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ANNUAL REPORT

TRINITY RIVER BASIN SALMON AND STEELHEAD MONITORING PROJECT

1992-1993 SEASON

CHAPTER III - JOB III

LIFE HISTORY, DISTRIBUTION, RUN SIZE AND ANGLER HARVEST OF STEELHEAD IN THE SOUTH FORK TRINITY RIVER BASIN

by

Larry Hanson and Barry W. Collins

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ABSTRACT

The California Department of Fish and Game's Natural Stocks Assessment Project monitored adult fall-run steelhead (Oncorhynchus mykiss) migration at various weirs. An insufficient number of tags, applied at our immigrant weir, were recovered to allow us to make a valid estimate of steelhead escapement in the South Fork Trinity River basin during the 1992-1993 season.

Based on the results of our creel survey of the sport fishery in the two major areas accessible to the public, we estimated that 934 anglers fished within these areas and harvested 99 adult steelhead during the 1992-1993 season. The angler harvest in the entire South Fork Trinity River basin during the 1992-1993 season could not be reliably estimated due to an insufficient number of tag returns.

Thirty-four steelhead spawning surveys were conducted in 23 tributaries of the South Fork Trinity River and Hayfork Creek. We surveyed 103.1 km of stream, observed 11 adult steelhead, and counted 98 redds. Steelhead were found to spawn mostly in pool tail-crests (48.3%), runs (28.1%), and step-runs (14.6%). The average redd area was 1.65 m2 and the average redd depth was 32.8 cm.

We captured 408 juvenile steelhead emigrating from the upper South Fork Trinity River basin, and 1,455 from the Hayfork Creek basin. Three juvenile chinook were captured emigrating from Hayfork Creek in May, 1993. Peak emigration of Age 0+ (young-of-the-year) steelhead occurred in May and June 1993.

Juvenile steelhead habitat utilization in Eltapom Creek, a tributary to the South Fork Trinity River, varied among age groups. During the fall 1992 survey, 481 juvenile steelhead were captured. Age 0+ steelhead densities were highest in pools and cascades. Age 1+ and 2+ fish densities were highest in cascades and pools. We estimated a standing crop of 1,594 juvenile steelhead in Eltapom Creek for the period.

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JOB OBJECTIVES

1. To determine the size, composition, distribution, and timing of the adult steelhead runs in the South Fork Trinity River basin.

2. To determine the angler harvest of adult steelhead in the South Fork Trinity River basin.

3. To determine the life history patterns of the South Fork Trinity River basin steelhead stocks.

4. To determine the seasonal use made by juvenile steelhead of various habitat types within selected South Fork Trinity River tributaries.

5. To describe relationships between habitat parameter and seasonal juvenile steelhead standing crops.

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INTRODUCTION

The life histories and current status of steelhead (Onchorynchus mykiss) populations within the South Fork Trinity River (SFTR) basin (Figure 1) are of concern because population numbers are believed to have dropped significantly in the last 30 years. However, little data are available regarding juvenile steelhead life-history patterns, adult steelhead run sizes, spawner distributions, sport fishery yields, and harvest rates.

FIGURE 1. Locations of weirs and traps used to capture immigrant adult steelhead, and emigrant adult and juvenile steelhead in the South Fork Trinity River basin during the 1992-1993 season.

A combination of human activities (e.g., road construction, timber harvest), exacerbated by flooding and wildfire, has limited steelhead production in the SFTR basin. Much of the spawning and rearing habitats have been damaged or destroyed through excessive sedimentation and stream aggradation.

Restoration of salmon and steelhead habitat within the basin is a high priority of the Trinity River Basin Fish and Wildlife Task Force, the U.S. Forest Service (USFS), and the California Department of Fish and Game (CDFG). Restoration and management efforts for steelhead stocks in the SFTR basin will be aided by the knowledge gained through studies of their current status, their habitat requirements, and life histories.

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