Tom Jenkins: What is a Spring Bottom Trawl Survey? April 20, 2018


NOAA Teacher at Sea
Tom Jenkins
Aboard NOAA Ship Henry B. Bigelow
April 10 – 27, 2018

Mission: Spring Bottom Trawl Survey
Geographic Area: Northeastern U.S. Coast
Date: April 20, 2018

Personal Log

A few months ago, I learned about my selection to be a NOAA Teacher at Sea.  When I learned I was offered a spot aboard the Henry B. Bigelow to help with the Spring Bottom Trawl Survey, my immediate reaction was “Yes!  I will do it!” I then quickly googled Spring Bottom Trawl Survey as I unsure exactly what I would be doing on my 18 day research cruise.

So, what is it?  The standardized Northeast Fisheries Science Center (NEFSC) Spring Bottom Trawl Survey is annual event (an additional survey is conducted in the fall) that was initiated in 1968.  Its primary objective is to collect fishery-independent data during standardized research vessel surveys from Cape Hatteras to the Scotian shelf.   While out at sea, additional oceanographic and plankton data are collected. This allows for continuous monitoring of the health and status of marine resources and their habitat.

 

 

How is it planned?  The Chief Scientist will work with the ship’s officers to set a cruise track to a set of sampling locations that were randomly selected by a computer program (this eliminates bias).  A multitude of factors come into play while plotting the course for the day. These include: weather, time, the number of stations they would like to cover, the types of stations, as well as other factors.  Once the ship arrives at a station, several people aboard the vessel scout the location. A desirable sea floor (minimal slope, no obstacles, etc.), avoiding fixed gear (lobster pots for example), and minimal boat traffic are a few of the things that help them tow in a spot within the allowable radius from the original point.

 

 

What actually occurs once a towable spot is found?  Data from the location needs to be gathered as this will provide a reference for the scientists that will later be studying the organisms as well as the data mined from this specific spot.  This is done with a CTD (seen above). The ship’s crew will hoist this apparatus over the edge of the ship and lower this device to roughly 30 feet above the seafloor. Sometimes down to a depth of over 1,000 feet!   Knowing things like Conductivity, Temperature, and the Depth help researchers paint a more complete picture which will aid them in their effort to study and assess fish populations.

 

 

After both the preliminary data is gathered and the scouting is complete, the fisherman aboard the ship will kick it into high gear.  Fishing aboard the Henry B. Bigelow is an impressive feat of engineering.  Once in the water and fishing the net is about 36 feet across at the opening (the wings), and about 90 feet long; which is loaded with sensors, is fed out the back using a set of winches.  These reactive winches control the wires which manipulate the net to ensure the best trawl possible which will hopefully result in a representative sample for the science team to process (This system is known as “autotrawl” and it aims at maintaining equal pressure by both winches, enabling more consistent performance especially in rough weather, and also reduces the amount of damage due to of “hangs”).

 

 

Once out of the net, the organisms are then loaded into the checker pen.  A member of the science team will then slowly feed them onto the conveyor belt which then carries them inside the wet lab.  The other members of the science team will then sort the various species of marine life into buckets of various sizes. Each of the containers has an attached bar-code tag which is then scanned and associated with the species that is in the container.  This ensures that everything that comes off of the belt is accounted for during processing.

 

 

In the wet lab, there are three processing stations.  Once a bucket arrives at the work area, the tag will then be scanned into the computer will tell members of the science team the specific data as well as the specimens to gather.  Data includes things such as mass, length, sex, age structures (otoliths (a calcified part of the inner ear), illicium (the long fleshy filament attached to the forehead of anglerfish), & scales) and stomach contents whereas specimens can be the entire body or a specific part.  Examples of additional requested include things such as fin clips (DNA), and gonads (reproductive information).

 

 

After the specimens are processed, they are carefully preserved for later use.  Some things such as otoliths can preserved in an envelope whereas something like a stomach needs to be placed in a jar which is then filled with a fluid (formalin solution) that will keep its contents fresh.  Large freezers aboard the ship allow the science team to quickly freeze bagged specimens which will allow high quality samples to be shipped to research facilities; not only in northeast, but to laboratories all around the world.

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Night Shift Crew

(The amazing 12am-12pm team that teaches the Teacher at Sea)

Thank you for taking the time to read my blog.  As always, if you have any questions and/or comments, please feel free to post them below.

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