NOAA Teacher at Sea
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: May 1, 2015
Weather Data from the Bridge:
Winds: Light and variable
Air Temperature: 6.2○ C
Water Temperature: 5.8○ C
Science and Technology Log:
Earlier today I had planned to write about all of the safety features on board the Bigelow and explain how safe they make me feel while I am on board. However, that was before our first sampling station turned out to be a monster haul! For most stations I have done so far, it takes about an hour from the time that the net comes back on board to the time that we are cleaning up the wetlab. At station 381, it took us one minute shy of three hours! So explaining the EEBD and the EPIRB will have to wait so that I can describe the awesome sampling we did at station 381, Cashes Ledge.
Before I get to describing the actual catch, I want to give you an idea of all of the work that has to be done in the acoustics lab and on the bridge long before the net even gets into the water.
The bridge is the highest enclosed deck on the boat, and it is where the officers work to navigate the ship. To this end, it is full of nautical charts, screens that give information about the ship’s location and speed, the engine, generators, other ships, radios for communication, weather data and other technical equipment. After arriving at the latitude and longitude of each sampling station, the officer’s attention turns to the screen that displays information from the Olex Realtime Bathymetry Program, which collects data using a ME70 multibeam sonar device attached to bottom of the hull of the ship .
Traditionally, one of the biggest challenges in trawling has been getting the net caught on the bottom of the ocean. This is often called getting ‘hung’ and it can happen when the net snags on a big rock, sunken debris, or anything else resting on the sea floor. The consequences can range from losing a few minutes time working the net free, to tearing or even losing the net. The Olex data is extremely useful because it can essentially paint a picture of the sea floor to ensure that the net doesn’t encounter any obstacles. Upon arrival at a site, the boat will cruise looking for a clear path that is about a mile long and 300 yards wide. Only after finding a suitable spot will the net go into the water.
The ME70 Multibeam uses sound waves to determine the depth of the ocean at specific points. It is similar to a simpler, single stream sonar in that it shoots a wave of sound down to the seafloor, waits for it to bounce back up to the ship and then calculates the distance the wave traveled based on the time and the speed of sound through the water, which depends on temperature. The advantage to using the multibeam is that it shoots out 200 beams of sound at once instead of just one. This means that with each ‘ping’, or burst of sound energy, we know the depth at many points under the ship instead of just one. Considering that the multibeam pings at a rate of 2 Hertz to 0.5 Herts, which is once every 0.5 seconds to 2 seconds, that’s a lot of information about the sea floor contour!
The stations that we sample are randomly selected by a computer program that was written by one of the scientists in the Northeast Fisheries Science Center, who happens to be on board this trip. Just by chance, station number 381 was on Cashes Ledge, which is an underwater geographical feature that includes jagged cliffs and underwater mountains. The area has been fished very little because all of the bottom features present many hazards for trawl nets. In fact, it is currently a protected area, which means the commercial fishing isn’t allowed there. As a research vessel, we have permission to sample there because we are working to collect data that will provide useful information for stock assessments.
My watch came on duty at noon, at which time the Bigelow was scouting out the bottom and looking for a spot to sample within 1 nautical mile of the latitude and longitude of station 381. Shortly before 1pm, the CTD dropped and then the net went in the water. By 1:30, the net was coming back on board the ship, and there was a buzz going around about how big the catch was predicted to be. As it turns out, the catch was huge! Once on board, the net empties into the checker, which is usually plenty big enough to hold everything. This time though, it was overflowing with big, beautiful cod, pollock and haddock. You can see that one of the deck crew is using a shovel to fill the orange baskets with fish so that they can be taken into the lab and sorted!
At this point, I was standing at the conveyor belt, grabbing slippery fish as quickly as I could and sorting them into baskets. Big haddock, little haddock, big cod, little cod, pollock, pollock, pollock. As fast as I could sort, the fish kept coming! Every basket in the lab was full and everyone was working at top speed to process fish so that we could empty the baskets and fill them up with more fish! One of the things that was interesting to notice was the variation within each species. When you see pictures of fish, or just a few fish at a time, they don’t look that different. But looking at so many all at once, I really saw how some have brighter colors, or fatter bodies or bigger spots. But only for a moment, because the fish just kept coming and coming and coming!
Finally, the fish were sorted and I headed to my station, where TK, the cutter that I have been working with, had already started processing some of the huge pollock that we had caught. I helped him maneuver them up onto the lengthing board so that he could measure them and take samples, and we fell into a fish-measuring groove that lasted for two hours. Grab a fish, take the length, print a label and put it on an envelope, slip the otolith into the envelope, examine the stomach contents, repeat.
Some of you have asked about the fish that we have seen and so here is a list of the species that we saw at just this one site:
- Atlantic wolffish
- Acadian redfish
- Alligator fish
- White hake
- Red hake
- American plaice
- Little skate
- American lobster
- Sea raven
- Thorny skate
- Red deepsea crab
I think it’s human nature to try to draw conclusions about what we see and do. If all we knew about the state of our fish populations was based on the data from this one catch, then we might conclude that there are tons of healthy fish stocks in the sea. However, I know that this is just one small data point in a literal sea of data points and it cannot be considered independently of the others. Just because this is data that I was able to see, touch and smell doesn’t give it any more validity than other data that I can only see as a point on a map or numbers on a screen. Eventually, every measurement and sample will be compiled into reports, and it’s that big picture over a long period of time that will really allow give us a better understanding of the state of affairs in the ocean.
It seems like time is passing faster and faster on board the Bigelow. I have been getting up each morning and doing a Hero’s Journey workout up on the flying bridge. One of my shipmates let me borrow a book that is about all of the people who have died trying to climb Mount Washington. Today I did laundry, and to quote Olaf, putting on my warm and clean sweatshirt fresh out of the dryer was like a warm hug! I am getting to know the crew and learning how they all ended up here, working on a NOAA ship. It’s tough to believe but a week from today, I will be wrapping up and getting ready to go back to school!