Northwest Fisheries Science Center

Student Questions & Answers

Answers to Questions from:

Mr Rabinowitz's
5th Grade Math and Language Arts
Sonoji Sakai Intermediate School
Bainbridge Island, Washington

Question (Alex): Answer:
How far down will you be going?
The ROPOS can go to a depth of 5000 meters but the deepest we will be sending it during our cruise will only be about 800 meters.

Question (Jake):
How does the sound tracking work?
We use sound to see what the bottom of the sea looks like as well as to see what is in the water. We send sound out from transducers mounted on the bottom of the vessel and wait for sound to be reflected back to us. When it hits the sea floor and bounces back to the transducers, the speed and intensity of the reflection gives us a picture of the bottom. Because we send many frequencies of sound out we get a very detailed picture. When we are looking for animals in the water we also look at the sound as echoes that are reflected from their bodies. Actually, we look in many cases at the reflections from the air bladders in things like fish. This can give us a picture of the number and size of fish.

Question (Annika):
How far from shore are you going?
We will be about 81 nautical miles offshore from Los Angles, California. The area we are surveying is south of San Nicolas Island.

Question (Shannon):
How does the ROV work?
The ROV is like a little underwater car or boat but one that is powered from the ship. It is connected to the ship by a wire that can send power down to the ROV and allows things like video to be sent back to the shop. No one rides in the car. The driver or pilot is safe and dry sitting on the ship. The car is lowered from the ship in a metal cage that we call a garage. The little car then drives out of its garage when it reaches the area we want to study. Power that goes down the wire runs motors that drivesthe car through the water. The pilots can steer the car from the computer room on the ship. They steer by looking at a video from cameras on the front of the ROV. There are also mechanical arms that the pilots can move and use to pick up samples of rocks and animals and put them in a box ready to bring back to the ship. Once the dive is over the car goes back into the garage and it is pulled to the surface and loaded back on the ship.

Question (Mr. R.):
Do fish make sounds?
Yes many do. Some of our colleagues are trying to estimate the number of fish by listening for the sounds they make.

Question (Max):
When you are using sound waves does it affect the fish?
The frequencies of sound that we use do not seem affect the fish.

Question (Andrew & Nathan):
What species of fish are you studying?
We are studying a group of fish known as groundfish. They include things such as cod, rockfish and flatfish.

Question (Eric):
How much pressure will the ROV withstand?
It can dive to 5000 meters. That is a pressure of about 500 times the pressure at sea level.

Question (Bridget):
What is the salinity of the water?
The salinity of seawater varies quite a bit from the surface to the bottom. If you look at the website for the research vessel were are working from ( and click on the area that is called scientific data you will see that there is a lot of data posted there. Open a file called 17406001-2.PDF in the area called CTD data plots. You will see a graph of salinity, temperature and fluorescence as it changes with depth. The green line shows a plot of salinity and you can see that the water is fresher (less saline) near the surface and has it highest salinity near the bottom.

Question (Rory):
How fast does the ROV go?
Not really fast, only about 3.5 knots

Question (Signe):
What experiments are you doing at the bottom?
We are not doing any experiments. We have hypotheses or questions that we are answering by taking samples and making observations. One of the questions that we are trying to answer is do certain species of fish prefer certain types of rocks, sand or sediment.

Question (Logan):
How long can the ROV stay down?
Since it is powered from the surface and controlled by people at the surface (no one actually rides in the vehicle) it could stay down forever. The longest time it has been in the water is 54 hours.

Question (Sophie):
How far from Port Angeles is Cherry Bank?
About 1087 nautical miles by water!

Question (everyone):
What is the density of seawater?
The density of seawater changes depending on things like its temperature and salinity. For instance cold seawater is denser than warm water and the cold water tends to sink below the warm water.

Question (Rachel):
Construction of the ROV?
Most of the ROV is constructed of aluminum but what allows it to go so deep is the use of titanium cases for the cameras and computers. The ROV was constructed by International Submarine Engineering in Port Moody, British Columbia, Canada.

Question (Mr. R.):
Why the name Cherry Bank?
We were wondering the same thing! None of us know, but we do know that it has two names. The other name is Dall Bank.

Question (Casandra):
What does it feel like being on the ocean for a while?
This ship is a not too small and the weather has been good. This makes the ship feel pretty stable and it is not rocking around too much. Sometimes when the sea is a little rougher the ship rocks back and forth and you have to be careful not to slip. The old saying on ships is that you should have one hand for the ship and one hand for you. They mean that you have to be ready to hold on to keep yourself steady. It is interesting eating and working together 24 hours a day. We work around the clock and that is a different. Some of us work at night and some during the day.

Question (Nicole):
Why are you studying plankton?
We are studying plankton because they are the small plants and animals on which many larger animals depend on for food.

Question (Nico):
How many samples are you taking?
We will probably take less than 50 samples of things like rocks using the ROV but we will take hundreds of samples of seawater and plankton.

Question (Alex):
Are there other liquids in water?
There are many things that are dissolved in water. Salts, minerals, and gases, such as oxygen and carbon dioxide, are all in seawater.

Question (Gracie):
What are you eating on the cruise?
We have several cooks who are feeding us VERY well. For lunch we had bratwurst and for dinner we had the choice of pork chops or mahi mahi with a wonderful sauce. (I am trying to convince the cook he should give me the recipe.)

Question (Graham & Charlie):
What have you seen so far in the way of fish?
We don't start using the ROPOS until tomorrow. That means so far we have not seen any fish.

Question (Jacob):
Why are you studying Cherry Bank?
Cherry Bank has both interesting geology and biology. It was a good opportunity to have scientists from both disciplines work together.

Question (Chris W.):
Are you trying to reduce pollution?
No, that is not one of the goals of this research.

Question (Erich):
What sensors does the ROV have?
The ROV has three cameras, a temperature probe and a salinity probe.

Question (Daniel):
How is the ROV powered?
It is powered by an electric motor turning a hydraulic pump.

Question (John):
What kind of zooplankton are you studying?
We are studying primarily copepods.

Question (Taylor):
How do you carry on your experiments from the surface, from underneath?
All the scientists stay on the ship at the surface and put the different instruments and sensors into the water while we stay safe and dry on the ship.

Question (Haley):
What other species of animals have you seen besides fish so far?
We have seen one whale, and several different kinds of sea birds. We also found some unexpected passengers on the ship today: a peregrine falcon and a northern pygmy owl!

Question (Mr. R.):
How do you control the variables in your experiments?
We are not doing any experiments during this research. We are making observations to test certain hypotheses.