Pollock – Page 9 – NOAA Teacher at Sea Blog

September 18, 2013August 20, 2021

Britta Culbertson, Big Fish Little Fish, Sept 15, 2013

NOAA Teacher at Sea
Britta Culbertson
Aboard NOAA Ship Oscar Dyson
September 4-19, 2013

Mission: Juvenile Walleye Pollock and Forage Fish Survey
Geographical Area of Cruise: Gulf of Alaska
Date: Saturday, September 15th, 2013

Weather Data from the Bridge
Wind Speed: 11kts
Air Temperature: 12.2 degrees C
Relative Humidity: 87%
Barometric Pressure: 1010.7 mb
Latitude: 59 degrees 26.51″ N Longitude: 149 degrees 47.53″ W

Science and Technology Log

Finally, as we near the end of the cruise, I’m ready to write about one of the major parts of the survey we are doing. Until now, I’ve been trying to take it all in and learn about the science behind our surveys and observe the variety of organisms that we have been catching. In my last few entries, I explained the bongo net tow that we do at each station. Immediately after we finish pulling in the bongo nets and preparing the samples, the boat repositions on the station and we begin a tow using an anchovy net. It gets its name from the size of fish it is intended to capture, but it is not limited to catching anchovies and as you will see in the entry below, we catch much more than fish.

Why are we collecting juvenile pollock?

We are interested in measuring the abundance of juvenile pollock off of East Kodiak Island and in the Semidi Bank vicinity. We are not only focusing on the walleye pollock, we are also interested in the community structure and biomass of organisms that live with the pollock. Other species that we are measuring include: capelin, eulachon, Pacific cod, arrowtooth flounder, sablefish, and rockfish. As I described in the bongo entries, we catch zooplankton because those are prey for the juvenile pollock.

Pollock trio — On the top is an age 2+ pollock, below that an age 1 pollock, and then below that is an age zero pollock. (Photo credit: John Eiler)

The Gulf of Alaska juvenile walleye pollock study used to be conducted every year, using the same survey grid. Now the Gulf of Alaska survey is conducted every other year with the Bering Sea surveyed in alternating years. That way, scientists can understand how abundant the fish are and where they are located within the grid or study area. With the data being collected every year (or every other year), scientists can establish a time series and are able to track changes in the population from year to year. The number of age 0 pollock that survive the winter ( to become age 1) are a good indicator of how many fish will be available for commercial fisheries. NOAA’s National Marine Fisheries Service (NMFS) will provide this data to the fisheries industry so that fishermen can predict how many fish will be available in years to come. The abundance of age one pollock is a good estimate of fish that will survive and be available to be caught by fishermen later, when they reach age 3 and beyond, and can be legally fished.

The other part of our study concerns how the community as a whole responds to changes in the ecosystem (from climate, fishing, etc.). That is why we also measure and record the zooplankton, jellyfish, shrimp, squids, and other fish that we catch.

How does it work?

The anchovy net (this particular design is also called a Stauffer trawl) is pretty small compared to those that are used by commercial fishermen. The mesh is 5 millimeters compared to the 500 micrometer mesh that we used for the bongo. The smallest organisms we get in the anchovy net are typically krill.

Trawl net — A picture of a generic trawling net. It’s very similar to the anchovy net that we are using.

Typically, we don’t catch large fish in the net, but there have been some exceptions. You might wonder why larger fish do not get caught in the net. It’s because the mesh is smaller and it’s towed through the water very slowly. Fish have a lateral line system where they can feel a change in pressure in the water. The bow wave from the boat creates a large pressure differential that the fish can detect. Larger fish are usually fast enough to avoid the net as it moves through the water, but small fish can’t get out of the way in time. One night we caught several Pacific Ocean Perch, which are larger fish, but very slow moving. They are equipped with large spines on their fins and are better adapted to hunkering down and defending themselves as opposed to other fish that are fast swimmers and great at maneuvering.

This is one of the Pacific Ocean Perch (rockfish) that got caught in our net.

When we pull in the trawl net, it is emptied into buckets and then the haul is sorted by species and age class. The catch is then measured, weighed, and recorded on a data sheet. After that, we return most of the fish to the sea and save 25 of the juvenile pollock, capelin, and eulachon to take back to Seattle for further investigation. We also save some of the smaller flatfish and sablefish to send back to Seattle. Check out the gallery below to see the process from beginning to end.

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Where are the pollock in the food web?

Eulachon and capelin are zooplanktivores and compete with the juvenile pollock for food. Larger eulachon and capelin are not competitors (those over 150 mm). Arrowtooth flounder and Pacific Cod are predators of the juvenile walleye pollock. Cyanea and Chrysaora jellyfish are also zooplanktivores and could potentially compete with juvenile walleye pollock, so that is why we focus on these particular jellyfish in our study.

This Cyanea jelly weighed 11.6 kilograms!

One of the most common jellies that we see, Cyanea or Lion’s Mane Jelly.

Chrysaora

What’s in that net?

When we pull in the trawl, we sort it into piles of different species and different age classes. If we get a lot of juvenile pollock (age 0), we measure and weigh 100 and freeze 25 to take back to the lab so their stomach contents can be examined. We do the same procedure for young capelin, eulachon, and flatfish. Other organisms like jellyfish are counted and weighed and put back in the ocean.

Below is a list of different organisms we have found in the anchovy net during this cruise:

Walleye Pollock
Eulachon
Capelin
Shrimp
Larger zooplankton
Pink and Coho Salmon
Pacific Ocean Perch
Lanternfish
Prowfish
Arrowtooth Flounder
Cyanea Jellyfish
Chrysaora Jellyfish
Miscellaneous clear jellyfish (some moon jellyfish)
Ctenophores (comb jellyfish)
Spiny Lumpsucker
Toad Lumpsucker
Grenadier
Flathead sole
Pacific cod
Herring
Sablefish
Sand Fish
Octopus
Snail fish

Very tiny snail fish!

Every once in a while we find Pacific Cod juveniles, which look very similar to juvenile pollock.

A pink salmon that made its way into our net.

Sometimes all we catch in the net are jellies!

The top two arrowhead flounders are facing up and the bottom one is upside down. Notice the color variation. In flounders, both of the eyes have migrated to the top of the head.

A small pile of krill that was in our anchovy net.

Sometimes we net jellies and sometimes we net kelp, but we are really looking for pollock!

These are the larval stage of a fish belonging to the family Osmeridae. They are likely Capelin or Eulachon.

Small flatfish larvae.

Sand fish found in the trawl. Note the upward pointing mouth. (Photo credit: John Eiler)

A teeny tiny octopus! (Photo credit: John Eiler)

Herring (Photo credit: John Eiler)

Here I am holding a large arrowtooth flounder that was in our trawl.

The sharp teeth of an arrowtooth flounder.

The top fish is a Eulachon, the next is a Capelin, followed by a larval osmerid (could be a Capelin) and lastly, an age zero pollock.

Personal Log

As we wind down the cruise, I’m feeling a little sad that it’s ending. I’m looking forward to going home and seeing my husband and our dog, but I’ll miss the friends I’ve made on the ship and I’ll certainly miss collecting data. Even though it can be quite repetitive after awhile, I can’t think of a more beautiful place to do this work than the Gulf of Alaska. The last few days we have had a couple of stations near the coastline around Seward, Alaska and we have ventured into both Harris Bay and Resurrection Bay. There we caught sight of some amazing glaciers and small islands. There was even an island that had bunkers from WWII on it. Yesterday, 3 Dall’s Porpoises played in our bow wake as I stood on the bridge and watched. It’s moments like this that all of the discomforts of being at sea fall away and I can reflect on what an incredible experience this has been!

Glacier — Beautiful scenery from Resurrection Bay.

Dall's Porpoise — Three Dall’s porpoises that were playing in our bow wake.

Did You Know?

Spiny lumpsuckers are tiny, cute, almost spherical fish that have a suction disk on their ventral (bottom) side. The suction disk is actually a modified pelvic fin. They use the suction disk to stick to kelp or rocks on the bottom of the ocean.

Their family name is Cyclopteridae (like the word Cyclops!). It is Greek in origin. “Kyklos” in Greek mean circle and “pteryx” means wing or fin. This name is in reference to the circle-shaped pectoral fins that are possessed by fish in this family.

These lumpsuckers are well camouflaged from their predators and their suction disk helps them overcome their lack of an air bladder (this helps fish move up and down in the water). Because lumpsuckers don’t have an air bladder, they are not great swimmers.

Spiny lumpsuckers are on average about 3 cm in length, but there are larger lumpsuckers that we have found, like the toad lumpsucker that you can see in the photo below.

You can read more about the spiny lumpsucker on the Aquarium of the Pacific’s website.

A cute little spiny lumpsucker.

A large toad lumpsucker.

September 7, 2013August 20, 2021

Britta Culbertson: Exploring the Oscar Dyson and Kodiak, AK Before Departure, September 3, 2013

NOAA Teacher at Sea
Britta Culbertson
Aboard NOAA Ship Oscar Dyson
September 4-19, 2013

Mission: Juvenile Walley Pollock and Forage Fish Survey
Geographical Area of Cruise: Gulf of Alaska
Date: Tuesday, September 3rd, 2013

Weather Data from the Bridge (for Sept 4^th at 8:57 PM UTC):
Wind Speed: 5.11 kts
Air Temperature: 12.6 degrees C
Relative Humidity: 70%
Barometric Pressure: 1003.2 mb
Latitude: 57.78 N Longitude: 152.43 W

Personal Log

My trip to Kodiak from Washington, DC was a long one. I left DC early in the morning on September 2^nd and I nearly missed my connection in Seattle after our flight left late from Reagan National Airport. I tried to dash off the plane, lugging my suitcase and backpack, with only 10 minutes to get to my connecting flight before it was supposed to take off. Fortunately, I know my way around SEA-TAC airport and with all of my escalator running experience from a year of DC living, I was able to get to my gate with 2 minutes to spare. On the plane, I was reunited with the scientists for my cruise and off we flew to Anchorage. Three and a half hours later, we arrived in Anchorage and from there it was just a one-hour flight to Kodiak Island where the NOAA ship the Oscar Dyson was in port.

While the ship was in port, we slept on board and I got used to the subtle rolls of the ship, which of course is nothing like when the ship is in motion. After a long day of travel on Monday, we ate dinner in town and went straight to bed afterwards. I spent the first day on the ship getting acquainted with the twists and turns of the hallways and the multiple staircases leading to different parts of the ship. Interestingly, you can’t walk from bow to aft on the same level on the Dyson, which makes it kind of difficult to get a nice deck side stroll.

There are 8 people, including myself, on the science team and a total of 33 people aboard the ship. I’m sharing a cabin with one of the scientists and we each have our own bunk with a small lamp and a curtain so we can close ourselves in and get some shut-eye. Each stateroom (cabin) has a shower and toilet, which is pretty luxurious! Once we get underway and get started working, I will work the noon to midnight shift and my roommate will work the midnight to noon shift. That way we will each have time alone in the cabin when the other is working.

Private bathroom — Our private bathroom.

Mess Hall (cafeteria) on the Dyson. Note the tennis balls and the tie downs on the chairs.

Science and Technology Log

Tuesday was our first full day in Kodiak and we started the day aboard the Dyson with a briefing about the scientific work that we would be doing during the cruise. It was a bit overwhelming at first, because every term is completely new to me. But because of the repetitive nature of the work we will be doing, everyone has assured me that once we get going, I will totally get the hang of it. In short, one of the things we will be looking at is the year 0 pollock (those fish which haven’t had a first birthday yet). The fish we collect during the survey will be analyzed back in Seattle to see how healthy they are. From there, projections can be made about how many pollock will make it through the winter and survive until their first birthday. Fish become vulnerable to the fishing when they reach year 3, so it’s important to understand the health of the young pollock now to set the numbers that can be caught by the fishing boats down the road.

Research boats are not like cruise ships. There are few comfortable places to sit outside of the lounge and people are working around the clock on various shifts, so you have to be really quiet when walking through the hallways. On board, there are automatically closing doors that slam shut during drills and emergencies, very steep staircases, and slippery floors. The Oscar Dyson has several labs below deck. I will spend most of my time working in the wet lab processing the pollock that we collect. There are computers on board and we also have internet, though the ship has to be going the right direction for us to be able to use it because otherwise the incoming signal gets blocked by the exhaust stack when the ship is at certain headings.

On Tuesday morning, we also had a short briefing about by Operations Officer Mark Frydrych, one of the NOAA Corps officers aboard the Dyson. He described the general rules and regulations on board the ship. Tomorrow (Wednesday) we head out to sea in the afternoon after the ship gets fueled. We will have to travel for a few hours to get to our first station where the work begins. I’m really looking forward to getting out to sea and starting to work on the project!

Did You Know?

“NOAA Ship Oscar Dyson R-224 supports NOAA’s mission to protect, restore and manage the use of living marine, coastal, and ocean resources through ecosystem-based management. Its primary objective is as a support platform to study and monitor Alaskan pollock and other fisheries, as well as oceanography in the Bering Sea and Gulf of Alaska. The ship also observes weather, sea state, and other environmental conditions, conducts habitat assessments, and surveys marine mammal and marine bird populations.

Oscar Dyson, was launched at VT Halter Marine, in Pascagoula, Mississippi on October 17, 2003, and was commissioned May 28, 2005 in Kodiak, Alaska. Oscar Dyson is the first of four new fisheries survey ships to be built by NOAA. The ship, one of the most technologically advanced fisheries survey vessels in the world, was christened Oscar Dyson by Mrs. Peggy Dyson-Malson, wife of the late Alaskan fisherman and fisheries industry leader, Oscar Dyson. The ship is homeported in Mr. Dyson’s home town of Kodiak, Alaska.”

Excerpt taken from: http://www.moc.noaa.gov/od/

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August 7, 2013March 12, 2021

Julia Harvey: Pollock on Deck/The Beautiful, the Strange and the Interesting, August 3, 2013

NOAA Teacher at Sea
Julia Harvey
Aboard NOAA Ship Oscar Dyson (NOAA Ship Tracker)
July 22 – August 10, 2013

Mission: Walleye Pollock Survey
Geographical Area of Cruise: Gulf of Alaska
Date: August 3, 2013

Weather Data from the Bridge (as of 00:00 Alaska Time):
Wind Speed: 26.5 knots
Temperature: 13.6 C
Humidity: 84%
Barometric Pressure: 1014.6 mb

Weather Update:
A low pressure system is in the north Pacific and we are having increase winds and swells.

Science and Technology Log:

We listened. We fished. Now what?

Before reporting to the fish lab, I must gear up. Slime gear keeps the scales and goo off of my clothes.

Julia Harvey — That is me holding coral while in my slime gear.

Fish are emptied out of the net and onto the table outside the fish lab.

fish table — The fish caught in the trawl net are emptied onto this table.

We can control how many fish land on the conveyor belt by raising the table and opening the door.

The fish on the conveyor belt are separated by species.

Separating species — As the fish come off the table, Jodi and I separate the species while Darin weighs them.

In this blog we will focus on the pollock that were caught.

Pollock are gathered into baskets and weighed.

We group the pollock into 3 groups; age 1, age 2 and age 3+. Each group as an entirety is weighed. Each age group has a somewhat different protocol for processing. Fifty specimens that are age 1 will be measured with the ichthystick and 10 will also be weighed.

Fish that are age 2 are processed as age 1 but are also sexed.

When measuring a pollock on an icthystick, one measures from the head to the fork in the tail. The icthystick (a magnetic board for measuring fish) is connected to a computer that automatically records the data.

The larger pollock are grouped by sex. To do this, we cut open their abdomen and look for ovaries or testes.

sexing fish — The abdomen must be opened to determine the sex of the pollock

Then all of the fish (or at least 300) are measured on the icthystick. Forty will be measured and weighed and set aside for otolith removal.

Otoliths are made of calcium carbonate and are located directly behind the brain of bony fishes.

They are involved in the detection of sound and the process of hearing. The age of the fish can be established by counting the annuli much like one does when counting tree rings.

This age data allows scientists to estimate growth rates, maximum age, age at maturity, and trends of future generations. This data is vital for age based stock assessment models. These fish are weighed and measured. Otoliths are removed and placed in jars with glycerol thymol.

The jars have bar codes on the side so that the otoliths are linked to the fish’ weight, length and sex.

The otoliths are sent to Seattle for more detailed analysis of age. These results will be used to correspond length to age in the stock assessment report.

Sometimes, ovaries are removed and sent to other scientists for further histological study.

Other organisms that are caught alongside the pollock are counted and measured as well. The catch might include Pacific ocean perch, salmon, herring, viper fish, lantern fish, jellyfish, squid, and capelin. Below are a few of the normal finds and the rest can be found in my personal blog account “the beautiful, the odd and the interesting”.

Personal Log:

The beautiful, the odd and the interesting

This trip is not just about pollock. When we bring any of the nets in there is the possibility of weirdness and other things that catch my eye. Jodi is always filling me in on the uniqueness of our discoveries. And Darin lets me save organisms for photographing later.

My favorite find so far is the lumpsucker. As Jodi says, they have gentle brown eyes and they do. They also have suckers on the bottom that allow it to stick to substrate.

The Methot trawl went close to the bottom and picked up a handful of brittle stars. At first, when they were mixed with all of the krill, it looked like a bunch of worms.

Pollock do eat young pollock. We found evidence of this when Darin opened the stomach of an adult and discovered partially digested age 1 pollock.

pollock stomach — This pollock had feasted earlier on young pollock.

Lanternfish (Myctophids) make up a huge amount of the deep sea biomass. They have photophores along their sides for producing light.

The adult Pacific sandfish bury themselves in the sand with only their mouths protuding.

Prowfish lack pelvic fins. They have continuous teeth to feed on jellyfish.

When I think of deep ocean fish I think of the viperfish with its needle sharp teeth.

This cute mud star came up with the brittle stars. It was also referred to as the cookie cutter starfish because it resembles a shortbread cookie.

Salmon are good swimmers and usually escape the net. A few are caught at the surface.

When we were in Kodiak, I would watch the moon jellies drift by. Now we are catching several different species of jellyfish like this sunrise jelly.

Jodi always has a keen eye for finding nearly invisible creatures. The arrow worm is a voracious predator. They immobilize their prey with neurotoxins.

I had never heard of a sea mouse before this cruise. Now I have. Except it is not a rodent. It is a carnivorous worm that feeds on hermit crabs and other worms. It is also a scavenger like a vulture.

Some isopods are parasitic and will feed off of the blood of fish in the gill chamber. I prefer their cousins the pill bugs.

Did You Know?

When we are all measuring and weighing away in the lab, it sounds like a video game. Each machine has it’s own unique sound effects. This allows scientists to have confidence that their data was recorded.

machine noise — All machines have unique recording sounds

August 6, 2013August 20, 2021

Melissa George: Would You Like Fries with That? August 5, 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: August 5, 2013

Current Data From Today’s Cruise (2 pm Alaska Daylight Time)

Weather Data from the Bridge
Sky Condition: Partly Cloudy
Temperature: 15.8 ° C
Wind Speed: Light Wind
Barometric Pressure: 1018.7 mb
Humidity: 84%

August 5, 2013 is a Cloudy Day on the Oscar Dyson

Sun and Moon Data
Sunrise: 5:13 am
Sunset: 9:35 pm
Moonrise: 4:22 am
Moonset: 8:27 pm

Geographic Coordinates ( 2pm Alaska Daylight Time)

Latitude: 59 ° 09.7 N Longitude: 141° 27.6 W
The ship’s position now can be found by clicking: Oscar Dyson’s Geographical Position

Science and Technology Log

Processing the Catch
My last blog post focused on mid-water trawling; this blog will focus on processing the catch. When we process the catch, we are processing it in a scientific way, not a food production way. The goal of any fish survey is to try to determine how many fish (in this case pollock) are in the sea in order to establish sustainable fishing limits. Ideally, trawling allows scientists to randomly select a sample of pollock to measure a good representation of the pollock population. The survey is undertaken in an ecologically friendly way with a focus to preserve as many fish as possible by releasing them alive back into the ocean. I will go through the steps of this process.

Step 1: Sorting and Measuring

Usually, fish brought in with the trawl net are placed directly on the table. If the catch is especially large, it may be weighed first by attaching a scale to a crane, and then attaching the load to the scale. The entire catch is weighed so the scientists can use the length and gender data taken from the sample to extrapolate for the entire catch. Then a sample (ideally 300 pollock) are kept to process and the rest are released. This data is combined with the acoustics data to estimate the size of the entire stock.

Delivering Fish From Trawling Net to Table

Fish are emptied out of the net and onto the table outside of the fish lab. The number of fish that land on the conveyor belt can be controlled by raising the table and opening the door. The fish on the conveyor belt are separated by species. Although in the catch there are often many types of species of sea animals present, the focus of this blog will be the pollock that are caught.

An Interested Observer Checks out the Pollock on the Conveyor Belt

In the video clip, the vast majority of the fish are adult pollock, but sometimes there are a variety of age stages; Age 0, Age 1, and Adult are what we have seen. Pollock are sorted by age, gathered into baskets, and weighed. Age 0 and Age 1 pollock are weighed and then measured with the icthystick, a magnetic fish measuring board, from the head to the fork in the tail. The icthystick is connected to a computer that automatically records the data. (The icthystick below shows how the length of capelin, a prey of pollock, are measured and recorded; the method is the same pollock).

Step 2: Sexing

Each age group has a somewhat different protocol for processing. Counts and measurements of weight and length are taken for the smaller pollock (and capelin). The larger pollock are grouped by sex. To do this, the abdomen is sliced open with a scalpel, the innards are pushed aside, and ovaries or testes are identified. After determining the sex of the fish, its length is measured with the icthystick. Finally, a subsample of fish are set aside for otolith removal. As we process a catch, samples of fish and other species are collected for various off-board scientists. For example, Age 0 pollock are kept for one scientist; ovaries from mature pollock for another.

Sometimes it is difficult to tell the testes from the ovaries. Generally, both are paired organs that lie along the vertebrae under the guts (stomach, liver, intestines). The ovaries tend to be fuller and more brightly colored; the testes, stringier and paler. However, these organs can vary somewhat depending on the maturity of the fish. Below are examples of the organs from fish that have not yet spawned (photos courtesy of Story Miller, TAS 2010).

These are the testes of a pre-spawning male — Testes of a Pre-Spawning Male Pollock (bottom right)

These are ovaries in the pre-spawning stage — Ovaries of a Pre-Spawning Female Pollock (center)

Step 3: Removing Otoliths

Otoliths are made of calcium carbonate and are located directly behind the brain of bony fishes. They are involved in the detection of sound and the process of hearing. The age of the fish can be established by counting the annuli (small ridges on the otoliths) much like one does when counting tree rings. This age data allows scientists to estimate growth rates, age at maturity, and exposure to various environmental conditions.

The otoliths are brought to Seattle for more detailed analysis, so after extracting them from the pollock, they are placed in jars with a preservative called glycerol thymol. The jars have bar codes on the side so that the otoliths are linked to the fish’ weight, length and sex. These results will be used to correspond length to age in the stock assessment report.

Personal Log Accomplishment

Continuing with Maslow’s hierarchy of needs, I will discuss some of the ways that the need of feelings of accomplishment are met on the Oscar Dyson.


A Version of Maslow’s Hierarchy of Needs

The goal of the Oscar Dyson crew is to safely and successfully navigate the ship through the Gulf of Alaska transects collecting and processing pollock. As of Saturday, August 3 on this mission, we have traveled almost 3000 nautical miles, traversed through 33 transects and completed 26 Aleutian Wing Trawls, 6 Poly Nor’eastern Bottom Trawls, and 6 Methots. We have measured and recorded data for 4,387 fish; 2,696 of these were pollock. We have also collected 334 otoliths. These numbers give the team a sense of accomplishment, knowing that they have contributed to the data and information processing to promote sustainable fishing practices. Check out this link, the NOAA FishWatch webpage that provides information on sustainable fishing practices.

Did You Know?

Married couples can work together aboard the Oscar Dyson. Kristin and Vince met in graduate school at the University of Florida where they were working on Master’s Degrees in Fisheries and Aquatic Science. They were collaborating on a project that focused on river systems in Florida. After getting married and working in labs at both the University of Maryland and Oregon State, they applied for Survey Technician positions with NOAA. Kristen and Vince work opposite shifts on the Oscar Dyson; Kristen works mornings and Vince works evenings. As survey technicians they are responsible for the calibration and deployment of various data acquisition systems such as the Scientific Computer System (SCS) that is constantly monitoring information such as air temperature, sea temperature, salinity, chlorophyll levels and weather. Kristen and Vince work as liaisons between the science team and the NOAA Corps.

Vince and Kristen, Oscar Dyson Survey Technicians

Something to Think About:

So far we have discussed the following invertebrate animal phyla: Porifera and Cnideria. Today’s episode of Trawling Zoology features other interesting representatives of the invertebrate animal kingdom: Annelida, Mollusca, Arthropoda, and Echinodermata that have turned up in our catches.

Phylum Annelida-from the Latin word anulus meaning “little ring”

Annelids are segmented worms that have a linear series of external segments divided by septa (walls between segments) that house serially repeated nervous, muscle, and excretory systems. Their anterior segments contain jaws, eyes, and cirri (small feelers that help with feeding). Filter-feeding marine annelids capture bacteria and feed selectively on sediment particles within tubes buried in sand or mud.

Polychaete from the Phylum Annelida (found in a bottom trawl)

Phylum Mollusca-from the Latin word mollis meaning “soft”

Mollusca is one of the most diverse groups of animals on the planet, with at least 50,000 living species (and more likely around 200,000). It includes such familiar organisms as sea snails, octopuses, squid, clams, and chitons, all of which we have seen on this mission. They all have soft bodies which typically have a “head” and a “foot” region. Often their bodies are covered by a hard exoskeleton, as in the shells of snails and clams or the plates of chitons. Squid and octopuses have small internal shells.

Members of the Squid Family, Gonotopsis borealis, the Armhook Squid

Hermit Crabs (Arthropods) Inhabiting the Shells of Mollusks

Phylum Arthropoda-from the combination of Greek words arthron meaning “jointed” and pous meaning “feet”

The Phylum Arthropoda includes organisms such as insects, spiders, and crustaceans (crabs and shrimp). The vast majority of sea dwelling arthropods are crustaceans. For example, the hermit crabs emerging from the mollusk shells in the picture above are members of the most abundant family on Earth, the arthropods. Arthropods have an exoskeleton of a tough compound called chitin that forms a rigid armor with joints in between. This outer shell provides the structure against which arthropod muscles pull, reduces water loss, and protects them from environmental dangers. Below are other examples of arthropods found frequently in trawls.

Isopods (The Cockroaches of the Sea) among Krill, another type of Arthropod

Phylum Echinodermata-from the combination of Greek words echinos meaning “spiny” and derma meaning “skin”

The adults are recognizable by their (usually five-point) radial symmetry, and include such well-known animals as starfish, sea urchins, sand dollars, and sea cucumbers. Echinoderms are found at every ocean depth and contains about 7000 living species. Echinoderms are also the largest phylum that has no freshwater or terrestrial (land-based) representatives. Two unique characteristics of this phylum are the ability to regenerate tissues and their ossified limestone exoskeletons.

Various Starfish found in a Bottom Trawl

July 31, 2013March 12, 2021

Julia Harvey: Determining Population Size/A Day in My Life Cruising, July 27, 2013

NOAA Teacher at Sea
Julia Harvey
Aboard NOAA Ship Oscar Dyson (NOAA Ship Tracker)
July 22 – August 10, 2013

Mission: Walleye Pollock Survey
Geographical Area of Cruise: Gulf of Alaska
Date: 7/27/13

Weather Data from the Bridge (at 1:00 am Alaskan time):

Wind Speed = 3.52 knots
Air Temperature = 13.6 C
Humidity = 94%
Barometric Pressure = 1025.5 mb

Science and Technology Log:

How can you determine the population size of species?

You could count every member of the population. This would be the most accurate but what if the population moves around a lot? What if the population is enormous and requires too much time to count each and every one? Would you want to count all of the krill in the Gulf of Alaska?

You could mark and recapture. In this method you catch individuals from the population and tag them. Data are compiled from the recaptures and the population is mathematically calculated. Halibut and many other populations are monitored this way and require fishermen to report any recaptures.

Tagged Halibut
photo courtesy of Greenland Institute of Natural Resources

Another method is sampling. The organisms in a small area are counted and then the overall population in the entire area is calculated.

line_transect — Using a transect to sample a population.
Photo courtesy of http://www.kscience.co.uk/as/module5/succession/fieldwork.htm

This picture above illustrates the use of a transect line. On various increments along the transect line, samples of populations are taken. Imagine the Oscar Dyson’s path as the measuring tape and the trawl net as the sampling square.

The overall survey area of the pollock study this summer is the northern Gulf of Alaska between the shore and the continental break. Within this area transect lines were established. These are pathways that the Oscar Dyson will travel along and periodically take samples of the fish.

Transect Plan — The pollock summer survey is broken into three legs. I am part of leg 3.
Photo courtesy of NOAA

The current set of transects are 25 nautical miles (1 nautical mile is equal to 1 minute of latitude) apart and are parallel but transects in other areas may be 2 or 5 miles apart. Transects that we are following now are located on the shelf and are perpendicular to the coastline. Transects in inlets and bays may run differently and may even zigzag.

OD Current Cruise — Leg 3 left from Kodiak and is moving eastward for the survey.
Photo courtesy of NOAA

If fish are located through acoustics, the ship will break transect (a mark is made on the map) and the ship will circle around and a sample of the population is taken by trawling. The population of pollock can then be mathematical calculated. After trawling, the ship will return to the break and continue along the transect line.

This afternoon, we were working smaller transect lines near Amatuli Trench that were 6 miles apart. It is an area that has had good pollock catches. Just when we were going to fish, a pod of fin whales was spotted in the area. So we moved to another area and hauled in quite the catch of Pacific Ocean perch.

POP Haul — After fish are caught they are processed in the fish lab. Here we are processing the Pacific Ocean perch.

It is hopeful that the Oscar Dyson will finish a transect line by nightfall and then the ship can be at the next transect by sunrise. This maximizes the time looking for fish and trawling.

Personal Log:

I am settling into life on the Oscar Dyson and have established a routine that will support my night shift (4 pm to 4 am). So how do I spend 24 hours on the ship?

I wake up around 11:45 in the morning to be able to eat lunch that is served only between 11:00 and 12:00. Because of the shift schedules, some people are bound to miss one or more of the meals. I miss breakfast because I am sleeping. We are able to request a plate of food be saved for later.

Between the end of lunch and the start of my shift, there are several things that I can do. The weather has been very nice and so I often go on deck to soak up the sun and whale watch.

Whale watching — Can you spot the fin whales?

I may need to do laundry as my clothes start to smell fishy.

Laundry Room — We are lucky to have a laundry room on board. It meant I did not have to bring many clothes.

I will also workout in one of the two gyms. The gym at the back of the boat can’t be used when trawling because of the high noise level. There is a rower, two exercise bikes, two treadmills, a cross trainer, mats and weights. I got lucky and someone installed a makeshift pull up bar.

Front exercise room — This is the exercise room towards the bow of the ship.

Back Exercise Room — This is the exercise room toward the stern of the ship.

There is also a lounge where I can read or watch DVDs. Some of the movies are still in theaters.

An hour before my shift starts, I read and take a short nap. Then, I grab a cup of coffee at 4 pm as my shift starts. I listen as the day shift fills in the evening shift about the happenings of the last 12 hours.

During my shift, there are several things that I may do. If we have fished, there will be pollock and other organisms to process.

Processing pollock — Here Jodi, Kirsten and I are processing the pollock by determining their sex. Then, they will be measuresd weighed and their otoliths removed.

After processing, we need to clean up the fish lab which involves spraying down everything include ourselves with water to remove scales and slime.

I also keep an eye on the acoustic monitors, to see what I can recognize. Paul and Darin are always willing to answer my questions (even the ones I already asked).

Acoustics Screens — The four screens of acoustic data. From these screens, Paul will determine whether to fish.

I may look at trawl camera footage or observe camera drops. Drop Camera

I also have time to work on my blog.

Work Space — I have set myself up an area in the “Cave” to write my blog.

Dinner is served at 5 pm but the mess is always open and is filled with snacks such as sandwich fixings, ice cream, yoghurt, a salad bar and pop tarts.

Whenever I get hungry at night, I just head for the mess. It is a time that I am able to chat with the crew and NOAA Corps as they come in for snacks too.

At 4 am, I make it a point to head directly to my stateroom and go to sleep. The room has a window but I can close the curtains on the portlight (window) and around my bed.

There are no weekends out here. Everyone works 7 days a week for the duration of the cruise.

Did You Know?

Usually fin whales show only their back as they surface for air. Check out my video clip and see if you can spot the whale. It wasn’t too close.