NOAA Teacher at Sea
Walter Charuba
Aboard R/V Savannah
July 18 — 29, 2011
Mission: Reef Fish Survey
Geographical Area: Southeast Atlantic Ocean
Date: July 21, 2011
Science and Technology Log
There is an old sailor’s proverb: “Red Sky at night, it will be bright” or “sailors take flight“ or something like that. I just know that I live by this saying and it has caused many a captain to throw away their weather charts. There was a beautiful red sunset last night and I stood at the bow or stern (I am down to two boat locations now) in complete admiration. However, when I started my shift in the morning there was a front moving in with rain clouds and lightning. I must admit I have been pretty calm most of the trip and this has not been due to the Dramamine. Seeing these clouds caused my imagination to get the better part of me, which of course would be the part that includes my brain. I had images of “The Great Wave” by Hokausai racing in my head. This outlook was ridiculous because there weren’t even white caps on the waves. The storm never hit us and the day turned out to be excellent.
Another reason last night was special was because I was able to view some dolphins at a very close distance. First Mate, Michael Richter, made it quite clear that no one was supposed to walk around the boat alone at night, especially the dark upper deck , and especially on the railings. So after daylight, we are limited to the lighted lower deck. As I was reviewing my constellations, the light seemed to attract these flying fishes. I do not know if this is true, because correlation isn’t always causation, but it looked true. As I was staring at the flying fishes, a large splash startled everyone. It was a spotted dolphin and a calf jumping for the flying fishes. The dolphins jumped around for about twenty minutes until we took off to our next destination. It was kind of like our own little Sea World, except natural. It was a perfect way to end the night.
Morning was the time to not only see, but capture, new creatures. My last blog described the deployment of traps, but now I will write about the retrieval of traps. Science Watch Chief, David Berrane termed this “action time.” The two flotation buoys we drop are significant because, after “soaking” a trap for 90 minutes, the boat returns to these devices and a crew member has to throw a grappling hook at a line between the buoys. We then quickly pull the buoys in next to the boat. The buoys are lifted up, the line is connected to a “hauler,” and a trap is pulled on board. This may sound simple but it is actually a five person task. The task is very intense and focused because people may trip over the buoys or ropes, or the trap’s line can snap due to weight or current. Hopefully the trap will be filled with fish and the cameras will record useful data from depths ranging from 25 to 83 meters. As soon as the trap is brought on board, the fish are collected and the cameras are disconnected.
The video survey of the reef is just as important as capturing fish, as cameras can assess the population of species that do not go in traps. Zeb Schobernd, the video watch commander, and I do salute him, downloads all the data on board for further viewing during the off season. Imagine all the viewing that has to be done? For instance fifteen videos were taken in one day of our ten day cruise, and there are four or five missions a year. To avoid reef video insanity, the data is viewed in thirty second intervals which is still a great deal of work.
Fish brought on board are immediately classified to species, and then measured individually. Measurement data are called “length frequency,” and hundreds of fish could be measured from one trap. According to a random tally sheet, certain fish are kept to collect “age and growth” data. Again, this could be hundreds of fish. In the ship’s “wet lab,” fish are then dissected. Most fish have a pair of “otolith” bones (i.e., ear stones) in their head. Otoliths are collected at sea, but sent to a lab where they will be examined under a microscope. When otoliths are cut by a delicate saw, visible rings tell the age of a fish, similar to how the rings visible on a tree stump can tell the age of a tree. Fish are further dissected to check the condition of their reproductive systems.
In the next blog I will I write about the “CTD” device.