My First Pollock Trawl

NOAA Teacher at Sea: Tammy Orilio

NOAA Ship Oscar Dyson

Mission: Pollock Survey

Geographical Area of Cruise: Gulf of Alaska

Date: 20 June 2011

Weather Data from the Bridge:

Latitude: 54.29 N

Longitude: -165.13 W

Wind Speed: 12.31 knots

Surface Water Temp: 5.5 degrees C

Water Depth: 140.99 m

Air Temp: 6.1 degrees C

Relative Humidity: 97%

Science & Technology Log:
We finally started fishing! The objective of this survey is to determine the population status of walleye pollock, which is an important fish species here in Alaska. Walleye pollock make up 56.3% of the groundfish catch in Alaska (http://www.afsc.noaa.gov/species/pollock.php), and chances are you've eaten it before.  It's a commonly used fish in all of the fast food restaurants, in fish sticks, and it's also used to make imitation crab meat.  

Our first catch had a little over 300 walleye pollock, and we processed all of them. Three hundred is an ideal sample size for this species. If, for example, we had caught 2,000 pollock, we would only have processed 300 of the fish, and we would have released the rest of them back into the ocean.  Check out the photos/captions below to see how we process the catch.  

Fish are first moved onto the conveyor belt, where we separate the pollock from bycatch in the net. 

After separating the pollock, the next step is to sex them.  We make a crescent-shaped slice in their ventral side to expose their gonads.  Each sex then goes into a separate container for the next step. 

After sexing, we then measured the length of each fish. There's a ruler embedded in the lab table, and we laid each fish down on the ruler. Then we put a hand-held sensor at the caudal (tail) fin of the fish, and the total length was recorded on a computer.   

At the sexing station, cutting open pollack. 

We also removed and preserved 20 stomachs from randomly selected fish in order to (later) analyze what they had been eating prior to them being caught. One of the last things we do is collect otoliths from each of those 20 fish. Otoliths are ear bones, and they are used to determine the age of a fish- they have rings, similar to what you see in trees.

Here's a look at some of the bycatch in our nets:

Basket Star.  Marine 1: What phylum are sea stars in?

Arrowtooth flounder. 

The reason(s) WHY they're called ARROWTOOTH flounder.  

Animals Spotted:

walleye pollock

chum salmon

rockfish

arrowtooth flounder

squid

basket star

Northern Fulmars

Gulls

Albatross (couldn't tell what kind)

* I did spot some kind of pinniped yesterday, but have no idea what exactly it was!

Personal Log:

I was very excited that we finally got to fish today!!  As an added bonus, we caught 2 salmon in the trawl, which means we're having salmon for dinner tonight!  We we supposed the have teriyaki steak, but the cook has changed it to teriyaki salmon instead :)  I didn't get any pics of them because my gloves were covered in fish scales, blood, and guts by that point and I didn't want to get any of that funk on my camera :)
We passed by Dutch Harbor yesterday- it should sound familiar if you watch Deadliest Catch.  We didn't go into the Harbor, so no, I didn't see any of the crab boats or any of the guys from the show!  Below are some pics of the Aleutian Islands that I've see thus far...many more to come, since we still have another 13 days (give or take) of sailing left!

QUESTION(S) OF THE DAY:

• The Aleutian Islands were formed at the boundary where the North American and Pacific Plates are coming together.  The Pacific Plate is denser than the North American Plate, so it slides underneath the North American Plate.  What is this type of plate boundary called (where plates move towards each other), and what is it called when one plate slides underneath another?  
• One thing we're doing on this trip is trawling for fish.  We are conducting both mid-water and bottom trawls.  Describe one advantage and one disadvantage to trawling in order to gather scientific data.