DIE ekologie van geselekteerde bentiese spesies in boskopdam, transvaal.

Abstract

THE ECOLOGY OF SELECTED BENTHIC SPECIES IN BOSKOPDAM, TRANSVAAL This study was initiated with the purpose to determine the bio- energetic status of the benthos in the ecological food-pyramid of Boskop Darn, Transvaal. These values, quantitative and qua= litative, were used to determine the potential yield of the benthic component in relation to the fish production in Boskop Darn. In order to obtain this result the following had to be done: 1. A pilot survey was done to determine the dominant bentnic species in numbers and their type of distribution in the darn. 2. The Friedinger dredge was used for obtaining bottom samples and the sampling error for the method used was also determined. 3. A continuous study of six months was then done on the ecology of the dominant benthic groups. This study includes the varia= tion of several factors in the biology of these benthic organisms= over the 6 month period of time. These variables are population numbers, dry bodyrnass, energy content, proteien content, lipid content, the egg production and energy utilized for respiration. Physical and chemical analysis of the darnwater included pH, tern= perature, biological oxygen demand, percentage of saturation of the water with oxygen and the nature of the bottom substrate. The methods used for analysis are described in the handbook of the International Biological Programme (I.B.P.) (Golterrnan, 1969). 4. Further information included is an evaluation of the total loss of population biomass due to passive emigration via the irrigation water. 5. The study is concluded by evaluating the results obtained during the survey to determine the bio-energetic position of the main benthic components and its trophic status as far as the fish population is concerned.