nitrite in a receiving water so that it may be significant to the stream 

 biota. Water reuse systems in some fish hatcheries also employ the nitri- 

 fication process to reduce ammonia concentrations. Where these systems 

 are used, hatchery fish may also be subjected to increased nitrite 

 levels. It has been shown (Smith and Russo, 19/5) that nitrite induces 

 methemoglobinemia in rainbow trout. This results in a reduction in the 

 oxygen-carrying capacity of the blood, and fish may die from anoxia. 



Toxicity of Nitrite to Fishes 



The amount of published information on nitrite toxicity to fishes is 

 small, and most available data are from static tests of short duration; 

 many for 48 hours or less. 



Of 13 fish species tested by McCoy (19/2), logperch [Pcncina captiodte) 

 was the most sensitive, dying in less than 3 hours at 5 mg/liter NO2-N; 

 the common white sucker {Catoi>tomuJ> comm&uovil) was the least sensitive, 

 surviving 48 hours at 100 mg/liter. A 96-hour LC50 of 1.5 mg/liter N02-N 

 was reported for mosquitofish [Gambusia a^lwU) (Wallen, oX at., 1957), 

 and 10 mg/liter NO2-N was reported to be fatal to minnows {Phoxlnu* lazviA, 

 kgtu) in 14 days (Klingler, 1957). Channel catfish {IctaluAuA punctata*) 

 we^e studied by Konikoff (19/5) and Colt (19/4), who reported 96-hour LC50 

 values of 7.5 and 12 mg/liter NO2-N, respectively. 



The LC50 values for 96 hours for rainbow trout [Salmo gaiAdwixl) ranged 

 from 0.? to 0.4 mg/liter NO2-N, with an asymptotic LC50 of 0.14-0.15 (Russo 

 nt al., 19/4). The susceptibility of cutthroat trout {Salmo clcuikl) to 

 nitrite appears to be comparable to that of rainbow trout. Observed 

 96-hour LC 50 values for cutthroat trout were 0.5-0.7 mg/liter NO2-N, with 

 asymptotic LC50 valus of approximately 0.4 (Russo and Thurston, 1975). 

 Chinook salmon {Oncofihijnchui t&hawytAcha) exhibited 40 percent mortality 

 in ?A hours at 0.50 mg/liter N0 2 -N"(Smith and Williams, 19/4), and 96-hour 

 LCcq values for chinook salmon were reported to be 0.88 mg/liter NO2-N 

 (West in, 19/4). 



There are differences in the reported susceptibilities of fishes to 

 nitrite. There does appear to be some genuine variability among fish 

 species, and there may be differences depending on fish size. It should 

 be pointed out that in some cases differences may be due to variations in 

 test water conditions. Recent work (Russo and Thurston, unpublished data) 

 has shown a wide variation in lethal concentrations of nitrite in waters 

 of different pH and salinity. 



REFERENCES 



Ball, I.R. 1967. The relative susceptibilities of some species of fresh- 

 water fish to poisons - 1. Ammonia. Water Res. 1_: 767-775. 



Brown, V.M. 1968. The calculation of the acute toxicity of mixtures of 

 poisons to Rainbow Trout. Water Res. 2: /23-/33. 



79 



