Anne Mortimer: Cam-trawl, July 14, 2011

NOAA Teacher at Sea
Anne Mortimer
Onboard NOAA Ship Oscar Dyson
July 4 — 22, 2011 

Mission: Pollock Survey
Geographical area of cruise: Gulf of Alaska
Date: July 14, 2011

Weather Data from the Bridge
Conditions: sunny and windy
Air Temperature: 10.1 ⁰C
Sea Temperature: 7.6 ⁰C
Wind direction: 237 ⁰C
Wind speed: 20 knots
Wave height: 2-3 ft.
Swell height: 5-6 ft.

Science and Technology Log

My last blog I said that I would talk more about the cam-trawl. This technology was created by scientists working on the pollock survey. The purpose behind the cam-trawl is to be able to put a net in the water with an open cod-end (basically a net with an opening at the end), and have images of the number, species, and size of fish that went through the net. Of course, sometimes some fish would have to be brought on deck so the otoliths and stomachs could be taken back to the lab in Seattle. Overall, this could eliminate taking so many research-based fish and/or invertebrate samples. When cam-trawl is used on acoustic-trawl surveys, the echograms can be matched up with the stereo-camera  images which can provide more data about the distribution of fish or other marine organisms in the water.

How the cam-trawl works: it is a stereo-camera system that takes snapshots of whatever comes through the net. These images allow the research team (including me on this leg) to determine the approximate number, species (some, not all), and size of fish that go through the net.

cam-trawl image
This still image from the cam-trawl shows a salmon and pollock against a black “curtain.”

The pictures are taken at the same time, but because of the slight difference in camera position, they look similar but not identical. You can mimic this with your eyes by looking at an object with only your right eye, then switching to looking with only your left eye. Did you see the same object but from a slightly different perspective? This is called disparity, or parallax (astronomers often use parallax to estimate the distance of far-away stars or other celestial objects). The program that was written for the cam-trawl (also by this research team) can then calculate the approximate size of the fish based on their relative positions.

In this photo, I’m using the cam-trawl measuring program to measure a sample of fish.
This screen shot shows the stereo-images and the yellow measurements that I’ve added. Using the lengths that I’ve chosen for the program, it calculates the approximate length (in meters) of the fish.

Personal Log

After several windy days with lots of swell, I’m happy to be in calmer waters. I’ve been working on the computer for some of the time which doesn’t go well with swell. I have also found it to be very tiring and tense on my body to be in constant motion and prepared to grab whatever I can to stay upright. I can’t tell you how hard it is to use a treadmill or take a shower in rough seas! BUT, for the time being, it’s calm and I just watched a great sunset over Kodiak island with a few humpback whale blows in the distance. If you are still wondering about the salmon in the picture above, it’s a chum!

Species Observed
humpback whales
northern fulmars
tufted puffins
black-footed albatross
storm petrels
porpoises (yesterday)

Dana Tomlinson: Day 22, March 22, 2002

NOAA Teacher at Sea

Dana Tomlinson

Aboard NOAA Ship Ka’imimoana

March 1 – 27, 2002

Date: Friday, March 22, 2002

Lat: 1°S
Long: 91°W
Seas: 2-4 ft.
Visibility: unrestricted
Weather: partly cloudy
Sea Surface Temp: 82-86°F
Winds: light airs
Air Temp: 86-79°F

Today makes exactly three weeks on the Ka’imimoana. And this will be my last Daily Log from it. What a day it was. It was truly a perfect day. The weather was crystal clear and warm with very little breeze. The waters are so flat it’s hard to believe you’re on an ocean. Since we are closing in on the Galapagos, we are seeing more animal life: two hugs pods of porpoises and a few different kinds of birds. Seeing the birds is nice. We have seen very few on this trip. Dr. McPhaden feels this could also be an indicator of El Niño since the waters are warmer, the fish may be fewer and, therefore, the birds have less to eat.

Everyone is very excited about reaching the Galapagos first thing tomorrow morning. The scientists have prepped and are ready for the buoy recoveries/deployments back on the 95°W line north of Galapagos. The crew was busy getting their work done so they can have some well-deserved time off (Ian and Dane were welding at sunset down on the fantail – it looked beautiful with the setting sun behind them). All hands worked very diligently on the leg down here and the CO is very glad to be able to give them some quality time in a port most have never seen before.

As for me, this is a farewell to the KA. Dr. Kermond, Dr. McPhaden and I will be leaving the ship here to spend a couple of days on Santa Cruz. I will continue to write my logs, but won’t have access to a computer until I get back to San Diego. So, in about a week, please check the website again for the finale to my trip. I thank Cmdr. Tisch and his wonderful crew of dedicated, professional workers for making me feel just like one of them, and giving me the opportunity to bring the valuable work they do to the world, as well as experience what it is like to be a scientist for a while. This experience can only help to make me a better teacher with what I can bring to my students. Thanks to NOAA for a win-win situation. And now I’m off to pack as much into two days in the Galapagos as I can! Stay tuned……………

Question of the Day: 

Here’s a no-brainer: did I have fun and learn a lot on the KA? You’re darn right I did. It was truly the experience of a lifetime.

Answer(s) of the Day: 

From Wednesday: Amy has 6 hours between CTD’s if she’s doing them every degree. It’s about 60 miles to a degree. And the ship goes about 10mph. From Thursday: Once again, knowing that 1 degree is about 60 miles, when you count up the degrees, you get almost forty. That would be 2400 miles and Mrs. Mackay’s class in San Diego got it almost right on the money. Super job, you all!

Til I return from the Galapagos,
🙂 Dana

Dana Tomlinson: Day 21, March 21, 2002

NOAA Teacher at Sea

Dana Tomlinson

Aboard NOAA Ship Ka’imimoana

March 1 – 27, 2002

Date: Thursday, March 21, 2002

Lat: 1.5°S
Long: 95°W
Seas: 5-8 ft.
Visibility: unrestricted
Weather: mostly cloudy with isolated rainshowers
Sea Surface Temp: 82-86°F
Winds: SE 10-15 knots
Air Temp: 83-70°F

Today was a day of mostly rainshowers, in actuality, with intermittent spurts of sun. The skies were pretty dramatic. The day was a pretty typical day at sea on the KA. The crew members were all doing their chores around the ship. The scientists spent the morning in preparation. Brian could be found splicing nylon cord together, Nuria was inputting data, etc. There is a buoy already outfitted on board, ready to be deployed after the ship leaves the Galapagos and continues to move northward on the 95°W line.

We had some delightful visitors this afternoon – a group of porpoises slowly made their way from the port side forward of the bow, to the bow, and then slowly drifted off to starboard. This occurred while the scientists were visiting the buoy at 2°S 95°W, so the ship was stopped. Once again, the bearings in the anemometer on this buoy were shot, so the scientists switched the anemometer with a new working one. It was a quick trip out and back and the ship continues to make very good time. We will be getting into the Galapagos much earlier than expected (Saturday morning). The cliche is true, eh? All good things must come to an end, for this Teacher at Sea anyway.

Question of the Day: 

This will be the last real question of the day, since I will only be at my email address until early Saturday morning. So, I’ll make you think. Starting at the 8°N point on the 110°W line and traveling down to the 8°S point on the 110°W line, and then traveling east to the 95°W line and going north to the equator, how many nautical miles is that? Keep in mind that 1° is about equal to 60 nautical miles. Get out the pencil and paper and go for it!!

Answer of the Day: 

I even stumped Cmdr Tisch on this one! We’ve decided a round number on what it costs to run the Ka’imimoana every day is about $20,000. It’s difficult to tell exactly. I did find out about how much fuel they use every day. Give up? About 2200 gallons. Fill ‘er up!

Til tomorrow,
🙂 Dana