247 



The probk-ms of how and whc-n this organism was introduced to San Francisco 

 Bay must doubtless always remain unsolved. It was not found here in an investigation 

 of shipworms made for the United States P\)rest Service by Kofoid and Armstrong in 

 1910-1911, nor was it brought to light in the biological survey of San Francisco Bay 

 in 1912-1913 by the United States Bureau of Fisheries and the University of California. 

 Barrows (1917) considers that the first infection probably occurred in the summer of 

 1913, during a period of increased salinity in .San Pablo Bay following a season of 

 unusually scant rainfall and consequently of lessened river discharge. The persistence 

 of such conditions the following year afforded an unusual opportunity for the organism 

 to become established in this locality and to spread to other portions of the bay. 

 The damage at this time, however, was not sufficiently serious to attract general 

 attention, and apparently abated the following year in conseciuence of a season of 

 more than normal rainfall and river discharge. 



A repetitit)n of the damage by Teredo was noticed in January-, 1917, on the outer- 

 most dyke at Mare Island. This was during a period of reduced river discharge, 

 following three years in which it had been more than normal. The maximum pene- 

 tration was about three inches, and the damage was not as serious as in 191,V1914. 

 By this time, however, the organism had apparently gained a thorough foothold in 

 the region, and conditions grew rapidly worse, shortly assuming the proportions of a 

 commercial catastrophe. 



In October, 1919, a dock at Oleum collapsed (see fig. 1), precipitating se\eral 

 loaded freight cars into the bay. In December of this year it was found that the piling 

 of the .Southern Pacific slips at Port Costa and Benicia had been penetrated by 

 Teredo to a depth of two or three inches, and in some cases the piles were almost 

 completely eaten through at the mud line. During this season the range of the borers 

 was extended upstream into Suisun Bay, at least as far as Martinez, where they were 

 found to have penetrated the piling of the wharf of the Mountain Copper Company 

 one-half inch by March, 1920. At this wharf, and probably at Port Costa and Benicia, 

 the borers were exterminated by the flood waters of April and May, 1920. But the 

 following summer and autumn were again favorable to the propagation and spread 

 of Teredo, and the record of this season is one of disaster unprecedented in the history 

 of the ravages wrought by marine borers. 



By the autumn of 1920 the borers had spread upstream until they reached 

 Antioch on the San Joaquin River, 25 miles above Carquinez Strait. In the upper bay, 

 from Pinole, through Oleum, Mare Island, Vallejo, Crockett, Port Costa, Benicia and 

 Martinez, to Avon, the destruction of piling by Teredo during this season reached a 

 climax which left little or no untreated piling intact, and much of it completely 

 destroyed by penetration to or near the center at the mud line. The nature and degree 

 of the damage at some of these localities is strikingly shown in figure 1. 



Above Martinez the attack was widespread, but owing to the adverse effect of 

 lower salinities the growth of the borers was slower, and the penetration of piling 

 was not sufficiently rapid or deep to attain the level of a commercial catastrophe. 



This progressive invasion was the direct result of a shortage of rainfall and run- 

 oft" during three years preceding the summer of 1920, which conduced to the settling 

 of the larvae on unprotected piling during the breeding season of the summer and 

 fall, and the survival of the borers in the wood during the brief seasons of the spring 

 freshets of those years. 



In the meantime the in\asion by Teredo navalis had spread elsewhere to unpro- 

 tected structures, such as those above Black Point on Petaluma Creek, to the wharves 



