The case of the sea lion: stranding events linked to domoic acid outbreaks

By Sophie BernsteinMLML Ichthyology Lab

When I moved to the Monterey Bay area for graduate school, I found myself most excited to be immersed in a new ecosystem. I couldn’t wait to learn about what the Monterey Bay was known for: the kelp forest. But I never considered the marine life I could see from shore until my scientific diving course, when we would spend several hours a day loading and unloading boats near Moss Landing Harbor. I felt like a little kid in an ice cream store, excited by all the resident sea lions perched on the dock and nearby boats! Needless to say, as an East-coaster, I was in awe. Meanwhile, the Californians who surrounded me did not look twice. Whereas I thought these sea lions were outrageously cute, and had never seen something like this in the wild, my peers simply rolled their eyes at the barking and obnoxious smell coming from the large animals.

Soon enough, I came to realize that California sea lions are a commonly observed, charismatic marine mammal found along the entire California coast. They are top predators in the local ecosystem, and spend extensive amounts of time at sea foraging on a variety of prey items. Common food for these sea lions include anchovies, sardines, squid, and salmon. When not actively feeding, sea lions may be found on shore breeding in groups called rookeries. A single breeding site can be home to several hundred breeding individuals, with one large male dominating the pack! Because they are such large predators who spend time on coastal shores, they are highly visible to the public.

Rookeries are not the only location where sea lions are seen in large numbers onshore. Every few years, sea lions strand in high numbers along the coast. This is particularly noticeable to the public, because when stranded, they displaying incredibly abnormal behavior, such as excessive head weaving, seizures, or even unusually large mortality events. Unfortunately, mass sea lion strandings usually indicate a larger problem occurring in the marine system: harmful algal blooms.

Red tide events, which cause coastal waters to appear red and make the headlines in California newspapers, are one type of harmful algal bloom visible by the naked eye. Another type of bloom that is not necessarily visible in the water itself causes mass sea lion stranding events along the California coast. These blooms are caused by a different type of algae known as Pseudo-nitzschia, and are capable of producing a harmful neurotoxin called domoic acid (DA).  Similar to a canary in a coal mine, California sea lion stranding events are often the first indicator of a domoic acid outbreak.

The most recent DA events were in 2015-2016 and 1998 and both coincided with unusually warm oceanographic conditions. These warm oceanographic conditions are characterized by a decreased supply of cold, nutrient rich water (scientifically known as ‘upwelling’), resulting in water that is comparatively warmer and depleted in nutrients. The changes in upwelling alter how the larger ecosystem functions, by changing the distribution and amount of prey available. Major DA events occur rather infrequently because they require a specific combination of environmental conditions, but when they occur, they are visible to the public. Similar to other threats to marine ecosystems, these stranding events are tied to climate change. The frequency of DA events and marine mortality events may increase as climate change pressures alter upwelling patterns, creating environments prone to toxic outbreaks.

But if sea lions are top predators in California waters, how and why would a tiny algae cell impact them? While we don’t know yet for sure, scientists think sea lions are impacted by domoic acid through the food web. The Monterey Bay ecosystem is amazingly rich. It is home to thousands of fish and invertebrate species, all of which are connected to each other through predator-prey dynamics. For example, a sea lion may eat a squid, which eats smaller invertebrates and phytoplankton. Through this chain, sea lions and the phytoplankton come in contact.

Scientists recognize that sea lions are exposed to DA through these food chain connections. Sea lions are opportunistic feeders who consume a variety of prey items, including anchovies. Anchovies feed directly on algae and other phytoplankton. Since anchovies are important prey items for predators throughout California, the sea lions who consume them might be directly exposed to DA.

Yes, we’re talking about the same anchovy that may be sitting on your pizza! Anchovies are one of the largest fisheries in central California that contribute > 13 million pounds to commercial fisheries. This creates another question: Does DA threaten seafood consumers? Indeed, humans can be exposed to DA through the same food web connections that make sea lions vulnerable.

An important remaining question is: where are sea lions foraging when they’re exposed to DA? Scientists at The Marine Mammal Center have been researching related topics based on the stranded animals they respond to. Researchers have found that DA toxicity in sea lions can result from ingesting prey items which have accumulated DA, but where were these prey items consumed? And what is the relationship between ocean warming events, climate change, and DA outbreaks? With a better understanding of where prey items accumulate DA, monitoring agencies can more adequately test high risk regions, and increase the chances of detecting a toxic event early on rather than waiting for another biological indicator, such as mass sea lion stranding and mortality events.

To learn more about how The Marine Mammal Center is researching and helping during DA stranding events, check out this article.

CSI: Marine Mammal 🐋 – A day in the life of an MLML stranding responder

By Lauren Cooley, MLML Vertebrate Ecology Lab

The hotline rang at 2pm and I quickly ran across the lab to grab the phone, excited to find out what new adventure awaited me. “Moss Landing Marine Laboratories Stranding Network, this is Lauren,” I answered.  The caller had been out for a walk on Del Monte Beach in Monterey, California and had stumbled upon a deceased California sea lion. He relayed to me his location and a brief description of the animal. I thanked him for reporting the sea lion to our hotline, packed up my equipment and headed out the door, excited for another glamorous (or maybe not) day of marine mammal field work!

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Navigating a changing world: The challenges giant whales face as they search for bluer pastures

by Jenn Tackaberry, MLML Vertebrate Ecology Lab

As a marine biologist, part of my job is to study the behavior of whales and how they interact with their environment. Many projects I am involved in are long-term (40+ years) studies that follow individual whales throughout their lives. Long-term projects allow researchers to document how whales have reacted to changes in their environment in the past and how that affected the population as a whole. These data can help determine how whales are responding to climate change and how their response may affect their long-term survival.

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Listen Up! Brings Marine Science to Monterey-Area Schools

By Brijonnay Madrigal, MLML Vertebrate Ecology Lab

AR web Bri.jpgThis week's post comes from grad student Bri Madrigal. Bri recently started her own K-12 outreach program called Listen Up! to get kids interested in science and teach about the importance of acoustics in the marine environment.

I love working with children. They are enthusiastic and inquisitive, and I am always so amazed by how much they can absorb and learn. From a young age, I knew I wanted to become a marine biologist and inspire children to be interested in science by exposing them to new subjects and teaching them about the ocean. As marine scientists, we realize the importance of ocean conservation and we want people to make changes in their daily habits in order to maintain healthy oceans and healthy ecosystems.

But first, we need to make people care about the ocean. How do you do that? One way is by connecting people to the amazing animals that live in the ocean. I believe that marine mammals like whales, dolphins, and other charismatic megafauna, are an avenue to tap into peoples' hearts and inspire them to care about our oceans. When these values are established as children, I believe this will make a more profound impact on how they perceive environmental issues, influence their daily habits and influence their vote as adults to make an impact on ocean conservation.

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Who Are the People Who Run Towards the Stinky Beach Carcass?

IMG_6430By Sharon Hsu, Vertebrate Ecology Lab

My initiation to the MLML Marine Mammal & Sea Turtle Stranding Network was by fire. Actually, by a 200-pound dead harbor seal that we had to drag up Spanish Bay and load into the backseat of Jenni’s Ford Focus, amongst an onslaught of concerned tourists who had just paid to take a leisurely drive down one of Monterey’s most beautiful roads. Surprisingly, despite all the awkward and concerned staring, only a handful of people approached to ask what we were doing. I assume that, like me, everyone else was too shy to ask what the hell we were doing and will forever wonder about that big blue body bag that was suspiciously getting pulled off the beach by two women in flip-flops.

As official dead-thing-touchers (yes, we have the permits to do so – and yes, you have to have a permit to do so), we find that only a few brave individuals will approach to ask questions about what we are doing, and I can only assume that others might be left wondering why two people in a kayak were sampling blubber from that dead humpback whale off Lover’s Point or putting that dead sea lion pup into a plastic bag in front of a class of baby kayakers on Del Monte Beach. So here are the answers to the top six questions we get:

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Working with “mer-dogs” aka California Sea Lions

mason cole profile pictureBy Mason Cole, Vertebrate Ecology Lab

This post is part of Dr. Gitte McDonald’s marine mammal class blog series.

MLML Director Dr. Jim Harvey likes to say that harbor seals are the “cats of the sea”.  If that’s true, then California sea lions are the rambunctious young puppy dogs of the sea.  But not those little baby fluff-ball puppies; no, more like that almost-full-grown, 90-pound wrecking ball.

Many a commercial fisherman would cringe to read this, but I love working with sea lions.  They earned their place in my mind as “mer-dogs” for more than just their energy and enthusiasm: they are also particularly intelligent, with striking personalities and an impressive capacity to learn trained behavior.

Nemo derpy head strap 2
Nemo with his prize herring - good boy!  (Photo credit: Mason Cole.)

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Disentangling a Difficult Situation

By Bradley Wilkinson, SJSU Graduate Student

This post is part of Dr. Gitte McDonald's marine mammals class blog series.

The lighthouse on Southeast Farallon Island offers an amazing view of the surrounding Gulf of the Farallones for whale observations. Photo: Bradley Wilkinson

I had never seen so many whales before in my life. Standing atop Southeast Farallon Island, bracing against the rails of a relic lighthouse, I commanded an unequaled view of the surrounding seascape. To the northeast, Pt. Reyes stood before Bodega Bay, forming an extreme limit to my far-reaching gaze. The Golden Gate Bridge was blatantly obvious to the east, framed nicely against the hustle and bustle of San Francisco. To the south and west, endless blue. Huge container ships waiting for port entry outlined the invisible lanes of industrial traffic.

But the whales. The whales were everywhere, stealing the proverbial show. Spouts popped off in every direction, grouped in conglomerates of nearly a dozen on occasion. In total, I counted over eighty whales of three species that afternoon, in only one hour of effort. The extreme productivity of the Gulf of the Farallones had attracted this concentration of cetaceans, a predictable patch of food nested with the dynamism and variability of the oceanic environment. But just below the surface, sharing the water column with swarms of krill and schools of anchovy, lurked a lethal threat. I had seen them while onboard the sailboat to the island. Although only a small part of each one was visible at the surface, I knew much more lay beneath. This paradoxically obvious yet invisible threat was both insipid and borne of abandonment. Derelict fishing gear.

Humpback whale with damaged flukes. This animal most likely had these injuries inflicted by an entanglement event that cleaved the tail. Photo: Bradley Wilkinson

And of course, threats breed consequence. A few days later, I witnessed this firsthand. While conducting a seabird diet assessment on another end of the island, a group of whales fed a bit offshore. Taking a break to observe the diving giants, one of the members of our party suddenly exclaimed that an individual in the feeding group was missing a tail. Surely not, we thought. Perhaps the flukes had been seen at an odd angle, performing an optical trick. We studied the group further. Then we all saw it; a whales spouted, rolled, and began to dive. As it arched its back and raised its tail, it was all too obvious that both of the flukes of the animal were gone. It was as if they had been sheared off by a gigantic pair of scissors. But of course we knew that wasn’t the case. The most likely candidate was an entanglement event with derelict fishing gear.

Unfortunately, this is not a rare occurrence along the California coast. In fact, statistics point to 2016 as the most frequent year of entanglement events on record. Whales, unable to detect the long lines of nylon suspended in the water, become trapped in gear as it wraps around body parts ranging from mouths, to flukes, to flippers. Fortunately, there are people who are trying to help. California Whale Rescue is a group of dedicated professionals who not only free entangled whales when reported, but work with both the industry and the public to solve this issue from the start. Together, they look to help stem the tide of increasing entanglements. To learn more about this group and how you can do your part to prevent whale entanglements like the one described here, please visit Thanks also go to Point Blue Conservation Science and Farallon National Wildlife Refuge for aspects of this post.

A passing blue whale takes a breath, leaving a signature blow. Photo: Bradley Wilkinson

A Day on the Water Tagging Whales

IMG_20170428_070106_011By Brijonnay Madrigal, Vertebrate Ecology Lab

This post is part of Dr. Gitte McDonald's marine mammal class blog series. 

Tagging marine mammals is a highly difficult procedure and a skill that requires extreme finesse from scientists. Due to the high speeds that large baleen whales travel and the short amount of time their dorsal side is exposed at the surface, it requires a quick deployment and impeccable timing. When a whale is at the surface, it usually comes up for a few breathes before diving down. Therefore, there are only a few moments when tagging is possible. Being able to participate in such fieldwork was very exciting for a group of MLML students. This April, students in MS 211: Ecology of Marine Turtle, Birds and Mammals had the opportunity to aid Dave Cade in his research in Monterey Bay.

We departed on the John Martin early on a clear, sunny morning. Our role that day was as the support boat for the tagging boat, the Musculus. Aboard the Musculus was a small tagging team comprised of Dave, the tagger, and John Calambokidis, the boat driver. John Calambokidis, a research biologist and founder of the Cascadia Research Collective, is one of the world’s most experienced whale researchers. The Musculus remained in close proximity to the Martin as the support vessel and we maintained corresponded with the tagging team as the day proceeded.

A group of students in the marine mammal field class enjoy observing whales from the top deck of the John Martin [Photo Credit: Jennifer Johnson, MLML student]

The tagging boat is approaching two humpback whales to deploy a tag under the NMFS permit # 20430 and ONMS permit MULTI-2017-07 [Photo Credit: Jennifer Johnson, MLML student]
We scanned the horizon for any blows to indicate the whale’s presence. Alas… there she blows!!! Once a whale was spotted, the Martin traveled towards the animal to see if it was a potential tagging candidate. A group of students were situated at the top deck of the boat with the best view in order to take photos for photo identification purposes. Pictures taken were compared to photos in a photo identification guide of known humpback whales in the Bay. Students were able to compare identifying features like dorsal fin shape and flukes patterns to identify specific individuals. Detailed notes were recorded on number of whales in the area, distance between whales and the boat and tag information.

MLML students Heather Barrett and SJSU student Olivia Townsend record data from the top deck of the John Martin [Photo Credit: Jennifer Johnson, MLML student]
Although we were constantly on alert for whales, the students on the support boat had various roles. A few students ran the echosounder, an instrument that uses sonar to determine depth and produced pings at three frequency ranges in order to map the prey within the water column. Once a whale was found, the Martin traveled in small and large square shape tracks around the whale, echosounder pinging continuously, in order to map prey in the area around the whale.

dropping CTD_Mar2017
MLML student Jennifer Johnson and MLML faculty member and instructor of the course, Gitte McDonald, deploy the CTD [Photo credit Mason Cole]
During the day, we had the opportunity to witness the tagging process from a distance. As a whale surfaces, the boat must be positioned in a precise manner and approach the whale at a fast-enough speed to come alongside the whale parallel for the tagger to place the suction cup tag on an animal the size of a school bus. As the whale surfaced, the boat sped up to get in line with the whale. The tagger extended the pole with the tag attached to the end and…WHOMP! The tag hit the whales skin and detached from the pole. The suction cups on the bottom of the neon colored tag kept it adhered to the whale’s back. Success!! Once the tags were on the animals, students used telemetry to find the tagged animal. The tags emitted a ping at a specific frequency which the telemetry instruments could detect. With arm extended, students would move the instrument 360 degrees to hear beeps. When the beeping got louder, this indicated the presence and directionality of the tag. At the end of the cruise, CTD deployments were also conducted to collect salinity, temperature, and dissolved oxygen levels. As we headed back to Moss Landing harbor at the end of the afternoon, I think all the students could agree that it was a very fulfilling day. Not only did we contribute to ongoing whale research, but we had the opportunity to aid a fellow graduate student with his PhD work that will yield insightful information about predator-prey dynamics of humpback whales in Monterey Bay. This collaboration between Hopkins Marine Lab not only benefits the Moss Landing students that are able to partake in local research efforts but also gives Hopkins the opportunity to operate out of the Moss Landing harbor and have access to the MLML vessels. Goldbogen lab research is conducted in close collaboration with MLML director, Jim Harvey, and research faculty Alison Stimpert.

SJSU student Brad Wilkinson is stationed at the bow using telemetry to find the location of the deployed tag [Photo Credit: Jennifer Johnson, MLML student]
Dave Cade, a PhD student in the Goldbogen Lab at Stanford, studies predator-prey dynamics of humpback whales and ecosystem ecology in Monterey Bay. The goal of his research is to study the kinematics and success of foraging Humpback whales on different prey types. To do this, he used suction cup tags to collect accelerometer, magnetometer, basic audio and gyroscope data. This is a collaborative project involving researchers from Hopkins Marine Station, Cascadia Research Collective, and Moss Landing Marine Laboratories. This work was completed under permits NMFS permit #20430 and ONMS permit MULTI-2017-07.

Monterey is Expensive: The cost of disturbance

By Heather Barrett, Vertebrate Ecology Lab

Heather Barrett recording sea otter behavior during a disturbance scan.

The crisp morning begins with stretches, a barrel role here and there, and one of the members breaking off to search for a crab breakfast. The raft bobs as the distant boat wake lifts each otter in a wave; rocking them gently in a water cradle. There are five mothers with cotton-ball pups that begin the tedious nursing and grooming process, lifting the plush bodies and breathing warm air in to their Einstein frizz. But the calm morning routines will soon be disrupted and turn to disorder. The bright colored beasts have arrived, aiming the kayak bows towards the otter raft, paddles drumming as they hit the surface of the water.

Most human disturbance is unintentional. However, this naiveté does not eliminate the potential behavioral or physiological consequences for wildlife. Simply our presence, especially when too close, can impact certain species by initiating a stress response. Stress hormones release, causing an increase in heart rate, rise in blood pressure, suppression of feeding and reproduction, and modulation of immune function 1. This is critical in acute stress response, for it allows for a quick reaction during a potentially threatening situation. But what if this becomes chronic?

Sea otter raft that experiences high human traffic at Jetty Road, Moss Landing.

Chronic stress leads to prolonged exposure to these stress hormones, which can cause muscle wasting, bone thinning, reproductive failure, and immune deficiency 1. These physiological responses are usually undetected in wildlife, which can portray a false sense of acceptability for disturbance 2. Behavioral responses tend to be clearer since they are visually detectable. Individuals will become alert, move away, and show avoidance or even aggression 3. All which have an energetic cost. With these varying responses, why is disturbance particularly a concern for sea otters?

As a keystone species, sea otters have a disproportionate effect on their surrounding environment, enhancing local biodiversity 4. They exhibit this strong influence on their coastal community through their voracious appetite, controlling grazer populations 4. With little fat storage and only dense fur to keep warm, sea otters use their high metabolic rate to maintain their internal temperature in a cold marine environment. Since they use energy to keep warm, they must consume a quarter of their body weight in food each day to fuel this heat production 5.

So picture an exhausted sea otter mother: using energy for lactation, heat production, foraging, and pup care; imagine what it would be like to have constant disturbance from people recreating in the bay. If already living near physiological limits, what is the energetic consequence when human disturbance increases the cost? To answer this, it is important to understand the types of disturbance and create a baseline of behavioral response.

Abram_Sea Otter Photo
Female sea otter illustrating behavior to look for when recreating near sea otters: Head raised and alert. This means you are too close.

Sea Otter Savvy is spearheading the sea otter disturbance data collection with citizen science and educating the public through outreach programs. As a graduate student at Moss Landing Marine laboratories, I am thrilled to participant in the data collection and honored to use this information. I will couple this with the previously collected metabolic data from University of California Santa Cruz 5,6 to investigate the energetic cost of disturbance of sea otters in Monterey Bay.  This unique collaboration, and inclusion of graduate research, benefits the scientific community, the public, and can provide information to agencies making wildlife policy and management decisions.

If you are interested in learning more about Sea Otter Savvy and the current disturbance project, please visit the website:


  1. Hill, R.W., Wyse, G.A., Anderson, M. and Anderson, M., 2004. Animal physiology (Vol.2). Massachusetts: Sinauer Associates.
  2. Sorice, M.G., Shafer, C.S. and Scott, D., 2003. Managing endangered species within the use/preservation paradox: understanding and defining harassment of the West Indian manatee (Trichechus manatus). Coastal Management, 31(4), pp.319-338
  3. Gill, J.A., Sutherland, W.J. and Watkinson, A.R., 1996. A method to quantify the effects of human disturbance on animal populations. Journal of appliedEcology,pp.786-792.
  4. Estes, J.A. and Palmisano, J.F., 1974. Sea otters: their role in structuring nearshore communities. Science, 185(4156), pp.1058-1060.
  5. Thometz, N.M., Tinker, M.T., Staedler, M.M., Mayer, K.A. and Williams, T.M., 2014. Energetic demands of immature sea otters from birth to weaning: implications for maternal costs, reproductive behavior and population-level.
  6. Yeates, L.C., Williams, T.M. and Fink, T.L., 2007. Diving and foraging energetics of the smallest marine mammal, the sea otter (Enhydra lutris). Journal of Experimental Biology, 210(11), pp.1960-1970.

Life on the beach: My first field season as an elephant seal researcher

By Kate High, SJSU undergraduate

Third installment of the blog series by students enrolled in MS 211: Ecology of Marine Mammals, Birds and Turtles with faculty member Dr. Gitte McDonald. 

Mel re-sighting elephant seals. Photo source: Kate High


Interning in the Vertebrate Ecology Lab at Moss Landing Marine Laboratory this past year has given me countless opportunities to participate in activities most undergraduate students at SJSU might not know exist. I began training for elephant seal research at Año Nuevo State Park at the beginning of January. Even though I’ve had a lot of field experience, I can honestly say I have never been more nervous about a field day in my life.

I was getting trained to help with tag re-sights as well as weaner weighing. This was my first time working with pinnipeds and of course we were working with the largest North American species. There are a couple things that stick with me from that first field day. The first one is Dr. McDonald’s ultimate rule “First is our safety, then the animal’s, then comes the science.” The second was being surprised that most males were calm and paid little to no attention to us. This is in contrast to some females, who made my heart jump because of a reaction I got from some seals.

The first time out to Año Nuevo, your head feels like it’s spinning around because there’s so much activity on the beach. You have to be alert and aware of your surroundings, all while trying to collect accurate data.  But through all the chaos there are moments when you can appreciate the beauty of the surroundings and the excitement of the work.  Before you know it, the season has wrapped up and the beach at Año Nuevo seems empty.

Elephant seal sunrise (Photo source: Kate High)

There are many memories I will cherish from my first season at Año. I’ll never forget walking in the crisp air as the sun was rising, and being able to both hear and see the male elephant seals trumpeting in the distance. There were weeks where it seemed as if you couldn’t walk anywhere on the beach because there were so many females and pups packed in. I loved doing tag re-sights of pups and coming across a group of deep sleepers that happened to be snoring, or weaners that would accidentally roll down a hill. I’ll always remember my individual trip out with Dr. McDonald as a great chance to ask questions and to hear about her experiences in the field. Although some days it was windy and raining and we were wet and cold, being out in the field and having this experience was a privilege.

Some might wonder if the researchers doing field work out at Año Nuevo get tired of their work out there - my answer would be an immediate “No.” The group of researchers and volunteers I worked with were always enthusiastic and supportive, and willing to teach. I was always ready for field day as soon as my alarm went off. I would tell myself before I went out each time, “A million people would kill for this experience and to be in your shoes. Don’t take today for granted.” And as cheesy as it sounds, Año Nuevo never got less magical for me.