A Puzzle with Missing Pieces: Marine Mammals in the Gulf

With fewer than 50 individuals remaining, Rice’s whales have the distinction of being one of the world’s rarest whales. They are also the only known baleen whale that live in the Gulf of Mexico year round – the other 21 whale and dolphin species in the Gulf have teeth instead of the bristly baleen plates that filter plankton and small fish from salty ocean waters. 

However, despite their unique life history, Rice’s whales are not as well known as some of their more popular whale cousins, such as the North Atlantic right whales who are named and tracked closely by scientists and coastal residents. 

“The awareness of Rice’s whales was remarkably low until recently,” said Lance Garrison, a research fishery biologist for NOAA’s Southeast Fisheries Science Center located in Miami, Florida. “Sports fishermen would see them, maybe, if they are looking.”

Garrison studies Rice’s whales with the goal of finding ways to protect them in the increasingly industrialized Gulf. But one of the major barriers he faces is the lack of information about this newly named species – without an understanding of their abundance, distribution, and behavior, it is difficult to fully determine the status and health of these animals. 

This issue – a lack of data about the 21 marine mammal species in the Gulf of Mexico – is a dilemma shared by many researchers in the region. Marine mammal researchers are making sure to leverage partnerships and communicate their findings to help inform each other’s research. Each study becomes a piece of the increasingly complex puzzle of marine mammal conservation in the Gulf. 

During the Deepwater Horizon oil spill, more than four million barrels of oil were released into the Gulf over an 87-day period. Oil response and recovery teams used nearly two million gallons of dispersants, chemicals used to dissolve the oil, to break the slicks up into small oil droplets, which then collected in ocean sediments. Oil also coagulated below the surface, creating clouds of oil droplets that became obstructions for marine animals nearby. Though public concern after the spill often focused on the 1,313 miles of coastline impacted, the Gulf’s open ocean was exposed to the largest percentage of toxic pollutants. 

“I don’t think people understood the full footprint of the event,” said Tracey Sutton, a professor at Nova Southeastern University and lead researcher of the DEEPEND project. “If you look at the dissolved fraction of the oil spill, it was basically the eastern half of the Gulf of Mexico. It was an enormous footprint, bigger than the public perception, I think. There is a real possibility that stuff is still being turned over [circulated] in the deep Gulf even today.”

“The animals were just not able to reproduce like they should have.” - Lori Schwacke, director for Scientific Programs for the Marine Mammal Commission

Today, evidence of oil contamination can be seen in the chronic conditions of some of the Gulf’s marine mammals, such as inshore dolphin species.

Lori Schwacke is the director of Scientific Programs for the Marine Mammal Commission. She previously worked for NOAA and was involved in early health assessments of marine mammal populations after the Deepwater Horizon oil spill. She left NOAA in 2016 to join the National Marine Mammal Foundation, where she continued her research in the Gulf as director of the Consortium for Advanced Research on Marine Mammals Health Assessment. A decade of her career was consumed assessing the aftermath of the spill on marine mammal populations. During the last health assessment she conducted in 2018 on dolphins in Barataria Bay, Louisiana, chronic issues were still present. 

“What we found was the dolphins that had been alive at the time of the spill, some of which we had sampled multiple times, still had a high prevalence of lung disease,” Schwacke said. 

Schwacke also observed reproductive impacts. 

“We expected the population to decline after the spill, up to about nine or 10 years, before it would actually start to turn around because there were reproductive impacts as well,” Schwacke said. “The animals were just not able to reproduce like they should have.”

But lingering impacts from the Deepwater Horizon oil spill are not the only threats that marine mammals face in the Gulf. Schwacke listed a slew of other stressors such as entanglement in fishing lines and nets, boat and ship strikes, mercury and other contaminants, industrialization, sediment and freshwater diversions from the Mississippi River, harmful algal blooms, morbillivirus (a virus that can cause respiratory issues and brain swelling in dolphins), and other oil spills like the Taylor Energy spill that has been slowly leaking into the Gulf over the past 14 years. 

While some threats are unique to the Gulf, “some of the threats are the same no matter where you go,” Schwacke said. 

Researchers have begun to assess the impacts of multiple stressors on marine mammals in the Gulf. Ryan Takeshita, a researcher with the National Marine Mammal Foundation, was awarded nearly  $80,000 by the NOAA RESTORE Science Program in 2021  to plan research on the topic. Takeshita’s research asks how to reduce uncertainty about the effects of both natural and man-made impacts on bottlenose dolphins living off the coast of Houston. Part of his process has been to bring together a working group of researchers, managers, and other stakeholders to design a project that can answer this question. 

Schwacke said that projects like this that work to develop new methods and approaches to collect information on marine mammal populations are a necessary next step before researchers and managers can begin to pinpoint solutions, and this is especially true for animals living offshore.  

“We think we have an idea of what happened with offshore populations just based on what we extrapolate from the dolphin studies, but it’s really difficult to know because you can’t get hands-on with offshore species,” Schwacke said. “Hopefully, in the future, there will be improved diagnostic tools and approaches to be able to tell more from the offshore species.”

During the Deepwater Horizon oil spill, about 50 percent of Rice’s whale habitat in the Gulf was covered by oil. Before the oil spill, the only information available on the Rice’s whale, which was formerly considered to be a member of Bryde’s whale species, came from historical survey data. After it was designated as an endangered species in 2019 and determined to be a unique species in 2021, genetically distinct from the Bryde’s whale, urgency heightened to understand the ecology of the species. The timing of this new designation aligned with a  $2.3 million research award  Garrison received from the NOAA RESTORE Science Program in 2017 to study the whales and their role in the larger Gulf ecosystem.

With fewer than 50 individuals in the wild, gathering information about the species can be especially difficult. And once an individual is located, there are limits on how information can be collected. 

“Coming from a fish background – and I will put it in the grossest sense – you drag a net, you pull up 1,000 fish, and you cut them open and you see what there is,” Garrison said. “You can’t do that with whales. There’s just a lot of challenges along the way of studying them and not causing harm.” 

Some insights are clearly evident by research that has been conducted thus far, however. For one, Rice’s whales have an extremely specialized diet. They consume a small number of prey species, and if those prey species decline, the whales struggle to meet their energetic requirements. 

“What we found almost immediately was this really large decline in abundance of just about everything." - Tracey Sutton, professor and deep-sea researcher

The body conditions of observed whales in the Gulf indicates that many individuals are just barely getting by. 

“Their prey resources are very patchy,” Garrison said. “Basically all day long, all they are doing is diving and feeding. When they are at depth, they are making one or two feeding attempts and then coming right back up, breathing, and going right back down. So they are working all of the time, and you see this variability in their body condition.”

Professor and deep-sea researcher Tracey Sutton and his team are looking at the other side of this environmental trend with their DEEPEND project, which received over  $2.7 million in support from the RESTORE Science Program in 2019 . This funding followed earlier support from the Gulf of Mexico Research Initiative, first awarded in 2015, and NOAA’s Office of Response and Restoration, first awarded in 2010. 

For the past decade, Sutton and his team have embarked on open-ocean expeditions in the Gulf of Mexico to identify trends in the fish, shrimp, and cephalopods (such as squid and octopus) that live offshore. Researchers drop a net to deep sections of the Gulf, reaching a depth of 1700 meters, and collect specimens to identify. Many of the animals they found have never been discovered before, and with 90 percent of the Gulf’s volume concentrated in the deep ocean, the team has a lot of saltwater to cover. 

“We have found about 900 species of fishes, and 186 of those are new [observations] for the Gulf,” Sutton said. “There aren’t as many shrimp and squid species, but the numbers that we have collected in the Gulf are still huge for each of those taxa as well. And we are still finding new species on every cruise, so it’s not like we know everything down there, we just know what we have come across to date.”

To collect specimens, the researchers use a net that they can open and close on demand at different depths, which allows them to analyze the movement patterns of deep-Gulf species as they migrate up and down throughout the day. Since Sutton’s team began sampling in 2010, just after the Deepwater Horizon oil spill, they have worked to create a baseline for deepwater animals and, over time, track whether their populations are recovering.

“What we found almost immediately was this really large decline in abundance of just about everything,” Sutton said. “For some of the shallow living things, the numbers were about the same but for most of the deeper living things, the numbers went down substantially.”

Sutton’s crew found declines in abundance consistently from cruise to cruise, indicating that the reproductive abilities of many deep-sea species continue to be impacted more than a decade after the oil spill. They also measured polycyclic aromatic hydrocarbons – a chemical compound of oil that has been found to impact reproduction, development, and immunity – at sublethal levels (which doesn’t kill organisms but harms them) in shrimp and fish eggs as recently as 2018. 

“That’s why the RESTORE work is so important to us – we want to see if it recovers at all,” Sutton said. “We are still to this day waiting to see that recovery. It has not happened yet.”

Declines in the abundance of deep-sea animals have likely affected marine mammals and other long-living marine animals that rely on deepwater fishes and squid as staples of their diet. Any reduction in their access to those species can place them on what Garrison calls “a nutritional knife edge.” 

Sutton and Garrison communicate frequently about their research projects, comparing findings and generating new questions. For Sutton, making his team’s deepwater survey data available for managers and others to use has led to surprising connections, but has also led to challenges. 

“We are really seeing that our data matter to other people in ways we didn’t envision,” Sutton said. “It was a real challenge for us to figure out how people can use data for a resource that is not actually fished, or that most people don’t even know is out there. How do we now inject that into the bigger picture?”

The northern Gulf of Mexico is a highly industrialized ocean body with five of the 10 major water ports in the U.S. Cargo ships make over 100,000 trips a year in the Gulf basin, carrying billions of tons of cargo. The lower Mississippi River alone is considered the largest port complex in the world with about 12,000 trips from deep draft cargo ships annually. Gulf oil rigs produce about 97 percent of oil and gas production in the U.S. Outer Continental Shelf. Seismic airguns, which blast a high-energy impulse every 10 to 12 seconds for days to months at a time, are also regularly used to map oil and gas reserves offshore. All of this activity leads to some of the highest chronic noise levels in U.S. waters, which can cause major disruptions for marine mammals like the Rice’s whale that frequent these areas.

“What that does for a baleen whale is it limits its communication space,” Garrison said. “They call it the cocktail party effect. If you are in a loud room, you have to talk louder to be heard, and it’s also kind of stressful.”

Because Rice’s whales feed on prey that is sparsely distributed, they may rely on communication from other whales to locate patches of available food. When industrial noise levels crowd the acoustic space in which whales and other marine mammals communicate, their vocalizations travel shorter distances, making it more difficult for them to relay information about food availability. 

Melissa Soldevilla is a research fishery biologist at the NOAA’s Southeast Fisheries Science Center in Miami, Florida. Soldevilla and her team received nearly  $3.6 million from the RESTORE Science Program in 2020  to use passive acoustic monitoring to gather information about both marine mammals and noise levels in the Gulf. The project is also supported by the Scripps Institution of Oceanography, a research organization that has been engaged in post-Deepwater Horizon monitoring work since 2010.   

"It’s hard to get anybody interested in trying to solve a problem that they don’t know exists." - Melisssa Soldevilla, reseach fishery biologist

“That's one of the great things when you are using passive acoustic methods is you are both monitoring the marine mammals and you are also monitoring the noise,” Soldevilla said. “You are getting information on both the natural resource – the marine mammals – as well as the human impact.”

Over the next five years, Soldevilla’s team plans to monitor 28 different sites in the Gulf – eight of which will be studied over a longer-term period. At each site, an instrument is positioned on the seafloor to record the acoustic signals within a specific frequency range. After a year recording ocean sounds, the research team pulls the instruments up and collects the recordings. They then use automated detectors to pull out sounds produced by marine mammals, such as echolocation clicks and other vocalizations. 

With that information, the team can run analyses on the abundance and density of marine mammals and can even identify specific species. The data also help researchers start to understand how animals are moving around different depths and locations. 

“Once we start understanding those density trends at specific sites, we can start combining those with the oceanography and do some modeling to understand what are the oceanographic drivers,” Soldevilla said. “We are hoping all of that information will better inform us as we are trying to move forward and restore these animals in the Gulf.”

The team has partnered with Mexican researchers to monitor southern portions of the Gulf of Mexico, where data on marine mammal abundance are even more limited than in the northern basin. Soldevilla is particularly interested in seeing if the monitoring sites in Mexican waters pick up calls from Rice’s whales. Historical whaling records from the 1600s indicate that Rice’s whales may have previously traversed waters in the southern Gulf. A major question is if more individuals from this endangered species can still be found there.  

“It’s like you have all these puzzle pieces, and yeah there are a lot missing, but you can put a few of them together." - Laura Engleby, marine mammal branch chief of NOAA Fisheries’ Southeast Regional Office

“I think one of the most exciting parts about this project is our ability to get into Mexican waters because until now that’s been this great unknown,” Soldevilla said. “It’s easier to get funding for NOAA to do surveys of marine mammals in our waters but looking at the other half of the ecosystem, we have just been missing that. We are really excited to start seeing our first datasets come from there.”

Soldevilla has seen the field of passive acoustics progress since she began working with this approach at the Scripps Institution of Oceanography in 2002. Since that time, the technology has gotten more advanced – researchers are now able to collect audio signals at higher frequencies, which requires a faster sampling rate and increased battery power. With increased power comes a greater ability to collect baseline data in new locations for species that were previously unmonitored, all of which is part of the groundwork that Soldevilla believes must be done to figure out the next steps for conservation. 

“I think, overall, the passive acoustics are more of the science rather than the solution,” Soldevilla said, “but I think if you are not aware of the problem, and you don’t have the data to say that there is a problem, then it’s hard to get anybody interested in trying to solve a problem that they don’t know exists.” 

Soldevilla’s research for the RESTORE Science Program is being leveraged by the Open Ocean Trustees for the Deepwater Horizon Natural Resource Damage Assessment Program to help develop voluntary partnerships focused on reducing the impacts of noise on cetaceans as part of a six-year, nearly $9 million restoration project selected in 2019.

“The data resulting from acoustic monitoring by both of these Deepwater Horizon projects will advance our ability to target noise reduction strategies and support resilient marine mammal populations in the Gulf of Mexico,” said Laurie Rounds, NOAA’s area lead for the Deepwater Horizon Open Ocean Restoration program.

As the marine mammal branch chief of NOAA Fisheries’ Southeast Regional Office, Laura Engleby has her dream job. Her interests were seeded as a child watching Jacques Cousteau interact with dolphins, and she spent her career moving from dolphin trainer to education director to a NOAA expert on marine mammals, while building a nonprofit organization dedicated to dolphin conservation on the side.

“I wanted to be in a place of decision making,” Engleby said. “I wanted to help decide where money goes. I thought that could be the best way I could help these animals.”

With 21 known species of whales and dolphins in the Gulf, it can be difficult to prioritize the conservation of all species at once. To better coordinate conservation efforts, researchers have identified a handful of focal species that they believe represent the needs of other species as well. By focusing on the needs of those few, they hope to capture the needs of the many. But in an environment full of uncertainty and constant change, Engleby said she gets worried that it may be easy to miss something.

“It’s like you have all these puzzle pieces, and yeah there are a lot missing, but you can put a few of them together,” she said. “These RESTORE projects are certainly adding many more pieces to add a little more clarity. We can start to see the bigger picture and understand more of what we may or may not be able to do and where we may or may not be able to do it.”

"What we have discovered is that the dolphins are a lot smarter than we are." - Michael Moore, director of the Marine Mammal Center at Woods Hole Oceanographic Institution

One beacon of hope is the introduction of new technologies that help make it easier to study marine mammals, such as a remote-tagging device being developed at the Woods Hole Oceanographic Institute that could help reduce the stress dolphins experience during health assessments. The project received over  $280,000 from the RESTORE Science Program in 2021  to develop and test this new approach to deploying satellite tags.  

“Dolphins, in order to put a tag on them, you typically have to capture them and restrain them and then put the tag on,” Engleby said. “If we could figure out this remote option, that would really open up this universe of possibilities and questions we can ask and get answers to.”

Michael Moore, the director of the Marine Mammal Center at Woods Hole Oceanographic Institution, is working with a team of researchers and engineers to develop this remote-tagging device called the TADpole, which stands for a tag attachment device on a pole. 

It works by using compressed air to insert a pin through the animal’s dorsal fin the moment the device makes contact. The researcher holds the device on a pole over the bow of a boat to reach a dolphin’s fin as it rides the waves. The interaction happens extremely fast. 

“Tens of milliseconds, and they are out of there,” Moore said. 

Dolphin satellite-linked tags are typically attached by capturing the animal in a net, bringing it onto a boat, and creating a small a hole through the fin for attachment with a plastic pin. Suction cup tags have also been used, but they don’t last as long as tags that are attached through the fin.

To make sure the tag works properly, Moore and his team first tested it in a lab on a dead dolphin recovered by a marine mammal stranding team. They met that benchmark without issue, but when it comes to attaching a tag to a living, wild dolphin that is moving quickly and cleverly, success becomes a bit more elusive. 

“We were able to make contact with the dorsal fins of bow-riding dolphins a number of times with previous iterations of this device, but what we have discovered is that the dolphins are a lot smarter than we are,” Moore said. “We thought initially, in our naive way, that the animal would accelerate from us when we were trying to get this device on a pole against the back of the dorsal fin. Well they didn’t accelerate, they just dropped and rolled.” 

The TADpole team includes Randall Wells, director of the Chicago Zoological Society’s Sarasota Dolphin Research Program, based at Mote Marine Laboratory on the Gulf Coast of Florida, who leads efforts to test the device on live dolphins.

Over the past few months, the team has made significant progress on the TADpole. The device has gotten faster and more efficient, and it worked successfully on living animals that were captured for health assessments in Sarasota Bay. But Moore acknowledges there is much work ahead before the device changes the game on how dolphins are tagged in the wild. 

“All kinds of people are attaching single-pin dorsal fin tags to dolphins, so the novelty of what we are doing is trying to do so without catching the animal first. That’s the challenge,” he said. “I don’t know anyone else who is trying to do that – probably for a good reason because it may not be doable, but we haven’t reached the end of our rope yet.”

Libby Fetherston-Resch, marine mammal restoration coordinator for NOAA Fisheries’ Southeast Regional Office, is a firm believer of combining information and rethinking approaches to get the most out of marine mammal restoration in the Gulf, even when the connections between projects are not obvious. 

“There’s not any super clear overlap in some of this work,” she said. “The individual efforts are not intrinsically linked but they are adjacent; they are touching. So how do we spend the time to think about each of us doing something slightly differently so the pieces line up and we get more out of it? I’m that person who is always like, ‘we can get one more sledding run in before the sun goes down.’ I think even just asking the question is really valuable.” 

“No one is built for as rapid an environmental change as we are experiencing and will experience over the next 20 years.” - Lance Garrison, research fishery biologist

In her career in the Gulf, Fetherston-Resch has pushed to expand what is considered ecological restoration and how funds intended for restoration after the Deepwater Horizon oil spill could be spent to better support injured marine life. 

“In the early days, we spent a lot of time laying down this path of information as restoration – knowledge about these offshore species helps you do better things for these species,” she said. “Now we think about data gap filling and data collection as an essential part of the restoration effort, which certainly wasn’t what came out of the gate.”

Now as a NOAA project manager, Fetherston-Resch and her team are working on a restoration project to aggregate marine mammal data in the Gulf with an online tool where researchers can input their information, combine it with other datasets, and access the findings of other projects. The hope is that people can play with the data and visualize information in new and different ways to help better design restoration, target management actions, and understand data gaps. 

“We are not going anywhere without that synergy, that’s where the insight is,” Fetherston-Resch said. “Without these kinds of partnerships and looking cleverly at how we try to line our work up to accomplish synthesis, we will never achieve insight. You can’t achieve it on accident. Hope is not a strategy.” 

The need to prioritize information gathering for these species is felt by others in the region as well. For Rice’s whales, Garrison hopes to establish a long-term monitoring program that focuses specifically on the species. The RESTORE Science Program’s investment in Garrison’s project was the first research award dedicated to understanding Rice’s whales specifically. Previous data on these animals was gathered during projects that were focused on other research questions and species. 

Research findings from Garrison’s project will feed into recovery plans and critical habitat designations in the future. NOAA Fisheries’ Southeast Regional Office has discussed developing an outreach strategy for the Florida panhandle to raise awareness of the presence of Rice’s whales in the region among boating communities. This strategy includes the opportunity to report vessel strikes to Rice’s whales on the “Whale Help” hotline.  

“We need to be able to keep track of these guys and understand how they are responding to their changing environment,” Garrison said. “No one is built for as rapid an environmental change as we are experiencing and will experience over the next 20 years.”

Climate impacts and other rapid environmental changes undoubtedly complicate the conservation puzzle for marine mammals and cloud pathways to clear solutions, but Engleby and those like her who are dedicated to conserving these animals are determined to do whatever they can to reduce stress on the Gulf’s dolphins and whales. 

“Anything we can do in that regard is beneficial and worth doing,” Engleby said. “We have one of the world’s most endangered whales, the Rice’s whale, in the Gulf of Mexico with an estimated 30 to 50 left. That’s a big deal. That’s going to be difficult. That’s a challenge. But that doesn’t mean we are not determined to do something to try to help these whales and learn everything we can along the way about what’s impacting them that can benefit other types of whales in other places.”