WE HAVE been hurtling south through marshes for half an hour when Brad Robin kills the engine of his flat-bottomed oyster boat. Having already fallen off my stool once, I grab a metal rail. We鈥檝e arrived at our first stop 鈥� the mouth of Lake Jean Louis Robin in south-eastern Louisiana, in the middle of the marshlands that border the Gulf of Mexico. Here, the Robins have bred and harvested oysters for generations.
Robin and his crew throw a net over the side and haul in the catch. Dozens of palm-sized eastern oysters, , clatter onto a plastic tray. 鈥淢ostly boxes,鈥� says Ed Cake, a marine biologist with Gulf Environmental Associates in Ocean Springs, Mississippi. He holds one up for me to see. The shell hangs open, empty. Cake estimates that 75 per cent of the shells in the catch are boxes.
Mortality rates are normally closer to 5 per cent, but that changed in the aftermath of the Deepwater Horizon oil spill this year. How fast the industry rebounds depends on an event expected sometime in the next few weeks, and Cake and Robin are eagerly searching for early signs of it.
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The event is the annual spatfall, when oyster larvae cement themselves onto old oyster shells and other material on the sea floor. After the spill, the Louisiana state authorities took an unprecedented decision designed keep the oil at bay and save the local oystermen, but which could also doom them: they maxed the flow of fresh water through the region鈥檚 canals to three times usual levels.
Oysters thrive in about 2 per cent salinity. After the flush, salinity fell to near zero at the mouth of the canals, and this is likely what killed most of Robin鈥檚 harvest. Yet, like many other oystermen, he supported the decision, hoping that larvae further out where salinity stayed higher would be saved from the oil and brought ashore by local currents.
Oysters in the Gulf take about two years to mature, so if spatfall happens as normal, Robin could be harvesting oysters again in 2012. If it fails, that could get delayed six months or more.
Early signs are promising. As we travel further towards the Gulf, only 20 per cent of the oysters come back as boxes. The freshwater inundation may even boost yields in the long run. Though each female produces from 75 to 150 million eggs, only 1 in 1000 survive. With so many empty shells now scattered on the sea floor, the larvae have more to latch onto, improving their odds. Moreover, the flush killed oyster predators as well as oysters. Boring sponges, for instance, are noticeably absent from the fresher inshore waters.
History suggests a bumper crop could occur within five years. After hurricane Katrina wiped out Gulf oysters in 2005, harvests recovered to 85 per cent of pre-Katrina levels by 2009. By early 2010, oystermen were bringing in record numbers. Then the oil spill happened.
On the boat, Robin squints at a white speck on the shell of another box oyster. It鈥檚 a spat. 鈥淚t looks like they鈥檙e trying to come back,鈥� says Cake. Now all they can do is wait and hope for a longer gap between catastrophic events 鈥� a tall order in the Gulf of Mexico.
