produced in intertidal areas than in upstream 

 areas (Kirkwood, 1962). From field observation 

 alone, it is apparent that pink and chum salmon 

 eggs and larvae can tolerate intermittent high 

 salinity. 



Rockwell (1956) exposed pink and chum salmon 

 eggs and larvae to constant high salinity and found 

 no evidence that fertilization of eggs was affected 

 by salinities up to 18% . The tolerance of 

 embryos to sea water was a function of osmotic 

 pressure, time of exposure, and stage of develop- 

 ment. Mortality was attributed to dehydration. 

 He found a marked reduction in the rate of early 

 growth of chum salmon embryos at constant 

 salinities of 12%o and greater and a total mortal- 

 ity to hatching at a salinity of 12%o. At 6% 

 salinity, survival to hatching was less than thai 

 in the controls. 



Larvae are more tolerant of high salinity than 

 eggs. According to Rockwell (1956), salinities as 

 high as 18% o killed few pink salmon larvae. 

 Chum salmon larvae were less tolerant, some dying 

 at a salinity of 12°/oo- 



Salinity of intragravel water in pink and chum 

 salmon intertidal spawning beds is influenced 

 markedly by tidal action. Hanavan and Skud 

 (1954) found salinity of intragravel water of pink 

 salmon spawning beds corresponds closely to 

 salinity of overlying water. Also, they observed 

 high survival of pink salmon eggs and larvae where 

 tidal inundation prevailed during 35 percent of the 

 incubation period. Ahnell (1961) observed that 

 the salinity of intragravel water remained high 

 for a period after the tide had receded and after 

 fresh water had flowed over the streambed. He 

 found also that high salinity of intragravel water 

 was frequently associated witli low dissolved 

 oxygen concentration. 



The effect of salinity on pink and chum salmon 

 fry production is still poorly understood, although 

 highly productive spawning areas exist in inter- 

 tidal zones of streams (Kirkwood, 1962). Eggs 

 and larvae of both species can tolerate intermit- 

 tent high salinity, but tolerance levels have not 

 yei been defined. Also, the retention of sail water 

 by spawning beds and the influence of salt water 

 on temperature, oxygen levels, and water velocity 

 have not been studied in detail. The ultimate 



need is to determine the relative potential of 

 intertidal and upstream areas to produce fry. 



500 



PERMEABILITY OF BOTTOM MATERIALS 



It has already been pointed out that the oxygen 

 delivery rate to an egg or larva is a function of 

 both the oxygen content and velocity of intra- 

 gravel water. Apparent velocity of water flow- 

 ing within the streambed can be described by the 

 equation. 



v= v i (2) 



Where v= apparent velocity, 



jj = permeability coefficient, and 

 i= hydraulic gradient. 



According to tins equation, apparent velocity 

 of intragravel water varies directly with the perme- 

 ability of materials through which it passes. 

 Other factors being equal, the permeability of 

 bottom materials in spawning beds should be 

 directly related to their potential to produce 

 salmon fry; Wickett (1958) gave evidence that 

 the average survival of pink and chum salmon eggs 

 and larvae in four British Columbia streams was 

 directly related to the permeability of bottom 

 materials (fig. 3). 



The permeability of bottom materials is a 

 function of particle compaction, arrangement, 

 and size. McNeil and Ahnell (1964) showed that 

 the permeability of bottom materials in a pink 

 salmon spawning bed is inversely related to the 

 fraction of fine particles composing the total 

 volume of the bed. Thus, the resistance to flow 

 caused by the presence of fine particles in salmon 

 spawning beds must govern, to a large extent, 

 their potential to produce healthy fry. 



40 80 120 160 



PERMEABILITY OF STREAMBED GRAVELS ICM./MIN.) 



Figi re 3.— Observed relation reported by Wickett (1958 

 between permeability and survival of pink and chum 

 salmon to migrant fry. 



U.S. FISH AND WILDLIFE SERVICE 



