Alicia Gillean: Adventures in Dredging; July 1, 2012


NOAA Teacher at Sea
Alicia Gillean
Aboard R/V Hugh R. Sharp
June 27 – July 7, 2012

 

Mission:  Sea Scallop Survey
Geographical area of cruise: North Atlantic; Georges Bank
Date: Sunday, July 1, 2012

Weather Data from the Bridge
Latitude: 40 48.43 N
Longitude: 068 04.06W
Relative Wind Speed: 8.9 Knots
Air Temperature: 17.61 degrees C
Humidity: 92%
Surface Seawater Temperature: 16 degrees C

Science and Technology Log

Dump dredge

Dumping dredge onto sorting table

My last shifts have been a mix of HabCam work and dredging. Remember, dredging is when we drag a heavy-duty net along the ocean floor for fifteen minutes, then bring it up and record what ocean critters we catch.  Dredging involves a lot more physical work and is much dirtier than flying the HabCam, so time goes much faster when we are dredging and it’s exciting to see what we will catch.  However, it is also kind of sad to see all the animals we bring up in the dredge, because most of them are dead or will soon be dead.  You can watch a video about sea scallop dredging here and here.

There are three two-week legs to this sea scallop survey.  I am on the last leg.  Before the first leg began, a computer program, with the assistance of a few people, decided which spots in the sea scallop habitat we should dredge and fly the HabCam.  These points were all plotted on a computerized map and the chief scientist connects the dots and decides the best route for the ship to take to make it to all the designated stations in the available time.

Here’s how our typical dredging process works:

About 10 minutes before we reach a dredge station, the Captain radios the lab from the Bridge (fancy name for the place at the top of the ship where the Captain and his crew work their magic) to let us know we are approaching our station.  At this point, I get on a computer in the dry lab to start a program that keeps track of our dredge position, length of tow, etc.  I enter data about the weather and check the depth of our dredge station.  When the engineer and Captain are ready, they radio the lab and ask for our depth and how much wire they need to send out to lower the dredge to the ocean floor.  I get the wire length from a chart hanging in the dry lab that is based on the depth of the ocean at the dredge site and use the radio to tell the engineer, who lets out that amount of wire until the dredge is on the ocean floor.  When the dredge hits the ocean floor, I use the computer program to start timing for 15 minutes and notify them when it is time to bring the dredge back up.

Alicia sorting fish

Alicia sorting the haul

The lab technicians and engineer raise and dump the dredge on a giant metal table, then secure it for the scientists to come in and begin sorting the haul.  Meanwhile, the scientists get dressed in foul weather gear to prepare for the messy job ahead.  That means I’m wearing yellow rubber overalls, black steel-toed rubber boots, blue rubber gloves, and a lovely orange lifejacket for each dredge.  Sometimes I add a yellow rubber jacket to the mix, too.  Science is not a beauty contest and I’m grateful for the protection!  Each scientist grabs two orange baskets, one large white bucket, and one small white bucket and heads to the table. The lab technicians shovel the catch toward each scientist as we sort.  Scallops go in one orange basket, fish go in the white bucket, crabs go in the small white bucket (sometimes), and everything else goes into the other orange basket.  This is considered “trash” and is thrown back overboard, but the watch chief keeps track of how many baskets of “trash” are thrown overboard during each haul and enters it into a computer database along with other data. After sorting the haul, much of the data collection takes place in lab called a “van”.

Research Van

Research “van” where we gather data from haul

The fish are sorted by species, counted, weighed, sometimes measured, and entered into a special computer system that tracks data from the hauls.  Sometimes we also collect and count crabs and sea stars.  The baskets of sea scallops are counted and weighed, and then individual scallops are measured on a special magnetic measuring board.  You lay the scallop on the measuring board, touch the magnet to the board at the end of the scallop, and the length is automatically entered into the database.    Some hauls have lots of sea scallops and some don’t have very many.  We had a couple hauls that were almost completely sand dollars and one that was almost completely sea stars.  I learned that sea stars can be quite slimy when they are stressed. I had no idea!

Sand dollar dresge

Dredge haul with LOTS of sand dollars

Sometimes my watch chief, Sean, will select a subsample of five sea scallops for us to scrub clean with a wire brush.

Alicia scrub scallops

Alicia scrubbing scallops at about 11pm

Next, we weigh and measure all five sea scallops before cutting them open to determine the gender.  We remove the gonad (the reproductive organ) and weigh it, then do the same with the “meat” (the muscle that allows the scallop to open and close its shell and the part people like to eat).  All of this information is recorded and each scallop is given a number.  We write the number on each shell half and bag and tag the shells.  The shells and data will be given to a scientist on shore that has requested them for additional research.  The scallop shells can be aged by counting the rings, just like counting the rings on a tree.

Alicia scrub scallops 2

Scrubbing scallops is dirty work!

Meanwhile, other people are hosing off the deck, table, buckets, and baskets used.  The dredge ends by shucking the scallops and saving the meat for meals later.  A successful dredge requires cooperation and communication between scientists, lab technicians, the Captain, and the crew. It requires careful attention to detail to make sure the data collected is accurate. It also requires strategic planning before the voyage even begins.  It’s an exciting process to be a part of and it is interesting to think about the different types of information that can be collected about the ocean from the HabCam versus the dredge.

Personal Log

Hallway to shower

Hallway to the shower and bathroom

Living on a ship is kind of like living in a college dorm again: shared room with bunkbeds, communal shower and bathroom down the hall, and meals prepared for you.  I can’t speak to the food prepared by the steward (cook) Paul, as I haven’t been able to eat much of it yet (I’m finally starting to get a handle on the seasickness, but I’m not ready for tuna steaks and lima beans just yet), but I do appreciate that the galley (mess hall) is open all the time for people to rummage through the cabinets for crackers, cereal, and other snacks. There’s even an entire freezer full of ice cream sandwiches, bars, etc.  If my husband had known about the ice cream, he probably would have packed himself in my duffel bag for this adventure at sea!

Taking a shower at sea is really not much different than taking a shower at the gym or in a college dorm… in the middle of a small earthquake. Actually, it’s really not too bad once you get used to the rock  of the ship.  On the floor where the scientists’ berths (rooms) are, there are also two heads (bathrooms) and two showers.  The ship converts ocean water into water that we can use on the ship for showering, washing hands, etc.  through a process called reverse osmosis.  Sea water is forced through a series of filters so small that not even the salt in the water can fit through.  I was afraid that I might be taking cold showers, but there is a water heater on board, too!   We are supposed to take “Navy showers”, which means you get wet, press a button on the shower head to stop the water while you scrub, then press the button to turn the water back on to rinse.  I’ll admit that I find myself forgetting about this sometimes, but I’m getting much better!

Shower

Shower on Hugh R Sharp

Today there was about an hour and a half of “steam” time while we headed to our next dredge location and had nothing official to do.  Some of the people on my watch watched a movie in the galley, but I decided to head to one of the upper decks and enjoy the gorgeous views of ocean in every direction.  I was awarded by a pod of about 15 common dolphins jumping out of the water next to the ship!

I’m starting to get a feel for the process of science at sea and am looking forward to the new adventures that tomorrow might bring!

Question of the Day

Which way do you think is the best way to learn about the sea scallop population and ocean life in general: dredging or HabCam?  Why do you think so?

 You can share your thoughts, questions, and comments in the comments section below.

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