Seasonal changes in faunal abundance on intertidal flats are believed to be 

 due to life history events, such as mortality and recruitment, since little 

 evidence of active seasonal migration has been found among most infaunal 

 species (Little and Boyden 1976; and Stromgren et al. 1973). Passive 

 transport of infaunal animals by ice, waves, or on the surface film, may occur 

 to a limited extent. 



In a study of intertidal mud flats in the Sears Island area of Penobscot Bay 

 (region 4) the highest number of individuals per m^ (table 5-10) was present 

 in fall and the lowest in spring (Normandeau Associates 1975). Winter 

 mortality due to low temperatures and ice probably accounted for the 

 differences . 



The density of natural populations fluctuates widely over time. Dean and 

 Ewart (1978) have noted annual variations in the density of several common mud 

 flat species, including the Baltic clam, the gastropod, Hydrobia totteni , the 

 polychaetes Heteromastus f iliformis , , Scoloplos sp., and Streblospio benedicti 

 in Montsweag Bay (region 2). Some densities varied between years by a factor 

 of twenty. Dauer and Simon (1976) found that although great fluctuations 

 occurred in the density of sand flat animals over time the species composition 

 remained relatively constant. 



Deposit feeders were the most abundant feeding type on both the mud and sand 

 flats surveyed in Maine by Larsen and Doggett (1978a). Exceptions to this 



Table 5-10. Numbers of Individuals/m2 Collected on Intertidal 

 Flats in Upper Penobscot Bay (Region 4)^ 



Transect 



Summer Fall Spring 



1 

 2 

 3 



Totals 



a 



Normandeau Associates .1975. 



5-100 



