NOAA Teacher at Sea
Marla Crouch
Aboard NOAA Ship Oscar Dyson
June 8-26, 2013
Mission: Pollock Survey
Geographical area of cruise: Gulf of Alaska
Date: June 12, 2013
Weather Data from the Bridge: as of 2300
Wind Speed 12.30 kts
Air Temperature 6.10°C
Relative Humidity 98.00%
Barometric Pressure 1,009.6mb
Latitude: 54.22N Longitude: 164.65W
Science and Technology Log
Here I am all decked out in my rain gear in the wet lab, ready to sort the catch of our first bottom trawl. Quite a fashion statement, don’t you think?
Walleye Pollock (latin name Theragra chalcogramma), a fish that lives both on and above the seafloor, is the main target of the Pollock survey, but information about other sea life is also collected. When we start sorting the catch from this bottom trawl, the primary population is Pacific Ocean Perch (POP, Sebastes alutus). The POP is a member of the Scorpaenidae or scorpionfish family and has poisonous spines. When handling the fish I have to be really careful of the very sharp spines to avoid injury. Fortunately, the POP’s teeth are not as formidable as their spines, so I can grab them by the mouth to safely move them around.
After we sort the catch the total weight of each species is recorded. We collect additional biological data on the POP, by first sorting them by “Blokes” or “Sheilas.” I’ll let you figure out what characterizes Blokes and Sheilas. After the sorting, each fish in the sample is laid on an electronic measuring board (mm) to determine and record the length of the fish. In this survey the length of the fish is measured from the tip of the mouth to the center of the “v” in the tail, this is know as the fork length.
Other populations being sampled are plankton and the jellyfish that were collected in a Methot trawl. Here Abigail McCarthy is sorting two types of zooplankton krill (also called euphausiids) and jellyfish that were collected. Once the sorting is completed, then the quantity and weight of the krill and the jellyfish is recorded. One of the areas Abby is investigating is if there is a correlation between the krill population and the location of baleen feeding whales. Abby wonders how far away the whales can smell or sense dinner? Who can tell me which species of whales are baleen feeders?
Another tool the scientists use to collect data is a tethered stereo camera that takes 10 pictures/second. Using the pictures I am counting and sorting fish by species. Look at the pictures and you’ll see a Gorgonia sea fan and a basket star. The camera has a stationary photo length, so objects closer to the camera appear bigger. In the picture with the sea fan, you are also seeing krill. You can use the pairs of images from the stereo cameras to measure the size of the organisms that appear in the images.
Personal Log
When the Oscar Dyson sailed from Dutch Harbor we head west to the Islands of Four Mountains, a cluster of volcanic isles. On one isles is Mt. Cleveland, which on May 5th was actively spewing lava. As we pass, Mt. Cleveland is quietly shrouded in dense cloud cover. Darn, cannot check eruption off my “Want to see” list. I don’t think I’ll see an aurora either as the cloud cover has been thick.
Science aboard the Oscar Dyson runs 24/7. Both the Dyson’s crew and the science team work in twelve hour shifts. For the Dyson’s crew the day is broken into two shifts, from midnight to noon and noon to midnight. The science team shifts are from 4 a.m. (0400 hrs.) to 4 p.m. (1600 hrs.) and 1600 hrs. to 0400 hrs. I am on the 1600hrs to 0400hrs shift; morning and night run all together. A note here, when the scientists collect data the time stamp is Greenwich Mean Time (GMT). GMT is eight hours ahead of us here in Alaska.
Did You Know?
I’ve discovered that you can slosh in your berth. Check out the next blog for “Surf Your Berth.”
