Transportation as a means of increasing wild juvenile salmon survival. Recovery issues for threatened and endangered Snake River salmon : Technical report 4

摘要

Smolt transportation on the Snake and Columbia Rivers has been under nearly continuous study for 25 years. Most controversy surrounds transport of spring/summer chinook, so most analyses and discussion are devoted to that species. Sockeye migrate at the same time as spring/summer chinook as do the earliest of the fall chinook. Therefore, action taken of spring/summer chinook will also affect sockeye and fall chinook. Many factors influenced transportation study results including population structure change -- the shift from nearly all wild fish to nearly all hatchery fish; new dams; the number of turbines at Snake River dams alone increased from 3 in 1968 to 24 by 1979; installation of juvenile fish pass facilities; and calamitous natural events such as the 1977 drought. All the above had negative effects on the survival of wild fish in general and on transport test results specifically, except that when smolts were transported from the upper dam their survival was not influenced by new or existing structures downstream from the transport site.