Scratching the Surface

By Dr. Leigh Torres, Assistant Professor, Oregon State University, Geospatial Ecology of Marine Megafauna Lab

I have been reminded of a lesson I learned long ago: Never turn your back on the sea – it’s always changing.

The blue whales weren’t where they were last time. I wrongly assumed oceanographic patterns would be similar to our last time out in 2014 and that the whales would be in the same area. But the ocean is dynamic – ever changing. I knew this. And I know it better now.

Below (Fig. 1) are two satellite images of sea surface temperature (SST) within the South Taranaki Bight and west coast region of New Zealand that we surveyed in Jan-Feb 2014 and again recently during Jan-Feb 2016. The plot on the left describes ocean surface conditions in 2014 and illustrates how SST primarily ranged between 15 and 18 ⁰C. By comparison, the panel on the right depicts the sea surface conditions we just encountered during the 2016 field season, and a huge difference is apparent: this year SST ranged between 18 and 23 ⁰C, barely overlapping with the 2014 field season conditions.

Figure 1. A comparison of satellite images of sea surface temperature (SST) in the South Taranaki Bight region of New Zealand between late January 2014 and early February 2016. The white circles on each image denote where the majority of blue whales were encountered during each field season.
Figure 1. A comparison of satellite images of sea surface temperature (SST) in the South Taranaki Bight region of New Zealand between late January 2014 and early February 2016. The white circles on each image denote where the majority of blue whales were encountered during each field season.

While whales can live in a wide range of water temperatures, their prey is much pickier. Krill, tiny zooplankton that blue whales seek and devour in large quantities, tend to aggregate in pockets of nutrient-rich, cool water in this region of New Zealand. During the 2014 field season, we encountered most blue whales in an area where SST was about 15 ⁰C (within the white circle in the left panel of Fig. 1). This year, there was no cool water anywhere and we mainly found the whales off the west coast of Kahurangi shoals in about 21 ⁰C water (within the white circle in the right panel of Fig. 1. NB: the cooler water in the Cook Strait in the southeast region of the right panel is a different water mass than preferred by blue whales and does not contain their prey.)

The hot water we found this year across the survey region can likely be attributed, at least in part, to the El Niño conditions that are occurring across the Pacific Ocean currently. El Niño has brought unusually settled conditions to New Zealand this summer, which means relatively few high wind events that normally churn up the ocean and mix the cool, nutrient rich deep water with the hot surface layer water. These are ideal conditions for Kiwi sun-bathers, but the ocean remains highly stratified with a stable layer of hot water on top. However, this stratification does not necessarily mean the ocean is un-productive – it only means that the SST satellite images are virtually useless for helping us to find whales this year.

Although SST data can be informative about ocean conditions, it only reflects what is happening in the thin, top slice of the ocean. Sub-surface conditions can be very different. Ocean conditions during our two survey periods in 2014 and 2016 could be more similar when compared underwater than when viewed from above. This is why sub-surface sensors and data collection is critical to marine studies. Ocean conditions in 2014 and 2016 could both potentially provide good habitat for the whales. In fact, where and when we encountered whales during both 2014 and 2016 we also detected high densities of krill through hydro-acoustics (Fig. 2). However, in 2014 we observed many surface swarms of krill that we rarely saw this recent field season, which could be due to elevated SST. But, we did capture cool drone footage this year of a brief sub-surface foraging event:

An overhead look of a blue whale foraging event as the animal approaches the surface. Note how the distended ventral (throat) grooves of the buccal cavity (mouth) are visible. This is a big gulp of prey (krill) and water. The video was captured using a DJI Phantom 3 drone in the South Taranaki Bight of New Zealand in on February 2, 2016 under a research permit from the New Zealand Department of Conservation (DOC) permit # 45780-MAR issued to Oregon State University.

Figure 2. An echo-sounder image of dense krill patches at 50-80 m depth captured through hydroacoustics in the South Taranaki Bight region of New Zealand.
Figure 2. An echo-sounder image of dense krill patches at 50-80 m depth captured through hydroacoustics in the South Taranaki Bight region of New Zealand.

Below are SST anomaly plots of January 2014 and January 2016 (Fig. 3). These anomaly plots show how different the SST was compared to the long-term average SST across the New Zealand region. As you can see, in 2014 (left panel) SST conditions in our study area were ~1 ⁰C below average, while in 2016 (right panel) SST conditions were ~1 ⁰C above average. So, what are normal conditions? What can we expect next year when we come back to survey again for blue whales across this region? These are challenging questions and illustrate why marine ecology studies like this one must be conducted over many years. One year is just a snap shot in the lifetime of the oceans.

Figure 3. Comparison of sea surface temperature (SST) anomaly plots of the New Zealand region between January 2014 (left) and January 2016 (right). The white box in both plots denotes the general location of our blue whale study region. (Apologies for the different formats of these plots - the underlying data is directly comparable.)
Figure 3. Comparison of sea surface temperature (SST) anomaly plots of the New Zealand region between January 2014 (left) and January 2016 (right). The white box in both plots denotes the general location of our blue whale study region. (Apologies for the different formats of these plots – the underlying data is directly comparable.)

Like all marine megafauna, blue whales move far and fast to adjust their distribution patterns according to ocean conditions. So, I can’t tell you what the ocean will be like in January 2017 or where the whales will be, but as we continue to study this marine ecosystem and its inhabitants our understanding of ocean patterns and whale ecology will improve. With every year of new data we will be able to better predict ocean and blue whale distribution patterns, providing managers with the tools they need to protect our marine environment. For now, we are just beginning to scratch the (sea) surface.

 

 

 

Biopsy sampling blue whales in New Zealand

By: Callum Lilley

Senior Ranger, Marine – Department of Conservation, Taranaki, New Zealand

During the end of January, I had the privilege to be part of the research team studying blue whales in the South Taranaki Bight, New Zealand.  My role, along with assisting with visual survey, was to obtain biopsy samples from whales using a Paxarm modified veterinary rifle.   This device fires a plastic dart fitted with a sterilized metal tip that takes a small skin and blubber sample for genetic and stable isotope analysis. This process is very carefully managed following procedures to ensure that the whales are not put under any undue stress.  Biopsy sampling provides a gold mine of genetic and dietary information to help us understand the dynamics of this whale population.

Although firing a dart at a creature that is considerably larger than a city bus sounds reasonably easy, it is rarely the case.  The first challenge is to find whales within a large expanse of ocean.  The team then needs to photograph the side of each animal and take note of any distinctive features so that each individual is only sampled once.  Sometimes other work will be undertaken (such as collecting fecal samples, or deploying a drifting hydrophone or unmanned aerial system/drone).  Finally the team will attempt to get close enough to the whales, while taking care not to unduly disturb them, to get a biopsy sample.  Wind, vessel movement, glare, the length of time whales spend underwater and the small target they sometimes present above the water are further challenges.

The video below shows a successful biopsy attempt.  It is a well-coordinated team effort that relies on great communication. You can hear observer Todd Chandler direct the skipper of the vessel Ikatere into position while keeping me (the biopsy sampler) informed as to which whale is surfacing and where.  From the vantage point of the flying bridge, Todd can see the whales’ position and movement (my view is limited from the lower deck).  Todd points out where the whale is surfacing and it momentarily presents a target.  This was the second sample from the two racing whales previously discussed by Dr. Torres, so it will be interesting to see their relationship to one-another.

The ideal angle to approach a whale to take a biopsy sample is from behind at a 45 degree angle, as this causes the least disturbance.  The following video was taken from an unmanned aerial system.  It shows the vessel Ikatere approaching from the whale’s left flank. Department of Conservation (DOC) biodiversity ranger Mike Ogle is on the bow of the vessel and fires a biopsy dart at the whale.  After the biopsy is taken the vessel maneuvers to collect the dart/sample from the water while the whale continues to travel.

In addition to blue whale samples, the DOC permit issued to Oregon State University also allowed for opportunistic sampling of other whales.  The following video was taken during an encounter with a large pod of pilot whales.  The video shows how the lightweight dart bounces off the animal and floats in the water.  Care is taken to communicate its location to the skipper who positions the vessel so it can be retrieved with a net.

Once samples have been retrieved they are handled very carefully to prevent contamination.  The sample is split, with some preserved for genetic analysis and the rest for stable isotope analysis.  Analysis of genetic samples provides information on sex, abundance (through genetic capture-recapture, which is calculated by analyzing the proportion of individuals repeatedly sampled over subsequent seasons), and relationships to other blue whale populations.  Stable isotope analysis provides information on diet.  Also, a portion of all samples will be stored for potential future opportunities such as hormone and fatty acid analysis. It blows me away how much information can be gleaned from these tiny samples!

 

Eavesdropping on blue whales in New Zealand

 

Kristin Brooke Hodge

Research Analyst, Bioacoustics Research Program, Cornell University

https://www.researchgate.net/profile/Kristin_Hodge

Over the past few weeks, we have surveyed the South Taranaki Bight, New Zealand, collecting biological and oceanographic data to learn more about the population of blue whales in this region.  Our efforts have been successful: we have encountered multiple blue whales, and recorded information about their identification, behavior, and habitat.  While our visual survey efforts have provided us with an invaluable dataset, our field season is shortly coming to an end.  So how can we continue to learn more about the blue whale population, if we cannot collect visual survey data?

Solution: we will study the sounds they make.

Bioacoustics is a non-invasive method to study acoustically-active animal populations in terrestrial and marine habitats.  Scientists can eavesdrop on animals by recording and analyzing their sounds, and in turn gain insights about their occurrence, behavior, and movement patterns.   This is especially useful for studying elusive or rare species, such as the blue whale, that can be difficult to find in the field.  Since blue whales produce high intensity, infrasonic calls and songs that can travel for many miles across ocean basins, we can capture information regarding their spatial and temporal occurrence, even if we cannot see them. (To listen to a blue whale call recorded off of Chile click here.)

We are using Marine Autonomous Recording Units (MARUs), developed by the Cornell Bioacoustics Research Program, to record blue whales (Fig. 1).  The MARU is a digital audio recording system contained in a buoyant sphere, which is deployed on the bottom of the ocean using an anchor.  Each MARU has a hydrophone that collects acoustic data, and these sounds are recorded and stored on electronic storage media inside the MARU.  The MARUs are programmed to record continuous, low-frequency sounds for approximately six months, after which they pop up to the surface of the ocean, ready to be retrieved for data analysis and redeployed with fresh batteries and storage media.

Figure 1. Kristin Hodge about to deploy a Marine Autonomous Recording Unit (MARU) and anchors in the South Taranaki Bight of New Zealand.
Figure 1. Kristin Hodge about to deploy a Marine Autonomous Recording Unit (MARU) and anchors in the South Taranaki Bight of New Zealand.

Over the course of this field season, we strategically deployed five MARUs across the South Taranaki Bight (Fig. 2), and we will record acoustic data in these five sites over the next couple of years.  This will allow us to understand patterns of occurrence at larger spatial and temporal scales than we can accomplish with visual survey alone.  Our acoustic dataset will complement the biological and oceanographic data we collected on survey, providing a more complete picture of the blue whale population in the bight.

Figure 2. Approximate locations of Marine Autonomous Recording Unit (MARU) deployment sites across the South Taranaki Bight of New Zealand.
Figure 2. Approximate locations of Marine Autonomous Recording Unit (MARU) deployment sites across the South Taranaki Bight of New Zealand.

To see us deploy a MARU in New Zealand, check out this video:

 

Racing blues

By Dr. Leigh Torres, Assistant Professor, Oregon State University, Geospatial Ecology of Marine Megafauna Lab

A week ago we observed two racing blue whales.

Please read my blog about this amazing sighting that was recently posted on The National Geographic Explores webpage. You can also watch these videos:

 

Marine Megafauna Ecology Fund

 

Blues Clues

Although blue whales are big, the South Taranaki Bight is bigger. So finding them is not straight forward. In fact, with little prior research in this area, the main focus of our project is to gain a better understanding of blue whale distribution patterns in the region. So, while bouncing around on the sea, we are collecting habitat data that we relate to whale occurrence data to learn what makes preferred whale habitat.

We conduct CTD casts. CTD stands for Conductivity, Temperature and Depth. This is an instrument we lower down to the bottom of the ocean on a line and along the w ay it records temperature and salinity (conductivity) data at all depths. This data describes the water structure at that location, such as the depth of the thermocline. The ocean is often layered with warm, low-salt water on top, and cooler and salty water at the bottom. This thermocline can act as a boundary above which prey aggregate.

Todd and Andrew deploy the CTD off the R/V Ikatere.
Todd and Andrew deploy the CTD off the R/V Ikatere. (Photo by Callum Lilley)
CTD cast
Example data retrieved from a CTD cast showing how temperature (green line) decreases and salinity (red line) increases as it descends through the water column (depth on y-axis).

We also have a transducer on board that we use to record the presence of biological material in the ocean, like krill (blue whale prey). This transducer emits pings of sound through the water column and the echoes bounce back, either off the seafloor, krill or fish. This glorified echosounder records where blue whale prey is, and is not.

Example display image from our echosounder (EK60) showing patches of prey (likely krill) in the upper surface layer.
Example display image from our echosounder (EK60) showing patches of prey (likely krill) in the upper surface layer.

Additionally, the research vessel is always recording surface temperature (SST). I monitor this SST readout somewhat obsessively while at-sea as well as study the latest SST satellite images. Using these two bits of data as my “blues clues”, we search for blue whales.

After a bumpy ride across the Cook Strait we had a good spell of weather last week. We covered a lot of ground, deploying our 5 hydrophones across the Bight and keeping our eyes peeled for blows. Our first day out we found three whales. Fantastic sightings. But, as we continued to survey through warm, low productivity water we found no signs of blue whales. The third day out was a beauty – the type of day I wish for: low swell and low winds – perfect for whale finding. We covered 220 nautical miles this day (deploying 2 hydrophones) and we searched and searched. But no whales. I could see from the SST satellite image that the whole Bight was really warm: about 20 ⁰C. I could also see a strip of cold water down south, toward Farewell Spit. I said “Let’s go there”.

Sea surface temperature (SST) satellite image of the South Taranaki Bight region in New Zealand that shows mostly warm water with a plume of colder water down south.
Sea surface temperature (SST) satellite image of the South Taranaki Bight region in New Zealand that shows mostly warm water with a plume of colder water down south.

After twelve and a half hours of survey effort through clear, blue, warm water, we finally saw the water temperature drop (to about 18 ⁰C) and the water color turn green. We started to see gannets, petrels, shearwaters, and common dolphins feeding. Then I heard the magic words come from Todd’s mouth: “Blow!” So began our sunset sighting. From 7:30 to 10 pm we worked with four blue whales capturing photographs and biopsy samples, and echosounder prey data.

Diving blue whale in the South Taranaki Bight, NZ (photo by Leigh Torres)
Diving blue whale in the South Taranaki Bight, NZ (photo by Leigh Torres)

This is an example of a species-habitat relationship that marine ecologists like me seek to document. We observe and record patterns like this so that we can better understand and predict the distribution of blue whales. Such information is critical for environmental managers to have in order to effectively regulate where and when human activities that may impact blue whales can occur. Over the next two weeks we will continue to document blue whale habitat in the South Taranaki Bight region of New Zealand.

Blown out.

By Dr. Leigh Torres, Assistant Professor, Oregon State University, Marine Mammal Institute, Geospatial Ecology of Marine Megafauna Lab

Hurry up and wait. Can’t control the weather. All set and nowhere to go.

However you want to say it, despite our best efforts to be ready to sail today, the weather has not agreed with our best-laid plans. It’s blowing 20-30 knots in the South Taranaki Bight, which makes it very difficult to spot a whale from our small (but sturdy) research vessel (NIWA’s R/V Ikatere), and practically impossible to take good photos of the whales or to deploy our hydrophones. So, we wait.

Over the last few days we have been busy tracking down gear, assembling the hydrophones, discussing project logistics, preparing equipment (Fig. 1), provisioning the vessel, getting the crew in place, and practicing vessel operations. We have flown to the other side of the world. We have prepared. We are ready. And we wait. Such is field work. I know this. I’ve been through this many times. But it is always hard to take when you feel the clock ticking on your timeline, the funds flowing from your budget, and your people waiting for action. Fortunately, I have built in contingency time so we will still accomplish our goals. We just have to wait a bit longer. As the Kiwis say, ‘Bugger!’

kristin and hydrophones small
Figure 1. Kristin Brooke Hodge of The Bioacoustics Research Program at Cornell University performs a global sound check on the hydrophones (loud bang of hammer to pipe) so that times can all be synced and any clock drift accounted for.

Below is a wind and rain forecast for New Zealand (provide by the MetService). The box in red is our study region of the South Taranaki Bight. We are currently in Wellington where the green star is, but we want to be in Pohara where the yellow star is – this will be our base during the field project, if we can just get there.

NZ wind

Wind strength and direction in these types of maps is depicted by the wind indicator lines: the wind is coming from the tail toward the flag end of the symbol, and the strength is symbolized by the number and size of the barbs on the flag end.

wind barbs

Notice how inside the red box there are lots of barbs on the indicator lines (most saying about 20 knots), but just to the west and north there are few barbs – about 5 to 10 knots. These are great survey conditions, but not where we want to be! A bit heartbreaking. But that’s how it goes, and I know we will get our weather window soon. Until then, we sit tight and watch the wind blow through the pohutukawas and cabbage trees in beautiful Wellington.

An update from the Antarctic Peninsula

By: Erin Pickett

Yesterday someone said to me, “I don’t know if it was sunrise or sunset, but it was beautiful”. So it goes on the R/V Lawrence M. Gould (LMG), the surrounding scenery is incredible but the work schedule on this research ship makes it difficult to remember what time of day it is.

Here on the Antarctic Peninsula, the sun never really sets and our daily schedules are dependent on things like the diel vertical migration of krill, the current wind speed and the amount of sea ice in between us and our study species, the humpback whale. For these reasons, we sometimes find ourselves starting our workday at odd hours, like 11:45 pm (or 4:00 am). As a reminder, I am currently working on research vessel on a project called the Palmer long term ecological research (LTER) project.  You can read my first blog post about that here. We are about one week into our journey and so far, so good!

Our journey began in Punta Arenas, Chile, where we spent two days loading our research supplies onto the LMG and getting outfitted with cold weather gear. From Punta Arenas we headed south through the straights of Magellan and then across the Drake Passage. Along the way we spotted a variety of cetaceans including minke, fin, sei and humpback whales, and Commerson’s and Peale’s dolphins. I spent as much of our time in transit as I could looking for seabirds, the most numerous being white-chinned and cape petrels, southern giant petrels, and black-browed albatrosses. Spotting either a royal or a wandering albatross was always exciting. An eleven foot wingspan allows these albatross to glide effortlessly above the water and this makes for a beautiful sight!

We have spent the last four days transiting between various sampling stations around Palmer deep, which is an underwater canyon just south of our home base at Palmer station. When conditions allowed, we loaded up our tagging and biopsy gear into a small boat and went to look for humpback whales. We’ve been incredibly successful with the limited amount of time we’ve had on the water and this morning we finished deploying our sixth tag.

We brought a few different types of satellite tags with us to deploy on humpback whales. One type is an implantable satellite tag that transmits location data over a long period of time. These data allow us to gain a better understanding of the large-scale movement and distribution patterns of these animals. The other tag we deploy is a suction cup tag, so called because four small suction cups attach the tag to the whale. These suction cup tags are multi-sensor tags that measure location as well as fine scale underwater movement (e.g. pitch, roll, and heading). They are also equipped with forward and backward facing cameras and most importantly, radio transmitters! This allows us to recover the tags once they fall off the animal and float to the surface (after about 24 hours). The data we get from these tags will allow us to quantify fine-scale foraging behavior in terms of underwater maneuverability, prey type and the frequency, depth and time of day that feeding occurs.

When we deployed each of these tags we also obtained a biopsy sample and fluke photos. Fluke photos and biopsy samples allow us to distinguish between individual animals, and the biopsy samples will also be used to study the demographics of this population through genetic analysis.

Now that we’ve deployed all of our satellite tags and have recovered the suction cup tag just in the nick of time (!), we are starting our first major transect line toward the continental shelf. We will be continuing south along these grid lines for the next week.

My lab mate Logan Pallin and I will be continuing to write about our trip over the next couple of months on another blog we created especially for this project. You can find it here: blogs.oregonstate.edu/LTERcetaceans

I’ll leave you with a few of my favorite photos of the trip so far!

“This is what I would do if I weren’t afraid” – New Zealand blue whale field season 2016

By Dr. Leigh Torres, Assistant Professor, Oregon State University, Geospatial Ecology of Marine Megafauna Lab

Two years ago I documented a blue whale foraging ground in an area of New Zealand called the South Taranaki Bight (STB) – the country’s most industrially active marine area with intense oil and gas exploration and extraction since the 1970’s, elevated vessel traffic, and potential seabed mining (Figure 1). Over just five days of survey effort we observed 50 blue whales and documented foraging behavior. But we still know next to nothing about where and when blue whales are in the STB, how many whales use this area, how important this area is as a feeding area, or to what population the whales belong. Without answers to these questions effective management of human activities in the region to protect the whales and their habitat is unfeasible.

I am now heading back to New Zealand to collect the data needed to answer these questions that will enable successful management. That’s my goal.

Figure 1. Illustration of a space-use conflict between industry activity and blue whales in the South Taranaki Bight, which lies between the north and south islands of New Zealand. Blue whale sightings and strandings recorded between 1970 and 2012.
Figure 1. Illustration of a space-use conflict between industry activity and blue whales in the South Taranaki Bight, which lies between the north and south islands of New Zealand. Blue whale sightings and strandings recorded between 1970 and 2012.

Such research costs money. In collaboration with the Bioacoustic Research Program at Cornell University (birds.cornell.edu/brp), we are deploying five hydrophones to listen for blue whales across the region for 2 years. We will conduct vessel surveys for 1 month in each year to find whales and collect data on their habitat, behavior, and individual occurrence patterns. As far as field research projects go, this work is not very expensive, but we still need to pay for vessel time, equipment, and personnel time to collect and analyze the data. This is an ugly truth of scientific research – it costs money and there is not a lot out there.

For two years I’ve had my fund raising hat on (Not my favorite hat. I much prefer my research hat). I believe that industry groups active in the STB should take an active role in supporting the necessary research. They exploit the natural resources in the region and should therefore take responsibility for ensuring the ecosystem’s sustainability and health. Right? They did not agree.

I emphasized to these groups that by supporting the project they would demonstrate their environmental responsibility and ultimately be engaged in discussions of management options based on project findings. Despite hundreds of emails, phone calls and discussions, all the oil and gas companies, the seabed mining group, and the maritime traffic organization declined to fund the project, claiming lack of funds or lack of relevance to their interests. Meanwhile, other groups who prioritize conservation management are supporting the project. I am grateful to The Aotearoa Foundation, The National Geographic Society Waitt Foundation, The New Zealand Department of Conservation, Greenpeace New Zealand, OceanCare, Kiwis Against Seabed Mining, and an anonymous donor.

Lately I have been reading Sheryl Sandberg’s poignant book, Lean In, which I feel is a call to women to take responsibility for our equality and leadership. Those familiar with this book will recognize the opening of my blog title from her valid push for women to take more risks and push ourselves beyond our comfort zones. In many ways I feel I am doing this now. It would be much easier for me to withdraw from this project, say I tried, and let things carry on until someone else takes the challenge. Funding is short, last minute contract issues abound, equipment logistics are running late, I fear political pushback, and I have a sore throat. But it’s time for this project to happen. It’s time to recognize biodiversity’s innate right to healthy habitat. It’s time for industry groups to acknowledge their potential impacts on blue whales through elevated ocean noise, vessel strikes, and habitat degradation and displacement. It’s time for management to have the tools to act.

Figure 2. A blue whale surfaces in front of an oil rig in the South Taranaki Bight, New Zealand. Photo by Deanna Elvines.
Figure 2. A blue whale surfaces in front of an oil rig in the South Taranaki Bight, New Zealand. Photo by Deanna Elvines.

I remain hopeful that industry groups will engage in this research effort. Through diplomacy, transparency and robust science I want to bring together industry, NGOs, and management groups to develop effective conservation strategies to protect blue whales and their habitat in the STB. Collaboratively we can balance industry activity and biodiversity protection.

Since reading Lean In, I’ve been wondering if the conservation movement suffers because of women’s reluctance to challenge, take risks, and ‘sit at the table’ as Sandberg says. The conservation field is heavily dominated by women. For progress to happen we must be willing to force issues, be perceived as aggressive, and not be nice all the time. Just like men are expected to be.

Over the next four weeks colleagues and I will conduct research in the STB on blue whales. Stay tuned to this blog for updates.

Entering in the world of Photogrammetry

By Leila Lemos, Ph.D. Student, Department of Fisheries and Wildlife, OSU.

 

Hello everybody with the first post of the year from the GEMM Lab!!

The year of 2016 has just begun and with that comes new projects and great expectations about my PhD project.

During this week I am going to learn how to measure gray whales (Eschrichtius robustus) using aerial images that were captured during last summer’s pilot field season along the Oregon Coast led by my advisor Dr. Leigh Torres.

Dr. Torres aimed to test the methodology for our project that will combine these whales’ measurements data with hormonal analysis to assess the overall health of gray whales.

The aerial videos and images were taken through an unmanned aerial system (UAS) that is composed of a flying unit and an on-board camera. An example of this system can be seen below, in Figure 1.

Lt%20recaptures%20drone

Figure 1: Dr. Leigh Torres re-captures the UAS (DJI Phantom 3) while at sea after an over flight of a gray whale.

Source: Leigh Torres, 2015.

 

The measurement of the whales through aerial images is known as “photogrammetry” and this method can give us important information about the whales through this unique overhead perspective, such as individual identification using natural markings, sex and reproductive condition based on size estimation, and individual-based changes in growth, health and body condition (nutritive condition) over time through replicate samples.

Perryman and Lynn (2002) used images captured from planes and adopted four different measurements for each photographed whale: the total length (Lt), the width of the whale at its widest point (Wm), the distance from the tip of the rostrum to the widest point (RWm), and the width of the flukes (Fw), as shown in the Figure 2. Using these methods, this study was able to identify pregnant females and found that southbound migrating gray whales were significantly wider than northbound whales.

Captura de Tela 2016-01-08 às 4.49.47 PM

Figure 2: Features measured on vertical photographs in gray whales

Source: Perryman and Lynn, 2002.

 

We plan to build upon this established method by measuring width at multiple points along the whale’s body, in addition to the total length.

Images taken of the same individuals during different temporal periods can reveal variations in their body condition.

We aim to collect images of the same individuals at the beginning and end of a foraging season and hypothesize that due to weight gain and increased blubber mass the width of animals will increase. Additionally, when images of indiviudals are compared between years we hypothesize that body condition changes due to major events such as pregnancy, entanglements, skin lesions, and predation events, will be linked to changes in body condition.

We will relate these photogrammetry data to hormonal data on stress and reproductive status in order to describe individual stress variation as it relates to size, health, location, year, reproductive status and ocean noise levels.

During the pilot field season, six gray whale fecal samples were collected and hormonal levels in these samples were analyzed showing positive results. Based on the success of the pilot field season, I believe my PhD project will produce exciting and informative data about gray whale ecology by linking physiology and morphometrics.

I am excited to begin my thesis research and, until my field season starts next summer, you can find me measuring gray whales!

To illustrate, below are a few aerial images taken of gray whales off Newport, Oregon, using a UAS, which we will use to conduct photogrammetry (all photos taken under NMFS permit 16111 issued to John Calambokidis).

Captura de Tela 2016-01-03 às 1.29.00 PM Captura de Tela 2016-01-03 às 1.28.43 PM Captura de Tela 2016-01-03 às 1.28.25 PM

And, just for fun, here is a UAS clip of a foraging gray whale in a kelp bed off the coast of Oregon to give a sense of the unique perspective we can get on animal behavior.

* Taken under NMFS permit 16111 issued to John Calambokidis.

This research is facilitated through the collaboration with OSU’s Aerial Imaging Systems Lab (http://ais.forestry.oregonstate.edu/), and Cascadia Research Collective (http://www.cascadiaresearch.org/).

Until next time and thanks for reading!

 

Bibliographic Reference:

Perryman WL, Lynn MS. 2002. Evaluation of nutritive condition and reproductive status of migrating gray whales (Eschrichtius robustus) based on analysis of photogrammetric data. J. Cetacean Res. Manage. 4(2):155-164.

Behind the scenes of modeling

By Olivia Hamilton, PhD Candidate, Institute of Marine Science,

University of Auckland

I am going to take you behind the scenes of modeling. No, I do not mean the kind of modeling where six-foot tall glamazons such as Cindy Crawford get paid exorbitant amounts of money to dress up in fabulous outfits, strike a pose, and attend A-list parties. I am talking about statistical modeling. This usually involves wearing sweatpants, sitting at your computer for extended periods of time, and occasionally turning to a block of chocolate for comfort.

Species distribution models (SDM), also known as habitat models, are a powerful tool for informing conservation and management of animal populations. They essentially enable us to identify important areas of habitat by describing the relationship between the spatial distribution pattern of a species and the attributes of their physical environment. It is logistically difficult to observe top marine predators such as whales, dolphins, sharks, and seabirds. This difficulty is because a) they move, and b) we only get to observe them during the small portion of their lives that they spend near or at the surface of the water. Environmental variables such as water depth and slope do not necessarily influence the habitat use patterns of top predators directly, but we can use them in our models as proxies for more important ecological determinants of habitat use that are more difficult to collect data for, such as the distribution of their prey.

Some SDM take this a step further by enabling us to make predictions about a species’ distribution in areas or time periods that we did not survey. This predictive capacity can provide us with a more holistic understanding of their how animals use their range, and the ability to anticipate distribution patterns under variable conditions (think climate change 100 years from now).

The idea of understanding how sharks, dolphins, whales, and seabirds are using the Hauraki Gulf in New Zealand is an extremely exciting prospect for a nosy biologist like me. I have always had a fascination with mega-fauna, and more specifically with large predators. To me, uncovering the reasons that drive their habitat use patterns is the equivalent to finding a pearl in an oyster. However, that’s just me being selfish. The best thing about creating predictive habitat models for mega-fauna in the Gulf is that we will gain a better understanding of how to manage and protect them. The SDM that I am using are called Boosted Regression Trees (BRT). They are a relatively new kid on the habitat modeling block, but are recognized as a powerful tool for making habitat predictions with. Dream result.

My Master’s thesis had a focus on abundance estimates and social structure analyses; everything I have learned about habitat modelling while in the GEMM Lab at Oregon State University was from scratch. One of the largest lessons that I learned was how much behind the scenes preparation is needed before you can even get to the actual modeling point. The length of the preparation stage is proportional to the size of the dataset. Needless to say, the years’ worth of multi-species aerial survey data that I have collected has kept me quite busy.

The first step was to create pseudo-absences.

Pseudo-what you say?

When we are out on the water, or in the plane, and we see animals of interest, we record their geographic location. As a result, our presence sightings are represented as points in space. However, in order to identify areas of preferred habitat we need to also describe the range of environmental conditions that are available to the population. To do this, we also need to obtain environmental data from where animals were not seen, otherwise known as absence data. As I mentioned earlier, observing marine animals is difficult. This makes it difficult to obtain confirmed absence data. Luckily, some savvy scientists came up with the idea of creating pseudo-absences. The idea is to basically use the area in which sightings were not made to generate randomly placed absence points.

As simple as that?

Of course not.

When generating pseudo-absences, we want to make sure that they are placed in areas that reflect true absences. Poor environmental conditions affect our ability to detect animals, especially when travelling along at 160km/h at 500ft in a small plane. After making some exploratory plots of the various environmental conditions relative to sighting frequencies, we identified what conditions hindered our ability to see animals (Fig. 1 & 2). Stretches of the track that we flew in poor conditions were then removed before generating the pseudo-absences.

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Fig. 1. Example of exploratory plots looking at the relationship between detection rates and the amount of glare coverage within our viewing area. Fig. 2. shows that very few detections of common dolphins were made when the glare coverage exceeded 60% and 3 shows that detection rates for gannets were acceptable up to 80% glare coverage. Any stretches of a particular survey that exceeded these values were excluded before pseudo-absences were generated.

The next step was to decide where to place the pseudo-absences along the track-lines. To do this, we used all sightings data for each species to create density plots (Fig. 2), and then distributed our pseudo-absences in an inverse proportion to their density (Fig. 3). That way, we were distributing a higher number of absences in areas of known lower density, and therefore obtaining a representative sample of environmental variables in areas that reflected true absences.olivia2Fig. 2: Density plot of all common dolphin sightings over 22 aerial surveys in the Hauraki Gulf. Red represents the highest density and blue represents the lowest density.

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Fig. 3:  Aerial track-lines flown in the Hauraki Gulf, New Zealand on 19 March 2014. Triangle symbols represent pseudo-absences and black circles represent presence sightings for that day.

Next what?

Step two involved creating environmental layers that would be included as predictor variables in our models. Instead of chucking any old variable in there, we needed to decide what physical or biological features of the environment would be ecologically relevant for explaining the different species distributions. For example, one of the variables we are using is tidal height/flow. Tidal movement pushes around potential food for marine animals and therefore influences how they use their space.  Some others environmental variables included in our models were proximity to potential prey patches (zooplankton and fish), sea surface temperature, and the type of substrate (sand, mud, gravel).

Finally, we are ready for the main event. Ladies and gentlemen, I introduce to you preliminary results for one of my study species, the Nationally Endangered Bryde’s whale (Fig. 4). These plots show us the relative influence of each the environmental variables on the distribution of Bryde’s whales in the Hauraki Gulf. The percentage value associated with each of the plots tells us how much influence each variable had in the model. We can see that the time of the year (month), the distribution of food (zooplankton and fish), and the difference in water temperature over the year have the most influence on the distribution of Bryde’s whales. This makes complete ecological sense. Prey distribution is one of the main ecological drivers of the distribution of predators both in time and space. Temperature is one of the main drivers for the distribution of prey species. As the water temperature changes throughout the year within the Gulf, so does the availability of the Bryde’s whales prey items. In turn, this influences how much time they spend in the Gulf. When prey is around, the Bryde’s whales are never far away. Eating is a very important part of the day for these 90,000 lbs whales; therefore it pays to stay close to their food supply.

Olivia4Fig. 4: Relative influence of environmental predictors on the distribution of Bryde’s whales within the Hauraki Gulf, New Zealand.

The show is not over yet, folks. While the code is all running smoothly, there is still a bit of fine-tuning to do. I am currently working on this, re-running these models over and over, trying to iron out the creases. At the moment, I am creating SDMs for four of my study species: Bryde’s whales, common dolphins, bronze whaler sharks, and gannets. Once we are satisfied with how things are running, I will start stage two of the modeling process: the prediction maps.

Next year, we will conduct several more aerial surveys in the Hauraki Gulf with the aim of validating our habitat models.

How is that for a cliffhanger?

Stay tuned to gain an insight into the habitat use of mega-fauna in the Hauraki Gulf, New Zealand.