September 6, 2012 A Nice Break
As we were wrapping up our station last night it began to snow, and as we moved NW toward Wrangel Island during the night, we were once again rocking and rolling; some found sleep difficult. However, when we woke up for our station at 7 AM, we found that the wind and waves had died down. What a treat to be able to walk without hanging on and, for me, to be able to sit in a chair with my computer on my lap and work. For the past week, it's been nearly impossible with the ship's movement pushing my chair, my computer, and me across the room.
To make an already good day better, Jackie got her first cores of the cruise and the sun came out! Not only did Jackie get her cores, but the fish teams were able to trawl and the entire biology station "worked." Of course, that didn't last long as we moved away from the protection of the island once the station was complete and we started rolling again. Oh well, it was a nice break.
Due to the weather, the two teams working on fishes have not had a lot of luck putting their trawls over, so they were excited to get their trawls into the water today. As soon as we finished our benthic work, the first of the trawl nets went in off the stern. Brenda Holladay, a research scientist at the University of Alaska Fairbanks (UAF), in the school of Fisheries and Ocean Sciences talked to me about the work of her team. She's on board with Kelly Walker, a fisheries technician and Andres Lopez, curator of fishes at the Museum of the North in Fairbanks. In order to collect samples for the fish ecology team to study the ecology, distribution and abundance of fishes in the Chukchi Sea, they deploy a bongo plankton net, a beam trawl, and an otter trawl, all off the stern. The bongo trawl (two plankton nets attached to a frame with openings that resemble bongo drums) picks up fish eggs, larval forms of fish, and other zooplankton, the beam trawl is a small meshed bottom trawl that opens to one meter above the substrate and picks up juvenile and small adult fishes as well as epibenthos, and the otter trawl opens a little higher off the bottom and is larger meshed to avoid catching the smaller gastropods (snails), bivalves (clams) and substrate (mud!). The bongo trawl catch is split into two parts, one of which is preserved in formalin so the fish eggs and larvae can be examined after the cruise. The zooplankton project (see 9/2) will examine the other part of the bongo catch, which has larger planktonic animals than the finer-meshed nets they deploy. The bottom trawl catches are sorted on the cover of the hold on the back deck (see 9/1), and Brenda's team will search for fishes among the more abundant epibenthos. As the sorting comes to an end, the fishes are moved into the laboratory to be examined further. Once they have their fish specimens identified, measured and weighed, several people want the fish and/or pieces of them. Brenda´s team will look at trace elements in the otoliths, bony structures in the ear that are laid down in layers as the fish ages (somewhat analogous to tree rings). At the core, the otolith shows a record of what was in the environment when the fish was hatched from its egg, and the outer edge of the otolith indicates the environment of the capture location. Interestingly, these otoliths are often seen in souvenir shops in the form of earrings! The team will also look at developmental stages of the fish and, from the eggs and larval fish in the plankton tows, they can get an idea of where the fish were spawned, where they´ve moved, and which geographic region and habitats they are most abundant. Ultimately, they would like to be able to identify population changes (e.g. are populations moving, expanding), but they are still establishing baseline data to see where fish species are at the present time. Combined with work being done in the northeast Chukchi Sea and on other cruises, they hope to compare fish communities with water masses and examine a host of other variables that may impact fisheries management decisions.
There's additional work related to the trawls. Andres not only helps with the work of the team, he is also looking at fish population genetics. He takes a small tissue sample of representatives of several fish species, and brings the samples back to UAF for analysis. While Brenda´s team is primarily focused on the more abundant fish, Kitty Mecklenburg's team is particularly interested in rare fish that might appear in the trawls. I'll fill you in on Kitty's work soon.
Journal Update for 7 September 2012:
After a busy night of sampling, with our biology station starting at 4:30 AM, we completed a combined biology/geology station by 6:30 PM. We got another good core for sectioning and the trawls were once again a success. The daylight gave me a chance to get a picture of the teams pulling in the beam trawl. It's large, bulky, and often very heavy with organisms and mud.