Wednesday, March 14, 2012

Past Abundance of Wild Summer Steelhead in the North Umpqua Basin

13,000+ Wild Fish on an El Nino Year?
Past Abundance of Wild Summer Steelhead
in the North Umpqua Basin

This is an assessment of The Umpqua River Study, a joint report by the Fish Commission of Oregon and The Oregon State Game Commission in 1946.  These two agencies later became The Oregon Department of Fish and Wildlife (ODFW).  This means that it is part of the historical record for past Pacific salmon numbers in this basin.
This study is of interest as the earliest historical documentation of fish counts over Winchester Dam and is apparently used as such by the North Umpqua Basin ODFW office.  This report contains data about run sizes for wild summer steelhead and other Pacific salmon in the North Umpqua River for 1946 and about past abundance.  All page citations herein refer to The Umpqua River Study.
First of all, The Umpqua River Study defines the summer steelhead as those fish crossing Winchester Dam from June through October (p. 41).  Presently and for some time now, the ODFW has defined as summer steelhead those steelhead crossing the dam between May 1 and November 30.  I have corrected the data from their Table 3 for this discrepancy  The number of wild summer steelhead documented as they passed the dam in 1946 becomes 4,137 fish.
The Umpqua River Study states (p. 43) that 1,244 steelhead were taken during the coho net fishery below the dam from October 1 through November 15, 1946.  Sixty-six of these fish were from the Smith River, leaving 1,178 North Umpqua River fish.  The timing indicates that these fish were undoubtedly summer steelhead.  The study further states that 97 summer steelhead were taken below the dam during the shad net fishery May and June of 1946.[1]  When the summer steelhead taken during the coho and shad fisheries are added to the corrected number of wild summer steelhead counted as they crossed Winchester Dam, the size of the 1946 run of summer steelhead becomes 5,412 wild fish.  This is 2,051 more fish than are presently listed as running in 1946—3,361 fish—by the ODFW.
Past abundance.  “The only summer steelhead caught by the commercial fishery are those few taken incidentally in the shad nets.” (p. 45).  In 1926, 18,000 pounds of summer steelhead were landed during the shad net fishery in May and June (p. 43).  When the average size of the summer steelhead landed in the 1946 shad fishery, 6.8 pounds, is used, this 18,000 pounds becomes 2,647 fish.  During 1946, May and June summer steelhead—including the 97 fish caught in the shad nets during 1946—make up 24% of the 5,412 summer steelhead that ran in that year.  Dividing the extrapolated 2,647 summer steelhead caught in shad nets during 1926 by 24% (0.24) yields a minimum of 11,029 wild summer steelhead running in 1926. 
The run size in 1926 is a minimum number because certainly some summer steelhead made it past the shad nets during May and June of 1926.  If even 20% of the summer steelhead running in May and June made it past these nets, the run size could have been over wild summer steelhead for that year.
Other factors had a negative influence on the size of the wild summer steelhead run in the North Umpqua River in 1926.  Commercial fishing was in full swing on the lower Umpqua.  “From 1916 to 1923 the fishing intensity gradually increased.  Then, in 1924, sixteen additional gillnet boats were brought from the Colombia to the Umpqua River.  This, coupled with the success of the previous season’s fishery, raised the fishing intensity to an all time high in 1924.” (p.23).  Even twenty years later in 1946, commercial fishing in the Umpqua River supported fifty fishermen and their families as well as four processing plants (p. 6).
Another factor influencing the numbers of summer steelhead returning to the North Umpqua River was the presence in the river—in the neighborhood of Rock Creek—of weirs stretched bank to bank from the spring until sometime in September.  These blockages to migration were for the purpose of taking eggs from Pacific salmon.  This had occurred since at least 1900 and continued in some fashion through 1946 (p. 11).  “From 1939 to 1946, inclusive, a total of slightly over 3,000,000 [eggs] were taken.” (p.11).
The final factor influencing fish abundance in 1926 is that 1926 is well recognized now in the literature as a severe El Nino year, that is, a year of exceptionally poor ocean conditions.  El Nino/Southern Oscillation (ENSO) events occur every two to seven years and last from six to eighteen months and, while primarily a tropical event, it affects regions of the world far removed from the tropics with anomalous weather.  The main influence of these events on Pacific salmon numbers is probably through their interruption of southerly near-shore winds of spring and summer that bring about the coastal upwellings of cold nutrient-rich water, fueling the rich ocean ecosystems along the coasts of Oregon and Washington and increasing productively by more than 100%.  The adult abundance of various Pacific salmon species is correlated with the strength of these seasonal upwelling events.
So, in the face of decades of permanent egg weirs, of an intensive commercial net fishery, and—additionally and exceptionally—in the face of a very poor ocean conditions, a minimum number of 11,029 wild summer steelhead returned to the North Umpqua Basin.  In the fifty-seven years (only until 2002[2]*) since counting began at Winchester dam, the average return of wild summer steelhead to the basin has been 3,461 fish [1,951 fish less than what The Umpqua River Study documents ran in 1946—5,412 fish—and approximately a third of the fish that ran in the severe El Nino year of 1926.].  And consider, if in an El Nino year eighty years ago, the minimum number of wild summer steelhead was 11,029 fish, what was the wild summer steelhead run on the years when ocean conditions were average or good?
The historical number documented in their official file of Winchester Dam counts for 1946 by the ODFW is 3,361 wild summer steelhead.  This is approximately the number that would be obtained from Table 3 in The Umpqua River Study by ignoring the summer steelhead taken in the shad and coho nets and not counting those fish that ran in May and November as summer steelhead.  Why is this number of 3,361 wild summer steelhead being used by the local ODFW today?
How did the Fish Commission of Oregon and the Oregon State Game Commission assess the 5,412 wild summer steelhead that ran in 1946?  They don’t say directly, but indirectly they do.  The sport fishery that year was considered “particularly unsuccessful” (p. 46).  Their single recommendation bearing specifically on steelhead populations (p. 44) was to close the North Umpqua and its tributaries above Rock Creek to all fishing between October 31 and the opening of the trout season the following spring.  Together these observations suggest that the authors of The Umpqua River Study were not impressed with the 5,412 wild summer steelhead assessed for 1946.
In their summary, the authors of The Umpqua River Study actually state that “Under a proper management program, an average sustained yield of several times the 1946 catches [sic] may be expected.” (p. II).
And, please bear in mind, the permanent egg weirs and commercial in-river net fisheries have by now been gone for more than half a century and the absence of these two wild fish killers more than offset any subsequent deterioration of the habitats used by the various life stages of wild summer steelhead.[3] 
So where are the fish?  Has the ODFW reasonably and responsibly managed our  management of our wild summer steelhead populations? 
Take care, go well,
Lee Spencer




[1] With reference to the incidental catch of summer steelhead in shad nets, Chris Frissell notes that an uncertain percentage of these steelhead may be ocean-bound fish that have survived the spawning process (personal communication 2007).
[2] The seasonal percentage wild fish versus hatchery fish reported as passing Winchester Dam ceased to be believable around 2003.
[3] You would do well to consider that there has been a hatchery program for summer steelhead in place for more than fifty years now.

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