CORNISH, UK - The Government has confirmed that 20 ships were involved in an intense military exercise off the Cornish coast, just days before the mass stranding of dolphins this summer.
The death of 26 dolphins in the incident in June, most of them in the shallow waters of Porth Creek on the Roseland, was one of the UK's biggest wildlife tragedies in recent years.
Though up to 200 other dolphins were saved by the intervention of RNLI and wildlife volunteers, campaigners say that 80 more could have been traumatised by the incident.
The Royal Navy at first denied involvement in the disaster, but the Ministry of Defence (MoD) later confirmed it was carrying out exercises in Falmouth Bay just hours before the dolphins beached themselves.
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DON’T BE SO FAST TO BLAME MILITARY SONAR
A powerful thrusting seaquake ripped the seafloor apart near the Mid-Atlantic Ridge a little north of the Azores Triple Junction just 14 days prior to the stranding. Violent reverse-thrust seaquakes that occur in the top few kilometers of the rocky bottom are capable of producing hydroacoustic shockwaves that move vertically through the water column at more than 1,500 km per second. When these seismic waves strike the underside of the surface, the positive pressure goes through a 180-degree phase shift and bounces back as negative pressure (vacuum). This refection known as the "Llyod's Mirror Effect" drops the hydrostatic pressure to the point where the water starts to boil with cavitation bubbles.
The Deafwhale Society, Inc. suggests that the event in the Azores caused the stranding, not military sonar.
Pods of offshore dolphin feed mostly at night on squid that hang around mid-oceanic ridges, the most seaquake-prone areas in the world.
They use biosonar to find their food in the dark. Biosonar requires excellent binaural hearing in which the two ears can distinguish time of arrivals of the returning echoes in less than a few microseconds.
Stereophonic hearing underwater requires two unique features: (a) the earbones must be isolated from skull vibrations and other unwanted sounds, and (b) the desired echo must be directed to each ear is a special acoustic channel.
To isolate the cochleae, evolution suspended them on long thin ligaments and surrounded them with a series of small air sacs. The air in the sacs serves as a perfect acoustic scattering device bouncing the unwanted sound away for the inner ears.
To channel the sound, evolution equipped the whales with special acoustic fat below the lower jaw. These "windows" feed the returning echoes directly to the inner ears in a fashion whereby the vibrations stimulate the earbone from only one direction. Thus, by turning the head slightly left or right and up and down, the toothed whales can zero in on their prey.
The air sacs and other enclosed air spaces of the diving whales are subject to catastrophic failure if exposed to sudden and excessive alterations in the surrounding water pressure. Excessive and rapid pressure waves causes the volume of air in the acoustic deflectors (air sacs) to fluctuate too drastically and too quickly for the whales to compensate. The membranes surrounding these air sacs rupture, destroying the pod’s ability to dive and feed itself. Every exposed member is affected—not just the pod leaders.
Such a barotramatically-injured pod has no choice but to surface and halt all diving and feeding activity until the barotrauma heals. If the injury is not too severe and the pod finds food on the surface, they will likely be able to return to normal diving and feeding in less than ten days. On the other hand, if they do not recover within a few weeks, they will become dehydrated and their condition will worsen due to malnutrition and etcetera. They will likely reach a point of no return after ~3 weeks, becoming so weak that they can no longer avoid a stranding, especially at night during an incoming tide.
As indicated above, the trauma in the sinuses causes biosonar (navigational) failure so the pod can easily get lost at sea. Surface currents quickly turn the aimless animals downstream. They will huddle together for protection from sharks and swim along at 4-5 knots always headed in the path of least resistance (downstream) covering 100 to 125 miles per day. Land masses that extend out to sea that oppose the flow of current can often serve as giant catching arm systems to trap the non-navigating pod. So can the mouth of rivers when the tide is incoming.
The pod is also vulnerable to an encounter with a sonar ship since they have no idea which way to swim to avoid added injury.
Thus, the best answer for why the dolphins stranded in the river is barotrauma resulting from exposure to a series of dangerous pressure changes generated when a thrusting seaquake erupt in the seabed 1,400 miles east of where they beached.
. . . from the "SEAQUAKE THEORY" by CAPT David Williams
(david07 at deafwhale.com)
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