Carbaryl, Carbofuran, and Methomyl - National Marine Fisheries ...

provide a slight beneficial effect to species abundance and have neutral or uncertain
effects on species productivity, spatial structure, and diversity.
The precise pre-1960 abundance of this species is unknown. However, historic run
estimates for the Yakima River imply that annual species abundance may have exceeded
300,000 returning adults (Busby, Wainwright et al. 1996). MCR steelhead run estimates
between 1982 and 2004 were calculated by subtracting adult counts for Lower Granite
and Priest Rapids Dams from those at Bonneville Dam. The five year average (geometric
mean) return of natural MCR steelhead for 1997 to 2001 was up from previous years’
basin estimates. Returns to the Yakima River, the Deschutes River, and sections of the
John Day River system were substantially higher compared to 1992 to 1997 (Good,
Waples et al. 2005). Yakima River returns are still substantially below interim target
levels of 8,900 (the current five year average is 1,747 fish) and estimated historical return
levels, with the majority of spawning occurring in one tributary, Satus Creek (Berg
2001). The recent five year geometric mean return of the natural-origin component of the
Deschutes River run exceeded interim target levels (Good, Waples et al. 2005). Recent
five year geometric mean annual returns to the John Day River basin are generally below
the corresponding mean returns reported in previous status reviews. However, each
major production area in the John Day system has shown upward trends since the 1999
return year (Good, Waples et al. 2005). The Touchet and Umatilla are below their
interim abundance targets of 900 and 2,300, respectively. The five year average for these
basins is 298 and 1,492 fish, respectively (Good, Waples et al. 2005).
As per the FCRPS (2008), during the most recent 10-year period (for which trends in
abundance could be estimated), trends were positive for approximately half of the
populations and negative for the remainder. On average, when only natural production is
considered, most of the MCR steelhead populations have replaced themselves. The
ICBTRT characterizes the diversity risk to all but one MCR steelhead population as
“low” to “moderate”. The Upper Yakima is rated as having “high” diversity risk because
of introgression with resident O. mykiss and the loss of presmolt migration pathways.
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