Economically, sea scallops are an important species; in 2008 the scallop harvest was about 53.5 million pounds and was worth about $370 million. The population is not currently considered to be overfished and has been above minimum sustainable levels since 2001. Formal management began in 1982 with the Atlantic Sea Scallop Fisheries Management Plan. The management plan includes limiting new permits, restrictions on gear and on the number of crew on a boat. Since about 2000, the biomass of scallops has been increasing. Biomass is estimated by using the weight of scallops per tow on cruises like this one. Combinations of biomass estimates and estimates of the commercial catch are used to update and adjust the management plan.
Sea Scallops (Placopecten magellanicus) are filter feeders. They can live up to 20 years and begin reproducing at about 2 years, with maximum fertility reached at 4 years. A single female scallop can produce up to 270 million eggs in her life. This high reproductive capacity has helped the scallop population recover relatively quickly. Gender can be determined by the color of the gonad; females are orange while the male gonad is white. Adult scallops average between 6 and 7 inches from hinge to tip (called height) but can be as big as 9 inches. Age can be estimated by counting the rings on the shell. Scallops can “swim” by opening and closing the two shells. This is a useful adaptation for escaping from predators, including flounder, cod, lobsters, crabs, and sea stars. Scallops are harvested for the adductor muscle (the one that opens and closes the shell). There is no commercial aquaculture of scallops in the US as of August 2009.
Personal Log
A storm moved through beginning on Wed. evening (day 2) and stayed with us most of Thursday. By the end of shift on Wednesday, we were working on deck in full foul weather gear and life jackets. Thursday we had an 8 hour steam between dredge sites and by the end of shift on Thursday, the seas had begun to smooth out. Friday was quite nice, weather-wise.
I am learning to shuck scallops, though I am about half the speed of many on the boat. I am also learning to tell the various types of flounder and other fish apart as well. It’s not always obvious which type of flounder or hake is which.
New Species
Goose fish (aka monk fish), several more varieties of flounder, sea urchins, sea cucumbers, eel pout, some very large skates, 3 types of sea stars and 1 type of brittle star.
NOAA Teacher at Sea
Kathryn Lanouette
Onboard NOAA Ship Oscar Dyson
July 21-August 7, 2009
Mission: Summer Pollock Survey Geographical area of cruise: Bering Sea, Alaska Date: August 1, 2009
This sonar-generated image shows walleye pollock close to the sea floor. The red line at the bottom of the image is the sea floor. The blue specks at the top of the image are jellyfish floating close to the water’s surface.
Weather Data from the Ship’s Bridge
Visibility: 10+ nautical miles
Wind direction: variable
Wind speed: less than 5 knots, light
Sea wave height: 0 feet
Air temperature: 7.9˚C
Seawater temperature: 8.6˚C
Sea level pressure: 30.1 inches Hg
Cloud cover: 7/8, stratus
Science and Technology Log
In addition to the Aleutian wing trawl (which I explained in Day 5 NOAA ship log) and Methot (which I explained in Day 8 NOAA ship log), scientists also use a net called an 83-112 for bottom trawls. The 83-112 net is strong enough to drag along the sea floor, enabling it to catch a lot of the animals that live in, on, or near the sea floor. This afternoon, we conducted the first bottom trawl of our cruise. Bottom trawls are usually conducted in two situations: if the walleye pollock are too close to the sea floor to use an Aleutian wing trawl or if the scientists want to sample a small amount of fish (because the 83-112’s net opening is smaller than the Aleutian wing trawl’s net). From the looks of the sonar-generated images, it appeared that most of the walleye pollock were swimming very close to the bottom so the scientists decided it would be best to use the 83-112 net.
Here I am holding one of the skates that was caught in the bottom trawl
Once the fish were spotted, we changed our course to get ready to trawl. Usually the trawl is made into the wind for stability and net control. Once the ship reached trawling speed, the lead fisherman was given the “OK” to shoot the doors. Slowly, the net was lowered to 186 meters below the surface, the sea depth where we happened to be. The water temperature down there was about 1˚C (compared to 7˚C on the sea’s surface). I had heard from a previous Teacher At Sea that bottom trawls brought up a wide variety of animal species (compared to the relatively homogenous catches in mid-water trawls). And sure enough, when the net was brought up, I couldn’t believe my eyes!
All told, we sorted through over 7,000 animals, a total of 36 different species represented in the total catch. It took 4 of us over 4 hours to sort, measure, and weigh all these animals. There were over 350 walleye pollock in this catch as well as skates, octopi, crabs, snails, arrowtooth flounder, sea anemones, star fish, and dozens of other animals. Some of them were even walking themselves down the table.
During this catch, I also learned how to take the ear bones, or otoliths, out of a walleye pollock. Why ear bones you might ask? Using the ear bones from a walleye pollock, scientists are able to determine the exact age of the fish. Misha Stepanenko, one of the two Russian scientists on board the Oscar Dyson, showed me how to cut partially through the fish’s skull and take out two large ear bones. Once they were taken out, I put them in a solution to preserve them. Back in NOAA’s Seattle lab, the ear bones are stained, enabling scientists to count the different layers in each ear bone. For every year that the fish lives, a new layer of bone grows, similar to how trees add a layer for each year that they live. By learning the exact age of a fish, scientists are able to track age groups (called “cohorts”), allowing more precise modeling of the walleye pollock population life cycle.
A diagram of an otolith, or ear bone, of a fish. You can see that it’s a lot like looking at tree rings!
Personal Log
So far this trip, we have sailed within 15 miles of Cape Navarin (Russia) on at least two different occasions but fog and clouds prevented any glimpse of land both times. It was a frustrating feeling knowing that land was so close, yet impossible to see. After 12 days of looking at nothing but water and sky, seeing land would have been a welcome treat.
Despite not seeing land, I still felt like I was in Russia just from listening to different fishing vessels communicate with one another. On our first night in Russian waters, we sailed through a heavy fog, with 7 or 8 different boats fishing nearby. I was impressed with how Ensign Faith Opatrny, the Officer on Deck at the time, communicated with various vessels, using collision regulations (“the rules of the road”) to navigate safely. On a culinary note, I got my first chance to eat some of a catch. After most trawls, we discard remaining inedible specimens overboard. After our bottom trawl however, one of the scientists filleted some of the cod. The next day, the stewards cooked it up for lunch. It tasted great and it felt good to be eating some of the fish that we sampled.
A graph showing the adult walleye pollock biomass estimates from 1965 to 2008.
As the cruise starts to wind down, I also want to express my gratitude to all the NOAA scientists and Oscar Dyson crew. Everyone in the science group took time to explain their research, teach me scientific techniques, and answer my many questions. On numerous occasions, the deck crew explained the mechanics of fishing nets as well as the fishing process. The engineering crew gave me a tour of the engine rooms, describing how four diesel engines power the entire boat. The survey techs explained how different equipment is operated as well as the information it relays back to the scientists. The NOAA Corps officers showed me how to read weather maps, take coordinates, and explained ship navigation. The ship’s stewards described the art and science behind feeding 33 people at sea. And the USFWS bird observers patiently showed me how to identify numerous bird species. From each of them, I learned a tremendous amount about fisheries science, fishing, boats, sailing, birding, and life in the Bering Sea. Thank you!
Answer to July 28 (Tuesday) Log: How has the walleye pollock biomass changed over time?
In the past few years, the walleye pollock biomass has decreased (according to the acoustic-trawl survey, the survey that I joined.) It should be noted that there is a second complementary walleye pollock survey, the eastern Bering Sea bottom trawl survey. This survey studies walleye pollock living close to the sea floor. As walleye pollock age, they tend to live closer to the sea floor, thus the bottom trawl survey sometimes shows different biomass trends than the acoustic-trawl survey. Both surveys are used together to manage the walleye pollock stock.
An up-close look at one of the squid’s tentacles
Animals Seen
Auklet, Arrowtooth flounder, Basket star, Bering skate, Cod, Hermit crab, Fin whale, Fur seal, Octopus, Sculpin, Sea mouse, Sea slug, Shortfin eelpout, Snow crab, Squid, and Tanner crab.
New Vocabulary: Bottom trawl – fishing conducted on and near the bottom of the sea floor. Catch – fish brought up in a net. Shoot the doors – a fishing expression that means to lower the 2 metal panels that hold open the fishing nets in the water. Stewards – the name for cooks on a ship. Table – nickname for the conveyor belt where the fish are sorted for sampling. Vessels – another word for ships.
NOAA Teacher at Sea
Duane Sanders
Onboard Research Vessel Hugh R. Sharp
June 8-19, 2009
Mission: Sea Scallop Survey Geographical Area: New England Coast Date: June 15, 2009
Weather Data from the Bridge
Wind: Speed 6.8 KTS, Direction 65.7 degrees
Barometer: 018 millibars
Air temperature: 11.33 0C
Seas: 2-3 ft.
Dumping a dredge on the sorting table.
Science and Technology Log
We had to change out the dredge during my last watch. Actually, I watched while the crew did the dangerous work. We have been working in an area with a rocky bottom and the rocks caused substantial damage to the netting in the dredge. Fortunately, we are carrying four dredges plus spare netting. The crew put a new dredge into operation right away so that we didn’t lose too much time. Geoff, our watch chief, directed the installation of the new mesh into the first dredge.
The scallop dredges we use are eight feet wide. Commercial dredges are sixteen feet wide. The basic design is the same for each. The mouth of the dredge is a welded steel rectangular frame, with the height about one foot. The bottom of this rectangle is a heavy steel bar, called the cutting bar. This breaks loose organisms from the bottom. A steel plate, called the pressure plate, is welded at an angle across the top of the rectangle. This plate creates a downward swirl of water that directs the organisms into the mouth of the netting. The bag attached to the dredge is made of a net of steel rings. A mesh liner is mounted inside the bag for scientific use. This helps to trap other organisms that make up bottom-dwelling communities. This gives scientists a more complete picture for the survey. Commercial dredges do not use a liner and the rings of the bag are larger. This allows smaller size scallops and other organisms to pass through the bag and remain to help sustain a healthy scallop population.
The business end of a scallop dredge
We have been ‘shadowed’ by another ship, the Kathy Marie for part of the time we have been working. She is carrying a device known as the “HabCam”, short for Habitat Camera. This is an underwater camera system that is towed just over the bottom. It makes a photographic record of still images of the bottom taken at a rate of three per second. The HabCam accumulates data at about three terabytes per day. The Kathy Marie runs over the same area dredged by the Sharp after we move on to the next station. Images from these runs provide scientists with an index of dredge efficiency at capturing the bottom dwellers. Once enough image data has been collected to make useful correlations to dredge data, it might be possible to reduce the number of physical dredge samples taken and use the HabCam to record the community ‘in situ’, that is, in position without disturbance.
Personal Log
I said in an earlier log entry that fish are not my favorite type of organism. Because of this bias, I had been avoiding helping with the fish sorting and identification. After thinking about this for a bit, I decided that I needed to embrace my bias against fish and try to learn something as well as help my colleagues. Besides, how could I face my students without at least making an effort? So, I am trying to learn how to identify these critters. So far, I am pretty good with goosefish, red hake, longhorn sculpin and some of the flounder species.
I wonder how long it will take me to adjust to walking on dry land after being at sea for eleven days. I guess I’ll find out soon enough. I have been trying to read some before going to sleep, but I find that I can do a few pages at best. Hard work, sea air and the rocking motion of our ship make powerful sleep inducers.
NOAA Teacher at Sea
Elise Olivieri
Onboard Research Vessel Hugh R. Sharp May 9 – 20, 2009
Mission: Sea Scallop Survey Geographical area of cruise: Northwest Atlantic Date: May 17, 2009
Weather Data from the Bridge
Air Temperature: 13.61 Degrees Celsius
Barometric Pressure: 1012 mb
Humidity: 97 %
Here you can see the many different sizes of sea scallops.
Science and Technology Log
So Far the sea scallop survey has collected 76,170 sea scallops which can also be expressed as 9,251 kilograms. This is a tremendous amount of scallops and the survey is not even a third of the way complete. At stations where crabs and starfish were sampled we have collected 8,678 cancer crabs and 279,768 starfish (Asterias) so far. Without a reliable database like FSCS it would be impossible to keep up with such a large amount of information.
Today I got a chance to talk with Shad Mahlum. He is a seagoing technician for NOAA and was born and raised in Montana. He has experience working with freshwater surveys. In the past years he has studied how beaver dams influence native and non-native species of freshwater fish. Shad also spent some time looking at various cattle grazing strategies and how they affect food chains. Shad loves working on the open ocean and the physical process of sea scallop surveys. Shad hopes to work with freshwater and saltwater projects in the future.
Here I am holding a scallop and a Red Hake.
As I was gazing out into the deep blue sea a very large animal caught my eye. I was so excited to see another Finback Whale. They are the second largest animal on earth after the Blue Whale. They are known to grow to more than 85 feet. Finbacks are indifferent to boats. They neither approach them nor avoid them. Finback Whales dive to depths of at least 755 feet. They can grow anywhere from 30-80 tons. Finbacks eat Krill, fish and squid and their population numbers are approximately 100,000 or more. The only threats Finbacks have are polluted waters. It is incredible to see such a large animal breaching out of the water. I will never forget it.
Animals Seen Today
Wrymouth Squid, Eelgrass Slug, Razor Clam, Lobsters, Green Sea Urchin, Macoma clam, Sea Stars (Asterias), Horseshoe Crab, Fourbeard Rockling, Palmate Sponge, Hermit Crab, Black Clam, Golden Star, Tunicate, Winter Flounder, Surf Clam, Yellowtail Flounder, and Sea Mouse.
NOAA Teacher at Sea
Susie Hill
Onboard NOAA Ship Albatross IV July 23 – August 3, 2007
Mission: Sea Scallop Survey Geographical Area: North Atlantic Ocean Date: July 30, 2007
Mesh netting in the dredge
Weather Data from the Bridge
Air Temperature: 17.5° C
Sea Temperature: 18.6° C
Relative Humidity: 100 %
Barometric Pressure: 1014.8 millibars
Wind Speed: 3.62 knots
Water Depth: 65.3 meters
Conductivity: 43.45 mmhos
Salinity: 32.03 ppt
Science and Technology Log
I can’t believe it’s already been a week already since we left from Woods Hole, MA. I’m still getting a hang of the time schedule, but it’s working out okay. The weather has been beautiful. The staff is great—I’ve learned so much from them. The food is delicious, too! Today’s focus will be on the dredge. This is a metal frame with a metal ringed and meshed net that we use to dredge or scoop the sea bottom in hopes of finding our prize catch, sea scallops. The bag is about 8 feet wide with 2” rings and mesh netting. The mesh netting, called a liner, is in the dredge to ensure catching of the smaller scallops as well as the other species that coexist with the scallops. The dredge is lifted, put into the water, and dragged using a motorized gantry with a block and tackle system. The dredge is towed for 15 minutes at each station. The depths for this trip have been ranging from 29 meters to 112 meters. Sea Scallop dredge surveys have been conducted by the National Marine Fisheries Services since 1975.
Sea Scallops (Placopecten magellanicus) are filter feeders. They can live up to 20 years and begin reproducing at about 2 years, with maximum fertility reached at 4 years. A single female scallop can produce up to 270 million eggs in her life. This high reproductive capacity has helped the scallop population recover relatively quickly. Gender can be determined by the color of the gonad; females are orange while the male gonad is white. Adult scallops average between 6 and 7 inches from hinge to tip (called height) but can be as big as 9 inches. Age can be estimated by counting the rings on the shell. Scallops can “swim” by opening and closing the two shells. This is a useful adaptation for escaping from predators, including flounder, cod, lobsters, crabs, and sea stars. Scallops are harvested for the adductor muscle (the one that opens and closes the shell). There is no commercial aquaculture of scallops in the US as of August 2009.
