Submerged cage culture of fish in supersaturated thermal effluent. 8 Annual Meeting of World Mariculture Society. San Jose (Costa Rica) Jan. 9, 1977.
A primary drawback for cage culture in heated effluent has been extensive mortalities due to gas bubble disease. This malady, endemic to power plant effluent, is caused by supersaturation of atmospheric gases in water. The objective of this research was to determine the effect of hydrostatic pressure as a possible remedy for gas bubble disease in the discharge canal of a Galveston Bay, Texas, steam-electric plant. Seven estuarine fishes, pinfish (Lagodon rhomboides), spot (Leiostomus xanthurus), Atlantic croaker (Micropogon undulatus), black drum (Pogonias cromis), red drum (Sciaenops ocellata), Atlantic spade-fish (Chaetodipterus faber), and striped mullet (Mugil cephalus), were caged at the surface and bottom of the 3 m-deep discharge canal where total gas saturation frequently exceeded 120% during winter months. Survival in surface cages averaged 1% after 2 weeks, while survival in bottom cages averaged 81% after 12 weeks. No supplemental food was allotted, but an abundance of small organisms was continually sluiced down the discharge canal through the cages. Winter growth rates generally surpassed those of comparable species cultured elsewhere in the cooling water system at ambient temperature and fed a prepared ration. As discharge water temperature approached 35 degrees C, growth rates declined. Other factors affecting growth were cage mesh size, species type, and size of individuals. All fish were maintained in the heated effluent until thermal death to determine the upper lethal temperature limits. These results indicate that submerged cage culture in power plant effluent might offer a significant savings to the culturist by increasing winter growth rates without the expense of feeding.