The seamounts are calling and I must go: a humpback’s landscape

Solène Derville, Entropie Lab, Institute of Research for Development, Nouméa, New Caledonia (Ph.D. student under the co-supervision of Dr. Leigh Torres)

The deep ocean is awe-inspiring: vast, mysterious, and complex… I can find many adjectives to describe it, yet the immensity of it prevents me from picturing it in my mind. Landscapes are easy to imagine because we see them all the time, but their hidden ocean counterparts of seascapes with several kilometer-high seamounts and abyssal trenches are hard to visualize.

When I started a PhD on the spatial ecology of humpback whales, a species typically known for its coastal distributions, I never imagined my research would lead me to seamounts. Lesson of the day: you never know where research will lead you… So here is how it happened.

About twenty years ago when my supervisor, Dr Claire Garrigue, started working on humpback whales in New Caledonia, she was told by fishermen that humpbacks were often observed in prime fishing locations, about 170 km south of the mainland. After a little more investigation into this claim, it was discovered that these fishing spots corresponded with two seafloor topographic features: the Antigonia seamount and Torch Bank (Fig. 1), These features rise from the seafloor to depths of 30 m and 60 m respectively and are surrounded by waters about 1500 m deep. This led Dr. Garrigue to implement an ARGOS-satellite tagging program to follow the movements of humpbacks leaving the South Lagoon (one of the main breeding area in New Caledonia, Fig. 1). Sure enough, most of the tagged whales (61%) visited the Antigonia seamount (Fig. 2; Garrigue et al. 2015)⁠.

Map of New Caledonia and our study areas: the South Lagoon and the Southern Seamounts. Light grey lines represent 200m isobaths. Land is shown in black and reefs in grey.
Figure 1: Map of New Caledonia and our study areas: the South Lagoon and the “Southern Seamounts”. Light grey lines represent 200m isobaths. Land is shown in black and reefs in grey.
Figure 2: ARGOS tracking of 34 humpback whales tagged between 2007 and 2012 in the South Lagoon. The Antigonia seamount and Torch Bank are completely covered by tracklines.
Figure 2: ARGOS tracking of 34 humpback whales tagged between 2007 and 2012 in the South Lagoon. The Antigonia seamount and Torch Bank are completely covered by tracklines.

 

Seamounts are defined as “undersea mountains rising at least 100m from the ocean seafloor” (Staudigel et al. 2010). Most of them have a volcanic origin and the majority of them are located in the Pacific Ocean (Wessel 2001). But what is the link between these structures and marine life? The physical and biological mechanisms by which seamounts attract marine wildlife are diverse (for a review see: Pitcher et al. 2008)⁠. In a nutshell, topography of the ocean floor influences water circulation and isolated seabed features such as seamounts affect vertical mixing and create turbulences, consequently resulting in higher productivity.

For instance, have you ever heard of internal waves? Contrary to the surface waves people play in at the beach, internal waves propagate in three dimensions within the water column and can reach heights superior to a 100m! When these waves encounter steep topography, they break, similar to what a “normal” wave would do when reaching shore. This creates complex turbulence, which in turn may attract megafauna such as cetaceans (see com. by Hans van Haren).

The importance of seamounts for cetaceans is often referenced in the literature, however, few studies have tried to quantify this preference (one of which was recently published by our labmate Courtney Hann, see Hann et al. 2016 for details). So what importance do these seamounts serve for humpback whales in New Caledonia? Are they breeding grounds, do they serve as a navigation cue, a resting area, or even a foraging spot (the latter being the less likely hypothesis given that humpback whales have never been observed feeding in tropical waters)?

To answer this question, an expedition to Antigonia was organized in 2008 and about 40 groups of whales were observed in only 7 days! The density of this aggregation, the high occurrence of groups with calves and the consistent singing of males suggested that this area may be associated with breeding or calving behavior. Several other missions followed, confirming the importance of this offshore habitat for humpbacks.

Looking through all this data I was struck by two things: 1) whales were densely aggregated on top of these seamounts but were rarely found in the surrounding area (Fig. 3), and 2) other seamounts with similar characteristics are only a few kilometers from Antigonia, but seem to be rarely visited by tagged whales.

What is so special about these seamounts? Why would energetically depleted females with calves choose to aggregate in these off-shore, densely occupied and unsheltered waters?

 

Figure 3: 3D surface plot of the seabed in the Southern seamount area. Humpback whale groups observed in-situ during the boat-based surveys conducted between 2001 and 2011 are projected at the surface of the seabed: blue points represent groups without calf and white points represent groups with calf. Antigonia and Torch Bank have a clear flat-top shaped which classifies them in the “guyot” seamount type. Most whale groups aggregated on top of these guyots.
Figure 3: 3D surface plot of the seabed in the Southern Seamounts area. Humpback whale groups observed during the boat-based surveys (2001-2011) are projected at the surface of the seabed: blue points represent groups without calf and white points represent groups with calf. Antigonia and Torch Bank have a clear flat-top shaped and are called “guyots” seamounts. Most whale groups aggregated on top of these guyots. For 3D interactive plot: click here.

I will spend the next two months at the GEMM lab in Newport, OR, trying to answer these questions using ocean models developed by New Caledonian local research teams (at IRD and Ifremer). I will be comparing maps of local currents and topography of several seabed features located south of the New Caledonia main island. The oceanographic model used for this study will allow me to analyze a great number of environmental variables (temperature, salinity, vertical mixing, vorticity etc.) through the water column (one layer every 10m, from 0 to 500m deep) and at a very fine spatio-temporal scale (1km and 1day, even 1 hour at specific discrete locations) to better understand humpback whale habitat preferences.

Figure 4: Modeled Sea Surface Temperature for July 15th 2013 (model in progress, based on MARS3D, development by Romain Legendre). A temperature front occurs in the middle of the study area, along the Norfolk ridge. On this image, a cold eddy is forming right on top of the Antigonia seamount.
Figure 4: Modeled Sea Surface Temperature for July 15th 2013 (model in progress, based on MARS3D, development by Romain Le Gendre). A temperature front occurs in the middle of the study area, along the Norfolk ridge. On this image, a cold eddy is forming right on top of the Antigonia seamount.

 

Looking forward to uncovering the mysteries of seamounts and sharing the results in December!

Literature Cited

Garrigue C, Clapham PJ, Geyer Y, Kennedy AS, Zerbini AN (2015) Satellite tracking reveals novel migratory patterns and the importance of seamounts for endangered South Pacific Humpback Whales. R Soc Open Sci

Hann CH, Smith TD, Torres LG (2016) A sperm whale’s perspective: The importance of seasonality and seamount depth. Mar Mammal Sci:1–12

Pitcher TJ, Morato T, Hart PJ, Clark MR, Haggan N, Santos RS (2008) Seamounts: ecology, fisheries & conservation. Oxford, UK: Blackwell Publishing Ltd.

Wessel P (2001) Global distribution of seamounts inferred from gridded Geosat/ERS-1 altimetry. J Geophys Res 106:19431–19441

Staudigel H, Koppers AP, Lavelle JW, Pitcer TJ, Shank TM (2010) Defining the word ‘seamount’. Oceanography 23,20–21.

Exciting news for the GEMM Lab: SMM conference and a twitter feed!

By Amanda Holdman (M.S Student)

At the end of the week, the GEMM Lab will be pilling into our fuel efficient Subaru’s and start heading south to San Francisco! The 21st Biennial Conference on the Biology of Marine Mammals, hosted by the Society of Marine Mammalogy, kicks off this weekend and the GEMM Lab is all prepped and ready!

Workshops start on Saturday prior to the conference, and I will be attending the Harbor Porpoise Workshop, where I get to collaborate with several other researchers worldwide who study my favorite cryptic species. After morning introductions, we will have a series of talks, a lunch break, and then head to the Golden Gate Bridge to see the recently returned San Francisco harbor porpoise. Sounds fun right?!? But that’s just day one. A whole week of scientific fun is to be had! So let’s begin with Society’s mission:

smm-2015-logo

‘To promote the global advancement of marine mammal science and contribute to its relevance and impact in education, conservation and management’ 

And the GEMM Lab is all set to do just that! The conference will bring together approximately 2200 top marine mammal scientists and managers to investigate the theme of Marine Mammal Conservation in a Changing World. All GEMM Lab members will be presenting at this year’s conference, accompanied by other researchers from the Marine Mammal Institute, to total 34 researchers representing Oregon State University!

Here is our Lab line-up:

Our leader, Leigh will be starting us off strong with a speed talk on Moving from documentation to protection of a blue whale foraging ground in an industrial area of New Zealand

Tuesday morning I will be presenting a poster on the Spatio-temporal patterns and ecological drivers of harbor porpoises off of the central Oregon coast

Solène follows directly after me on Tuesday to give an oral presentation on the Environmental correlates of nearshore habitat distribution by the critically endangered Maui dolphin.

Florence helps us reconvene Thursday morning with a poster presentation on her work, Assessment of vessel response to foraging gray whales along the Oregon coast to promote sustainable ecotourism. 

And finally, Courtney, the most recent Master of Science, and the first graduate of the GEMM Lab will give an oral presentation to round us out on Citizen Science: Benefits and limitations for marine mammal research and education

However, while I am full of excitement and anticipation for the conference, I do regret to report that you will not be seeing a blog post from us next week. That’s because the GEMM Lab recently created a twitter feed and we will be “live tweeting” our conference experience with all of you! You can follow along the conference by searching #Marman15 and follow our Lab at @GemmLabOSU

Twitter is a great way to communicate our research, exchange ideas and network, and can be a great resource for scientific inspiration.

If you are new to twitter, like the GEMM Lab, or are considering pursuing graduate school, take some time to explore the scientific world of tweeting and following. I did and as it turns out there are tons of resources that are aimed for grad students to help other grad students.

For example:

Tweets by the thesis wisperer team (@thesiswisperer) offer advice and useful tips on writing and other grad related stuff. If you are having problems with statistics, there are lots of specialist groups such as R-package related hashtags like #rstats, or you could follow @Rbloggers and @statsforbios to name a few.

As always, thanks for following along, make sure to find us on twitter so you can follow along with the GEMM Labs scientific endeavors.

 

 

Looking back on a busy field season

Solène Derville, EnTroPie Lab, Institute of Research for Development, Nouméa, New Caledonia (Ph.D. student under the co-supervision of Dr. Leigh Torres)

After one month and a half in the field, I am now comfortably sitting at my desk in the Institute of Research for Development (IRD) in Nouméa and I am finally finding the time to look back on my first marine mammal field experience.

The New Caledonian South Lagoon is certainly not the worst place on earth to study whales. While some people spend hours trying to spot extremely rare and shy species living in freezing cold polar waters, I have to endure a 25°C temperature, turquoise waters and a study species desperate for attention (series of a dozen breaches are not uncommon). As with all field work, there were ups and downs but following humpback whales during the 2015 breeding season was by far the most exhilarating field experience I’ve ever had.

During the austral winter, humpback whales are thought to travel and stay in different areas of the New Caledonian Economic Exclusive Zone. Using satellite telemetry, several seamounts (e.g. Antigonia), banks (e.g. Torche bank) and shallow areas have been shown to play an important role for breeding and migrating humpback whales (Garrigue et al. In Press). However, as much as we would like to study whales in these areas, offshore field missions are logistically and financially hard to conduct. This is why most of the data on humpback whales in New Caledonian waters have been collected in coastal waters, and more specifically in the South Lagoon. Opération Cétacés, a local NGO, has been studying whales in this area for about two decades and I was lucky to participate in this year’s field season with their experienced team.

The South Lagoon of New Caledonia
The South Lagoon of New Caledonia

The usual day in Prony (the village that we live in during the whale season) usually starts early. We get up at about 5:30, and start by engulfing a bowl of porridge (nicknamed “globi” and considered as a highly exotic dish). By 6:30 everyone is standing in our rigid-hulled inflatable boat, listening to the weather forecast on the radio. After a 15 minute trip across the bay of Prony, two people disembark and climb to a land-based lookout, the N’Doua Cape, where they will spend the day trying to spot humpback whales and guiding the boat towards their location via VHF radio communication. The vessel-based team slowly approaches the whale groups to do photo-identification (using the unique marks on the ventral surface of the tail flukes), biopsy collection, and behavioral activity monitoring. The particular coastal geography of this study area (see previous post: Crossing Latitudes) allows us to uniquely combine land-based and boat-based surveying. These methods increase our encounter rate and allow us to collect more individual-based data. Yet, compared to a standardized boat-based surveys, our survey effort is much more complex to estimate and account for in a spatial distribution model.

This season, the number of whale encounters was particularly high. We spent 31 days at sea and observed a total of 99 groups. Using photo-identification, we documented 113 different individuals, some of which were first observed more than 15 years ago! Biopsy samples were collected from 139 different individuals and we managed to record 4h of songs performed by six different whales. Given that the size of the New Caledonian population is currently thought to be less than 1000 individuals, our sampling is not too bad!

A calf breaching out of the water on a late afternoon. No wonder humpback whales are favored by whale-watching companies, they can be very active at the surface!
A calf breaching out of the water on a late afternoon. No wonder humpback whales are favored by whale-watching companies, they can be very active at the surface!
These two adult whales were part of a very active competitive group of eight individuals and displayed a peculiar behavior that included gently rolling and rubbing themselves against each other.
These two adult whales were part of a very active competitive group of eight individuals and displayed a peculiar behavior that included gently rolling and rubbing themselves against each other.

Another great achievement of this season was the tagging of two adult humpback whales with ARGOS satellite-tracking devices. It was a thrilling experience to be part of this procedure and witness the level of concentration and experience required to place a tag on a whale. Our two individuals, one a presumed male and the other a female with calf, were respectively baptized Lutèce (the name Romans gave to Paris) and Ovalie (an old fashioned way to call rugby in France). Their tags transmitted for 15 and 20 days respectively, which was not long enough to follow their migration south towards Antarctica. Yet, both whales spent time on seamounts that are known to play an important role for humpback whales in the region. We were very interested in Ovalie’s track (map given below), as she travelled along the Loyalty ridge, a seafloor structure of great interest to us. We suspect that whales could be using this ridge as a navigational aid and/or using shallow areas (seamounts and banks) along the ridge as resting or breeding habitats. The amount of humpback whales present in this area and the eventual role played by oceanic features along the Loyalty ridge will be the subject of my future research.

Raw ARGOS track: Ovalie visiting seamounts south of New Caledonia and then travelling towards the Loyalty ridge (Don’t worry whales didn’t start walking on land since you saw your last National Geographic documentary; the accuracy of the satellite transmitter is to blame. For some of these points accuracy simply can’t be estimated –classes A and B- and unrealistic locations will have to be removed before performing analysis. In general, accuracy of ARGOS locations ranges between 250 and 1500m).
Raw ARGOS track: Ovalie visiting seamounts south of New Caledonia and then travelling towards the Loyalty ridge (Don’t worry whales didn’t start walking on land since you saw your last National Geographic documentary; the accuracy of the satellite transmitter is to blame. For some of these points accuracy simply can’t be estimated –classes A and B- and unrealistic locations will have to be removed before performing analysis. In general, accuracy of ARGOS locations ranges between 250 and 1500m).

 

But now that we have all this data, let’s get back to work! As much as I love being in the field, there comes a time when you have to sit in front of your computer and try to make sense of all this information you collected.

And that is where my collaboration with the GEMM Lab comes in! I am looking forward to visiting Newport once again in December and to start shedding a light on the ‘How’s and ‘Why’s of New Caledonian humpback whales’ space use.

Literature cited:

Garrigue, C., Clapham, P. J., Geyer, Y., Kennedy, A. S., & Zerbini, A. N. (In Press). Satellite tracking reveals novel migratory patterns and the importance of seamounts for endangered South Pacific Humpback Whales. Royal Society Open Science.

 

Sharing the Science! Outreach at the GEMM Lab

Hello Everyone,

My name is Florence, and I’m here to update you on all the amazing outreach activities that the GEMM lab has participated in this past month!

We started on April 11, with the HMSC-wide Marine Science Day celebrations.  This year was particularly exciting because the Hatfield Marine Science Center is turning 50 years old! Along with the rest of our colleagues at the Marine Mammal Institute, we presented posters detailing our projects, had a few hands on activities such as ‘spot the whale’ – a bit of a scavenger hunt designed to give people a taste of how difficult it can be to spot marine mammals, and answered questions about our work.  It was quite a success!

IMG_6948
Florence representing the GEMM lab and gray whale research in Port Orford
IMG_6939
The Redfish Rocks Community Team table!

On April 19, I went down to Port Orford, OR to participate in “Redfish Rocks on the Docks”  an outreach event showcasing all the exciting research being done in conjunction with the Redfish Rocks Marine Reserve near Port Orford.  I presented a poster about my thesis project: Assessment of vessel disturbance to foraging gray whales on the Oregon Coast to promote sustainable ecotourism, and answered questions while leading folks through our ‘stay warm like a whale’ blubber glove activity.  It was a beautiful sunny day, but so windy that at times we joked that our tables looked more like geology presentations than marine biology due to all the rocks holding everyone’s papers, photos, and flyers down! Many of the folks who I will be collaborating with over the course of this project also had their own informational booths; South Coast Tours, Redfish Rocks Community Team, and the Oregon Marine Reserves Program. The Surfrider Foundation and CoastWatch also had interesting activities and information to share about marine debris and conservation of our oceans.  My favorite moment of the day was when I was explaining to a little girl how gray whales need to eat a lot of mysid shrimp in order to maintain their blubber to stay warm in the frigid ocean – and she intuitively made the jump from the blubber glove to the wetsuit she uses to go swimming!  It was wonderful to see her thinking critically about the different strategies for heat retention in water.

 

Lab group photo
The Ladies of the GEMM Lab! Courtney, Amanda, Dr. Leigh, Florence, Solène
Solene Best presentation (1)
Solène received the Best Presentation Award!

Finally, yesterday, almost the entire lab gave presentations at the Northwest Student Society of Marine Mammals Annual Meeting.  The meeting was attended by ~80 interested students and researchers from a number of outstanding universities including; Western Washington University, University of Washington, Portland State, Stanford University and of course, Oregon State University.  The day began with an excellent introductory presentation by Dr. Ari Friedlander of our sister BTBEL Lab, and then it was on to student presentations.  Courtney and I presented in the ‘Human Dimensions’ forum on the possibilities of citizen science in marine mammal research and gray whale foraging ecology respectively.  At lunch, our valiant leader, Leigh, took part in a discussion panel and fielded questions from the audience concerning current advances in technology and possible applications to field work as well as giving professional development advice.  A few take away messages; Technology can provide wonderful insights, but one should not use a tool just to use a tool.  Rather, it is important to first ask your question, and then build your methodology and choose your tools in a manner most precisely able to answer the questions at hand.  In regards to professional development, do not discount the benefit of getting international experience – A broad perspective on possible solutions, and strong international collaborations will be necessary to solve many of the management issues facing our oceans today.  During the ‘Bioacoustics’ session, Amanda presented her work concerning harbor porpoise spatial distribution. Finally, Solène presented her work on Maui’s dolphins during the ‘Space and Time’ Session, and walked out having earned the ‘Best Presentation’ Award!!  Over the past few months that she has been visiting us, she has been a dedicated colleague and a wonderfully cheerful presence in the lab, and it was fantastic to see all her hard work being recognized in this public forum.  Overall, this NWSSMM conference was a great opportunity to see what other students in the Pacific Northwest region are working on, opened doors for future collaborations and gave us ideas for future projects.

 

Sunrise in Port Orford
Sunrise in Port Orford

International Collaborations: What do the Oregon Coast and Maui’s dolphins have in common?

My name is Solène Derville and I am a master’s student in the Department of Biology at the Ecole Normale Supérieure of Lyon, France. As part of my master’s, I am spending a few months in Newport, where I am working under Dr Leigh Torres’s supervision in the GEMM Lab. Hopefully, this will be the starting point for a longer term collaboration, for a PhD project about the spatial ecology of humpback whales in New-Caledonia (South Western Pacific Ocean) which I am currently preparing.

Solene at Crater lake

On an early morning of February 2015, I am waiting at the airport for my flight to PORTLAND/PDX. I’ve had only one day to pack but I feel confident that I’ve made the right choices as my 23kg luggage contains mainly jumpers, sweatshirts, thick socks, and a brand new umbrella. I’ve got everything I need to face my four months internship in rainy Newport, Oregon.

A few disillusionments await me when I finally land: 1) my “saucisson” (fancy sausage) can’t pass customs and ends up in a bin despite my attempts to negotiate with the customs official, and 2) as soon as I am out of the airport, it starts raining. At first sight this looks like the harmless kind of drizzle I’ve experienced in England, until I realize it’s raining sideways! So much for buying a new umbrella…

Luckily, these small inconveniences don’t affect my spirits for long as I get to discover the richnesses Oregon has to offer.

My mouth drops open the first time someone tells me that I can see elk around Newport and that gray whales are commonly observed next to the jetty at this time of year. It’s difficult to describe to someone who’s always been living in this environment how exciting it is to me. I am not used to all this wilderness and certainly not to living so close to it. It’s a thrill to think that I only need to ride my bike for a few miles to meet the amazing local fauna.

Oregon Coast by Solene
Oregon Coast by Solene

Of course, the beauty of Oregon’s landscapes and the richness of its wildlife is not the only thing that catches my attention. I am immediately touched by the kindness of people, the sense of sharing and the deeply rooted sense of community. I feel welcomed at HMSC, and by my colleagues in the GEMM lab and I am eager to start my internship.

So what is my work here exactly?

Well, believe it or not, I’ve crossed the Atlantic Ocean and came to the US to actually work on a species of dolphins endemic to New-Zealand! Dr Leigh Torres, and I are investigating the fine-scale distribution and habitat selection patterns of Maui’s dolphin (Cephalorhyncus hectori maui). This subspecies of the more common Hector’s dolphin (Cephalorhyncus hectori, also endemic to New-Zealand) is the smallest dolphin in the world and unfortunately among the most endangered (listed as “critically endangered” by the IUCN). The Maui’s dolphin population is thought to have decreased to under 100 individuals in the past decades.

Maui's dolphin credit: Will Rayment
Maui’s dolphin credit: Will Rayment

In practice, this means I am doing data analysis so I spend my days in front of my computer. This may sound a bit dull, but computer work is actually a great part of research in ecology (apart from awesome field work stage, but this is only the tip of the iceberg). Speaking for myself, I’ve always found it very exciting to put together all this hard-won data to answer important questions, especially when the conservation of species as emblematic as the Maui’s dolphin is at stake. To tell the truth, the nerdy code writing work is also a lot of fun!

My data set consists of boat-based observations of Maui dolphin groups made during the 2010, 2011, 2013 and 2015 summer surveys. Overall about a hundred groups were observed. Based on these observations we would like to know: WHERE are the Maui dolphins (distribution pattern)? And WHY (habitat preferences)?

New Zealand
New Zealand

My job is first to describe the spatial distribution patterns of these observations given the year, composition of groups, or group behaviour (whether animals were feeding, resting etc.). This can be done using kernel density estimates: a very good method for “smoothing” a distribution in 2 dimensions and highlighting its main characteristics (extent, core areas etc.). This allows us to answer (or try to answer) the “WHERE” question.

Kernel density maps
Kernel density maps

The second stage of my analysis is to describe the environmental conditions at each of the dolphin group locations and compare them with the environmental conditions in surveyed areas where Maui dolphins where not observed. This allows us to better understand the environmental cues that Maui dolphins might be following to find “suitable” places for their every-day activities and therefore try answer the “WHY” question. In statistical jargon, we are exploring the relationship between probability of presence of Maui dolphins and environmental predictors such as: sea surface temperature, turbidity of the water, distance to closest river mouths, distance to the coast and depth.

The resulting models will be used to predict seasonal variations in Maui’s dolphin distribution, notably in winter when direct surveying is difficult because of weather conditions. Based on the resulting dynamic distribution models, we finally aim to predict how Maui’s dolphins might interact with anthropogenic activities or react to changes in their environment.

So far, preliminary results are very promising and I am hoping to share these soon!