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

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Table 7 identifies populations within the CV spring-run Chinook salmon ESU, their<br />

abundances, <strong>and</strong> hatchery input.<br />

Table 7. CV Chinook salmon--preliminary population structure, abundances, <strong>and</strong> hatchery<br />

contributions (Good, Waples et al. 2005).<br />

Population<br />

Historical<br />

Abundance<br />

Most Recent<br />

Spawner<br />

Abundance<br />

Hatchery<br />

Abundance<br />

Contributions<br />

Butte Creek Spring-run Chinook 67-4,513 Unknown<br />

Deer Creek Spring-run Chinook 243-1,076 Unknown<br />

Mill Creek Spring-run Chinook 203-491 Unknown<br />

Total<br />

~700,000 for all<br />

populations<br />

513-6,080 Unknown<br />

Life History<br />

CV Chinook salmon enter the Sacramento River from March to July <strong>and</strong> spawn from late<br />

August through early October, with a peak in September. Spring-run fish in the<br />

Sacramento River exhibit an ocean-type life history, emigrating as fry <strong>and</strong> sub-yearlings.<br />

Chinook salmon require cool freshwater while they mature over the summer. This<br />

species tends to take advantage of high flows. Adult upstream migration may be blocked<br />

by temperatures above 21ºC (McCullough 1999). Temperatures below 21ºC can stress<br />

fish by increasing their susceptibility to disease (Berman 1990) <strong>and</strong> elevating their<br />

metabolism (Brett 1979).<br />

Status <strong>and</strong> Trends<br />

CV Chinook salmon were listed as threatened on September 16, 1999 (64 FR 50393).<br />

This classification was retained following a status review on June 28, 2005 (70 FR<br />

37160). The species was listed because dams isolated individuals from most of their<br />

historic spawning habitat <strong>and</strong> the remaining habitat is degraded. Historically, spring-run<br />

Chinook salmon were predominant throughout the CV. This species occupied the upper<br />

<strong>and</strong> middle reaches (1,000 to 6,000 ft) of the San Joaquin, American, Yuba, Feather,<br />

Sacramento, McCloud <strong>and</strong> Pit Rivers. Smaller populations occurred in most tributaries<br />

with sufficient habitat for over-summering adults (Stone 1874; Rutter 1904; Clarke<br />

1929).<br />

67

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