A new study by scientists from the University of Exeter and Bristol in the UK has shown that eels are losing the fight to survive when faced with marine noise pollution such as that of passing ships as they lose crucial responses to predator threats.
The study, published in the journal Global Change Biology, found only 38% of the European eels that were exposed to ship noise responded to an ambush from a predator compared to 80% in normal ocean conditions. And they were 25% slower to startle to an ‘ambush predator. Those that were pursued by a pursuit predator were caught more than twice as quickly when exposed to the noise.
Anthropogenic noise has in recent years been recognised as a major pollutant of international concern. With research showing disturbed communication, movement and foraging patterns in a wide range of species. The findings of the study suggests that acute acoustic noise such as that from passing ships may have serious physiological and behavioural impacts on species living in the ocean affecting compromising life-or-death responses.
Lead researcher, Dr Steve Simpson of the University of Exeter said; ‘over the past 20 years eel populations have declined by 90 per cent due to climate change. The eels are spawned in the Sargasso Sea, and then spend 18 months finding their way back to Europe. To do this they have to cross busy shipping lanes and acute acoustic events, like the noise of a passing ship, may be adding to the problems they have to overcome‘.
Physiological and spatial behaviour was also tested in order to understand what may cause the loss of crucial anti-predator behaviour seen. The researchers found that eels who experienced additional noise had diminished spatial performance and elevated ventilation and metabolic rates, these are indicators of stress, compared with control individuals.
The study highlights the importance of assessing the scale of impact anthropogenic noise that now pervades many coastal environments may have. Compared to many other pollutants underwater noise is a pollutant we have more control over, and by alleviating one of the many stressors eels are faced with globally, the authors believe the European eels would be more resilience to other stressors.