otoliths – NOAA Teacher at Sea Blog

August 23, 2024August 27, 2024

Tonya Prentice: NOAA’s CTD and Carousel, August 20, 2024

NOAA Teacher at Sea

Tonya Prentice

Aboard NOAA Ship Henry B. Bigelow

August 8 – August 24, 2024

Mission: Northeast Ecosystem Monitoring Survey

Geographic Area of Cruise: Northwest Atlantic Ocean

Date: August 20, 2024

Weather Data from the Bridge
Latitude: 42.2212 º N
Longitude: 70.29659º W
Wind Speed: NW at 12 mph
Air Temperature: 19.8° Celsius (67.64° F)
Sea Temperature: 19.3 Celsius (66.74° F)

Science and Technology Log

Monitoring Ocean Parameters with NOAA’s CTD and Carousel Bottle Sampler

The CTD and Carousel Sampler are essential tools NOAA uses to monitor ocean conditions. “CTD” stands for Conductivity, Temperature, and Depth, the primary parameters this device measures. By running profiles of the water column from the surface to the bottom, the CTD helps us understand key ocean characteristics. The Carousel Sampler paired with the CTD allows collection of water samples at depth for laboratory analysis.

What Does the CTD Measure?

Conductivity: Helps determine the salinity of the water.
Temperature: Measures the thermal profile of the water column.
Depth: Tracks how deep the CTD is during data collection.

Together, these measurements give us a detailed profile of the water column, helping scientists monitor what we call “the Big Four” parameters.

Carousel: Collecting Water Samples

The CTD and Carousel is equipped with twelve Niskin bottles, which are used to collect discrete water samples from specific depths. The bottles are numbered 1-12, and are “fired” (closed) at different depths to capture water samples.

For example, bottle 1 might be fired near the bottom (a few meters above the seafloor), bottle 2 at 10 meters, bottle 3 at the determined chlorophyll maximum (C Max), and bottle 4 couple just below the surface. Multiple bottles are often fired at each depth to collect additional water. These samples provide critical data about the ocean’s chemical properties at various levels.

view of the carousel sampler resting on the deck of NOAA Ship Henry B Bigelow at night. A white cylindrical metal frame holds twelve gray cylindrical bottles in a round. The bottles have opened stoppers connected at the top and bottom. the CTD probe, at the center of the round, is not visible. Tonya has added yellow text boxes to label the following: carousel, Niskin bottles, top stopper, valves, bottom stopper. — CTD Carousel Bottle Sampler

Preparing the CTD Carousel Bottle Sampler

Before deployment, we ensure that all the stopper valves at the top and bottom of each Niskin bottle are closed. We also hook the wires at the top and bottom to prepare the bottles to open at the designated depths. Once the CTD is ready, it is carefully lowered into the water, beginning its descent through the water column.

Analyzing the Key Parameters

Once the water samples are retrieved, we focus on analyzing these key parameters:

Dissolved Inorganic Carbon (DIC)
pH
Total Alkalinity (TA)
Nutrients
Chlorophyll

view of a large scientific instrument, a cylindrical metal frame containing a round of tall dark gray sample bottles, suspended over the rail of a ship. The sky and the water are both a dark blue, fading into one another at the horizon. — Lowering the CTD into the water.

photo of a computer monitor displaying a graph; the graph itself is not really readable — Lowering the CTD into the water.

Storing the Samples

After processing, the nutrient and chlorophyll samples are stored in a freezer kept at -80°C (-112°F) to preserve them for further analysis. Mercuric chloride is added to the DIC, pH, and TA samples to preserve them until they are measured in the laboratory. These samples provide invaluable insights into ocean health. The DIC, TA and pH samples help us monitor the effects effects of ocean acidification— which occurs when carbon dioxide dissolves into the ocean. The chlorophyll samples measure the amount of phytoplankton living in the water. Like plants on land, microscopic phytoplankton carry out photosynthesis, produce oxygen, and are at the base of the marine food web.

Understanding these parameters allows us to monitor the ocean’s health and better predict how it may change in the future. For more information on ocean acidification, check out this resource: NOAA Ocean Acidification.

By closely monitoring DIC, TA and pH we can track important changes in our oceans, providing critical data for research and conservation efforts.

Personal Log

Life on a 12-Hour Work Shift at Sea

Working a 12-hour shift at sea might sound intense, but there’s often some downtime between stations and even a few hours after the work is done. The time you get can vary depending on how far apart each station is. Sometimes it’s just enough to process samples before heading to the next station, while other times you have several hours to relax and recharge.

So, how do you spend that free time on a ship? There’s no shortage of options. You could enjoy a movie in the lounge area, dive into a good book, play a board or card game with other crew members, or head to the flying deck to spot seabirds and marine life, or simply take in the stunning ocean views. Another interesting way to pass the time is visiting the bridge, where you can see how the ship is navigated, maneuvered, and commanded.

Let’s not forget “Activities and Crafts with Katy,” which can bring a whole new adventure to your day. Today, this included visiting the lab and looking at the different species of marine organisms that have been collected, such as stingray barbs, dogfish, and scallop shells. Katy then showed us how to make our own Acadian Redfish otolith (ear bone) earrings. “Scientists use the ear stones (bones) as a way to age the fish. Also called otoliths, they are bones found right behind the skulls of bony fishes.” (Smithsonian)

The balance of work and downtime can make those long shifts much more manageable and even enjoyable, offering moments to connect with colleagues and the environment around you in a way that few people get to experience.

view of two rows of large brown comfy-looking recliners facing a tv screen mounted on the wall above cabinets. there is a bookcase off to one side. — The Lounge area.

the flying deck - the uppermost deck on the ship - is bisected by the ship's yellow mast. a tall metal frame appears to be shade structure but may serve additional purposes. There are picnic benches and beach lounge chairs. — The Lounge area.

Did You Know?

“One atmosphere is equal to the weight of the earth’s atmosphere at sea level, about 14.6 pounds per square inch” (NOAA Water Pressures at Ocean Depths). Beneath the ocean’s surface, water pressure increases by approximately one atmosphere for every 10 meters of depth.

To illustrate just how intense this pressure can be, we conducted a simple yet fascinating experiment. We decorated 16 ounce styrofoam cups with artwork, then placed them in a mesh bag attached to the CTD Carousel Sampler. The CTD , along with the cups, was submerged to a depth of about 500 meters (1640.42 feet), where the pressure equals roughly 725 pounds per square inch (psi). We repeated this process by submerging the cups to 200 meters (656.17 feet), which equals about 291.18 psi.

As the cups descended into the depths, the increasing water pressure caused them to shrink dramatically because the air inside the cups was compressed. This simple experiment vividly demonstrates how powerful the forces at play beneath the ocean’s surface can be.

three styrofoam cups in a row on a table or desk surface. the leftmost cup is the standard size, undecorated. The middle cup is 30-40% smaller. It's colored with marker to be a flower scene, with "2024" written around the top rim. The rightmost cup is the smallest, probably less than half the size of the original. It says Go Wildcats, August 2024, Henry B Bigelow. — This is a normal size ounce styrofoam cup (left side). Here is the cup after it was submerged 200 m below the ocean surface (middle). The last cup was submerged 500 m and then again at 200 m (right side).

June 21, 2023June 21, 2023

Laura Guertin: Collecting Data: Icthysticks and Otoliths, June 21, 2023

NOAA Teacher at Sea

Laura Guertin

Aboard NOAA Ship Oscar Dyson

June 10 – June 22, 2023

Mission: 2023 Summer Acoustic-Trawl Survey of Walleye Pollock in the Gulf of Alaska

Geographic Area of Cruise: Islands of Four Mountains area, to Shumagin Islands area
Location (10:45AM (Alaska Time), June 21): 55^o 29.7525′ N, 156^o 44.7276′ W

Data from 10:45AM (Alaska Time), June 21, 2023
Air Temperature: 8.4 ^oC
Water Temperature (mid-hull): 8.2^oC
Wind Speed: 8 knots
Wind Direction: 20 degrees
Course Over Ground (COG): 76 degrees
Speed Over Ground (SOG): 11 knots

Date: June 21, 2023

Once the echo sounder has shown us the position of an aggregation of Alaska walleye pollock (we hope they are pollock and not some other fish species), we lower the trawl net and see what we can catch. This is where the trawl sonar and CamTrawl (see previous blog post) come in handy to give us an idea of what is going into the net. It’s an amazing coordination of effort between the acoustics lab (who decides where to trawl), the bridge for navigation, and the deck crew for setting/retrieving the haul.

We aim for trawling at the mid-water level, where the pollock are typically found. Pacific Ocean perch (POP, or rockfish) can also be found in the mid-water level in the Gulf of Alaska, especially just off the shelf break. Bottom trawls can yield pollock and other fish (e.g., POP and other rockfish species, various species of flatfish).

Once the trawl net has been brought back on board, the catch is emptied into a bin called a table. There is a door on the side of the table that opens into the fish lab. Once the table door opens, the fish spill into the laboratory where they travel down a conveyor belt for the initial sorting. Our target species is the pollock. We weigh everything that ends up onto the sorting table, either in bulk (by species) or individually.

Pollock moving along the sorting belt
Pile of Pacific Ocean perch (rockfish) after being hauled on the ship
Small squid that fell out of the trawl net on deck.

A subset of around 250 pollock are set aside to collect length data. The length of these of each individual pollock are measured on an Ichthystick. This is another invention by Rick Towler and Kresimir Williams (remember the CamTrawl? (see previous blog post)). As described in their article An inexpensive millimeter-accuracy electronic length measuring board, these NOAA scientists describe using magnetic measuring technology that, to millimeter resolution, takes a measurement when you placed a magnet on a sensor that runs the length of the board. For our pollock measurements, we were looking to record the fork length, and a quick placement of the red magnet along the fish tail sends the data to a computer program called CLAMS (Catch Logger for Acoustic Midwater Surveys).

Bins of pollock waiting to be measured on the Ichthystick
Ichthystick logo with a pollock sketch
Computer end of Ichthystick, which digitally shows the value of fish length and is written to CLAMS
Sketch showing what is measured for the fork length of a fish. From Corvallis Forestry Research Community.
Pollock lying on Ichthystick getting its fork length being measured
Two scientists measuring pollock fork length on Ichthystick

Another subset of approximately 50 pollock are set aside for additional data collection on individual specimens – length, weight, sex, maturity, and age. Otoliths (e.g., ear bones) are removed, and sometimes organs are removed and measured (ovaries for maturity development analyses, liver).

a black and white image showing pairs of otoliths from different fish species. Each otolith is white and gray in contrast with the solid black background; lighting reveals the ringed growth pattern — Otolith pairs (two per individual fish) from an assortment of Bering Sea fish species. Walleye pollock is located in the top left. Note: otolith sizes are not on a relative scale. Photo: NOAA Fisheries.

What are otoliths, and why remove them? Otoliths are ear stones, or ear bones, found in fish. To give you an idea of why we remove ear bones, let’s start by thinking about trees and corals… trees grow a new ring on their structure each year, and corals have differences in their skeletal density between the seasons (both trees and corals are also used to reconstruct past climate conditions (proxy data for paleoclimatology)). By counting the rings on trees and coral, we can calculate the age of that specimen. It turns out that fish also have a way to record their annual growth – and it occurs in their ear through Fish Otolith Chronologies.

Scientists are very interested in studying otoliths. When otolith data are combined with data on fish size, scientists are able to determine the growth rates of fish, which then combined with the survey work, helps inform annual fish stock assessment reports. We don’t do any of the otolith analyses on the ship, but we do collect the samples with a detailed label and all the corresponding data (fish length, sex, weight, location) that is sent back to the NOAA Fisheries Alaska Fisheries Science Center for analyses and entered into their Fish Otolith Collection Database.

Rockfish otoliths
Zoom of rockfish otoliths
Otoliths still inside a pollock
Placing an otolith cleaned in freshwater into a vial for storage and shipment for analysis

Did you know… More than 30,000 otoliths are read annually by NOAA Fisheries Alaska Fisheries Science Center scientists. So far, the Science Center has collected more than 1.1 million fish otoliths for ageing. (from NOAA Fisheries)

To learn more about the fascinating studies of otoliths and what NOAA Fisheries is doing, check out these websites:

NOAA Fisheries Age and Growth – NOAA Fisheries scientists assess the age and growth rates of fish species and populations to better monitor, assess, and manage stocks. There is also a separate site for Age and Growth Research in Alaska.

NOAA Fisheries Age and Growth Homework: Determining How Old Fish Are

NOAA Fisheries Near-Infrared Technology Identifies Fish Species From Otoliths – NOAA Fisheries scientists are developing ways to use near-infrared spectroscopy (NIRS) analysis of otoliths (fish ear stones) to provide accurate information for sustainable fisheries management faster.

If you are really curious to explore some fish otolith data, check out the Alaska Age And Growth Data Map, an interactive map displays collected specimen information from recent age and growth studies from Alaska Fisheries Science Center.

Screenshot from the Alaska Age and Growth Data Map website. On the left is a map of Alaska with lots of orange, blue, and green circles marking sampling locations. To the right are two graphs plotting lengths (y-axis) against ages (x-axis) for walleye pollock sampled in 2021. Blue circles (or box-and-whisker plots) represent samples from the Western Bering Sea and green circles represent samples from the Eastern Bering Sea.

July 11, 2019July 12, 2019

Erica Marlaine: Oh, the Places You’ll Go! July 6, 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 6, 2019

Weather Data from the Bridge:

Latitude: 55º 4.07N
Longitude: 156º 42 W
Wind Speed: 3.2knots
Wind Direction: 96º
Air Temperature: 10.3º Celsius
Barometric Pressure: 1025.7. mb
Surface Water temperature: 11.05º Celsius
Depth of water column: 1,057.6 meters

If you love science and exploring, consider a career in the NOAA Corps!

NOAA Corps

The NOAA Corps is one of our nation’s seven uniformed services (along with the Army, Marine Corps, Navy, Air Force, Coast Guard, and Public Health Service Commissioned Officer Corps). NOAA Corps officers are an integral part of the National Oceanic and Atmospheric Administration (NOAA), an agency of the U.S. Department of Commerce. NOAA and the NOAA Corps can trace their lineage to 1807 when President Thomas Jefferson signed a bill for the “Survey of the Coast.” The survey work was done by Army and Naval officers along with civilian men and women. The Coast Survey was actually the first federal agency to hire female professionals! Their duties included charting our nation’s waterways and creating topographic maps of our shorelines, which made our marine highways among the best charted in the world.

Today, the NOAA Corps is an elite group of men and women trained in engineering, earth sciences, oceanography, meteorology, and fisheries science. NOAA is comprised of the National Weather Service, National Marine Fisheries Service (NOAA Fisheries), Office of Oceanic and Atmospheric Research (NOAA Research), National Environmental Satellite, Data and Information Service, National Ocean Service, and the Office of Marine and Aviation Operations. NOAA Corps officers operate NOAA’s ships, fly aircraft, manage research projects, conduct diving operations, and serve in staff positions throughout NOAA.

NOAA Officer Spotlight

I had the opportunity to speak with Ensign (ENS) Lexee Andonian (although by the time this is published Ms. Andonian will have been selected for LTJG (Lieutenant junior grade)! ENS Andonian has been a member of NOAA Corps for almost 2 years, and loves her job, but it was not something she originally considered as a career (or even knew about). She first learned about NOAA while working at a rock climbing gym. A patron mentioned it to her, and offered to show her around a NOAA ship. She went home and googled NOAA. With her interest piqued, she decided to accept the patron’s offer, and went to Newport, Oregon to tour the NOAA Ship Bell M. Shimada (which is actually the sister ship of the NOAA Ship Oscar Dyson. A sister ship means they were based off the same blueprint and can serve similar projects.)

ENS Andonian applied for the NOAA Corps, but was waitlisted. NOAA is highly selective and accepts a very limited number of applicants (approximately 15-25 twice a year.) Undeterred, she applied for the next NOAA class, and was once again waitlisted, but this time she was accepted off the waitlist. After 5 months of training at the Coast Guard Academy, she was ready to begin her assignment onboard a NOAA ship, where additional hands-on training occurs non-stop. Each NOAA Corps member wears a multitude of “hats” while onboard. ENS Andonian is currently the Acting Operations Officer, the Navigation Officer, the Environmental Compliance Officer, and the Dive Officer. ENS Andonian loves that her job allows her to see unique places that many people never get to explore since they are not accessible by plane or car. Asked what she misses the most from home, she said, “Bettee Anne” (her dog).

Science and Technology Log

Today I was introduced to a few new species in the fish lab. Until now, most of the jellyfish have been Chrysaora melanasta, which are beautiful and can be quite large, but today I saw 2 egg yolk jellyfish, aptly named as they look like egg yolks.

I also saw a lumpsucker, which is the cutest fish I have ever seen. Lumpsuckers look like little balls of grey goo. He (or she) seemed to look right at me and kept opening and closing its mouth as if trying to say something. Lumpsuckers have a suction cup on their bottom which allows then to adhere to rocks or other surfaces.

Personal Log

As a teacher, I create experiences for my students that will take them out of their comfort zone so that they can realize just how much they are truly capable of. On the NOAA Ship Oscar Dyson, it is my turn to step outside my own comfort zone. If you would have told me a few months ago that I would feel comfortable being elbow-deep in live fish and jellyfish, or dissecting fish to see whether they are male or female, or slicing into a fish’s head to collect otoliths (ear bones), I would not have believed you, but that is how I spend every day onboard the Oscar Dyson, and after 2 weeks, it feels like something I have done all my life. It is an experience I highly recommend to everyone!

A slice is made slightly behind the pollock’s eyes.
Otoliths are then removed using forceps.
Walleye pollock otoliths.
Otoliths are bottled and sent for further analysis.

June 27, 2019

Karah Nazor: The Glowing Dolphins of the Channel Islands and Interview with UCSC Graduate Student Ilysa “Ily” Iglesias, May 31, 2019

NOAA Teacher at Sea

Karah Nazor

Aboard NOAA Ship Reuben Lasker

May 29 – June 7, 2019

Mission: Rockfish Recruitment & Ecosystem Assessment

Geographic Area: Central California Coast

Date: May 31, 2019

Game Plan and Trawling Line: Channel Islands San Nicolas Line

I am up on the flying bridge and I just saw two humpback whales spouting, an albatross soaring and a large Mola Mola on the sea surface. In this blog I will write about an amazing once in a lifetime experience that from last night- May 31, 2019. The first haul was called off due to an abundance of Pacific White-Sided Dolphins, Lagenorhynchus obliquidens, (as reported by the inside marine mammal watch prior to net deployment), so we motored on ahead to the second station, but dolphins chased the ship all the way there, too. One strategy to encourage marine mammals to leave is for the ship to stop moving with the hope that the dolphins become disinterested and vacate the area. This pod was intent on having a party at the ship so Keith Sakuma encouraged everyone to just go outside to observe and enjoy the dolphins!

Fishing on this survey takes place at nighttime (so the fish do not see the net) and Scripps graduate student Kaila Pearson and I stepped outside on the side deck into the darkest of dark nights. Kaila and I carefully placed one foot in front of the other because we couldn’t see our feet and where to step next. I was afraid I would trip. When I asked Keith Hanson if we should use a flashlight to safely make our way up to the top deck, he suggested that we stay in place for a few minutes to allow our eyes to adjust. Within 5 minutes or so objects around us started to present themselves to us within the black void. We could eventually see our feet, each others faces, the dolphins, and even the finer features of the sea surface.

Within a few minutes Ily Iglesias reported seeing bioluminescence, a type of chemiluminescence that occurs in living things, such as the familiar green glow of lightening bugs in the Summer in the South. This glow results from oxidation of the protein luciferin (present in photophore cells/organs) by the enzyme luciferase. It its excited state, lucifern emits light. This reaction is known to occur in some marine bacteria, dinoflagellates (single celled photosynthetic organisms), squid, deep sea fish, pyrosomes and jellyfish, and I am fortunate to have observed many of these creatures already on this research cruise (see photos below). Some animals have photophore organs and generate their own luciferin, while others are hosts to bioluminescent bacteria.

The large photo organ is a large green circle under the eye of the deepsea longfin dragonfish, *Tactostoma macropus*.

California lanternfish, *Symbolophorus californiensis*, with photophores under the lateral line and the ventral surface.

Blue lanternfish, *Tarletonbeania crenularis*, collected from a bongo net at 265 meters. Photophores line the ventral surface of the body.

*Cranchia scabra* “baseball squid” with large photophores lining the eyes.

Chiroteuthis veranii squid — *Chiroteuthis veranii* squid

When dinoflagellates floating on the sea surface are agitated, they glow. At first when I was trying really hard to see this, I noticed a couple of tiny flashes of green light, sort of like lightening bugs, but it wasn’t anything super obvious. In time, I noticed clouds of faint light, sort of like a glowing mist floating the water’s surface, that moved up and down with the swell. I hypothesized that dinoflagellates on the sea surface were being agitated by the passage of waves through them and Ily suggested that it was caused by schools of anchovies.

Since the dolphins were intent on staying, we decided to head to the next station. I knew that as the ship began to move that the bow would be breaking through surface water that had previously been undisturbed, and I predicted the bioluminescence would be much more intense.

As we took off, the dolphins began to bow surf and, as I predicted, the dinoflagellates were activated and this time their glow was a bright white. As the dolphins surfaced to breath, their skin became coated with the glowing algal cells, creating an effect as if they were swimming in an X-ray machine. The dolphins were literally glowing white swimming in a black sea! We were so entranced and excited by the beauty, we screamed in delight. I am sure the dolphins heard us cheering for them. They too, seemed excited and could see each other glowing as well.

Next we saw the faint cloud of dinoflagellates caused by Northern anchovies (Ily was right) up ahead of us. As the ship encountered the school of small (~ 3-6 inch) fish, they also started to glow really bright and it was easy to see all of the individual fish in the school. The dolphins could also see the glowing fish and split off in different directions to hunt them. There were hundreds of fish that dispersed as they were being chased creating a pattern of short white glowing lines somewhat like the yellow lane markers on the highway.

The display was unlike anything I have ever witnessed. It was like the Aurora Borealis of the sea. Despite our best efforts, our cell phone cameras were unable to pick up the bioluminescent signal, however, we do not need photos because the patterns of light will be forever embedded in our minds. The dolphins eventually tired from the surf and chase and departed. Ily said the experience was “an explosion of light that overwhelmed the senses” while Flora said it was “better than fireworks.”

With no marine mammal sightings at the third station, we completed a five minute haul in the deep channel and collected a huge white bin of anchovies (see photo of Keith Hanson with this catch below). In this catch we found a few Mexican lampfish, 3 king of the salmon, a lot of of large smooth tongues, a lot of salps, a few pyrosomes and one purple striped jellyfish. The purple-striped jelly (Chrysaora colorata) is is primarily preyed upon by Leatherback turtles. Haul 2 was conducted over shallower water near San Nicolas Island and we only found salps and four small rockfish in the catch. After these two hauls, we called it a night and wrapped up at 4:15 a.m.

Scientist Spotlight: Ilysa Iglesias, NMFS SWFSC FED/ University of California Santa Cruz (UCSC)

Ilysa “Ily” is a doctoral student who works in John Field’s Lab at UCSC. She is studying the fish we are collecting on this cruise as part of her research. She is very knowledgeable about all of the survey research objectives. She is also one of the most positive and gregarious people I have every met. Ily grew up in Santa Cruz, CA, and enjoys surfing, hiking, gardening and raising chickens. Ily is a fan of early marine explorer Jacques Cousteau, who often wore a red beanie/toboggan and a blue shirt. Ily came prepared and brought six red hats (that she knit herself) for each of the members of the sorting team. Ily’s favorite fish is the hatchetfish. She was thrilled when we found on in the catch!

Ilysa with hatchetfish — Ilysa Iglesias with deepsea marine hatchetfish

A deepsea marine hatchetfish caught in the bongo which was deployed to depth of 265 meters.

Ily obtained a Bachelor’s degree from UC Berkeley in integrated biology and a Masters Degree from the University of Hawaii in Zoology with a specialization in marine biology. Her thesis was on the function of intertidal pools as a nursery habitat for near-shore reef fish. She compared otoliths (fish bone ears) of fish reared inside and outside of tide pools and compared their growth rates. Otoliths can be used to the age of the fish much like counting rings on a tree and stable isotope analysis reveals information about where the fish were reared.

Ily, Flora and Kristin have all used otoliths in their research and taught me how to locate and collect the sagittal otolith from anchovies and myctophids. It is a tiny ear bone (one of three) that is positioned near the hindbrain of fish. See photos below of the otoliths we collected. This is a technique that I will definitely take back to my classroom and teach my McCallie students.

Photomicrograph of otoliths we collected from blue lanternfish (top) and Northern Anchovy (bottom) and observed under the dissecting microscope.

After obtaining her masters degree, Ily was Conservation Fellow for the Nature Conservancy in HI and worked in octopus fisheries before returning home to join NOAA’s salmon team and then the rockfish team as a Research Associate. Ily has just completed the first year of her doctoral work in the Field Lab and expects to complete the program within 5 years.

On this cruise, Ily is collecting small fish called Myctophids for her research. These are small bioluminescent fish that live at depths of 300 and 1,500 m in the bathypelagic zone. In this survey, we encounter these deep sea dwellers during their nightly vertical migration up to the edge of the photic zone at depths we are targeting. They are likely chasing their prey (krill) on this upward journey. It is amazing to me they are able to withstand the pressure change. Mcytophids are also known as lanternfishes and have bioluminescent photophores dispersed on their bodies. The fish sorting team analyzes the position of these organs to help distinguish between the different species. There are 243 known species of myctophids, making these little fishes one of the most diverse vertebrates on Earth. They are so abundant in the sea that they make up 65% of the ocean’s biomass, but most people have never heard of them!

In 2014- 2015 there was an anonymously high sea surface temperatures off of the Pacific Coast known as The Blob. Marine scientists are still elucidating the effect of the hot water had on fish populations and ecosystems. Ily explains that “atmospheric forcing caused changes in oxygen and temperature resulting in variability in the California current.” The water was less nutrient dense and caused a reduction in phytoplankton. This disruption of primary production propagated up the trophic cascade resulting in die offs of zooplankton, fish, marine mammals and birds.

Ily is using the catch records and acoustics data from the rockfish survey to study changes in distribution and abundance of myctophids from before, during and after The Blob (2013-2019). She aims to understand if and how their trophic position of myctophids was affected by the unusually high sea surface temperatures. Using elemental analysis isotope ratio mass spectrometry to analyze the Carbon and Nitrogen atoms incorporated into fish muscle, Ily can determine what the myctophids were eating each year.

September 24, 2017

Kate Schafer: So Many Snappers… September 24, 2017

NOAA Teacher at Sea

Kate Schafer

Aboard NOAA Ship Oregon II

September 17 – 30, 2017

Mission: Shark/Red Snapper Longline Survey

Geographic Area of Cruise: Gulf of Mexico

Date: September 24, 2017

Weather Data from the Bridge:

Latitude: 28^o 25.1’ N
Longitude: 94^o50.3’ W

Broken sky

Visibility 10 nautical miles

Wind speed 13 knots

Sea wave height 2-3 feet

Temperature Seawater 28.8 ^oCelsius

Science and Technology Log:

This is a shark and red snapper longline survey, and the sharks tend to steal the stage. They are bigger (for the most part), more diverse and definitely have more of a reputation. I have been surprised, however, by how much I’ve been drawn to the snappers. They are a beautiful color, and tend to come up in groups that are pretty similar in size.

The Northern Red Snapper (Lutjanus campechanus) is commonly fished in the Gulf of Mexico, both recreationally and commercially. It turns out that the commercial fishers get 51% of the catch quota and the recreational fishers get 49%. The methods for dividing up those two basically equal pieces of the pie is different between the commercial and recreational fishers. In addition, the commercial fishing catch is monitored very closely, while the recreational fishing catch numbers are largely unknown. Plus, the states have their own waters that extend out to different distances, depending on the state, and the federal waters extend from the state water boundary to 200 nautical miles offshore. So, in other words, managing the fishery is quite complicated.

So, how do all these fishing rules and regulations get established and modified over time? A law was passed in 1976, called the Magnuson-Stevens Fishery Conservation and Management Act, and one of the key parts of the act established eight regional management councils for regulating fishing in federal waters (more information on the act here: http://www.nmfs.noaa.gov/sfa/laws_policies/msa/). It also established the 200 nautical mile extension of federal waters from land. The Gulf of Mexico Fishery Management Council (GMFMC) is responsible for creating Fisheries Management Plans (FMPs) for fisheries within the U.S. federal waters of the Gulf of Mexico, from southern Texas, along Louisiana, Mississippi, and Alabama, and down the west coast of Florida. This graphic shows the catch limits for red snapper and other species for 2017 set by the GMFMC. For red snapper, the catch limit is close to 14 million pounds.

2017ACLBLOGGraphic_07-17-1024x663 — Annual Catch Limits as set by the Gulf of Mexico Fishery Management Council (http://gulfcouncil.org/fishing-regulations/federal/)

The data that we are collecting helps scientists and policy makers to determine what the annual catch limit for a particular season should be. For each fish that we bring on board, we measure the fish length and weight, as well as the weight of the gonads. In addition, we collect their otoliths (ear bones) and samples of the ovaries of females. These both help managers to estimate the age and size of the population, and future populations as well.

Otoliths are calcium carbonate hardened structures and are present in the part of the inner ear that is responsible for balance. Humans and other vertebrates have them too, and they can be used to tell the age of the fish. The otoliths of Lutjanus campechanus are quite large. There seems to be an overall relationship between the habitat of the fish species and the size of the otolith. Species like Lutjanus campechanus that live along reefs and rocky structures have much larger otoliths than species like tuna that swim up in the water column. Flying fish, which we’ve seen a lot of, also have large otoliths, given their body size, probably aiding them in knowing where they are as they glide through the air.

Well, we have been collecting a lot of data over the past couple of days to help inform these policies in the future! Each line we’ve pulled in lately has had a dozen or more snappers on it, and they are a lot of extra work as compared with the sharks, due to all the samples we have to collect once we’re done. A couple times, we’ve barely finished before it was time to start baiting lines again.

Personal Log:

As I mentioned earlier, I’ve really come to love the red snappers. Their eyes are the same color as their skin and I’m just awed by their size. I am used to snappers that I’ve watched on coral reefs, and even the largest species I’ve seen on reefs are nothing compared with these guys.

SnapperEye — Red snapper (Lutjanus campechanus) eyes

I’ve also adjusted to the shift in my day, as evidenced by the fact that I’m finishing this up at 1 a.m. It has been a long time since I’ve been on this kind of late night schedule. I’m enjoying it, especially because I know when I return to California, I’ll be getting up at 5:30 a.m. again.

Did You Know?

That snappers eat a wide variety of different foods, including fish and various types of crustaceans? Here are a couple of items we’ve found in the ones we’ve caught. Can anyone identify them? I studied the second group for my Ph.D. dissertation!