MOBIMUTUNA

Context

Ocean temperature influences the behaviour, distribution and reproduction of Atlantic bluefin tuna, meaning that warming in the Mediterranean could alter the areas and periods with suitable thermal conditions for spawning.

Anticipating these changes is important for fisheries management, as shifts in spawning grounds or reproductive windows may require adjustments to fishing seasons and fishing gear used to target this species, including traditional tuna traps (almadrabas).

MOBIMUTUNA addresses this need by analysing isotopic information preserved in Atlantic bluefin tuna otoliths. Using δ¹³C and δ¹⁸O values, the project will reconstruct the thermal conditions experienced by individual fish throughout their life cycle and combine this information with climate projections to assess how thermal suitability for spawning in the Mediterranean may evolve in the future.

Objectives

The main objective of MOBIMUTUNA is to generate scientific evidence that will enable Spain’s General Secretariat for Fisheries to anticipate and plan potential adjustments to Atlantic bluefin tuna fishing gear and seasons in response to changes in thermal suitability in the Mediterranean.

To achieve this, the project aims to:

• Quantify the spatial connectivity of Atlantic bluefin tuna by estimating the proportion of individuals that predominantly use the eastern Atlantic–Mediterranean region and those that also use the western Atlantic.
• Define the species’ optimal temperature range and thermal tolerance limits, including variability between individuals and throughout their life cycle.
• Assess current thermal suitability for spawning in the Mediterranean and project how it may change under different warming scenarios.
• Determine when and where the Mediterranean may retain or lose suitable thermal conditions for reproduction.
• Generate information to help anticipate potential adaptations to fishing gear and fishing schedules.

Expected results

MOBIMUTUNA will provide a quantitative assessment of the optimal temperature range and thermal tolerance of Atlantic bluefin tuna, based on high-resolution isotopic profiles obtained from otoliths and used to reconstruct thermal conditions throughout individual life cycles.

The project will also develop operational thermal indicators, including thresholds, critical temperature ranges and periods of thermal suitability, as well as maps of current and future thermal suitability for spawning in the Mediterranean.

These results will help identify potential spatial and temporal shifts in conditions suitable for the species’ reproduction under different warming scenarios.

Expected impact

The findings will provide Spain’s General Secretariat for Fisheries with a scientific basis for anticipating how changing thermal conditions in the Mediterranean may affect Atlantic bluefin tuna spawning and support fisheries management decisions.

In particular, they will enable earlier assessment of potential needs to adapt fishing seasons, schedules and gear, including traditional tuna traps (almadrabas), in response to projected changes in the areas and periods with suitable thermal conditions for reproduction.

Funding