Tom Savage: Tuning in to Sei Whales, June 16, 2015

NOAA Teacher at Sea
Tom Savage
On Board NOAA Ship Henry B. Bigelow
June 10 – 19, 2015

Tuning in to Sei Whales

Mission: Cetacean and Turtle Research
Geographic area of Cruise: North Atlantic
Date: June 16, 2015

Weather Data from the Bridge
Air temperature: 13 C
Wind speed: 10 knots
Wind direction: coming from the North West
Relative humidity: 95%
Barometer: 1004 millibars

Personal Log

Today is my third day at sea and I’m enjoying every moment; time onboard the ship flies. Although time onboard is dwindling, lots of discovery remains. Sunday brought sunny skies and warm temperatures, another perfect day for whale identification. It has been a real joy working with this exceptional group of professionals. Everyone is very supportive of each other and mission focused.

Science and Technology Log

The mission of this cruise is Cetacean research, but what exactly is a Cetacean? Cetus is a Latin word used in the context of biology defined as “whale”. Whales and dolphins are included within this order of classification. As stated in my earlier blogs, we are focusing on sei whales, pronounced ‘say” and beaked whales.

Why study sei and beaked whales? These whales are some of the least studied and scientists know relatively little about them. Information collected so far on sei whales: they have poleward migration trends, feed on small fish, krill and copepods (small crustaceans), and are thought to be populated along boundaries of elevated sea floors such as Georges Bank. Along the border of Georges Bank, upwelling of small prey occur due to ocean currents creating a perfect feeding ground for whales. Sei whales will also skim the ocean surface for food. Unfortunately, due to this feeding habit, many sei whales are struck and killed by large ships.

The other type of whale we are searching for are beaked whales. These whales are extremely difficult to identify due to their feeding and swimming behaviors. They are deep divers and spend a lot of time at depths of more than a thousand feet feeding on squid and fish. When they surface, they are inconspicuous and not acrobatic, and they are very difficult to see. Because they are found offshore in very deep waters, there are few opportunities to study them. Most of what is known about these species comes from individuals that have stranded on beaches where people can find them.

Spectrogram
Acoustician scientist, Chris, analyzing a spectrogram

One method scientists on board use to detect the presence of sei whales is to listen for them using hydrophones (underwater microphones). For this cruise, the acousticians are deploying sonobuoys: short term recorders that can transmit live audio feed through VHF channels. Sei whales generate tonal calls and produce a “down sweep “ from high to low frequency with a range from of 80 – 30 Hz. Sei whales are classified as a Baleen Whale.

Sei whale
Sei whale, photo courtesy Northeast Marine Fisheries, NOAA Whale permit mmpa # 17355

Baleen whales produce tonal calls typically under 1 kHz. For some species, like the humpback whale, song is known to be produced only by males, presumably to attract mates. After deploying the sonobuoy, we quickly began receiving signature tonal calls of sei whales. A sound spectrogram is used to interpret and project these acoustics on a graph with frequency on the y axis (vertical) and time on the x axis (horizontal). The darker plots indicate that the whale is close and lighter plots are weaker signals. Sometimes they will call in doubles or triple sweeps. Below is an example of a sei whale tonal call of the coast of Nova Scotia. Can you find the call?

Spectrograph
Sei whale acoustic sample recorded off the coast of Nova Scotia.

Scientists are not sure at this point what purpose these calls serve; for example, they could be used to maintain contact between individuals, attract mates, or advertise feeding areas.

Atlantic White Sided Dolphin
Atlantic White Sided Dolphin Photo taken by Hillary Moors-Murphy

Scientists are also trying to understand the oceanographic and habitat factors that are correlated with sei whale distribution. One question is what kind of prey are in the areas where sei whales are and are not found. In the evening hours, fishing nets are deployed to take a sample of organisms present in the ocean at that location. Shallow nets, called bongos, are used to take samples of zooplankton in the water down to 200m. Tonight, we are in deeper waters and the mid-water trawl net went down to 650 meters for 45 minutes. The net is then pulled in and fish are identified, counted and entered into a computer database. As mentioned above, sei whales like to feed on copepods and small arthropods. Guess what we pulled out of the bongo nets last night?

Copepod Soup
Copepod soup. A delicious dinner for sei whales!

Until next time, happy sailing!

Tom

Kathryn Lanouette, July 28, 2009

NOAA Teacher at Sea
Kathryn Lanouette
Onboard NOAA Ship Oscar Dyson
July 21-August 7, 2009 

Here I am sorting different zooplankton species
Here I am sorting different zooplankton species

Mission: Summer Pollock Survey
Geographical area of cruise: Bering Sea, Alaska
Date: July 28, 2009

Weather Data from the Ship’s Bridge 
Visibility: 8 nautical miles
Wind direction:  015 degrees (N, NE)
Wind speed:  7 knots
Sea wave height: 1 foot
Air temperature: 7.6˚C
Seawater temperature: 7.3˚C
Sea level pressure: 29.8 inches Hg and falling
Cloud cover: 8/8, stratus

Science and Technology Log 

In addition to studying walleye pollock, NOAA scientists are also interested in learning about the really tiny plants (phytoplankton) and animals (zooplankton) that live in the Bering Sea.  Plankton is of interest for a two reasons. First, phytoplankton are the backbone of the entire marine food chain. Almost all life in the ocean is directly or indirectly dependent on it. By converting the sun’s energy into food, phytoplankton are the building blocks of the entire marine food web, becoming the food for zooplankton which in turn feed bigger animals like small fish, crustaceans, and marine mammals. Second, zooplankton and small fish are the primary food source for walleye pollock. By collecting, measuring, and weighing these tiny animals, scientists are able to learn more about the food available to walleye pollock. In addition, every time the scientists trawl for walleye pollock, the stomachs of 20 fish are cut out and preserved. Back at a NOAA lab in Seattle, the contents of these fish stomachs will be analyzed, giving scientists a direct connection between walleye pollocks’ diet and specific zooplankton populations found throughout the Bering Sea.

A simplified marine food chain  (Note: A complete marine food web involves hundreds of different species.)
A simplified marine food chain (Note: A complete marine food web involves hundreds of different species.)

Two important zooplankton groups in the Bering Sea are copepods and euphausiids (commonly referred to as krill). Euphausiids are larger and form thick layers in the water column. In order to catch euphausiids and other zooplankton of a similar size, a special net called a Methot is lowered into the water. This fine meshed net is capable of catching animals as small as 1 millimeter. The same sonar generated images that show walleye pollock swimming below the water’s surface are also capable of showing layers of zooplankton. Using these images, the scientists and fishermen work together, lowering the net into the zooplankton layers.

The Methot net is the square shaped net in the background. It was just brought up and is filled with hundreds of zooplankton.
The Methot net is the square shaped net in the background. It was just brought up and is filled with hundreds of zooplankton.

Once the Methot net is back onboard the boat, its contents are poured through fine sieves and rinsed. All species are identified. A smaller sub sample is weighed and counted. This information is applied to the entire catch so if there were 80 krill, 15 jellyfish, and 5 larval fish in a sub sample, then scientists would approximate that 80% of the entire catch was krill, 15% was jellyfish, and 5% was larval fish. Having only seen photos of some of these zooplanktons, it was interesting to hold them in my hands and look at them up close. They seemed better suited for space travel or a science fiction movie than the Bering Sea!

Personal Log 

The day before, I caught my first glimpse of Dall’s porpoises. This pod of porpoises came swimming alongside the boat. It was awesome to see their bodies rise and fall in the water. I was surprised at how quickly they were swimming, darting in and out of the Oscar Dyson’s wake. Today, I also got my first glimpse of a whale! It was a fin whale, a type of baleen whale, about 20 meters from the boat. It was exciting to watch such a large mammal swimming in such a vast expanse of water. I’m hoping to see a few more marine mammal species before we return to port. The seas have been very calm for the last five days, at times as smooth as a mirror. I’m surprised that I’ve gotten used to falling asleep in the early morning hours and waking around midday. Now that I’ve adjusted to the 4pm to 4am shift, I’m wondering how strange it will be to return to my regular schedule back on the east coast.

Answer to July 25th Question of the Day: Why are only some jellyfish species capable of stinging? 
As I picked up my first jellyfish in the wet lab (asking at least twice “Are you sure this won’t sting?”), I wondered why some jellyfish don’t sting.  So I did some reading and asked some of the scientists a few questions. Here is what I found out: All jellyfish (called “gelatinous animals” in the scientific world) have stinging cells (nematocysts) in their bodies. When a nematocyst is touched, a tiny barb inside fires out, injecting toxin into its prey.  It seems that in some jellyfish, the barbs are either too small to pierce human skin or that nematocysts don’t fire when in contact with human skin.

One euphausiid and two different species of hyperiid amphipod (They are between 1-3 cm long)
One euphausiid and two different species of hyperiid amphipod

Animals Seen 
Capelin, Dall’s porpoise, Euphausiid, Fin whale, Hyperiid amphipod, and Slaty-backed gull.

New Vocabulary: Baleen whale – a whale that has plates of baleen in the mouth for straining plankton from the water (includes rorqual, humpback, right, and gray whales). Methot net – a square framed, small meshed net used to sample larval fish and zooplankton. Phytoplankton – plankton consisting of microscopic plants. Plankton – small and microscopic plants and animals drifting or floating in the sea or fresh water. Trawl – to fish by dragging a net behind a boat. Zooplankton – plankton consisting of small animals and the immature stages of larger animals

Question of the Day: How has the walleye pollock biomass changed over time?