FOULING OF SHIPS' BOTTOMS 



223 



WATERS CRUISED 



Associated directly with the duties of a vessel is the cruising record, indicating 

 by its log where the vessel has been and what ports were visited. Thus, of the boats 

 examined for this report the passenger vessels were on the trans-Atlantic service or 

 the South American or Mediterranean routes, while the freighters had an even wider 

 range of routes. Some of those examined plied regularly between New York and 

 the west coast of South Africa, others between New York and the Mediterranean 

 or New York and our west coast, or even New York and the East Indies. 



Naval craft, as a rule, do not have regular definite routes, consequently much 

 of the data in Table 1 is of little use in an analysis of the relation between routes 

 and the amount of fouling. 



In those cases, however, where it has been possible to study the effect of dif- 

 ferent routes traversed by different ships it has proved to be one of the most in- 

 teresting problems encountered during the entire study. Just as the flora and fauna 

 of the Tropics is different from that of the Arctic regions, and just as the trees of 

 California are different from those found in Maine, so the growths attaching to ships 

 in the China Sea are markedly different from those attaching in the North Atlantic 

 or from those of any other geographic region. In other words, each vessel, if foul, 

 shows at the time of docking, by the growths found on its bottom, a visible record 

 of its cruise. 



This report is not the place for a discussion of the geographic range of various 

 species of organisms but a discussion of their effect on fouling will be in order. 



One of the effects which was noticed early and was confused on many occasions 

 is that found when a ship fouled in a tropical port arrives in a northern port, 

 or vice versa. On such ships all growths are dead, either in a putrid condition 

 or leaving behind only their skeletons or shelly growths as a reminder of the once 

 abundant life. {Nevada, January 5, 1923.) Even ships moving from one port to 

 another 500 miles away usually exhibited a similar state. {Leviathan, May 18, 1923, 

 Norfolk to Boston.) 



While it can be stated as a general rule that vessels that remain only a few days 

 in one port and then move on to another remain free from fouling, there are certain 

 noticeable exceptions. This is the case with freighters of the United States Shipping 

 Board, which ply between New York and the west coast of Africa. Almost without 

 exception these vessels were found to be heavily fouled, in spite of short dry-docking 

 periods (five to six and one-half months), and in spite of the fact that rarely did 

 they remain in any one port for more than three or four days. By an examination 

 of Figure 29, which indicates the geographical relationship of the routes taken by 

 these ships, it will be seen that although they moved from port to port almost daily 

 yet these ports are very close together and most are in the same latitude; that is, they 

 are in a similar geographical area, with environmental conditions comparable if not 

 identical. It is evident, consequently, that the effect of change of port on growths 

 causing fouling would be very slight, if any, and it is very evident, as seen by the 

 records of examination of such ships, that the barnacles and hydroids that attach 

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