methot trawl – NOAA Teacher at Sea Blog

June 29, 2018June 29, 2018

Lacee Sherman: Teacher Running Out of Witty Blog Titles June 27, 2018

NOAA Teacher at Sea

Lacee Sherman

Aboard NOAA Ship Oscar Dyson

June 6, 2018 – June 28, 2018

Mission: Eastern Bering Sea Pollock Acoustic Trawl Survey

Geographic Area of Cruise: Eastern Bering Sea

Date: June 27, 2018

Snailfish!!! — TAS Lacee Sherman with an Okhotsk Snailfish

Weather Data from the Bridge at 15:00 on 6/27/18

Latitude: 56° 32.03 N

Longitude: 168° 08.15 W

Sea Wave Height: 2 ft

Wind Speed: 9 knots

Wind Direction: 229° (SW)

Visibility: 8 nautical miles

Air Temperature: 9.8° C

Water Temperature: 8.5° C

Sky: Broken cloud cover

Water and cloud cover on 6/27/18 @ 15:00

Science and Technology Log

Sometimes the pursuit of scientific knowledge requires very precise scientific instruments, and sometimes it just requires a bucket, funnel, and a coffee filter. During the CTD casts, a special bottle collects water samples from a specific depth. The CTD can hold multiple water sample bottles, so a few days ago I was able to choose the location for an extra water sample to be taken. The required water sample was taken near the ocean floor, and I requested one at about 15 meters below the surface.

On the EK60 we had noticed a lot of “munge” in the water near the surface and we wanted to know exactly what was in the water that was reflecting an acoustic signal back up to the transducers since it did not appear to be fish. The upper part of the water column that had the munge was expected to have more small and microscopic organisms than the sample taken at a lower depth because of what had been seen on the EK60.

Water Collection Bottle — CTD water collection bottles

The CTD water bottles have flaps on the ends that can be triggered at specific depths. When the two CTD bottles were brought back on the ship, they were opened to pour out the water samples. Once the required 1 liter sample from the bottle taken near the ocean floor was put aside for another scientific study, the rest of the water was put into large white buckets to be sampled and inspected as we saw fit. We had one large bucket filled with water from near the bottom which we labeled “deep” and the water from only 15 meters down, which we labeled “shallow”.

We used coffee filters placed in funnels to strain out any microscopic organisms from the water. We had one set up for the “shallow” water sample, and another for the “deep” water sample. When there was a tiny bit of water left in the filter, we used a pipette to suck up the slurry of microscopic organisms and a bit of water and place them in a glass dish. From there, we took a few drops from each dish and put them under a dissecting microscope.

Filtering Ocean Water — Funnel and coffee filter straining the living organisms out of ocean water

Using the dissecting microscope we were able to identify a few things that we were seeing, and even take photos of them through a special part of the microscope where a camera could be attached. We did not individually identify everything that we saw, but we did notice that there were diatoms, rotifers, crab larvae, and some type of egg. There was a noticeable difference though between the quantity of organisms in the shallow and deep samples. As predicted, the shallow water sample had many more microscopic organisms than the deep water sample.

Diatoms, eggs and larvae under the microscope

Personal Log

Yesterday we did two trawls and one Methot sample. I understand so much more now about exactly how all of the instruments work and how to operate some of them. I finally feel like I was getting the hang of everything and able to be more helpful. Each trawl takes about 3 hours plus processing time, so the days pass much quicker when we are fishing often.

Methot net being brought on deck — Methot net coming on deck after a haul

In our second trawl of the day we ended up catching a really neat kind of snailfish that isn’t very common. It’s always exciting to get something other than pollock in the nets, and it was really neat this time since no one else had ever seen one before either! After spending a lot of time taking photos, looking at identifying features and using books and the internet to help, we finally were able to identify it as an Okhotsk Snailfish.

Okhotsk Snailfish belly

Okhotsk Snailfish head

Okhotsk Snailfish suction

Okhotsk Snailfish

Okhotsk Snailfish side view of face

Okhotsk Snailfish Body

Okhotsk Snailfish head

Okhotsk Snailfish belly

Okhotsk Snailfish Body

Okhotsk Snailfish

Okhotsk Snailfish suction

Okhotsk Snailfish side view of face

Today we are steaming back to Dutch Harbor, AK and I have to admit that I have mixed feelings about leaving life on the ship behind. I will miss being a part of research and working with the MACE team. I love being able to do research, and work closely with scientists and learn more about something that I really enjoy. I will also definitely miss seeing the ocean every day. I think it will probably be strange to walk on land now. Since the ground won’t be moving anymore, hopefully that means that I can stop walking into walls!

All operations stopped on the ship last night so that we can have enough time to make it back to land before 09:00 on June 28, 2018. Today I will be packing up my things, cleaning up my room for the next person, and then helping to clean and scrub the fish lab. Tomorrow I will return to life as a land dweller, although hopefully not forever.

Did You Know?

According to the Encyclopaedia Britannica, “The Bering Sea has more than 300 species of fish, including 50 deep-sea species, of which 25 are caught commercially. The most important among them are salmon, herring, cod, flounder, halibut, and pollock.”

August 8, 2013August 20, 2021

Melissa George: Scraping the Bottom-Dwellers, August 6, 2013

NOAA Teacher at Sea
Melissa George
Aboard NOAA Ship Oscar Dyson
July 22 – August 9, 2013

Mission: Pollock Survey
Geographical Area of Cruise: Gulf of Alaska
Date: Tuesday, August 6, 2013

Current Data From Today’s Cruise (9 am Alaska Daylight Time)

Weather Data from the Bridge
Sky Condition: Partly Cloudy
Temperature: 15° C
Wind Speed: 7 knots
Barometric Pressure: 1019.6 mb
Humidity: 90%

August 6, 2013: Partly Cloudy or Partly Mountainy?

Sun and Moon Data
Sunrise: 5:15 am
Sunset: 9:33 pm
Moonrise: 5:33 am
Moonset: 8:45 pm

Geographic Coordinates ( 9 am Alaska Daylight Time)

Latitude: 59 ° 20.4 N Longitude: 141° 16.6 W
The ship’s position now can be found by clicking: Oscar Dyson’s Geographical Position

Science and Technology Log

Besides the mid-water trawling, information about the pollock population is gathered in other ways on the Oscar Dyson research vessel. One of these ways is direct, monitoring the pollock by trawling in other parts of the water column; the other way is indirect, evaluating the prey that the pollock feeds on.

Bottom Trawling

Scientists use acoustics to locate the signal for the fish. Sometimes this signal is noticed near the ocean floor. In this case, the PolyNor’eastern (PNE) Bottom Trawl Net is used to trawl for fish. This net is a large net equipped with rubber bobbins that allow it to get close to the benthic region of the ocean without dragging.

During this research expedition, we used the PNE net six times to survey pollock. Often times these trawls brought up other interesting sea life, that were quickly assessed (identified, measured, and recorded) and returned to the ocean. The majority of invertebrate sea animals such as poriferans (sponges), cnidarians (sea anemones), annelids (segmented worms), mollusks (barnacles), arthropods (hermit crabs hiding in mollusk shells), and echinoderms (sea urchins and starfish) were brought up in these hauls. In addition, some interesting species of fish (see this blog’s Trawling Zoology segment below) were gathered in bottom trawls.

Miscellaneous Invertebrates from Bottom Trawl

Using the Methot Trawl

We use the Methot trawling net to sample krill, a type of zooplankton that pollock feeds on. On this voyage, the Methot was used 6 times as well. The Methot is a single net with a large square opening or mouth. The net is deployed from the stern and towed behind the vessel. Inside the Methot is a small removable codend where much of the catch is deposited.

The krill is measured and counted as well. First, the water is drained out, then it is weighed, and a small sample is weighed and counted.

Bottom trawls and Methot trawls are both important aspects of the pollock survey.

Personal Log

Accomplishment

Continuing with Maslow’s hierarchy of needs, I will discuss the top part of the pyramid, how self-actualization, or being involved in creative endeavors to expand one’s full potential, are met on the Oscar Dyson.

A Version of Maslow's Hierarchy of Needs — A Version of Maslow’s Hierarchy of Needs

Since I am an honorary member of the am science team, I am privy to many discussions between the scientists on the team regarding a variety of topics. For example, one side project on the mission is to gather information regarding the abundance and distribution of euphausiids (krill) in the Gulf of Alaska. This research project involves the use of a smaller “critter camera,” engineered and built by two of the MACE (Midwater Assessment and Conservation Engineering) group members, to take pictures of krill at various ocean depths and (ideally) reconcile its distribution with acoustic and Methot trawl data. The goal of the project is to provide insight into the feeding conditions of pollock. The discussions between group members involve postulating, speculating, testing, theorizing, analyzing, teaching, and questioning; clearly this meaty dialog indicates that the process of science is an intellectually stimulating and creative endeavor.

Scientist Team Members--- Abigail, Patrick, and Kirsten---Engaged in a Stimulating Discussion — Scientist Team Members— Abigail, Patrick, and Kirsten—Engaged in a Stimulating Discussion

Did You Know?

One of the people who views my blogs before they are posted is the Executive Officer (2nd in Charge) of the crew on the Oscar Dyson. His name is Chris and on this mission he is “augmenting” or filling in for another employee. Chris administers the day-to-day operations of the crew including logistics, payroll, and travel. Chris is a member of the NOAA Corps; he has both a BS in Marine Biology and an MS in Management Information Systems from Auburn University located in Auburn, Alabama. He grew up in various places in the Midwest (his dad was in the U.S. Airforce) and has worked in several fields including information technology and zookeeping. He applied to the NOAA Corps because he wanted to live and work near the ocean.

Chris, the Executive Officer of the Oscar Dyson — Chris, the Executive Officer of the *Oscar Dyson*

Something to Think About:

In previous posts, we have explored invertebrates encountered on this mission. Today we will look at a group of vertebrates from the class Osteichthyes, a word that comes from the Greek osteon meaning “bone” and ichthus meaning “fish.” We will focus on some of the other fish besides pollock found in bottom trawls. These bottom-dwellers are quite interesting creatures.

One of the most frequently found fish, other than pollock, is a type of rockfish called the Pacific Ocean Perch (POP); the species name is Sebastes alutus (Greek: Sebastes “August, venerable”, alutus “grow, nourish”). This fish actually was seen in many trawls, both mid-water and bottom. As the picture below indicates, the body and fins of the POP are light red; however, there are dark olivaceous areas on back under soft dorsal fin and on the caudal peducle. The maximum length of the fish is 55 cm and it is commonly found at a depth between 100-350 m.

Pacific Ocean Perch (a type of Rockfish)

A fish that belongs to the same genus as the POP is the Tiger Rockfish, Sebastes nigrocinctus ( Latin: niger, “black” and cinctus, “belt”). We found this fish once in a bottom trawl. The bottom of the tiger rockfish is light red to orange with several broad, vertical black-red bands on body. It grows to a maximum length of 61 cm and is commonly found at a depth between 55 to 274 m. Notice how similar it looks to the POP.

Tiger Rockfish, notice the similarities to the Pacific Ocean Perch

One of the most colorful fish that was found in a bottom trawl was the kelp greenling, Hexagrammos decagrammus (Greek: hexa, “six”; grammus, “letter, signal”, deca, “ten”), a fish that generally hangs out in rocky reefs and kelp beds in relatively shallow waters (up to 46 m). The fish is olive brown to bluish grey, speckled with irregular blue spots if male and reddish brown to gold spots if female (those we caught were most likely female). The fish reach a maximum length of 53 cm.

July 4, 2010April 15, 2021

Michele Brustolon, July 4, 2010

NOAA Teacher at Sea
Michele Brustolon
Onboard NOAA Oscar Dyson
June 28 – July, 2010

NOAA Ship Oscar Dyson
Mission: Pollock Survey
Geographical area of cruise: Eastern Bering Sea (Dutch Harbor)
Date: July 4, 2010

Weather Data from the Bridge

Time: 1500
Latitude: 57.59N
Longitude: 171.10W
Cloud Cover: 100%
Wind: 11 knots
Air Temperature: 7.20 C/ 44.960 F
Water Temperature: 5.50 C/ 41.90 F
Barometric Pressure: 1010 mb

Science and Technology Log

Now that I have provided you with information about the importance of pollock and how the Oscar Dyson works to survey the stock in the Eastern Bering Sea, I wanted to answer a few related questions.

What about other species?

In the Bering Sea, pollock are so abundant that our mid-water trawls capture mostly pollock. However, there are a lot of other species in the Bering Sea that scientists are interested in. In addition to the Oscar Dyson, NOAA charters fishing boats (such as the Alaska Knight and the Aldebaron) to trawl on the ocean floor. This allows scientists to see more species in the Bering Sea. These ships trawl all day; sometimes up to 6 trawls a day. The GF boats cover the eastern Bering Sea shelf, extending up to the region around St. Lawrence Island (a wider area than the Oscar Dyson will cover). While the Oscar Dyson focuses on euphausiids and pollock, the ground fishing boats examine everything else found on the bottom.

brustolon_log4_img_5 — Euphausiids from Methot trawl

brustolon_log4_img_6 — Katie proudly holding a pollock from our first Aleutian wing Trawl

Who owns the water?
International laws provide countries with an Exclusive Economic Zone (EEZ) within 200 miles of their shoreline. The area we are studying in the Bering Sea can be fished solely by fishing boats operated in the United States. On the other side of the Sea, Russians fish in their own 200-mile zone. However, in the middle there is a “donut hole” which is considered “international waters”. This Donut Hole supported a large pollock fishery in the late 1980’s.

brustolon_log4_img_1 — Transects for Leg II on Oscar Dyson

brustolon_log4_img_2 — The “Donut Hole” or “Bubleek” in Russian, is shown here in the shaded circular area between U.S. and Russia.

How do American scientists collaborate with scientists from other countries?
The United States works with other Pacific countries to conduct research on the Pacific Ocean and the Bering Sea. For example, the Oscar Dyson, in addition to hosting two Teachers at Sea, is hosting two Russian scientists from the Pacific Research Institute of Fisheries and Oceanography (TINRO) in Vladivostok, Russia – Mikhail Stepanenko and Elena Gritsay.

I had the opportunity to sit down with Mikhail the other night and asked him about his experience and how he ended up on the Oscar Dyson. Born and raised in Primorye, Mikhail spent a great deal of time at the Ussuri River. He studied biology at The Far East State University in Vladivostok and began researching at sea soon after his graduation in 1968. After the first USA-USSR agreement regarding marine research, Mikhail visited the United States and worked out of La Jolla, CA starting in 1969. He has spent about 5-6 months at sea per year for the last 40 years, including the last 18 summers on the NOAA summer pollock survey (specifically on the Oscar Dyson and its sister ship the Miller Freeman)

This wealth of experience has made Mikhail an expert and he is a well-respected member of the Pacific marine science community. Throughout the years, there have been numerous conferences between stakeholder countries, and Mikhail has played an active role in recommending action for working together to maintain the populations of pollock and other fish. Mikhail has served on the Intergovernmental Consultative Committee – a six-nation committee that meets biannually to discuss fishing polices in the “donut hole.” In addition, Mikhail worked as a Russian delegate during meetings which led to the creation of PICES (North Pacific Marine Science Organization), an “intergovernmental scientific organization, was established in 1992 to promote and coordinate marine research in the northern North Pacific and adjacent seas.” (Visit their website for more information). Mikhail was elected Chairman of the Fisheries Science Committee (FIS), a branch of PICES, in 2008 and is currently preparing for their next meeting in October.

Each organization is trying to find the best policies to help understand the organisms through reproduction, population dynamics, stock assessments and fishery management. Mikhail’s wealth of knowledge, collaborative scientific research and commitment to the sustainable fishing benefits all members of the international community and we are lucky to have such a science superstar in our midst.

brustolon_log4_img_3 — Catch of jellyfish and pollock coming in (Abby: left; Kathy: right)

brustolon_log4_img_7 — This is a lumpsucker. Isn’t it cute?

PICES website: http://www.pices.int

Personal Log

The Fourth of July ending up being a packed day! First thing I was able to help with the CTD (remember from previous journals- conductivity, temperature, depth). You definitely wake up standing on the Hero Deck at 0400! My day of adventure continued when we got to fish after lunch. Why was this such a big deal? We hadn’t fished since June 30! We saw 100s of pounds of Chrysaora melanaster (jellies) that were so large we had to struggle to move them. We focused more on the pollock that were 1-3 years old this trawl, but the COOLEST animal by far was the lumpsucker! I was able to help sort the pollcok, sex them, and take the otoliths out for research. After we cleaned up the wet lab, we had a great ending to our day…

We had a cookout on the Boat Deck. Ray, the Chief Steward, with the help of Floyd Pounds, 2nd Cook, made everything you could possible imagine: a variety of kabobs, cheese burgers, salmon, different salads, cake, fruit, and the list goes on. To top the evening off (remember, it’s still light out!), Ensign (ENS) Amber Payne gathered and shot off expired flares for our “light show.” I enjoyed having the time to hang out with some people that I never see now that we are all working our shifts. It is a Fourth of July that I will remember always!

brustolon_log4_img_4 — Fourth of July cookout on the Boat Deck

Animals Seen
brown jellies or northern sea nettle- Chrysaora melanaster
pollock- many 1-3 years
smooth lumpsucker
rock sole
fulmars

Word of the Day
Propiate: appease
New Vocabulary
GF boats: ground fishing boats
“Donut hole”: the area between Russia and the U.S. that was considered International waters” so it did not belong to a certain country

June 17, 2010March 12, 2021

Richard Chewning, June 17th, 2010

NOAA Teacher at Sea
Richard Chewning
Onboard NOAA Ship Oscar Dyson
June 4 – 24, 2010

NOAA Ship Oscar Dyson
Mission: Pollock Survey
Geographical area of cruise: Gulf of Alaska (Kodiak) to eastern Bering Sea (Dutch Harbor)
Date: June 17, 2010

Weather Data from the Bridge

Position: north of Dutch Harbor
Time: 0830
Latitude: N 54 58.080
Longitude: W 165 58.080
Cloud Cover: cloudy with fog
Wind: 20 knots from SW
Temperature: 6.9 C
Barometric Pressure: 1007.9 mbar

Science and Technology Log

In addition to the Tucker trawl, fish biologists onboard the Dyson also utilize the Methot trawl to catch zooplankton in their study of pollock. The Methot is a single net with a large square mouth (the opening of the net) that is deployed from the stern and towed behind the Dyson. The Methot uses fine mesh with openings slightly larger than the Tucker trawl. This larger mesh size allows the net to be towed at higher speeds. A torpedo looking instrument called a flowmeter is suspended in the mouth of net to measure the flow of water moving through the net. The flowmeter allows the researchers to calculate how much zooplankton is found in a certain volume of water. With its larger mouth and faster speed through the water, the Methot is able to catch the larger zooplankton such as euphausiids the Tucker trawl might miss. Pollock seem to love euphausiids as I have seen firsthand stomachs of pollock caught during Aleutian wing trawls that have had stomachs stuffed with euphausiids.

chewning_log7_img_1 — Deploying the Methot trawl

chewning_log7_img_2 — Recovering the Methot trawl

After the Methot is return onboard, the sample is rinsed and poured through a strainer to separate the zooplankton from smaller algae and phytoplankton. After being weighed, a small subsample is removed and preserved for later identification. The number of euphausiids in a second subsample is counted to calculate the total number in the catch. Several individual euphausiids are also frozen so they can later be analyzed for age and development by examining their eye stalks. In addition to catching the small zooplankton pollock eat, the Methot will also catch some of the largest zooplankton in the ocean: jellyfish. Almost all the Dyson’s trawls have yielded large number of Chrysaora melanaster jellyfish. After being removed from the sample, these jellyfish are also weighed and measured. These jellyfish produce only a mild sting but can be quite frustrating to process in large numbers.

The Dyson has also been routinely deploying a piece of equipment known as a CTD (conductivity-temperature-depth recorder). This instrument package allows scientists to measure temperature, depth, dissolved oxygen, chlorophyll, light intensity and conductivity. By measuring conductivity (the amount of electricity carried by seawater), salinity can also be calculated, and from temperature and salinity, density can be calculated. The CTD is deployed once every night before dawn and during selected locations during the day. The CTD is attached to a metal frame called a carousel along with other pieces of scientific equipment. Niskin bottles can be attached to the carousel allowing the recovery of water samples from different depths. The Niskin bottle is a vertical plastic tube that is initially deployed with both ends open allowing seawater to flow through. Once the CTD is lowered to the desired depth, the bottle is ‘fired’. Firing signals the bottle to close the openings, sealing the water sample inside. This water can be brought to the surface and filtered to measure the amount of chlorophyll it contains. By better understanding how the properties of seawater such as temperature and chlorophyll concentration relate to the various biological organisms that form the foundation of the Bering Sea ecosystem, researchers can better understand pollock distribution and abundance.

chewning_log7_img_4 — Recovering the CTD

Personal Log

After getting to know the crew over the last week and a half, I have noticed most have a passion for the great outdoors and enjoy a wide range of physical activities such as hiking and skiing when not at sea. Most enjoy hunting and fishing and several enjoy competitive events such as running and cycling. You would think staying active while sharing a platform only 208.6 feet long and 49.2 feet wide with up to 40 people might seem like a daunting task, but this is surprisingly not the case. I have noticed most of crew members from the CO (the commanding officer) to the guest scientists have dedicated time in their schedule to keeping physically fit.

The deck crew has an upper hand in this endeavor as their work often involves moving heavy lines, chains, and gear. Their labor is aided however by powerful hydraulic winches that can lift even the heaviest objects with ease. The Dyson’s acting XO (executive officer) Lieutenant Sarah Duncan was also willing to suit up in her foul weather gear and life vest to give the deck crew an extra set of hands with two late night pollock trawls. Besides the physical workout of retrieving the gear, she told me that working down on deck gives her better appreciation for how the deck crew is affected by the ship’s movements and weather conditions when deploying and retrieving gear. This is very valuable information for Sarah for when she is high in the bridge working hard to direct the ship’s movement so the deck crew can work efficiently and safely in different weather conditions and sea states.

Maintaining one’s physically fitness benefits every member of the crew regardless of station as rough seas can wear the body down physically and mentally in a very short period of time. The rowing machine seems to be the first choice among the crew although the stationary bike and elliptical machine are also popular. The treadmill is the most challenging workout as you are constantly being thrown off balance. I can’t help but wonder what prisoners chained to the oars of wooden ships of old would think knowing that mariners today use large mechanical engines to power the ship and use stationary rowing machines for exercise!

chewning_log7_img_5 — Measuring Chrysaora melanaster jellyfish

chewning_log7_img_6 — Holding Chrysaora melanaster jellylfish

Did you know? The word ‘plankton’ and ‘planet’ come from the same root word? Both names come from the Greek word planktos that means ‘wander’. Plankton is any plant or animal not strong enough to swim against water currents. Examples include diatoms, dinoflagellates, copepods, and euphausiids. Planets were named because they were observed by early astronomers to drift or wander among the stars. Stars appear to maintain the same spatial relationships with each other as they rotate across the sky because they are located so far away. Although they are actually moving, their position in relation to each other appears to be unchanging. This is the reason why the same constellations (pattern of stars in the sky) have been identified throughout human history. Planets on the other hand move through the star field as they are very close in comparison and are orbiting the sun. Thus planets appear to wander among the stars just like plankton drift among the currents of the ocean.

chewning_log7_img_7 — Saving a euphausiid sample

July 26, 2007April 1, 2021

Roy Arezzo, July 26, 2007

NOAA Teacher at Sea
Roy Arezzo
Onboard NOAA Ship Oscar Dyson
July 11 – 29, 2007

Mission: Summer Pollock Survey
Geographical Area: North Pacific, Alaska
Date: July 26, 2007

Weather Data from Bridge
Visibility: 8-10 nm (nautical miles)
Wind direction: 220° (SW)
Wind speed: 11 knots
Sea wave height: 3 feet
Swell wave height: 0 feet
Seawater temperature: 10 °C
Sea level pressure: 1014.9 mb (millibars)
Air Temperature: 10°C
Cloud cover: 8/8, Stratus

Roy works with the deck crew to remove the “pea pod” from the trawl net.

Science and Technology Log: Special Operations

When a fully equipped research ship goes to sea everybody wants in. Any scientist doing work in a particular region needs access to that region to conduct their fieldwork. Fishery scientists often catch a ride with commercial vessels to do work at sea. A research vessel can be more desirable for certain projects and NOAA has a system for organizing request proposals and prioritizing work. Unfortunately, a boat is limited in the number of passengers, equipment, food and other resources it can carry. For example one scientist, who is not with us, has sent light meters onboard and requested we collect the data for him. The light meter mounts to our trawl net to study if light penetration affects the vertical distribution of walleye pollock. The pollock survey, the main project of the season, has a science team of 8 not including the birders, ship’s staff and Teacher at Sea. With this many scientists onboard the ship becomes a platform for an interesting mix of experimentation.

We finished the transects of the Pollock Survey and are now transiting southeast back towards Dutch Harbor. Tomorrow we launch “the sled”, a large metal-framed instrument equipped with an underwater video camera to record the sea bottom of a special study site. The purpose of the study is to assess the effect of bottom trawling on benthic habitats and measure recovery progress over time. The study site is an area that was bottom trawled back and forth around a month ago. The camera will be pulled in lines perpendicular to the tracks created by the trawling. I got a sneak peak at some of the video footage and the benthic habitat is flat and muddy with strange white sea pens poking upward around 5 feet. Crabs and flat fish scurry around while giant basket stars and sea anemones ornament the bottom. We will use some of our transit time to reflect on some of other side projects that occurred this trip, most of which were designed to refine and validate the survey methodology.

When the trawl catch is unloaded into the lab the sex, weight and length of individual fishes are recorded. To make the work more efficient, a new measuring board has been designed to length fish. This is the first time it was tested and it performed smartly. The board allows scientists to input digital length data by touching the sensor to the board at the end of the fishtail fork. NOAA Scientists, Rick Towler and Kresimir Williams, designed the instrument using magnetic sensors from scratch, and shared with me the details of their first project and how the length board evolved from an acoustic instrument through trial and error to the prototype we tested this year. When processing data from trawling, there is always a concern as to how to best represent biomass estimates. You should not count a fish that is 10 centimeters the same as you would a fish that is 40 centimeters. Although they would both qualify as one fish they have a different size and thus a different biomass. We know we cannot count every fish so we have different methods of estimating biomass.

Deck crew works to get fish out of the pocket nets

Not all fish are caught with the same efficiency; the retention of fish in a net must be taken into consideration. To compensate for this, an estimate as to fish escapement is often factored into the calculations for fish density. Fisheries Scientist, Kresimir Williams, wants to quantify fish escapement. He is using handmade “pocket nets” to study selectivity and sample escaped fish. In the evening we conducted experimental trawls to monitor escapement from our main trawl nets. We did this by attaching pocket nets to the outside of the trawl net in random placement and analyzing pollock caught in the smaller nets relative to the catch in the cod end. We have found that smaller fish (one year-old juveniles) more often escape the net from near the cod end as opposed to forward, where there is a larger mesh size. Although the data will not be analyzed until later, observations indicate this could be important in interpreting pollock survey results.

The “peas” are equipped with digital cameras

The most exciting project for me is the “Optical Pea Pod”, another Kresimir/Rick design. The pod houses 2 digital cameras, a timed circuit board and a strobe light that is lowered in the net to photograph fish at regular intervals. The setup is designed to produce calibrated stereo images of fish making it possible to measure fish length in deep water. Perhaps, in the future, the cod end can be left open allowing the fish to swim out safely as they are documented. The imaging data can possibly be used to verify the acoustic data that is currently used to estimate the population, reducing the need to handle fish on deck. I would like to thank my technical advisors, Kresimir and Rick, for involving me in their projects and for their support in my work as Teacher at Sea.

Bird of the Day

Adrienne and Travis test the empty peacameras pods for pressure down to 80 meters — Adrienne and Travis test the peacameras for pressure down to 80 meters

The Albatross is a seabird steeped in maritime folklore. Mariners of yore would tell stories of the souls of dead sailors rising when they saw the white bird. Famous for being one of the largest seabirds they are a magnificent sight. The Wandering Albatross is capable of extremely long migrations, circumnavigating the globe for years before settling down to breed. Albatrosses, of the biological family Diomedeidae, have recently been reclassified (based on recent DNA evidence) and the number of genii and species is widely disputed. What is clear is that many species are in danger of extinction. The greatest impact to their populations is long line fishing although many were slaughtered for their feathers before being protected after the turn of the last century. Swordfish, monkfish and cod are fished with long-lines involving miles of baited hooks that can attract the birds and lead to their entanglement and subsequent drowning. We have seen two species on this cruise, the Laysan and the Short-tailed Albatross. It is estimated that there are only between 1500 and 2000 Short-tailed Albatrosses remaining the world. Many were harvested for feathers and a volcano eruption at their Japanese breeding grounds decimated the remaining adults. Fortunately juveniles at sea have returned to breed and hopefully with protection, the numbers will continue to rebound. We were lucky to have one spend a fair amount of time of our stern in calm waters the other day as we were stopped for water quality testing.

Rick spends most of the sail tweaking the electronics and the software for things to work. In an attempt to upgrade the failing batteries of the strobe light he designs a super-battery housed in a milk carton.

Personal Log

The Bering is a surprisingly lovely color of blue and if the sun would ever come out I am sure it would accent the aesthetic of the water’s color. When we stop to check the water quality the CTD instrument makes for a decent secchi disk and I have observed anecdotally that the visibility seems to be around 13 meters or 40 feet. On an unrelated topic, the other day Executive Officer LT Bill Mowitt let me in on his “lesson plan” for the weekly drill. We went into a fan room and created an electrical fire scenario. We also left clues around the area for the crew and fire fighter team to assess and react to. When it came time for the actual drill I had front row seats to watch the drill unveil and was then permitted to test the fire house of the leeward side the ship. All went well.

Question of the Day Today’s question: How much fish did we catch? Previous Question: How does one become a Golden Dragon?

The short answer is one sails across the 180-degree line separating the eastern and western hemisphere. We did this going steaming to Russian waters continuing our survey work in the Northwest Bering.

Kresimir and Rick send the final prototype of the pea pod down in the trawl net

Pollock in the net down below 80 meters – caught and measured on camera

Another amazing in-flight shot by Tamara K. Mills

An Immature Short-tailed Albatross off the stern of the OSCAR DYSON (image by Mark Rauzon).

Executive Officer Bill Mowitt sets up a Fire Drill

July 23, 2007April 1, 2021

Roy Arezzo, July 23, 2007

NOAA Teacher at Sea
Roy Arezzo
Onboard NOAA Ship Oscar Dyson
July 11 – 29, 2007

Mission: Summer Pollock Survey
Geographical Area: North Pacific, Alaska
Date: July 23, 2007

Weather Data from Bridge
Visibility: <1 nm (nautical miles)
Wind direction: 220° (SW)
Wind speed: 8 knots
Sea wave height: <1 foot
Swell wave height: 0 feet
Seawater temperature: 9.8 °C
Sea level pressure: 1006.7 mb (millibars)
Air Temperature: 10°C
Cloud cover: 8/8, fog

Roy and Tamara get excited about birding on the bridge of the OSCAR DYSON

Science and Technology Log

Consumers became very aware of the issue of by-catch when the media reported the canned-tuna industry was killing dolphins in their nets nearly a decade ago. The industry responded by changing some of their fishing methods and marketing “dolphin-safe tuna”. NOAA monitors and sets catch limits for commercial fishing, regulating by-catch, among other things. The Coast Guard assists by also enforcing these fishing regulations. Some of the scientists working here on the pollock survey have worked as fishery observers on commercial vessels, monitoring by-catch in the Alaska fleets. The by-catch regulations vary based on the region, species and season. For example, on the Bering Sea none of the finfish outfits are allowed to keep any crab, they need a special permit to keep halibut and they need to keep cod if they are fishing for pollock. Commercial trawling for pollock results in typically low by-catch. Some environmental groups have listed pollock as a sustainable fish food compared to other seafood in that the harvest does not seem to significantly harm the environment or severely deplete fish stocks. The Marine Stewardship Council, an independent global nonprofit organization, has certified Alaskan pollock as a sustainable fishery.

NOAA Scientist Abby separates out Chrysaora melanaster, common name Lions Mane. — NOAA Scientist Abby separates out a Chrysaora melanaster jellyfish.

Although we are not dealing with by-catch directly, I find the connection between by-catch, sustainability and fish stocks very interesting. The Echo Integration Trawl Survey uses acoustic data to estimate pollock populations. When we put out our nets we do so to obtain a sample of fish, detected by our acoustic instruments. Since we are conducting mid-water trawls we bring up mostly pollock. The non-pollock species that occasionally get caught in the net are important in verifying the acoustic data and to know what is in the water column with the target species. As a science teacher, the diversity makes for interesting fishing and I have been able to observe a few organisms that spend most of their time in deep water. I have shared some of my images of the unusual species below, all of which I had never seen before this trip. Many of the organisms we bring up go back into the water after we record the data but some of our catch makes it to the galley to be served up for meals.

More Invertebrates

Flathead Sole (Hippoglossoides elassodon). Flatfish tend to swim higher in the water column in the evening following the plankton

Greenland Turbot (aka Greenland Halibut)

Great Sculpin (Myoxocephalus polyacanthocephalus)

Smooth lumpsucker (Aptocyclus ventricosus)

Kier, Chef and Assistant to the Chief Steward, makes a serious shrimp bisque.

Catch of the day: Chief Steward Rick cooks up Pollock Fish and Chips

Bird of the Day: Turns out, there is no such thing as a seagull. This was passionately explained to me by birder who will remain nameless. You ask, why no seagulls? Simply the term is not used in the scientific community. There are seabirds and of this general group there are well over 100 species of gulls. Some gulls are found well inland. Some species of land-based gulls have become popularized due to their opportunistic feeding around humans. Many of the pelagic gulls I have seen this trip are not as well trained as the ones in NYC and stick to wild foods, not even accepting the occasional fish scraps I have tempted them with off the back deck. I had reported in a previous log seeing Kittiwake’s and some immature Herring Gulls. Today we saw a Slaty-back Gull. It is a handsome gull with striking contrasts of black, dark grey and white. They seem to turn up more each time we reach the northern end of a transect line (above 60° latitude). I also learned that the red spot on the beak is a sign of maturity in many adult gulls. I have a renewed appreciation for gulls and look forward to identifying the species back home.

Bottom trawls, conducted on the previous leg of this study, tend to have more diversity in the sample

Personal Log

We are approaching the northwestern edge of our transect field and the water is deeper and colder and we are finding less fish. I am lucky to find more time to spend on the bridge and witness the communication with Russian fishing vessels, jumping salmon and occasional marine mammal sightings. I have a little camera envy. Some of the folks aboard have the right lens and the right camera to catch the action out at sea. My little 4X zoom digital is looking mighty bleak on the deck and thus I need to rely on the serious photographers for images of some of these exciting finds; their generosity in sharing their images is most appreciated.

Question of the Day

Today’s question: How does one become a Golden Dragon?

Previous Question: Why do pollock rise in the water column at night?

Much of the food eaten by pollock fluctuates in their vertical migration depending on light penetration. During the daylight hours many of the euphausiids (krill) can be found lower in the water column. It seems that by staying lower in the darker portions of the water column during the day, zooplankton may be more protected from their major predators. Near the surface, the phytoplankton (algae) uses the sun’s energy to produce food all day. As the light fades the zooplankton rise, feeding on algae, and the pollock follow their food source.

Krill from one of our nighttime raids with the Methot Trawl

Krill (pollock food): Partially digested from inside the stomach of a pollock

Pollock gill rakers screen food from leaving the oral cavity as the water passes out of the gill slits, oxygenating the gills

July 19, 2007April 1, 2021

Roy Arezzo, July 19, 2007

NOAA Teacher at Sea
Roy Arezzo
Onboard NOAA Ship Oscar Dyson
July 11 – 29, 2007

Mission: Summer Pollock Survey
Geographical Area: North Pacific, Alaska
Date: July 19, 2007

Weather Data from Bridge
Visibility: 10+ nm (nautical miles)
Wind direction: 270° (SW)
Wind speed: 11 knots
Sea wave height: 5 foot
Swell wave height: 5feet
Seawater temperature: 8.1°C
Sea level pressure: 1004.4 mb (millibars)
Air Temperature: 9.7°C
Cloud cover: 6/8, stratus

NOAA’s Lieutenant Commander D. ZezulaReading the chart of the North Bering Sea — NOAA Lieutenant Commander D. Zezula reading the chart of the North Bering Sea

Science and Technology Log:

I would like to thank David J. Zezula, Lieutenant Commander for NOAA and Alaska Region’s Navigation Manager, who spent over an hour showing me charts and resources for my school. David is serving as a relief officer of the deck aboard the OSCAR DYSON. Around our second Transect this leg we needed to break off from our line momentarily to avoid some shallow pinnacles listed on the chart. Of the three, one pinnacle is charted in deep water and the tall thin pinnacle seems an unlikely seafloor feature. I was surprised to learn that the information on the printed chart was different from the digital GLOBE program the scientists use to assess the bottom. It was indicated on the printed chart that these shallow regions were charted back before we started making seafloor maps using multi-beam sonar technology. The actual depth in that region is thus questionable and rather than sail over what seemed like deep enough water we cruised around it for safety precautions. Our draft is about 29 feet and all of sensors are located on the centerboard that extends down below the hull’s lowest point. As a research vessel we care very much about our sensors.

Long-tail Jaeger photographed off the bow of OSCAR DYSON by Tamara K. Mills

I asked David about this and he went to his files and was able to show me more information about the dates and background on that specific chart. Some of the archives he has access to were actually scanned from hand written charts created with lead lines back at the turn of the century. One of the main parts of his job back on land is to help prioritize what regions of Alaskan waters are to be updated with modern technology as part of NOAA’s Office of Coast Survey (the hydrographic and nautical charting division of NOAA). Obviously they focus on key ports and channels first but there is much water out there to chart and verify.

Bird of the Day: Today I was fortunate to see yet another “new to me” species. The Long-tail Jaeger (Stercorarius, longicaudus) is a pelagic seabird that rules the air. Although it probably eats some fish near the surface it is famous for its aerial piracy. It is a very muscular bird that is capable of upending flying birds forcing them to regurgitate their stomach contents to obtain a meal. This is currently their breeding time so it is early in the season for them to be found this far out at sea but soon mature adults and their grown offspring will be out on the Bering looking for food before their winter migration to the south. I keep missing the albatross sightings and hope that it will be my next bird of the day. Information provided courtesy of Mark Rauzon, birder, author, educator and friend.

Personal Log

Land! It was very exciting to see land for many reasons. First, the sun was out, a rare treat on the Bering. Many of the weather entries above will list the cloud cover as 8/8, which means out of 8 parts of sky all of it is covered by clouds. Also the visibility was good and the seas, which turned up with some high winds last night, had calmed down considerably. Lastly we were looking at Russia, many of us for the first time, which made sense since we were in the north part of our third transect line in Russian waters. It was also the first time we have seen land since we left Dutch Harbor. Cape Otvesnyy, at 860 meters high was visible from about 63 miles away. We all went outside the bridge to take photos and celebrate.

Question of the Day

Today’s question: Why do pollock rise in the water column at night?

Previous Question: How is the field of acoustics used in science?

OSCAR DYSON’S deck crew attaches an acoustic device (yellow) to the fishing gear

Acoustics is a huge area of technology that ranges from how we design theaters to the use of sonograms to view unborn children. Much of the acoustic technology used in science has to do with creating alternative ways to observe different environments. Light does not travel through water as far as sound (vibrations). Sound waves are the key to looking deep into water. Marine mammals know this and can find prey with echolocation, reading reflected sound waves they send out to locate food and communicate.

On OSCAR DSYON we use several types of acoustic instruments

The Simrad EK60 is our main fish counting instrument and it uses about a 7º beam to send out sound waves of different frequencies and receive echoes from organisms and objects of different sizes. It is mounted on the centerboard and reads information from 5 frequencies ranging from 18 to 200 KHz. As we run along our transect line the data that is received is used to estimate the fish density. The scientists onboard spend a fair amount of time checking to see that the echoes actually represent pollock.

The ME70 Multi-beam is mounted to the ship’s hull and is a powerful tool in creating a wide swath three-dimensional image of what is below the ship. This is especially useful in hydrographic work that involves charting and mapping the seafloor bottom but it may be used for the fish survey in the future. The Acoustic Doppler Current Profiler (ADCP) is also connected to the centerboard and uses the Doppler Effect (the change in frequency and wavelength of a sound pulse as perceived by an observer moving relative to the source of the sound) to estimate current and fish speed.

We place a Net Sounder (FS70, affectionately known as the turtle) on to our fishing n each time we trawl. Like scientists, commercial fishermen often use this instrument to monitor the shape of the net opening and the amount of fish entering the net. It does this by sending a 200 kHz frequency beam across the opening of the net and transmits data along a cable for the team to see on our monitors. Along with the turtle we send down a Simrad ITI, which is smaller and wireless but a lower resolution net sounder that is used as backup in the event we have trouble with our cable.

The DIDSON (Dual Frequency Identification Sonar) is an instrument that has been developed for divers in low visibility water and has many industrial applications. It creates an image typical to the one seen on sonogram tests. It uses a high frequency beam (up to 1.8 MHz) to achieve a short-range image (up to 50 meters). It has been applied to salmon return rate studies and has well enough resolution to make out the shape of a moving fish. The pollock survey team has been experimenting with it as a way to monitor fish escapement from the net and how fish behave within the net.

In our survey work most of our mid-water trawls occur between 17 and 700 meters. The acoustic technology is vital to verify fish at these depths.

July 16, 2007April 1, 2021

Roy Arezzo, July 16, 2007

NOAA Teacher at Sea
Roy Arezzo
Onboard NOAA Ship Oscar Dyson
July 11 – 29, 2007

Mission: Summer Pollock Survey
Geographical Area: North Pacific, Alaska
Date: July 16, 2007

Weather Data from Bridge
Visibility: 8 nm (nautical miles)
Wind direction: 260° (SW)
Wind speed: 6 knots
Sea wave height: 1 foot
Swell wave height: 3 feet
Seawater temperature: 9°C
Sea level pressure: 1014.4 mb (millibars)
Air Temperature: 8°C
Cloud cover: 8/8, stratus

Science and Technology Log: Why fish pollock? What do pollock fish? Pelagic Food Webs of the Bering Sea

Surveying pollock on the Bering shelf provides the data needed to set catch limits to manage the fishery. Catch limits for American fishing fleets are to be decided soon for next year. The pollock survey I am part of as Teacher at Sea is technically known as the Echo Integration Trawl Survey been an annual tradition of NOAA since 1971! The OSCAR DYSON, and before her the MILLER FREEMAN, use traditional trawling gear to achieve this goal. The fishing gear tends to be smaller then the larger fishing vessels since we don’t need to catch as many fish to estimate population trends. Like commercial operations we are interested in where the fish are in the water column and their geographic distribution. We also are concerned with their age composition. Although we primarily use acoustic sensors to detect fish, by trawling we can see how the technology used to locate fish in the water matches with what is being caught in the net. We also monitor by-catch organisms to observe what is mixed in with pollock when trawling.

Dutch Harbor, AK, according to the National Fisheries Service continues to be the No. 1 port by weight for seafood landings. In 2005, 877 million pounds of seafood passed through port, in 2006 it was more. In terms of seafood value only New Bedford, Mass., surpasses Dutch Harbor mostly due to the increase in the scallop market and decrease in crab populations. Dutch Harbor is known for its king crab industry in the winter and finfish year round, including hake, cod and salmon. Although shrimp is American’s most popular seafood item in terms of sales, finfish occupy much of the top five. Canned tuna is second highest for sales in the U.S., salmon is third and then pollock and tilapia; however if you factor in the global market, the amount of pollock being harvested and the sales for food products such as frozen whitefish foods, filets and surimi (Asian fish paste used in foods such as artificial crab) make it the largest seafood industry in the world (Anchorage Daily News). In addition Pollock are seasonally fished for roe. Commercially, fishing pollock is a good business venture due to its large schools and typically low by-catch. According to the National Marine Fisheries Service approximately 307 million dollars in pollock sales was made in the U.S in 2005. More than 3 million tons of Alaska pollock are caught each year in the North Pacific from Alaska to northern Japan. Of that the U.S. is responsible for about half. The population of Pollock in the Bering alone was estimated at 10 million metric tons early this decade and the catch limit was set around 10 –15% of the population size. Last year the survey team found a significant decline in populations and thus the catch limit was lowered but anecdotally there are preliminary signs of good recruitment with many young pollock being identified in this summer’s survey.

We are clearly at the top of the food web and consuming a large amount of pollock. The pollock are part of a very complex ecosystem. They are fragile fish and short lived but fast growing and quick to reproduce. The pollock population seems to be greater in number then most other harvestable finfish in the Bering, possibly due to a decline in Pacific Ocean perch, and shows interesting fluctuations in population density in response to global climate changes and sea current patterns. The Bering Sea lies between the Arctic Ocean to the north and the North Pacific to the south but remains a unique ecosystem exhibiting some characteristics of each of its neighbors.

Jellyfish found in the plankton net - large plankton! — Jellyfish found in the plankton net – large plankton!

The food web of the pelagic zone of open water in the cold Bering Sea is contingent on movement of nutrient rich waters. The main source of nutrients for the upper shelf region where one finds pollock seems to be influenced by the flow of the Alaskan Stream near shallower coastal waters which flows east across the Aleutian chain. Some of the water flows up through passes and becomes parts of currents like the Aleutian North Slope Current that feed the shelf. The Bering Sea is an extremely large and a relatively shallow body of water making it very different and it is this nutrient flow between shallow waters of the coast and shelf and deep basin/trenches to the west and south that account for its high biodiversity. In addition to currents ice melt and water temperature greatly affects nutrient flow and productivity. The nutrient rich water enables phytoplankton to flourish and reproduce in otherwise cold barren water. In turn zooplankton feed on the phytoplankton which transfers the organic carbon foods from producers to other levels of the food web. Invertebrates (ex. crabs, shrimp and jellyfish), small birds, small fish and baleen whales feed on the zooplankton. Seals, sea lions, skates, larger seabirds, porpoises and toothed whales feed on the fish and invertebrates. A substantial portion in the diet of larger pollock is made of plankton such as krill. This is the same food baleen whales filter out of the water when feeding. Krill is the common name of shrimp-like marine invertebrates belonging to the order of crustaceans called the Euphausiids. Adult Pollock also dine on smaller pollock and this has been seen in our harvest as some pollock come up from the net with smaller fish in their mouth or stomach contents.

What is plankton?

Plankton is a general word used to describe aquatic organisms that tend to drift with the current and are usually unable to swim against it. They are generally buoyant and found in the epipelagic zone (top of water receiving sun energy) although many species have serious vertical migration to feed and escape predators. Most folks think of plankton as being tiny but large seaweeds and jellyfish are considered plankton. Phytoplankton refers to algae and photosynthetic organisms that make food with the sun’s energy. Diatoms are important phytoplankton in the Bering Sea ecosystem an have amazing silicon patterns. Zooplankton includes many groups of animal-like organisms, including microscopic protozoa and tiny crustaceans such as daphnia and copepods. The copepods population seems like an important link in understanding survivorship of young pollock. Many benthic crustaceans and mollusks (oysters and clams) start their life cycle as free-swimming larvae high in the water column. Young fish such as pollock also start their life cycle as plankton-like larvae.

Methot net, flow meter, and emptying the plankton net

Observing and Measuring Pollock Food: Last night we did a Methot Trawl. This involves dragging a net with a finer mesh than our fish trawl to pick up plankton. This is important in understanding what the fish we study are eating. When we dissect the belly of a pollock we often find it full of zooplankton with the occasional small fish, such as smelts or young pollock. We correlate the mass of the plankton caught in the net with the flow rate to estimate population density. We estimated 44,000 critters in the 35,000 cubic meters of water that passed through the net, much of which consisted of Euphausiids and Amphipods. This works out to approximately 1.3 plankton organisms per cubic meter of water.

Euphausiid pictured left and Amphipod pictured right

Personal Log

The Bering Sea has been relatively calm with good visibility. We have seen our first boats in over 36 hours, some fishing boats and a Coast Guard Cutter. There have been some marine mammal sightings but nothing close enough to make an ID. I am settling into a bit of a routine, waking around 10:30 AM for lunch and then relaxing and working out before checking in for my shift at 4 pm. I spend a fair amount of my off time in our spacious bridge discovering new technological toys and looking out for wildlife. Each day I spend some time out on the deck above the bridge for fresh air.

After dinner we usually begin fishing and I don my foulies and safety equipment and observe operations from the back deck. I then photo anything new that comes in and try to process any bycatch to make sure it is returned to the water quickly and in good shape. The science team then works together, processing the pollock and helping with the clean up. Sometimes the fish schools are large so we have to stay in our gear and work back to back trawls. After trawling we often look at the data collected or deploy various test equipment and water quality checks. Nighttime is not best for trawling so the few hours between sunset and sunrise is reserved for special project applications designed to modify our methods. In between fishing I work on my Teacher-At-Sea writings and interviewing folks on the boat.

Mature Male Pollock; testis visible above

Question of the Day

Today’s question: How is the field of acoustics used in science?

Previous Question: How does one tell a male fish from a female fish in Pollock?

Male and female Pollock look the same from their exterior anatomy. Although we weigh and catalog all the fish we pull in, we sex a 300 fish sample batch from each trawl. This involves dissecting the fish to identify their gonads. We make a cut on the ventral surface from the gills towards the anus. We open the body cavity and move the liver to the side to expose the other internal organs. Gravid females are relatively simple to ID since they have large egg sacks with whitish eggs. A mature female will have a large ovary that tends to be reddish and lined with blood vessels. Immature females are more difficult to identify and have a less pronounced ovary that varies in color.

Mature males will have developed white coiled testis. For undeveloped males one looks for pink globular organs where the white testis should be. Immature males are more difficult to identify but when no ovary is visible we search for a thin membranous tissue running from the Uro-genital opening up into the body cavity towards the backbone.

Interested in more about Alaskan fisheries?

NOAA Alaska Fisheries Science Center

Pacific State Marine Fisheries Commission

Anchorage Daily News