The drone of Maximiliano Cartes Salas recorded for the first time a group of Gasterochisma melampus, known as “Argentine tunas,” swimming alive near the coast of Las Grutas, in the Golfo San Matías. Until now, sightings were limited to stranded specimens lifeless on the beaches.
“We are used to seeing them dead on the sand. Capturing them alive, strong, and patrolling our coasts is a historic visual document,” shared Cartes Salas on his social networks.
A little-known species
Marine biologist Raúl González, a researcher at the Universidad Nacional del Comahue and CONICET, has been studying this species for almost 40 years. He clarifies in dialogue with the Río Negro portal that, although it is called “Argentine tuna,” it is actually more related to mackerels than to tunas. Internationally it is known as “butterfly mackerel” due to the long fins of the juveniles that resemble wings.
Its distribution is circumpolar in the southern hemisphere, and in the southwestern Atlantic, its presence is scarce. Most data comes from captures by Japanese fleets in the Pacific, off the coast of Chile.
Mystery in the Golfo San Matías
Since 1988, González has recorded between 30 and 40 strandings in the area of Las Grutas and San Antonio Oeste, generally one or two specimens per year. The new video clears doubts: they are small groups that occasionally approach the coast.
The hypothesis is that they migrate to reproductive areas in the Pacific, guided by magnetic lines, and that on this journey some end up entering the gulf. Seasonality indicates appearances between April and August, with peaks in May and June.
Characteristics of the specimens
- Size: between 80 cm and 1.90 m.
- Weight: from 20 to 80 kilos.
- Diet: squid, anchovies, and pelagic species.
- Females: in an advanced reproductive state, which coincides with their movement towards breeding areas in the Pacific.
Scientific importance
The visual record confirms hypotheses built over decades and provides key material for scientific publications. “Today in journals, having images or videos is very important because it makes everything more powerful,” says González.
Moreover, the finding reinforces the need for non-invasive observations, like the one made by Cartes Salas, who emphasized that he kept a prudent distance and used a telephoto lens to avoid altering the animals’ behavior.
After almost 40 years of seeing them only stranded, the filming of live Argentine tunas in groups marks a milestone for marine science in Argentina. The Golfo San Matías is confirmed as a key scenario for understanding the migration and behavior of this enigmatic species, which continues to surprise researchers and local fishermen.
Instagram video @maximilianofcartes.
