Necturus lewisi Study: Distribution & Ecology 23 



Table 5. Comparative Necturus lewisi capture success for different amounts of 

 precipitation within a sampling period. Number of sampling efforts in 

 parentheses; percentages are success rates for each category. 

 Capture Levels of precipitation (in.) 



success 







.25" 



(86) 



(22) 



20.4% 



(108) 



.25-.5" 



(40) 



(14) 



25.9% 



(54) 



.5-1.0" 



(54) 



(11) 

 16.9% 



(65) 



1.0-3.0" 



(24) 



(7) 

 22.6% 



(31) 



3.0"+ 



Negative 

 Positive 



Totals 



(301) 



(74) 

 19.7% 



(375) 



(3) 



(2) 



40.0% 



(5) 



Table 6. Comparative Necturus lewisi capture success at different levels of tur- 

 bidity (Secchi disc). Number of sampling efforts for each turbidity level 

 in parentheses; percentages are success rates for each category. 

 Capture Turbidity (cm) 



success 



0-20 



(134) 

 (64) 



32.3% 



(198) 



21-40 



(94) 



(22) 

 19.0% 



(116) 



41-60 



(98) 

 (14) 



12.5% 



(112) 



61-80 



(93) 



(18) 



16.2% 



(HI) 



81-98 



(58) 



(15) 



20.5% 



(73) 



99+ 



Negative 

 Positive 



Totals 



(119) 



(27) 

 18.5% 



(146) 



some food items could have been trap assisted. Larval specimens were 

 dipnetted, thus their stomach contents may be more representative of 

 natural conditions. All specimens were collected from January to mid- 

 April and reflect feeding habits for that time interval. Initially, the two 

 size groups were divided into 10 mm size increments to check for 

 obvious size-related feeding differences. No such differences were found 

 within either group. The 36 larvae contained 197 food items (mean = 5.5 

 items/ specimen) and the 1 17 adults contained 1,435 food items (mean = 

 12.3 items/ specimen). 



The feeding habits of adult N. lewisi (Table 7) were more diverse 

 than those observed in larvae (Table 8). Arthropods accounted for 99% 

 of the food items in larvae, but only 74.1% in adults. Ostracods and 

 copepods, major elements in larval diets, were not found in adults. 

 Adults added to their diets two groups of mollusks, several vertebrates, 

 various terrestrial food items (Table 10), and other aquatic organisms 

 too large for larvae to eat. The types of dipteran larvae eaten are listed 

 in Table 9. The apparent shift in types of dipterans eaten seemed to 

 reflect a preference for larger dipteran larvae by adults. 



Data on digestive tract contents of 34 N. punctatus, collected sym- 

 patic with N. lewisi and divided into the same two size categories (20- 

 50 mm SVL larvae, N=14; 91-150 mm SVL adults, N=20), are presented 

 in Table 11. There was little deviation from the diet of N. lewisi. The 



