The Brazilian current enters the system from the North until it meets the Malvinas current in the Confluence Zone.
The Brazilian Current is changing and affects fishing
Wednesday, October 21, 2020, 02:00 (GMT + 9)
Global warming has generated changes in the South Atlantic. The increase in the temperature of the water and the intensity of the winds is generating a displacement of the Brazilian Current towards the south, causing changes in the environment that impact on the fishing resources.
The interesting reports prepared by CONICET oceanographer Bárbara Franco and a renowned team of scientists show the effects that climate change has already produced on the southeast of the South Atlantic Ocean, causing changes in the temperature of the water and the movement towards the south of the Brazilian Current. The warm waters are dragged to the south modifying the confluence with the Malvinas Current and this brings about a change in the marine environments, affecting commercial fishing species from Argentina, Brazil and Uruguay. The Patagonian scallop, anchovy and hubbsi hake are some of the resources on which they provide information, indicating that they should be read as the first signs of a change that will not stop.
The Malvinas Current carries cold waters and nutrients northward along the continental slope and the edge of the Argentine shelf, while the Brazilian Current carries warm waters southward along the continental slope and outer shelf of Brazil and Uruguay. The confluence of these currents generates environments of very high productivity; The Front of the Talud is one of the most prominent nationally and worldwide.
But the effects of climate change are changing that scenario. Changes in wind direction over the South Atlantic have led to an intensification of the Brazil Current and a poleward shift. Consequently, intense ocean warming has been observed along the path of the Brazil Current, over the southern Brazilian shelf and in the Rio de la Plata.
There has been a constant change towards the poles of the main subtropical ocean gyres driven by climate change with a strong tendency to surface warming on the border currents of the western edge of the oceans, which is displacing the Brazilian Current towards the south. In the region, the warming of the ocean surface is observed, mainly along the trajectory of the Brazil Current, the Brazil-Malvinas Confluence and in the Río de la Plata.
Image: Worm current of Brazil “Atlas of the Patagonian Sea. Species and Spaces ”, co-edited by the Wildlife Conservation Society and BirdLife International
The South Atlantic has been reported as one of the most extensive and intense hot zones for global warming of the global ocean surface and this research group has identified hot areas, "hotspots", in the water column, particularly in the middle of the world. water and lower layers where marine species inhabit.
But they note that even though changes in the distribution and productivity of marine species have already been recorded from oceanic warming faster than other regions of the world, the potential changes remain largely unexplored.
“While hot areas from surface ocean warming and heat waves are relatively well studied based on the availability of satellite data, temperature changes at greater depths and at the bottom remain poor, despite their potential impact. in neritic, pelagic and benthic ecosystems ”, they warn.
►Scallop fishing ground location (Source: Advances in the science of aquaculture and fisheries | Volume 40, 2016 | Chapter 25 - Biology, fishing and management of scallops in Argentina | Authores: GasparSoriaJ.M. (Lobo) OrensanzEnrique M. MorsánAna M.ParmaRicardo O. Amoroso)
Despite the existing limitations, the research group has been able to describe, based on the scientific fishery information available, some changes in fisheries of commercial importance that would be related to the changes in the environment that the displacement of the Brazilian Current is causing.
The warming of the waters over the largest bank of Patagonian scallops could exceed the thermal tolerance of this species and its survival. The mean surface temperature during 2014 shows warmer waters of the Brazil Current reaching latitudes further south than observed during 2005, for example.
As the Patagonian scallop is a cold-water species, the southward shift of this warming trend and its projection implies a trend towards unfavorable thermal conditions for the species, they explain.
As for the hubbsi hake, another cold water species, they point out that it has also exhibited decreasing landings during the last 25 years and add that the movement towards the south that has been observed could be a consequence of warming. This situation, they consider, "deserves urgent efforts to improve research."
Image: “Atlas of the Patagonian Sea. Species and Spaces ”, co-edited by the Wildlife Conservation Society and BirdLife International
On the other hand, they point out that despite being caught less than recommended and having sustainability certification, the engraulis anchovy has undergone changes in abundance as well as in the size and weight of the specimens. They consider that these changes could be related to an increase in surface temperature and changes in the salinity of the water.
Horse mackerel (Trachurus lathami). Image: courtesy INIDEP ►
Another relevant piece of information is the southward movement of horse mackerel, which would be associated with an expansion of feeding areas. In Uruguay, they are even beginning to see a tropicalization of species: spaces that were previously occupied by cold water resources are being occupied by warmer water species.
Climate change has also intensified extreme weather and climate events in the southeastern South Atlantic Ocean, affecting fisheries that are particularly vulnerable. Among the affected species, they cite the case of massive deaths in populations of yellow clams and the subsequent lasting decline in abundance.
►Hake (Hubbsi) (Photo: courtesy INIDEP)
For specialists, the projections of changes in fishing catches require urgent research efforts based on observations of changes in yield, abundance, distribution and sizes of the main fishery resources. "The impact of such projected changes depends on how the countries of the region increase their capacity to adapt to climate change," they indicate.
They note that although Brazil, Uruguay and Argentina are home to numerous commercially significant fisheries, their research has rarely been approached from a climate change perspective.
“Lack of long-term monitoring programs, restricted access to available information, partial data on loading from global stock assessment databases, and institutional indifference to consider environmental changes in fisheries management have contributed to a shortage of knowledge in comparison with other regions ”, they indicate.
They warn that this scarcity of data leads to a poor representation of the South Atlantic in global assessments of the climate impact on fisheries and undermines the adaptive capacity of dependent governments and marine communities, highlighting that in our region 59% of populations are fishing at unsustainable levels, and suggest improving assessments to lay the foundations for better management strategies in the context of climate change.
"By raising awareness of the potential impact of climate change on fisheries, adapting to changes in fish yields and proactively creating effective transboundary institutions, many of the potentially detrimental effects of climate change on fisheries could be alleviated," the report concludes.
Author: Karina Fernandez / Revista Puerto