The future of the Valencian clóchina: production strategies to combat climate change

Miguel Jover Cerdá. Professor of Aquaculture at UPV

The Valencian clóchina (Mytilus galloprovincialis) is a highly valued aquaculture product in Valencia for its quality, produced artisanally in the 25 clochineras (or rafts) of the Port of Valencia and Sagunto. Its production dates back to the late 19th century, organized under the Unión Mejillonera del Puerto de Valencia, from which it was exported to other areas of Spain.

Production of 200 tons in 2010 has increased considerably, reaching 2,703 tons in 2024 according to MAPA data, with a first sale value of 4.3 million euros.
Clóchina aquaculture has faced several challenges, such as attempted brand usurpation, predation by gilthead bream, lack of criançó (seed), and reduction in first sale price and profitability, but in the future, climate change, primarily through increased seawater temperature and acidification, could have a negative effect on production, as reflected in scientific reports.

Increased water temperature causes mass mortalities in the Mediterranean according to the Aquaculture Advisory Committee (2025), and reduced growth as a consequence of thermal stress caused by reduced oxygen and increased metabolism, resulting in earlier harvesting in the months of March and April. The temperature tolerance limit is around 25°C, a value that is exceeded in the waters of the Port of Valencia during the months of June, July, and August, and furthermore an increase in average monthly values for August has been noted since 2012, from 27.5°C to values close to 30°C in July and August 2025, according to data from Puertos del Estado.

On the other hand, ocean acidification, as a consequence of atmospheric CO2 uptake, causes a reduction in the availability of carbonate ions in the water, generating problems with shell calcification, which is especially important during the first 24 hours of larval life, and if it does not occur adequately, survival becomes compromised. Furthermore, acidification reduces the attachment strength of the byssus to the ropes and losses due to water dynamics.

The interaction between both phenomena, temperature and acidification, makes clóchinas more sensitive to climate change, and the negative consequences on survival and growth could increase by 2050 if CO2 emissions are not addressed.

Local strategies by clóchina farmers in response to the situation are difficult and limited, as this is a global worldwide problem, but some biomass management operations could mitigate the negative effects. Advancing the production cycle is one of them, so that the season can begin during the months of March and April, as well as occupying the deepest zones of the ropes to reduce the effect of high temperatures during the summer months.

Likewise, water oxygenation could mitigate the reduction in dissolved oxygen as a consequence of temperature increase, but would entail an increase in production costs.
On the other hand, the lack of seed could be resolved through captive breeding of clóchina under controlled conditions and seeding on the rafts at the most appropriate times, although this is a medium-term option, as it requires optimization of the reproductive technique tested in the laboratory or pilot scale to make it profitable.

In any case, it would be advisable to have more information about the reproductive biological cycle of clóchinas on the rafts, their growth, their sexual maturation process and seed attachment, as well as environmental parameters in the water column—temperature, oxygen, pH, and food availability—in order to propose possible measures for improving production and adapting to climate change.
The Valencian clóchina is a product of the highest quality, local and sustainable, that generates wealth and employment, which is why measures are necessary to guarantee its production and profitability in the face of the negative effects of climate change.

With the support of: