224 



BULLETIN OF THE BUREAU OF FISHERIES 



in these ports continue to grow ia the neighboring harbors just as rapidly and liixu- 

 riantly as if the vessel had remained in the original port during the entire interval. 

 It is doubtful if a series of ports can be found anywhere else iu the world having so 

 similar environmental factors that determine the ecological conditions for rapid 

 growth of fouling organisms. 



In contrast with this route, vessels returning from South American ports are 

 frequently clean, or at best only lightly fouled. Vessels iu the trans- Atlantic service, 

 whether passenger or freight, rarely show heavy fouling unless delayed in some port 

 for a considerable length of time. 



FiQ. 29. — Route taken by certain of the freighters operated by the United States Shipping Board. Many of the ports are in 

 the same latitude and all are in a similar geographic area 



The type of foiiling is very specific for certain routes, or at least for certain 

 waters. Thus, naval vessels that practice in southern drill grounds at Guantanamo 

 Bay, Cuba, West Indies, have characteristically large numbers of Balanus impro- 

 visus, B. ampMtrite, and Memiranipora lacroxii. Vessels that remaiu in the western 

 Atlantic, north of the Chesapeake, have characteristic growths of B. eburneus and 

 Tubularia. Vessels that visit the ports of the east coast of South America usually 

 have growths of B. tintinahvlum and B. ampMtrite, although if no extended time 

 was spent in these ports, or if these were river ports, such vessels would have clean 

 bottoms. 



It can be stated definitely from all data available that vessels that visit ports 

 in tropical regions usually are more foul than those that ply more temperate zones. 



