NOAA Teacher at Sea: Story Miller
NOAA Ship: Oscar Dyson
Wave Swell: 5 – 6 feet
We started the morning by dropping a CTD (Conductivity, Temperature, Depth) and monitoring the salinity of the ocean, the temperature, and depth. Salinity, the amount of salt in the ocean, is important as the higher the salinity the more conductivity it possesses. Conductivity is necessary for many things such as scientific observation and for marine life. For example, the transducer we use to send pings of energy through the ocean relies on conductivity and sound tends to travel better through waters with a higher salinity. Sound traveling through water is also important for animal communication. Salinity can influence the presence of fish species due to the different ways they process the water (think about freshwater fish versus saltwater fish). Water temperature is important for observing climate change. Because salinity affects the density of water (My students: remember the lab where we floated the egg with salt), it can change the temperature at which the ocean freezes. A simple example is that plain distilled water freezes at 0°C but the ocean at the surface typically begins to freeze at -1.1°C. As the water depth increases, so does the salinity and therefore as the temperature decreases the ocean does not freeze. We also launched an expendable bathythermograph (XBT) which measures depth and temperature at a deeper level than the CTD. These two tests are used to characterize the Bering Sea shelf environment.
Approximately six hours later we spotted our first school of pollock. We shot the AWT and caught a lot of two year-old pollock and a few one year-olds! The water temperature where they were located was about 2.5°C. I quickly donned my foul-weather gear and ExtraTuffs (rubber boots) and was ready to sort fish. From one sample, we sorted the fish, separating the small one year-olds from the two year-olds. Second, we cut open the fish to locate ovaries or testes. The males and the females were separated into bins and we fondly refer to the males as “Blokes” and the females as “Sheilas.” We measured their length and entered the data into the computer. With another sample, we sexed the fish, measured their length, extracted stomach samples to see what they are eating and to collect plankton samples, and last we extracted the otoliths. Otoliths are ear-bones and they are used to measure age, very much like looking at tree rings to find the age of a tree.
The walleye pollock observation has been conducted each summer since 1979 by the Midwater Assessment and Conservation Engineering (MACE) as a program of the Alaska Fisheries Science Center (AFSC) to estimate pollock abundance and distribution. The Oscar Dyson is following a route consisting of evenly spaced (20 nautical miles) parallel transects to estimate the pollock population over the entire Bering Sea shelf. So if you are tracking the ship using “Ship Tracker” this is why we are sailing in a strange pattern!
Yesterday I was slightly anxious because I chose to experiment with my sea tolerance and not take the seasickness medication. Of course the seas decided to be a little more active as we began our pollock transit. Combined waves reached 10-12 feet and I just ate plain rice and bread for supper! Today the waves are more gentle and my stomach is very excited about that! Up on the “Bridge” where the controls for driving the boat are located tends to rock with the waves the most and it was fun to try and type my blog while attempting to keep my balance! However, by the end of the day, I was well enough to help “supervise” ENS Payne in the construction of chocolate chip cookies during my time off!
Dissecting the fish was incredibly fun and I cannot wait to have my students try their hands at it! I was very excited to extract otoliths because those particular bones were the fossils we used to identify the different fish species at the Always Welcome Inn in Baker City, Oregon when I was conducting research in college! To see those fossils go to the following website:
Tomorrow we will be crossing the International Dateline and theoretically will have traveled into the tomorrow of tomorrow. The Oscar Dyson has become my time machine!
Animals Viewed Today:
Fork-tailed Storm Petrels
Something to Ponder:
Have you ever ordered pollock? How many of you have eaten fish sticks or surimi? Most likely you have eaten pollock and thought it was cod! Where does pollock fit in the food chain in the wild?
Also, how do you know when you have crossed the International Dateline? (Hint: check the data at the beginning of my blogs.)