Emily Whalen: Trawling in Cape Cod Bay, April 29, 2015

NOAA Teacher at Sea
Emily Whalen
Aboard NOAA Ship Henry B. Bigelow
April 27 – May 10, 2015

Mission: Spring Bottom Trawl Survey, Leg IV
Geographical Area of Cruise: Gulf of Maine
Date: April 29, 2015

Weather Data:
GPS location:  42^○51.770’N, 070^○43.695’W
Sky condition:  Cloudy
Wind: 10 kts NNW
Wave height: 1-2 feet
Water temperature:  6.2^○ C
Air temperature:  8.1^○ C

Science and Technology Log:

On board the Henry B. Bigelow we are working to complete the fourth and final leg of the spring bottom trawl survey. Since 1948, NOAA has sent ships along the east coast from Cape Hatteras to the Scotian Shelf to catch, identify, measure and collect the fish and invertebrates from the sea floor. Scientists and fishermen use this data to assess the health of the ocean and make management decisions about fish stocks.

Today I am going to give you a rundown of the small role that I play in this process. I am on the noon to midnight watch with a crew of six other scientists, which means that we are responsible for processing everything caught in the giant trawl net on board during those hours. During the first three legs of the survey, the Bigelow has sampled over 300 sites. We are working to finish the survey by completing the remaining sites, which are scattered throughout Cape Cod Bay and the Gulf of Maine.  The data collected on this trip will be added to data from similar trips that NOAA has taken each spring for almost 60 years.  These huge sets of data allow scientists to track species that are dwindling, recovering, thriving or shifting habitats.

At each sampling station, the ship first drops a man-sized piece of equipment called a CTD to the sea floor. The CTD measures conductivity, temperature and depth, hence its name.  Using the conductivity measurement, the CTD software also calculates salinity, which is the amount of dissolved salt in the water.  It also has light sensors that are used to measure how much light is penetrating through the water.

While the CTD is in the water,  the deck crew prepares the trawl net and streams it from the back of the ship.  The net is towed by a set of hydraulic winches that are controlled by a sophisticated autotrawl system.  The system senses the tension on each trawl warp and will pay out or reel in cable to ensure that the net is fishing properly.

Once deployed, the net sinks to the bottom and the ship tows it for twenty minutes, which is a little more than one nautical mile. The mouth of the net is rectangular so that it can open up wide and catch the most fish.  The bottom edge of the mouth has something called a rockhopper sweep on it, which is made of a series of heavy disks that roll along the rocky bottom instead of getting hung up or tangled.  The top edge of the net has floats along it to hold it wide open.   There are sensors positioned throughout the net that send data back to the ship about the shape of the net’s mouth, the water temperature on the bottom, the amount of contact with the bottom, the speed of water through the net and the direction that the water is flowing through the net.  It is important that each tow is standardized like this so that the fish populations in the sample areas aren’t misrepresented by the catch.   For example, if the net was twisted or didn’t open properly, the catch might be very small, even in an area that is teaming with fish.

After twenty minutes, the net is hauled back onto the boat using heavy-duty winches.  The science crew changes into brightly colored foul weather gear and heads to the wet lab, where we wait to see what we’ve caught in the net. The watch chief turns the music up and everyone goes to their station along a conveyor belt the transports the fish from outside on the deck to inside the lab. We sort the catch by species into baskets and buckets, working at a slow, comfortable pace when the catch is small, or at a rapid fire, breakneck speed when the catch is large.

After that, the species and weight of each container is recorded into the Fisheries Scientific Computing System (FSCS), which is an amazing software system that allows our team of seven people to collect an enormous amount of data very quickly. Then we work in teams of two to process each fish at work stations using a barcode scanner, magnetic lengthing board, digital scale, fillet knives, tweezers, two touch screen monitors, a freshwater hose, scannable stickers, envelopes, baggies, jars and finally a conveyor belt that leads to a chute that returns the catch back to the ocean.  To picture what this looks like, imagine a grocery store checkout line crossed with an arcade crossed with a water park crossed with an operating room.  Add in some music playing from an ipod and it’s a pretty raucous scene!

The data that we collect for each fish varies.  At a bare minimum, we will measure the length of the fish, which is electronically transmitted into FSCS.  For some fish, we also record the weight, sex and stage of maturity.  This also often includes taking tissue samples and packaging them up so that they can be studied back at the lab.  Fortunately, for each fish, the FSCS screen automatically prompts us about which measurements need to be taken and samples need to be kept.  For some fish, we cut out and label a small piece of gonad or some scales.  We collect the otoliths, or ear bones from many fish.

Most of the samples will got back to the Northeast Fisheries Science Center where they will be processed by NOAA scientists.  Some of them will go to other scientists from universities and other labs who have requested special sampling from the Bigelow.  It’s like we are working on a dozen different research projects all at once!

 

 

 

Something to Think About:

Below are two pictures that I took from the flying bridge as we departed from the Coast Guard Station in Boston. They were taken just moments apart from each other. Why do you think that the area in the first picture has been built up with beautiful skyscrapers while the area in the second picture is filled with shipping containers and industry? Which area do you think is more important to the city? Post your thoughts in the comment section below.

 

 

 

 

 

 

 

 

 

Personal Log

Believe it or not, I actually feel very relaxed on board the Bigelow!  The food is excellent, my stateroom is comfortable and all I have to do is follow the instructions of the crew and the FSCS.  The internet is fast enough to occasionally check my email, but not fast enough to stream music or obsessively read articles I find on Twitter.  The gentle rocking of the boat is relaxing, and there is a constant supply of coffee and yogurt.  I have already read one whole book (Paper Towns by John Greene) and later tonight I will go to the onboard library and choose another.  That said, I do miss my family and my dog and I’m sure that in a few days I will start to miss my students too!

If the description above doesn’t make you want to consider volunteering on a NOAA cruise, maybe the radical outfits will.  On the left, you can see me trying on my Mustang Suit, which is designed to keep me safe in the unlikely event that the ship sinks.  On the right, you can see me in my stylish yellow foul weather pants.  They look even better when they are covered in sparkling fish scales!

That’s it for now!  What topics would you like to hear more about?  If you post your questions in the comment section below, I will try to answer them in my next blog post.