The Seascapes

The Seascapes

Saturday, December 10, 2011

The Net Hits the Water Under a Butterfish Moon

Last night the crew of the Karen Elizabeth was busy sampling the mid-shelf south of Martha's Vineyard. Soon after they left the dock they did a short station we call a 'shakedown' station. This allows the ship and science crew to go through the logistics of the work needed to complete a station before they get to the critical stations inside the footprint of the model. It is a great chance for everyone to see how a station will work and what adjustments should be made before the next one.

For this trip, a station is two short 20 minute trawls. One trawl will be running north/south and the second will bisect that line running east west. Once the nets are back on board, the crew will measure the total weight of butterfish (in pounds) and record the distribution of butterfish size for a random sample of 100 individual fish. Here is a picture of the large nets that are towed by the F/V Karen Elizabeth.

Here are the ship's winches that haul in the net after the trawl.

The glider strapped to the boat is calling our lab once and hour. With each call we get an updated position and an opportunity to share data from ship to shore. We are sending daily updates of the model every night to the boat and John Manderson is sending back the catch results of their sampling stations as they are completed.

Here is the position and track of the Karen Elizabeth as of 5:00am local time this morning. In all the maps we show during the trip, the location of the Karen Elizabeth will be shown as a glider's location, labeled 'ru10'.

You can see the path of the boat moving south out of Pt. Judith, RI, around the eastern side of Block Island and offshore. The three most recent red dots at the end of the track indicate where the stations were done last night. These stations were at 9:00pm, 2:00am and 5:00am local time. It was a very busy night on board.

The background color is the prediction of butterfish habitat updated for 1:00am local time. Once again the blue areas indicate habitat predicted less suitable for butterfish and the red areas are preferred habitats for butterfish. As you can see from the map, the stations last night focused on the mid-shelf in regions of relatively poor butterfish habitat. According to the model, each station is moving closer to more favorable habitat.

Today will be our first look at the mid-shelf during the day. Above is an afternoon shot from the model. You can see that the yellow areas of the 1:00am image are now orange. Since our model is an indication of when the bottom habitat is preferable to butterfish, this indicates that according to our model, the bottom is more habitable to butterfish in the afternoon than at night. The Karen Elizabeth is now heading right to the hotspot in time for a peak mid-day sample!

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