By Darren Parkin
MARINE scientists in the Canary Islands are calling for a world-wide ban on the use of military sonar following a study which links mass whale strandings to naval exercises.
A recent study highlighted a connection between the use of sonar and strandings which have accounted for the deaths of dozens of whales.
It is now understood that a whale’s navigational senses could be severely impeded by the use of underwater military pulses which, according to marine biologists, may confuse the creatures.
Scientists say evidence points to the mammals attempting to escape the source of the sound in a panic, becoming disorientated and then, in certain circumstances, beaching themselves. Read more...
In some species – such as the beaked whale used in the study – the need to ‘take flight’ from the sound forces them into a deep dive, the following ascent from which can be too fast and lead to severe decompression sickness.
This, coupled with mass strandings, leaves the already-distressed mammal unable to survive the stress of becoming stranded, even if they are returned to the water after only a brief spell of being beached.
The researchers behind the study, from the University of Las Palmas de Gran Canaria, focused entirely on the beaked whale population around the Canary Islands.
Their evidence suggests that a 2004 ban on sonar in Canarian waters had proved effective in combatting the number of average strandings each year. However, the Canarian marine biologists are urging further action be taken where beaked whale numbers are dwindling. In particular, they point to the Mediterranean where the species is classed as ‘vulnerable’ and where many military vessels operate.
In the report, published in the ‘Proceedings of the Royal Society’ journal, the team from the University of Las Palmas de Gran Canaria called for action across the globe to reduce the use of sonar.
“Mass stranding events (MSEs) of beaked whales (BWs) were extremely rare prior to the 1960s but increased markedly after the development of naval mid-frequency active sonar (MFAS),” the report stated.
“The temporal and spatial associations between atypical BW MSEs and naval exercises were first observed in the Canary Islands, Spain, in the mid-1980s.
“Further research on BWs stranded in association with naval exercises demonstrated pathological findings consistent with decompression sickness.
“A 2004 ban on MFASs around the Canary Islands successfully prevented additional BW MSEs in the region, but atypical MSEs have continued in other places of the world, especially in the Mediterranean Sea, with examined individuals showing decompression sickness.”
Scientists held a workshop in Fuerteventura two years ago where they reviewed current knowledge on mass strandings of beaked whales associated with sonar activity.
“Spatial management specific to BW habitat, such as the MFAS ban in the Canary Islands, has proven to be an effective mitigation tool and mitigation measures should be established in other areas taking into consideration known population-level information,” the report added.
“Animals may respond to stressful situations by exhibiting the ‘flight or fight response’ with increased heart and metabolic rates, often accompanied by fast movement away from the perceived stressor.
“We recommend a moratorium on mid-frequency active sonar in those regions where atypical mass stranding events continue.”