SHIP WORM ON ATLANTIC COAST 99 



SESSIONAL PAPER No. 38a 



Another factor of importance in controlling the distribution of Teredo is salinity. 

 There appears to be general agreement among shipping men and others familiar with 

 the work of Teredo that any considerable amount of fresh water is fatal to it. On this 

 point, Mr. H. E. Miller states that "where the flow of fresh water is sufficient to have 

 any effect on salinity there is an entire absence of Teredo."^ 



The speedy destruction of T. navalis already alluded to which results when it is 

 brought into St. Johns harbour on ships is doubtless due to its inability to withstand 

 brackish water. While this factor would explain its absence from certain bays and 

 estuaries of the Bay of Fundy, neither salinity nor temperature will afford a satisfac- 

 tory explanation of the general scarcity or absence of Teredo in these waters. If tem- 

 perature alone were sufficient to bar Teredo from the Bay of Fundy it is difficult to 

 understand how lUyanassa ohsoleta, one of its congeners in the Acadian colony of the 

 gulf of St. Lawrence should be able to make its way into the shallow bays on the east 

 side of the Bay of Fundy, where I have found it at most points where I have dredged. 

 This species on the opposite side of the Bay of Fundy is rare or absent.^ One of the 

 peculiarities of T. navalis is its aversion to water containing sediments or other impur- 

 ities in suspension. Various writers have noted this aversion. The waters of the Bay 

 of Fundy are unique in their extreme turbidity ; no other waters on the American 

 coast approach them in this respect. This is due to the very high tides, and the corre- 

 spondingly swift currents in the estuaries which keep the waters near the coast every- 

 where turbid with sediment. In the Bay of Fundy there is a tidal range of 40 to 60 

 feet. In Northumberland Strait where Teredo is abundant the tidal range is in the 

 neighbourhood of 10 or 12 feet. The turbidity of the Bay of Fundy waters, particularly 

 in the upper and narrower portion of the Bay, exceeds that of Northumberland strait 

 in somewhat the same proportion as its tides exceed those of the strait. The high 

 turbidity of the estuarine waters of the Bay of Fundy is believed to be chiefly respon- 

 sible for the general absence or scarcity of Teredo. Barrows-^ has pointed out that a 

 definite correlation exists between the rock boring habit and a location on the open 

 coast. The need of protection from the waves at and near the tide line on open coasts 

 doubtless developed rock boring as a protective measure. This normal open-coast 

 environment which involved exposure to the surf included the normal salinity of the 

 open sea and comparative freedom from silt. The heavily silt laden waters of the upper 

 part of the Bay of Fundy afford the very antithesis of the open coast environment 

 which is normal tc rock boring molluscs and in this fact is to be found the explanation 

 of the absence or scarcity of T. navalis as well as the rock borers Zirfaea crispaia and 

 Petrioola pholadifonnis in the Bay of Fundy. 



ASSOCIATED SPECIES. 



A small crustacean, Limnoria lignorum, is associated with Teredo in some parts 

 of its range whose wood-destroying habits are similar to those of Teredo. These 

 two species which are similar only in habits, differ sufficiently in their preference 

 for certain environmental factors to lead them to reach their maximum numbers and 

 development along different parts of the coast line. Their zones of habitat, however, 

 overlap according to Murphy. This author states regarding the areas occupied by 

 these two species that " wooden wharves or bridges along the Bay of Fundy and 

 from there along the Atlantic coast as far as Whitehaven suffer from the Limnoria, 

 while the location of the Teredo is farther east and north." ..." There is no 

 neutral ground between them. Their domains overlap for a few miles, each of the 

 little borers becoming less abundant as we advance farther into the territory of the 

 other."-! 



1 Letter to the writer. 



2 Huntsman, Dr. A. G. Letter to the writer, February 5, 1917. 



3 Barrows, A. L. The Geologic Significance of Fossil Rock-Boring Animals, Bull. Geol. Soc. 

 Amer., Vol. 1917. 



4Proc. and Trans. N.S. Inst. Sci., Vol. 8, 1895, p. 218. 



