Marla Crouch: I Bid You Adieu, July 14, 2013

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: July 14, 2013

Weather Data from the Bridge: as of 1700
Wind Speed 6.02 kts
Air Temperature 52.10°C
Relative Humidity 100.00%
Barometric Pressure 1,024.60  mb

Latitude:  57.16N   Longitude: 151.78W

Science and Technology Log

The 2013 Walleye Pollock Survey extends from the Isles of Four Mountains to Yakutat, Alaska.  As the crow flies that is a distance of 2371 statute miles.  By the time the Oscar Dyson reaches Yakutat the distance traveled will be over three times that distance.  The survey is completed in three segments, called legs; during the first leg of the survey we traveled 3448 nmi.  A nautical mile is longer than a statute mile, 1 nmi is equivalent to 1.15 statute mile.

Map of the Alaskan Coastline
Map of the Alaskan Coastline

When we were surveying the waters around the Shumigan Islands we frequently encountered large schools of juvenile pollock, identified as age 1.   I asked Patrick Ressler, the lead scientist on this leg, if this was a nursery area.  Patrick indicated that the science team would need to go back and review the data collected on previous surveys to determine if there was sufficient evidence to make that determination.  The high number of age 1 pollock is a good sign that the fish stocks are healthy.

In my “Gumbi Marla” blog I talked about NOAA’s Ship Tracker and the transects, or the course, the ship navigates during the survey.  Surveys are completed during daylight hours, as the pollock behave differently at night, by changing the depth at which they swim.  When the acoustics data show a school of pollock that the science team wants to fish the position is recorded and the science team communicates with the Dyson’s bridge officer about when they can safely return to the specific position to trawl the area.  When the bridge crew is ready to leave the current transect they contact the science team, the science team then records the time and the exact position where the Dyson left transect.  After the trawl is completed the Dyson returns to the exact position they left transect to continue the survey.  During night time hours one of the scheduled tasks was to use the camera to review areas of the sea floor that had previously been deemed “untrawlable” as the seafloor was to rocky and would snag or tear the nets.

One type of gas that is trapped in Earth’s lithosphere is methane.  Methane escapes the lithosphere under the seafloor through vents and along fault lines.  The screen shot of the acoustics monitor shows vertical columns believed to be methane.  One theory about the Bermuda Triangle is a massive release of methane that creates a massive bubble.  When the bubble bursts objects in the immediate area are sucked into the momentary void created by the bubble, and swallowed by the sea.

Acoustic image of probable methane seepage.
Acoustic image of probable methane seepage.

Personal Log

Trees, there are trees on Kodiak!  I saw trees for the first time in 18 days, and I realize that I have missed seeing trees.  It’s interesting that the first three people I talk to as we approach the island of Kodiak all ask if I saw the trees.  I guess I’m not the only one that has missed seeing trees.  Sometimes the simplest observation makes the biggest impression.

Thank you to the crew of the Oscar Dyson and Science Team and to NOAA for giving me a phenomenal experience with the Teacher at Sea Program. Many students will benefit from my experiences.  Pictured is the Science Team from Leg 1 of the Pacific Walleye Pollock Survey, from left to right:  Lead Scientist Patrick Ressler, Taina Honkelehto, Kresimir Williams, Rick Towler, Abigail McCarthy, Marla Crouch (that’s me), behind me is Charles Andersen and Mike Gallagher.

Science Team
Science Team

There were so many great experiences; I hope you enjoy the video giving you glimpses into the science, technology, sights and the Oscar Dyson.

 Thanks to everyone that made my experience possible!

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