Researchers from UNR and CONICET are working at the Rosario Aquarium to generate knowledge about species diversity, analyze how human activities affect them, and develop tools for fish production.
We can take a close look at the riverbed and rediscover species as surprising as those in the ocean at the Paraná River Aquarium. Among the specimens, several stand out for their size, colors, and behavior, such as the lungfish, ghost shrimp, ray, and the sea bream, as well as the more familiar dorado, surubí, navy, and boga.
A team of aquarists dive into the enormous fish tanks and take care of all the care: water, feeding, quarantine, animal welfare, and recreating the river environments where they live, such as the marsh, the Madrejón, the lagoon, and the ravine. One of them, Biotechnology graduate Fernando Lo Menzo, explains that they select the species that fit into each of these environments, provided they are compatible, do not prey on each other, or compete with each other, and this assembly is maintained or modified over time according to needs. Since there is no bibliography for many species, they learn the habits of each one and adapt.
There are currently nearly 2000 specimens of more than 100 species in the river. The most common is the sábalo, which accounts for 60% of the Paraná fish population and forms the basis of the entire food chain. Others, such as the pacú, are no longer fished in our area but are found further north.
The best-known species are those caught and eaten, but there are other, less common species that attract visitors. For example, the lungfish, which is like an eel that has to come up to take in atmospheric air instead of oxygen from the water. Or the sea snails, which aren't colorful but eat algae and place their mouths like suction cups on the walls of the tank. With the interest sparked by the Conicet broadcast on the depths of the sea, the transparent shrimp, known as "ghost shrimp," and the large, polka-dotted rays gained popularity.
Regarding the feared palometas and their sharp teeth, "we try not to demonize them," they say. They explain that their behavior is related to life cycles: in summer, the temperature and metabolism rise, the river water level drops, they are in their reproductive stage, and they are very territorial. The same thing happens with stingrays if they are in the wrong place at the wrong time. In the aquarium, these conditions are controlled and are harmless. "I have to dive where the palometas are, and I have never been attacked," says the aquarist.
At this Scientific, Technological, and Educational Center, in addition to the aquarium room with QR codes to access information on each fish, there is a park of native plant species from the province and a laboratory dedicated to studying river fish and their ecosystems. Comprehensive environmental education is promoted for both schools and all visitors. "There is an integral connection between research, outreach, and education around the generation of knowledge," says Bárbara Bercovich, provincial director of special projects for the Santa Fe Science Secretariat.
Aquatic Biotechnology
A team of researchers from UNR and CONICET is working in the Joint Aquatic Biotechnology Laboratory to generate knowledge about the Paraná River, from characterizing the species that inhabit it, its diversity, and how human activities affect it, to developing tools for production.
Its director, Vanina Villanova, PhD in Biological Sciences, explains that to characterize diversity without having to go fishing, they take water samples, filter them, and analyze the remaining DNA. This must match a gene sequence to determine the species it belongs to. Since they had 150 sequences but there are around 230 species in our area of the river, the team recently dedicated itself to completing that database.
One line of research is to evaluate the genetic diversity of the Paraná River's sábalo and pacú populations. In the case of the sábalo, it is to observe whether there is any effect from the river's low water level or fishing over the years, and for the pacú, it is to compare the diversity and stocks of farmed populations with wild ones.
"The number of species in the Paraná River that we don't know, or know very little about, is impressive," says Villanova, who believes that this genetic characterization provides another tool for discovering them. For example, regarding river salmon, which is considered a vulnerable population, only one species was described in our area, but through genetic studies they discovered two in Corrientes, and now they have been found in our area as well. Questions then arise about why they weren't there before and now they are, or perhaps they have always been there and hadn't been identified or studied. For the biotechnologist, climate change may affect the river's conditions, with variations in the pulses of drought and flooding, which would bring about changes in the distribution of fish populations.
Outside the laboratory, there are tanks with pacu and silverside broodstock. Last year, one of the researchers focused on feeding silverside fish for farming, given that their meat is in high demand in the market. In the case of pacu, they are studying their immune system and stress response when exposed to low temperatures, as they cannot regulate their own temperature and depend on the environment. They are also analyzing whether gut bacteria have any influence on this response to cold. "In pacu farming areas, if the temperature drops significantly, there is susceptibility to disease and mortality can occur," says Villanova.
They also study sexual determination in pacu because it's a species that can't be distinguished with the naked eye whether it's male or female, except during reproduction, when the fish are already mature at two or three years old. For the researcher, this basic knowledge can have applications in fish farming and production.
In addition to these studies, two new ones were added: one on bacteriophages, which are phages that infect bacteria and produce environmental modulation. These are used in aquaculture as an alternative strategy to the use of antibiotics in all animal production. Furthermore, they are working on the characterization of metagenomes, that is, bacterial genomes associated with different production systems, to generate more sustainable aquaculture.
The Laboratory currently sustains itself thanks to the technological services it offers. For example, through CONICET's STAN (High-Level Technological Services), they provide services to the Teko company of the Puerto Las Palmas del Chaco group, one of the largest pacu producers in Argentina. Since they organize their breeding stock according to kinship and genetic diversity, the researchers' job is to monitor this population in captivity to observe whether or not there is erosion over the generations and what happens in the breeding center. Additionally, through the School of Biochemical Sciences, they provide sequencing services to both companies and other universities. These revenues are used by the Laboratory to continue research. "This is possible because there are people with a lot of enthusiasm for science, and despite the poor economic conditions, we look for ways to survive."
Journalist: Victoria Arrabal/Photos: Acuario