The situation in this large but shallow spring 

 basin is somewhat similar to that of a lake and it 

 has a diurnal change both in temperature and in 

 dissolved gas pressure. During August and Septem- 

 ber, early morning water temperatures were about 

 6°C, and the saturation level was hardly above air 

 pressure (1.012 atm). As the sun rose, water tem- 

 peratures climbed rapidly to 9°C and the dissolved 

 gas level reached 78-80 mm Hg (1.108 atm or higher). 

 Shortly after the sun set, the water cooled and gas 

 levels returned to normal. 



Much of the spring basin is rather shallow and 

 trout of all sizes can be seen. Dead fish have been 

 seen on the basin bottom, but fishermen are the 

 suspected cause because it is a popular place to fish. 

 Trout fry in shallow water were observed to be light 

 colored in the morning and darkened by late after- 

 noon, indicating stress. Some of these fry were 

 "pinheaded" indicating possible fasting. However, 

 human residents report that trout have been seen 

 spawning in this basin each fall (brook trout?) and 

 spring (rainbow trout?). 



The invertebrate fauna was extremely abundant 

 in this apparently very productive stream. Bottom 

 samples contained mayfly nymphs, stonefly 

 nymphs, caddis larvae, midge larvae, limpets, 

 snails, leeches, and oligocheates. Apparently, this 

 potentially lethal supersaturation is not having a 

 devastating effect in its diurnal form. 



Williamson River 



This stream was sampled only once in August 

 and it was slightly hyposaturated at that time. It is 

 famous for its good trout fishing and it has a prodi- 

 gious benthic invertebrate population. 



DISCUSSION 



Supersaturation in the Klamath Basin streams 

 begins with cold rain and melting snow percolating 

 into the ground thus recharging aquifers, but in so 

 doing, the water is geothermally warmed enough to 

 supersaturate most of its dissolved gases. Dissolved 

 oxygen levels were near saturation values which 

 according to Rucker (1974) may diminish the like- 

 lihood of gas bubble disease. Even so, the result of 

 supersaturation has been significant mortality from 

 gas bubble disease in the hatchery (at 105%). Even 

 higher levels of supersaturation (107%) occur con- 

 tinuously below the hatchery in Crooked Creek and 

 still higher levels (110%) occur diurnally in Spring 

 Creek. The impact to the wild fish is still undeter- 

 mined but wild trout are present and feed during 



supersaturation apparently reproducing (judging 

 from the presence of trout fry). Also, freshwater 

 invertebrate populations were well represented with 

 desirable types being present in abundance. 



It is possible that the low saturation levels 

 which killed fish in the hatchery are being aggra- 

 vated by solar heating of their bodies as well as by 

 heating of the water. These waters are crystal clear 

 and since sunshine can be very intense, sunburning 

 of the fish has been a significant problem in previous 

 years. Since it is theoretically possible to raise the 

 gas pressure within the fish by solar heating, sun- 

 shine may convert an otherwise tolerable gas pres- 

 sure into an internally lethal gas pressure. If so, it 

 might account for the fish mortality in the hatchery 

 raceway. 



This leaves the unanswered question as to why 

 the wild fish (and invertebrates) seem to be thriving 

 at higher gas levels than killed their hatchery 

 counterparts. One possibility is that present bioassay 

 methods result in hypersensitivity among the test 

 fish. For example, it seems rather unlikely that a 

 wild fish could expose itself continuously for 10 days 

 to a given uncompensated lethal hyperbaric dis- 

 solved gas level. One can think of other possible 

 factors, but whatever they may be, one sees a sig- 

 nificantly different problem when they compare 

 hatchery and laboratory bioassays to instream 

 conditions. After these phenomena are given further 

 study the results may shed some much needed light 

 both on "background" levels of supersaturation and 

 on how much supersaturation is too much in nature. 



REFERENCES 



Bouck, C. R., D. W. Bridges, J. P. Clugston, P. Culpin, R. Eisler, 

 D. Hansen, ). S. Hughes, H. E. Johnson, D. Narver and N. Rath- 

 burn. 1974. A Survey of Manpower, Funding, and Biological 

 Research in Water Pollution Abatement Among Natural Re- 

 source Agencies of Canada and the United States. Unpublished 

 Report of the Water Quality Committee, American Fisheries 

 Society. 



Egusa, S. 1959. The gas disease of fish due to excess nitrogen. 

 Hiroshima Univ. /. fac. Fish. An. Husb. 2.157-182. 



Harvey, H. H. 1967. Supersaturation of lake water with a pre- 

 caution to hatchery usage. Trans. Am. Fish. Soc. 96.194-201. 



Harvey, H. H. and A. C. Cooper. 1962. Origin and Treatment 

 of a Supersaturated River Water. Intl. Pacific Salmon Fish. 

 Comm. Prog. Rpt. No. 9, 19 pp. 



Lindroth, A. 1957. Abiogenic gas supersaturation of a river 

 water. Archiv. Fur Hydrobiologic. 53.589-597. 



Renfro, W. C. 1963. Gas-bubble mortality of fishes in Calves- 

 ton Bay, Texas. Trans. Am. Fish. Soc. 92.320-322. 



Rucker, R. R. 1974. Cas-bubble Disease of Salmonids: Varia- 

 tion in Oxygen-Nitrogen Ratio with Constant Total Cas Pres- 

 sure. National Marine Fish. Ser. Project Completion Report. 

 12 pp. (Mimeo). 



40 Bouck 



