• Substantial loss of size, drop in biomass, sardines have been a concern for years in the Mediterranean.

  • The small pelagic holds an important place in the food chain and for the economic sector of fishing.

  • Ifremer has determined that the drop in the number and quality of plankton, linked in particular to global warming, is at the origin of this change in metabolism.

The phenomenon has worried the industry for years.

The size of sardines has sharply decreased in the Mediterranean in recent years, from an average of 15 to 11 cm.

And the proportion is even worse in terms of weight, since the biomass of these small pelagics has dropped from 30 to 10 grams on average.

After several years of research, Ifremer has confirmed the hypothesis made in recent years.

“It is neither fishing, nor natural predators [tuna or dolphin], nor a virus that is the cause, but their diet, underlines the institute.

Plankton is less nourishing, which has just been confirmed by the results of the Mona Lisa scientific project.

"

15% drop in the amount of microalgae

The concern has been identified.

It is located at the base of the food chain.

“Satellite images clearly show a drop in the amount of microalgae in the mid-2000s, by up to 15%.

That is to say, when we began to observe the sardines size down "specific

e

Jean-Marc Fromentin, a researcher at Ifremer, in Sète.

Fewer microalgae, smaller and less energetic plankton.

The problem reverberates at every level of the chain.

Their origin undoubtedly stems from significant regional environmental changes and in particular the global increase in temperature of 0.5 ° C in 30 years on average in connection with climate change.

To demonstrate the correlation between the change in diet and that of sardine metabolism, Ifremer carried out an experiment with 450 of these fish in the experimental station of Palavas-les-Flots, near Montpellier.

They were divided into four groups, with the size and quantity of food as variable.

Fish fed with prey of the same size and quantity as in the past have returned to their pre-2008 size.

Smaller sardines, a big problem for fishermen

“With small-sized foods, the sardines consume their prey in“ filtration ”mode through their gills, which implies sustained swimming for a fairly long period, details Ifremer.

With large foods, the sardines gobble up their prey one by one, which requires a much shorter sustained swimming time and therefore less energy expenditure.

"

The industry now knows the origin of the problem.

But this defect in the trophic chain has very worrying consequences for professionals.

They find themselves faced with the lack of outlets to sell these smaller catches.

Montpellier

Montpellier: But why are sardines affected by dwarfism?

Montpellier

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