Anne Mortimer: Swell Sleeping, July 12, 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 12, 2011

Weather Data from the Bridge
Conditions: Foggy and windy, changing to partly 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

Last night we had a “splitter” catch. The scientists found an area that they couldn’t pass up fishing, so at about 9pm the trawl was put in the water. The 540 ft. long Aleutian wing trawl brought in lots of pollock and Pacific ocean perch, a type of red-colored rockfish.  A catch is called a splitter when it is so big it won’t all fit on the table. To get a weight of the whole catch, the deck crew use a crane to weigh the net, then empty it out.  Then the catch is dumped into a bin that is split in two parts. Only one part of the bin is then raised, putting a sub-sample on the table to be worked-up. It took a long time to process all of the catch. We separated the species on a conveyor belt system, then the messy stuff happens. I mentioned that otoliths and stomachs are collected, but I don’t think I emphasized just how gross this can be. To sex the fish, we use a scalpel to slice the fish down the side, then look for larger pink-colored ovaries or a stringy, twisted looking testes. To collect otoliths, the fish skull is cut just behind the eyes and cracked open. The otoliths are then picked put with tweezers. If you are really good at pulling otoliths, you can pull both at once, which can be very challenging. My double-take record is only 2 in a row, but I’ve pulled both at once at least 5 times now!  The last messy thing is stomach collection. You can imagine what this entails, I’m sure. I’m happy to say that I’ve only had to hold the baggie for the stomach, not cut any out! Processing this catch took several hours– we didn’t end until after 1am.

red rockfish
This red-colored fish is a pacific ocean perch, or P.O.P. to a fish biologist.
Pacific ocean perch

When I am not processing a trawl or on the bridge observing, I have been working to annotate some videos from the cam-trawl. The cam-trawl is a stereo-camera system that takes snapshots of whatever comes through the net. This cam-trawl was designed by several of the scientists on the pollock survey. They are hoping it will help lead to less actual fish samples needed if the images can accurately provide evidence of species, numbers, and sizes. Some trawls would still have to be taken aboard for sexing, weights, and otolith and stomach samples.  Annotating the images basically means that I click through the images, counting each species of fish or invertebrate (usually jellies) that I see. This can very tedious, but the whole idea of the project is very exciting. I’ll talk more about the cam-trawl and this technology in my next blog.

Personal Log

Yesterday was my first real encounter with rocking and rolling on the Oscar Dyson. The winds were blowing at about 30 knots (that’s about 35 mph), and there was a lot of swell. Swell waves are long-wavelength surface waves that could have originated from a storm hundreds or thousands of miles away. The combination of these two made for a very rocky ride until we hid behind an island until sunrise. Since I go to bed at 4:30am, it wasn’t long before the boat was headed back out to unprotected waters, and I was rudely awakened by the swell. To say I didn’t have a swell sleep is an understatement. I had to take a nap this evening to compensate for my lost hours!


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