226 



BULLETIN OF THE BUBEATJ OP FISHEKIES 



only while in the cyprid stage, it is apparent that fouling by barnacles could occur 

 only from July to late September in this region. Of the three hydroids listed in his 

 report, which are occasionally found on ships' bottoms, it is of interest that the major- 

 ity are also present as larvse during the late summer months. 



Although a few additional scattered references to similar data could be listed, 

 they are extremely meager, and there are almost no data available on the subject 

 of seasonal distribution and periodicity (especially with reference to the larvse) 

 that are at aU comparable to the complete study of this subject with reference to 

 the boring moUusks (Teredo and Bankia), which so severely attack all marine struc- 

 tures, especially piling, buoys, and wooden vessels. (See Atwood and Johnson, 1924.) 



SEASONAL PERIODICITY 



During this investigation, while examining the bottoms of more than 250 ships, 

 it has been possible to secure some additional data, but relatively few are of an 

 BOSTON- NEW YORK —r- NORFOLK-— BEAUFORT- — 



Fig. 30. — Prevalence of the larvse of organisms that cause fouling at Boston, New York, Norfolk, and Beaufort, N. C. 

 From data gathered from ships' bottoms and test panels 



exact nature because few ships are docked within 90 days of their previous docking, 

 consequently it was only on rare occasions that the exact time of attachment for 

 specific organisms could be determined. However, from the few ships that docked 

 within 30 days of their last previous dry docking, as well as from vessels that were 

 in a given port continuously, it has been possible to prepare some incomplete but 

 fairly accurate charts for fouling in the harbors at Boston, New York, and Norfolk, 

 and at Beaufort, N. C. These are given in Figure 30. 



By referring to this chart it will be seen that the periods of active fouling vary 

 with the kinds of fouling. Thus, the hydroids and algae are late winter and early 

 spring forms; while many of the barnacles, the oyster, and the bryozoan Bugula 

 are late spring and summer forms, and some barnacles and the tunicate Molgula 

 are late summer or early autumn forms. Each of these is found earlier in southern 



