New Design and Use of a Fish Metabolism Chamber

A 10-litre rectangular fish metabolism chamber was constructed with acrylic plastic so that it would passively restrain a 250 to 450-g fish. Gill excretion products were separated from anal excretion products by a rubber septum. Urine was collected through a catheter, and respired carbon dioxide (CO₂) was collected in a gas chamber. Channel catfish (Ictalurus punctatus) were given doses of carbon-14 (¹⁴C) radiolabeled carboxymethyltartonate (CMT) and linear alkylbenzene sulfonate (LAS) by either intraperitoneal injection, liquid gavage, or food gavage. Improved techniques were developed for catheterizing fish.

Analysis of ¹⁴C activity in gill chamber water, anal chamber water, urine, and the CO₂ scrubber enabled quantification of the routes and rates of chemical elimination. Essentially, 100 percent of the CMT from the intraperitoneal dose was excreted within 4 days, 85 percent in the urine with the remainder in the anal and gill chamber waters and the CO₂ scrubber. A greater portion of total LAS excretion showed in the anal and gill chambers, with urine still being the most important route of elimination. The rate of chemical elimination was greatest in the urine during the first 48 h.