2023-09-24 05:00:00
He San Matías Gulfwhich extends between Punta Bermeja, Río Negro, and Punta Norte, in Chubut, suffers the invasion of exotic species, like many other ecosystems on the planet, as a consequence of different human activities. The latest introduced species that worries scientific researchers is the green crab or European shore crab. They tell him the “karateka crab” for the strong blows with which he attacks other individuals.
It was identified on the coast of The Grottoes, east of the Province of Río Negro. It has a green color with some yellow spots. Its shell can measure 9 centimeters. Its scientific name is Carcinoma maenas.
Their presence is worrying because it is known that invasive crabs can cause a lot of economic and environmental damage: they can reduce biodiversity and generate problems for local fisheries.
In the San Matías Gulf area, green crab individuals were found in 2021 and that motivated a study that allowed the first steps to be taken to determine what impact it may have on the ecosystem. The team of scientific researchers has already discovered that its presence is distributed in several coastal points of the San Matías Gulf.
“For now we know that he is just another member. We do not have to see it from the catastrophic side, because we do not know if it will be a risk for coastal diversity. Its incidence will emerge over time. What is known is that it is very difficult to control a species when it is already established. And this crab is already on our shores,” he told Rio Negro Newspaper marine biologist Maite Narvarte, one of the scientists in charge of the research.
Narvarte is a researcher at Conicet in the Almirante Storni Center for Applied Research and Technology Transfer in Marine Resources (CIMAS) and and the Higher School of Marine Sciences of the National University of Comahuein San Antonio Oeste, Río Negro.
What would be the damage that the crab could cause in San Matías? It happens that, in other places where it spread, it wreaked havoc on the ecosystem. “It is known that among the invaders found in the Golfo Nuevo, in Chubut, green crabs were the most successful invertebrates, in terms of their potential to establish self-sustaining populations. Therefore, its introduction has raised concern in relation to its possible negative interaction with populations in native species of crabs and mussels of the rocky intertidal zone.”
In the northeast of USAFor example, something similar happens, and the green crab competes with two native crabs. Meanwhile in New Scotland, Canadatheir diet is similar to that of American lobster. This means that in situations where food is scarce, “this invader reduces the available food resources of the lobster, which is of high commercial value,” said the expert.
“It could be expected that in the San Matías Gulf the green crab would also present competitive trophic interactions and/or predation with species native to the area,” he warned. That is, it competes for food and ends up imposing itself on other varieties or directly also ends up preying on them. Because “this crab is a voracious predator that feeds on gastropods (limpets and snails), cirripedians (a type of crustacean) and mussels, although they are also cannibals, and can feed on crabs of their own species or another,” he said.
So far, however, no worrying incidents have been seen in the area investigated locally. “There were fewer mussels during a period of the study we did, but it coincided with a time of very high temperatures and the low availability we believe is associated with that climatic factor,” Narvarte explained.
As part of the investigation, a technical report was already made on the crab in the San Matías Gulf. In addition to Narvarte, Micaela Müller Baigorria, Alexia Aguilar, Daniela Cabrera Galeano, Samantha Fraire, Agustín Patocchi, Camila Sierra, Lucila Sánchez, Leandro Hünicken, and Raúl González did so.
The research team described the densities, size structure, sex ratio and female crabs that were incubating eggs (ovigerous). They evaluated two different intertidal environments located south of Las Grutas. One of them has a rocky substrate and the other a marsh, which is a swampy area that usually fills with water at high tide.
It was found that, unlike what occurs with the same species in other places, in the areas studied south of Las Grutas The green crab is found in greater numbers in some pools that are covered with sea water, and not so much in rocky or sandy sectors. Although this difference was related “to the time of sampling and not to preferences on the part of the species for one or another environment,” he clarified.
On the other hand, the relationships between sexes (abundance of females or males) were comparatively similar to other areas of Argentina, where the crab also arrived and began to spread. The way in which the species was introduced is still unknown, but there are assumptions.
“With species that are not native, it usually happens that they arrive along with the ballast water of merchant ships, or ships that travel from abroad and bring that liquid to balance their flotation, from which they are released once they enter the port. Some life forms can arrive there that, if they are resistant enough, can remain in the new habitat,” explained the biologist.
Research on green crab in the Gulf is ongoing. One of the members of the group, Müller Baigorria is carrying out a thesis on the subject. More information will be gathered about the species and its possible impact on ecosystems.
When was the first detection in the Argentine Sea
The first detection of the green crab was made in 2000 in Comodoro Rivadavia, although the first published report was from Caleta Carolina years later (near Camarones). According to what he said Evangelina Dwindlesresearcher of Institute of Biology of Marine Organisms of Conicet in Puerto Madryn, Chubut.
“In the first years, the crab expanded southward more abundantly, specifically on the southern coast of the Golfo San Jorge, and remained for several years until it was observed in Puerto Madryn in 2014. There, the density and expansion rate exploded. . Today it is the most abundant crab in the intertidal. We don’t really know what happened. It may have found an environment much more suitable for reproduction and survival, or a second introduction event may have occurred, which is common with marine species. If the latter occurred, it means that the crab was not moving up the coast from Comodoro Rivadavia but was introduced by boats again.
“It arrived earlier at the San Matías Gulf than at the San José Gulf, which is north of the Valdés Peninsula. It could continue to disperse northward without major complications since the native intertidal crabs are very small and this exotic species is quite aggressive,” Schwindt warned.
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