| Summary: | Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item. Includes bibliographical references. Issued also on microfiche from Lange Micrographics. A commercial diet containing 10% lipid and an experimental diet consisting of the commercial diet with additional menhaden oil to provide 14.5% lipid were fed to separate groups of juvenile (100 g) red drum (Sciaenops ocellatus). After 6 weeks of consuming these diets, subgroups of fish were stocked into 8, 0.04-ha earthen ponds, with or without thermal refuges, during January 1994. The thermal refuges, consisting of air-inflated domes of plastic sheeting covering one end of affected ponds, were designed to afford red drum sub-habitat warmer than other parts of the ponds. Geothermal water (22 OC) from a freshwater well heated the refuges. An opening in each refuge's pond-ward side provided access for the fish. Mean water temperatures inside the refuges were generally 1 'C or greater than open-pond temperatures. Fish were observed entering the refuges. The experiment ended, after a harsh cold-front, and it was observed A commercial diet containing 10% lipid and an experimental diet consisting of the commercial diet with additional menhaden oil to provide 14.5% lipid were fed to separate groups of juvenile (100 g) red drum (Sciaenops ocellatus). After 6 weeks of consuming these diets, subgroups of fish were stocked into 8, 0.04-ha earthen ponds, with or without thermal refuges, during January 1994. The thermal refuges, consisting of air-inflated domes of plastic sheeting covering one end of affected ponds, were designed to afford red drum sub-habitat warmer than other parts of the ponds. Geothermal water (22 OC) from a freshwater well heated the refuges. An opening in each refuge's pond-ward side provided access for the fish. Mean water temperatures inside the refuges were generally 1 'C or greater than open-pond temperatures. Fish were observed entering the refuges. The experiment ended, after a harsh cold-front, and it was observed that all fish in every pond were dead. However, the refuge design utilizing geothermal water was successful in maintaining temperatures in the refuges above those observed in open ponds. Water analysis indicated that chlorides may have been too low for survival of red drum at stressful low temperatures. Another study with juvenile red drum (> 7 g) was conducted in which the same diets were fed for 6 weeks, after which fish were transferred to the following three water treatments prepared from fresh well-water used in the refuge study: unamended well-water; artificial seawater (6 '/. salinity); and well-water + NaCi (6 '/. salinity). Fish in these water treatments were subjected to an acute cold-tolerance assay. The median lethal temperature for fish held in the artificial seawater was significantly (P< 0.05) lower than the other treatments; well-water + NaCi did not increase cold-tolerance over well-water alone. However, fish not challenged with cold had the highest survival in artificial seawater followed by well-water + NaCl, but no survival in unamended well-water alone. These studies suggest that exposure to water inadequate in chlorides and possibly other ions can result in reduced cold tolerance of red drum. Dietary lipid effects on cold tolerance were not significant in either study.
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