Jennifer Fry: March 13, 2012, Oscar Elton Sette

NOAA Teacher at Sea
Jennifer Fry
Onboard NOAA Ship, Oscar Elton Sette
March 12 – March 26, 2012

Mission: Fisheries Study
Geographical area of cruise: American Samoa
Date: March 13, 2012

Pago Pago, American Samoa 

Science and Technology Log:

The Teacher at Sea program in the South Pacific is going swimmingly.

Nighttime Midwater Cobb Trawls:

I’m on the night watch for the first week of our time at sea. Our research day starts at 8:30 p.m. The scientific team of 7 is trawling for bioluminescent fish, myctophids throughout the night.  We trawl at several different depths then bring the net up to the surface.  We sort the catch into five categories.

1.  Myctophids

2.  Non-Myctophids

3.  Cephalopods: octopus/squid

4.  Crustaceans: shrimp/lobster/krill

5.  Gelatinous zooplankton: salps/jellies

5.  Misc. zooplankton

Then we weigh measure and record all the contents of the net, Last night was our first attempt. The first trawl began at 9:00 p.m.   With the NOAA crew members’ help, the net was lowered into the water after securing several tracking devices, TDR and Netminds, at different places on the net, which measured the longitude, latitude, water’s temperature and depth.   The clock started and the net trawled with 350 meter line out from the ship.  The trawl lasted for 30 minutes at which time the winch operator brought the line into 100 meters where the clock started for another 30 minutes.

In all, the net was positioned at 350 meter from the ship for 30 minutes and at  100 meters for  another 30 minutes.

The second trawl attempt occurred around 1:30 a.m. The winch stopped, appearing to overheat, and couldn’t bring the net up to the surface.  When it finally was retrieved, the time factor was no longer a constant, but became a variable. The total trawl time exceeded the 30 minutes.   The scientists took very careful notes and  made sure to record that the second net had been in the water for much longer that the first experiment/ attempt/ round.  Scientists refer to each experiment as “replicate”  By running many experiments in the same manner, ensures accuracy and careful data collection. They want to keep  the constants and variables all standardized.

We got to bed around 4:30 in the morning.

Safety First aboard at all times:  I was just awakened to a false alarm fire drill, which got my heart pumping, that’s for sure.  It’s a good thing we have these drills for practice and accuracy.

The day was spent sleeping and acclimating to the new nighttime schedule.

The team of scientists working the Night Cobb Trawls re-convened at 8:30 p.m.  We began the first trawl around 9:00 p.m. and continued the second at approximately 1:30 p.m.

Midwater Cobb Trawl #1  Tow #1   The data collected included:

Name of fish: Numbers Count Volume (milliliters) Mass (grams)
Myctophids 173 300 310
Non-Myctophids 296 85 75
Crustaceans 67 16 20
Cephalopods: 19 44 30
Gelatinous zooplankton 7 24 40
Misc. zooplankton n/a 80 110

 

Authors

Leave a Reply