acoustic survey – Page 2 – NOAA Teacher at Sea Blog

July 16, 2009April 5, 2021

Megan Woodward, July 16, 2009

NOAA Teacher at Sea
Megan Woodward
Onboard NOAA Ship Oscar Dyson
July 1 – 18, 2009

Mission: Bering Sea Acoustic Trawl Survey
Geographical Area: Bering Sea/Dutch Harbor
Date: Tuesday, July 16, 2009

All bony fish have otoliths (ear bones) that can be used for calculating the age of the fish.

Weather and Location
Position: N 58 13.617; W 171 25.832
Air Temp: 7.2 (deg C)
Water Temp: 6.54 (deg C)
Wind Speed: 15 knots
Weather: Overcast

Science and Technology Log

One of the most interesting things I’ve learned while participating in the pollock survey is the importance of otoliths. Otoliths are small bony structures situated in the head of all bony fish, and are often referred to as “ear stones.” For each haul we brought on board, 50 otoliths were taken from large fish (3+ years) and/or 5 from small fish (younger than 3 years old). The otolith holds the key to accurately calculating the age of a fish (scales and vertebrates can also be used, but are not as reliable). The average age of fish from the samples collected in the survey helps scientists estimate the strength of a year-class and size of the stock in the future.

Back in the lab, otolith samples are carefully catalogued.

The first step in taking an otolith is pictured above. An incision is made on the back of the pollock’s head, and an otolith is removed using tweezers. Once the otolith is removed, it is rinsed with water and placed in a glass vial containing a small amount of 50% ethanol solution for preservation purposes.

The otoliths are taken back to NOAA’s aging lab where ages are determined by reading rings similar to those on a tree trunk. A crosscut is made through each otolith revealing a pattern of rings. Scientists then count the rings to determine the age of the fish. Lightly burning or staining the otoliths makes the rings more visible.

New material is deposited on the surface of the otolith creating the rings as the fish grows. The translucent/light zones indicate the main growth that takes place in the summer months. The opaque/darker rings appear during the winter months when growth is slower. Because of the slower growth rate, new material is deposited on top of the old layers resulting in the dark ring. Each pair of light and dark zones marks one year. In fish younger than one year of age, rings can be identified for each day of life!

Personal Log

I was surprised to discover otoliths have been used for aging fish since the early 1900’s. While working in the fish lab I observed the scientist removing otoliths, however I did not remove any myself. The cracking sound heard when cutting the head open was like fingernails on a chalkboard to me. I spent most of my time in sorting and measuring fish, as well as assisting with the stomach collection project.

For the next two days we will be heading back to Dutch Harbor, and the likelihood of trawling for more fish is minimal. Our remaining work assignment is to give the fish lab a thorough cleaning. Everything in the lab is waterproof, so we’ll put on our Grunden’s (orange rubber coveralls) and boots and spray down the entire space. Working and living at sea for nearly 3 weeks has been an eye opening experience. My time aboard the Oscar Dyson has flown by. I have learned so much about fisheries research and life at sea. Dry land, however, will be warmly welcomed when we get back to Dutch Harbor. Would I do it again? Absolutely.

Animal Sightings

The whales have an incredible way of showing up when I don’t have my camera. Yesterday I spotted two orcas, but did not get a photograph. The seabirds continue to circle. I like the murres most. They look like small, flying penguins.

New Vocabulary

Otoliths- Small bony structures situated in the head of all bony fish. Often referred to as “ear stones.”

Stock- Refers to the number of fish available, supply.

*** Much of the information used for this log entry was found on the Centre for Environment, Fisheries & Aquaculture Science (Cefas) web site.

July 15, 2009April 5, 2021

Jennifer Fry, July 15, 2009

NOAA Teacher at Sea
Jennifer Fry
Onboard NOAA Ship Miller Freeman (tracker)
July 14 – 29, 2009

Mission: 2009 United States/Canada Pacific Hake Acoustic Survey
Geographical area of cruise: North Pacific Ocean from Monterey, CA to British Columbia, CA.
Date: July 15, 2009

Weather Data from the Bridge
Wind Speed: 19 kts.
Wind direction: 355° north
Temperature: 15.4°C (dry bulb); 13.2°C (wet bulb)

Science and Technology Log

This picture shows the Miller Freeman in Alaskan waters. On our cruise, it’s working off the coast of California.

Our cruise was delayed for a day due to poor weather conditions and heavy seas. We began with a meeting of the scientific team which consists of 8 members all with their specific scientific knowledge and expertise. We will be conducting several types of oceanographic sampling during our cruise: 2-3 hake tows per day, weather permitting, an open net tow where fish are viewed through a camera, XBTs: Expendable Bathythermograph, HABS: Harmful Algal Bloom Sampling, and CTD: Conductivity, Temperature, and Density. The ship conducted Man Overboard and Fire drills.

The research vessel Miller Freeman set sail from Eureka, California on Wednesday, July 15^th at approximately 12:30. Each person aboard is assigned a specific job and place to report on the Miller Freeman during such an event. Our assignments are posted on our stateroom door. During a Fire/Emergency Drill the signal is a 10 second blast of the general alarm and/or ship’s whistle. I am to report or muster to the Chemical Lab.

In the event of an Abandon Ship Drill, I am assigned to life raft #2 and muster on the O-1 deck, port (left) side. The Abandon Ship signal is more than 6 short blasts followed by one long blast of the general alarm and/or ship’s whistle. If a Man Overboard Drill is called, we will hear 3 prolonged blasts of the general alarm and/or ship’s whistle. The muster station is the Chemical Lab. If we personally see a person go overboard the ship there are three things to do immediately: Throw a life ring overboard, call the bridge, and keep your eyes on the person.

These things all need to be done as simultaneously as possible to assure the safety and recovery of the person who is in the sea. It is important to conduct these emergency drills so that everyone is ready and prepared in the case of an emergency event.

Personal Log

I am sharing a stateroom with Julia Clemons, an oceanographer on board the Miller Freeman. She works for NOAA Fisheries in Newport, Oregon. Her educational background includes a Bachelors’ degree in Oceanography and a masters’ degree in Geology. The scientists and crew on board are so professional and willing to teach and tell about their job. They are an amazing group of people.

New Term/Phrase/Word
Domoic acid

Questions of the Day?
What does a hake look like in person?

Animals Seen Today
5 Egrets
1 great blue heron
Numerous gulls

July 14, 2009April 5, 2021

Jennifer Fry, July 14, 2009

NOAA Teacher at Sea
Jennifer Fry
Onboard NOAA Ship Miller Freeman (tracker)
July 14 – 29, 2009

Mission: 2009 United States/Canada Pacific Hake Acoustic Survey
Geographical area of cruise: North Pacific Ocean from Monterey, CA to British Columbia, CA.
Date: July 14, 2009

Weather Data from the Bridge
No data (In port)

Science Log

After arriving at the Eureka airport I found my way to the Miller Freeman thanks to many friendly Eurekan locals. What a lovely town with many interesting sights including the dock area, downtown with its renewed turn of the century architecture. Upon arriving at the Miller Freeman I was greeted by Ensign Heather Moe who graciously gave me a tour of the ship.

There were four decks or levels to the ship which include:

Flying Bridge Deck: observations take place as well as storage
Bridge Deck: Navigation can take place from the bridge or the trawl house. The trawl house faces toward the stern of the ship and is used to control the ship during “fishing.”
Boat Deck: Officers’ & Chief Scientist’s staterooms. A stateroom is where you would sleep on a boat or ship. Your bed is called a “rack.” Most staterooms on the Miller Freeman have bunk beds. The boat deck is where the small launches/rescue boats are stored.
There is: a FRB, Fast Rescue Boat, and a small launch.
Quarterdeck/ Main Deck: Ship’s store, survey officers’ staterooms and the back deck, used for fishing. *The term quarterdeck was originally, in the early 17th century, used for a smaller deck, covering about a quarter of the vessel. It is usually reserved for officers, guests, passengers. It is also an entry point for personnel. Lower/ Galley Deck: Crew’s and scientists’ staterooms, library, two lounges, galley, where everyone eats their meals.
Hold: Gym for exercising and engineer’s storage area.

Question of the Day
Where did the word quarterdeck* originate? (see answer above)

Animals Seen Today
Egrets Blue Heron Gulls

July 12, 2009April 5, 2021

Megan Woodward, July 12, 2009

NOAA Teacher at Sea
Megan Woodward
Onboard NOAA Ship Oscar Dyson
July 1 – 18, 2009

Mission: Bering Sea Acoustic Trawl Survey
Geographical Area: Bering Sea/Dutch Harbor
Date: Tuesday, July 12, 2009

Any bycatch in a haul has to be measured and weighed if there are more than 25 of the same species caught. — Any bycatch in a haul has to be measured and weighed if there are more than 25 of the same species.

Weather/Location
Position: N 60.35.172; W 174.08.187
Air Temp: 6.1 (deg C)
Water Temp: 5.24 (deg C)
Wind Speed: 25 knots
Weather: Overcast, rain

Science and Technology Log

How is all the data collected from a trawl and acoustic lab used? By collecting data about weight and length from a sample, scientists are able to connect the size of fish caught to the amount of return seen in the acoustic lab. The return is assigned a name (PK1, PK2, etc.) and all schools showing a similar acoustic pattern are given the same name. In the end, scientists can estimate the number of fish and their size for a given area based on the acoustic and fish lab data collected. This is repeated throughout the survey resulting in an estimate for the total number of fish in the survey area.

Both during and after the survey estimates of abundance in the same location over the past several years are compared. Scientists evaluate the data and determine if the pollock population in the survey area is increasing, declining or stable. Their conclusions are used to make a recommendation about pollock fishing limits for the upcoming year. In the past few years the pollock population has been lower than in previous years. Due to the decline, the fishing quota has been reduced. However, the 2006 year-class is proving to be strong. At 4 years of age pollock are considered mature and fishable. Therefore, the fishing quota is predicted to rise in the next year or two.

Personal Log

While discussing the acoustic survey project with the scientists on board, I was quite surprised to hear the pollock survey had been going since 1979. Acoustic technology has changed and improved, but in essence the project has remained the same. Modern computer technology has allowed collection and analysis of enormous data sets and greatly reduced the amount of paper work needed for the project’s success.

The concept of strong vs. weak year-class is also quite interesting. There doesn’t seem to be a direct connection between a year-class’ success and environmental factors. Environmental factors that are potentially influential are water temperature, available zooplankton, ice cover, storms and predators. The fish currently being caught by commercial fisherman are 5-7 years old. Can you figure out which year classes those fish are from?

We continue to spot plenty of seabirds and a few more minke whale pods. I was able to watch a group of Dall’s porpoises play in the wake of the bow for half an hour yesterday. There haven’t been any new animal sightings during the past few days.

Although we are out here working in the best interest of pollock, I have found it difficult to watch thousands of pollock come through the fish lab. I have to remind myself that sampling the fish is truly for the good of the order. In addition, after being measured the fish are sent back into the ocean where they become food for other organisms such as crab or birds. One of their natural predators is having a good meal, something that was likely to happen anyway.

Animal Sightings

Seabirds
Dall’s porpoises

New Vocabulary

Bycatch – Anytime something is caught during a trawl other than pollock it is labeled bycatch. Jellyfish has been the most common form of bycatch.

Year-class – All the fish born in a given year are members of that year-class. We have caught a lot fish from the 2008 year-class (1 year old fish).

July 10, 2009April 5, 2021

Megan Woodward, July 10, 2009

NOAA Teacher at Sea
Megan Woodward
Onboard NOAA Ship Oscar Dyson
July 1 – 18, 2009

Mission: Bering Sea Acoustic Trawl Survey
Geographical Area: Bering Sea/Dutch Harbor
Date: Tuesday, July 10, 2009

The pollock are carefully loaded onto the table.

Weather/Location
Position: N 56.30.202; W 172.34.37
Air Temp: 7.4 (deg C)
Water Temp: 7.4 (deg C)
Wind Speed: 19 knots
Weather: Overcast

Science and Technology

Once the fish are onboard a rigorous data collection process begins. All of the data collected are recorded via instruments linked to a computer network in the fish lab. Below is a series of photos showing the process used in the fish lab to collect valuable data.

Once the fish are on the table, we carefully look through the fish for any species other than pollock caught in the trawl. These non-pollock species are sorted into bins and accounted for. The fish are weighed one basket full at a time as they reach the end of the conveyor belt. Initially, we take a count of how many fish fill one basket. There is a scale connected to a computer program that records the basket’s weight.

The sorting begins. The pollock are sorted between male and female.

After weighing the pollock, we move on to sorting a sample of approximately 300 fish by sex. To find the sex of a fish we cut open its belly and look for either male or female reproductive organs. The sexed fish are then placed in the appropriate bin. Next, each pollock from the male/female sort is measured in centimeters. We use a measuring board linked to a computer that records the size of each fish. There is a small tool in my hand that gets placed at the “v” of the fish tail. Sensors on the board detect the placement of the measuring wand, and send a length measurement to the computer so it can be recorded. This program also keeps track of how many fish we measure, so we get an accurate sample count.

The stomach of a pollock is prepared for preservation.

Several scientists have asked us to collect pollock for various research projects. One project, designed to study the diet of pollock, requires us to sex, measure, weigh and take the stomach of 20 pollock from each haul. A label with all of the information is placed in a bag with the stomach. They are placed in a freezer for preservation purposes.

Here I am using the measuring board. The stomach of a pollock is prepared for preservation. — Here I am using the measuring board.

We also use a similar process for scientists examining one-year-old pollock. This study asks for the entire fish to be preserved, not a specific organ. In one 12-hour shift there is a maximum of 3 trawls if fish sign is identified in the acoustics lab. Each trawl takes 2 to 3 hours to process. It’s possible another trawl could happen while finishing up the data collection from the previous haul. This makes for a very busy, fish filled shift.

Personal Log

Working in the fish lab has provided for a tremendous amount of new learning to take place. I’ve learned to identify species of fish that mix in with pollock (capelin, flatfish, skate and cod), and have seen several crustaceans and jellyfish, too. All of the measuring technology has been straight forward and user friendly. Sexing the fish has been the most difficult job, but has become easier with practice. Examining the innards to identify male or female reproductive organs seems nearly impossible in the young fish, and it’s not always clear in the older fish.

Today I was in charge of weighing the fish as they came down the conveyor belt. I was certainly mistaken when I thought it would be a simple task. First off, I had to count the fish as they dropped into the basket at a speed faster than I could count. At the same time I had to control the speed of the belt and open the gate so more fish would move down the line. When the basket was full, I stopped the belt and placed the full (semi-accurately counted) basket on the scale and waited for the scale’s “steady” signal to come on. Since the boat is constantly in motion the steady light rapidly blinks on and off. It took me three tries before I managed to get the basket weighed. Meanwhile the rest of the team patiently waited. Maybe I’ll give it another try tomorrow.

This average sized skate was flapping his wings making him difficult to hold. Look closely at the fish on the conveyor belt and you will see hermit crabs and seastars.

Basketstars were brought up in a bottom trawl. Hermit crabs and snails were also caught in the bottom trawl. — Basketstars were brought up in a bottom trawl.

Hermit crabs and snails were also caught in the bottom trawl. — Hermit crabs and snails were also caught in the trawl.

Animals Seen

Minke Whale
Skate
Pacific Cod
Tanner Crab
Snow Crab
Basketstar
Sturgeon Poacher
Snails
Hermit Crabs
Arrow Tooth Flounder