FISHERY BULLETIN; VOL. 78, NO. 3 



gorbuscha, to short-term, high concentrations of 

 NH3; 2) to determine the size of emergent fry after 

 long-term exposure of alevins to low concentra- 

 tions of NH3; and 3) to determine whether early 

 emergence of immature salmon fry can be caused 

 by short-term sublethal concentrations of NH3. 

 The short-term tests with high concentrations of 

 NH3 identified the more sensitive life stages and 

 provided information on concentrations that were 

 lethal. The sublethal tests identified NH3 concen- 

 trations that caused decreases in the size of emer- 

 gent fry or caused early emergence of immature 

 fry. Identification of factors that cause smaller fry 

 at emergence is important because smaller fry are 

 less capable of surviving in the environment. 

 Laboratory and field studies by Bams (1967) and 

 Parker (1971) have shown that smaller salmon fry 

 have less swimming endurance and are selectively 

 preyed upon by larger predators. 



Our ultimate objective was to compare the con- 

 centrations of NH3 that are harmful to pink salm- 

 on in the laboratory with concentrations of NH3 

 that are harmful in hatchery incubators (Bailey et 

 al. 1980) and in natural spawning redds (Rice and 

 Bailey 1980). To compare the studies of Bailey et 

 al. and Rice and Bailey with our study, our tests 

 were conducted with pink salmon eggs, alevins, 

 and fry exposed to NHg at temperatures <4.8° C 

 and pH's <6.5 — conditions that are typical for 

 freshwater streams in boggy rain forests of the 

 colder northern latitudes. 



MATERIALS AND METHODS 



The pink salmon eggs were fertilized in Sep- 

 tember at Lovers Cove Creek, southern Baranof 

 Island, southeastern Alaska, and incubated to the 

 eyed stage in Heath^ incubators at Auke Bay, near 

 Juneau, Alaska. Some eyed eggs were taken from 

 the Heath incubators and placed in upwelling in- 

 cubator cups or in 15.2 cm diameter pipe in- 

 cubators (Rice and Moles'*) for long-term expo- 

 sures or emergence stimulation tests. The rest of 

 the eggs were left in the Heath incubators for 

 short-term bioassays. 



We measured concentrations of total ammonia 



(NH3 -I- NH4 ^ ) by an automated method that mea- 

 sured the intensity of indophenol blue formed 

 after the reaction of ammonia with alkaline phenol 

 hypochlorite (U.S. Environmental Protection 

 Agency 1974). Total ammonia concentrations 

 were analyzed the same day water samples were 

 taken. The concentrations reported in this study 

 are for the toxic, un-ionized NH3. Total ammonia 

 was measured and the concentration of NHg de- 

 termined by using the temperature-pH correction 

 tables of Emerson et al. (1975). 



Our experimental approach involved three 

 types of experiments: 1) to determine the sensitiv- 

 ity (survival) of each early life stage to NH3, we 

 exposed eyed eggs, alevins, and fry to short-term, 

 high concentrations of NH3 ( >50ppb);2) to deter- 

 mine the effect of long-term exposures of NH3 on 

 size of fry at emergence (end of yolk absorption), 

 we exposed alevins at different stages of develop- 

 ment to low concentrations of NH3 ( <3 ppb) for up 

 to 61 d; and 3) to determine whether NH3 would 

 cause emergence of immature fry, we exposed ale- 

 vins to high concentrations of NH3 (30-150 ppb) 

 for 24 h and counted voluntary out-migrants from 

 the incubators. 



The senstivities of different life stages to short- 

 term, high concentrations of NH3 were tested with 

 96-h bioassays conducted according to the stan- 

 dard procedures of Doudoroff et al. (1951). Eggs, 

 alevins, and fry were exposed to static solutions of 

 ammonium sulfate in freshwater at pH of 6.3-6.5 

 and 3.7°-4.8° C. Twenty-five animals were placed 

 in each 18 1 test container; resulting ratios of tis- 

 sue to test solution were <0.3 g/1. The test solu- 

 tions were aerated and the tests were conducted in 

 the dark. Median tolerance limits (TLm's) and as- 

 sociated 95% confidence levels were calculated by 

 a computerized probit analysis program based on 

 the method discussed by Finney (1971). 



To test the effect of long-term exposures to NHg 

 on size of fry at emergence, ammonium sulfate 

 was introduced into the water which flowed 

 through incubator cups containing the developing 

 alevins. Twenty-five eyed eggs were placed in each 

 upwelling incubator cup (Bailey^), and exposures 

 to NH3 began at selected times after hatching. The 

 NH3 was introduced by dripping small quantities 

 of concentrated ammonium sulfate solutions into 



^Reference to trade names does not imply endorsement by the 

 National Marine Fisheries Service, NOAA. 



"Rice, S. D., and D. A. Moles. 1977. Apparatus for incuba- 

 ting salmonid eggs and alevins in a variety of controlled envi- 

 ronments for laboratory studies. Unpubl. manuscr. Northwest 

 and Alaska Fisheries Center Auke Bay Laboratory, NMFS, 

 NOAA, Auke Bay, AK 99821. 



^Bailey, J. E. 1964. Incubation of pink salmon eggs in a 

 simulated intertidal environment. In Proceedings 15th An- 

 nual Northwest Fish Culture Conference, p. 79-89. Oregon Agri- 

 cultural Experiment Station, Corvallis, OR 97330. 



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