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ANNUAL REPORT

TRINITY RIVER BASIN SALMON AND STEELHEAD MONITORING PROJECT

1991-1992 SEASON

CHAPTER III - JOB III

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

by

Carrie E. Wilson 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 and winter-run steelhead (Oncorhynchus mykiss) migration at various weirs and estimated an escapement of 3,741 steelhead into the South Fork Trinity River basin during the 1991-1992 season.

Based on the results of our creel survey in the two major areas accessible to the public, we estimated that 1,580 anglers fished within these areas and landed 224 adult fall-run and winter-run steelhead, two half-pounders, two juvenile steelhead, and five fall-run chinook salmon during the 1991-1992 season. The angler harvest rate during the 1991-1992 season, in the entire South Fork Trinity River basin, was estimated from mail-returns of reward tags from adult fall-run and winter-run steelhead. The sport harvest rate was estimated to be 20.2% (756 fish).

Adult steelhead spawning stock surveys were conducted on 26 streams that are tributaries to the South Fork Trinity River and to Hayfork Creek. We surveyed 134.4 km of stream, observed nine adult steelhead, and counted 262 redds.

The characteristics of steelhead spawning habitat within the South Fork Trinity River basin were evaluated by measuring various physical and hydraulic parameters of steelhead redds. Steelhead were found to spawn mostly in step-runs (42.8%) and pools (36.7%). The average redd area was 1.24 m2 and the average redd depth was 23.1 cm. The average fish-nose water velocity and average mean water column velocity where redds were observed were 0.39 and 0.42 m/sec, respectively.

We captured 1,896 juvenile steelhead emigrating from the upper South Fork Trinity River basin and 7,127 from the Hayfork Creek basin. Peak emigration of Age 0+ steelhead occurred during May and June 1992, while peak emigration of Age 0+ (young-of-the-year) chinook salmon occurred during May 1992.

Juvenile steelhead habitat utilization in Eltapom Creek, a tributary to the South Fork Trinity River, varied among age groups. During the fall 1991 survey, Age 0+ steelhead densities were highest in riffles and cascades, while in spring 1992 densities were the lowest in these two habitat types. Age 1+ fish densities in the fall were highest in cascades and pools; in spring their densities were about equal in all habitats except runs, where densities were about 1/2 that in other habitats.

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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 of steelhead (Oncorhynchus 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, sportfishery yields, and harvest rates. As a result of poor habitat management within the SFTR basin, the 1964 flood severely impacted the area, damaging or destroying spawning and rearing habitats through excessive sedimentation. A combination of human activities (i.e., road construction, timber harvest, and recreation) exacerbated by natural events (i.e., wildfire and flooding) continue to curtail steelhead production within the basin by degrading in-stream habitat quality. 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 [Shasta-Trinity National Forest]), and the California Department of Fish and Game (CDFG). These restoration efforts will be guided by the knowledge gained through this study of the current status of steelhead stocks, their habitat requirements, and their life histories.

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 1991-1992 season.

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METHODS

Use of Standard Julian Week

Weekly sampling data collected by Project personnel at the weirs are presented in Julian week (JW) format. Each JW is defined as one of a consecutive set of 52 seven-day (weekly) periods,

beginning 1 January, regardless of the day of the week on which 1 January falls. The extra day in leap years is included in the 9th week, and the last day of the year is included in the 52nd week (Appendix 1). This procedure allows annual comparisons of identical weekly periods.

Adult Steelhead Run Timing

To assess the timing of the adult steelhead run into the SFTR basin, we trapped immigrant adult steelhead at the Sandy Bar Weir within the SFTR basin. The Sandy Bar Weir was located on the SFTR at river km (RKM) 2.4, and operated from 5 September 1991 through 11 February 1992. The weir consisted of a series of panels, measuring 1.2 m high and 1.5 m wide constructed of 1.9-cm EMT (electrical metallic tubing) conduit with 3.2 cm horizontal bar spacing welded to angle iron frames. The panels were wired end to end and supported with metal fence posts. A trap (2.4 m wide x 2.4 m long x 1.2 m high), with sides constructed from the same weir panels, and flooring and top from marine plywood, was placed in the river thalweg with its fyke entrance facing downstream. The weir panels were tied in with the trap and extended outward across the river guiding upstream migrating fish into the trap. Small mesh netting was strung above the weir to prevent fish from jumping over.

Each steelhead captured was examined for: 1) fin clips, 2) tags, 3) gill net scars (nicks in the leading edges of dorsal and pectoral fins, sometimes combined with vertical white scars on the head), 4) hook scars (of ocean origin when healed, of freshwater origin when not healed), 5) predator scars (inverted 'V'-shaped marks, usually on the underbody), and 6) other scars of unknown origin. Steelhead were measured to the nearest cm fork length (FL), and their sex recorded. A scale sample was removed from the left side of each weir-caught fish, in an area slightly posterior to the anterior insertion of the dorsal fin, just above the lateral line. Each scale sample was placed between waterproof paper within a coin envelope and labeled with collection date, collection site, method of collection, sex, and FL (cm) of the fish.

All adult steelhead in good condition were marked with a 1/2 left ventral (LV) fin clip and a discretely numbered $10-reward anchor tag. To avoid excessive tagging mortality, we did not tag fish which were severely stressed by the weir capture and handling process, or those which appeared in generally poor physical condition. Tag recoveries were later used to estimate harvest rates and population abundance. Angler harvest rates were estimated from reward tag returns. The tags and clips were applied with the intention of computing a Petersen population estimate (Ricker 1975) based on the ratio of tagged to untagged fish observed in later recovery efforts (creel census and weirs for emigrant fish).

Creel Survey

Angler effort and harvest information for fall- and winter-run steelhead within two areas of the SFTR basin was determined from a systematic stratified creel survey, conducted from 1 November 1991 through 14 March 1992. The creel survey was conducted in two subsections of the lower SFTR basin (Figure 2). The lower survey area extended from the confluence of the SFTR with the main-stem Trinity River upstream for a distance of 22.5 km. The upper, Hyampom, area extended through the Hyampom Valley from RKM 33.0 to RKM 50.7. These two creel survey areas cover the river reaches fished by the majority of anglers, as public access is limited outside of these two areas due to the lack of public roads. Angler access sites in each creel survey area were identified prior to the survey period. The creel survey was further stratified by JW (Appendix 1), day (weekend/weekday), and time periods (am/pm: dawn to noon and noon to dusk, respectively). We extrapolated data for each stratum that was not surveyed by using average values for strata from equivalent sampling periods (i.e. for a missing weekday evening survey, the mean of all weekday pm's in that JW). Estimated and actual data were combined to estimate total catch for the season in these areas.

FIGURE 2. Locations of the two creel survey areas in the South Fork Trinity River basin surveyed during the 1991-1992 season.

During the creel survey, clerks followed a set route based on a predetermined schedule, and monitored each access site for anglers. Anglers observed fishing during the survey periods were contacted and interviewed for hours fished that day, success, angling method, and county or state of residence. Sport-caught steelhead observed were measured (cm FL), and examined for fin clips and external tags. The number of any tag observed was recorded, the fish's sex determined, its spawning condition noted, and a scale sample taken. We classified steelhead < 25 cm FL as juveniles, > 25 cm and < 35 cm as half-pounders, and > 35 cm as adults (Kesner and Barnhart 1972). Water clarity was measured with a secchi disk in designated pool areas in both sections daily. When the river was judged to be "unfishable" due to high turbidity, no survey effort was recorded.

Tag Return and Steelhead Harvest Rates

All reward tags from Sandy Bar Weir that we observed during the creel surveys were left with the angler for them to return to us by mail. This was done so that we could calculate an overall SFTR basin sport harvest rate for fall- and winter-run steelhead. We estimated the sport harvest rate from the percentage of $10-reward tags returned by anglers corrected for non-response, based on the following assumptions: 1) that all tagged fish caught in the sport fishery were recognized as such by anglers, 2) no tags were shed, and 3) there was no differential mortality between tagged and untagged fish. The percentage of reward tags caught by anglers which were not returned to us (i.e., non-response rate) was estimated from the number of reward tags we observed during our creel surveys, and the number of those tags which were subsequently returned to us by mail. The estimated sport harvest rate was determined from the number of reward tags returned by anglers divided by the non-response rate and the number of tags applied at the Sandy Bar weir.

Spawner Surveys

Project personnel conducted walking surveys of tributary streams to the SFTR and Hayfork Creek to document steelhead spawning distribution and timing. The surveys were conducted from 3 April through 1 June 1992. The areas surveyed included: 1) tributaries to the SFTR and to Hayfork Creek in the Hyampom Valley area, 2) tributaries to the SFTR in the upper SFTR basin near the town of Forest Glen, and 3) tributaries to Hayfork Creek near the town of Hayfork, and in the upper Hayfork Creek drainage near the town of Wildwood (Figure 1). Specific creeks surveyed were selected to include those which historically attracted spawning steelhead, and to replicate areas examined in previous CDFG surveys (Miller 1975; Mills and Wilson 1991; Rogers 1972, 1973; Wilson and Collins 1992; Wilson and Mills 1992).

Most streams were surveyed twice. During the first survey, two people walked designated stream reaches recording the length and type of each habitat unit, and observing spawning behavior and individual redd locations. Each habitat unit was classified as either a cascade, pool, riffle, run, or step-run. Last year we did not distinguish step-run units from run units when recording habitat types, but we now believe that the characteristics of step-runs may be a very important factor in redd location. Redds were flagged with surveyor's tape, with the survey date and field notebook description number recorded on the tape. The tape was then attached to nearby structures (such as root-wads, shrubs, or bushes). During the second survey, redd characteristics (area and depth), site descriptions (substrate and cover composition), and stream conditions (water velocities) were compiled for individual redds. New redds established since the first survey were included.

Steelhead Redd and Spawning Habitat Evaluations

We characterized steelhead spawning habitat within the SFTR basin by measuring the physical and hydraulic parameters of redds we observed in spawning areas, and by recording the characteristics and quality of the substrate and associated cover.

Length and width measurements were taken of each redd using a meter stick or tape measure. Length was measured from the head of the redd to the highest point of the tailspill, and width was measured perpendicularly across the widest point of the redd. An index of the surface area occupied by the redd area was calculated as the product of the length and width. Water depths were taken using a graduated top-setting wading rod and water velocities were measured with an electronic flow meter. Two separate water velocity measurements were taken: mean water column velocity (MWCV) and fish-nose water velocity (FNWV). MWCV measurements were taken 60% below the water surface and FNWV measurements were taken 0.12 m above the substrate. Redd substrate composition was determined by assessing the average size of the dominant and subdominant components, and the percent embeddedness of each (Hampton 1988) (Table 1). The water velocity measurements and the substrate analysis were all made approximately 0.15 m upstream of the redd in order to simulate prespawning hydraulic and substrate conditions. Distance to the closest cover, escape or resting place, was noted as well as the dominant habitat type in which the redd was located.

TABLE 1.Criteria used to describe the size of dominant and subdominant spawning gravel substrate.

Adult Steelhead Recoveries at Emigrant Weirs

Downstream emigrant weirs were assembled on lower Hayfork Creek near the town of Hyampom (8.0 river kilometers upstream from the SFTR confluence), on the SFTR near the town of Forest Glen (approximately 150 m below the Highway 36 bridge, RKM 89.6), and on the SFTR below the Hyampom Valley (off of Gates Road at RKM 31.7) to capture post-spawning steelhead emigrating from the basin. Hereafter, these three weirs are referred to as the Hayfork Creek Weir, Forest Glen Weir, and the Gates Road Weir, respectively. We constructed Alaskan-style weirs at the Hayfork Creek and Forest Glen sites, and the CDFG's Trinity Fisheries Investigations Project constructed a weir-panel type weir at the Gates Road site on the SFTR. The Alaskan-style weirs were constructed using a series of panels 3.2 m high and 3.0 m long and supported by wooden tripods set 2.4 m apart and joined together to block the entire river. Each panel contained 1.9-cm EMT conduit pickets set 2.9 cm apart (46 per panel), secured through three aluminum channel sections on the face of the weir. A trap constructed of welded conduit panels and containing a fyke entrance was placed in the river thalweg. All steelhead recovered were: 1) measured (cm FL), 2) given a right operculum punch (ROP), 3) checked for spawning condition, tags, fin clips, and marks, 4) sampled for scales, and 5) released.

In addition to the downstream (emigrant) traps, we also installed upstream (immigrant) traps at each weir to capture spring-run steelhead entering the SFTR basin. These fish were not tagged, but were given a 1/2 left ventral fin-clip (1/2LV) at the Gates Road Weir to prevent any later recounting at the other two upstream weirs. We had also given immigrant fall- and winter-run steelhead caught at the Sandy Bar Weir the same secondary mark (1/2LV). However, we believed that we could distinguish fall- and winter-run steelhead tagged and marked at the Sandy Bar weir from spring-run steelhead marked at the Gates Road Weir, based on the presence or absence of a tag or tag-scar, their sexual maturity, the general coloration and condition of the fish, and fin regeneration of the fall- and winter-run fish.

SFTR Adult Fall-run and Winter-run Steelhead Escapement Estimate

We estimated the adult fall- and winter-run steelhead escapement into the SFTR basin using the Petersen method of mark and recapture (Ricker 1975, p. 78, formula 3.7) by tagging adult steelhead at the Sandy Bar Weir and recovering them through the emigrant weirs (Hayfork Creek Weir, Forest Glen Weir and Gates Road Weir) and creel surveys. Spring-run steelhead at the emigrant weirs were differentiated from fall- and winter-run steelhead by their sexual maturity, coloration, and general condition. Confidence limits were calculated using the Poisson approximation method (Chapman 1948).

Juvenile Steelhead Emigration Studies

We monitored juvenile steelhead emigration patterns by systematically trapping at two sites within the SFTR basin in lower Hayfork Creek, 305 m upstream of its confluence with the SFTR, and in the SFTR upstream of its confluence with Hayfork Creek, within 0.4 km on either side of the Hyampom Road bridge at RKM 49.1 (Figure 1). When flow conditions permitted, we trapped on a weekly basis throughout most of the year, but increased trapping frequency to every third night during the spring period of peak juvenile steelhead emergence 23 April - 22 July (JW 17-29). Juvenile steelhead were captured using fyke nets attached to trap boxes. The nets were constructed of 1.3-cm nylon mesh, had a 1.8-m x 2.4-m upstream opening and extended 10.1 m to a trap attachment frame at the terminal end. Trap boxes were constructed of marine plywood and hardware cloth, and measured 0.8 m x 1.2 m at the opening and were 0.5 m deep. One or two fyke-net traps were fished overnight in the river or stream, for 16 to 24 hour periods, and examined the following morning.

Captured fish were identified to species and enumerated. The first 50 individuals of each species removed from the traps were measured for FL (mm), and scale samples were systematically taken from a maximum of 10 juvenile steelhead, at each trap site, each sampling day. Flows through the net were measured at the net opening, and total volume of stream flows were estimated to the nearest 0.03 m/sec using either a pygmy meter or a Marsh-McBirney (no endoresement implied) flow meter. Water temperatures were monitored using hand-held thermometers or digital recording thermographs.

Habitat Use by Juvenile Steelhead

Seasonal habitat use by juvenile steelhead was studied in Eltapom Creek (Figure 1) during fall 1991 (10-13 September) and spring 1992 (8-12 June). Prior to sampling fish during each season's study, the creek was first surveyed and habitat-typed into individual units of the five basic habitat types: cascades, pools, riffles, runs, and step-runs. Our goal was to sample 1/3 of the available habitat units. In September 1991 we sampled 24 of 70 (34%) units and in June 1992 we sampled 26 of 71 (37%) units. Habitat units were randomly selected for sampling in proportion to the numeric abundance of each of the five basic habitat types.

Sample units were isolated using block nets to prevent any immigration or emigration of fish, and then electrofished. We recorded air and water temperatures with hand-held thermometers, and water velocities (to the nearest 0.03 m/sec) for each individual habitat unit and took photos of each unit sampled. Water velocities were measured at 60% of the total depth from the surface along a line transverse to the flow at points 1/4, 1/2, and 3/4 of the way across the stream. Stream length and width were measured to the nearest 0.03 m in each habitat unit.

All captured steelhead were counted, measured (mm FL), sampled for scales (first five fish per habitat unit), and then released. During the fall 1991 survey, fish <85 mm were classified as Age 0+, fish 86-150 mm as Age 1+, and fish >150 mm as Age 2+. During the spring 1992 survey, fish <60 mm were classified as Age 0+, fish 61-150 mm as Age 1+, and fish >150 mm as Age 2+. We will attempt to refine the age-length relationship through scale analysis. The relative age distribution was determined for fish from each basic habitat type, based on length frequencies. The data were in turn used to determine the relative densities of each age group in each habitat type. The total number of juvenile steelhead present in the entire stream during each survey was then extrapolated, based on the available area.

Last year we intended to use either the two-step or the Zippin method to estimate abundance (Hankin 1986, Price 1982). However, the two-step method proved unsatisfactory because in several cases more fish were caught on the second pass than the first, leading to negative abundance estimates. In addition, several other cases yielded equal numbers of fish on both passes, which leads to division by zero in the formula. The abundance estimates calculated last year using the Zippin method were identical to the total number of fish caught in most of the units sampled. Therefore, density estimates were based on the total number of fish caught, rather than on an estimated number of fish present. This year we have also decided to report density estimates just based on the total number of fish caught.

We have conducted similar studies during fall 1989, 1990 and 1991 and spring 1991 (Wilson and Collins 1992; Wilson and Mills 1992).

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