whereas only solitary forms were found on panels exposed for periods 

 of 5 and 6 months. This is interpreted to mean that tunicates require 

 a particular substratum for optimum setting, and a 1-month or probably 

 2- month exposure period does not allow sufficient time for development 

 of this substrate. 



Tunicates apparently set in greatest numbers during autumn or early 

 winter. They exhibited no apparent preference for the concave or convex 

 side of the panel. 



7. Amphipods 



Amphipods appeared on the monthly panels in quantity from 

 July through December and in consistently greater numbers on the 

 cumulative panels as the total mass of fouling became greater. Am- 

 phipods apparently flourish as the density of hydroids increases. 

 Amphipods did not appear on the monthly panels from January through 

 March, probably because of lack of suitable habitat. 



IV. DISCUSSION 



The results of the first year's exposure of test panels in Thimble 

 Shoal Channel have provided relatively detailed and apparently con- 

 sistent information on the total fouling complex and the seasonal 

 variation of set and growth which occurred during the 1956-57 period. 



In this region of lower Chesapeake Bay the test panels accumulated 

 a total of . 3 1 ounces of growth (wet weight in air) per square foot 

 per year. The fouling complex consisted predominantly of barnacles, 

 calcareous tubeworms, hydroids, bryozoans, jingle shells, and tunicates. 

 Oysters, sponges, mussels, and sea anemones were also observed 

 in the fouling complex. For purposes of this study, the discussion 

 will be restricted to the predominant, permanently attaching forms. 



Figure 14 shows graphically the exposure period of each panel and 

 the predominant forms attaching to it. The 1-month panels show the 

 times of attachment of the various forms, whereas the 2-, 3-, 4-, 5-, 

 and 6-month panels serve to indicate cumulative fouling, succession 

 of the various forms, and probably most important, as a cross check 

 on the data obtained from the monthly panels. 



As an example of the consistency between monthly panels and panels 

 exposed for longer periods of time, consider the distribution of 

 tubeworms. These organisms were observed first in June but were not 

 observed on panels after October. These relatively sharp beginning 



