Julia Harvey: Here Fishy Fishy/Prince William Sound, August 1, 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:  8/1/13

Weather Data from the Bridge (as of 00:00  Alaska Time):
Wind Speed:  12 knots
Temperature:  13 C
Humidity:  97 %
Barometric Pressure:  1021 mb

Science and Technology Log:

The main goal of Leg 3 of this mission is to use acoustics and trawling to survey the mid-water portion of the pollock population along the Gulf of Alaska starting near Kodiak to Yakutat Bay.

leg 3

Leg 3 began east of Kodiak and will continue to Yakutat

Pollock live in the an area between the middle of the water column and the seafloor.  Sometimes we sample the mid-water and sometimes we will sample the bottom.

bump-food-web_600

Location of Fish in Water Column

The Oscar Dyson carries three different types of trawling nets for capturing fish as part of the mid-water survey:  the Aleutian Wing Trawl (AWT),  a mid-water trawl net, the Poly Nor’Eastern (PNE), for bottom trawls and the Methot, which is for gathering samples of very small ocean creatures such as krill.  I will focus on the AWT, although some of the video footage is from a bottom trawl.

AWT

Scale model of the Aleutian Wing Trawl (AWT) net courtesy of NOAA Scientist Kresimir Williams

When the net is deployed from the ship, the first part of the net to hit  the water is called the codend.  This is where most of the fish end up after the trawl.  The mesh size of the net is smallest at the codend (about 1 cm) and gets larger as it approaches the doors (about 1 m).

A Cam Trawl goes in the water next.  This is a pair of cameras that help scientists identify and measure the fish that are caught in the net.  This technology can also be used to help  scientists validate their biomass estimate from trawling sampling counts.  This piece of equipment has to be clipped into loops on the trawl each time.

trawl camera

The trawl camera is attached to the net to monitor the fish entering the net.

The next piece of the net to hit the water is the “kite” which is secured to the head rope.  Here,  a series of sensors is attached to help the scientists gather data about the condition of the net including depth, size, and shape underwater. The major acoustic sensor, called the “turtle,” can tell if the fish are actually going into the net.

AWT Net

Close-up view of the AWT scale model to highlight the kite and the turtle that ride at the top of the net. The third wire holds the electrical wires that send data from the turtle to the bridge (courtesy of Teacher at Sea).

Once the kite is deployed, a pair of tom weights (each weighing 250 lbs), are attached to the bridal cables to help separate the head rope from the foot rope and ensure the mouth of the net will open.  Then, after a good length of cable is let out, the crew transfers the net from the net reel to the two tuna towers and attach the doors.  The doors create drag to ensure the net mouth opens wide.

The scientists use acoustic data to determine at what depth they should fish, then the OOD (Officer on Deck) uses a scope table to determine how much cable to let out in order to reach our target depth.  Adjustments to the depth of the head rope can be made by adjusting speed and/or adjusting the length of cable released.

The scientists use the acoustic data sent from the “turtle” to determine when enough fish are caught to have a scientifically viable sample size, then the entire net is hauled in.

Turtle

The turtle that can relay information to the science team about the number of fish collected.

Once on board, the crew uses a crane to lift the cod end over to the lift-table.  The lift-table then dumps the catch into the fish lab where the fish get sorted on a conveyor belt.

Net with Haul

Net with haul

Personal Log:

The Oscar Dyson needed to pick up materials for a net repair so we headed into Prince William Sound towards Valdez.  The area was spectacular.

Julia Harvey

Here I am in Prince William Sound

The sun was out and the skies were blue for most of the day.  Although we have had very calm seas, we have been under clouds for most of the last few days.

Enjoying the Sun

A handful of people gathered at the bow of the ship to enjoy the sun and the sights.

The absolute highlight of the day was spotting Dall porpoises and filming them bow surfing.

Here are snapshots of the day.  The area was so impressive that I have several hundred pictures.  Here are just a few:

porpoise

Still shot of Dall porpoise

sea otters

Verification that I did see sea otters

glacier

The sun shining bright on the Anderson glacier visible as we left Prince William Sound

Columbia glacier

The ship was just close enough to see Columbia glacier.

Click here to learn more about the Columbia glacier and to watch the changes to the glacier over time.

glacier

Look close to see the wall of ice of the Columbia glacier at the water’s edge.

Prince William Sound

Prince William Sound

Prince William Sound

Prince William Sound

Prince William Sound

Prince William Sound

Prince William Sound

Prince William Sound

I am reminded of the Exxon Valdez oil spill devastation.

Did You Know?

The Exxon Valdez (oil tanker) ran aground on Bligh Reef in Prince William Sound, Alaska on March 24, 1989.

Bligh Reef

This is the location where the Exxon Valdez hit the Bligh Reef.

 

The amount of oil spilled into this pristine environment exceeded 11 million gallons of crude oil and affected over 1300 miles of shoreline. According to OCEANA, as many as 2,800 sea otters, 300 harbor seals, 900 bald eagles and 250,000 seabirds died in the days following the disaster.

Jodi, who works the night shift with me, grew up in Cordova, Alaska and as a child remembers the smell of the disaster and the fears in her town (many were fishermen).

Has the area recovered? Part of the settlement with Exxon established a fund to support research.  Read more.

 

4 responses to “Julia Harvey: Here Fishy Fishy/Prince William Sound, August 1, 2013

    • The weather has cleared as we head towards Yakutat Bay. I should be able to get some gorgeous shots but may need to stay up tomorrow.

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