Teredo navalis is likely to occur in association with other shipworm species within submerged timbers.Invasion History: Teredo navalis has been transported by ships for so many centuries that its historic native distribution cannot be known with certainty. Its center of endemism is believed to be European, however; there exists substantial evidence supporting the assertion that the species is correctly considered exotic and introduced on both coasts of the Americas (Ruiz et al. 2000, NIMPIS 2002).In 1839, T. navalis was first reported in Massachusetts Bay in the sheathing of foreign wooden vessels. A century later the species was abundant in samples taken fromm Nova Scotia to Massachusetts The species was first collected from Long Island Sound in 1869, again from the timbers of a sailing vessel. Within several decades the species was collected in abundance in test boards from all around New York Harbor (Brown 1953).This shipworm occurred at low densities around Chesapeake Bay as early as 1878. As recently as the mid 1950s, the species was reported as rare in Chesapeake Bay (Andrews 1956). Subsequently, T. navalis has been collected from North Carolina and southward to Florida, Texas, the Bahamas, and Puerto Rico (Brown 1953).On the U.S. west coast, introduction of T. navalis into San Francisco Bay in 1913 led to a serious invasion and substantial negative economic impact (Cohen 2004). Potential to Compete With Natives: Where Teredo navalis co-occurs with native shipworm species, some degree of resource competition is likely. Possible Economic Consequences of Invasion: Turner (1966) proposed Teredo navalis as likely the most widespread marine wood borer in the world. The historic negative economic impacts of T. navalis invasion may rival those of any other introduced marine species. It is the species believed responsible for a massive infestation of Dutch dikes in the 17th century. It was also described by a Dutch commission in 1731 as a "horrible plague" threatening to destroy the dikes protecting the lowlands of Holland (Cohen and Carlton 1995, Reise et al. 1999). The damage inflicted by the shipworms prompted replacement of wooden dikes with stone.Massive T. navalis infestation was also responsible for the destruction of an unknown number of wharves, piers, ferry slips and other wooden harbor structures at a rate of a major structure a week for a period of two years in San Francisco Bay from 1919-1921. Cohen (2004) notes that in current dollars this would have equated to between $2 billion and $20 billion in damage.In general T. navalis has a centuries-long history of causing damage to sailing vessels, piers, pilings, marinas, and any other submerged wooden structures. In 1946, shipworms were estimated to cause $55 million/year of damage to waterfront structures in U.S. (Scheltema and Truitt 1954).
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