EXPERIMENTALLY DETERMINED BLOOD AND WATER-FLOW LIMITATIONS FOR UPTAKEOF HYDROPHOBIC COMPOUNDS USING PERFUSED GILLS OF RAINBOW-TROUT (ONCORHYNCHUS-MYKISS) - ALLOMETRIC APPLICATIONS

The influence of water and blood flows on the uptake of a number of hy drophobic compounds was investigated using perfused gills of rainbow t rout. For all compounds studied, the uptake rate constants increased w ith water flow between 0.045 and 0.52 L min(-1) kg(-1), and remained c onstant at higher flow. The uptake rate constants did not change when blood flow decreased from 10 to 4.4 mL min(-1) kg(-1), while they doub led when blood flow increased from 10 to 20 mL min(-1) kg(-1). Both wa ter and blood flows thus influence the uptake of hydrophobic chemicals . Using allometric relations, it can be established that the water flo w will limit the uptake of hydrophobic chemicals for fish weighing mor e than 5 g. The flow of water will not limit uptake in fish < 5 g, irr espective of physiological conditions and oxygen concentration. At low oxygen concentration, which will increase the water flow in large fis h, the uptake of hydrophobic chemicals may increase with a factor of 5 or more. Increasing the blood how may maximally increase the uptake o f hydrophobic chemicals two-fold, in small as well as in large fish.