Tag: trawl

Posted on

Megan Woodward, July 7, 2009

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

Mission: Bering Sea Acoustic Trawl Survey
Geographical Area: Bering Sea/Dutch Harbor
Date: Tuesday, July 7, 2009

This map depicts the path the Miller Freeman will take on our cruise.
This map depicts the path the Miller Freeman will
take on our cruise.

Weather/Location 
Position: N 56.18.292; W 171.46372
Air Temp:  7.3 (deg C)
Water Temp:  6.9 (deg C)
Wind Speed: 17 knots
Weather: Overcast

Science and Technology Log 

We are traveling on designated lines in the north/south direction looking for pollock (travel lines are illustrated above). The samples we pull in are compared to the amount of fish found in the same location over 20+ years.  The process used to “go fishing” is not as easy as one might think.  Several things need to align for a successful trawl to take place. As of today, I have been a part of three successful trawls.  Below is an explanation of the fishing process.

  1. The Fisheries Research Biologist and his team recognize a series of acoustic returns as potential pollock schools while sitting in the acoustics lab. Then they decide if the amount of fish being seen is enough to fish on. If yes, go to step 2.
  2.  Next the team questions if the weather conditions are calm enough, are the fish far enough off the bottom of the sea floor, and have we traveled at least 30 miles from our last fishing point.  If conditions are aligned, move to step 3.
  3. The team contacts the bridge to prepare the crew for fishing. The bridge receives the exact location (longitude/latitude) the nets should enter the water for the best possible fishing.  By now we have traveled over the top of the fish we saw on the acoustic screen.  A decision must be made about the best direction to travel so the nets work properly:  Do we flip a u-turn and fish up the line, or do we circle back to where we saw fish and retrace our path on the line? The water’s current and prevailing winds impact how the nets will function, which are some of the deciding factors in choosing the direction we will tow the nets.  Fishing in motion, continue to step 4.
  4.  Up to the wheelhouse. Here the lead fisherman, the ship’s Officer of the Deck (person in charge of driving the ship) and the fisheries team can work together to create the best fishing scenario. The same acoustic information can be viewed in the wheelhouse as in the acoustic lab.  Based on the depth of the acoustic return, the fisheries team can inform the fisherman how far to lower the nets in the water. Keep going to step 5. We almost have fish…we hope!
  5. Once the net is in the water, there are two acoustic screens closely watched. These are pictured below with the explanation of the information received.  The net is continually raised or lowered based on the depth of the return. A trawl lasts for 20 minutes and covers 1 mile on average. The fisheries team is aiming for 300 fish per trawl.  They are careful to not over fish. Almost done, bring the fish aboard.
  6. The final step is bringing the nets back in and unloading the fish.  If all went as planned, the next few hours will be spent in the fish lab collecting information about the sample. Unfortunately the system is not perfect.  It’s possible to bring in a water haul or a stuffed sausage. Neither one is good news.
This is the acoustics lab. The top screens are displayed in the bottom monitors as needed. The top two left monitors show the acoustic return from the 5 frequencies (pings) sent out.
This is the acoustics lab. The top screens are displayed in the bottom monitors as needed. The top two left monitors show the acoustic return from the 5 frequencies (pings) sent out.

Personal Log 

Now that I have participated in three trawls, I’m feeling much more comfortable with the whole fishing process. Rather than looking at the acoustic screens with a puzzled look, I’m able to recognize what the return from a school of pollock looks like. Jellyfish show up on the screen as blue-green clusters, and have been present in the top 40 meters of water the majority of time we’ve been at sea.  I can only imagine how many of those creatures are down there.

There seems to be a bit of humor in all we do at sea.  There are two awards given out based on the hauls we bring in: The water haul and the stuffed sausage awards.  You really don’t want to be the recipient of either one. The water haul award goes to the team that brings in the haul with the least fish (mostly water). This happened yesterday when we attempted to catch pollock close to the surface.  There wasn’t but a single pollock in the net. Of course there were numerous jellyfish.

This is an acoustic screen showing a return typical of pollock. The several clusters with the trail of return on the left are showing a good fishing opportunity. The dark red across the middle of the screen is the sea floor.
This is an acoustic screen showing a return typical
of pollock. The several clusters with the trail of
return on the left are showing a good fishing
opportunity. The dark red across the middle of the screen is the sea floor.

The stuffed sausage is just the opposite of a water haul. As you may have guessed, the stuffed sausage award goes to the team that brings in the most over-stuffed net.  If we were looking to make money off of our catch, this would be considered a success. However, we really only want a sample of about 300 fish. A stuffed sausage means too many fish were brought in.  It is possible to be the “winner” of both awards.

Animals Seen 

  1. Red-legged kittiwake  
  2. Blacklegged kittiwake
  3. Albatross
  4. Fulmar
  5. Fur Seal
  6. Capelin (they smell like cucumber)
This screen shows the return from a signal that sweeps left to right like a pendulum. The bottom of the net is the ½ circle shape. During a trawl you can see if a school of fish enters the net.
This screen shows the return that sweeps left to right like a pendulum. The bottom of the net is the ½ circle shape. During a trawl you can see if a school of fish enters the net.
When the net is in the water, there is return from the top and bottom of the net. This screen shows a vertical return. We can see we are at the correct depth, but maybe we are too far to the left or right.
There is return from the top and bottom of the net. This screen shows a vertical return. We can see we are at the correct depth, but maybe too far to the side.

New Vocabulary 

Acoustic Lab: AKA “The Cave” because there are no windows.  This is where the Fisheries Research Biologist and his team watch the acoustic return monitors.

Bridge/Wheelhouse:  This is where the officer on duty drives the ship using several navigational tools. Named the wheelhouse because the ship’s steering wheel is found here.  The bridge is located on the top level of the ship. The Methot and trawl nets are also operated from the bridge.

Haul:  This is how the fish are referred to when they are caught in the net.  One might ask, “How was the haul?”  “It was a (big haul, small haul, water haul, stuffed sausage).”

Water Haul:  A net lacking fish following a trawl.

Stuffed Sausage: An overstuffed net, too many fish caught.

Hauling in the net
Hauling in the net
This fur seal followed the boat for about 30 minutes while we were trawling for pollock. He was hoping for a free dinner.
This fur seal followed the boat for 30 minutes while we were trawling. He was hoping for a free dinner.
The center bird is a blacklegged kittiwake, identified by the black wing tips, white underwing and the light gray color on its back.
The center bird is a blacklegged kittiwake, identified by the black wing tips, white underwing and the light gray color on its back.
Posted on

Megan Woodward, July 5, 2009

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

Mission: Bering Sea Acoustic Trawl Survey
Geographical Area: Bering Sea/Dutch Harbor
Date: Tuesday, July 5, 2009

Weather/Location 
Position: N 58.37.239; W 171.05.968
Air Temp:  4.5-6.0 (deg C)
Water Temp:  4.94 (deg C)
Wind Speed: 16 knots
Weather: Overcast and rainy

This is the screen I use to get info about our ship’s location. The little white speck inside the red oval is our ship.
This is the screen I use to get info about our ship’s location. The little white speck inside the red oval is our ship.

Science and Technology Log 

We have been at sea now for almost five days in search of pollock. The fish had not been spotted on the lines we traveled on until today. We had the opportunity for our first pollock trawl around 02:00, and used the Methot net to bring in two zooplankton samples earlier in my shift. This was by far the most action yet.  I was eager and ready to see what the fishing process was all about. This log will focus on the zooplankton samples.

The Methot net was put in the water and lowered to the desired depth determined by watching the location of the acoustic return. After twenty minutes the net was brought back up and the catch was unloaded.  I was expecting a net full of euphausiids, but the critters were actually collected in a small container on the back end of the net.  The catch was brought into the fish lab and dumped into a bucket so we could separate the other organisms caught in the net (9 jellyfish and 23 tiny pollock in this case). Once the other fish had been removed, we took a sample (a ••• cup scoop) to weigh and count the euphausiids in the sample (sample is shown above). The rest of the catch was also weighed. 

There were 543 euphausiids in the scoop. The weight and number help estimate the amount of euphausiids in the entire catch. We repeated this process again a few hours later. The second sample had almost twice as many euphausiids, 13 jellyfish and fewer than 5 pollock.

The survey tech and skilled fishermen lower the Methot net into the water.
The survey tech and skilled fishermen lower the Methot net into the water.

Personal Log 

Until today, the fishing portion of this trip remained a mystery.  However, I was feeling a little sea sick, okay very sea sick, so it was probably a good thing. We encountered some VERY rough seas with sustained winds ranging from 30-40 knots and swells averaging 17 ft. Some of the swells were much larger; one was rumored to be almost 35 ft. high.  Apparently the rough seas are expected to return tonight and tomorrow. My sea legs are securely fastened, so I am ready to take on whatever the sea has to offer.

When we brought in the first haul of pollock last night, my eyes must have looked like they were going to roll out of my head.  I couldn’t believe how many fish were coming across the conveyor belt. This was what I had been waiting for, so I got on my rain gear and started sorting the fish.  Each species was placed into separate crates so a count of all fish caught could be taken.  Of course, pollock made up the majority of the catch.  In the next few weeks, I will become an expert member of the pollock survey team. Everyone on board, both scientists and crew, have been more than willing to answer my

A sample of zooplankton brought up in the Methot net. These are euphausiids, which are also referred to as krill.
A sample of zooplankton brought up in the Methot net. These are euphausiids, which are also referred to as krill.

Getting used to the 16:00-04:00 (4pm4am) shift has been trying.  Today’s shift was the first that didn’t require a nap.  Due to the odd shift hours, I’ve been waking up at 14:00 (2 pm) and going to bed around 05:00 (5 am).  This makes mealtime tricky.  Dinner is served first, then I eat some breakfast in the middle of the night. My body is thoroughly confused. The ship’s cooks are wonderful, and continually provide a stocked mess hall with loads of choices.  I swear the dessert bar is continually whispering my name. I couldn’t ask for a more kind, welcoming group of people to work questions. One part of this adventure I’m looking forward to is getting to know the wide range of characters who make this important research possible.

It was certainly a thrill to see the first whale of the trip. The pod was spotted just off the bow of the ship andlater seen in the distance.
It was certainly a thrill to see the first whale of the trip. The pod was spotted just off the bow of the ship andlater seen in the distance.

Animals Seen 

  • Fin Whale
  • Jelly Fish
  • Flathead Sole
  • Northern Flathead Sole
  • Arrow tooth Flounder
  • Pollock
  • Yellow Irish Lord
  • Euphausiids

New Vocabulary 

Zooplankton– A very small or microscopic animal organisms possessing little or no power of locomotion (can’t move themselves), leaving them to merely drift or float in the water.

Euphausiids (eu·phau·si·id) – A type of zooplankton, also known as krill, are tiny shrimp-like crustaceans that form an important part in the diet of many animals including whales, seals, fishes and birds. These are the main food source for pollock.

Methot Net  – Methot is the name of the man who designed the style of plankton net we used to catch the euphausiids.

One of several jellyfish brought up in the nets. This guy is slimy and heavy, but not a stinger
One of several jellyfish brought up in the nets. This guy is slimy and heavy, but not a stinger 
Posted on

Ruth Meadows, July 3, 2009

NOAA Teacher at Sea
Ruth S. Meadows
Onboard NOAA Ship Henry B. Bigelow 
June 12 – July 18, 2009 

Mission: Census of Marine Life (MAR-Eco)
Geographical Area: Mid- Atlantic Ridge; Charlie- Gibbs Fracture Zone
Date: July 3, 2009

Weather Data from the Bridge 
Temperature: 6.2oC
Humidity: 81%
Wind: 16.47 kts

This is one of the glass floats encased in plastic that can withstand the pressure of the deep waters.
This is one of the glass floats encased in plastic that can withstand the pressure of the deep waters.

Science and Technology Log 

High winds and high waves put a temporary stop to our fishing with the nets.  When the waves are too high, the safety of the crew comes first and we wait for the weather to clear before we can start using the trawl again. The waves finally calmed down enough for the net to be used today.  We are using a different type of net to fish the deep bottom (benthic trawling) than was used to fish the mid-water (pelagic trawling). This net is much simpler in design. It is a very large net lowered to the bottom of the ocean and then pulled behind the ship. The top part of the net is held open by floats. These floats were bought specifically for this cruise.  The pressure on the bottom of the ocean is so great that normal floats would collapse.  The new floats are made of glass spheres with a hard plastic covering. Only glass can withstand the amount of pressure that is found at these depths.

This is the net used for deep bottom trawling that has the yellow floats attached to it.
This is the net used for deep bottom trawling that has the yellow floats attached to it.

There are rubber tire-like rollers that move along the bottom to help prevent snags and also to stir up the sea floor and cause the fish and other organisms to move into the net where they are then funneled back into the narrow end of the net (cod-end). There are weights on the bottom section of the net to keep it on the ground.  Of course, there are always obstacles on the bottom of the ocean floor and occasionally the net will get caught on one of these. This is a particular problem here because of the mountainous terrain.  When the net gets hung up the crew works very carefully to release it from the obstacle.  Sometimes the ship moves backwards as the winches try to pull on the net to release it.  Sometimes the ship moves in a circle to try and pull the net clear.    

The full net after it’s been retrieved on deck.
The full net after it’s been retrieved on deck.

So far the benthic net has gotten caught twice but the crew successfully retrieved the net without damage. Once the net is on deck, the cod-end is opened and everybody comes out of the lab with foul weather gear (waterproof boots, overalls, jackets, life preserver and hardhats) on to collect the catch. We use lots of baskets to do a quick rough sort of the organisms caught.  If the net is full, it takes a while to complete the first sort.  Some of the fishes are large and some of the organisms have been torn. The organisms found on the floor of the deep floor are very different from the ones found in the mid-waters. They are much larger in size and very different in coloration.

Personal Log 

A bucket with squid and other fishes.
A bucket with squid and other fishes.

The scientific crew is divided into three groups.  We have a “day” shift, called a watch, that works from 12 noon to 12 midnight, and a “night” watch that works from 12 midnight to 12 noon, and then one group that works whenever a net comes up.  I am on the day watch and we have all gotten into a pattern of who does what in the lab.  My watch chief scientist is Dr. Shannon Devaney from Los Angeles.  She works at the Natural History Museum there.  Dr. Amy Heger from Luxembourg, Tom Letessier from Norway, CJ Sweetman from Connecticut and Randy Singer from Georgia rounds out our crew.  CJ takes DNA samples, Tom takes care of the crustaceans, Randy removes the ototliths (this helps the scientist figure out the age) from the fishes, and Amy and I use the computer to enter the data.  With some species we remove the stomach, liver and gonads from the fishes.   These body parts are then measured and either frozen or preserved for scientists that are not on the trip.  It has been fun relearning how to do some of the procedures.

The first sort of the catch.
The first sort of the catch.
Posted on

Megan Woodward, July 1, 2009

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

Mission: Bering Sea Acoustic Trawl Survey
Geographical Area: Bering Sea/Dutch Harbor
Date: Tuesday, July 1, 2009

Science and Technology Log 

What is this trip all about?  Well, NOAA is working to collect a range of pollock fish samples from across the Bering Sea.  The samples collected will help set fishing regulations based on the estimated pollock fish population.  The fish are looked at to assess the male to female ratio, size and age.

Pollock, a member of the cod family, are mainly found in the Bering Sea. They are typically found between 328 to 984 feet depths. Pollock lives up to 17 years, and reach maturity around age 4. The maximum size of the pollock is slightly larger then 3 feet long.

The colors in the picture at right indicate the amount of return received from the 3 spheres seen towards the top. The other mass of colors at the bottom and surrounding the lines are fish, which are interfering with the read.
The colors in the picture at right indicate the amount of return from the 3 spheres seen towards the top. The other mass of colors at the bottom and surrounding the lines are fish, which are interfering with the read.

We are currently preparing to set sail.  Departure time is set for 15:00 (3:00 pm).  Our first anchoring will take place just a few hundred feet from where we are docked in Dutch Harbor.  At that time, the Chief Scientist and other members of the science team will calibrate (check the accuracy) the echo sound system used during the course of the survey.  Once the calibration is complete and the data is collected, we will continue to sail in search of pollock fish.

The echo sound system is used to measure the amount of return or “back scatter” from a ping (term to describe the sound sent down into the ocean).  Depending on the size of the return, the scientists are able to determine if they are detecting fish.  Pollock are known to give a return within a specific range, which provides the scientists with one of the clues that help them make an educated guess about the type of fish being detected.

In order to calibrate the echo sound system, three metal spheres that have an expected return level are lowered into the sea.  A ping is sent into the open sea, and the scientists are able to watch the amount of return from the spheres through their computer.  The amount of return can be seen using a color-coded scale. Red shows the highest level of return, and gray is the color indicating very little return. The scientists can then see if each sphere is giving the expected return. If a sphere is giving off more or less than the expected return, the scientists then know how to adjust the level of return they are getting from fish throughout the project.

Eagle or seagull? This guy sits and waits for a food meal on top of the hotel dumpster.
Eagle or seagull? This guy sits and waits for a food meal on top of the hotel dumpster.

Personal Log 

After a day and a half in Dutch Harbor, I’m glad to finally be getting under way.  Dutch Harbor is a small, small town.  There are a few restaurants, one hotel and a Safeway.  All of the other businesses are linked to the fishing industry in one-way or another. Flying into the island was an incredible experience. The plane hummed through the air between multiple tiny landforms.  The airport runway stretches out to the edge of the sea, allowing the passengers to think, for just one moment, they are making a water landing. The plane touched down just beyond the shore.

Since my arrival, I have been welcomed with warmth from all of the NOAA scientists and deck crew. Everyone has been more than wiling to answer even the most ridiculous of questions I’ve had. My time the past two evenings were spent getting to know several of the Oscar Dyson officers and crew members.  

A good chunk of Monday was spent hiking Ballyhoo with two of the officers from the ship.  Ballyhoo is a steep hill behind the airport (approx 1400 ft. elevation). The hill was littered with WWII shelters.  As we tromped up the hill, the wind began to pick up. By the time we were nearing the top, the wind was practically knocking me sideways.  The gusts were sustained and powerful. Certainly some of the windiest conditions I’ve encountered. The wildflowers growing on the hillside were reminiscent of the summer blooms found on Mount Rainier. The views from the top were breathtaking.  Several bald eagles swooped past the emerald hills, and the sun started to peak out as we made our way back to sea level.

Animals Seen in Dutch Harbor 

  • Ground Squirrel
  • Jelly Fish
  • Bald Eagles
  • Variety of Seabirds
  • Arctic Fox
  • Guard dog
This little ground squirrel wasn’t bothered as we walked by.
This little ground squirrel wasn’t bothered as we walked by.

New Vocabulary 

Echo Sound System – A tool used to measure the return or “back scatter” from a ping.  The amount of return helps determine what is hiding under the sea.

Ping – The name of the sound that is sent into the water to create an echo/return for the scientists to read. The ping is a constant, repeated sound wave.  Several different frequencies are used to detect objects.

Return  – AKA back scatter, is the amount of acoustic sound waves/echo bouncing back off an object beneath the water.

Trawl – The phrase used when talking about catching fish using a large net

Posted on

Taylor Parker, April 27, 2009

NOAA Teacher at Sea
Taylor Parker
Onboard NOAA Ship Oscar Elton Sette
April 19-29, 2009 

Mission: Hawaii Bottom fish Survey
Geographical Area: South side of Oahu
Date: April 27, 2009

Weather Data 
Partially cloudy.
Minimal Winds.
Air temp: 75F.

Scientists deploying the CTD
Scientists deploying the CTD

Science and Technology Log 

Similar to the smaller CTD that we dropped from the SAFE boats, there is a much larger one on the Sette that is dropped almost nightly. The large CTD is different in several ways: it drops to a depth of 6800 meters while the smaller one will only go 600 and the larger CTD can measure many more components. It determines conductivity, temperature, salinity, dissolved oxygen, and flourescence. Conductivity is the amount of electrical current allowed within the sample, salinity is then measured by the conductivity and temperature, dissolved oxygen is the amount of oxygen found within between the water molecules and fluorescence is, well, exciting. Flourescence is the measurement of chlorophyll at different depths; to do this a little LED light is shone into the water to see the excitability of the algae. Determining the amount of chlorophyll, and subsequently the amount of algae, helps to, among other things, measure the amount of the oceans ability to absorb greenhouse gases.

Prior to the departure of the cruise, the scientists set up sampling sites along transects on a grid system near shore off the Kona coast. They are compiling data over the years to analyze changes in the physical characteristics of the ocean. This part of the research aboard the Sette is really interesting and the impacts of the data are obvious. However, there wasn’t much for me to do with this other than take photos of the Science Techs do their job and ask them questions. That is quite alright though; I lost a couple hooks while bottom-fishing but I don’t think that I want to be responsible for losing that big piece of equipment.

A Sample of the Marine Debris Encountered
A Sample of the Marine Debris Encountered

Earlier in the day, I was participating in the routine I/K trawl and we came across a slick that had perfect conditions for the billfish we were looking for. We dropped the net and slowly came upon the slick. We set everything in the water and even put the safety line across up. Within ten minutes the entire trawl was filled with marine debris, it was filled with trash. Debris accumulation is apparently normal for slicks; along with being an area where small fish can be found, the same ocean currents bring planktonic debris. And, according to the scientists who study billfish, it is good habitat for fish larvae. Not this time. This time the whole net was filled with trash and very little of anything else. We started going through it and found a crab and a shrimp and pounds of plastic. We collected everything and dropped the net in again hoping to keep it down there longer. While the remaining trawls were less trashy, there were still significant amounts of litter strewn about.

Personal Log 

The large CTD required trained professionals so I sat back and watched the two techs maneuver the large instrument. I spoke with them after to understand what they were doing. What I found most interesting was the use of the fluorometer to help measure the ocean’s ability to absorb greenhouse gases. Considering the challenges facing our planet and oceans, this is incredible data that they are collecting and when the results are analyzed, I can’t wait to see what they read.

Sargassum fish
Sargassum fish

Another challenge is one that we faced when trying to run I/K trawls. The amount of litter in the oceans is staggering. I have worked on many beach cleanups and have run tons of classes, educating hundreds of kids about the importance of watershed responsibility. Seeing the garbage floating freely in the water, clogging the runways of slow currents in the oceans is depressing. Talking with the other scientists they suggested I take a look at NOAA’s Marine Debris Program. This is a very useful and informative website describing the many factors of trash in the ocean: awareness and information about hazards, education, removal projects, etc. This is a very pressing problem considering debris, and specifically small plastics that look like food, is found everywhere where the ocean touches shore.

Animals Seen Today 
Like I said, we were picking up mostly trash in our trawls and the CTD doesn’t pick up many animals. One of the small boats did happen to pick up a kind of Frogfish called a Sargassum fish (Histrio histrio). I was reading about them and apparently they have one of the smallest brains in proportion to their body and they are highly cannibalistic.