Reasons for the variation in abundance of illex argentinus

In a recent paper published online, Taiwanese scientists found a correlation between environmental factors, such as sea temperature, the strength of whirlpools, and the direction of ocean currents, to explain changes in squid abundance at mile 201. This is a complex analysis that involved more than 20 years of observations to reach this conclusion. If verified, it will allow predicting the annual abundance of the cephalopod available for fishing, a highly sought-after aspect to reduce the uncertainty prior to the start of the season that characterizes the Argentine squid fishery.

The biomass of short-lived marine resources, annual or few years, is usually characterized by very high variability, which affects fishing exploitation. Predicting the abundance of these resources available for fishing in a season is a crucial aspect for the fishing industry for several reasons: it provides advance information on the availability of the target species, allowing for more sustainable and efficient management of fishing operations. This helps avoid overexploitation of resources and contributes to the conservation of populations and their future availability in a sustainable fishing framework. Furthermore, abundance prediction facilitates the logistical and economic planning of fishing companies, optimizing efforts and minimizing the financial risks associated with uncertainty in the catch.

However, forecasting the abundance of annual or short-lived resources, such as squid or shrimp, represents one of the most complex challenges in fisheries research. The lack of knowledge about the myriad sources of variability and determining processes complicates the task, highlighting the need to develop much more sophisticated approaches to improve the accuracy of these predictions.

Despite several attempts to relate the variability of the abundance of the Argentine squid (Illex argentinus) with the oceanographic variables that model its habitat, until now it had not been possible to determine, even with reasonable doubt, significant relationships with said variables or a real knowledge of the processes that shape the abundance and availability of the species in the Southwest Atlantic.

This is what recent joint scientific work carried out by a dozen researchers from Taiwanese science institutions points out. The aforementioned scientific work, which addresses the interactions between the ocean and the atmosphere and relates them to the abundance of squid off the exclusive economic zone of Argentina, is based on observations and recording of environmental and fishing data carried out for 21 years, from 1998 to 2018.

The fishing data corresponded to the Taiwanese fleet that operates annually on the high seas and is mainly concentrated on both the Buenos Aires North Patagonian and South Patagonian stock of squid, two of the four subpopulations present in the Argentine Sea, which in their distribution and migrations exceed the EEZ Argentina.

Among the main findings of the study, which involved sophisticated calculation and analysis methods, a statistically significant relationship was determined between the abundance of squid during the main fishing season (March-May) and the sea surface temperature (SST), in the months prior to the start of each season (January-February), the kinetic energy of the whirlpools generated by marine currents in the area during the fishing season, and the direction and speed of marine currents at depths of around 100 meters from June to September of the previous year.

The mechanism by which these variables affect squid abundance, which involves large-scale phenomena, was also proposed by the researchers. They propose that the main climate driver would be the South American monsoon, which is a seasonal climate pattern characterized by heavy rains and winds that mainly affect the northern region of South America. This phenomenon generates climatic variations throughout South America, resulting in colder SSTs and an increase in w kinetics whirlpools along the coasts of the Southwest Atlantic, thus promoting a proliferation of squid abundance.

They also propose, in agreement with previous research, that a lower SST provides more suitable environmental conditions for a greater abundance of squid, which is based, at least in part, on the favorable survival of the larvae in the habitats and their trophic relationships. , and in the influence on the growth patterns and population structure of squid during their early growth phases, when they grow more rapidly.

The analysis by Taiwanese scientists demonstrates how oceanic and atmospheric changes can alter the annual abundance of squid in the Southwest Atlantic. However, in our opinion, many more studies are required before fully knowing the factors that affect the variability of squid in the Argentine Sea and adjacent regions. In this sense, it is striking that fishing pressure, that is, the impact of catches, which is usually decisive in the area close to our EEZ, was not taken into account when also relating it to the abundance of squid in the following season..

The study thus assumes that only environmental variables model squid abundance, and therefore the effect of fishing would be negligible. However, this assumption may not be entirely correct, given that the predation of squid beyond mile 200, facilitated by the total absence of capture rules and controls on fishing effort, generates a significant decrease every year. of the reproductive fractions of both the North Patagonian and South Patagonian Buenos Aires stock, which can negatively affect the reproductive success of the species and therefore its abundance in the following fishing season.

Another worrying aspect regarding the future of the squid fishery in the Southwest Atlantic arises from the scientific work analyzed. Given the strong relationship with sea temperature, can the Argentine squid suffer a decrease in abundance if the area is affected by climate change resulting in an increase in surface temperature? The researchers indicated that under the effect of climate change, considerable fluctuation and/or uncertainty is expected in the annual abundance of squid, as well as in that of different fishery resources in different regions of the world, due to changing oceanic and atmospheric dynamics at large. scale.

Given the persistent uncertainty, we consider that the study carried out should not be interpreted as a conclusive observation. However, it represents a valuable contribution that should be taken as an essential starting point to advance the understanding of the relationship between the abundance of squid and the atmospheric and oceanic variables that influence their development, generating changes in their distribution and abundance. In this context, it is suggested to strengthen these studies in Argentina, providing a more determined approach to comprehensively address the problem and contribute to knowledge, both from the public and private sector of a resource as significant as squid for the Argentina fishery.

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