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Small freshwater fish in greater danger of extinction in the coming decades

The high temperatures and rains expected between 2050 and 2070 as a consequence of global climate change would be the main responsible for the decrease of almost 50% of these species, especially in tropical areas.

To offset this reality which seems imminent, requires all the countries in the world to report the academic trends and projections to take action for a term closer to 2050, a year established in some protocols that seek to decrease the effects of climate change.

The prior would be some of the main results of a research project carried out by Universidad del Magdalena Biologists and Universidad Nacional de Colombia (UNal) Amazonian Studies Ph.D., Ana Milena Manjarrés Hernández.

“In this journey through biology, I was concerned to understand how fish are distributed in general, mainly in rivers. This is when I got the idea of working in species distribution and analyzing it from spatial and temporal perspectives, establishing along with my thesis director, this doctoral research project,” said Manjarrés.

Read more: The Amazon trout, the Amazonian treasure at risk of overfishing

In her project, Manjarrés performed an analysis of the variables, or factors that could have a bearing on freshwater fish distribution, taking into account different spatial scales and impact levels. Furthermore, she carried out a projection on how the current conditions would help predict which species would be present, or extinct between 2050 and 2070.

“Normally biologists do field trips and obtain information but in this opportunity, my work consisted of updating and analyzing the database which had close to 16,825 fish species of the world This database was obtained with the support of a whole team, and headed by Professor Cástor Guisande,” she said.

Using a software program known as ModestR she analyzed 19 bioclimatic variables, such as temperature and rainfall, which help to understand how the environment works. They also worked with other variables, such as height, human population density, vegetation rate, primary production, and others which contributed to the analysis.

Endemic species, the most impacted

The research project showed that the analysis of geographical extension produces a differentiated effect on the influence of the variable over species distribution. For instance, in small areas, known at the local scale, the temperature would be the variable that would most impact species distribution, while in larger areas, the influence of other factors, such as rainfall, would be greater.

“One of the species where we observed variability was in Hoplias malabaricus, known as the wolf fish (of the Erythrinid family). At the Amazon River basin level, we documented that in the sub-basins of Bolivia, rain produced a greater impact,” said Manjarrés.

They hope that for the coming years included for the previsions for 2050 to 2070, and according to the species distribution models they worked on, there will be a total disappearance of the areas of distribution to almost half of the freshwater fish species, which varies between 45.3 and 46.7% independent of the year and climate scenario.

According to Manjarrés, this would occur especially in smaller species and in species with a smaller geographic range, therefore it is less probable that endemic species adapt to climate change. Also, the taxonomic diversity would decrease as having fewer species there would be greater uniformity in all basins.

Closer measures

Carbon dioxide is one of the greenhouse effect gases that most contributes to climate change, through temperature hiking. Although there have been different scenarios and protocols to mitigate it, Manjarrés warns that before projecting different contention measures, Governments need to document more to produce more efficacious prevention.

“At the regional level, the idea is to work in formulating policies to protect specific areas and prevent the introduction of species in ecosystems, as besides the impact of the changing climate conditions, species interaction would also be impacted,” she added.

Read more: Exploring the deep sea, an opportunity for research

“At the local level we need to protect the areas, especially the species that help maintain the health of the environment and create awareness in schools and universities on preservation, and conservation, helping the ecosystem so the changes are carried out in the slowest way possible,” claims Manjarrés.

Fish sub-registry continues to be a challenge

Another of the goals of the Manjarrés’ research project was to determine how far or near are the inventories of fish species in the Amazon basin.

Manjarrés observed that the current registries are far below the number of species they expect to live in the basin. However, she discovered that according to the wealth of the species observed and forecasted, there is a pattern where the richest areas are closer to the headwaters and the less rich as near outpours.

According to Manjarrés, this sub-registry may be due to many factors, one of them is the lack of research in these locations, therefore it is necessary to invest more in research projects in the Amazon basin, “Although they carried out a large project known as Amazon Fish, –which tried to increase the inventory of fish species– there is still a lack of registries”.

“Another factor is that there are areas of difficult access, where, although there is research support, for many researchers it has been impossible to reach some areas of the great Amazon basin,” she added.



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