RESULTS: The results of the population size surveys are 

 presented in Table 3, p. 7. As stated in a previous report 

 (Shelly and Schassberger 1990) , these figures are to be strictly 

 regarded as estimates. Nonetheless, they do indicate that 

 populations remained fairly stable in size from 1987 to 1989; 

 however, between 1989 and 1990, 20 populations were reduced in 

 size by at least 50 percent, and 14 were reduced by more than 75 

 percent of the previous years' estimates. Anomalies over the 

 period from 1987-1990 include the reduction in population size of 

 H. aguatilis in occurrence 012 between 1987 an 1989 (while most 

 other ponds remained the same or showed an increase in population 

 size) , and a slight increase in size of this same population in 

 1990 (while nearly all other ponds showed a reduction in 

 population size) . Population (026) showed an increase in 

 population size between 1987 and 1989 (similar to most 

 populations) , but the population size again increased between 



1989 and 1990 (contrary to all but population 012) . 



Also included in Table 3 are 1990 estimates of the percentage of 

 each pond that is occupied by H. aguatilis . These estimates 

 correlate well with the population size estimates (smaller 

 populations generally occupy the smallest percentage of suitable 

 habitat) . 



The results from the line-transect studies for three years are 

 presented in Table 4, pp. 8-9. The four ponds for which water 

 depth measurements were taken in both 1988 and 1989 were all 

 deeper during the second year, with pond numbers 020 and 027 

 significantly deeper in 1989. In 1990, pond number 008 was only 

 slightly less deep than in 1989, pond 013 remained the same 

 (013) , while the rest were slightly more deep. 



As reflected in the population size estimates for the five ponds, 

 line-transect data indicate that the percent cover of H. 

 aguatilis was significantly lower in 1990 than in 1988 or 1989. 

 Large population fluctuations reflect this species' annual habit, 

 and the apparent influence of fluctuating water levels on yearly 

 abundance. 



Freguency measures for the five line-transect ponds indicated a 

 less extreme drop in estimated population sizes between 1989 and 



1990 than either the population estimate or line-transect 

 methods. Results are presented in Table 4, p. 8. 



DISCUSSION: Populations were observed to be greatly reduced in 

 1990, as shown by the results of line-transect, freguency and 

 population size estimate studies. As stated in Lesica (1990), 

 the possible reasons for fluctuating sizes of H. aguatilis 

 populations include date of pond drying each year. The observed 

 decline in population size in nearly all the surveyed ponds in 

 1990 may reflect a suboptimal drying regime in 1989. Climate 

 data, including precipitation and temperature data from 



