Electrical Power for Valdez and the Copper River Basin-1981

emergence and outmigration of fry to Port Valdez at a time when itis questionable that there would be adequate planktonic productionto sustain rearing activity. Consequently, a substantial alterationin natural water temperature during the egg to fry developmentperiod would negatively impact run strength.With sufficient data, the number of temperature units required foreggs to hatch under natural stream temperatures can be calculatedand compared to the number of temperature units anticipated to existunder altered stream conditions. The difference in temperatureunits will show if early or late emergence will occur, and if so,give the approximate magnitude of change in the time of emergence.Where intertidal spawning occurs, such as in Allison Creek, thewarmer saltwater contributes to higher intragravel temperatures.This adds to the complexity of the temperature regime in intertidalareas because intertidal zone temperatures are influenced by (1)upstream water temperatures, (2) saltwater temperatures exposed tostream gravel, (3) time of exposure to saltwater, and possibly (4)the permeability of gravels.Should early fry emergence occur, sufficient food sources may notexist. Figure 4 illustrates the seasonal variation in populationdensity of the copepod, Harpacticus uniremis, an organism whichcould be an important food source for post-emergent fry. Healey(1979) found that H. uniremis made up 50% of the overall diet ofjuvenile chum salm~n in the Nanaimo Estuary and greater than 80%of the diet when fry were most abundant. He also found thatthe seasonal pattern of abundance of fry and H. uniremis in theestuary was the same, and that fry consumed most of the estimatedproduction of H. uniremis. Large numbers of this copepod are usuallynot present in Port Valdez until mid-March to early April. Undernatural conditions pink and chum salmon fry emergence begins inmid-April in the Port Valdez area.Radical fluctuations in stream flow contribute most heavily tomortality of developing eggs through erosion, shifting of gravel, ordewatering of spawning beds. Flooding also causes mortality bydeposition of silt on spawning areas, which slows intragravel watermovement, decreasing the oxygen supply to the eggs, and preventingremoval of waste products. Other factors contributing to mortalityof eggs are freezing, exposure to light, parasites, predation, highsalinity, shock, and superimposition of redds (spawning beds).The tailrace discharge could cause increased velocity in the streamand scouring of the streambed with subsequent removal or burial ofspawning gravel. Alterations in natural streamflow could also haveadverse impacts upon spawning adults as a result of either high orlow flows which are not optimum for spawning. Post-project flowschedules could be beneficial to fish resources by reducing radicalflow fluctuations and providing flows optimum for life stage requirementsof pink and chum salmon.