Anne Mortimer: Otoliths and more otoliths…, July 8, 2011


NOAA Teacher at Sea
Anne Mortimer
Onboard NOAA Ship Oscar Dyson
July 4 — 22, 2011 

Mission: Pollock Survey
Geographical area of cruise: Gulf of Alaska
Date: July 8, 2011

Weather Data from the Bridge
Air temperature: Sunny, 10°C
Sea temperature: 9.1°C
Wind direction: SW; 318 degrees
Wind Speed: 24.1 knots
Barometric pressure: 1012.12 mbar

Science and Technology Log

On my last 12 hour shift, a beautiful, sunny day, we started by pulling in, sorting, counting, and weighing fish caught in a mid-water trawl.  The scientists were also testing out a new “critter cam” that was attached to the net. The trawl net has a special device called a M.O.C.C. which stands for Multiple Opening and Closing Cod-ends. The net has three separate nets that can be opened and closed by the M.O.C.C. when the scientists reach the desired depth or location for catching, this keeps the catches from different targeted depths from mixing together. The three separate nets are called cod-ends. Each cod-end catch is processed separately. In this trawl, we saw multiple jellies, juvenile pollock, krill, juvenile squid, juvenile Pacific sandlance, capelin, juvenile flatfish, and juvenile cod.

capelin

Capelin from our trawl covered the deck of the boat.

MOCC entering the water

The Multiple Opening and Closing Cod-end, or MOCC, and net being released to the water for a mid-water tow.

Later, we trawled a 2nd time for about an hour. The trawl net used is called the AWT or Aleutian Wing Trawl because the sides of the net are like wings. After the net is in the water, two large steel doors are dropped in the water and help to pull the net open wide. You can see them in the picture above, they are the giant blue steel plates attached to the very stern (end) of the ship. During this trawl, only one cod-end was opened, and the catch was several hundred pounds of Pollock, with some eulachon, capelin, squid and jellies also.

Because pollock are the target fish of this survey, each was sexed and counted, and a smaller number were measured for length and weight, and the stomachs and otoliths were removed. The stomachs are being preserved for another research project back in Seattle, and as I mentioned previously about otoliths, they tell the age of the fish.

Personal Log

Today I was happy to have beautiful sunshine and 2 trawls to sort through. The skies and surrounding islands were absolutely stunning. I can understand why people are drawn to this place. It’s wild and rugged and looks like it probably did hundreds of years ago.

Scenery of the Shumigan Islands.

sunset

Dusk in the Shumigan Islands.

Species List

humpback whale (just one today!)

fulmar

tufted puffin

pollock

arrowtooth flounder

jellies

krill

squid

Pacific sandlance

capelin

juvenile flatfish

juvenile cod

sea gulls

eulachon

Thought for the day… if I was a blubbery whale, I would live in the Gulf of Alaska. If I was a pollock, I’d try not to get into a net, they can give you a splitting headache.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s