NOAA Teacher at Sea Rebecca Kimport
NOAA Ship Oscar Dyson
June 30, 2010 – July 19, 2010
Mission: Summer Pollock survey
Geograpical Area:Bering Sea, Alaska
Date: June 30, 2010
Weather Data from the Bridge
Time: 1600 hrs
Latitude: 57.16 N
Longitude: 169.09 W
Cloud Cover: Dense fog
Wind: 11.56 knots
Air Temperature: 5.3°C (41.5°F)
Water Temperature: 5.09°C (41.16°F)
Barometric Pressure: 1005.02 mb
Did I mention I completed all the tasks in the previous post before lunch? That left us time to fish for pollock in the afternoon.
Why pollock? Walleye pollock (Theragra chalcogramma) is an important fish for Alaska (and the entire United States). Although you may not know it, you’ve probably eaten pollock when you have enjoyed fish sticks or a fish sandwich at a fast food restaurant. Also, sushi lovers, artificial crab is made from pollock surimi. Walleye pollock produce one of the largest catch of any single species within US waters and accounts for over half the groundfish catch in Alaska (see:http://www.afsc.noaa.gov/species/pollock.php for more information)
How the Oscar Dyson helps? By surveying the pollock populations within the Bering Sea, scientists can gather data on these important fish – including size, gender distribution, maturity, location, and diet.
How do we find the fish? Scientists work around the clock gathering data through acoustics to identify the locations of aggregations (or schools). The Oscar Dyson has five transducers located across the bottom of the ship on its centerboard. These transducers send out signals and the data are graphed on large computer screens in our acoustics lab (more information on the acoustics lab will come in a later post) While on shift, we eagerly await word that a fish aggregation has been identified and await the trawl.
And the trawl… As mentioned above, we were lucky enough to spot fish during my first shift and we conducted the trawl in the afternoon. A trawl is a method where a large net is cast off the back and towed behind the boat until it fills with fish. The take varies based on the aggregations (or schools) identified and the net may be out for two minutes or an hour. This first trawl was out for 45 minutes before the crew hauled it in. It was amazing how many seabirds were swarming around the net as it was pulled up and how many jellyfish were caught in the lines. The first task, once the catch is brought on deck and placed in the fish table, is to sort the specimens. We had pollock, Pacific cod, and 2 types of jellies (including theChrysaora melanaster shown at right)
Once the catch was sorted, the fish were weighed and then sexed. After they were sorted into Blokes and Sheilas (males and females), the fish also had to be measured. A small sample was dissected to remove stomachs and otoliths (ear bones of pollock that are used by scientists to determine the age of the fish) for further study.
Animals Seen on First Shift