Vanishing dolphins in the Gulf of Guayaquil: can conservation help?

Environment | Oceans

By Madeline Davis, Freelance writer

Published August 22nd, 2022

At the Gulf of Guayaquil, where over 20 rivers in Ecuador and Peru feed into the largest estuarine ecosystem on South America’s Pacific coast, bottlenose dolphins once thrived. However, a steep decline in their numbers by 50% since the early 1990sㅡprimarily driven by increasing human activityㅡis endangering the local population.

The common bottlenose dolphin (Tursiops truncatus) is found across the globe in temperate and tropical waters. Ecuador’s Gulf of Guayaquil has been home to this intelligent and playful species in exceptionally concentrated numbers. Its uniquely biodiverse estuarine ecosystem, containing a nutrient-rich mix of saltwater and freshwater, extensive mangrove forests and a myriad of species, provides a rich supply of fish, squid, shrimp and crabs which make up the dolphins’ diet.

A dolphin at Puerto El Morro, Ecuador. | Carine06 / Flickr

Made famous by films such as Flipper and loved for their friendly disposition, dolphins are a major attraction for tourists in the Gulf. They also play an essential role in regulating the complex ecosystem at this location. As large top predators, they control the population of fish and other marine animals, maintaining ecological balance.

Yet their numbers at the Gulf of Guayaquil have been in sharp decline, falling by half (from over 600 to around 300 currently) within just the last three decades. Human intervention is the main driver, as the dolphin’s habitat is used intensively for fishing and tourism, as well as being under pressure from boat traffic, pollution and environmental degradation.

Marine biologist Dr Fernando Félix and his colleagues have been studying the dolphins in the Gulf of Guayaquil for years. Their latest research, published in the Ocean and Coastal Management journal, explores the environmental and human factors influencing the behaviour and survival of two dolphin communities within the Gulf, known as Posorja and El Morro, to gain insight into how we might protect them.

Under threat

Dr Félix identified fishing as one of the most urgent threats faced by the Gulf of Guayaquil’s dolphins. The estuaries here provide ample nutrients for a large number and diverse array of economically important marine species, such as tuna, shrimp, mackerel and sardines—consequently, it is one of the most plentiful fishing grounds in Ecuador. However, these fish also draw in feeding dolphins.

Shared use of these waters is increasingly leading to dolphins getting trapped in fishing gear and injured. Tragically, over 13% of bottlenose dolphins in the Gulf have scars or fin injuries linked to fishing. Entanglement can be fatalㅡa study on cetaceans on the Ecuadorian coast between 2001 and 2017 found entanglement in fishing gear to be the main diagnosed cause of death.

Bottom gillnets—vertical walls of netting stretching to the seafloor—are particularly dangerous. A bottom gillnet fishery has recently been constructed in the Gulf to harvest stone crabs, a delicacy worth around US $30 to $60 per pound. This area of the Gulf was once a busy feeding and resting site for the Posorja dolphins, but since the construction of the fishery they appear to be moving away to avoid the risk of getting trapped.

Dolphin watching trips in the Gulf of Guayaquil provide significant revenue for Ecuador’s economy, but are disrupting the dolphins’ behaviour and health. | Rinaldo Wurglitsch / Flickr

Fishing gear is not the only problem caused by the industry. Dr Félix warns that the constant exposure to the excessive levels of noise generated by fishing vessels, as well as dolphin-watching boats carrying tourists, threatens them with long-term health problems including hearing loss. This is particularly concerning for a species that relies on echolocation for navigation and feeding.

The Posorja dolphin community encounters more boat traffic and noise than the El Morro dolphin community, and this has caused noticeable differences between the groups. In the Posorja population, stress experienced by the dolphins may be contributing to reduced reproductive success. This community experiences 2.7 times greater mortality of dolphin calves under one year of age, and a fall in female fertility of almost 40% compared to the El Morro dolphins.

Pollution is another hazard faced by these dolphins. A shocking 75% of water pollution along Ecuador’s coastline ends up being collected in the Gulfㅡthis includes pesticides, sewage, industrial waste and even toxic heavy metals. These pollutants are very harmful to dolphins and have been linked to increased susceptibility to disease, reproductive problems, developmental abnormalities and other health conditions.

‘Stress experienced by the dolphins may be contributing to reduced reproductive success.’

Climate change is likely to exacerbate the population declines. Bottlenose dolphins are highly adaptable creatures, a trait which has enabled them to live across the globe. However, Gulf of Guayaquil’s dolphins are specially adapted to the local environmentㅡthey inhabit a small home range and are genetically distinct from other bottlenose dolphin populations, indicating they are dependent on the estuarine ecosystem.

This could make them especially susceptible to environmental changes caused by human activity and climate change combined. Predicted effects of climate change in the Gulf include a rise in temperature by about 2°C and an increase in precipitation by roughly 6% within the next 30 to 60 years, leading to habitat loss, loss of prey species and reduced reproductive success for the dolphins.

Essential for ocean life

Currently, the International Union for Conservation of Nature (IUCN) lists common bottlenose dolphins as a ‘Least Concern’ species globally. However, present rates of population decline in the Gulf of Guayaquil place the local populations at severe risk of disappearing within mere decades.

Ecologically, this loss would be disastrous. The potential implications of local bottlenose dolphin extinction are not fully known. However, they are a top-level predator in the Gulf of Guayaquil, and it is likely that without the dolphins to keep them in check, their prey would surge in numbers. Species further down the food web would then subsequently suffer a spike in predation, knocking the ecosystem out of balance.

The common bottlenose dolphin is also a sentinel speciesㅡ an organism which indicates the overall health of its environment. Due to their long lifespan (between 40 and 60 years in the wild) and their role as an apex predator, eating a wide variety of prey, they accumulate contaminants in their environment in their blubber and other body tissues. Therefore, analysis of stranded dolphins can provide a warning of environmental degradation and human health threats.

Fishing is a highly important and growing industry in Guayaquil and regulating it to ensure sustainable practices and prevent overfishing is challenging. | Prefectura de la Provincia de Guayas / Flickr

Conservation action

Urgent action needs to be taken to protect the Posorja and El Morro dolphins. However, planning and implementing effective conservation strategies is proving complicated.

The fishing sector is the second largest contributor to Ecuador’s annual exports, according to the public body Seafish. Guayaquil, the main port and largest city by population in Ecuador with over two million residents fuel its expanding fishing industry with catch from the Gulf. Ecotourism and dolphin-watching trips also provide significant revenue.

These jobs have improved the standard of living for many people within Guayaquil, particularly after the devastating impacts the coronavirus crisis had on the city. Opportunities in fishing and tourism in Guayaquil have drawn in a huge number of migrants from the more economically-deprived rural areas, contributing to a proliferation of slum housing in the southern outskirts of the city.

With such high social and economic dependency on fishing and tourism, how can we save the Gulf’s dolphins from further drastic population declines? The answer lies in making these practices more sustainable, rather than attempting to stop them.

‘The answer lies in making these practices more sustainable, rather than attempting to stop them.’

One step in the right direction would be to substitute gillnet fishing to safer methods, such as traps and longlines, which have been proven to reduce injuries and deaths of other cetaceans. Dr Félix has also previously proposed creating safe ‘corridors’ without disturbance for dolphins to travel through.

In 2007, the El Morro Mangrove Wildlife Refuge (REVISMEM) was constructed in the Gulf to protect against overfishing and over-tourism. The reserve has had some positive effects—most of the El Morro dolphins live within REVISMEM, and the reserve has helped to raise awareness of dolphin conservation among the community.

However, little was known before the construction of REVISMEM about the home range of the dolphins in Posorja. Unfortunately, 88% of them are found outside REVISMEM boundaries and so are not under its protection. The reserve has also not done enough to regulate the stone crab fishery that was built in the Posorja dolphin’s range.

An extension of this reserve, along with tighter regulations about the type and amount of fishing and tourism activities allowed, would help make REVISMEM more of a sanctuary for dolphins.

The dolphin population needs attention and implementing safe corridors may be the solution to save these creatures from the threat of fisheries. | Gregory "Slobirdr" Smith / Wikimedia Commons

Tackling water pollution in the Gulf is a complicated and challenging issue, as pollutants can be washed in from far onshore, and come from many sources. One example source of pollution is sewage—12% of households in the southern end of Guayaquil do not have access to sewage systems, meaning a lot of this eventually makes its way to the shore via rivers. Ideally, pollution needs to be addressed at the source by dealing with the social and environmental problems leading to its generation.

Educating children in schools and the local community on the importance of dolphins, and how they can be protected for the future, will also be essential for reconnecting people with nature and ensuring the dolphins will be protected in future generations.

While Dr Félix’s latest study provides insight into the dolphins’ lives, more research will need to be conducted to improve understanding of how much the dolphins are affected by certain changes in their environment. This information will enable policymakers to implement more effective conservation strategies, and help them to secure funding for such projects.

Dr Félix forecasts that, according to current trends, the dolphins could disappear completely from Posorja in 40 years and from El Morro in a century. This should not be allowed to happen. Change must be made as soon as possible to ensure these beautiful and intelligent creatures will be leaping in the water for many more years ahead.

Featured Image: NASA | Wikimedia Commons (please note that this photo was taken in Florida)

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