshot of an echogram. The space between vertical grid lines represents 100 pings, and the space between horizontal grid lines represents 10 meters of depth.
The echogram shows depth on the y-axis and time on the x-axis. The intensity of backscatter is color-coded, where more intense backscatter is represented with red and brown, and less intense backscatter is represented with blue and green. The vertical grid lines represent all the backscatter from one ping, and the space between lines represent 100 pings.
On the cruise, pings are typically emitted at a rate of 1 Hz, or once every second. With every new ping, the echo sounder adds data to the right end of the echogram. This means that the horizontal grid lines represent the backscatter at one depth over time (or distance, if the ship is traveling at a constant speed).
At least one scientist monitors the backscatter throughout the duration of the transect. During the first day, the echogram was blank except for some lower-intensity backscatter near the surface and high-intensity reflection from the ocean floor. Because the mission of this cruise is to survey pollock, which tend to live at greater depths, we don’t pay much attention to the backscatter near the surface which is comprised of smaller organisms like krill. However, when scientists notice backscatter consistent with scattering from pollock, they may trawl to collect a sample for more detailed biological information.
Echograms from two different locations showing low-intensity backscatter (left) and high-intensity backscatter (right). When the backscatter looks as it does on the right, the science team may decide to fish in that area.
As we traveled along the first transect line, there was very little backscatter that the science team thought represented pollock. Our CTD (conductivity, temperature, depth) measurements also showed that the water temperature was cold, right around freezing. This may suggest that we were traveling through the Bering Sea cold pool, a mass of cold water that forms from melting ice. This water tends to be too cold for pollock and other fishes, however, other animals, such as snow crabs, can still survive the lower temperatures. Fish like cod prey on snow crab, so the cold pool offers these crab an important refuge from predators. Read more about the importance of the cold pool for crab here!
Historical bottom temperature showing cold pool in blue / purple (Image Credit: NOAA Fisheries)
Personal Log:
The start of the cruise has been busy learning new faces, maritime practices, and scientific terms. However, in the past few days, with the help of meclizine (seasickness medication), I’ve begun to feel more settled and like I have some sense of routine.
When I’m on shift, I bounce around between a few different places. The science team tends to be in the acoustics lab, where we monitor backscatter and make decisions on when to fish.
Acoustics lab, also called “the cave” for its lack of windows.
Once the scientists decide to fish, we first go up to the bridge, where NOAA officers control the direction and speed of the ship. The bridge has windows on all sides, so we’re able to make sure there are no marine mammals before putting the net in the water.
From the bridge, you can also see the trawl deck, where the deck crew works in collaboration with NOAA officers to put the net in the water. Once the fish are caught and hauled back to the ship, the science team processes the catch in the fish lab.
The bridge and its view of the trawl deck.
When we’re not working, we’ll grab food from the galley / mess deck. The stewards on the ship serve three meals a day, but since I’m on the night shift, I often heat up leftovers or take advantage of the wide selection of snacks they leave out. There’s also a lounge, two gyms, and places to do laundry while at sea!
The galley, where food is available 24 hours a day!
Did you know?
NOAA Ship Oscar Dyson has six onboard laboratories including a wet lab, dry lab, electronics lab, bio lab, acoustics lab, and hydrographics lab. Read more about the ship here!
Mission: Acoustic Trawl Survey (Leg 3 of 3) Geographic Area of Cruise: Pacific Ocean/ Gulf of Alaska Date: Sunday, August 13, 2023
Weather Data Lat 59.12 N, Lon 150.11 W Sky condition: Partly Cloudy Wind Speed: 13 knots Wind Direction: 330° Air Temp: 14 °C
Science and Technology blog
The ocean is a really big place. We have really only mapped about 5% of the ocean bottom. How do we manage fisheries if we have to count fish in an area that is overwhelmingly large? This is where the genius of acoustics and trawl sampling complement each other. The scientists aboardNOAA Ship Oscar Dyson use the echo sounders to find fish or other animals lurking in the ocean and then they can extrapolate and upscale that data to a much larger area which is covered by their transects.
Wait! That is a lot of information using language that folks don’t really use at the dinner table. Could you please explain this in more basic terms? You bet, as a matter of fact in the last couple of days I have been swimming in a sea of new vocabulary, talking to really smart people and trying to keep up with the conversation that it almost makes my head explode. Don’t worry, I am safe. But it’s really impressive how scientists have developed ways to accurately know fish and marine organism populations in the ocean with out having to sample all of it.
Acoustics
Acoustics uses the echo-sounders a lot like a fish finder, but the ones on NOAA Ship Oscar Dyson are much more capable than the type you would find on your boat. The echo-sounders are attached to the bottom of a lowered centerboard—essentially a large keel—in the center of the boat, and they measure five different frequencies with different wavelengths.
View of the 5 different frequencies measured by the echosounders, one in each frame. The darker marks on the screen could be fish, jellyfish, krill or other marine organisms, this is referred to as “backscatter.” The red circles show the different frequencies used to measure the backscatter.
So, if we can see the fish using acoustics, why do scientists need to sample using a trawl net? As you can see above, the marks in the backscatter can show the depth and the approximate shape of objects, but there is not enough detail to tell exactly what kind of organism is present. Most of the scientists on board have a pretty good idea what kind of fish or organisms are present, but the most definitive way to know is to take a trawl sample.
Trawl Sampling
The trawl net as seen in the picture below is being set off the aft deck.
The part that is in the air is called the codend. That is the section of the net where the specimens are ultimately collected.
The trawl is a about 172 meters long and it stored on these rollers on the back deck.
When the trawl is deployed to the depth that the scientists want to sample, the net will funnel fish and other organisms into it. This is called flying the net.
The screen above diagrams three different views of the net as it is pulled through the water. You can see that the trawl net was not directly behind the boat and went to a depth of 21.5 m.
In this image you can see the net and how far back it trails behind the Oscar Dyson.
I just have to include one more view of the trawl net from the bridge as it is pulled behind the boat.
This image was taken when the crew was bringing the net back into the boat, so the depth is shallower.
The next image shows the path that the net was pulled through the water.
The acoustics show the backscatter which the scientists make the trawl target. The next step is to process what is captured in the codend of the trawl and see exactly what is present.
Because the trawl is dragged through the water, it catches different organisms at different times. The scientists want to know when the different organisms were caught so they have cleverly attached a camera to the side of the net. Through the camera they can see which type of fish came into the trawl. Ultimately, this links the kind of acoustic backscatter viewed in the echograms recorded during the trawl to exactly the type of organism caught by the trawl.
The camtrawl: a camera that records the type of fish entering the net and when they enter.
Below is a picture of some fish as they enter the trawl net and move towards the codend.
The camera is looking across the net as the fish move past. The fish in the picture are pollock, the type of fish we are looking for on this leg of the cruise.
Transect Lines
So how do scientists take this information and extrapolate the data to a broader area? While the Oscar Dyson is out at sea they run transect lines while recording acoustic data. Transect lines are specific paths in the ocean. The picture below shows the transect lines that we plan to do and have done on this leg of the cruise.
The red lines are the transects we have done and the blue lines are the transects scientists plan to do in the remainder of this leg of the cruise. If you look closely there are pictures of fish symbols on the transect lines where the ship has made trawl samples.
Using the acoustic data that the echo-sounders provide and verifying the types of fish and other marine organisms through the trawl sampling allows the scientists to predict, with a high level of certainty, the amount and types of marine organisms that are present along the transect lines that were not trawl-sampled. Thus saving the taxpayers money, and allowing fisheries managers to use good data, keeping the fishery viable, and allowing commercial fishing boats to have reasonable catch limits.
Scientist in the Spotlight
Honestly it takes a team to make all of this happen. But, half of our team is sleeping at the moment, I have the night shift from 4pm to 4am, so I am going to introduce one fabulous expert in acoustics and fisheries:
Abigail McCarthy in the Acoustics Lab
Abigail McCarthy has been working for MACE: Midwater Assessment and Conservation Engineering Program since 2007. She received her undergraduate degree in Biology from Wellesley College and then obtained a Masters in Fisheries from Oregon State University.
For fun, she surfs and enjoys long-distance prone paddle board races. She has recently found a new love with fly fishing.
Aboard the Ship Oscar Dyson, she is working as a specialist helping to run the acoustics lab.
I asked Abigail what she thought of about her educational experience? She immediately said, “I love learning! High school and college were both a lot of fun.”
What would be a good suggestion for a young aspiring high school student pursuing a degree related to ocean studies or science in general?
Her response was great: “Being curious and working hard is more important than being brilliant. Persistence and determination will get you where you want to be in the future.” Finally, “Learn to code! Become familiar with programing languages like Python and R.”
Hopefully, I answered your burning questions about the use of acoustic trawl sampling, and surveys. Yet, there is so much more to learn. Why not take a trip yourself? Check NOAA’s website out and just apply.
Mission: Pacific hake (Merluccius productus) Survey (Leg 3 of 5) Geographic Area of Cruise: Pacific Ocean off the Northern California Coast working north back toward coastal waters off Oregon. Date: July 29, 2023
Weather Data from the Bridge
Sunrise 0616 | Sunset 2037 Current Time: 1500 (3pm Pacific Daylight Time) Lat 41 06.7 N, Lon 124 37.6 W Visibility: 10 nm (nautical miles) Sky condition: A few clouds Wind Speed: 13 knots Wind Direction: 334° Barometer: 1019.7 mb Sea Wave height: 2-3 ft | Swell: 330°, 3-4 ft Sea temp: 14.1°C | Air Temp: 17.6°C
Science and Technology Log
Hake are not the only thing being studied during this mission. In the Chemistry Lab, there are a variety of ongoing tests. Every few transects, seawater is collected and tested for Harmful Algal Bloom (HABs). A vacuum pump sucks the sample through a 0.45um filter, which is then removed and placed into a test tube for microscopic study. The Southern California coast is currently dealing with a bloom toxic to animals. Scientists want to know if the bloom is drifting north. Blooms are a natural phenomenon, but human activity cannot be ruled out from having an impact.
HAB test in the Chem Lab
A seawater pump connects to a software program that allows you to see images of phytoplankton being photographed in real time as they are sucked past the camera. Phytoplankton forms the base of the aquatic food web. They provide food for huge whales, small fish, invertebrates, and zooplankton. Plankton makes up 95% of life in the ocean, they generate half of our oxygen and absorb carbon. A sudden removal of phytoplankton would result in a collapse of aquatic ecosystems, and would accelerate climate change further.
The phytoplankton images are taken using a robotic microscope automating identification. The name of the artificial intelligence is Imaging Flow CytoBot (IFCB). Flow cytometry uses lasers to create both scattered and fluorescent light signals. These signals are read by photosensitive diodes and tubes, and then those signals can be converted electronically to be read by a computer. The data gathered enables ecosystem modeling, and can act as an early warning to toxic blooms.
Image of phytoplankton captured by the IFCBThe Chem Lab’s seawater pump.
Career feature
Chief Scientist, Steve de Blois, on the bridge during a trawl.
Steve de Blois, Chief Scientist
Steve’s favorite thing about his job is getting out in nature, seeing, and photographing marine mammals. Even though the hours are long, the commute is short when you’re at sea! His educational background includes an undergraduate degree in biology from the University of Michigan, Ann Arbor; and a Master’s from Humboldt State University (now called Cal Poly Humboldt) in marine mammals. It was tough finding work after graduate school since working with marine mammals generally holds more appeal than fish, and thus more people are competing for a finite number of jobs. Once Steve secured a job at one of NOAA’s regional offices, he found out about other opportunities and ended up on a walleye pollock acoustic trawl survey in Alaska. This is where he had one of those National Geographic moments where the scenery is so stunning it touches you at your core. He has been with NOAA since 1990—the same year the Teacher at Sea Program began.
Steve’s advice for young people interested in ocean-related careers is to focus on getting your education. He states that getting a graduate degree (PhD and/or Master’s) will make you more competitive in the scientific community. However, he also advises, “get experience.” Nothing can compare to first-hand experience and there are many opportunities for volunteering in the field, in marine labs, and on ships.
During his leisure time, Steve prefers to fly his home-built plane (A Zenith CH 650), go scuba diving, and enjoy photography. When it comes to reading he prefers nonfiction. He has German heritage on his mother’s side and shared some personal history of family members surviving both World War One and World War Two. This part of his family tree has increased his interest in true tales about World War Two German fighter pilots. In his youth, he absorbed science fiction novels by Arthur C. Clarke and recalls enjoying Dune, by Frank Herbert. Recently, he read Rachel Carson’s classic The Sea Around Us and was impressed by its lyrical prose. Steve has patiently taught me about how to detect hake sign on an echogram. Acoustically speaking, hake have a unique characteristic. The visualized pings usually show hake near the slope of the continental shelf, and they appear as a diffuse cloud of colored pixels, or as a “hakey snakey” line gently curving up and down. A calculation called NASC, Nautical Area Scattering Coefficient, makes an estimate of individuals in that defined area drawn by scientists.
The acoustic echogram has a color key representing the strength of return on what the sound waves bounce off. The color scale looks something like you’d see in an art room class teaching color theory. The weakest return is signified by a pale grey to dark, then a light blue shade into dark, the blue turns teal as it morphs into greens, then when yellow appears the scientists start getting excited. After yellow is orange, pink, then many shades of red ending with a deep magenta. The ocean floor appears as deep magenta. On Leg 2 the Shimada saw several very dense balls of fish; these fish are likely herring or sardines, species smaller than hake. The acoustic return from these very dense balls of fish is extremely high—their color in the acoustic software is easily deep red, almost brown.
The thicker reddish brown line you see is the continental shelf/ocean floor. The greenish-yellow cloud represents an acoustic signature historically found to be hake. The thin red lines in the echograms on the right represent the head rope from imaging by the SBE (Sea-Bird Electronics) camera, aka “the turtle.”
Taxonomy of Sights
Day 5. Bycatch highlights: Intact squid, Chinook salmon (also known as King salmon), and excited albatross following a record haul.
Day 6. More salmon, two kinds of rockfish, a Thetys vagina salp (more on the awkward name here), and a marine hatchetfish so small my camera found it difficult to focus on. Ethan Beyer, Wet Lab Lead, shared a trick to determine the difference between a yellowtail rockfish and widow rockfish (they look similar). The difference? Widow rockfish have a “widdle” mouth. Meaning, the mouth is smaller than the yellowtail’s (ha, ha). The two types of rockfish we caught were the widow and the shortbelly (Ethan says they make great tacos!) Speaking of tacos, the widow rockfish are due to make an appearance on our mess deck menu soon.
Day 7. Not much…
You Might Be Wondering…
What is the furthest you’ve been from shore? To date (July 28th), an extension of transect 39 took us a total of 62 nautical miles from shore, which beat our extension record on Wednesday, July 26th. Leg 3 has extended more transects than Leg 2. The reason for extending a transect is to go where the fish sign is. The NOAA Fisheries protocol is to discover what the western extent is for schools of hake on that transect. So, they wait for at least one mile without seeing hake before ending the transect.
What is the deepest trawl you’ve made? So far on Leg 3 we’ve gone 400 meters (about a quarter of a mile) to reach a target depth. Simply put, target depth is where the fish are estimated to be.
Floating Facts
Vocabulary
Bycatch – Some dictionaries call them unwanted creatures caught in the pursuit of a different species. NOAA however, thinks it worthwhile to catalog the biomass of these tag-alongs.
Biomass – The total weight (sometimes quantity) of a species in a given area or given volume.
One of these things is not like the others Tow, Haul, and Trawl are used interchangeably in reference to fishing. “Catch” is what we’ve caught in the net.
Survey Permits
You know how you ask permission at school and at home to do a thing? The hake survey requires a number of permits to conduct its research. A permit is an official document saying you have asked for and been granted permission.
NOAA’s Western Region office issues “Authorizations and Permits for Protected Species.” The protected species are salmon and eulachon, a thin silvery thing about the size of a herring. The permit dictates what you can (measure and weigh it) and can’t do (eat it) with protected species.
A state’s jurisdiction over ocean waters only extends three nautical miles from shore. The Oregon Department of Fish and Wildlife wants to know the number of all species caught off its coast. California’s Department of Fish and Wildlife issues a Memorandum of Understanding (MOU) along with a permit. The MOU calls out particular species they are interested in: longfin smelt, coho and chinook salmon.
I should be frowning – we don’t intend to be pulling salmon out of the water. However, their appearance does contribute to data about the health of their populations.
While fishing rarely ever happens in Alaskan waters during the hake survey, the Department of Fish and Game issues a permit that is shared with Canadian colleagues who may pursue hake further north. Waters defined by NOAA’s National Marine Sanctuaries have their own monitoring system and permit issuance. The hake survey passes through three sanctuaries in California waters and one in Washington (the Olympic Coast). Finally, the West Coast Region of NMFS (National Marine Fisheries Service) issues a permit and requires a record of all species caught in U.S. waters, so a grand total of sorts for all states involved.
Personal Log
Thursday was a huge improvement over the icky Wednesday ride. We made two successful trawls, and two trawls on Friday. Wet Lab Lead, Ethan Beyer, commented during fish processing on Friday, “I feel like I’m the world’s foremost expert on the visual maturity of hake. I look at a lot of hake gonads.” This was memorable.
Saturday dawned with too much fishing line in the water to do anything so we waited until we moved past it before dipping the net in. We did squeeze in a catch before lunch, but it produced exactly one hake among the usual lanternfish and pyrosomes. Disappointing for the science crew.
Note: In an earlier post I referred to lanternfish as “lampfish,” which is incorrect. I’ve also been calling Dramamine “dopamine” for some reason. I’ll blame it on the mild disorientation that is caused by floating around on the ocean.
My Daily Routine
I wake around 0600 and sometimes make it up to the flying bridge to see the sunrise, but usually go up regardless before breakfast to view the morning light. I stop in at the acoustics lab to sit at my workstation, blog a bit, and see what hake sign there is on the echogram (software visualization of what lies beneath us). Breakfast is served at 0700, then I return to acoustics to stay up to date on when we’re going fishing.
When you hear, “Fishing, fishing, fishing,” on the radio you know it’s almost time for the marine mammal watch. Marine mammal watch happens on the bridge, and I continue watching for a while even after the watch ends. I’ll stay up there for most of the trawl until I hear, ”Doors at the surface.” (More on the stages of a trawl next time.)
Next, I’ll go to the “ready room” in the wet lab where boots and fishy rubber overalls are stored. Blog post three walked you through what we do in the Wet Lab once the catch has been dumped in the crate. Processing species takes us into lunch hour at 1100.
A second trawl after lunch, and assuming the catch is decent, processing will take us to dinner. I have down time after dinner, watch the evening light if the weather is amenable, then return to acoustics for more blog time. I’m in bed somewhere between 2030 and 2230.
While there is a general routine, no day is exactly alike. On Saturday I assisted Ethan with collecting sea water from a vertical net dipped by a crane to 100 meters. Scientists will look at the plankton, krill, and other small species to determine stratification and measure abundance.
Deck and Survey Crews work with Ethan to collect samples from the vertical net.Wet Lab Lead, Ethan Beyer, removing a weight on the vert net.Plankton floating at the top of a sample.
Librarian at Sea
“It is a curious situation that the sea, from which life first arose should now be threatened by the activities of one form of that life. But the sea, though changed in a sinister way, will continue to exist; the threat is rather to life itself.”― Rachel Carson, The Sea Around Us
The cover of Rachel Carson’s book, The Sea Around Us, appears on the wall of the dining room at Sylvia Beach Hotel where I stayed prior to the departure of leg three. Her poetic approach to scientific insight continues to inspire readers. The book I brought with me on the ship does something similar. In How Far the Light Reaches, author Sabrina Imbler blends personal memoir with profiles of ten sea creatures. Imbler attempts to keep metaphors and personal (human) parallels at a distance from the scientific integrity of species. Both titles are recommended reading.
How Far the Light Reaches: A Life in Ten Sea Creatures by Sabrina Imbler
The Sea Around Us by Rachel L. Carson
Hook, Line, and Thinker
When I was a kid, my Dad sometimes sang Gordon Lightfoot’s ‘Ode to Big Blue’ as a lullaby before bed. It’s one of the only songs I know all the lyrics to, although sometimes I scramble the verses up. I think it was my first exposure to the tension between commerce and the sustainability of natural resources. The sixth verse says,
Now the gray whale is run and the sperm is almost done The finbacks and the Greenland rights have all passed and gone They’ve been taken by the men for the money they could spend And the killing never ends it just goes on
Herein lies another ethical debate on balancing preservation, economics, and the needs and wants of Homo sapiens. The song celebrates the natural wonder of whales alongside the biting reality of human enterprise.
In April 2023 NOAA released a 2022 Status of Stocks report. Data displayed overfishing status of 490+ stocks managed by NOAA.
NOAA Fisheries assistant administrator, Janet Coit, said in the Status of Stocks news release, “Managing fisheries sustainably is an adaptive process, relying on sound science and innovation to conserve species and habitat, and meet the challenge of increasing our nation’s seafood supply in the face of climate change.” NOAA Fisheries priorities for fiscal year 2023 are full of words like: sustainability, resilience, mitigate, adapt, diversify, ensure equity, safeguard, propel recovery, conservation, protect, and restore. NOAA continuously strives to balance the scales between conservation and consumption.
What are the ethical concerns that should guide economics? Is it possible to view the ocean other than as a natural resource? Is that view in fact imperative to the sustainability of life on Earth?
A Bobbing Bibliography
If you keep your eye out for books, you will find them. Tucked away on the bridge is a shelf containing…
