The California Department of Fish and Game's Natural Stocks Assessment Project monitored adult steelhead (Oncorhynchus mykiss) migration at various weirs and estimated an escapement of 2,326 steelhead into the South Fork Trinity River basin during the 1990-1991 year.
Based on the results of our creel survey, we estimate 981 anglers fished within the basin landing 43 adult steelhead and five chinook salmon within the 1990-1991 season. The harvest rate of adult steelhead is estimated to be 0.10.
Adult steelhead spawning stock surveys were conducted on 22 streams tributary to the South Fork Trinity River and to Hayfork Creek. We surveyed 120.0 km, observed 7 adult steelhead and counted 239 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.
We captured 1,006 juvenile steelhead emigrating from the upper South Fork Trinity River basin and 1,807 from the Hayfork Creek basin. Peak emigration of Age 0+ steelhead and Age 0+ chinook salmon occurred during May 1991.
Juvenile steelhead habitat utilization in Eltapom Creek, a tributary to the South Fork Trinity River, varied among age groups. During fall 1990, Age 0+ and Age 1+ fish occurred in about equal densities in pools and riffles, but Age 0+ fish were more abundant in runs and step-runs than Age 1+ fish. During spring 1991, steelhead densities were much lower; Age 0+ fish were more abundant than Age 1+ fish in riffles and step-runs, while Age 1+ fish were more abundant in pools. Both age classes of steelhead were equally abundant in runs during the spring 1991 survey.
Six hundred-forty sets of juvenile steelhead scale samples were collected and 280 sets were read and interpreted for indications of various life history characteristics.
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 parameters and seasonal juvenile steelhead standing crops.
The life histories of steelhead (Oncorhynchus mykiss) populations within the South Fork Trinity River (SFTR) basin (Figure 1) are of concern because little data are available regarding juvenile steelhead life history patterns, adult steelhead run sizes, spawner distributions, sport-fishery yields and harvest rates. As a result of poor habitat management within the SFTR basin, the 1964 flood severely impacted the area, causing spawning and rearing habitats within the basin to be severely damaged or, in some instances, lost through excessive siltation. 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 of steelhead habitat requirements and life histories gained in this study.
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 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 inter-annual comparisons of identical weekly periods.
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 13 September 1990 through 1 March 1991. An Alaskan-style weir was constructed using a series of panels 3.2 m high and 3.0 m long set 2.4 m apart and joined together to block the entire river. Each panel contained 1.9-cm EMT (electrical metallic tubing) conduit pickets set 2.9 cm apart (46 per panel), secured through three aluminum channel sections on the face of the weir. A cubic trap consisting of welded conduit panels was constructed in the river thalweg, with an entrance made by opening a portion of the weir and connecting the weir and trap with a fyke entrance.
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. Each steelhead was measured to the nearest cm fork length (FL), and its 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 right ventral (RV) fin clip and a discretely numbered $10-reward anchor tag. We did not tag fish which were excessively stressed by the weir capture and handling process, or those which appeared in generally poor physical condition, to avoid excessive tagging mortality. 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 projects (creel census and weirs for emigrant fish).
Angler harvest of steelhead within the SFTR basin was determined from a systematic stratified creel survey, conducted from 22 September 1990 through 30 April 1991. 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 mainstem 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 for season totals.
During the creel survey, clerks followed a set route based on a predetermined schedule, and examined 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 we 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 determined "unfishable" due to high turbidity, no survey effort was recorded.
We estimated sport harvest rate from the percent of $10-reward tags returned by anglers, based on the following assumptions: 1) a 100% response rate by anglers, 2) that all tagged fish caught in the sport fishery were recognized as such by anglers, 3) no tags were shed, and 4) there was no differential mortality between tagged and untagged fish. The estimated harvest rate of adult steelhead within the SFTR basin was determined from the number of reward tags returned by anglers divided by the number of tags applied at the weir.
Project personnel conducted walking surveys of tributary streams to the SFTR and Hayfork Creek to document steelhead spawner distribution and the occurrence of spawning activity. The surveys were conducted from 27 March through 29 May 1991. 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 Mills 1992).
During each survey, two people walked designated stream reaches carrying field notebooks to record observed spawning behavior, individual redd locations, redd site descriptions, and stream conditions. Redds were flagged with surveyors tape attached to nearby structures (such as root-wads, shrubs, or bushes) with the survey date and field notebook description number recorded on the tape.
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 from the head of the redd to the highest point of the tailspill. Water depths were taken using a graduated top-setting wading rod and water velocity measurements were taken 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 analyses 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.
Emigrant weirs were assembled on lower Hayfork Creek near the town of Hyampom (8.0 RKM 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, the Forest Glen Weir, and the Gates Road Weir, respectively. We constructed Alaskan-style weirs at the Hayfork Creek and Forest Glen sites, and the Trinity Fisheries Investigations Project constructed a weir-panel-type weir at the Gates Road site on the SFTR. The weir panels were 1.2 m high x 1.5 m wide, and constructed of 1.9-cm EMT conduit with 3.2 cm horizontal bar spacing. All steelhead recovered were: 1) measured (cm FL); 2) given an operculum punch at the upper two weirs (left at Hayfork Creek Weir, right at Forest Glen Weir), but were not punched at Gates Road Weir; 3) checked for spawning condition, tags, fin clips or marks; 4) sampled for scales; and 5) released.
In addition to the downstream traps, we also installed upstream traps at each weir to capture spring-run and late winter-run steelhead entering the SFTR basin. Steelhead captured in upstream traps which appeared sexually immature were classified as spring-run fish; if they were sexually mature, they were classified as winter-run fish. These fish were given a 1/2 left ventral (LV) fin clip at the Gates Road Weir to prevent any later recounting at the other two weirs.
We estimated the adult steelhead escapement into the SFTR basin using the Petersen method of mark and recapture (Ricker 1975, p. 78, formula 3.7) by marking 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. Confidence limits were calculated using the poisson approximation method (Chapman 1948).
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 either side of the Hyampom Road bridge at RKM 49.1 (Figure 1). Flow conditions permitting, 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 emigration (22 April through 30 June 1991). 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 placed in the river or stream overnight, for 16 to 24 hour periods, and examined the following morning.
Captured fish were identified to species and counted. 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. Flow through the net was measured at the net opening, and total volume of stream flow was estimated to the nearest 0.3 m/sec, using either a pygmy meter or a Marsh-McBirney flow meter. Water temperatures were monitored using hand-held thermometers or digital recording thermographs.
We studied seasonal habitat use by juvenile steelhead in Eltapom Creek (Figure 1) during fall 1990 (29 August - 4 September) and spring 1991 (3 - 6 June). Prior to each season's study, the creek was first surveyed and habitat-typed into 72 units of the five basic habitat types: cascades, pools, riffles, runs and step-runs. Twenty-four (33%) of the 72 habitat units were randomly selected for sampling in proportion to the numeric abundance of each of the five basic habitat types.
We conducted a similar study during fall 1989 to duplicate an earlier Humboldt State University study (Glase and Barnhardt 1989). In the earlier study, Glase and Barnhardt had habitat-typed the stream into 101 habitat units using only four basic habitat types to describe the stream: cascades, pools, riffles and runs. In our fall 1990 and spring 1991 surveys, however, we included the "step-run" as a fifth basic habitat type, and reorganized the habitat unit designations into 72 units of the five basic habitat types: cascades, pools, riffles, runs and step-runs.
Sample units were isolated using block nets to prevent any immigration or emigration of fish, and then electrofished. During the spring survey, the voltage setting on the electro-shocking unit was set so young-of-the-year fish would not be shocked. This was a misunderstanding on the part of the field crew doing the survey. Although some young-of-the-year fish were caught, their numbers were not representative of the relative abundance of their age group in the survey area. We recorded air and water temperatures, and water velocities (to the nearest 0.031 m/sec) for each of the 72 habitat units and took photos of each habitat unit we 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 1990 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 1991 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 over the course of a year with additional scale analysis. The relative age distribution was determined for fish from each basic habitat type. These 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.
Steelhead life history patterns were described from intensive analysis of scales from juvenile fish. Juvenile steelhead scale samples have been collected since 1988 by CDFG personnel through downstream outmigrant trapping and electrofishing projects. Adult scale samples were also collected during the creel surveys, and at our immigrant and emigrant weirs. Unfortunately, we have found the first two years of growth patterns on adult scales hard to interpret. Thus, emphasis this year was placed on a more intensive study of juvenile scales in order to better understand the patterns of scale development and growth associated with the early life history phase of juvenile fish. This will greatly assist in the interpretation of adult scales in the future.
All scales collected in the field were taken to the lab for processing. Each adult scale sample was cleaned, dried, then mounted between two glass microscope slides. Scale samples from juvenile steelhead did not usually require cleaning. The cleaning process involved soaking scales in distilled water to soften them. Softened scales were rubbed between thumb and forefinger to remove debris. If debris persisted, scales were soaked in a 5% detergent solution made up with distilled water, and then rubbed again as mentioned previously. Softened tissue and debris that continued to adhere to scales after these cleaning processes was peeled off using blunt tipped forceps.
Juvenile steelhead scales were examined to determine age and freshwater life history. Scale samples were read using the Optical Pattern Recognition System (OPRS). The OPRS method digitizes, measures, and records distances for each freshwater circuli on each scale examined. Statistical and graphic software can then be used to analyze scale data. Annuli were determined by the cutting or crossing-over of circuli, incompleteness of circuli, and narrowing of the distance between circuli. A year of growth was considered to be the time from the formation of the last circulus of an annulus to the formation of the last circulus of the succeeding annulus. Circuli between annuli were counted and measured relative to the entire scale length.
The Sandy Bar Weir operated from 13 September 1990 through 1 March 1991, trapping 176 adult steelhead, with the first trapped on 17 September 1990 (Figure 3). Steelhead entered the SFTR basin throughout this period, showing no distinctive immigration peak periods. We feel we measured most of the steelhead run at Sandy Bar but know that the run continued after 1 March 1991 based upon immigrants trapped at our upper SFTR basin weirs (Hayfork Creek, Forest Glen and Gates Road weirs) later in the season. Steelhead immigration and run-timing seems to be more dependent on environmental conditions (storm events with accompanying high flows) rather than calendar dates. The periodic increases in steelhead capture numbers at the weir directly coincided with storm events.
Ten of the 176 steelhead captured at the Sandy Bar Weir carried tags previously applied at the Willow Creek Weir (Figure 1). We tagged the remaining 166 fish with $10-reward anchor tags and gave all 176 steelhead 1/2 RV fin clips. Mean FL of all 176 steelhead examined was 60.0 cm (Figure 4). Gill-net scars (37.6%) and predator scars (29.0%) were the most common scars seen on steelhead trapped at the weir (Table 2). Travel times for the 10 fish previously tagged at the Willow Creek Weir ranged from 2 to 84 days (d), and averaged 37 d (Appendix 2).
The creel survey was conducted on the SFTR between 22 September 1990 and 30 April 1991, an interval of 221 d. The lower survey section (Figure 2) was monitored for angler activity on 162 d and a creel survey conducted on 86 d of this period. The upper survey section was monitored for 210 d and a creel survey conducted on 108 d of the period. Creel surveys were not conducted when monitoring indicated no anglers were present or flows were high enough to prevent successful angling. The river in the lower survey section was considered "unfishable", based on high flow or turbidity observations, for four (2.5%) of the days it was surveyed and throughout the month of March 1991, while the upper section was determined "unfishable" for four (1.9%) of the days it was surveyed.
During the survey, 136 anglers were interviewed, 33 (24.3%) within the lower section and 103 (75.7%) within the upper section. Peak angling activity (22.6%) was observed within the upper survey section, in the lower Hyampom Valley near Big Slide Campground, with the rest of the anglers' effort distributed over a range of other sites. Of the 136 anglers interviewed, 28 were observed fishing at multiple locations in the upper survey section on the same day. Each site of angling activity was counted but the angler was not recounted when observed at a different location on the same day (Table 3).
Five adult steelhead and one adult chinook salmon were observed in the catch (all in the upper survey section). No half-pounder steelhead were observed in either section. Based on extrapolations of the creel survey data, an estimated 207 anglers within the lower section landed no adult steelhead (Table 4), while an estimated 774 anglers within in the upper section landed an estimated 43 adult steelhead and five chinook salmon (Table 5). County of origin was tabulated for 136 anglers. The majority (89.0%) of the anglers fishing within the SFTR basin were from Trinity and Humboldt counties (Table 6).
Excluding the unfishable days, water clarity ranged from 2 to 150+ cm in the lower survey section, and from 14 to 150+ cm in the upper survey section. Water temperatures ranged from 3E to 21E C and averaged 10E C in the lower survey section, while the upper survey section ranged from 1E to 17E C and averaged 8E C.
Three steelhead tagged at the Sandy Bar Weir were observed in the catch, and all three tags were subsequently returned by anglers, indicating a 100% response rate. The estimated harvest rate of 8% for adult steelhead (95% Poisson confidence interval [C.I.]: 5% to 14%) was determined by dividing the total number of tags returned by anglers (14), by the number of reward tags applied (167).
