Attack of the Gribbles

Sounds like a science fiction title doesn't it? But the attack of the gribbles could be in most any shipyard, dock or under any wooden boat. These are one of the two animals that cause the most damage in wooden boats.

Gribbles are related to the lobster and crab. They are mostly a pale, white, small crustacean from one of the 56 species of marine isopods from the Limnoriidae family.

For a long time the gribble diet was a mystery; gribbles lack the nitrogen-fixing bacteria in their bellies that symbiotically allow termites and shipworms to survive on the carbon riches of wood. In other words, they were endlessly gnawing through wood that provided little nutrition or energy to them.

The secret is the wood in seawater, like our harbor estuary, has a slimy surface. That slimy surface, scientists have discovered, is the true diet of a gribble. And by tunneling through wood, and having succeeding generations of gribbles widen those protected tunnels, gribbles dramatically increase the surface area on which the nitrogen-rich microbial slimes can grow.

Gribbles and shipworms, another wood borer, were absent from many harbors for generations because pollution levels were too high, and oxygen levels too low, for them to survive. Strangely enough, the very polluted harbors were often known as "clean harbors" because they had local waters that were so toxic that the unwanted organisms would die off of ships. Luckily, many of these harbors are healthier and the gribbles are back.

At the shipyard, we have classic wooden ships and yachts. Careful maintenance of making sure the bottoms are painted and all the seams are sealed, prevents gribbles from damaging these ships and yachts.