Seasonal Diet of Margined Madtom 31 
Table 4. Contribution (percent) of chironomids to the diet of four size classes 
of margined madtoms for each of the four seasons. a 
Season 
Size class (mm) 
<31 31 - 60 
(N = 1) (N = 18) 
8 £ 
1 n 
91 - 120 
(N= 16) 
Fall 
Winter 
Spring 
Summer 
- 79 (37.7 ± 5.9) 
- 67 (2.4 ±1.3) 
- 42 (19.3 ±6.8) 
94 (17 b ) 81 (49.3 ± 11.8) 
56 (20 b ) 
65 (46 b ) 
15 (9.2 ±4.3) 
51 (13.2 ± 4.1) 
43 (6.0 ± 3.8) 
27 (9.4 ± 2.3) 
18 (9.0 ±2.7) 
42 (6.3 ± 3.9) 
a Mean ± 1 SE in parentheses. 
b No SE shown because sample consists of one individual. 
long, were usually found on the upper surface of rocks. This was 
especially true for the filter-feeding Simulium. These taxa made up only 
9% of the diet of madtoms <60 mm long. Many of the prey were 
obviously too large for small madtoms to handle, e.g. late instars of 
Acroneuria, Stenonema , Isonychia, and Megaloptera, as well as crayfish. 
Consequently, we favor the idea that diet diversifies with increasing size 
because the larger madtoms (1) are able to capture larger prey successfully 
and (2) are able to forage in areas of higher current flow. Our data 
suggest that the diet of margined madtoms is strongly influenced by 
size-specific prey capture abilities and current velocity. These and other 
factors influencing the predatory behavior of many stream fishes, 
especially nonvisual predators like madtoms, deserve further study. 
ACKNOWLEDGMENTS.— We thank Jerry Diamond and Rob 
Edwards for helping with the collection of the madtoms. Bill Cooper, 
Dennis Mullen, and Mark Oemke reviewed earlier drafts of the 
manuscript. Comments by two anonymous reviewers improved the 
manuscript. This research was funded by NSF Grant DEB-8206910 to 
S. R. Reice. Contribution No. 649 from the W. K. Kellogg Biological 
Station, Hickory Comers, Mich. 
LITERATURE CITED 
Allen, K. R. 1941. Studies on the biology of the early stages of the salmon 
(Salmo salar). 2. Feeding habits. J. Anim. Ecol. 10:47-76. 
Burr, B. M., and R. L. Mayden. 1982. Life history of the brindled madtom 
Noturus miurus in Mill Creek, Illinois (Pisces: Ictaluridae). Am. Midi. Nat. 
107:25-41. 
