We arrived around 9:00pm on Thursday and immediately started fishing. We use two types of gear: otter trawls and fish pots. We fish at depths that range from ~150meters to ~200meters in depth. The icefish and the red blooded notothenioids are benthic; they sit on the bottom, which is why we need to do bottom trawls to catch them.
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The otter trawl is being hauled up onto the deck. The metal doors help to hold the net open while it is being pulled through the water. It takes about 20 minutes for the net to reach the bottom, we trawl for 15 minutes and then another 20 minutes to bring the net up to the surface.
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Here you can see the entire net hauled up on deck; the cod-end of the net is the part of the net that holds the fish that are caught. You can see the enlarged cod end that holds our catch. Where we were fishing we were hauling up a lot of macroalgae, so most of what is in the net is algae, not fish.
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We set lines of four fish pots and fill a bait bag (the orange sack in the photo above) with mackerel and sardines. We set the pots and haul them back up 24 hours later. In each pot we generally catch 0-8 fish, and we set a total of 16 pots. We use the fish pots to catch primarily the red-blooded Antarctic fish,
Notothenia coriiceps (below).
The common name of
N. coriiceps is the yellow belly rockcod.
When you lift the operculum and look in the gill chamber of a red-blooded fish you can see the gills. The gills are red because of the presence of red blood cells that contain hemoglobin. Hemoglobin is an oxygen binding protein that transports oxygen through the body. The only adult vertebrate that do not have hemoglobin are the icefish, which is the group of fish we are studying. I'll show a photo of icefish gills in the next post, but icefish do not have red blood because they do not have hemoglobin or red blood cells.
But, back to the fish pots.... When we haul up the pots, there are amphipods that are feeding on the bait.
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| The bait bags are covered with amphipods, which are a type of crustacean. |
Below you can see a close-up of a bait bag; the amphipods have scavenged the "meat" off the mackerel and sardine bait, leaving only the skeleton... pretty cool, huh?
