- The abundance of bottlenose dolphins in Ecuador’s Gulf of Guayaquil has decreased by around 50% in the last decade.
- Several rivers in Ecuador, as well as neighboring Peru, empty into the gulf, and it is one of the most productive fishing areas in the country.
- But entanglements in fishing gear, along with tourism and water pollution, are contributing to the dolphins’ decline and could lead to their disappearance altogether in the coming decades, researchers report in a new study.
* This report is a journalistic collaboration between Mongabay Latam and GK from Ecuador.
Amid the swirling mix of fresh and salt water in the Gulf of Guayaquil live groups of bottlenose dolphins, perhaps the best-known cetacean species in the world and known locally as bufeos.
On the IUCN Red List of Threatened Species, the conservation status of bottlenose dolphins (Tursiops truncatus) is deemed of least concern globally. But, according to recent research, unless things change, they could soon disappear from the shores of Ecuador, which shares the Gulf of Guayaquil with Peru.
Two populations of the species live in the western Gulf of Guayaquil, named Posorja and El Morro after nearby human communities. They could be wiped out in less than a century, according to marine biologists Fernando Félix and Santiago Burneo. Along with their colleagues at the Pontifical Catholic University of Ecuador (PUCE), the scientists have observed a steep drop in the number of bottlenose dolphins in these areas over the past decade. Earlier research shows the population today is half of what it was in the early 1990s, and Félix and Burneo report in a study published Sept. 3 in the journal Frontiers in Marine Science that the species could ultimately disappear from the gulf in the next few decades.
The bottlenose dolphins that live in the Gulf of Guayaquil are genetically unique compared to other groups of the same species living elsewhere. Félix said they’re more or less geographically isolated from other populations because the gulf offers them a stable environment and sufficient food. During this isolation, they’ve become genetically distinct, and with little influx of new genetic material from outside, the genetic diversity among the population has decreased. That has made them more susceptible to the consequences of human activities such as fishing, tourism and trade.
A drastic decline in population
Human activities affect ecosystems and biodiversity across the Gulf of Guayaquil. When Félix began studying bottlenose dolphins in the early 1990s, he estimated there were 637 individuals living in the gulf. In 2019, the researchers spotted 35 resident dolphins living in the Posorja and El Morro groups. Only seven of those were females of reproductive age, a statistic that throws the future of the gulf’s bottlenose dolphin population into question.
According to the researchers’ estimates, the dolphins in Posorja could be completely extirpated in 40 years, and the dolphins in El Morro in 100 years. Without the financial resources to affix satellite tags to the dolphins, the scientists are restricted to monitoring these cetaceans through visual observations. As a result, they have not been able to determine why individual dolphins have disappeared. The only thing they know for sure is that, on average, fewer and fewer remain each year.
Félix said he believes that, in recent years, the population has fragmented, possibly due to migration. Last year, near the city of Naranjal on the eastern edge of the Gulf of Guayaquil, he came across four dolphins that used to live between the Posorja and El Morro populations.
Ana Eguiguren, a marine biologist at Dalhousie University in Canada, who was not involved in the recent study, said dolphins usually remain in the same place, and it’s unusual for them to leave. Bottlenose dolphins live in what scientists call fission-fusion societies. One component of that structure involves numerous cooperative interactions within their social groups. That makes it rare for communities to fragment and for individuals to go to other places, Eguiguren said. Still, Félix said that if the dolphins can find better conditions in other areas, they may leave.
Guardians of the estuary
The Gulf of Guayaquil is the largest estuary ecosystem on the South American Pacific coast, according to the United Nations’ Convention on Biological Diversity. In the gulf, the fresh waters from Ecuador’s and Peru’s rivers meet the salty waters of the sea, creating a unique ecosystem. Eguiguren said estuaries support a wide array of species because they contain nutrients from both the rivers and the ocean. A warm current from Panama also converges with the freezing Humboldt current along this part of the coast, bringing still more nutrients into the system and creating habitat for large numbers of species — species that provide food for dolphins and humans alike, Félix said.
The Gulf of Guayaquil is also one of the most productive fishing grounds on the Ecuadoran coast. There are fisheries for shrimp, tuna, small pelagic species such as sardines and anchovies, and pangora, or stone crab. Félix said this area is Ecuador’s most important economic and social asset. But if the ecosystem is not looked after, he said, it will no longer be as productive.
“We are going to find ourselves in big trouble,” he said, because being without food “would put our own survival at risk.”
Dolphins are critical to the health of the gulf. In this ecosystem, dolphins are at the top of the food chain, and they are responsible, in part, for keeping the habitat in balance. They prey on sick and old animals, which helps to maintain the health of the ecosystem.
Without dolphins in the role of predators, Eguiguren said, the populations of other species would grow out of control. In the long term, such a change would affect not only the estuary, but also the mangroves that surround it.
Bottlenose dolphins are also a sentinel species because they are sensitive to the pressures around them. When a sentinel species is sick, it can be a sign that something is amiss in the environment, Eguiguren said. Changes to their health and their responses to toxic elements in the environment can serve as an alarm about habitat degradation and the presence of pollutants, she added.
Burneo and Félix said that in the Gulf of Guayaquil the dolphins “can tell them what is happening there, and this also helps in identifying other species that are being affected in the estuary.” Both said that if dolphins are conserved, other species will be too, some of them economically important to Ecuador’s fishery sector. If dolphins aren’t protected, the consequences could be dire for the ecosystem and for people.
The main threats
Fisherfolk and dolphins navigate the waters of the Gulf of Guayaquil in pursuit of the same goal: finding fish. The heavy fishing pressure levied by humans is one of the main reasons that the Posorja and El Morro dolphins are in danger. Félix said the primary threat is fishing gear, especially nets on the bottom of the ocean. Fishers set baited nets in very deep waters and leave them there, unattended, for up to 24 hours, he said. If dolphins get entangled in one of these nets, Félix added, they will most likely suffocate within minutes.
As marine mammals, dolphins must constantly surface to breathe. But if they get tangled up and no one notices, they will die, Félix said.
Cetaceans are also prone to being trapped in surface nets. Although fishers will often cut them loose, they can create problems by not following best practices. Sometimes, fishers release dolphins without noticing that parts of the net are still attached to the dolphin’s tail or fins, Félix said. Pieces of the net could become embedded in the flesh, causing infections that could lead to painful deaths.
Another threat to dolphins in the Gulf of Guayaquil is maritime traffic. A large number of boats traverse through the gulf, especially in the Posorja area, and they are not monitored in any way, Burneo said. Dolphins must dodge boats constantly, causing them to burn more energy. Expending this energy means less is available for breeding, Burneo said, potentially affecting the population’s demographics.
Noise from tourism and fishing vessels is another stressor impacting bottlenose dolphins in the Gulf of Guayaquil, Félix said. For example, about 40 dolphin-watching boats operate between Posorja and El Morro.
“They do not want to harm them,” Félix said. “In fact, they depend [economically] on the presence of the animals, and they do not want them to disappear.” But the noise from the boat engines has unavoidable consequences. A study published in the Journal of Experimental Biology revealed that marine mammals are among the species most affected by high noise levels in their habitats.
Dolphins depend on sound to communicate and forage for food, evade predators, and reproduce. In areas with significant ambient noise, relying on sound is more difficult. Félix said high noise levels suppress the immune system, reducing dolphins’ natural defenses and making them more susceptible to infections and diseases. They are more likely to suffer respiratory and digestive disorders and develop ulcers or tumors. Noise may even disrupt the production of sex hormones, potentially affecting reproduction and the long-term survival of the population.
Pollution is yet another threat to dolphin survival in the gulf. Three-quarters of the polluting waste from the entire Ecuadoran coast ends up in the Gulf of Guayaquil. Félix and Burneo said the gulf is under attack from all sides as waste from cities, herbicide and pesticide residues from banana and rice crops, and toxic effluent from the mining industry in the provinces of El Oro and Azuay flow in. These chemicals have devastating effects on the ecosystem and its biodiversity. Félix said he’s especially concerned that, lately, significant loads of heavy metals such as lead, mercury and arsenic have been found in the water. These pollutants can affect all species, creating a damaging domino effect that ripples through the food chain.
Heavy metals accumulate in algae that are then consumed by fish, which in turn provide food for the dolphins. Michelle Montenegro, an independent biologist who studies environmental science and eco-development, said that although the negative effects of these pollutants are difficult to track in the short term, they will appear in the future and the most serious consequence will be changes in population dynamics. Montenegro, who was not involved in the new study, said heavy metals hinder the survival, development and growth of dolphins. And the risks the population faces are greater because it is already quite small.
There is still hope
There is still time to protect the dolphin community in Ecuador’s most important port, Burneo said. If changes are made now, he said, it may be possible to rebuild dolphin numbers. He and his colleagues propose changes in fishing gear, waste management and the control of maritime traffic. The goal is to find solutions so that “the fisheries do not have to stop fishing and that tourism can still take place,” Burneo said. It is also important to develop awareness of the problem in the population, he added.
The figures are alarming. Félix said each dolphin that dies in the Gulf of Guayaquil represents about 3% of the area’s dolphin population.
“It is as if 50,000 people suddenly disappeared in Quito,” he said. Still, Burneo and Félix said they believe it is possible to restore the number of dolphins and improve conditions in the ecosystem so that individuals that migrate into the gulf will stay.
Their goal is to return to the gulf and work with communities on changes that will help save the dolphins. But the COVID-19 pandemic has delayed their plans and cut their resources. PUCE has a scholarship program to support research, including Burneo and Félix’s work for the last few years. Now, though, they need more, they said, so they are looking for other organizations and foundations to finance the dolphin monitoring project.
Currently, they said, too few regulations from the Ministry of Environment and Water (MAAE) are focused on protecting dolphins in the Gulf of Guayaquil.
MAAE told Mongabay Latam that its actions “are linked to monitoring the activities that generate the greatest impact” on marine species, including dolphins. The ministry also said that DP World, the company in charge of the operation of the deep-water port in Posorja, is developing a project in coordination with ESPOL, a public university in Guayaquil, focused on minimizing the effects of human activities on dolphins in the El Morro area.
Félix, who has worked with the cetacean community for about 30 years, is calling on local authorities to educate people about their role in the survival of the region’s dolphins. He said he believes that if communities establish a positive relationship with nature, there will be a spontaneous shift in people’s attitudes toward it. And those new attitudes will be essential to protecting the bottlenose dolphin population and preventing them from becoming extirpated from the Gulf of Guayaquil.
Citation:
Félix, F., & Burneo, S. F. (2020). Imminent risk of extirpation for two bottlenose dolphin communities in the Gulf of Guayaquil, Ecuador. Frontiers in Marine Science, 7. doi:10.3389/fmars.2020.537010
Banner image: Researchers call on other local stakeholders, environmental authorities and citizens to join forces to protect the last dolphins. Image by Fernando Félix.
This story was first reported by Mongabay’s Latam team and published here on our Latam site on Sept. 29, 2020.
