Mission: Walleye Pollock Survey
Geographical Area of Cruise: Gulf of Alaska
Weather Data from the Bridge (as of 17:00 Alaska Time):
Wind Speed: 9.54 knots
Temperature: 15.7 C
Humidity: 83 %
Barometric Pressure: 1017.9 mb
Current Weather: The winds have decreased and we are not moving as much. The weather report calls for an increase to the winds with 7 ft swells on Wednesday. But maybe it will die down before it reaches us.
Science and Technology Log:
We only will fish during daylight hours. The sun is now setting before 10:00 pm and rising around 5:30 am. And even though we are not fishing between sunset and sunrise, science continues. At nightfall, we break transect and Jodi begins her data collection.
The Sustainable Fisheries Act mandates an assessment of essential fish habitat. This is in conjunction with stock assessments of groundfish. Jodi’s research involves integrating multibeam accoustic technology to characterize trawlable and untrawlable seafloor types and habitat for managed species.
A bottom trawl survey is conducted every other year in the Gulf of Alaska. The goal is to better identify seafloor types using multibeam acoustics. This would help improve groundfish assessment, and limit damage to habitat and trawling gear.
The Gulf of Alaska survey area is divided into square grids.
On this cruise we are conducting multibeam mapping in trawlable and untrawlable grid cells. A grid cell is divided into 3 equidistant transects for a multibeam survey. Jodi directs the ship to follow these smaller transect lines. While the ship is following the transects lines, the multibeam sonar is active and data is collected.
The SIMRAD ME70 is the multibeam sonar that Jodi is using for her research. There are 6 transducers on the ship that will send out a fan of 31beams of varying frequencies. The strength of their return (backscatter) can be analyzed for sea floor type. Looking at the diagram below, you can see the differences in backscatter clearly in the range of 30 to 50 degrees (away from straight down).
Silts will have a very weak backscatter and rock will have a strong backscatter.
After the transects are completed, Jodi and Darin complete 1 – 3 camera drops to record visually how the seafloor appears. This camera below will be lowered to the ocean floor and video footage will stream to the computer for 10 minutes. Then the camera is brought up.
Last night, Darin gave me the opportunity to operate the camera drop. After a bit of instruction, it was showtime. I am very grateful for the chance to explore the seafloor.
Here is what I saw at 190 meters.
For more photos of my drop camera experience, see the end of this blog.
CTD (conductivity, temperature, depth) drops are conducted in the grid as well. Data that are gathered are used to correct for the speed of sound under varying conditions of the ocean.
The next day, Jodi processes the data from the ME70. The bottom detection algorithm (a series of calculations) removes backscatter from the water column (from fish).
Each frame product represents 5 minutes of seafloor. The following are outcomes from the algorithm and represent angle dependent data. The images below, show backscatter on the left and bathymetry on the right.
Then Jodi takes into account a number of factors such as results from the CTD, motion of the boat (offset, attitude, pitch, roll), and tides. These uncertainties are applied.
Then she mosaics the data.
The color image above represents the depth and the bottom image provides information on seafloor substrate.
The footage from the camera drops is also reviewed for more evidence of the seafloor substrate and to look for objects that would snag trawl nets.
I really appreciate Jodi taking the time to educate me on her research. Her passion for her work is evident. I look forward to seeing where her research leads.
So who actually works the night shift (4pm to 4 am) in the “cave”. Jodi Pirtle, Paul Walline and Darin Jones are the three scientists I have been lucky to work with during my cruise.
I discussed Jodi’s work on the ship in the science section. She has an extensive educational background. She earned a BS in Biology from Western Washington University in Bellingham and then a MS in Environmental Science from Washington State University in Vancouver. Then she earned a Ph.D in Fisheries from the University of Alaska at Fairbanks. Her thesis was on ground fish habitat on rocky banks along the US west coast. And her dissertation was based on red king crab nursery habitat. She just finished her postdoc at the University of New Hampshire Center for Coastal and Ocean Mapping where her work applied multibeam acoustics to study trawlable and untrawlable seafloor types and groundfish habitat in the Gulf of Alaska. She is now working on groundfish habitat suitability modeling after she was selected to be a National Research Council NOAA postdoc at the Alaska Fisheries Science Center Auke Bay Lab in Juneau. Jodi continues to integrate multibeam acoustics in her research at ABL.
Jodi was born and raised in Cordova, Alaska which we came near when we were in Prince William Sound. I have enjoyed listening to her speak of growing up in Alaska. There are no roads out of Cordova, so imagine traveling with a sports team in high school? I will not forget how she described the Exxon Valdez oil spill to me from the eyes of herself at 11 years old.
I have greatly appreciated her knowledge of the creatures we bring up in the nets. She has an eye for finding the hidden gems like the chaetognath (arrow worm).
Jodi enjoys cross country skiing, snow boarding, berry picking, hiking and yoga. She introduced me to beautiful ripe salmon berries back on Kodiak.
Darin is a MACE (Midwater Assessment & Conservation Engineering) scientist who earned his BS in Marine Biology from the University of North Carolina at Wilmington and then his MS in Fisheries Resources form the University of Idaho at Moscow. His master’s work involved disease resistance in bull trout. He spent 5 years collecting fishing data as an observer aboard commercial fishing boats in Alaska. He also tagged cod on George’s Bank and worked at several conservation fish hatcheries before moving to Seattle to work for MACE. Darin is part of the team to assess the biomass of the walleye pollock in the Gulf of Alaska.
I have heard that Darin played in a band with some MACE colleagues but they broke up because one of them moved. Maybe there will be a reunion tour.
He is a surfer and has surfed on Kodiak but his favorite surf spot so far was in Costa Rica. Darin is an easy-going guy who I often call Scott because he reminds me so much of a colleague at school. Darin has patiently explained my tasks to me and helped me learn what I am really doing. And he supported me as I did my first camera drop.
Paul is a native of Washington state and completed his academics there as well. He earned a BS in Oceanography and a Ph.D in Fisheries Oceanography from the University of Washington. For 20 years he worked at the Israel Limnological and Oceanographic Institute. He was involved in managing the water quality in Lake Kinneret. His role was to estimate the number of fish to determine their affect on water quality. Paul accomplished this by developing acoustics surveys of fish stocks in Israel. Lake Kinneret, also known as the Sea of Galilee, provides Israel with 40% of its drinking water.
In 2000, Paul moved back to Seattle and is working as a fisheries biologist for MACE.
I have been fortunate to see photographs that Paul has taken both on this trip and elsewhere. He has an incredible talent for finding beauty.
I am writing this as we are tossing and turning in ten foot swells. According to Paul, it doesn’t matter if the swells get any bigger because the effect is the same. His calmness, knowledge and expertise remind me a lot of my dad.
As you can see, I worked with amazing, brilliant individuals. The night shift rules. We had awesome teamwork when a haul needed to be processed.
And then we slept through the fog and awoke to beautiful sunsets (on some days).
Did You Know?
Glacial runoff changes the color of the ocean. Compare the two photos. The one at the bottom is near a glacier.
Animals Seen Today:
The bottom trawl that was brought up right when I began work, contained three types of sharks. The smaller ones were spiny dogfish and spotted spiny dogfish. The big one was a salmon shark. Check out the video.
To read more about salmon sharks and to monitor their migration pattern, check out the content on Tagging of Pacific Predators website. Click here: TOPP
My Drop Camera Experience