Groundtruthing - Using data to support educated guesses

Wednesday, March 4, 2015 by Adam Baukus

These are video clips from two different cameras I deployed as part of our acoustic survey work.  Our acoustic equipment can give us information about lots of different types of organisms in the water column, and using different frequencies of sound we can start to make educated guesses about what the species are.  We also go out and sample with nets and cameras to verify exactly what species are in the area, this is called groundtruthing. 

Video Player Here: https://www.youtube.com/watch?v=Hkb_gu56sGE&feature=youtu.be

The first clip is from a drop camera.  This is a camera and light setup that is on a long cable that we drop over the side of the boat.  We can see the images real time on a computer on the deck of the boat, and we lower it until we are close to the bottom.  It was a calm flat day when we shot this video and it seemed like the boat was not moving, but as you can see from the footage, the tidal currents move the boat over the bottom rather fast, and even small waves make the camera go up and down dramatically.  This is a good way to see some small schools of fish near the bottom, take a look at some of the sessile organisms in the area like anemones and sponges, or look for any large egg masses left on the seafloor by spawning fish.

The second clip is from a camera that we mounted on our sampling trawl net.  We fish with the net in the area of our acoustic survey to see what types of fish are around.  There are different types of fishing nets designed to catch different types of fish.  This net is designed to catch smaller, schooling fish like herring, and the net has a sorting grate in it which helps remove larger fish like cod or monkfish.  In the video, the fish that go through the grate end up being caught, and the fish that go up over the orange floats escape.  So this camera helps me see what fish are in the area that did not get caught in the net.  In this clip we see all sorts of fish including herring, butterfish, whiting, red hake, flounder and a couple lobsters!



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