100 J. Douglas Oliver 



1989) for each of these fishes, consumption by both L. ommata and G. 

 affinis is calculated to be 5.88 mg/m /day. Assuming a wet to dry 

 conversion of 6, invertebrate prey production would have to be at least 

 130 kg/ ha/ year (wet weight), just to meet consumption needs of these 

 fish. At a recently abandoned bird rookery on the west side of the 

 Okefenokee, guano fertilization apparently increased standing stocks of 

 several trophic levels, including fish (Oliver and Schoenberg 1989): 

 Average annual biomass estimates of L. ommata and G. affinis were 

 elevated to 4.5 times the levels of the present study. Invertebrate 

 production may have been about 580 kg/ ha/ year, just to meet con- 

 sumption by these fish. At the same site, I measured fish production 

 directly by the size-frequency method (Hynes and Coleman 1968, 

 Freeman and Freeman 1985) and made a second estimate of prey 

 production: Based on a combined production for L. ommata and G. 

 affinis of 89.8 kg/ ha/ year (wet weight, unpublished data) and a gross 

 conversion efficiency of <25% for fish (Brett and Groves 1979), 

 production of invertebrate prey would have to be at least 360 kg/ ha/ year, 

 just to meet consumption requirements of the two fishes. These values 

 are within the range of estimates of production for the total zoobenthos 

 in non-blackwater systems given by Waters (1977), and they are con- 

 sistent with the findings of Freeman and Freeman (1985) that indicated 

 substantial productivity of another Okefenokee blackwater ecosystem. 



ACKNOWLEDGMENTS.— I thank Robert E. Reinert and Steven 

 A. Schoenberg, of the University of Georgia, and Tom Richards for 

 their valuable help and ideas. This research was supported by National 

 Science Foundation grants BSR 81 14823 and BSR 82155587. Paper No. 

 63, Okefenokee Ecosystem Investigations. 



LITERATURE CITED 



Amundsen, P. A., and A. Klemetse-n. 1988. Diet, gastric evacuation rates and 



food consumption in a stunted population of Arctic charr, Salvelinus 



alpinus L., in Takuatn, northern Norway. J. Fish Biol. 33:697-709. 

 Araujo-Lima, C. A. R. M., L. P. S. Portugal, and E. G. Ferreira. 1986. Fish- 



macrophyte relationship in the Anavilhanas Archipelago, a black water 



system in the Central Amazon. J. Fish Biol. 29:1-1 1. 

 Barber, M. C. 1983. Nutrient dynamics of orb weaving spiders (Araneae: 



Araneidae) in Okefenokee shrub swamps. Ph.D. dissertation, Univ. of 



Georgia, Athens. 

 Basimi, R. A., and D. J. Grove. 1985. Estimates of daily food intake by an 



inshore population of Pleuronectes platessa L. off eastern Anglesey, North 



Wales. J. Fish Biol. 27:505-520. 

 Brett, J. R., and T. D. Groves. 1979. Physiological energetics. Pages 279-352 in 



