NOAA Teacher at Sea
Aboard NOAA Ship Oscar Dyson
May 24 – June 2, 2012
- Mission: Fisheries Surveys
Geographical Area: Eastern Bering Sea
Date: May 24, 2010
Pollock Survey Begins
On Saturday, my watch began at 10:00 AM. Two of the scientists, Annette Dougherty and Kevin Bailey have watch from 4 AM until 4 PM. The other two scientists, Tiffany Vance and Steve Porter, have watch from 4 PM until 4 AM. I guess being the teacher they took pity on me and gave me half and half. Before getting to one of the stations, the scientists make sure that everything is ready. They lay out the bongo nets on the deck where they will be used. The bongo nets are two nets that from the top look like bongo drums. (See picture) There is an instrument attached to the bongo nets called a SEACAT that takes conductivity, temperature and salinity measurements during the tow. Inside the lab, buckets, bowls and tweezers are all laid out ready to be used.
As we approach each station, the bridge informs the scientists and survey technicians. The bongo nets have already been readied and are set to be deployed (put into the ocean) from the hero platform. When the OK is given, the nets are lifted by the hydrowinch to a point where they can be maneuvered over the rail and then they are lowered into the water. The nets are lowered until they are at 100 meters or 10 meters off the bottom. As they are lowered, the pilot of the boat keeps the wire at a 45° angle by moving the boat slowly forward. Once the nets reach their maximum depth, they are slowly brought back up again. ( I tried to upload a video showing the deployment and retrieval of the bongo, but it won’t work so I’ll show you the video when I get back.
When the nets clear the water, they are hosed down to get any organisms into the bottle on the end of the net (called the cod end.) The cod end is then removed and the contents of one net are poured into a bucket for sorting. The contents of the other net are preserved and sent to a lab in Poland where they use instruments to get a very accurate count of the Pollock.
Inside the chem lab, the contents of the bucket are scooped out and poured little by little into a mixing bowl. We then perform a rough count by removing the very small Pollock larvae and any other fish larvae and put them into a petri dish with cold water (the petri dish is placed on top of ice.) They are only a few mm long (averaging between 6-10mm.) Once we have gone through the entire contents, the Pollock larvae are counted, photographed and the length measured. They are then placed into a labeled vial with 95% ethanol. The other fish larvae are placed in a separate vial in 100% ethanol. They are kept in case another scientific team needs the data. The Pollock larvae will be sent to the scientists’ lab back in Seattle where they will perform further analysis on them. I’ll tell you more about that in the next blog.
Answers to your questions:
Annalise – The ship travels at 12 knots when we are going between stations.
Matt T– The ship is very safe. Drills are conducted every week. My first day on the ship, we had a fire drill and abandon ship drill. (See photo of me in my survival suit.)
Dan – The Oscar Dyson observes and records a number of environmental conditions. The bridge takes weather readings every hour and keeps them in a weather log. These include wind direction, wind speed, seawater temperature, air temperature, air pressure, cloud cover, sea swell height and direction. Conditions in the water are also constantly monitored such as temperature, conductivity, salinity, and amount of oxygen.
Olivia – The bongo tow is one way to get fish eggs. The mesh used on the bongo nets is very fine). It is able to filter out these very small larval fish and fish eggs, too.
Brittany – There is no specific number of fish that need to be caught for this experiment. Part of the experiment is to see how many larval fish there are. For our rough count, the scientists measure 20 larvae to get an estimate of their size. They will then look at the otoliths (small inner ear bones) to estimate their age.
Amy – Aside from the Pollock larvae in the nets, we have caught cod larvae, larval squid, fish eggs, amphipods, terapods, jellies, Euphausids or krill, copepods and the larvae of other fish. The nets are small enough that we don’t catch any large fish or other animals.
Josh W. and Jon – Joel Kellogg has the night shift, so I haven’t met him yet. Stephen Macri is not on this cruise so I can’t ask him your questions.
Questions for today
In your answers to the last blog, many of you researched the large animals that live here in the Gulf of Alaska. The most abundant organisms, however, are much smaller. Two organisms that are very important to the survival of the large animals here are copepods and Euphausids. The larval Pollock feed on the larval copepods that are called copepodites.
Find out what other animals feed on copepods and euphausids. Then, describe at least one food chain that includes copepods and one that includes krill. In your food chain start with a producer or autotroph Ex. Algae) and end with the highest level of consumer or predator (Ex. blue Whale)
Again, Please be sure to include the link to the website where you got your information. Answer the questions in your own words writing complete sentences with as much detail as you can.