In a previous post, I briefly mentioned that acoustics helps Oscar Dyson scientists locate aggregations of pollock. I didn’t know much about acoustics surveying before I arrived on board but think its pretty cool.The Oscar Dyson has 5 transducers on its center board and 1 temporary transducer on the side of the center board that looks horizontally. The transducers allow us to see where the fish are. Because of where the transducers are placed, we can only see the pollock from 16m to the bottom. This means that if there are any fish between the surface and 16m they will not be detected. This is the near surface “dead zone”. At right you will see a picture of the acoustic data picked up by the transducers. Why this happens? The transducers are mounted on the bottom of the centerboard about 9 m below the water line, and near the transducer face (first 7 m), no good data are collected. Why it’s okay? Pollock tend to hang out in mid-water. Although a few baby pollock might be in the near surface “dead zone,” the majority of pollock will be in the area we are watching. There is also a bit of a “dead zone” at the other end near the ocean floor.
Acoustic Data
Why acoustics?
Ideally, the acoustic data collection would allow us to track aggregations of pollock without actually having to fish them out of the water. All parties involved (scientists, fish, bank accounts) would benefit from this change but scientists are still in the process of perfecting this process. The Oscar Dyson is part of a fleet of five boats that was specifically designed for acoustics. Specifically, it is considered a “quiet boat” where the engine noise is decreased to prevent scaring the fish. Other acoustic projects include: Pacific hake off the coast from California to Vancouver Island (run as a joint project with Canada), herring in the northwest Atlantic, and krill in the Antarctic. Acoustics are used throughout the globe and many countries depend on acoustics for their fish surveys.
Sonar
Looking in more than one direction
Along with the transducers, there is also a multibeam SONAR that produces the same information as the transducers but with a wider angle range. Scientists use this program to help separate species in the water column. The multibeam ME70 sends its signal out after the transducers information is sent and returned. They alternate about 1.5 seconds apart. Scientists around the world are working to improve this technology and we use information from a group at University of New Hampshire along with a program from Tasmania to analyze these data. Scientists utilize the multibeam ME 70 along with the transducers and fish trawling to ensure they are capturing an accurate picture of the mid-waters.
How the survey data we collect are used.
The data we collect on the Oscar Dyson during the summer pollock surveys are used by scientists and policy makers to determine the fishing quota (the “take”) of pollock for the next season. Quotas are important for maintaining the population of pollock (and other species) for this generation and generations to come. The data we collect on the Oscar Dyson help ensure that maximum stock can be taken without negatively impacting the Eastern Bering Sea pollock population.Thought Question: What could happen if we didn’t regulate the amount of fish that could be caught? Bonus points for anyone who can identify an area where overfishing has impacted the ecosystem.
NOAA Teacher at Sea Michele Brustolon Onboard NOAA Oscar Dyson June 28 – July, 2010
NOAA Teacher at Sea: Michele NOAA Ship Oscar Dyson Mission: Pollock Survey Geographical area of cruise: Eastern Bering Sea (Dutch Harbor) Date: July 1, 2010
Weather Data from the Bridge
Time: 1400 Latitude: 58.19 N Longitude: 170.01 W Cloud Cover: 100%, dense fog Wind: 11.49 knots Air Temperature: 3.800 C/ 38.840 F Water Temperature: 3.960 C/ 39.1280 F Barometric Pressure: 1003.10 mb
Science and Technology Log
Here fishy fishy!
July 1st began by spending time in the Acoustics Lab learning about the equipment used to analyze the data. The Oscar Dyson has 5 transducers on its center board and 1 temporary transducer on the side of the center board that looks horizontally. The transducers allow us to see where the fish are. Because of where the transducers are placed, we can only see the pollock from 16m to the bottom. This means that if there are any fish between the surface and 16m they will not be detected. This is the near surface “dead zone”. Why this happens? The transducers are mounted on the bottom of the centerboard about 9 m below the water line, and near the transducer face (first 7 m), no good data are collected. Why it’s okay? Pollock tend to hang out in mid-water. Although a few baby pollock might be in the near surface “dead zone,” the majority of pollock will be in the area we are watching. There is also a bit of a “dead zone” at the other end near the ocean floor. Yesterday the bottom was around 69.35m.
Transducer data
Why acoustics? Ideally, the acoustic data collection would allow us to track aggregations of pollock without actually having to fish them out of the water. All parties involved (scientists, fish, bank accounts) would benefit from this change but scientists are still in the process of perfecting this process. The Oscar Dyson is part of a fleet of five boats that was specifically designed for acoustics. Specifically, it is considered a “quiet boat” where the engine noise is decreased to prevent scaring the fish. Other Acoustic projects include: Pacific hake off the coast from California to Vancouver Island (run as a joint project with Canada), herring in the northwest Atlantic, and krill in the Antarctic. Acoustics are used throughout the globe and many countries depend on acoustics for their fish surveys.
A little help from UNH! Along with the transducers, there is also a multibeam SONAR that produces the same information as the transducers but with a wider angle range. The multibeam ME70 sends its signal out after the transducers information is sent and returned. They alternate about 1.5 seconds apart. The University of New Hampshire (UNH) is helping to use the tool and also to analyze the data. To analyze the transducer data collected, a program is in place from Tasmania to help determine what the boat is seeing. The scientists use the program to help separate species in the water column. Scientists utilize the multibeam ME 70 along with the transducers and fish trawling to ensure they are capturing an accurate picture of the mid-waters.
Multibeam ME70 data
How the survey data we collect are used. The data we collect on the Oscar Dyson during the summer pollock surveys are used by scientists and policy makers to determine the fishing quota (the “take”) of pollock for the next season. Quotas are important for maintaining the population of pollock (and other species) for this generation and generations to come. The data we collect on the Oscar Dyson help ensure that maximum stock can be taken without negatively impacting the Eastern Bering Sea pollock population.
Here I am deploying the XBT (eXpendable bathymetric thermograph)
Personal Log
Although there was no fishing yesterday, I certainly was able to be involved. I launched the XBT off the Hero Deck just as we began our fire drill. Once that was completed I returned to the Acoustics Lab until we were cleared from the drill. We then had our abandon ship drill where we get our survival suits and head to our assigned position. My meeting location is at life raft 3 and 4. Once we learned how to deploy our life raft, we headed inside to the conference/lounge to practice donning our suits. While this is very serious, it is also worth a laugh or two watching people struggle and become orange gumbies! The goal is to be able to don your suit in under 60 seconds!
Zodiac ride into the cove of St. Paul’s Island
Yesterday I had the opportunity to head into St. Paul’s Island; the largest of the Pribilof Islands. St. Paul’s is also called the Galápagos of the north. The Zodiac was driven by Joel Kellogg and Amber Payne, and our CO (Commanding Officer Mike Hoshlyk) allowed Katie, Rebecca, and I the opportunity to take the trip inland. Our mission while on land was to bring science equipment (ice-flow detector) to the airport that needed to be sent to Anchorage. Stepping foot onto St. Paul’s Island seemed eerie and mysterious. There was the lurking fog along with a very industrial feel to the island. Because most of the island consists of coalescing small volcanoes, the sediment’s dark color is due to lava flow which didn’t brighten the land at all. We did not see many people other than those working on dredging the new causeway or the people in the airport. Our taxi driver said that they hadn’t gotten mail since Monday and it was Thursday which explained why the people waiting for flights at the airport seemed a bit anxious. On our way back to the boat, we were able to see sea lions and some puffins hanging out in the water and around the break wall. As we approached the boat, it was like an apparition appearing before us. Just another once in a lifetime chance that I have had this cruise!
NOAA Teacher at Sea
Richard Chewning
Onboard NOAA Ship Oscar Dyson
June 4 – 24, 2010
NOAA Ship Oscar Dyson Mission: Pollock Survey Geographical area of cruise: Gulf of Alaska (Kodiak) to eastern Bering Sea (Dutch Harbor) Dates: June 6-7, 2010
Weather Data from the Bridge
Position: Snakehead Bank, Gulf of Alaska Time: 1700 hrs Latitude: N 56 00.390 Longitude: W 153 46.380 Cloud Cover: Overcast Wind: 12 knots from the SE Temperature: 7.1C Barometric Pressure: 1016.9 mbar
Science and Technology Log
I have been impressed by the wide array of oceanographic research the Oscar Dyson is able to conduct. A few examples include biological studies of organisms ranging from microscopic plankton to massive marine mammals, collecting a variety of weather data, describing both physical and chemical characteristics of seawater (such as temperature, salinity, chlorophyll, and dissolved oxygen), conducting acoustic surveys of marine life and the sea floor, and much more.
Three Saints Bay nautical chart
One of the Dyson’s ‘bread and butter’ surveys is our survey studying the distribution, biomass, and biological composition (male/female ratios and age) of walleye pollock in the Bering Sea. Walleye pollock is a very important fishery for Alaska. You have almost certainly been a part of this fishery as most fish sandwiches in fast food restaurants and fish sticks in the frozen food section of your local grocery store are Alaskan-caught pollock.
One of the Oscar Dyson’s many tools for this research is her impressive array of acoustic sensors located on the ship’s hull and centerboard. The centerboard is an extension of the hull that can be raised and lowered in the water in order to position most of the Dyson’s sensitive acoustic sensors below the bubbles often found near the water’s surface. These air bubbles interfere with sound traveling through the water and degrade the quality of the data being collected. The Dyson has six downward looking centerboard-mounted transducers, each transmitting a different frequency. Why so many frequencies? Since different types of marine organisms interact with sound waves differently producing varying acoustic signatures, the Dyson must be equipped with a variety of sensors to best characterize the variety of marine life encountered during a survey.
For example, lower frequencies are better suited for fish such as pollock and the higher frequencies are better suited for smaller organisms such as plankton. Think of transducers as a downward shining flashlight illuminating the depths of the ocean with sound rather than light.
The Dyson also has other acoustic sensors such as the ME-70 multibeam echosounder that has the unique ability to look over a much wider angle through the water. Acoustic research works on the same echo location principle that bats and marine mammals employ to find food and navigate. By sending out sound waves and measuring the time the sound takes to travel back after encountering an object, one can learn a great deal about that object’s properties such as distance, size, and movement.
Before traveling to the Bering Sea to start our pollock survey, the Dyson’s scientists must take great care to ensure that their echo-sounding equipment is calibrated correctly. Calibrating the transducers is similar in concept to tuning a piano string or zeroing a sight on a rifle. To this end, the Dyson anchored in Three Saints Bay, a sheltered bay protected from the wind, waves, and currents of the open ocean, at least theoretically. While a troublesome storm passed almost directly overhead, scientists from the Midwater Assessment and Conservation Engineering (MACE) Program (part of the Alaska Fisheries Science Center (AFSC) located in Seattle, WA), the US Fish and Wildlife Service (FWS located in Anchorage, AK), and the Pacific Institute of Fisheries and Oceanography (located in Vladivostok, Russia) worked diligently to fine tune their acoustic sensors.
Copper sphere used to calibrate the acoustic sensorsBill and Patrick positioning spheres under the Dyson
Paul Walline, Patrick Ressler, Darin Jones, Bill Floering, and Mikhail ‘Misha’ Stepanenko worked day and night calibrating their equipment using metal spheres positioned directly under the ship.
Spheres of different sizes and materials with known acoustic signatures (such as tungsten carbide and copper) are used to calibrate the transducers.
The crew of the Dyson works around the clock as ship time is precious. The scientists work 12 hour shifts, either from 4am to 4pm (the shift to which I am assigned) or from 4pm to 4am. The acoustics lab where the data is collected and analyzed is affectionately called ‘The Cave’ as there are no portholes (windows) to tell the time of day outside.
The acoustic lab, a.k.a. “the cave”
Personal Log
I wasn’t sure when the Dyson arrived at Three Saints Bay as I had retreated to my stateroom early in the evening of the 4th as I was feeling the effects of the rolling seas. I am being berthed with the ship’s 2nd Cook, Floyd Pounds, who is also from Georgia but now calls the Dyson home.
Floyd works with the Chief Steward, Rick Hargis, who has been with NOAA for 20 years and is originally from Washington State. So far the meals have been very filling and satisfying (there is even an ice cream bar!).
My stateroom is located on the crew deck, one level below the main deck near the bow (the pointy end of the ship) on the starboard side (the right side when facing the bow). Utilizing every nook and cranny and with no wasted space, my berth is quite cozy and is surprisingly comfortable. Fortunately with the help of some seasickness medication, I soon found my sea legs and awoke feeling refreshed and hungry (always a good sign!). Seasickness comes from conflicting messages received from the inner ear and the eyes by the brain (the inner ear feels the motion of the boat rolling and pitching in the water but the eyes report a stable environment confusing the brain).
Snug as a bud in a rugRichard, ready for a swim
A person soon observes that safety is paramount onboard the Dyson as with any NOAA vessel. For example, within 24 hours of leaving Kodiak, the entire crew conducted fire and abandon ship drills. These drills are conducted once a week and are essential for maintaining readiness in the event of an emergency. During the abandon ship drill, I was able to practice donning my survival suit just like our visiting Coast Guard kids did in Kodiak! Although the suit is designed to be quite snug to keep cold water out and to keep the body warm, I was thankful I didn’t have to put the suit to the test by going over the side. To my surprise, Chief Marine Engineer Jerome ‘Jerry’ Sheehan and ENS Russell Pate did just that, going for a dip in the frigid 7.3 degrees Celcius or ~45 degrees Fahrenheit waters! Jerry and Russell used dry suits to scuba dive under the Dyson to check the hull, the prop, and the transducers for anything out of place such as barnacles on the transducers or tangled fishing gear. The only discovery was of a piece of bull kelp snagged on one of the blades of the prop which may explain a noise that was heard on the hydrophones (microphones located under the Dyson’s hull) during our departure from Kodiak.
CO Hoshlyk overseeing recovery divers Jerry Sheehan and ENS Russell Pate
After completing our calibrations and safety operations, the Dyson sailed for a site called Snakehead Bank located 60 nautical miles southeast of Kodiak. The name comes from the bathometric profile of the seafloor of this area which resembles the head of a snake. We soon began conducting camera operations for ground-truthing sea floor composition that I will discuss in my next log!
Remnants of Nunamiut, earliest Russian settlement 1792 in three saints bay, KodiakDeparting Three Saints Bay
Where did the NOAA ship Oscar Dyson’s name originate?
The Oscar Dyson is named for an Alaskan fisherman who was very influential in fisheries development and management in Alaska. From his days as a commercial fisherman, Oscar Dyson was a pioneer and advocate for Alaska fisherman and was very influential in the growth of this important industry. Alaska’s commercial fishing industry spans the state and includes salmon, herring, pollock, various shellfish, and various ground fish like halibut. While traveling through the Ted Stevens International Airport in Anchorage, I learned that Alaska is a land defined by water with more than three million lakes and more coastline than the rest of the United Sates combined! Alaska is also the only state in the US to have coastlines with three different oceans/seas: the Pacific Ocean, the Arctic Ocean, and the Bering Sea.
NOAA Teacher at Sea: Karen Matsumoto Onboard NOAA Ship Oscar Elton Sette April 19 – May 4, 2010
NOAA Ship: Oscar Elton Sette Mission: Transit/Acoustic Cetacean Survey Geographical Area: North Pacific Ocean; transit from Guam to Oahu, Hawaii, including Wake Is. Date: Friday, April 29, 2010
Science and Technology Log
We passed over a seamount, which is an undersea mountain that rises from the seafloor (usually volcanic) to an elevation below sea level. Seamounts often project upwards into shallower zones and are more inviting to sea life, which provide habitats for marine species that are not found on or around the surrounding deeper ocean bottom. This may explain the numerous sightings we have experienced the past couple days.
In addition to simply providing physical presence, the seamount itself may deflect deep currents and create upwelling. This process can bring nutrients into the photosynthetic zone, producing an area of activity in an otherwise desert-like open ocean. These seamount areas may be vital stopping points for some migratory animals such as whales and seabirds. Some recent research also indicates that whales may use seamount features as navigational aids throughout their migration.
I have been working primarily with the acoustics group, launching and monitoring sonobuoys. Over the past couple days, we have detected minke whale boings and sperm whale clicks on a consistent basis. Our sonobuoys did not pick up the whistles of the melon headed whales, but these high frequency whistles were showing up on the towed hydrophone array. Often when visual sightings are reported to acoustics from the “flying bridge” observation deck, we have long been monitoring their vocalizations!
Sperm Whale. NOAA photo
Finding and observing cetaceans while at sea is very challenging, and viewing conditions are strongly dependent on weather and sea conditions. I also spent a couple days with the visual monitoring team up on the “flying bridge.” Because we are looking for visual observation cues up to a distance of several miles using the “Big Eyes” binoculars, it is critical that the observer pick up on whale and dolphin “signs” other than seeing the animals themselves out of the water. These signs include blows, splashing, dorsal fins at the surface of the water, or the presence of congregating sea birds.
A trained whale observer, like a seasoned birder, is able to pick out distinguishing characteristics from a distance, including the shape and size of the “blows”. Each species has a distinctive blow due to differences in blowhole (nostril) placement, number of blowholes, and the amount of time the whale can go between blows.
Direction and shape of blows of the main whale species.
Source: Alan N. Baker, Whales and dolphins of New Zealand and Australia: an identification guide. Wellington: Victoria University Press, 1999, pp. 42–43
Personal Log
It was a terrific two days for the research team. We had a record number of sightings, including my first whale sighting on the “Big Eyes”! It was really exciting to be the first person on a whale sighting event. I first noticed it’s “blow” which led to me seeing others. I guess I now understand the phrase, “Thar she blows” through firsthand experience!
We had a full moon on April 29th, and we also crossed the International Dateline. We should have watched the movie “Groundhog Day” last night on board the ship!
I had fun helping out with dinner, and made Vietnamese salad with Doc and helped Jay and Randy with the mashed potatoes. Randy also made his most famous cheese and dill biscuits, which are heavenly!
Jay, steward and cook aboard the Sette and Karen making mashed potatoes for dinner.Cook Randy’s glorious cheese and herb biscuits!
In acoustics, we have been monitoring the vocalizations of several cetaceans that we have not seen through visual observations. Amanda, one of our acousticians (I never heard of this profession before – it means acoustics specialist!) has also been monitoring minke whale boings. This is her interpretation of what we could be hearing:
Question of the Day: If it is Thursday on the east side of the International Date Line what day is it on the west side?
What is the International Dateline?
The International Date Line is the imaginary line on the Earth that separates two consecutive calendar days. The date in the Eastern hemisphere, to the left of the line, is always one day ahead of the date in the Western hemisphere. The dateline has been recognized as a matter of convenience and has no force in international law.
Without the International Date Line travelers going westward would discover that when they returned home, one day more than they thought had passed, even though they had kept careful tally of the days. This first happened to Magellan’s crew after their circumnavigation of the world. A person traveling eastward would find that one fewer days had elapsed than recorded, which is what happened to Phineas Fogg in “Around the World in Eighty Days” by Jules Verne (which allowed Fogg to win his bet when he thought he had lost!).
In celebration of crossing the dateline, the Sette crew launched expired signal flares as a “safety exercise”! I had similar signal flares before when I had a boat, but have never used them before! The crew let me light one off. Pretty exciting!
Sette Officer Mike Marino showing how to set off the trigger for the signal flare.
New Term/Phrase/Word of the Day: Blow
A blow is a visible cloud of warm, moist air expelled from a whale’s lungs as it surfaces. It can appear low and bushy, or tall and columnar, depending on the species. Blows are used as a feature in identifying cetaceans in the field.
The blowhole is really a nostril, or respiratory opening of a cetacean. Odontocetes, toothed whales have one blowhole, and mysticetes, the baleen whales have two.
Did you know that:
Sperm whales form stable, long-term groups made up of females which form the core of sperm whale society. These groups consist of about a dozen adult females accompanied by their female and young male offspring. Males about six years or older leave their mother’s group to join all-male bachelor groups called “bachelor schools”. As the male sperm whales become older, they leave the bachelor group and essentially become solitary during their prime breeding years and in old age. Matriarchy is common among whale societies.
Animals Seen Today:
Sooty tern
White-tailed tropic bird
Red-footed albatross
Melon headed whales
Sperm whales
Animals Heard Today:
Sperm whales
Melon headed whales
Minke whales
Full moon from the Sette at daybreak, the day we crossed the international dateline.
NOAA Teacher at Sea: Karen Matsumoto Onboard NOAA Ship Oscar Elton Sette April 19 – May 4, 2010
NOAA Ship: Oscar Elton Sette Mission: Transit/Acoustic Cetacean Survey Geographical Area: North Pacific Ocean; transit from Guam to Oahu, Hawaii, including Wake Is. Date: Friday, April 25, 2010
Science and Technology Log
The Oscar Elton Sette is making its way to Wake Island, and we hope to be there by tonight. One of the research operations is to recover a HARP (High-frequency Acoustic Recording Package) that is in place on Wake Island and replace it with a new HARP unit.
This morning, I was on “CTD duty” at 4:30 a.m. A CTD (conductivity-temperature-depth) station is deployed prior to the start of the visual survey effort, right at sunrise. The CTD data is collected using the ship’s SeaBird CTD shown below. The CTD is deployed to a depth of 1000 meters (depending on depth where we are) with a descent rate of about 30 meters per minute for the first 100 meters of the cast, then at 60 meters per minute after that. It takes three people, plus a winch driver to deploy the CTD, as well as the expert operation from the bridge to keep the ship steady and in one place during the entire operation!
Checking the CTD unit prior to launch.Launching the CTD unit.
Background on CTDs
The CTD is a device that can reach 1,000 meters or more in depth, taking up to five water samples at different depths, and making other measurements on a continuous basis during its descent and ascent. Temperature and pressure are measured directly. Salinity is measured indirectly by measuring the conductivity of water to electricity.
Chlorophyll, a green photosynthetic pigment, is measured indirectly by a fluorometer that emits purple light and measures fluorescence in response to that light. These measurements are made continuously, providing a profile of temperature, salinity, and chlorophyll as a function of depth. The CTD unit is torpedo-shaped and is part of a larger metal water sampling array known as a rosette. Multiple water sampling bottles are often attached to the rosette to collect water at different depths. Information is sent back to the ship along a wire while the instrument is lowered to the depth specified by the scientist and then brought back to the surface.
Monitoring the CTD in the ship’s E-lab.Data gathered from the CTD during its descent.
By analyzing information about the water’s physical parameters, scientists can make inferences about the occurrence of certain biological processes, such as the growth of algae. Knowledge like this can, in turn, lead scientists to a better understanding of such factors as species distribution and abundance in particular areas of the ocean.
I am continuing my acoustic work with the sonobuoys. Today I heard a Minke whale BOING! Below is what a Minke whale boing looks like on the computer. It sounds very much like someone blowing a low tonal whistle or a cell phone vibrating on the desk!
To hear an Atlantic minke whale call (which is different from those found here in the North Pacific, but really cool!) go to this website:
I am making so many great friends among the Sette crew and the science team! I am getting spoiled from all the fantastic meals put together by Randy our cook, and no one ever wants to miss a meal! Our wonderful Doc Tran makes incredible Vietnamese dishes and delicious desserts. Today we had cream puffs for dinnertime dessert! Who would have ever guessed!
Marie Hill, our Chief Scientist and fearless leader was awarded the prestigious NOAA Team Member Award! We surprised her with balloons and decorations in her cabin, and Doc Tran and Lisa made a yummy cake in celebration! Congratulations Marie!!!
Marie Hill, Chief Scientist finding her cabin wildly decorated to congratulate her on her award.
We had a visitor today on the flying bridge-an exhausted juvenile red-footed booby! He sat on the mast, finding a place to rest in the middle of the ocean! It felt great to feel the warm wind hit my face and watch the sapphire blue water crash against the bow of the ship! What a great feeling!
Juvenile red-footed booby on the bridgeDeep blue Pacific ocean water!
Question of the Day: How can you figure out how much food to bring on a 2-week cruise? How do you keep the food fresh? What do you do with leftovers?
This is the situation that the Chief steward has to deal with on every cruise! How would you figure this out? Can you do the math?
New Term/Phrase/Word of the Day: Beaufort Sea State is an empirical measure for describing wind speed based mainly on observed sea conditions. It is also called the Beaufort Wind Force Scale. We stop conducting our visual observations when wind/sea conditions reach Beaufort 7, as wind and sea conditions are too rough to accurately make observations (and its windy out there!).
Something to Think About:
This part of the North Pacific is often described as an ocean desert. We have not seen any whales, and have had only a couple sightings of dolphins since we left Guam. We have also seen migrating sea birds, but not in huge numbers. What do you think may account for the lack of sea life in this expanse of tropical waters?
Animals Seen Today:
Sooty tern
Red-footed booby (juvenile)
Did you know?
That the team of whale visual observers never discuss the numbers of animals they see among themselves. Some people consistently count high, others count low, others are spot on! By not discussing how many animals they observed, they don’t influence each others’ observations. Back at the lab, researchers compare each observer’s counts from their written observations, and can tell which observers tend to under or overestimate numbers of animals they see. They can then make adjustments to total numbers based on everyone’s observations! This is similar to calibrating thermometers or other scientific equipment!
