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Ecology and salmon related articles

Chinook Salmon Laid More Eggs in 2002

by Idaho Fish & Game News
Wood River Journal, February 19, 2003

Should Translated Into Bigger Numbers

Idaho chinook laid more eggs in native streams last year even though fewer adult fish were counted at Lower Granite Dam than in 2001.

If Mother Nature helps make rivers and ocean conditions salmon-friendly, Idahoans should see good fish runs again in a few years as a result of the 2002 spawning success.

Fish and Game biologists have been reviewing their index 2002 redd (salmon nests) counts and are seeing what they expected -- a slight increase over the number of redds counted in 2001. This may seem odd because the total number of adult spring and summer chinook counted at Lower Granite Dam in 2001 was 185,700, whereas only 97,200 adults were counted in 2002. How then to explain more redds?

The answer lies in looking at the components of the run. Most of Idaho's hatchery stocks return primarily as two-ocean (four-year old) adults. However, many of the state's wild spring and summer chinook stocks have an equal or larger number of adults that return as three-ocean (five-year-old) adults.

Thus, for smolts that went to the ocean in 1999, those from a hatchery mostly returned in 2001, but as many or more smolts that were wild returned as adults in 2002.

Idaho fishery biologists count the same "index" populations of spring and summer chinook in the same places each year to give them a reliable gauge of trends in Idaho's salmon. Today's index redd count program started in 1957, when all of the index populations are influenced by hatchery fish. However, many remain unaffected by hatcheries, such as in the Middle Fork of the Salmon River wilderness.

In 2002, biologists counted 3,542 redds in Salmon River drainage index areas. That compares to 3,345 redds counted in 2001, for an increase of 6 percent. Looking back at recent history shows that there has been a substantial increase in chinook spawning compared to 1997, the spawn year for the "parents" of many of the adults spawning in 2002. The 1997 redd count was 1,169.

A comparison of the 1997 redd count to the 2002 count shows a 203 percent increase, attributed to better freshwater migration conditions for smolts and a more productive ocean. Smolts from the 2002 redds will migrate to the ocean in 2004, and will return to Idaho from 2004 through 2007.

A longer look back in time reveals that in 1962, the total redd count was 7,287 from the same group of populations that was counted in 2002. So, although the increase redd count in 2002 will help Idaho's spring and summer chinoook, the 2002 redd count declined 51 percent from just 40 years ago.

What does the future hold? The 2003 adult run return forecast is lower than for the 2001-2002 returns, but biologists will not know the real number until the fish show up. What we can already count on is that come late August and September, no matter what, Idaho fishery biologists will be out counting salmon redds as they have for the last 46 years.

Idaho Fish & Game News
Chinook Salmon Laid More Eggs in 2002
Wood River Journal, February 19, 2003

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