Marilyn Frydrych, September 20, 2008

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 20, 2008

Weather Data from the Bridge 
42.53 degrees N, 67.51 degrees W
Cloudy, wind out of the E at 11 knots
Dry Bulb Temperature: 15.2 degrees Celsius
Wet Bulb Temperature:  14.0 degrees Celsius
Waves: 1 foot
Visibility:  10 miles
Sea Surface Temperature:  16.9 degrees Celsius

A goosefish, also called a lumpfish.
A goosefish, also called a lumpfish.

Science and Technology Log 

We did a CTD with an attached water bottle and then deployed a net. We backtracked today and redid the sites we found yesterday which had good herring potential. About 10:30 in the morning we collected about 1/3 of a clothesbasket of fish. Most of that were herring and mackerel, with the usual small butterfish, goosefish or lumpfish, red hake fish, small jellyfish, and Ilex squid. The catch included an unknown two inch fish which Mike, the chief scientist, conjectured had gotten caught in a warm eddy off the Gulf Stream and ended in the wrong part of the ocean much like the jet stream blows birds off course. Part of sorting the fish involved gutting one to three each of the different lengths of herring to determine their sex, age, and what they had been eating. With practice and much patience on Robert and Jacquie’s part I learned to recognize the stomach and sex organs of the fish.  None of the herring today had anything in their stomachs, while those of two days ago had lots, mostly krill.  With two of us working it took about 45 minutes to measure the length and weight of each herring.  They varied When we finally collected the net we had 3 basketsful of redfish, half a basket of silver hake, 4 herring, one large goosefish about a foot long, and a rare Atlantic Shad about 2 feet long.

To measure our fish we used the magnetized pointer in the upper right hand corner of the picture.  It looks like a cigarette.  We lined up the fish’s head against the black backstop. Then we stretched the body straight out.  When we pressed the pointer against the end of the fish’s body an electrical circuit closed and the computer automatically recorded the fish’s length.  The fish are silver hake.
To measure our fish we used the magnetized pointer. We lined up the fish’s head against the black backstop and stretched the body straight out. When we pressed the pointer against the end of the fish’s body an electrical circuit closed and the computer automatically recorded the fish’s length. The fish are silver hake.

We froze samples which we’d opened up for Mike and then one ungutted sample from each of the nine categories for the University of  Maine. We did another CTD about 11:30 and deployed the net again. All did not go well this time. The sonar showed that the net was twisted and the opening blocked. The fishermen were called upon to bring it in and straighten it.  The first thing they did was to take the two 400 pound chain weights off. Then they sent the net back out hoping it would straighten itself.  Alas, they had to bring it in and send it out a couple more times as they manually untangled all the lines. It was very strenuous work and took them about 45 minutes.  As a result we steamed about 3 miles past the point where we intended to fish.

We’ve sorted a smaller catch on the measuring board. We measured and weighed these fish, but never opened them to determine their sex.  We did that only for herring.  The scale is under the gray container on the right.  We only had to press a button for the computer to record the weight.
We’ve sorted a smaller catch on the measuring board. We measured and weighed these fish, but never opened them to determine their sex. We did that only for herring. The scale is under the gray container on the right. We only had to press a button for the computer to record the weight
 

Tara Treichel, April 25, 2008

NOAA Teacher at Sea
Tara Treichel
Onboard NOAA Ship Nancy Foster
April 15-27, 2008

Mission: Lionfish Survey
Geographical Area: Atlantic Ocean, off the coast of North Carolina
Date: April 25, 2008

The diver support boat NF-4 waits for the dive team to surface.
The diver support boat NF-4 waits for the dive team to surface.

Weather Data from the Bridge 
Visibility: 10 n.m.
Wind: 2 knots
Waves: 1 foot
Ocean swells: 2-3 feet
Sea surface temperature: 23.4
Air temperature: 21.5

Science and Technology Log 

Today the morning dive at Lobster Rocks went to 125 feet. The report was that it was an excellent dive, and the video showed this to be true. The visibility was excellent and the habitat looked rich. Among the Amberjacks, Grouper, Blue Angelfish, and Hogfish, were tons of Lionfish! They were everywhere, lurking around every ledge and rock. They look like princes of their domain, regal in their showy capes of red and white, brandishing lances to keep out intruders. Neither aggressive nor fearful, as they have few if any predators, they hover in place, guarding their territory from other lionfish.

NOAA Teacher at Sea, Tara Treichel, has just taken length and fin ray measurements from this large lionfish, and has removed gonads and a gill sample for lab analysis.
NOAA Teacher at Sea, Tara Treichel, has just taken length and fin ray measurements from this large lionfish, and has removed gonads and a gill sample for lab analysis.

The morning divers brought a small collection of creatures back for further study, including a sample of bryozoans (a form of attached invertebrates that looks a lot like algae), a large spiny lobster (carapace at least 5 inches in diameter), a handful of fish for the cryptic fish survey, and about a dozen Lionfish. I helped Wilson take basic measurements from the Lionfish, and dissected them to remove gonads and gill samples for DNA analysis. The fish ranged in size from 150 to 380 mm, from mouth to end of tail. Next, dorsal and anal fin rays are counted, to help determine species classification (lionfish are of Indo-Pacific origin, and are classed in two subspecies based on number of fin rays). On the fish sampled, dorsal fin rays varied between 10 and 11.5, but anal fin rays consistently numbered 7.5. After I had removed the gill section and gonads, I gave the fish to Brian, who opened up their stomachs to take a cursory look at what the fish had been eating. In one, he found a small spiral shell about the size of a shirt button. In another, the stomach was bulging full, and contained four small fish, whole but partially digested and terribly stinky. All in a day’s work of a scientist! After this initial information was collected, the fish were labeled in zip-lock bags and frozen for later study. 

The stomach of this small Lionfish contained four partially digested whole fish.
The stomach of this small Lionfish contained four partially digested whole fish.

Personal log 

Today I had the fortune—and the misfortune—of getting out in one of the small boats. I say fortune because the conditions were ideal: calm seas and sunny blue skies. It was a great day to be out on the water, and I expressed an interest in going for a swim. We were responsible for shuttling the safety diver to assist the dive team, and transporting the dive team back to the NANCY FOSTER. The misfortune occurred toward the end of the dive, as the safety diver was trying to reboard the boat. To make it easier for him to enter the boat, the skipper removed the side door of the craft, a routine task. Under normal circumstances, the bilge pumps purge any water that splashes into the boat, but on this day, for reasons unknown the bilge was already full of water, and the water that surged into the open door space quickly filled the stern of the boat. We tried to replace the door, but the water was spilling in too quickly, and the boat slowly overturned. So, I got my wish to swim faster than I’d expected! Fortunately, as I mentioned, it was a fine day for a swim. Minutes later, two rescue boats were deployed from the NANCY FOSTER, and shortly after we picked up the dive team and were safely onboard the mother ship again. The ship had quite a challenge getting the overturned boat back onboard and into its cradle, but with skilled use of the crane, the boat was recovered in little over an hour. It was the sort of adventure I had least expected when going out to sea. I was happy that no one got hurt, and impressed with the response of the NANCY FOSTER crew. 

Roy Arezzo, July 23, 2007

NOAA Teacher at Sea
Roy Arezzo
Onboard NOAA Ship Oscar Dyson
July 11 – 29, 2007

Mission: Summer Pollock Survey
Geographical Area: North Pacific, Alaska
Date: July 23, 2007

Weather Data from Bridge 
Visibility: <1 nm (nautical miles)
Wind direction:   220° (SW)
Wind speed:   8 knots
Sea wave height: <1 foot
Swell wave height: 0 feet
Seawater temperature: 9.8 °C
Sea level pressure: 1006.7 mb (millibars)
Air Temperature: 10°C
Cloud cover: 8/8, fog

Roy and Tamara get excited about birding on the bridge of the OSCAR DYSON
Roy and Tamara get excited about birding on the bridge of the OSCAR DYSON

Science and Technology Log 

Consumers became very aware of the issue of by-catch when the media reported the canned-tuna industry was killing dolphins in their nets nearly a decade ago. The industry responded by changing some of their fishing methods and marketing “dolphin-safe tuna”. NOAA monitors and sets catch limits for commercial fishing, regulating by-catch, among other things. The Coast Guard assists by also enforcing these fishing regulations. Some of the scientists working here on the pollock survey have worked as fishery observers on commercial vessels, monitoring by-catch in the Alaska fleets. The by-catch regulations vary based on the region, species and season. For example, on the Bering Sea none of the finfish outfits are allowed to keep any crab, they need a special permit to keep halibut and they need to keep cod if they are fishing for pollock. Commercial trawling for pollock results in typically low by-catch. Some environmental groups have listed pollock as a sustainable fish food compared to other seafood in that the harvest does not seem to significantly harm the environment or severely deplete fish stocks.  The Marine Stewardship Council, an independent global nonprofit organization, has certified Alaskan pollock as a sustainable fishery.

NOAA Scientist Abby separates out Chrysaora melanaster, common name Lions Mane.
NOAA Scientist Abby separates out a Chrysaora melanaster jellyfish.

Although we are not dealing with by-catch directly, I find the connection between by-catch, sustainability and fish stocks very interesting. The Echo Integration Trawl Survey uses acoustic data to estimate pollock populations. When we put out our nets we do so to obtain a sample of fish, detected by our acoustic instruments. Since we are conducting mid-water trawls we bring up mostly pollock. The non-pollock species that occasionally get caught in the net are important in verifying the acoustic data and to know what is in the water column with the target species. As a science teacher, the diversity makes for interesting fishing and I have been able to observe a few organisms that spend most of their time in deep water. I have shared some of my images of the unusual species below, all of which I had never seen before this trip. Many of the organisms we bring up go back into the water after we record the data but some of our catch makes it to the galley to be served up for meals.

More Invertebrates 

Some type of sea pen
Some type of sea pen
Small squid
Small squid
Flathead Sole (Hippoglossoides elassodon). Flatfish tend to swim higher in the water column in the evening following the plankton
Flathead Sole (Hippoglossoides elassodon). Flatfish tend to swim higher in the water column in the evening following the plankton
Greenland Turbot (aka Greenland Halibut)
Greenland Turbot (aka Greenland Halibut)
Pacific cod (Gadus macrocephalus)
Pacific cod (Gadus macrocephalus)
Pacific Herring (Clupea pallasi)
Pacific Herring (Clupea pallasi)
Great Sculpin (Myoxocephalus polyacanthocephalus)
Great Sculpin (Myoxocephalus polyacanthocephalus)
Smooth lumpsucker (Aptocyclus ventricosus)
Smooth lumpsucker (Aptocyclus ventricosus)
Shrimp from a night trawl
Shrimp from a night trawl
Kier, Chef and Assistant to the Chief Steward, makes a serious shrimp bisque.
Kier, Chef and Assistant to the Chief Steward, makes a serious shrimp bisque.
Catch of the day: Chief Steward Rick cooks up Pollock Fish and Chips
Catch of the day: Chief Steward Rick cooks up Pollock Fish and Chips

Bird of the Day: Turns out, there is no such thing as a seagull. This was passionately explained to me by birder who will remain nameless. You ask, why no seagulls? Simply the term is not used in the scientific community. There are seabirds and of this general group there are well over 100 species of gulls. Some gulls are found well inland. Some species of land-based gulls have become popularized due to their opportunistic feeding around humans. Many of the pelagic gulls I have seen this trip are not as well trained as the ones in NYC and stick to wild foods, not even accepting the occasional fish scraps I have tempted them with off the back deck. I had reported in a previous log seeing Kittiwake’s and some immature Herring Gulls. Today we saw a Slaty-back Gull. It is a handsome gull with striking contrasts of black, dark grey and white. They seem to turn up more each time we reach the northern end of a transect line (above 60° latitude). I also learned that the red spot on the beak is a sign of maturity in many adult gulls. I have a renewed appreciation for gulls and look forward to identifying the species back home.

Bottom trawls, conducted on the previous leg of this study, tend to have more diversity in the sample
Bottom trawls, conducted on the previous leg of this study, tend to have more diversity in the sample

Personal Log

We are approaching the northwestern edge of our transect field and the water is deeper and colder and we are finding less fish. I am lucky to find more time to spend on the bridge and witness the communication with Russian fishing vessels, jumping salmon and occasional marine mammal sightings. I have a little camera envy. Some of the folks aboard have the right lens and the right camera to catch the action out at sea. My little 4X zoom digital is looking mighty bleak on the deck and thus I need to rely on the serious photographers for images of some of these exciting finds; their generosity in sharing their images is most appreciated.

Slaty-Back Gull
Slaty-Back Gull

Question of the Day 

Today’s question: How does one become a Golden Dragon?

Previous Question: Why do pollock rise in the water column at night? 

Much of the food eaten by pollock fluctuates in their vertical migration depending on light penetration. During the daylight hours many of the euphausiids (krill) can be found lower in the water column. It seems that by staying lower in the darker portions of the water column during the day, zooplankton may be more protected from their major predators. Near the surface, the phytoplankton (algae) uses the sun’s energy to produce food all day. As the light fades the zooplankton rise, feeding on algae, and the pollock follow their food source.

Krill from one of our nighttime raids with the Methot Trawl
Krill from one of our nighttime raids with the Methot Trawl
Krill (pollock food): Partially digested from inside the stomach of a pollock
Krill (pollock food): Partially digested from inside the stomach of a pollock
Pollock gill rakers screen food from leaving the oral cavity as the water passes out of the gill slits, oxygenating the gills
Pollock gill rakers screen food from leaving the oral cavity as the water passes out of the gill slits, oxygenating the gills

 

Roy Arezzo, July 19, 2007

NOAA Teacher at Sea
Roy Arezzo
Onboard NOAA Ship Oscar Dyson
July 11 – 29, 2007

Mission: Summer Pollock Survey
Geographical Area: North Pacific, Alaska
Date: July 19, 2007

Weather Data from Bridge 
Visibility: 10+ nm (nautical miles)
Wind direction: 270° (SW)
Wind speed: 11 knots
Sea wave height: 5 foot
Swell wave height: 5feet
Seawater temperature: 8.1°C
Sea level pressure: 1004.4 mb (millibars)
Air Temperature: 9.7°C
Cloud cover: 6/8, stratus

NOAA’s Lieutenant Commander D. ZezulaReading the chart of the North Bering Sea
NOAA Lieutenant Commander D. Zezula reading the chart of the North Bering Sea

Science and Technology Log

I would like to thank David J. Zezula, Lieutenant Commander for NOAA and Alaska Region’s Navigation Manager, who spent over an hour showing me charts and resources for my school. David is serving as a relief officer of the deck aboard the OSCAR DYSON. Around our second Transect this leg we needed to break off from our line momentarily to avoid some shallow pinnacles listed on the chart.  Of the three, one pinnacle is charted in deep water and the tall thin pinnacle seems an unlikely seafloor feature. I was surprised to learn that the information on the printed chart was different from the digital GLOBE program the scientists use to assess the bottom. It was indicated on the printed chart that these shallow regions were charted back before we started making seafloor maps using multi-beam sonar technology. The actual depth in that region is thus questionable and rather than sail over what seemed like deep enough water we cruised around it for safety precautions. Our draft is about 29 feet and all of sensors are located on the centerboard that extends down below the hull’s lowest point. As a research vessel we care very much about our sensors.

Long-tail Jaeger photographed off the bow of OSCAR DYSON by Tamara K. Mills
Long-tail Jaeger photographed off the bow of OSCAR DYSON by Tamara K. Mills

I asked David about this and he went to his files and was able to show me more information about the dates and background on that specific chart. Some of the archives he has access to were actually scanned from hand written charts created with lead lines back at the turn of the century. One of the main parts of his job back on land is to help prioritize what regions of Alaskan waters are to be updated with modern technology as part of NOAA’s Office of Coast Survey (the hydrographic and nautical charting division of NOAA). Obviously they focus on key ports and channels first but there is much water out there to chart and verify.

Bird of the Day: Today I was fortunate to see yet another “new to me” species. The Long-tail Jaeger (Stercorarius, longicaudus) is a pelagic seabird that rules the air. Although it probably eats some fish near the surface it is famous for its aerial piracy. It is a very muscular bird that is capable of upending flying birds forcing them to regurgitate their stomach contents to obtain a meal.  This is currently their breeding time so it is early in the season for them to be found this far out at sea but soon mature adults and their grown offspring will be out on the Bering looking for food before their winter migration to the south. I keep missing the albatross sightings and hope that it will be my next bird of the day. Information provided courtesy of Mark Rauzon, birder, author, educator and friend.

OSCAR DYSON’s centerboard
OSCAR DYSON’s centerboard

Personal Log

Land! It was very exciting to see land for many reasons. First, the sun was out, a rare treat on the Bering. Many of the weather entries above will list the cloud cover as 8/8, which means out of 8 parts of sky all of it is covered by clouds. Also the visibility was good and the seas, which turned up with some high winds last night, had calmed down considerably. Lastly we were looking at Russia, many of us for the first time, which made sense since we were in the north part of our third transect line in Russian waters. It was also the first time we have seen land since we left Dutch Harbor. Cape Otvesnyy, at 860 meters high was visible from about 63 miles away. We all went outside the bridge to take photos and celebrate.

Question of the Day 

Today’s question: Why do pollock rise in the water column at night?

Previous Question: How is the field of acoustics used in science? 

OSCAR DYSON’S deck crew attaches an acoustic device (yellow) to the fishing gear
OSCAR DYSON’S deck crew attaches an acoustic device (yellow) to the fishing gear

Acoustics is a huge area of technology that ranges from how we design theaters to the use of sonograms to view unborn children. Much of the acoustic technology used in science has to do with creating alternative ways to observe different environments. Light does not travel through water as far as sound (vibrations). Sound waves are the key to looking deep into water. Marine mammals know this and can find prey with echolocation, reading reflected sound waves they send out to locate food and communicate.

On OSCAR DSYON we use several types of acoustic instruments

The Simrad EK60 is our main fish counting instrument and it uses about a 7º beam to send out sound waves of different frequencies and receive echoes from organisms and objects of different sizes. It is mounted on the centerboard and reads information from 5 frequencies ranging from 18 to 200 KHz. As we run along our transect line the data that is received is used to estimate the fish density. The scientists onboard spend a fair amount of time checking to see that the echoes actually represent pollock.

The ME70 Multi-beam is mounted to the ship’s hull and is a powerful tool in creating a wide swath three-dimensional image of what is below the ship. This is especially useful in hydrographic work that involves charting and mapping the seafloor bottom but it may be used for the fish survey in the future. The Acoustic Doppler Current Profiler  (ADCP) is also connected to the centerboard and uses the Doppler Effect (the change in frequency and wavelength of a sound pulse as perceived by an observer moving relative to the source of the sound) to estimate current and fish speed.

We place a Net Sounder (FS70, affectionately known as the turtle) on to our fishing n each time we trawl. Like scientists, commercial fishermen often use this instrument to monitor the shape of the net opening and the amount of fish entering the net.  It does this by sending a 200 kHz frequency beam across the opening of the net and transmits data along a cable for the team to see on our monitors. Along with the turtle we send down a Simrad ITI, which is smaller and wireless but a lower resolution net sounder that is used as backup in the event we have trouble with our cable.

The DIDSON (Dual Frequency Identification Sonar) is an instrument that has been developed for divers in low visibility water and has many industrial applications. It creates an image typical to the one seen on sonogram tests. It uses a high frequency beam (up to 1.8 MHz) to achieve a short-range image (up to 50 meters). It has been applied to salmon return rate studies and has well enough resolution to make out the shape of a moving fish. The pollock survey team has been experimenting with it as a way to monitor fish escapement from the net and how fish behave within the net.

In our survey work most of our mid-water trawls occur between 17 and 700 meters. The acoustic technology is vital to verify fish at these depths.

Roy Arezzo, July 16, 2007

NOAA Teacher at Sea
Roy Arezzo
Onboard NOAA Ship Oscar Dyson
July 11 – 29, 2007

Mission: Summer Pollock Survey
Geographical Area: North Pacific, Alaska
Date: July 16, 2007

We love Plankton
We love Plankton

Weather Data from Bridge 
Visibility: 8 nm (nautical miles)
Wind direction:   260° (SW)
Wind speed:   6 knots
Sea wave height: 1 foot
Swell wave height: 3 feet
Seawater temperature: 9°C
Sea level pressure: 1014.4 mb (millibars)
Air Temperature:   8°C
Cloud cover: 8/8, stratus

Science and Technology Log: Why fish pollock? What do pollock fish? Pelagic Food Webs of the Bering Sea 

Surveying pollock on the Bering shelf provides the data needed to set catch limits to manage the fishery. Catch limits for American fishing fleets are to be decided soon for next year. The pollock survey I am part of as Teacher at Sea is technically known as the Echo Integration Trawl Survey been an annual tradition of NOAA since 1971! The OSCAR DYSON, and before her the MILLER FREEMAN, use traditional trawling gear to achieve this goal. The fishing gear tends to be smaller then the larger fishing vessels since we don’t need to catch as many fish to estimate population trends. Like commercial operations we are interested in where the fish are in the water column and their geographic distribution. We also are concerned with their age composition. Although we primarily use acoustic sensors to detect fish, by trawling we can see how the technology used to locate fish in the water matches with what is being caught in the net. We also monitor by-catch organisms to observe what is mixed in with pollock when trawling.

Aleutian Islands
Aleutian Islands

Dutch Harbor, AK, according to the National Fisheries Service continues to be the No. 1 port by weight for seafood landings. In 2005, 877 million pounds of seafood passed through port, in 2006 it was more. In terms of seafood value only New Bedford, Mass., surpasses Dutch Harbor mostly due to the increase in the scallop market and decrease in crab populations. Dutch Harbor is known for its king crab industry in the winter and finfish year round, including hake, cod and salmon. Although shrimp is American’s most popular seafood item in terms of sales, finfish occupy much of the top five. Canned tuna is second highest for sales in the U.S., salmon is third and then pollock and tilapia; however if you factor in the global market, the amount of pollock being harvested and the sales for food products such as frozen whitefish foods, filets and surimi (Asian fish paste used in foods such as artificial crab) make it the largest seafood industry in the world (Anchorage Daily News). In addition Pollock are seasonally fished for roe. Commercially, fishing pollock is a good business venture due to its large schools and typically low by-catch. According to the National Marine Fisheries Service approximately 307 million dollars in pollock sales was made in the U.S in 2005. More than 3 million tons of Alaska pollock are caught each year in the North Pacific from Alaska to northern Japan. Of that the U.S. is responsible for about half. The population of Pollock in the Bering alone was estimated at 10 million metric tons early this decade and the catch limit was set around 10 –15% of the population size. Last year the survey team found a significant decline in populations and thus the catch limit was lowered but anecdotally there are preliminary signs of good recruitment with many young pollock being identified in this summer’s survey.

Assorted diatoms
Assorted diatoms

We are clearly at the top of the food web and consuming a large amount of pollock. The pollock are part of a very complex ecosystem. They are fragile fish and short lived but fast growing and quick to reproduce. The pollock population seems to be greater in number then most other harvestable finfish in the Bering, possibly due to a decline in Pacific Ocean perch, and shows interesting fluctuations in population density in response to global climate changes and sea current patterns. The Bering Sea lies between the Arctic Ocean to the north and the North Pacific to the south but remains a unique ecosystem exhibiting some characteristics of each of its neighbors.

Jellyfish found in the plankton net - large plankton!
Jellyfish found in the plankton net – large plankton!

The food web of the pelagic zone of open water in the cold Bering Sea is contingent on movement of nutrient rich waters. The main source of nutrients for the upper shelf region where one finds pollock seems to be influenced by the flow of the Alaskan Stream near shallower coastal waters which flows east across the Aleutian chain. Some of the water flows up through passes and becomes parts of currents like the Aleutian North Slope Current that feed the shelf. The Bering Sea is an extremely large and a relatively shallow body of water making it very different and it is this nutrient flow between shallow waters of the coast and shelf and deep basin/trenches to the west and south that account for its high biodiversity. In addition to currents ice melt and water temperature greatly affects nutrient flow and productivity. The nutrient rich water enables phytoplankton to flourish and reproduce in otherwise cold barren water. In turn zooplankton feed on the phytoplankton which transfers the organic carbon foods from producers to other levels of the food web. Invertebrates (ex. crabs, shrimp and jellyfish), small birds, small fish and baleen whales feed on the zooplankton. Seals, sea lions, skates, larger seabirds, porpoises and toothed whales feed on the fish and invertebrates. A substantial portion in the diet of larger pollock is made of plankton such as krill. This is the same food baleen whales filter out of the water when feeding.  Krill is the common name of shrimp-like marine invertebrates belonging to the order of crustaceans called the Euphausiids. Adult Pollock also dine on smaller pollock and this has been seen in our harvest as some pollock come up from the net with smaller fish in their mouth or stomach contents.

Pollock larvae
Pollock larvae

What is plankton? 

Plankton is a general word used to describe aquatic organisms that tend to drift with the current and are usually unable to swim against it. They are generally buoyant and found in the epipelagic zone (top of water receiving sun energy) although many species have serious vertical migration to feed and escape predators.  Most folks think of plankton as being tiny but large seaweeds and jellyfish are considered plankton. Phytoplankton refers to algae and photosynthetic organisms that make food with the sun’s energy. Diatoms are important phytoplankton in the Bering Sea ecosystem an have amazing silicon patterns. Zooplankton includes many groups of animal-like organisms, including microscopic protozoa and tiny crustaceans such as daphnia and copepods. The copepods population seems like an important link in understanding survivorship of young pollock. Many benthic crustaceans and mollusks (oysters and clams) start their life cycle as free-swimming larvae high in the water column. Young fish such as pollock also start their life cycle as plankton-like larvae.

Methot net, flow meter, and emptying the plankton net
Methot net, flow meter, and emptying the plankton net

Observing and Measuring Pollock Food: Last night we did a Methot Trawl. This involves dragging a net with a finer mesh than our fish trawl to pick up plankton. This is important in understanding what the fish we study are eating. When we dissect the belly of a pollock we often find it full of zooplankton with the occasional small fish, such as smelts or young pollock. We correlate the mass of the plankton caught in the net with the flow rate to estimate population density. We estimated 44,000 critters in the 35,000 cubic meters of water that passed through the net, much of which consisted of Euphausiids and Amphipods. This works out to approximately 1.3 plankton organisms per cubic meter of water.

Euphausiid pictured left and Amphipod pictured right
Euphausiid pictured left and Amphipod pictured right

Personal Log

The Bering Sea has been relatively calm with good visibility. We have seen our first boats in over 36 hours, some fishing boats and a Coast Guard Cutter. There have been some marine mammal sightings but nothing close enough to make an ID. I am settling into a bit of a routine, waking around 10:30 AM for lunch and then relaxing and working out before checking in for my shift at 4 pm. I spend a fair amount of my off time in our spacious bridge discovering new technological toys and looking out for wildlife. Each day I spend some time out on the deck above the bridge for fresh air.

Mature Female Pollock with visible eggs
Mature Female Pollock with visible eggs

After dinner we usually begin fishing and I don my foulies and safety equipment and observe operations from the back deck. I then photo anything new that comes in and try to process any bycatch to make sure it is returned to the water quickly and in good shape. The science team then works together, processing the pollock and helping with the clean up. Sometimes the fish schools are large so we have to stay in our gear and work back to back trawls. After trawling we often look at the data collected or deploy various test equipment and water quality checks. Nighttime is not best for trawling so the few hours between sunset and sunrise is reserved for special project applications designed to modify our methods. In between fishing I work on my Teacher-At-Sea writings and interviewing folks on the boat.

Mature Male Pollock; testis visible above
Mature Male Pollock; testis visible above

Question of the Day 

Today’s question: How is the field of acoustics used in science?

Previous Question: How does one tell a male fish from a female fish in Pollock?  

Male and female Pollock look the same from their exterior anatomy. Although we weigh and catalog all the fish we pull in, we sex a 300 fish sample batch from each trawl. This involves dissecting the fish to identify their gonads. We make a cut on the ventral surface from the gills towards the anus. We open the body cavity and move the liver to the side to expose the other internal organs. Gravid females are relatively simple to ID since they have large egg sacks with whitish eggs. A mature female will have a large ovary that tends to be reddish and lined with blood vessels. Immature females are more difficult to identify and have a less pronounced ovary that varies in color.

Mature males will have developed white coiled testis. For undeveloped males one looks for pink globular organs where the white testis should be. Immature males are more difficult to identify but when no ovary is visible we search for a thin membranous tissue running from the Uro-genital opening up into the body cavity towards the backbone.

Interested in more about Alaskan fisheries?

NOAA Alaska Fisheries Science Center

Pacific State Marine Fisheries Commission 

Anchorage Daily News