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vent of predatory fish into the Pacific Northwest, has this had more 

 of an effect on the populations than in other areas? 



Dr. Tillman. It is a factor in some of these rivers which have 

 dams on them. It is clear predators are feeding on the downstream 

 migrants of salmon and steelhead trout, but that is only one of the 

 factors. I wouldn't exactly consider it a major factor. These other 

 factors, the four H's, as we call them, are the primary problem 

 areas. 



Mr. Calvert. And you believe that those are the significant 

 problems that have more importance than the drought and of the 

 predatory fish, and even the advent of the species, especially mam- 

 mal marine species, whose populations have managed to increase 

 dramatically over the last several years? 



Dr. Tillman. Right. Looking at all of these river systems, over 

 the long haul, the long-term, the major factors are those four, the 

 hatcheries, the habitat degradation, the hydropower developments, 

 and so on. 



The drought is an act of God, if you will, that has come along 

 and exacerbated the effects of these other factors. It is not the 

 major effect. It has had an impact, yes, but over the long trend of 

 these stocks, it is these other factors which have been the most im- 

 portant ones. 



Mr. Calvert. Do you think it would be helpful — you mentioned 

 apparently there has not been any study to look at the drop of pop- 

 ulations, of the salmon population, if there is any way to do this 

 over recent history — I know you couldn't in the past — to look at the 

 drop of population of salmon after a period of drought to see what 

 the percentage drop in populations would be? 



Dr. Tillman. I am sure there is information available on that, 

 on what recoveries were experienced after drought periods. I have 

 not reviewed that myself 



Mr, ladanza is with me. Perhaps he knows something about that. 



Mr. Vento. Would you give your name for the record, please? 



Mr. Iadanza. Yes, my name is Nicholas ladanza, Chief of the 

 Habitat Conservation Branch out of Portland. I can take a stab at 

 your question. 



There have been some pretty significant drought occurrences in 

 the Pacific Northwest over the past couple of years. 1972 was a 

 pretty bad year as was 1977. We did see some drop in population 

 then. But since you have multiple year classes of fish, there is usu- 

 ally some compensating mechanism there. And there have been 

 fluctuations up and down. But I think in general, over the past 30 

 years, there has been a declining trend regardless of the fact 

 whether there have been drought years and then good water years. 



There are compensatory mechanisms that occur at times of 

 drought. Sometimes you have fewer fish coming down, making it 

 down the river because of drought; you have the rearing habitat 

 which has been limited; the spawning habitat has been limited, but 

 there is potential for more juveniles to survive when they come to 

 the estuary. 



So I think the basic response to your comment is the fact that 

 even though there have been droughts and there are fluctuations 

 in populations, the historic trend is showing there is a downward 

 trend in salmon populations. 



