NOAA Teacher at Sea
Leanne Manley
Onboard NOAA Ship Delaware II
March 24 – 31, 2005
Mission: Atlantic Mackerel and Herring Survey
Geographical Area: New Jersey
Date: March 26, 2005
Weather Data
Latitude: 40° N
Longitude: 72° W
SOG (speed over ground – boat): 10.8 knots
Speed log (speed of boat through water): 10.2 knots
COG (course over ground – boat): 241?
Furuno3 (3 meters deep) temp.: 2.4? C
Air temp.: 3.7? C
TSG (thermosalinograph) conductivity: 29
TSG Salinity: 31.4 ppt. (3.1%)
Fluorescence value (phytoplankton): 253 µg/L
Swells: 2- 3 feet (varies)
Science and Technology Log
Yesterday’s shift ended by releasing and retrieving the first CTD (conductivity, Temp and depth) probe. We hit the area of study (diagram after this log) and are starting the transects. It takes about a 4 hour steam to complete each transect. At the start of each transect the CTD probe is released to take its abiotic measurements (as stated in its name). This information is important to understand what conditions the fish thrive in and also to note any density-dependent or independent limiting factors.
This survey is near the Southern coast of New Jersey and about 10 – 15 miles off the coastline. Mike Jech stated that we are a bit too shallow. We will most likely move the transects slightly east to hit deeper waters. The last CTD probe hit a depth of only 11 meters on the west side of the transect (near the coastline).
After our fist CTD probe readings last night Mike took Deanelle “D”, Mike (volunteer) and I up to the computer room in the bridge to decipher some of the acoustic readings that the Simrad collected. I didn’t realize how difficult it was to interpret the readings. The acoustic readings are taken with 3 different wavelengths: 18 kHz, 38kHz and 128 kHz. Due to the different frequencies of these wavelengths different colors are assigned to each level of kHz. The difficulty lies when they overlap. Also, since a species-specific fish-finder is only a hope for the future, it is hard to interpret from the data what types of fishes are being detected.
“D” is a PhD student studying mechanical engineering at MIT. She specializes in long-range acoustics, so she was asked to join Mike J’s crew to learn and help out with this survey. She is one who is hopeful to design a long-range species-specific fish finder.
The early morning seems best to write log entries; so, the first quarter of my shift is the standard time for these entries. Shortly, we will release the CTD again and also take a water sample at that depth. The water sample is collected using a 4” PVC tube with spring inserts attached to the ends, or doors of the tube. Before the tube is released the spring loaded “doors” are tied open. Once the tube is at the desired depth the spring loaded “doors”, which are attached to a cord that someone has onboard the ship, are pulled releasing the springs and closes the doors. Upon return to the surface, the water is bottled and given to the National Marine Fisheries upon return to port for testing. The rectangular box represents the area of survey/study. The lines transecting the rectangle, creating a serpentine, is the course of the DELAWARE II. The CTD probe is released at the beginning of each transect, or line. The trawl, if the hydraulics were working, would have been released when the Simrad detected fish along this transect.
Personal Log
It is nice not to have e mail bombarding me every minute – The exercise bike is still a favorite…but the dehydration due to the Dramamine cramps muscles—I like discussing past, present and future research projects with the crew. The cold is a nice change. I’ve written 13 ideas for lessons applicable to this research…now I just have to write the procedures for each. Last, but not least, Snood is a cool game.
