The debate about the impact of fishing on different species has already gone on for 50 years. A recent study concluded that populations of tuna and similar species have been cut by 60% on average throughout the world over the last century.

The project published by the Proceedings of the National Academy of Sciences (PNAS) journal adds that most of these populations have been exploited to the limits of sustainability, and there are many species that have been overexploited.

The populations that have had their abundance most affected are cold water tuna, such as the Atlantic bluefin and the southern bluefin, which have decreased by 80%. These species are big, long-lived and high in economic value.

Mackerel, which are smaller and have shorter life cycles, have also experienced a significant reduction in abundance. According to the project, this information suggests that fishing can be a threat to all species, regardless of their size.

María José Juan-Jordá, researcher at the University of A Coruña (Spain) and main author of the study declared that "the results of this study, which are based on a compilation of more precise estimates, show a global situation of tuna populations that differs from bleaker past interpretations."

A study published in Nature journal in 2003, which concluded that the abundance of pelagic fish, mainly tuna, had reduced by 90% in the past century. Despite this, we are reminded that "there are worrying factors that regional fishing organisations should solve in order to ensure a sustainable future is these fisheries."

In the opinion of the authors, management of tuna populations can work "although with some species, fishing management needs help. The ones with the highest economic value are the most over-exploited. There are clearly still people who benefit economically from illegal fishing of bluefin tuna, a case in which international trade goes beyond international fishing regulations, which are usually effective" states Nicholas Dulvy, a researcher from University of Simon Fraser (Canada), who also participated in the study.

Juan-Jordá adds that "fishing management organisations must not just use their resources to manage high-value species, such as large tuna, but also for species of lower economic value, which are important as they are a big source of protein for many developing countries."

The study suggests that increasing hauls can continue to be risky and that as the demand keeps growing, any global fishing effort should be made with "a lot of care." Iago Mosqueira, a fishing scientist from the European Commission and co-author of the project points out that "therefore everyone must concentrate now on creating a real future for these populations and the fisheries that depend on them."

In the opinion of Juan Freire, Professor from A Coruña University, and participant in the study "serious efforts and effective action are needed to reduce global overfishing, to recover overexploited populations and regulate trade that endangers them. Only then can we guarantee bigger catches, stable financial profits and reduce our impact on marine ecosystems."

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Journal Reference:

1. M. J. Juan-Jorda, I. Mosqueira, A. B. Cooper, J. Freire, N. K. Dulvy. Global population trajectories of tunas and their relatives. Proceedings of the National Academy of Sciences, 2011; 108 (51): 20650 DOI: 10.1073/pnas.1107743108