Month: September 2020

Tales from the birds in the nest (on the ship at sea)

Clara Bird, PhD Student, OSU Department of Fisheries and Wildlife, Geospatial Ecology of Marine Megafauna Lab

Greetings from the NOAA research vessel Shimada! As you may know from previous blogs, usually one member of the GEMM Lab goes on the Northern California Current (NCC) ecosystem survey cruises as a marine mammal observer to collect data for the project Where are whales in Oregon waters? But for this September 2020 cruise we have two observers on-board. I’m at-sea  with fellow GEMM lab student Dawn Barlow to learn the ropes and procedures for how we collect data. This research cruise is exciting for a few reasons: first, this is my first cruise as a marine mammal observer! And second, this is the first NOAA Northwest Fisheries Science Center research cruise since the COVID-19 pandemic began in the United States.

Our job as observers involves surveying for marine mammals from the flying bridge, which is the upper most deck of the ship, above the Bridge where the officers command the vessel. Here, we are referred to as the “birds in the nest” by the officers (something I find fitting given my last name). We spend our time looking out at the water with our binoculars searching for any sign of a marine mammal. These signs include: a blow, a fluke, a flipper, or the splash of a dolphin. Surveys involve long stretches of time staring at the ocean seeing nothing but blue waves, punctuated by exciting moments. The level of excitement of these moments can range from finally seeing a blow in the distance to seeing a whale breach! As of the time I’m writing this blog, we’ve been at sea for six days and have four more to go, so I will describe the things we’ve seen and my experience being on a primarily oceanographic research cruise.

We started day one transiting offshore of Newport, right into some whale soup! What started as a few distant blows quickly became an ocean full of whales. Dawn and I were some-what frantic as we worked to keep track of the many humpback and blue whales that were around us (I saw my first blue whale!). We even saw a humpback whale breaching! This introduction to marine mammal observation was an exciting exercise in keeping track of blows and rapid species identification. Day two was pretty similar, as we spent the day travelling back inshore along the same path we had followed offshore on day one. It was cool to see that there were still many whales in the same area.

On day three we woke up to dense fog, and overall pretty poor conditions for marine mammal observing. One of the challenges of this work is that not only does bad weather make it hard to see, but it also makes it hard for us to be able to say that mammals were truly absent. In bad observation conditions we cannot know if we did not see anything because the animals were not there or if we just could not see them through the swell, fog or white-caps. However, by the late afternoon the fog cleared and we had a spectacular end of the day. We saw a killer whale breach (Image 1) and a humpback whale tail lobbing (smacking it’s fluke against the surface of the water) in front of a stunning sunset (Image 2).

(Top) Figure 1. A killer whale breaching. Photo credit: Clara Bird. (Bottom) Figure 2. A humpback whale fluke at sunset. Photo credit: Dawn Barlow.

Day four was a bit of a marine mammal work reality check. While spectacular evenings like day three are memorable and exhilarating, they tend to be rare. The weather conditions on day four were pretty poor and we ended up surveying from the bridge for most of the day and not seeing much. Conditions improved on day five and we had some fun dolphin sightings where they came and rode on the wake from the bow, and observed a sperm whale blow in the distance!

The weather was not great today (day six), especially in the morning, but we did have one particularly exciting sighting right along the edge of Heceta Bank. While we were stopped at an oceanographic sampling station, we were visited by a group of ~30 pacific white sided dolphins who spent about half an hour swimming around the ship. We also saw several humpback whales, a fur seal, and a Mola mola (Ocean sunfish)! It was incredible to be surrounded by so many different species, all so close to the ship at the same time.

Overall, it has been wonderful to be out at sea after the many isolating months of COVID. And, it has been an exciting and interesting experience being surrounded by non-whale scientists who think about this ecosystem from a different perspective. This cruise is focused on biological oceanography, so I have had the great opportunity to learn from these amazing scientists about what they study and what oceanographic patterns they document. It’s a good reminder of our interconnected research. While it’s been cool to observe marine mammals and think about something totally different from my research on gray whale behavior, I have also enjoyed finding the similarities. For example, just last night I had a conversation with a graduate student researching forams (check out this link to learn more about these super cool tiny organisms!). Even though the organisms we study are polar opposites in terms of size, we actually found out that we had a good bit in common because we both use images to study our study species and have both encountered similar unexpected technical challenges in our methods.

I am thoroughly enjoying my time being one of the “birds in the nest”, contributing data to this important project, and meeting these wonderful scientists. If you are curious about how the rest of the cruise goes, make sure to check out Dawn’s blog next week!

Cascadia 2020: Exploring Oregon via Zoom

By Rachel Kaplan, PhD student, OSU College of Earth, Ocean, and Atmospheric Sciences and Department of Fisheries and Wildlife, Geospatial Ecology of Marine Megafauna Lab

As a newly-minted PhD student, starting graduate school has so far been everything I dreamt — and a bit more. I expected the excitement of meeting my cohort and professors, and starting classes. The apocalyptic drive to campus through a fiery sky as fires burned across Oregon, and the week after spent solely indoors, I did not.

When conditions allow, being in the field is one of my favorite parts of the scientific process!

As I’ve settled into Corvallis, my program, and navigating the roadblocks 2020 keeps throwing our way, I have been so grateful for the warm (virtual) welcome by my lab groups, professors, and fellow students. One of the most impressive displays of flexibility and adaptability so far is the ever-evolving field course I am currently taking.

Called “Cascadia,” this course provides an introduction to the range of geological, physical, ecological, and biogeochemical topics that exist within the Pacific Northwest, and explores the linkages between these areas. The course’s goal is to introduce incoming CEOAS (College of Earth, Ocean, and Atmospheric Sciences) students to the surrounding landscape, and to the ways that human systems interact with that landscape. 

The professors teaching Cascadia — Drs. Frederick Colwell, Emily Shroyer, and George Waldbusser — have done an amazing job adapting the course to unprecedented circumstances. Over the summer, safety measures due to the pandemic required them to move the course to a largely online format, with only three planned day trips (typically the course is a full ten-day road trip around the state). Over the last week, the fires raging around Oregon have forced them to adapt the course repeatedly in real time, postponing field trips based on air quality forecasts and site closures.

During a typical year in the Cascadia course, the incoming students learn while exploring, camping, and hiking their way around a number of sites around Oregon. This year, our classmates are scattered around the country and our explorations have taken place in a Zoom room — but that hasn’t stopped the experience from being great.

Several professors shared their expertise with us through a series of talks that covered the ecology and history of the Willamette River, Pacific Northwest volcanoes, tsunami safety and preparation, and even wildfire ecology. In addition to talks by subject matter experts, each student delved into and presented on a topic of their choice, allowing us to learn from one another about everything from edible plants, to Oregon craft beers, to human movements throughout the Willamette River valley. We also enjoyed gorgeous pictures of Oregon’s mountains, coast, and desert, and received recommendations for trips and hikes that everyone is excited to explore.

As of the time of writing this blog, I’m excited to say that things may look a little different tomorrow — rain and improved air quality are in the forecast, and the Cascadia crew is planning to venture out to the coast for our first field trip! We’ll be learning on-site about the Oregon Coast Range and coastal dynamics, climate, and processes. This will actually be my first time on the Oregon coast, but definitely not my last.

For my PhD research, I will work with Dr. Leigh Torres and Dr. Kim Bernard (CEOAS) to understand how ocean conditions and prey distribution shape where whales are found in Oregon waters. Whale entanglements in Dungeness crab fishing gear have been on the rise since 2014, and we will collaborate with the Oregon Whale Entanglement Working group to look for solutions to this problem. 

A big part of my excitement about this research project lies in the way it intersects natural and human systems, just as we have been exploring through the Cascadia course. I am interested in how marine mammal distribution and behavior intersect with human systems — and how understanding these interactions can inform management and conservation efforts. I am thrilled to be a new member of the GEMM Lab, and to be starting (remote) classes and this research. For now, I’m wishing everyone good air quality and a safe fall!

Update: The Cascadia class did make it the coast! We were even lucky enough to see gray whales here at Depoe Bay.

Do gray whales count calories?

By Lisa Hildebrand, MSc student, OSU Department of Fisheries & Wildlife, Marine Mammal Institute, Geospatial Ecology of Marine Megafauna Lab

When humans count calories it is typically to regulate and limit calorie intake. What I am wondering about is whether gray whales are aware of caloric differences in the prey that is available to them and whether they make foraging decisions based on those differences. In last week’s post, Dawn discussed what makes a good meal for a hungry blue whale. She discussed that total prey biomass of a patch, as well as how densely aggregated that patch is, are the important factors when a blue whale is picking its next meal. If these factors are important for blue whales, is it same for gray whales? Why even consider the caloric value of their prey?

Gray and blue whales are different in many ways; one way is that blue whales are krill specialists whereas gray whales are more flexible foragers. The Pacific Coast Feeding Group (PCFG) of gray whales in particular are known to pursue a more varied menu. Previous studies along the PCFG range have documented gray whales feeding on mysid shrimp (Darling et al. 1998; Newell 2009), amphipods (Oliver et al. 1984; Darling et al. 1998), cumacean shrimp (Jenkinson 2001; Moore et al. 2007; Gosho et al. 2011), and porcelain crab larvae (Dunham and Duffus 2002), to name a few. Based on our observations in the field and from our drone footage, we have observed gray whales feeding on reefs (likely on mysid shrimp), benthically (likely on burrowing amphipods), and at the surface on crab larvae (Fig. 1). Therefore, while both blue and PCFG whales must make decisions about prey patch quality based on biomass and density of the prey, gray whales have an extra decision to make based on prey type since their prey menu items occupy different habitats that require different feeding tactics and amount of energy to acquire them. In light of these reasons, I hypothesize that prey caloric value factors into their decision of prey patch selection. 

Figure 1. Gray whales use several feeding tactics to obtain a variety of coastal Oregon zooplankton prey including jaw snapping (0:12 of video), drooling mud (0:21), and head standing (0:32), to name a few.

This prey selection process is crucial since PCFG gray whales only have about 6 months to consume all the food they need to migrate and reproduce (even less for the Eastern North Pacific (ENP) gray whales since their journey to their Arctic feeding grounds is much longer). You may be asking, well if feeding is so important to gray whales, then why not eat everything they come across? Surely, if they ate every prey item they swam by, then they would be fine. The reason it isn’t quite this simple is because there are energetic costs to travel to, search for, and consume food. If an individual whale simply eats what is closest (a small, poor-quality prey patch) and uses up more energy than it gains, it may be missing out on a much more beneficial and rewarding prey patch that is a little further away (that patch may disperse or another whale may eat it by the time this whale gets there). Scientists have pondered this decision-making process in predators for a long time. These ponderances are best summed up by two central theories: the optimal foraging theory (MacArthur & Pianka 1966) and the marginal value theorem (Charnov 1976). If you are a frequent reader of the blog, you have probably heard these terms once or twice before as a lot of the questions we ask in the GEMM Lab can be traced back to these concepts.

Optimal foraging theory (OFT) states that a predator should pick the most beneficial resource for the lowest cost, thereby maximizing the net energy gained. So, a gray whale should pick a prey patch where it knows that it will gain more energy from consuming the prey in the patch than it will lose energy in the process of searching for and feeding on it. Marginal value theorem elaborates on this OFT concept by adding that the predator also needs to consider the cost of giving up a prey patch to search for a new one, which may or may not end up being more profitable or which may take a very long time to find (and therefore cost more energy). 

The second chapter of my thesis will investigate whether individual gray whales have foraging preferences by relating feeding location to prey quality (community composition) and quantity (relative density). However, in order to do that, I first must know about the quality of the individual prey species, which is why my first chapter explores the caloric content of common coastal zooplankton species in Oregon that may serve as gray whale prey. The lab work and analysis for that chapter are completed and I am in the process of writing it up for publication. Preliminary results (Fig. 2) show variation in caloric content between species (represented by different colors) and reproductive stages (represented by different shapes), with a potential increasing trend throughout the summer. These results suggest that some species and reproductive stages may be less profitable than others based solely on caloric content. 

Figure 2. Mean caloric content (J/mg) of coastal Oregon zooplankton (error bars represent standard deviation) from May-October in 2017-2018. Colors represent species and shapes represent reproductive stage.

Now that we have established that there may be bigger benefits to feeding on some species over others, we have to consider the availability of these zooplankton species to PCFG whales. Availability can be thought of in two ways: 1) is the prey species present and at high enough densities to make searching and foraging profitable, and 2) is the prey species in a habitat or depth that is accessible to the whale at a reasonable energetic cost? Some prey species, such as crab larvae, are not available at all times of the summer. Their reproductive cycles are pulsed (Roegner et al. 2007) and therefore these prey species are less available than species, such as mysid shrimp, that have more continuous reproduction (Mauchline 1980). Mysid shrimp appear to seek refuge on reefs in rock crevices and among kelp, whereas amphipods often burrow in soft sediment. Both of these habitat types present different challenges and energetic costs to a foraging gray whale; it may take more time and energy to dislodge mysids from a reef, but the payout will be bigger in terms of caloric gain than if the whale decides to sift through soft sediment on the seafloor to feed on amphipods. This benthic feeding tactic may potentially be a less costly foraging tactic for PCFG whales, but the reward is a less profitable prey item.  

My first chapter will extend our findings on the caloric content of Oregon coastal zooplankton to facilitate a comparison to the caloric values of the main ampeliscid amphipod prey of ENP gray whales feeding in the Arctic. Through this comparison I hope to assess the trade-offs of being a PCFG whale rather than an ENP whale that completes the full migration cycle to the primary summer feeding grounds in the Arctic. 

References

Charnov, E. L. 1976. Optimal foraging: the marginal value theorem. Theoretical Population Biology 9:129-136.

Darling, J. D., Keogh, K. E. and T. E. Steeves. 1998. Gray whale (Eschrichtius robustus) habitat utilization and prey species off Vancouver Island, B.C. Marine Mammal Science 14(4):692-720.

Dunham, J. S. and D. A. Duffus. 2002. Diet of gray whales (Eschrichtius robustus) in Clayoquot Sound, British Columbia, Canada. Marine Mammal Science 18(2):419-437.

Gosho, M., Gearin, P. J., Jenkinson, R. S., Laake, J. L., Mazzuca, L., Kubiak, D., Calambokidis, J. C., Megill, W. M., Gisborne, B., Goley, D., Tombach, C., Darling, J. D. and V. Deecke. 2011. SC/M11/AWMP2 submitted to International Whaling Commission Scientific Committee.

Jenkinson, R. S. 2001. Gray whale (Eschrichtius robustus) prey availability and feeding ecology in Northern California, 1999-2000. Master’s thesis, Humboldt State University.

MacArthur, R. H., and E. R. Pianka. 1966. On optimal use of a patchy environment. American Naturalist 100:603-609.

Mauchline, J. 1980. The larvae and reproduction in Blaxter, J. H. S., Russell, F. S., and M. Yonge, eds. Advances in Marine Biology vol. 18. Academic Press, London.

Moore, S. E., Wynne, K. M., Kinney, J. C., and C. M. Grebmeier. 2007. Gray whale occurrence and forage southeast of Kodiak Island, Alaska. Marine Mammal Science 23(2)419-428.

Newell, C. L. 2009. Ecological interrelationships between summer resident gray whales (Eschrichtius robustus) and their prey, mysid shrimp (Holmesimysis sculpta and Neomysis rayii) along the central Oregon coast. Master’s thesis, Oregon State University.

Oliver, J. S., Slattery, P. N., Silberstein, M. A., and E. F. O’Connor. 1984. Gray whale feeding on dense ampeliscid amphipod communities near Bamfield, British Columbia. Canadian Journal of Zoology 62:41-49.

Roegner, G. C., Armstrong, D. A., and A. L. Shanks. 2007. Wind and tidal influences on larval crab recruitment to an Oregon estuary. Marine Ecology Progress Series 351:177-188.

What makes a good meal for a hungry whale?

By Dawn Barlow, PhD student, OSU Department of Fisheries and Wildlife, Geospatial Ecology of Marine Megafauna Lab

In the vast and dynamic marine environment, food is notoriously patchy and ephemeral [1]. Predators such as marine mammals and seabirds must make a living in this dynamic environment by locating and capturing those prey patches. Baleen whales such as blue and humpback whales have a feeding strategy called “lunge feeding”, whereby they accelerate forward and open their massive jaws, engulf prey-laden water in their buccal pouch that expands like an accordion, and filter the water out through baleen plates so that they are left with a mouthful of food (Fig. 1) [2]. This approach is only efficient if whales can locate and target dense prey patches that compensate for the energetic costs of diving and lunging [3]. Therefore, not only do these large predators need to locate enough food to survive in the expansive and ever-changing ocean, they need to locate food that is dense enough to feed on, otherwise they actually lose more energy by lunging than they gain from the prey they engulf.

Figure 1. Schematic of a humpback whale lunge feeding on a school of fish. Illustration by Alex Boersma.

Why do baleen whales rely on such a costly feeding approach? Interestingly, this tactic emerged after the evolution of schooling behavior of prey such as zooplankton and forage fish (e.g., herring, anchovy, sand lance) [4]. Only because the prey aggregate in dense patches can these large predators take advantage of them by lunge feeding, and by engulfing a whole large patch they efficiently exploit these prey patches. Off the coast of California, where krill aggregations are denser in deeper water, blue whales regularly dive to depths of 100-300 m in order to access the densest krill patches and get the most bang for their buck with every lunge [5]. In New Zealand, we have found that blue whales exploit the dense krill patches near the surface to maximize their energetic gain [6], and have documented a blue whale bypassing smaller krill patches that presumably were not worth the effort to feed on.

By now hopefully I have convinced you of the importance of dense prey patches to large whales looking for a meal. It is not necessarily only a matter of total prey biomass in an area that is important to a whale, it is whether that prey biomass is densely aggregated. What makes for a dense prey patch? Recent work has shown that forage species, namely krill and anchovies, swarm in response to coastal upwelling [7]. While upwelling events do not necessarily change the total biomass of prey available to a whale over a spatial area, they may aggregate prey to a critical density to where feeding by predators becomes worthwhile. Forage species like zooplankton and small fish may school because of enhanced food resources, for predator avoidance, or reproductive grouping. While the exact behavioral reason for the aggregation of prey may still only be partially understood, the existence of these dense patches allows the largest animals on the planet to survive.

Another big question is, how do whales actually find their food? In the vast, seemingly featureless, and ever-changing ocean environment, how does a whale know where to find a meal, and how do they know it will be worthwhile before they take a lunge? In a review paper written by GEMM Lab PI Dr. Leigh Torres, she suggests it is all a matter of scale [8]. On a very large scale, baleen whales likely rely on oceanographic stimuli to home in on areas where prey are more likely to be found. Additionally, recent work has demonstrated that migrating blue whales return to areas where foraging conditions were best in previous years, indicating a reliance on memory [9,10]. On a very fine scale, visual cues may inform how a blue whale chooses to lunge [6,8,11].

What does it matter what a blue whale’s favorite type of meal is? Besides my interest in foundational research in ecology such as predator-prey dynamics, these questions are fundamental to developing effective management approaches for reducing impacts of human activities on whales. In the first chapter of my PhD, I examined how oceanographic features of the water column structure krill aggregations, and how blue whale distribution is influenced by oceanography and krill availability [12]. Currently, I am deep into my second chapter, analyzing the pathway from wind to upwelling to krill to blue whales in order to better understand the links and time lags between each step. Understanding the time lags will allow us to make more informed models to forecast blue whale distribution in my third chapter. Environmental managers in New Zealand plan to establish a protected area to conserve the population of blue whales that I study [13] on their foraging grounds. Understanding where blue whales will be distributed, and consequently how their distribution patterns might shift with environmental conditions or overlap with human activities, comes down the fundamental question I started this blog post with: What makes a good meal for a hungry whale?

References

1.        Hyrenbach KD, Forney KA, Dayton PK. 2000 Marine protected areas and ocean basin management. Aquat. Conserv. Mar. Freshw. Ecosyst. 10, 437–458. (doi:10.1002/1099-0755(200011/12)10:6<437::AID-AQC425>3.0.CO;2-Q)

2.        Goldbogen JA, Cade DE, Calambokidis J, Friedlaender AS, Potvin J, Segre PS, Werth AJ. 2017 How Baleen Whales Feed: The Biomechanics of Engulfment and Filtration. Ann. Rev. Mar. Sci. 9, 367–386. (doi:10.1146/annurev-marine-122414-033905)

3.        Goldbogen JA, Calambokidis J, Oleson E, Potvin J, Pyenson ND, Schorr G, Shadwick RE. 2011 Mechanics, hydrodynamics and energetics of blue whale lunge feeding: efficiency dependence on krill density. J. Exp. Biol. 214, 131–146. (doi:10.1242/jeb.048157)

4.        Cade DE, Carey N, Domenici P, Potvin J, Goldbogen JA. 2020 Predator-informed looming stimulus experiments reveal how large filter feeding whales capture highly maneuverable forage fish. Proc. Natl. Acad. Sci. U. S. A. (doi:10.1073/pnas.1911099116)

5.        Hazen EL, Friedlaender AS, Goldbogen JA. 2015 Blue whales (Balaenoptera musculus) optimize foraging efficiency by balancing oxygen use and energy gain as a function of prey density. Sci. Adv. 1, e1500469–e1500469. (doi:10.1126/sciadv.1500469)

6.        Torres LG, Barlow DR, Chandler TE, Burnett JD. 2020 Insight into the kinematics of blue whale surface foraging through drone observations and prey data. PeerJ (doi:10.7717/peerj.8906)

7.        Benoit-Bird KJ, Waluk CM, Ryan JP. 2019 Forage Species Swarm in Response to Coastal Upwelling. Geophys. Res. Lett. 46, 1537–1546. (doi:10.1029/2018GL081603)

8.        Torres LG. 2017 A sense of scale: Foraging cetaceans’ use of scale-dependent multimodal sensory systems. Mar. Mammal Sci. 33, 1170–1193. (doi:10.1111/mms.12426)

9.        Abrahms B et al. 2019 Memory and resource tracking drive blue whale migrations. Proc. Natl. Acad. Sci. U. S. A. (doi:10.1073/pnas.1819031116)

10.      Szesciorka AR, Ballance LT, Širovi A, Rice A, Ohman MD, Hildebrand JA, Franks PJS. 2020 Timing is everything: Drivers of interannual variability in blue whale migration. Sci. Rep. 10, 1–9. (doi:10.1038/s41598-020-64855-y)

11.      Friedlaender AS, Herbert-Read JE, Hazen EL, Cade DE, Calambokidis J, Southall BL, Stimpert AK, Goldbogen JA. 2017 Context-dependent lateralized feeding strategies in blue whales. Curr. Biol. (doi:10.1016/j.cub.2017.10.023)

12.      Barlow DR, Bernard KS, Escobar-Flores P, Palacios DM, Torres LG. 2020 Links in the trophic chain: Modeling functional relationships between in situ oceanography, krill, and blue whale distribution under different oceanographic regimes. Mar. Ecol. Prog. Ser. (doi:https://doi.org/10.3354/meps13339)

13.      Barlow DR et al. 2018 Documentation of a New Zealand blue whale population based on multiple lines of evidence. Endanger. Species Res. 36, 27–40. (doi:https://doi.org/10.3354/esr00891)