Global warming threatens Mediterranean bluefin tuna – A recent international study conducted by the University of Southampton, in collaboration with the AZTI Technology Centre and the British Antarctic Survey, points out that rising temperatures in the Mediterranean’s spawning grounds could jeopardise the long-term recovery of the bluefin tuna population.
Research findings indicate that rising temperatures in the Mediterranean Sea over the next 50 years could force bluefin tuna to rethink their spawning strategy in order to survive. What is currently the species’ main spawning grounds could become unsuitable due to the predicted temperature rise, pushing the population to seek new, more temperate regions.
Thus, according to the researchers, the population may have to migrate to other, more temperate regions. This would inevitably require a review of fisheries management to adapt to the future distribution of bluefin tuna and the creation of new areas for reproduction and productivity.
The researchers therefore state that temperatures above 28ºC will have a negative impact on the growth of bluefin tuna. In the next 50 years, the Mediterranean could become inhospitable forcing a potential relocation to other spawning grounds.
The western Atlantic will also become inhospitable for bluefin tuna
The western Atlantic is not immune to this trend. Bluefin tuna, which spawn outside the Gulf of Mexico, may seek alternatives due to rising temperatures in the region. This research indicates that populations in the Mediterranean and eastern Atlantic may be acting similarly, looking for alternatives for reproduction.
The research team, consisting of scientists from eight countries, used a pioneering method of analysis based on otoliths, traditionally used to determine the age of fish. In this study, otolith chemistry was used to measure the energy consumption of bluefin tuna. Temperatures above 28ºC showed a decrease in energy consumption, highlighting the potential negative impact on fish viability.
Professor Clive Trueman, lead author of the study emphasised that this innovative method uses changes in the stable isotopes of carbon and oxygen in otoliths to reveal the individual metabolic rate of each tuna. This ‘natural fitness tracker’ can indicate when waters become too warm to be hospitable for fish.
The spawning grounds of bluefin tuna are crucial for the production of new fish each year. If these areas become too warm, the productivity of bluefin tuna and the sustainability of the fishery could be called into question, unless the species can successfully adapt to new spawning grounds.
The alarm raised by this study, published in Nature Communications, underlines the urgency of considering conservation strategies to preserve the future of this iconic species.
Global warming threatens Mediterranean bluefin tuna
