hydroacoustics – Page 3 – NOAA Teacher at Sea Blog

NOAA Teacher at Sea
Marilyn Frydrych
Onboard NOAA Ship Delaware II
September 15-25, 2008

Mission: Atlantic Herring Hydroacoustic Survey
Geographical area of cruise: New England Coastal Waters
Date: September 18, 2008

Weather Data from the Bridge
41.27 degrees N, 70.19 degrees W
Partly Cloudy
Wind out of the W at 19 knots
Dry Bulb Temperature: 26.0 degrees Celsius
Wet Bulb Temperature: 20.9 degrees Celsius
Waves: 9 feet
Visibility: 10 miles
Sea Surface Temperature: 21.6 degrees Celsius

Science and Technology Log

We suspended operations. The seas were from 8 to 9 feet for the next day and a half. Conditions were unsafe for the fishermen to work. Everyone spent the day reading, playing board games, watching movies, or typing on the three computers provided for everyone’s use. Erin Earley, the engineer wiper, took the opportunity to show Jacquie and me the engine room. She took us through all the portals marked, “Do Not Enter”. They all had ladders under them leading to the bowels of the ship. The engine area was compartmentalized and was entered from different spots from above. Erin showed us the ubiquitous colored handles which turned the various valves on and off.

There were yellow handles for transmission oil pipes, green for seawater, orange for hydraulic fluid, red for emergency fire hose water, blue for drinking water, and brown for engine oil. We headed down under the galley where we passed next to the 12-cylinder Detroit Diesel engine which powered the screw. It was about ten times the size of a good-sized pickup engine. Erin explained the importance of placing all this heavy machinery so that the weight is evenly distributed within the ship. The engine being so heavy is usually near the center of the ship. This necessitates a huge long drive shaft connecting it to the screw. The drive shaft, spinning away at high speed, was out in the open just under and alongside the catwalk. One slip would be catastrophic. Most of what we saw was large 5’ by 5’ or larger rectangular tanks for fuel, distilled water, black water, gray water, and used oil. The black water from the toilets is stored in a tank with “bugs” or a bacteria in it which eat the refuse and in effect clean up the water. The gray water is from the sinks and showers and contains soap which kills the bugs. The gray water has to be saved in tanks separate from the black water. All this is dumped into the sea in designated areas. Only the used oil is saved to be offloaded back at the dock.

Erin Earley pointing out hydraulic fluid pipes.

We saw two workshop areas, a storeroom with all the parts that might be needed for any possible repair, an extra emergency generator, and the Engine Control Room (CERC), where Engineer Chris O’Keefe was standing watch. The CERC room contained all the gauges to monitor all the engine systems. By the end of the tour Jacquie and I were totally impressed with how clean and organized everything was and how much knowledge the engineers needed. The four of them had to be experts in heating and cooling, in welding, in diesel engine repair, in electrical repairs, and hydraulics. Each of them had either mastered these fields or was in an apprenticeship with that as their goal. Usually people master one of these fields in a lifetime. We were also impressed with how many safety features were built in everywhere. It seemed everywhere we went there were three foot CO2 bottles which would automatically spray everywhere if a fire were to occur.

Personal Log

Sleeping was difficult for me that evening. I did succumb to seasickness Friday morning, but was fine after downing a sea sickness pill. We frittered away the rest of the day. Robert Gamble, second scientist under Mike Jech, got out his game called Hive and taught three or four of us how to play. Otherwise I read, did Sudoku, rode the exercise bike, and ate.

The food was tremendously good. All of it was prepared from scratch. The two cooks were at least four star cooks. They not only cooked, they also cleaned up their own mess, did the dishes, and cleaned up the dining area. They appeared the hardest workers on board. For both lunch and dinner they prepared two entrees, three veggies, homemade soup, and two salads. They baked two luscious desserts as well. So far we have sampled lamb chops, salmon, lobster bisque, crab ravioli, pork chops with a luscious applesauce, and grilled swordfish.

NOAA Teacher at Sea
Marilyn Frydrych
Onboard NOAA Ship Delaware II
September 15-25, 2008

Mission: Atlantic Herring Hydroacoustic Survey
Geographical area of cruise: New England Coastal Waters

Date: September 17, 2008

Weather Data from the Bridge
41.27 degrees N, 70.19 degrees W
Partly Cloudy
Wind out of the W at 19 knots
Dry Bulb Temperature: 26.0 degrees Celsius
Wet Bulb Temperature: 20.9 degrees Celsius
Waves: 2 feet
Visibility: 10 miles
Sea Surface Temperature: 21.6 degrees Celsius

Science and Technology Log

The third day out was much like the second day. Our first job was to fish with the big net. This time the chief scientist wanted to know what some small vertical echoes on the echogram were. He guessed that they were shrimp or krill. The acoustic echogram used three frequencies: 18 kHz, 38 kHz, and 120 kHz. If dots appeared in all three then he was pretty sure it was fish and most likely herring. These particular vertical dots appeared only in the 18 kHz echogram. He guessed they were very small fish, but wanted to determine if the signature belonged to opening were huge metal doors. They looked like doors, but in fact never closed. They were actually more like the front edge of an airplane wing. Their purpose was to stay parallel to each other and keep the net open. The net was rolled up on a large roller, which sat at the center back of the fantail. It was about 250 ft long. When it was time to deploy, the fishermen used a winch to unwind the net. The person at the helm had to be extremely careful that the boat kept at a steady headway of about 3 to 4 knots. The doors were stored at the very end of the stern. With the help of their own hydraulic winches they were lifted to a spot where they could be attached to the net. There was a place on each side of the net where the side wire changed to a chain link. The metal doors were clasped on these links and then dragged into the sea. Another link in the wire was for heavy chains. Their weight of about 400 pounds each held the sides of the net down.

Fishermen setting up the recorder which is sent outwith the net. — Fishermen setting up the recorder sent outwith the net.

The night crew, on from 6:00 pm to 6:00 am were busy Wednesday night and on into the morning. They did two CTD’s and three net deployments. They left us about 50 herring and silver hake to observe in the morning. Richie Logan, one of the fishermen, used these to write a birthday note to his daughter. Here’s his picture. Each time we sent out a net we were hoping for about half a clothes basketful of fish. Last night they filled 30 baskets. Only about 1/3 of a basket is ever measured and weighed. The rest are tossed back. Our chief scientist said he can remember processing enough to fill 60 baskets. So far most of the biomass in the basket has been krill. Mixed in with the krill are small anthropoids maybe a half inch square, jelly fish about twice that size, Illex squid from 2 to 6 inches long, baby silver hake, butterfish, or red hake. These last three are all in the neighborhood of 1 inch long.

This morning we pulled up a lamprey eel about 2 feet long and a couple two inch lumpfish in the evening. Most of the fish were dead when we got to them. We had to wait until the fishermen were totally finished with winding the net and had dumped the net’s contents onto the deck before we were allowed on the fantail. Then we sorted the large fish into clothes baskets and the smaller ones into small trays. Wednesday Jacquie Ostrom, another volunteer from Colorado Springs, noticed that two 3-inch lumpfish were moving. She added some water to our rectangular sorting pan and a piece of clear hard plastic we had thought was some molt or litter also started to move. No one seemed to know what the “plastic” was. After a quick reference to the Internet we learned it was the larva of the spiny lobster.

Richie Logan making a Happy Birthday email for his daughter.

Personal Log

We must have passed by the north-south migration path of the whales. We didn’t spot any today. The work load is really light compared with teaching. We work two or three hours cataloguing the catch after each trawl, clean up with the saltwater deck hose, and then wait for the next trawl maybe three or four hours later. A 20 minute CTD deployment every now and then is the only other work we are expected to do. The cruise is turning out to be very relaxing. I spend quite a bit of time just staring out at the sea, immersing myself in its gentle rhythm.

Seven basketsful of herring from a haul in the deep waters near Georges Bank.

The piece of “plastic” turned out to be the larva of a spiny lobster.

Tag: hydroacoustics

Marilyn Frydrych, September 18, 2008

Marilyn Frydrych, September 17, 2008