By Janet Tappin Coelho
Dolphins are dying in their droves leaving environmentalists in Brazil confounded as to the reasons why.
Around 88 gray dolphins have died from an unknown cause in less than a month in Sepetiba Bay, a region on the west coast of the state of Rio de Janeiro around 80km from the world-renowned city.
According to researchers at the Gray Dolphin Institute (IBC), based in Rio, nearly five porpoises are found floating lifeless every day.
The mass deaths have alarmed the scientific community which says if this rate continues, gray dolphins are at risk of disappearing altogether from Rio in a matter of months.
Sepetiba Bay has the highest concentration of gray dolphins in the world with an estimated population of around 800.
Researchers at the University of Rio de Janeiro (Uerj) are working around the clock on the carcasses to diagnose the cause.
Biologist Rafael Carvalho from Uerj’s Laboratory of Aquatic Mammals, Bioindicators and Oceanography Faculty said: “We’re still collecting evidence from the water to try to discover the reason for the deaths. Why this high mortality.
“We’re hoping to release our findings by the end of January and cannot speculate until we have all the facts before us.”
Many of the dead mammals are found emaciated, suffering from skin lesions and cloudy eyes indicating some form of corneal disease.
Biologist Leonardo Flach from the IBC said the inexplicable deaths are extremely worrying.
“We are facing a real tragedy in the dolphin population in Rio,” he said.
“Since December 16 we have collected between four to five dead porpoises a day.
“This is a shocking figure given that the normal mortality rate, until a few weeks ago, used to be five per month. Even this was considered unsustainable for the dolphin population and now we have already lost more than 10 percent in a few days.
“Twenty years ago, there were over 2,500, today the figures are less than a third,” the biologoist lamented.
Mass mortality among the dolphin population happens around the world due to a range of factors including over fishing on a large scale, acute chemical pollution such as oil spills or red tide – a harmful environmental condition where algae blooms out of control producing toxins affecting the marine ecosystem and people.
The Sepetiba Bay is bordered by condominiums, shipyards and ports but marine biologists said there is no evidence any of these issues have occurred in the area.
A video filmed by IBC shows the moment a biologist comes across a dead porpoise floating in the bay and starts the process to retrieve the creature’s body from the water.
According to scientists, this is the time of year when the dolphins should be leaping and diving as they race through the waves.
Instead the creatures are washing up lifeless in their dozens on seashores having apparently suffered a distressing death.
The gray dolphins, known for their gregarious nature, live in communities of up to 200 individuals and generally work together catching fish, procreating and protecting against predators.
The downside is, if the mass deaths are being caused by a viral disease or bacteria, the symptoms are likely to spread very fast because of their close relationships.
“There is no possibility of treatment in the wild,” admitted Mr Flach.
“If a pathogen-related disease specific to gray dolphins is diagnosed we may face a massive loss of 70 to 80 per cent of the population.
“It doesn’t bear thinking about and it will be devastating if this occurs.”
The institute is calling on Brazil’s environment agency to consider creating a marine protected area as a haven for those dolphins that survive, so the population is not completely wiped out by what could be the outbreak of an epidemic.