How the P.E.I oyster fishery could find a way out of its MSX crisis

MSX, a pathogen deadly to oysters, has struck two different parts of the U.S. coast in the last 70 years. P.E.I. could look to that experience to mitigate the pain now that the disease has been found in Island waters.

MSX was found in Bedeque Bay, about 20 kilometres west of the Confederation Bridge, two weeks ago, and has since been identified in three other locations around P.E.I. Those areas have been quarantined, but the discovery raises questions about the future of the industry for the whole province.

Ryan Carnegie of the Virginia Institute of Marine Science has been researching MSX — multinuclear sphere X — for 22 years, and knows well the devastation it can cause in oyster populations.

"My fear is that there is a near-term period of some pain ahead with regard to the wild fishery in P.E.I.," he said.

"MSX is a very acute disease that can cause very high levels of mortality, and we've had a painful experience with that in the U.S."

While harmless to humans, MSX can cause mortality of 80 to 90 per cent when it strikes a new population of oysters, Carnegie said.

MSX hit Chesapeake Bay in 1959.

At the time, the industry didn't know what to do about it, and the solution settled on was abandoning oysters altogether. The Chesapeake Bay industry turned to other species, such as clams.

Nature, however, had its own solution.

"It's not a gentle agent of natural selection. It's a sledgehammer," Carnegie said of MSX.

"The oysters that don't have the right set of genes are not going to survive for any length of time. So it very quickly will select for oysters that have what it takes to survive."

So while wild populations will crash, the progeny of those oysters that survive will carry MSX-resistant genes, and also survive. While the people making a living in the waters of Chesapeake Bay were looking the other way, the oysters returned.

Wild populations will recover from the advent of MSX, but it does take time. In evolutionary terms, because the pathogen is so deadly, this happens very quickly, said Carnegie, in two to three generations.

But that equates to eight to 10 years before an oyster population gets seriously on the path to recovery — too long for harvesters wondering how they are going to make a living.