64 W. J. Streever 



small animals suggests that recovery of crayfish population density is 

 not dependent on replacement through reproduction. Cave popula- 

 tions frequently display size distributions with many large individuals 

 and few small individuals, suggesting infrequent reproduction (Poulson 

 1963, Culver 1982). The fecundity of P. pallidus is unknown, but an 

 extensive study of the cave-adapted crayfish Orconectes australis 

 australis in Shelta Cave, Alabama, suggests that reproduction in cave 

 crayfishes may be infrequent and that clutch sizes may be small 

 (Cooper 1975). If a similar pattern occurs in P. pallidus, crayfish 

 population recovery that depends on reproduction could be slow. Be- 

 cause crayfish population densities in the Peacock Springs cave sys- 

 tem do not appear to be recovering through reproduction, the increase 

 in numbers along transects 1 through 6 may not represent a true 

 recovery of the crayfish population. Instead, crayfish density may be 

 the result of colonization by individuals that survived the kill and 

 are now moving into the portion of the cave where transects were 

 located. 



Catfish were not counted as part of this study. However, they 

 were common along transects before the 1991 kill, they were absent 

 from transects immediately after the kill, and they were common 

 during the 1994 census dives. An Asiatic clam population near the 

 mouth of Peacock III had an estimated density of 161 individuals/m 2 

 before the 1991 kill (Streever 1992a), but no live Asiatic clams were 

 found immediately after the kill or in 1994. Empty clam shells, pre- 

 sumably remaining from before the kill, were abundant. 



The causes of the kill and the factors affecting recovery are 

 unknown. However, intrusion of river water into caves typically full 

 of groundwater appears to be linked to cave kills in the Peacock 

 system. On 19 November 1994, two dead crayfish and a dead catfish 

 were found along transect 6, immediately after a period of flooding 

 during which Suwannee River water entered the cave. However, seven 

 live crayfish were found along the transect on the same day, so this 

 event did not have the intensity of the 1991 kill. Despite this apparent 

 association, the link between river water and crayfish mortality is not 

 clear. P. pallidus has been observed in two siphon-spring cave 

 systems flooded by Sante Fe River water throughout the year 

 (personal observation), so intolerance of low temperatures and other 

 environmental factors associated with river water may not be the 

 cause of mortality. Furthermore, kills have been observed in other 

 caves without flooding by river water (Franz et al. 1994). Establish- 

 ment of the cause of cave crayfish kills requires further investigation. 



