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New report shows that Ecuador’s freshwater fish are in grave danger

Published on August 23, 2021

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A recent study published in the Journal of Fish Biology highlights that the country’s aquatic ecosystems are seriously threatened, and conditions are worsening.

The freshwater fish communities in Ecuador exhibit some of the highest levels of diversity and endemism in the neotropics. But unfortunately, the country’s aquatic ecosystems are seriously threatened, there is little information about its fish and the threats to these animals increase every day.

The picture becomes more complicated as various studies show that freshwater fisheries generate only 10% of the income from fishing compared to marine fish and this leads to governments having little economic incentive to enforce laws that they seek to protect them.

Recently, a group of researchers did a great analysis and review of the conservation threats faced by freshwater fish in Ecuador. The results were published in the Journal of Fish Biology, finding at least 10 great dangers for these animals: loss of habitat due to the physical alteration of rivers, deforestation, degradation of wetlands and floodplains, water pollution by agricultural activities and urban, mining, oil exploitation, dams, overfishing, invasive species and climate change.

Bad data: the big concern

Several years ago, Ecuador formed the Freshwater Fish Working Group with the aim of expanding knowledge about these animals. In the midst of this work, 163 species were evaluated and, in 2019, the National Red List of Freshwater Fish was published. Several of these scientists are the authors of the new study, which highlights that 66 of these fish (40.5%) are considered Data Deficient (DD), that is, there is not enough information about them.

“Many of the species that were not evaluated lacked sufficient data to be considered for evaluation, so the actual number of species in category DD is probably much higher,” states the article.

Without a doubt, the lack of information is one of the main conclusions of the analysis carried out.

“We are very few scientists who work with fish in the country. It is one of the least studied groups. Many prefer reptiles, amphibians or mammals and fish are lagging behind, there is not much interest,” says Jonathan Valdiviezo, ichthyologist and researcher at the National Institute of Biodiversity (Inabio) and one of the authors of the article.

In addition, Valdiviezo emphasizes that there is information that is not published or that remains archived in State institutions. Likewise, there is a professional zeal among some researchers that prevents many from sharing their data, despite the fact that it has been changing in recent years.

For his part, Windsor Aguirre, ichthyologist, professor at DePaul University in Chicago, and lead author of the article, highlights that the large information gaps on freshwater fish are also related to historical factors such as the lack of resources for research in the country. Aguirre highlights that most of the information corresponds to commercial species but there is no greater interest in studying the other native fauna.

Not only is the lack of information worrisome because the analysis revealed that of the remaining species evaluated, 62 were categorized as Least Concern (LC) – according to the criteria of the IUCN Red List of Species – but 35 face some type of threat : 15 vulnerable (VU), 13 Near Threatened (NT), six Endangered (EN) and one Critically Endangered (CR).

Despite this, Aguirre says that the number 35 must be taken with caution since, as the article shows, the central point is that there is not enough information, which is also quite serious. “There are no databases from past decades that show us the pattern of change in abundance and diversity of fish. They exist in other countries, not in Ecuador.”

For Aguirre, it is clear that the fish have suffered a lot from the impacts to the rivers.

“That number [35] was estimated by the experts who participated in workshops and in this paper (scientific article), but it is difficult to know how real that number is because we do not have long-term data. It is possible that the situation is worse and that some species have disappeared from some of the rivers,” he says.

More than 30 species at risk

The article divides its analysis into three geographical areas: Coast, Sierra, and Amazon . The western coast of Ecuador is characterized by high levels of endemism but relatively low fish diversity. There it was estimated that approximately 38% of freshwater fish -43 of the 112 registered for this region- are endemic and there are nine species that present some degree of threat, being the Pseudochalceus bohlkei the one that is most at risk, located in the Endangered category (EN).

Unfortunately, the study highlights that western Ecuador is the region of the country that has been most impacted by human development, it has the largest number of inhabitants in the country and most of the land has been transformed into agricultural fields.

The lowlands of the Amazon are home to large catfish of the Pimelodidae family and in general a great variety of orders such as the characiformes, the osteoglossiformes and the myliobatiformes. Although studies of fish in the Amazon are on the rise, “there have been no systematic reviews of all faunas, and much remains to be learned about the ecology of most species,” the article reads. In this region, 22 species under threat were detected, of which 16 correspond to catfish.

In the Andes mountain range, also called the Sierra region, there are high levels of biological diversity and endemism, most of them in the middle and lower elevations of the rivers. This area has also been affected by humans for hundreds of years and much of the natural forest has been replaced by agricultural fields, non-native timber plantations and pastures. The authors add that many large cities lack adequate sewage treatment, that there are introduced species such as trout (Salmo trutta) that are highly detrimental to native species, and that there has been an increase in dam construction in recent years.

The researchers found four species of fish with some degree of threat in the Sierra region, the catfish Astroblepus ubidiai being the one of most concern since it is in the Critically Endangered (CR) category. This fish is the only one of the 35 registered for Ecuador that is in the highest risk category.

The big threats to fish

Researcher Aguirre says that habitat loss is critical and that there has been a lot of deforestation, especially in the western region, in the Guayas River basin, which is now dedicated to agriculture. “Deforestation is progressing in other areas, that changes the conditions in the rivers and causes some of the species to decrease in abundance or disappear, that has happened a lot on the coast and in the Andes and now it is progressing in the east [Amazon],” he comments.

Aguirre says that in the Amazon region there is a lot of development due to oil exploitation and that brings construction of roads, which facilitates the clearing of forest and greater erosion that translates into greater sediments in the rivers, as well as changes in their temperatures and structures. of the beds.

For the main author of the article, the quality of the water is another problem because in the Andes there are large cities where there is little control of the substances that enter the rivers, many of which are mountain, have small paths and that means that “the affectation is more evident.”

The researchers also pointed out the issue of dams, which they say have a long history of negative impacts. “Recovering that aquatic fauna is very difficult. Also, some of those dams are not necessary,” says Aguirre.

Jonathan Valdiviezo reinforces this concern by citing the case of the disappearance of the San Rafael waterfall and the regressive erosion of the Coca River where the Coca Codo Sinclair hydroelectric plant is located. According to him, the accumulation of sediment affects the breathing capacity of the fish, it sticks to their gills, and they die asphyxiated.

“They have not invited us to do a sample in the area, we are waiting for them to allow us to enter to analyze the effects of what has happened because we are sure that there is already an obvious impact. It is likely that there are environmental consultancies but that information is not publicly available and so far there is no report on what was in the river and what exists today,” Valdiviezo highlights.

Invasive species are also a danger to freshwater fish from Ecuador and quantifying the impact has been difficult due to lack of studies. However, the impact of tilapia (Oreochromis spp.) On the coast and rainbow trout (Oncorhynchus mykiss) in the Andes is evident.

For example, trout has negative impacts on small species of fish and on the catfish of the Andes, of the genus Astroblepus, which are endemic and of concern because they live in the upper parts of the rivers, having a rather restricted distribution.

The tilapia, on the other hand, is from lowlands and was introduced because it has a very desirable meat. Aguirre says that it is a very tolerant fish, it does not cost much money to keep it because it eats in the lower part of the food chain and it is very strong and resistant, so the quality of the water does not matter much. “But it is aggressive with other species, it can feed on some of them, and it can change the conditions of rivers due to its continuous removal of sediments on the bottoms, changing the turbidity of the water and some of its chemical properties,” adds the investigator.

Urgent action is needed

Freshwater fish are important in continental ecosystems and there is no question about that.

“They help the ecosystem to stay healthy, there are species that feed on algae, others feed on other fish, others help to eat dead fish,” says Jonathan Valdiviezo. If their ecosystem services are not enough to understand their importance, there are also social and economic arguments: “they are indispensable for hundreds of communities that live on the banks of rivers. In our country, the main source of protein is fish, either freshwater or seawater,” emphasizes Valdiviezo.

For the researcher, it is important to create agreements and regulations to reduce the impacts on fish, and he adds that it is not a question of prohibiting fishing but rather that it is sustainable. For example, he says that Amazonian catfish have suffered enormously from overfishing because, being migratory, they are easy to fish since they are trapped in the nets.

“In Ecuador there are regulations for the closed season for crabs and, in general, for many marine species; we want them not to leave freshwater systems behind. Researchers have information and we could collaborate in that process. The most difficult thing is knocking on the doors of decision makers and receiving attention, it is difficult even when you work for the same State,” he says.

Windsor Aguirre is clear that one of the most urgent recommendations has to do with filling the huge information gaps on freshwater fish. He believes that it is necessary to create a monitoring mechanism to establish a database that can be used in the long term and thus see patterns of change in fish populations. This, he says, has to go hand in hand with raising awareness among local human communities as Ecuador has high rates of endemism and they are being lost.

Despite the worrying situation, the researchers believe that it is possible to change the current trend of impact on freshwater ecosystems. For example, fish have the advantage that there are people who like recreational fishing and that can be useful for researchers as fishermen could help collect data on species and their distributions.

Aguirre says that it is not only important to protect what exists but to restore degraded habitats that may have already lost their economic value because activities such as mining, or agriculture are no longer viable.

“It is important to try to recover wetlands and flooded areas that are important for the ecology of the fish, especially in their reproduction. This can even recover the tourist value and bring other benefits: going fishing, bird watching and recreational activities that do not have much impact on the fish.”


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