Chelsea O’Connell-Barlow: To Fish Or Not to Fish?…A Question of Sound, September 4, 2017

NOAA Teacher at Sea

Chelsea O’Connell-Barlow

Aboard NOAA Ship Bell M. Shimada

August 28 – September 13, 2017

Mission: Pacific Hake Survey

Geographic Area of Cruise: Northern Pacific Ocean

Date: 9/04/2017

Weather Data from the Bridge:

Latitude: 53.59.372N

Longitude: 133 32.484W

Temperature 59 F

Wind 12.5 knots

Waves 1-2 feet

Science and Technology Log

After spending a few days observing what happens in the Acoustics lab and listening to our Chief Scientist Rebecca (RT) Thomas and acoustician Julia Clemons brainstorm aloud, I had one overriding question…”How do you decide when to fish?”

I asked RT this question and it is a multi-factored decision for sure, but seems like the decision could be broken down into 3 parts: what we see, what we know and what is currently happening.

What they see when deciding to fish or not is an echogram created by three acoustic sounders on the ship that send out 3 different frequency wavelengths. The image shows a relatively low frequency 18 kHz, 38 kHz, and a longer wavelength of 120 kHz. Keep in mind that sound travels faster in water than on land so this is a great way to gather information while being minimally invasive to the marine environment.

The backscatter, sound that scatters off of an object or its echo, on the echogram is what they look at to determine what marine life is on the transect we are scouting. As the sound wave bounces off of material in the ocean be it rock, flora or fauna it will create a spot or colored pixel on the echogram. Hake has a particular “look” of backscatter. When the echogram shows this particular hake sign we move in the direction of fishing.

Of course they only know what “hake sign” is because of gathering evidence throughout the course of this multi-year survey. During this survey they have created a huge reference database of hake sign and sign of other integral species to the hake’s environment, for example Euphausiid sp., one of the hake’s favorite food. RT and Julia have both interpreted many echograms and fished to confirm the identity the organisms that created the sign.  They are able to rule out images on the echogram until they find the backscatter that most resembles what they have historically experienced as hake.

The third part of this decision making process is the most variable…what is currently happening. As the boat travels and the sounders are sending out the trio of wavelengths an image of the ocean shelf is created. The scientists are able to see topography and measure the depths of the shelf’s different contours. The Shimada is a 209 foot long boat weighing over 2,400 tons. When deciding to trawl for hake that we suspect are present because of backscatter sign in the echogram the scientists and Commanding Officer always consider the depth to bottom, contours, wind and the maneuverability of the ship. Deploying the Aleutian Wing Trawl (AWT) net to catch hake is a task that involves cooperation and communication between the deck crew, Boatswain, bridge officers and the Chief Scientist. When RT sees a sign on the echogram that she wants to fish, she and Commanding Officer Kunicki quickly discuss the approach, wind direction and depth to get an idea on how the net will be affected and how close the ship can get to the exact sign that she wants to sample.

This is my bare bones description of the process that goes into deciding when to fish on Leg 5 of the Pacific Hake Survey. Stay tuned to see what we learn from comparing the echogram of sign to the actual yield from the AWT fishing net.

For more specifics from NOAA on the Bell M. Shimada’s acoustic and trawling capabilities https://www.omao.noaa.gov/learn/marine-operations/ships/bell-m-shimada/about

Personal Log

This ship is filled with kind, creative and industrious people. I am reminded of this constantly and appreciate this often. To me it is astounding to consider all the work and thought that is involved in a fifteen-day research survey at sea. This is a science survey so there are specific tools, computer programs and labs that must run well. To me, coming in with a science focus, this is most obvious. What I am blown away by are all of the additional layers that work together to make science even possible on this successful voyage. There are several teams at play: engineering, technology, deck, science and the bridge officers. Engineers are constantly maintaining engines, generators (this ship has 4), plumbing, ventilation and so much more. I had a tour today with Engineering Chief Sabrina Taraboletti that I am still trying to process through.

Technology is handled by one person on this ship. He maintains and trouble shoots computers in the acoustics lab, the bridge, the chemical lab and even found time to help maximize signal for the Fantasy Football draft. The deck crew is as versatile as anyone on this ship. We have two types of nets that we fish with. The deck crew is responsible for getting the nets out to fish and back in with the catch. Way easier said than done when we are talking about over a ton of weight with net, camera, chain, and doors. On top of all their other responsibilities many of the men in the deck crew have been helping out in the galley (kitchen) on this leg of the hake survey. Larry is the chief steward (chef) on board this leg and he typically has someone working with him but not on this leg of the Survey. So in addition to working their 12 hour shift, many of the deck crew have been working with Larry to prep food, clean up the mess (dining area), do dishes or even create their own personal specialties for dinner. We have been spoiled by Matt’s rockfish, Joao’s fresh salsa and soups and our Operations Officer Doug’s amazing BBQ. Liz and I even got to help out and make some donuts with Larry. Eating is great on the Shimada!

The Shimada team is rounded out with the bridge crew made up of 4 officers. The officers on a NOAA ship have a foundation of science knowledge and extensive nautical training. Before we go fishing I get to participate in the marine mammal watch up in the bridge. As I look for whales, dolphins and other marine mammals near the boat I can listen to the Captain and officers working their magic. We have had an incredibly smooth trip thus far which I credit to our Officers and of course Mother Nature.

Did You Know?

Crazy cool catch of the day…can you figure out what type of fish this is?

Here is a clue…they have specially adapted cells called photocytes that create light producing organs called photophores.  The photophores run along the sides of the fish and help them to lure prey and attract mates.

Answer:

This is a Viperfish.

Viperfish live in the deep ocean and migrate vertically as the day goes on in order to catch prey. They typically live around 1,500m (4,921 ft) and in the night will end up around 600m (1,969 ft) at night. This particular fish appears to have photophores along its mouth but it is difficult to be 100% sure from this specimen.