Roy Arezzo – NOAA Teacher at Sea Blog

July 28, 2007April 1, 2021

Roy Arezzo, July 28, 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 28, 2007

Weather Data from Bridge
Visibility: 10 nm (nautical miles)
Wind direction: 240° (SW)
Wind speed: 10 knots
Sea wave height: 3 foot
Swell wave height: 0 feet
Seawater temperature: 8.6 °C
Sea level pressure: 1020.5 mb (millibars)
Air Temperature: 0°C
Cloud cover: 8/8, Stratus

Creature at Sea: Roy holds a sea pen in the top picture and a basket star (bottom) from the bottom trawl study — Creature at Sea: Roy holds a sea pen

Science and Technology Log: Wrap Up

The Echo Integration-Trawl Survey of Walleye Pollock closed the season with a total of 74 Aleutian wing trawls (AWT mid-water trawls), 19 bottom trawls, 27 Methot trawls (plankton) and 81 ConductivityTemperature-Depth Sensor Package deployments (CTD water quality checks) collecting a wealth of biological and physical oceanographic data. The crew and scientists are excited to be headed back to shore but also there is a good feeling regarding the mission of the trip and the validity of the data collection. Of the 50,840 Kg of fish netted more then half was caught in the 44 AWT mid-water trawls executed this third leg of the survey. During this time we took the length of 16,761 individual pollock and identified 19 other species of fish.I spent some time looking at graphs of preliminary data to try and make sense of what was accomplished from the work done during the sail. This past winter had a higher incidence of sea ice relative to the previous years. Generally the colder and saltier the water, the greater the density and the deeper it sinks. Although this concept was illustrated in salinity measurements at different depths (deeper being saltier) we found this not to be true when looking at temperature profiles.

In the sea, deeper does not always mean colder. The Bering shelf is influenced by more than one current system and we found the data taken from the northern parts of the transect along the shelf had colder water than the southern areas as expected but along the slope near the edge of the deep basin the water remained consistently warmer relative to the shelf water despite the latitude change, rarely dipping below 1°C. Generally, we found colder water near the bottom of the shelf between 50 and 100 meters then we did near the bottom of the deeper slope at 200 meters or more. This is mainly due to ice melt in the northern latitudes slowly moving cold water along the bottom of the shelf, where as the deep basin and slope are influenced by slightly warmer currents moving northwest from the Aleutian chain. As a teacher working on the water in the east I came out here assuming the deep areas would be colder but instead I was schooled on currents and their influence on water temperatures.

Leg 3 Transects of Pollock Survey Area: Fish symbols indicate trawl locations. Circles represent CTD readings and diamonds represent the line between Russian and US fishing grounds.

Through much of the cruise the lead scientists on shift spend enormous amounts of time monitoring the acoustic signal (echograms) from sounds waves beamed below the ship. When they find a significant mass of pollock they often would take a sample – go fishing. Using patterns on computer monitors scientists are able to hypothesize which signals indicate pollock. Both the length data taken from measuring fish and the acoustic estimates are used to come up with biomass numbers. In the echogram in figure 3 there is what appears to be a signal indicating mixed size pollock. We know that pollock schools tend to be homogeneous with respect to age and size. The strong blue layer at the top of the echogram represents plankton near the surface and in this instance the fish are mostly near the bottom with larger fish indicated in blue and more evenly dispersed, while dense schools of small fish show up as odd shaped clumps with lighter colors. When we sampled this water we found this to be true; we observed two groups of pollock, large adults and small two year old juveniles. The data in Figure 4 (histogram lengths) shows the two size groups. Cannibalism may be part of the reason the smaller fish stick together in separate densely packed schools.

Temperature Profile from CTD readings

Conductivity (salinity) Profile from CTD readings

In the echogram, we see more evenly dispersed adult pollock. This is verified by the haul 92 histogram in figure 6 that shows that most of the pollock sampled where between 40 and 55 centimeters long. Looking at the distribution of pollock in our study area (Figure 7) shows a consistent band of greater incidence of fish near the slope particularly to the western parts of the study area. As the fishery scientists fine tune hydro-acoustic technology they hope to get a better understanding in zooplankton (Figure 8) trends that influence survivorship of young Pollock. A Krill Survey would be ambitious but by looking at the higher frequency acoustic waves, verified with Methot Trawls, one can estimate krill biomass in pollock regions. Environmental monitoring of chlorophyll concentration (phytoplankton measured from CTD water samples analyzed back on shore) and krill biomass (zooplankton) relative amounts from year to year can help create a better understanding of the resources necessary to support fish stocks.

FIGURE 7: Preliminary data of pollock distribution throughout the survey area

FIGURE 8: Preliminary data of zooplankton estimates through out the pollock survey area — FIGURE 8: Preliminary zooplankton estimates throughout the pollock survey area

I would like to thank Chief Scientist, Paul Walline and B-Watch Chief ,Patrick Ressler for taking the time to explain to me the science of hydroacoustic survey analysis and sharing with me their preliminary data.

Chief Scientist, Paul Walline, monitoring the echogram from the bridge of OSCAR DYSON.

Bird of the Day:

The bird survey folks identified over 35 species on our trip. I became familiar at least 6 species of birds that I felt comfortable identifying on the fly. When there were hundreds of birds circling the boat there was sometimes one type of bird that stood out making identification a snap. The Auks are related to penguins and have rounder body shapes and unique flight patterns. Like penguins of the southern hemisphere, the denser body composition makes them excellent at swimming under water, but they less nimble taking off and flying in the air compared to sleeker less dense seabirds like the gulls. Unlike penguins all 13 species of auks in the northern hemisphere can fly. The two most abundant types observed onboard are the Murres and the Puffins. I was fortunate to see two species of puffin this trip, the Horned and Tufted Puffin, seemingly too exotic for the Bering Sea. Both have specialized large colorful beaks for carrying multiple prey items and attracting mates. As we sail southeast we are fortunate to be seeing more of them.

Personal Log:

Patrick, always with a smile, takes a break from the computer screens to look at the catch.

These last few days, despite the lack of fishing, have not been without excitement. The bottom-study video sled captured Dall’s Porpoises swimming under water as it was deployed off the stern. As we head southeast there seems to be more whales and clearer skies. This evening we saw dozens of fin whales and one pod was feeding so close that I was able to see baleen. The whales’ baleen is used to screen their plankton food. I learned the Right Whale has asymmetrical coloring on its baleen and the right side has a lighter off-white color, which we were able to see from the port side of the ship. I would like to take this opportunity to express my gratitude to the crew of the OSCAR DYSON for their help in getting acclimated to the Bering and to NOAA’s Teacher at Sea program for providing this amazing experience.

Question of the Day

Today’s question: What is next for the OSCAR DYSON? She is headed back out to the Bering to find rare Right Whales. Check out ship tracker at NOAA’s website or the OSCAR DYSON Web site for more info.

Previous Question: How much fish did we catch? 26,575 kilograms (summer extra credit – convert this number to pounds and metric tons)

July 26, 2007April 1, 2021

Roy Arezzo, July 26, 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 26, 2007

Weather Data from Bridge
Visibility: 8-10 nm (nautical miles)
Wind direction: 220° (SW)
Wind speed: 11 knots
Sea wave height: 3 feet
Swell wave height: 0 feet
Seawater temperature: 10 °C
Sea level pressure: 1014.9 mb (millibars)
Air Temperature: 10°C
Cloud cover: 8/8, Stratus

Roy works with the deck crew to remove the “pea pod” from the trawl net.

Science and Technology Log: Special Operations

When a fully equipped research ship goes to sea everybody wants in. Any scientist doing work in a particular region needs access to that region to conduct their fieldwork. Fishery scientists often catch a ride with commercial vessels to do work at sea. A research vessel can be more desirable for certain projects and NOAA has a system for organizing request proposals and prioritizing work. Unfortunately, a boat is limited in the number of passengers, equipment, food and other resources it can carry. For example one scientist, who is not with us, has sent light meters onboard and requested we collect the data for him. The light meter mounts to our trawl net to study if light penetration affects the vertical distribution of walleye pollock. The pollock survey, the main project of the season, has a science team of 8 not including the birders, ship’s staff and Teacher at Sea. With this many scientists onboard the ship becomes a platform for an interesting mix of experimentation.

We finished the transects of the Pollock Survey and are now transiting southeast back towards Dutch Harbor. Tomorrow we launch “the sled”, a large metal-framed instrument equipped with an underwater video camera to record the sea bottom of a special study site. The purpose of the study is to assess the effect of bottom trawling on benthic habitats and measure recovery progress over time. The study site is an area that was bottom trawled back and forth around a month ago. The camera will be pulled in lines perpendicular to the tracks created by the trawling. I got a sneak peak at some of the video footage and the benthic habitat is flat and muddy with strange white sea pens poking upward around 5 feet. Crabs and flat fish scurry around while giant basket stars and sea anemones ornament the bottom. We will use some of our transit time to reflect on some of other side projects that occurred this trip, most of which were designed to refine and validate the survey methodology.

When the trawl catch is unloaded into the lab the sex, weight and length of individual fishes are recorded. To make the work more efficient, a new measuring board has been designed to length fish. This is the first time it was tested and it performed smartly. The board allows scientists to input digital length data by touching the sensor to the board at the end of the fishtail fork. NOAA Scientists, Rick Towler and Kresimir Williams, designed the instrument using magnetic sensors from scratch, and shared with me the details of their first project and how the length board evolved from an acoustic instrument through trial and error to the prototype we tested this year. When processing data from trawling, there is always a concern as to how to best represent biomass estimates. You should not count a fish that is 10 centimeters the same as you would a fish that is 40 centimeters. Although they would both qualify as one fish they have a different size and thus a different biomass. We know we cannot count every fish so we have different methods of estimating biomass.

Deck crew works to get fish out of the pocket nets

Not all fish are caught with the same efficiency; the retention of fish in a net must be taken into consideration. To compensate for this, an estimate as to fish escapement is often factored into the calculations for fish density. Fisheries Scientist, Kresimir Williams, wants to quantify fish escapement. He is using handmade “pocket nets” to study selectivity and sample escaped fish. In the evening we conducted experimental trawls to monitor escapement from our main trawl nets. We did this by attaching pocket nets to the outside of the trawl net in random placement and analyzing pollock caught in the smaller nets relative to the catch in the cod end. We have found that smaller fish (one year-old juveniles) more often escape the net from near the cod end as opposed to forward, where there is a larger mesh size. Although the data will not be analyzed until later, observations indicate this could be important in interpreting pollock survey results.

The “peas” are equipped with digital cameras

The most exciting project for me is the “Optical Pea Pod”, another Kresimir/Rick design. The pod houses 2 digital cameras, a timed circuit board and a strobe light that is lowered in the net to photograph fish at regular intervals. The setup is designed to produce calibrated stereo images of fish making it possible to measure fish length in deep water. Perhaps, in the future, the cod end can be left open allowing the fish to swim out safely as they are documented. The imaging data can possibly be used to verify the acoustic data that is currently used to estimate the population, reducing the need to handle fish on deck. I would like to thank my technical advisors, Kresimir and Rick, for involving me in their projects and for their support in my work as Teacher at Sea.

Bird of the Day

Adrienne and Travis test the empty peacameras pods for pressure down to 80 meters — Adrienne and Travis test the peacameras for pressure down to 80 meters

The Albatross is a seabird steeped in maritime folklore. Mariners of yore would tell stories of the souls of dead sailors rising when they saw the white bird. Famous for being one of the largest seabirds they are a magnificent sight. The Wandering Albatross is capable of extremely long migrations, circumnavigating the globe for years before settling down to breed. Albatrosses, of the biological family Diomedeidae, have recently been reclassified (based on recent DNA evidence) and the number of genii and species is widely disputed. What is clear is that many species are in danger of extinction. The greatest impact to their populations is long line fishing although many were slaughtered for their feathers before being protected after the turn of the last century. Swordfish, monkfish and cod are fished with long-lines involving miles of baited hooks that can attract the birds and lead to their entanglement and subsequent drowning. We have seen two species on this cruise, the Laysan and the Short-tailed Albatross. It is estimated that there are only between 1500 and 2000 Short-tailed Albatrosses remaining the world. Many were harvested for feathers and a volcano eruption at their Japanese breeding grounds decimated the remaining adults. Fortunately juveniles at sea have returned to breed and hopefully with protection, the numbers will continue to rebound. We were lucky to have one spend a fair amount of time of our stern in calm waters the other day as we were stopped for water quality testing.

Rick spends most of the sail tweaking the electronics and the software for things to work. In an attempt to upgrade the failing batteries of the strobe light he designs a super-battery housed in a milk carton.

Personal Log

The Bering is a surprisingly lovely color of blue and if the sun would ever come out I am sure it would accent the aesthetic of the water’s color. When we stop to check the water quality the CTD instrument makes for a decent secchi disk and I have observed anecdotally that the visibility seems to be around 13 meters or 40 feet. On an unrelated topic, the other day Executive Officer LT Bill Mowitt let me in on his “lesson plan” for the weekly drill. We went into a fan room and created an electrical fire scenario. We also left clues around the area for the crew and fire fighter team to assess and react to. When it came time for the actual drill I had front row seats to watch the drill unveil and was then permitted to test the fire house of the leeward side the ship. All went well.

Question of the Day Today’s question: How much fish did we catch? Previous Question: How does one become a Golden Dragon?

The short answer is one sails across the 180-degree line separating the eastern and western hemisphere. We did this going steaming to Russian waters continuing our survey work in the Northwest Bering.

Kresimir and Rick send the final prototype of the pea pod down in the trawl net

Pollock in the net down below 80 meters – caught and measured on camera

Another amazing in-flight shot by Tamara K. Mills

An Immature Short-tailed Albatross off the stern of the OSCAR DYSON (image by Mark Rauzon).

Executive Officer Bill Mowitt sets up a Fire Drill

July 23, 2007April 1, 2021

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

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

Flathead Sole (Hippoglossoides elassodon). Flatfish tend to swim higher in the water column in the evening following the plankton

Greenland Turbot (aka Greenland Halibut)

Great Sculpin (Myoxocephalus polyacanthocephalus)

Smooth lumpsucker (Aptocyclus ventricosus)

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

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

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.

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 (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

July 19, 2007April 1, 2021

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

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.

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

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.

July 16, 2007April 1, 2021

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

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.

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.

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.

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

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

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.

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

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

July 13, 2007April 1, 2021

Roy Arezzo, July 13, 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 13, 2007

Weather Data from Bridge
Visibility: 2 nm (nautical miles)
Wind direction: 227° (SW)
Wind speed: 4 knots
Sea wave height: <1 foot
Swell wave height: 4 feet
Seawater temperature: 8°C
Sea level pressure: 1010.3 mb (millibars)
Air Temperature: 5.8°C
Cloud cover: 8/8, stratus

Roy Arezzo, Teacher at Sea, on land before his sail, low visibility but great view.

Science and Technology Log: Introduction to the Pollock Survey

Where does one start? Monday, July 9, 2007, I left my apartment in NYC at 6:30 AM and by the time I was making a descent to OSCAR DYSON Seattle I started to realize I _{Pictured to right}was going far away. I was half way thereI then flew to Anchorage and finally took a small prop plane to Dutch Harbor. At 12 AM Eastern Standard time I was stepping out on the Tundra of Unalaska, my bag didn’t arrive until the next day. I had come a long way to fish, like many others, but this is the place to do it. The global fish market seems to just keep increasing and someone needs to be looking at the fish populations. That is where NOAA comes in. NOAA’s Teacher At Sea program sent me here and I ate some fresh salmon, some crab, hiked the tundra and soaked up the views in town before boarding for my expedition.

The OSCAR DYSON departed from the dock at 12 pm on Wednesday, July 11, 2007. I remained outside, above the bridge, watching land disappear for most of our transit past the sea buoy and into the Bering. Within two hours the U.S. Fish & Wildlife Service folks were camped out in the bridge collecting bird data. Knowing it would be some time before we reached our study area to fish, I spent most of my first two days up in the bridge absorbing ship operations, navigation technology, sea bird names and searching for marine mammals. Two hours into our trip we had spotted over a dozen Humpbacks’, one breaching off the port beam about a half mile out. Some came a fair bit closer.

Acoustic Image of the trawl net from the Bridge: The red line at bottom indicates the sea bottom. The circle represents the net and the specs inside the circle represent fish going in the net.

Within 24 hours we had seen and recorded information on 5 different whale species, including, Humpback, Fin, Orca, Sei and a Beaked whale, the Fin whales being the largest. The pod of Orca’s moved with a mission. Dall’s Porpoises were cruising in our wake as Murres, Tufted Puffins, Northern Fulmar’s, Black-legged Kittiwakes, Fork tailed Storm Petrels and some immature gulls, that I could not ID, circled above. It was a spectacular show to start our trip. Although the Ship has many projects going on at the same time the primary mission is to monitor Pollock.

Cruising at 12 knots for 2 days put us out on the first transect line. A transect line is a predetermined slice of ocean in a study area that we travel over in a straight line. Our mission is to spend 3 weeks monitoring the northern most region of a 9 week annual monitoring period (31 transects). We will travel northwest for most of the 3 weeks to cover all transects in this region. By 9 pm on Thursday we found ourselves on our first transect. When we pass over a transect line, which can be over a 200 miles long, we consistently send down sound waves from our center board several meters below any ship vibration. The reflection of sound waves from below can be interpreted as biomass data. Two science teams work 12 hour shifts to monitor the instruments and the data 24/7. The entire study covers the main area Pollock is found and fished in the Bering Sea. We can pick up small krill near the surface or schools hundreds of meters down depending on the frequency of the sound wave we use. On our monitors we get a visual image of the school of fish below us. When we find a significant fish footprint that resembles Pollock we put out trawl nets to catch an appropriate sample size. The ship has completed over 90 trawls in this study. When the nets come in we separate and record “by catch”, which I am happy to report there has been very little of (2 cod and some jellyfish). We then weigh all the fish, record size and sex on a sample size of 300. In addition we remove ear bones (the otolith) from 50 fish each trawl to age them back at NOAA’s lab headquarters in Seattle, WA. We have fished three times today and landed 3.65 tons of fish. The day is not done.

Personal Log

I am excited at the opportunity to work along so many experienced and knowledgeable crew members from the science team to the deckhands and to observe how they work together to reach the objectives of the mission. Folks here have interesting backgrounds ranging from surfing to tall ships to commercial crab fishing. The Ship is very comfortable and quiet for her size and workload. I have yet to see the dark but I will be up late tonight as I switch over to the 4pm to 4am shift. Fortunately there is a proper cup of tea and left over clam chowder to keep me awake and warm. I would like to thank Rebecca Himschoot, Teacher at Sea participant on the previous sail, for showing me around and providing invaluable insight into preparing for my trip. Thanks also to Amy and Forrest for a warm welcome to Alaska.

Question of the Day Today’s question: How does one tell a male fish from a female fish in Pollock?

The deck crew works a full net aboard NOAA Ship OSCAR DYSON.