98 J. Douglas Oliver 



reported for fishes in other types of habitats (see comparisons in the 

 following discussion). 



The diet of L. ommata in the Okefenokee marshland was mainly 

 chironomid larvae and other insects, as well as Cladocera. Similarly, in 

 the St. Johns River system of north Florida, L. ommata ate mainly 

 chironomids, Cladocera, and Copepoda (McLane 1955). In the 

 Okefenokee, Gambusia affinis consumed mainly chironomids, odonates, 

 other insects, and Cladocera (Table 1). Similarly, G. affinis in shallow 

 areas of Wheeler Reservoir, Ala., ate mostly Entomostraca (presumably 

 Cladocera or Copepoda), Chironomidae, and other juvenile insects 

 (Anopheles, Hess and Tarzwell 1942). In California rice fields, G. affinis 

 ate mostly Cladocera and immature Chironomidae (Washino and 

 Hokama 1967) and some Ostracoda (Farley 1980). Those in California 

 ponds ate mostly Cladocera (Miura et al. 1979). Thus, in Okefenokee 

 marshes, the fishes fed primarily on the same kinds of foods that they 

 ate in other localities and in different habitats. The two fishes in the 

 Okefenokee freshwater marsh ate oribated mites, which are often 

 associated with an algal, detrital system of this kind (Pennak 1978), but 

 Oribatei were a minor component of their diets (Table 1). 



Both fishes showed peak consumption rates at about the same time 

 of day, the afternoon. The afternoon had bright sunlight and the highest 

 temperatures of the day, and these factors may have contributed to 

 increased consumption by fish (Reddy 1975, Mann 1978, Smagula and 

 Adelman 1982, Garcia and Adelman 1985), and high illumination may 

 make foods more conspicuous, particularly in a vegetated blackwater 

 environment. 



Evacuation rates of the two fishes were alike, and similar to rates 

 reported for other fishes. Foregut evacuation rates were 0.143 and 

 0.279/ hour for L. ommata in winter and summer, respectively. Similarly, 

 rates for G. affinis were 0.157 and 0.262/ hour. Doble and Eggers (1978) 

 reported rates of 0.109 and 0.267/hour for small juvenile Oncorhynchus 

 nerka Walbaum in winter and summer. Ruggerone (1989) measured 

 evacuation of 0.274 to 0.329 for Oncorhynchus kisutch Walbaum at 

 13° C. Persson (1982) found rates of 0.129 and 0.499/hour for Rutilus 

 rutilus L. held at 12 and 24° C in the laboratory. Amundsen and 

 Klemetsen (1988) reported rates of 0.08 to 0.16/ hour for Salvelinus 

 alpinus L. at 13°C. Thus, evacuation rates for L. ommata and G. affinis 

 appear to be well within the range of values reported for various fishes. 



Because evacuation rates are similar to rates of other fishes, 

 consumption measures of Gambusia and Leptolucania in the Okefenokee 

 Swamp are in the same range as estimates for other species. Daily food 

 consumption by L. ommata was 24.2 and 93.1 mg/g/day (dry weights), 

 in winter and summer, respectively. Values for G. affinis were 32.1 and 



