Assessing suitable sea otter habitat along Oregon’s coast

By Dominique Kone, Masters Student in Marine Resource Management

When considering a species reintroduction into an area, it is important to assess the suitability of the area’s habitat before such efforts begin. By doing this assessment at the outset, managers and conservationists can gain a better understanding of the capacity of the area to support a viable population overtime, and ultimately the success of the reintroduction. However, to do a habitat assessment, researchers must first have a base understanding of the species’ ecological characteristics, behavior, and the physical habitat features necessary for the species’ survival. For my thesis, I plan to conduct a similar assessment to identify suitable sea otter habitat to inform a potential sea otter reintroduction to the Oregon coast.

Source: The Tribune.

To start my assessment, I conducted a literature review of studies that observed and recorded the various types of habitats where sea otters currently exist. In my research, I learned that sea otters use in a range of environments, each with a unique set of habitat characteristics. With so many features to sort through, I have focused on specific habitat features that are consistent across most of the current range of sea otters – from Alaska to California – and are important for at least some aspects of sea otters’ everyday life or behavior, specifically foraging. Focusing my analysis on foraging habitat makes sense as sea otters require around 30% of their body weight in food every day (Costa 1978, Reidman & Estes 1990). Meaning sea otters spend most of their day searching for food.

Here, I present four habitat features I will incorporate into my analysis and explain why these features are important for sea otter foraging behavior and survival.

Habitat Features:

  1. Kelp: Sea otters are famously known for the benefits they provide to kelp forests. In the classic three-trophic-level model, sea otters allow for the growth of kelp by keeping sea urchins – consumers of kelp – in check (Estes & Palmisano 1974). Additionally, sea otters and kelp have a mutually-beneficial relationship. Sea otters will often wrap themselves amongst the top of kelp stocks while feeding, resting, or grooming to prevent being carried away by surface currents. Meanwhile, it’s thought that kelp provide a refuge for sea otters seeking to avoid predators, such as sharks, as well as their prey.
Source: The Telegraph.
  1. Distance from Kelp: The use of kelp, by sea otters, is relatively straight-forward. Yet, kelp can still have an influence on sea otter behavior even when not used directly. A 2014 study found that sea otters along the southern California coast were almost 10 times more likely to be located within kelp habitat than outside, while outside kelp beds sea otter numbers declined with distance from the edge of kelp canopies. Sea otters will often forage outside or next to kelp canopies when prey’s available, and even sometimes to socialize in age- or sex-specific rafts (Lafferty & Tinker 2014). These findings indicate that sea otters can and do regularly disperse away from kelp habitat, but because they’re so dependent on kelp, they don’t stray very far.

 

  1. Seafloor Substrate: Sea otters forage over a variety of sediment substrates, including rocks, gravel, seagrass, and even sometimes sand. For example, sea otters hunt sea urchins over rocky substrates, while in other areas they may hunt for crabs in seagrass beds (Estes & Palmisano 1974, Hughes et al. 2014). The type of substrate sea otters forage in typically depends on the substrate needs of their target prey species. Despite some variability across their range, sea otters predominantly forage in rocky substrate environments. Rocky substrate is also necessary for kelp, whose holdfasts need to attach to hard, stable surfaces (Carney et al. 2005).
Source: Save our Seas Foundation.
  1. Depth: Seafloor depth plays a pivotal role in sea otter foraging behavior and therefore acts as a natural boundary that determines how far away from shore sea otters distribute. Many of the prey species sea otters eat – including sea urchins, crabs, and snails – live on the seafloor of the inner continental shelf, requiring sea otters to dive when foraging. Interestingly, sea otters exhibit a non-linear relationship with depth, where most individuals forage at intermediate depths as opposed to extremely shallow or deep waters. One study found the average foraging depth to be around 15 meters (Lafferty & Tinker 2014). This behavior results in a hump-shaped distribution of diving patterns as illustrated in Figure 1 below.
Figure 1. Average probability of occurrence as a function of depth for female (A) and male (B) sea otters as predicted by a synoptic model of space-use (Tinker et al. 2017).

Of course, local conditions and available habitat are always a factor. For example, a study found that sea otters along the coast of Washington foraged further from shore and in slightly shallower environments than sea otters in California (Laidre et al. 2009), indicating that local topography is important in determining distribution. Additionally, diving requires energy and limits how deep sea otters are able to forage for prey. Therefore, diving patterns are not only a function of local topography, but also availability of prey and foraging efficiency in exploiting that prey. Regardless, most sea otter populations follow this hump-shaped diving pattern.

Source: Doretta Smith.

These features are not a complete list of all habitat characteristics that support viable sea otter populations, but seem to be the most consistent throughout their entire range, as well as present in Oregon’s nearshore environment – making them ideal features to include in my analysis. Furthermore, other studies that have predicted suitable sea otter habitat (Tinker et al. 2017), estimated carrying capacity as a product of suitable habitat identification (Laidre et al. 2002), or simply observed sea otter foraging behavior (Estes & Palmisano 1974), have echoed the importance of these four habitat features to sea otter survival.

As with most reintroduction efforts, the process of identifying suitable habitat for the species of interest can be complicated. No two ecosystems or habitats are exactly alike and each comprise their own unique set of physical features and are impacted by environmental processes to varying degrees. The Oregon coast consists of a unique combination of oceanographic conditions and drivers that likely impact the degree and amount of available habitat to sea otters. Despite this, by focusing on the habitat features that are consistently preferred by sea otters across most of their range, I will be able to identify habitat most suitable for sea otter survival in Oregon. The questions of where this habitat is and how much is available are what I’ll determine soon, so stay tuned.

References:

Carney, L. T., Robert Waaland, J., Kilinger, T., and K. Ewing. 2005. Restoration of the bull kelp Nereocystis luetkeana in nearshore rocky habitats. Marine Ecology Progress Series. 302: 49-61.

Costas, D. P. 1978. The ecological energetics, waters, and electrolyte balance of the California sea otter (Enhydra lutris). Ph.D. dissertation, University of California, Santa Cruz.

Estes, J. A. and J. F. Palmisano. 1974. Sea otters: their role in structuring nearshore communities. Science. 185(4156): 1058-1060.

Hughes et al. 2014. Recovery of a top predator mediate negative eutrophic effects on seagrass. Proceedings of the National Academy of Sciences. 110(38): 15313-15318.

Lafferty, K. D. and M. T. Tinker. 2014. Sea otters are recolonizing southern California in fits and starts. Ecosphere. 5(5): 1-11.

Laidre et al. 2002. Estimates of carrying capacity for sea otters in Washington state. Wildlife Society Bulletin. 30(4): 1172-1181.

Laidre et al. 2009. Spatial habitat use patterns of sea otters in coastal Washington. Journal of Mammalogy. 90(4): 906-917.

Tinker et al. 2017. Southern sea otter range expansion and habitat use in the Santa Barbara Channel, California: U.S. Geological Survey Open-File Report 2017-1001 (OCS Study BOEM 2017-022), 76 p., http://doi.org/10.3133/ofr20171001.

Reidman, M. L. and J. A. Estes. 1990. The sea otter (Enhydra lutris): behavior, ecology, and natural history. United States Department of the Interior, Fish and Wildlife Service, Biological Report. 90: 1-126.

 

 

Conservation at the Science-to-Policy Interface

By Dominique Kone, Masters Student in Marine Resource Management

How can I practice conservation? As an early-career professional and graduate student, this is the very question I ask myself, constantly. In such an interdisciplinary field, there are several ways someone can address issues and affect change in conservation, even if they don’t call themselves a conservationist. However, there’s no one-size-fits-all method. A marine ecologist will likely try to solve a problem differently than a lawyer, advocate, journalist and so forth. Therefore, I want to explain how I practice conservation, how I develop solutions, and how this has factored into my decision to come to grad school and apply my trade to our sea otter project.

Jane Lubchenco – marine ecologist and environmental scientists – replanting coral. Photo Credit: Oregon State University.

Like many others in conservation, I have a deep appreciation for the field of ecology. Yet, I also really enjoy being involved in policy and management issues. Not just how they’re decided upon, but what factors and variables go into those decisions, and ultimately how those choices impact the marine environment. But most importantly, I’m curious about how these two arenas – science and policy – intersect and complement each other. Yet again, there are an endless number of ways one can practice conservation at the science-policy interface.

Think of this science-policy space as a spectrum or a continuum, if you will. For those who fall on one end of the spectrum, their work may be heavily dominated by pure science or research. While those who fall on the other end, conduct more policy-oriented work. And those in the middle do some combination of the two. Yet, what connects us all is the recognition of the value in science-based decision-making. Because a positive conservation result relies on both elements.

Infographic demonstrating the interface between conservation science and policy. Photo Credit: ZSL Institute of Zoology.

I’m fascinated by this science- policy space and the role that science can play in informing the management and protection of at-risk marine species and ecosystems. From my perspective, scientific evidence and the scientific community are essential resources to help society make better-informed decisions. However, we don’t always take advantage of those resources. On the policy end of the spectrum, there may be a lack of understanding of complex scientific concepts. Yet, on the other end, scientists may be inadvertently making their research inaccessible or they may not fully understand the data or knowledge needs of the decision-makers. Therefore, research that was meant to be useful, sometimes completely misses the mark, and therefore has minimal conservation impact.

Recognizing this persistent problem, I practice conservation as a facilitator, where I identify gaps in knowledge and strategically develop science-based solutions aimed at filling those gaps and addressing specific policy or management issues. In my line of work, I’m dedicated to working within the scientific community to develop targeted research projects that are well placed and thought-out to enable a greater impact. While I associate myself with the science end of the spectrum, I also interact with decision-makers on the other end to better understand the various factors and variables considered in decisions. This requires me to have a deeper understanding of the process by which decision-makers formulate policies and management strategies, how science fits within those decision-making process, and any potential gaps in knowledge or data that need to be filled to facilitate responsible decisions.

A commercial fishing vessel. Photo Credit: NOAA Fisheries.

A simple example of this is the use of stock assessments in the management of commercially important fisheries. Catch limits may seem like simple policies, but we often do not think about the “science behind the scenes” and the multitude of data needed by managers to set those limits. Managers must consider many variables to determine catch limits that will not result in depleted stocks. Without robust scientific data, many of these fisheries catch limits would be too high or too low.

Science protest in Washington, DC. Photo Credit: AP Photo/Marcio Jose Sanchez.

This may all sound like theoretical mumbo jumbo, but it is real, and I will apply this crossover between science and policy in my thesis. The potential reintroduction of sea otters to Oregon presents a multitude of challenges, but the challenge is exactly why I came to grad school in the first place! This project will allow me to take what I’ve learned and develop research questions specifically aimed at providing data and information that managers must consider in their deliberations of sea otter reintroduction. In this project I will be pushed to objectively assess and analyze – as a scientist – a pressing conservation topic from a variety of angles, gain advice from other experts, and develop and execute research that will influence policy decisions. This project provides the perfect opportunity for me to exercise my creativity, allow my curiosity to run rampant, and practice conservation in my own unique way.

 

Photo Credit: Smithsonian.

Everyone processes and solves problems differently. For those of us practicing conservation, we each tackle issues in our own way depending on where we fall within the science-to-policy spectrum. For me, I address issues as a scientist, with my techniques and strategies derived from a foundation in the political and management context.

Additional Resources:

Bednarek et al. 2015. Science-policy intermediaries from a practitioner’s perspective: The Lenfest Ocean Program experience. Science and Public Policy. 43(2). p. 291-300. (Link here)

Lackey, R. T. 2007. Science, Scientists, and Policy Advocacy. Conservation Biology. 21(1). p. 12-17. (Link here)

Cortner, H. J. 2000. Making science relevant to environmental policy. Environmental Science & Policy. 3(1). p. 21-30. (Link here)

New Study Looks to Investigate the Potential Reintroduction of Sea Otters to Oregon

By Dominique Kone, Masters Student in Marine Resource Management

As I begin a new chapter as a grad student in the Marine Resource Management program at Oregon State University, the GEMM Lab is also entering into unchartered waters by expanding its focus to a new species outside the lab’s previous research portfolio. This project – which will be the focus of my thesis – will assess the potential reintroduction of sea otters to the Oregon coast through an examination of available habitat and ecological impacts. Before I explain how this project came to fruition, it’s important to understand why sea otter reintroduction to Oregon is relevant, and why this step is important to advance the conservation of these charismatic species.

While exact historical populations are unknown, sea otters were once abundant along the coasts of northern Japan, across Russia and Alaska, and down North America to Baja California, Mexico[1]. In the United States, specifically, sea otters were native to coastal waters along the entire west coast – including Oregon. However, beginning in the 1740’s sea otters were subject to intense and unsustainable hunting pressure from Russian, British, and American entrepreneurs seeking to sell their highly-valuable pelts in the lucrative fur trade[2].  Historical records suggest these hunters did not arrive in Oregon until the 1780’s, but from that point on the sea otter was exploited over the next several decades until the last known Oregon sea otter was killed in 1906 at Otter Rock, OR[3].

Pictured: Sea otter hunters near Coos Bay, OR in 1856. Photo Credit: The Oregon History Project.

After decades of intense pressure, sea otter numbers dropped to critically low levels and were thought to have gone extinct throughout most of their range. Luckily, remnant populations persisted and were later discovered in parts of Alaska, British Columbia, California, and Mexico beginning in the 1910’s. Since then sea otters have been the focus of intense conservation efforts. With the goal of augmenting their recovery, the Alaska Department of Fish and Game lead a series of translocation projects, where groups of sea otters were transported from Alaska to unoccupied habitats in Alaska, British Columbia, Washington, and Oregon (Note: these were not the only sea otter translocations.)1.

Pictured: Sea otters on glacier ice, northern Prince William Sound, Alaska. Photo Credit: Patrick J. Endres/AlaskaPhotoGraphics.com

Fun Fact: For a marine mammal, sea otters have surprisingly little blubber. Luckily, they also have the densest fur of all animals – an estimated 1,000,000 hairs per square inch – that helps to keep them well-insulated from the cold.

Many of these projects are considered successful as sea otter populations grew, and continue to expand today. With a significant exception: sea otters mysteriously disappeared shortly after reintroduction into Oregon waters and the translocation effort failed. Many hypothesized what could have gone wrong – natural mortality, dispersal, conflicts with humans – but few have concrete answers. Aside from occasional reports of strandings and sightings of sea otters in Oregon coastal waters, no resident populations have formed. This is where my thesis project comes in.

Pictured: Cape Arago, OR – one of the unsuccessful translocation sites along the Oregon coast. Photo Credit: TravelOregon.com

With renewed interests from scientists, tribes, and the public, we are now revisiting this idea from a scientific perspective. Over the next two years, we will work to objectively assess the ecological aspects of sea otter reintroduction to Oregon to identify and fill current knowledge gaps, which will help inform decision-making processes by environmental managers. Throughout this process we will give consideration to not just the ecology and biology of sea otters, but the cultural, economic, and political relevance and implications of sea otter reintroduction. Much of this work will involve working with state and federal agencies, tribes, and other scientists to gain their insights and perspectives, which we will use to shape our research questions and analyses.

The process to move forward with bringing sea otters back to Oregon will no doubt take great effort by a lot of people, consultation, patience, and time. To date, we have been reviewing the relevant literature and meeting with local experts on this topic. Through these activities, we have determined the types of questions and information – suitable habitat and potential ecological impacts – of most need to managers. My goal is to conduct a meaningful, applied project as an objective scientist, and by gaining this type of feedback at the outset, I am to help managers make better-informed decisions. I hope my thesis can serve as a critical starting point to ensure a solid foundation that future Oregon-specific sea otter research can build from.

References:

[1] Jameson et al. 1982. History and status of translocated sea otter populations in North America. Wildlife Society Bulletin. (10) 2: 100-107.

[2] The Oregon History Project: Sea Otter. Accessed September 2017. <https://oregonhistoryproject.org/articles/historical-records/sea-otter/#.WamgT7KGPIU>

[3] The Oregon History Project: Otter Hunting. Accessed September 2017. <https://oregonhistoryproject.org/articles/historical-records/otter-hunting/#.Wa2TCLKGPIU>