576 ALSTON, LAWRENCE, BAYNE, AND CAMPBELL 



channels (channel 1, 0.78; channel 2, 0.65; channel 3, 0.41), and 

 there were no significant differences. 



Summer 



The plate-sampler data indicated that D in 1975 for channel 1 

 was significantly greater than that for channel 3. Dredge-sample data 

 for this same time did not indicate that channel 1 was significantly 

 different from the other channels, hi 1976, however, D (2.40) for 

 channel 1 was significantly higher than for either channel 2 (0.98) or 

 3(0.76). 



Fall 



The plate-sampler data indicated that D for channel 1 in 1976 

 was significantly greater than that for channel 2 or 3. The D for 

 channel 2 was highest, 3.10, compared with 2.20 for channel 1 ^ ' 

 1.89 for channel 3. 



All Seasons 



The following overall mean diversities were computed for each 

 channel for all of the periods and years and were compared using 

 Duncan's new multiple range test [means underlined with a common 

 line were not significantly different, (P - 0.05)] . 



Selected Fish-Food Organisms 



Oligochaetes 



In general, there were more oligochaetes in channel 3 than 

 channel 1 . One of the species of oligochaetes which was prevalent in 

 channel 3 was Branchiura sowerbyi Beddard (family Tubificidae), an 

 exotic species that was introduced into Europe and North America 

 from Southeast Asia on tropical and subtropical plants (Aston, 1968; 

 Brinkhurst and Cook, 1974). 



Snails 



During the summer of 1975, channel 2 maintained the highest 

 population of snails, with an average of 960 individuals/m-^ . The next 



