The California Department of Fish and Games' Trinity Fisheries Investigations Project is conducting a study of spring-run chinook salmon (Oncorhynchus tshawytscha) in the South Fork Trinity River basin. In this effort, we trapped and tagged returning adults, operated recovery weirs, performed creel, snorkel, spawner, redd, and carcass recovery surveys, analyzed adult and juvenile scales, and performed emigrant juvenile trapping.
During adult trapping operations in the spring and summer of 1991, we captured, marked, and released 42 spring-run chinook salmon. Subsequently, 14 spring-run chinook salmon were captured at recovery weirs. Two captured fish had been marked at the tagging weir. During summer snorkel surveys throughout the basin, we observed 66 spring-run chinook salmon. Four fish had been marked at the tagging weir. Due to the low number of mark recoveries, a statistically valid run-size estimate was not obtained. However, based on the above recovery numbers we estimated the run-size to be 232 fish (192 adults and 40 grilse). Based on scale analysis, we determined that the age class distribution of returning fish was 17% two-year-olds, 29% three-year-olds, 45% four-year-olds, and 9% five-year-olds.
Pools were the primary adult summer holding habitat in the basin. Significant numbers of spring-run chinook salmon were found in only eight of the pools we located.
Based on tag returns and creel surveys, the angler harvest was near zero.
Spring-run chinook salmon spawning began on 3 October and ended 26 October. During redd surveys we located 25 spring-run chinook salmon redds. Redds were distributed above and below Forest Glen with only one below Hyampom. Only one chinook salmon carcass was recovered.
Using emigrant juvenile trapping, we determined that spring-run chinook salmon young-of-the-year emigration began on 9 April and ended on 1 July. Yearling spring-run chinook salmon emigrate during winter and early spring.
1. To determine the size, composition, distribution, and timing of the adult spring chinook salmon run in the South Fork Trinity River basin.
2. To determine the angler harvest of spring-run chinook salmon in the South Fork Trinity River basin.
3. To determine life-history patterns of spring-run chinook salmon produced in the South Fork Trinity River basin.
This study is designed to be a thorough evaluation of the life history of spring-run chinook salmon (spring chinook), (Oncorhynchus tshawytscha) within the South Fork Trinity River (SFTR) basin. This is the first major study of spring chinook in this basin. The only other study was conducted in the late summer and fall of 1964 prior to the devastating flood that occurred that year (LaFaunce 1964). The California Department of Fish and Game (CDFG) and the U.S. Forest Service (USFS) have made numerous attempts to count adult spring chinook (and spring-run steelhead) in the SFTR in order to track population trends and evaluate post-flood habitat recovery. These efforts have been sporadic, short term, and made no attempt to determine complete life history (see Appendix 1). Reliable, statistically valid population estimates were not determined.
The size of the current population of spring chinook in the SFTR is not known. Estimates of annual spawner escapements from various sources (Appendix 1) range from multiples of ten to a few hundred fish. It is certain that the population has experienced serious decline since 1964, when the run was estimated to be 11,604 (LaFaunce 1964). A current, valid population estimate and understanding of life history patterns is crucial to any management or restoration effort.
This is the second year of a proposed five-year study of SFTR spring chinook by the CDFG's Trinity Fisheries Investigations Project (TFIP). Since our annual reports normally cover the period from 1 July through 30 June, the snorkel survey, redd and carcass recovery surveys and other observations made during summer and fall relate to those fish trapped and marked during the 1990-1991 reporting period. Also, scales used for life history determinations were obtained from fish trapped and released during the 1990-1991 season.
The study area includes the lower 132 km of the SFTR, the lower 7 km of the East Fork of the SFTR, and the lower 16 km of Hayfork Creek, totaling 155 km of river. Lafaunce (1964) broke this area into 16 roughly equal sections. We attempted to use these same sections for comparison, but for logistical reasons deviated slightly (Figures 1 & 2). We also snorkel surveyed the lower 4 km of Grouse Creek.
This study is comprised of several distinct elements, each generating an escapement estimate or providing information on in-stream life history or distribution.
To meet job objective one, we used the Petersen mark and recapture method, with some variation. We operated a weir at which fish were trapped, tagged, and released. We attempted to recover fish or observe tags in three ways: 1) we operated two recapture weirs (in the mainstem SFTR and in Hayfork Creek); 2) we observed over-summering fish during snorkel surveys of the entire study area; and 3) we attempted to recover carcasses during the spawning season. All data were to be used in making separate Petersen estimates.
To meet job objective two, we utilized non-reward tag returns and a limited creel survey. Historically, poaching has been a problem on the SFTR. Non-reward tags were chosen so as not to increase the potential of poaching for the reward.
To meet job objective three, we analyzed scales collected during the adult trapping operation, performed emigrant juvenile trapping, and made direct snorkel observations of heavily utilized spawning areas prior to, and during the time we expected to see emergent fry.
The trapping weir (Gates Weir) was located at river kilometer (RKM) 31.7, 16 km downstream of the township of Hyampom (Figure 1). The weir functions as a fence across the river designed to guide adult fish into a trap. The weir was constructed of 1.5-m wide by 1.2-m high panels, which reached completely across the river. Each panel was constructed of 1.9-cm (diameter) galvanized conduit welded horizontally on 5.7-cm centers to 2.5-cm by 2.5-cm steel angle iron uprights. Panels were wired together with steel tie-wire, and supported with conventional steel fence posts driven into the river bottom. Netting was placed atop the panels to prevent fish from jumping over the weir.
The trap was 2.4 m long by 2.4 m wide by 1.2 m high (vertical depth) and was constructed with weir panels described above. Two 1.1-m panels were placed inside to form a fyke which led fish into the trap and deterred their escape. The conduit of the upstream and side panels was sleeved with clear vinyl tubing in an effort to minimize potential abrasion to trapped fish. In an effort to make fish more at ease in the trap and less likely to try to jump out, a piece of dark blue nylon fabric was floated on the surface of the water. It was attached inside the trap at the upstream end only. If a fish were to jump and land atop the fabric, the fabric would simply sink allowing the fish to settle back into the water. This device also provided cover and made fish difficult to see from outside the trap. Great care was taken to insure that there were no sharp projections, wire, etc. inside the trap which might injure trapped fish. Foam pipe insulation was used in areas where unavoidable abrasion might occur. The trap was provided with a lockable plywood lid and solid plywood bottom.
Once trapped, fish were netted with a knotless, nylon-mesh net and placed in a tagging cradle. The tagging cradle consisted of a frame constructed from 1.9-cm copper pipe, measuring 100 by 50 cm which was fitted with a nylon cradle to hold fish, and a metric ruler for measuring fork lengths (FL). The cradle assembly was designed to slide into a channel in the front of the trap. A sliding door made from perforated aluminum plate (0.32-cm holes) formed the upstream end. Once marked, fish could be released by opening the sliding door.
Once in the tagging cradle, fish were examined for marks, scars, and general condition, their FL was measured to the nearest cm, and a scale sample was taken. A small knife was used to collect scales from the left side of the fish just below the dorsal fin.
Since we saw no ill effects resulting from tagging a portion of the 1991 cohort, all of the 1992 cohort was tagged, either with a one-half left-ventral (LV) fin clip and a Floy [Note: use of brand name is for identification only. No edorsement by CDFG is implied] anchor tag, or a one-half right-ventral (RV) fin clip and a Lotek1/ implantable radio transmitter. The Floy tag was placed on the left side, just below the dorsal fin, and just posterior to its midline. Each radio tag was inserted into the stomach of an adult chinook salmon through the esophagus, with the aid of a small length of 0.95-cm diameter PVC pipe. The radio tagging operation was done in cooperation with a project led by Dr. Roger Barnhart of the U.S. Fish and Wildlife Service, California Cooperative Fishery Unit, Humboldt State University. [Note: Tagged spring chinook discussed in the RESULTS section of this report refer to those marked during the last reporting period (1990-1991 season). Only half the number of these fish captured were actually tagged (Floy + 2LV), while the other half were fin clipped only (2RV). Discussion of fish tagged and marked in the manner noted above, including radio tagged fish, will be reported in the 1992-1993 Annual Report].
Tagged fish were then sprayed with a 10-20% aqueous solution of Propolyaqua (artificial slime) to help prevent infection caused by the removal of mucus during handling. Spraying was focused on areas such as the caudal peduncle, scale sample site, and the tag location. Care was taken to insure that the head, operculum, and gills were not sprayed with the solution.
Fish which appeared fresh and strong were then released directly from the cradle to the river (upstream) without further handling. During periods of warm water temperature (> 15.5o C) or when fish appeared stressed, they were allowed to swim from the cradle into a recovery tube and held there for at least 60 minutes. The recovery tubes were made from plastic pipe measuring 3.5 m long by 25 cm in diameter. Both the upstream and downstream ends were fitted with sliding plexiglass doors, each with numerous 2-cm holes to allow ample water to flow through the tube. The tubes were oriented with their long axis parallel to the current and held on the river bottom with large rocks. Once the recovery time was over, the upstream door was opened and fish were allowed to leave of their own accord.
We also installed and operated a trapping weir of similar construction to the one described above, in the lower SFTR at Sandy Bar (RKM 2.4), in order to assess any late-entering portion of the spring chinook salmon run. This weir was installed on 4 September 1991 and was operated by TFIP until 1 October. On 1 October the Natural Stocks Assessment Project (NSAP) moved the weir 100 m upstream to a more stable winter site, where they operated it until 11 February 1992.
The only problem we encountered in operating this weir was defining spring-run vs. fall-run chinook salmon (fall chinook), considering that both may be present at the same time. We defined late-entering spring chinook as those fish which were dark, brassy, and may have had other physical marks which indicated they had over-summered lower in the Klamath-Trinity system. Those chinook salmon which appeared fresh, bright, nickel colored, and usually lacked old marks and scars, were defined as fall-run.
Two Alaskan-style weirs were operated in the basin as recovery stations. These weirs were located in Hayfork Creek at Bar 717 Ranch, 8 km upstream from its confluence with the SFTR, and in the mainstem SFTR at Forest Glen Campground (RKM 89.5) (Figure 1). The Alaskan weir also utilizes 1.9-cm galvanized conduit as the "fence", but the support and orientation of the pipe is markedly different than the Gates Weir. The conduit slides through holes in 7.6-cm wide by 3.3-m long aluminum channel and contacts the natural river bottom. The aluminum channel is supported on tripods constructed of 10.2-cm x 15.2-cm and 5.1-cm x 15.2-cm Douglas fir beams. The aluminum channel is oriented horizontally and the conduit is oriented vertically. The spacing between the conduit centers is 5.7 cm. The trap construction is also the same as that noted above, except that vinyl tubing was not used for pipe sleeves in the Hayfork Creek trap. Fish captured in these traps were netted, examined for marks, scars, and general condition, then immediately released. Artificial slime was also applied to each fish just prior to release.
All weirs were operated 7 days per week, 24 hours per day. Each was serviced every morning and often staffed 24 hours per day during busy holiday weekends.
Digitally recording thermographs were used to continually monitor water temperatures at the weir sites. Thermographs were protected inside a steel casing and chained to each weir. Hand held thermometers were used to check water temperature each morning during the routine weir service and prior to the deployment of thermographs.
The snorkel survey was conducted during late June, July, and August of 1991 and covered the entire survey area (Figures 1 & 2). Our primary goal was to count the number of spring chinook salmon and adult steelhead, and to document the number of tagged spring chinook observed in the population. We also documented the number and location of over-summer holding pools utilized by three or more spring chinook.
We used teams of two to three individuals, equipped with mask, snorkel, wetsuit, anti-slip footwear or fins, notepads, and appropriate safety gear (e.g. rescue rope and first aid kit). We typically entered the river at approximately 09:30 and covered 7.0 to 10.5 km of river per day, depending on the length and difficulty of each river section. Each team floated or swam down the river, and recorded the number of adult salmonids and the relative abundance of juvenile salmonids. We also noted habitat types and condition, water temperature, presence of tributaries and their respective temperatures, and the presence or absence of summer holding habitat. The most difficult task was finding adult fish. We spent a great deal of effort searching beneath undercut rocks, ledges, vegetation, overhangs, etc., where fish often hid to avoid divers. Some sections required a good deal of walking and investigation of pools, step-runs, pocket water, and other habitat types which afforded good cover.
Once we determined what pools were being utilized by spring chinook, we made follow-up observations of fish at these sites. We used binoculars from a vantage point which afforded a good view, without the fish being aware of us. Almost every pool had a steep bluff associated with it which was ideal for this purpose. Our goals were to determine if fish were moving into or out of the pools, assess summer mortality, make counts and look for tagged and marked fish, and to observe pre-spawning behavior in order to begin our spawner surveys at the appropriate time.
Surveys began in mid-September and continued through mid-November. We used an aerial survey conducted by helicopter every seven to fourteen days to cover the entire river to ensure we were performing ground surveys frequently enough, and to observe overall trends. Each river section was covered more thoroughly by two-person crews, on foot or in kayaks. When redds were located, their location was documented (by RKM), each was assigned a specific identification number, and the following parameters were measured: over-all size, position in the stream, water depth, current velocity, and gravel size. We also estimated the percent fines in surrounding gravels and noted various aspects of fish behavior (e.g. female present or absent, evidence of false redd activity, estimated time spent on redd). We repeated the surveys until two consecutive trips noted no new redds or live fish.
The carcass recovery effort was conducted in the same manner as redd surveys and focused on those areas where redds and spawning fish were seen during previous surveys. Carcasses were examined for tags and tag scars, fin clips, spawning success, and signs of predation, and a scale sample was taken. Their species, sex, FL, and general condition were also noted. We attempted to correlate each carcass with a known redd. We hoped to be able to determine if redds might actually contain eggs, based on the spawning success of the correlated carcass. We also hoped to determine a tag shedding rate from recovered carcasses.
The angler harvest estimate was generated based upon tag returns and creel surveys. The creel survey was limited this season to seven days due to time and personnel constraints, and was conducted only in sections J and K of the Hyampom basin (Figure 1). This creel survey area covered that portion of the river where over-summering spring chinook were most likely to be caught by anglers. Angler access sites in the creel survey area were identified prior to the survey period. Upstream of RKM 48, fishing was allowed, but harvest of salmonids greater than 35 cm in total length was prohibited. Therefore, no creel survey was attempted above this point.
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 chinook were measured (FL, cm), and examined for fin clips and external tags. The number of any tag observed was recorded, the fish's sex determined, and its spawning condition noted. Scale samples were taken from creeled fish in the same manner as for fish from the Gates Weir.
In-stream life-history patterns were determined from analysis of adult and yearling scales, juvenile emigrant trapping, and snorkel observations of spawning areas performed during late winter and spring.
Scales obtained from immigrant chinook trapped at the Gates Weir and from emigrant yearling chinook trapped at the Forest Glen Weir were cleaned and mounted between two glass microscope slides. Scales were then examined with a microfiche reader. The number of annuli, and patterns on the scale indicating ocean- or stream-type life history were noted. An ocean-type life history was indicated by the presence of the first annulus outside the point of ocean entry. A stream-type life history was indicated by the presence of the first annulus inside the point of ocean entry (Snyder 1931, Mills 1986, Sullivan 1989). The point of ocean entry was identified by the first obvious, pronounced increase in the distance between circuli, as measured outward from the scale nucleus. The number of circuli were counted and the radial distance (mm) measured from the scale focus to the mark indicating ocean entry, the first annulus, between each annulus, and from the last annulus to the scale margin. Each scale set was examined by two readers and their results compared. If the readers were in agreement, we assumed the interpretation was correct. If readers were not in agreement, both readers re-examined the scale set together to determine the correct interpretation.
We monitored juvenile emigration patterns by trapping in the SFTR at Forest Glen, 400 m below the Highway 36 river crossing. We chose this location for three reasons: 1) in our field work or in the literature, we found no evidence of fall chinook spawning this far upstream, so we reasonably were sure that any juvenile chinook salmon captured would be spring-run fish; 2) more than one-half of the spring chinook redds we documented during the 1991 season were less than 12 km upstream of this point; and 3) this site afforded easy access and was less subject to high storm flows than areas farther downstream.
Juveniles were captured using fyke nets attached to trap boxes. The nets were constructed of 1.3-cm nylon mesh, had a 1.8-m- by 2.4-m- upstream opening and extended 10.1 m to a trap attachment frame at the terminal end. Trap boxes were constructed of plywood and hardware cloth, and measured 0.8 m wide by 1.2 m long and 0.5 m in depth (vertical dimension). The fyke-net traps were placed in the river overnight, normally 24 hours, and captured fish were examined the following morning. To minimize the chances of current-induced fish mortality, we placed two trap boxes in tandem so that the current velocity in the last box was less than 0.3 m-per-second. We also formed an enclosure inside the back trap box using hardware cloth with 1.3-cm holes, which allowed chinook salmon fry safe refuge from much larger Age 1+ and 2+ juvenile steelhead.
Captured fish were identified to species and enumerated. Individual chinook salmon and steelhead were measured for FL (mm). The displacement volume was then measured for chinook salmon caught each day. Scale samples were taken from yearling chinook salmon and some steelhead captured. Flows through the net were measured with a Marsh-McBirney flow meter. The total volume sampled was then estimated. Water temperatures were monitored using hand-held thermometers or digital recording thermographs. When flow conditions permitted, we trapped one night-per-week beginning in mid-January, but increased to two nights-per-week once emigration began. We trapped on this schedule until no juvenile chinook salmon were caught for two successive trap weeks, and we felt that emigration was complete.
We made snorkel surveys in the area below Silver Creek Ranch (RKM 101.6 to RKM 99) during February, March, and April of 1992, attempting to observe newly emergent chinook salmon fry. Our intent was to document the timing of emergence to support data from fyke-net trapping and to document fry post-emergence behavior. We utilized the same snorkel methods discussed above, except that we covered only about two to three km of river. We chose this location because it had a relatively high density of redds and good water clarity, even during winter.
During snorkel surveys, we used small dipnets to sweep along stream margins, especially in submerged vegetation. We also used dipnets held at the bottom, perpendicular to stream flow while we disturbed the bottom (gravel and cobble) just upstream. In this fashion any alevins or fry dislodged from the bottom would be caught in the net.
We determined the number of effectively-marked fish by subtracting the number of tagging or marking mortalities recovered at or near the Gates Weir from the number of marked fish. Mortality was considered to be a result of the tagging operation if the fish was discovered dead within 30 days of processing. We did not subtract those mortalities discovered during the snorkel surveys from the effectively-marked population since some over-summer mortality is normal.
As reported in the 1990-1991 Annual Report, during that trapping season we systematically applied anchor tags to every other spring chinook captured, and marked the other half of the spring chinook captured with a RV fin clip only. We assumed that both fin clips and tags would be visible to personnel at recovery weirs and during carcass surveys, but that only tags would be visible during snorkel surveys. Therefore, only half the number of fish marked were considered effectively-marked fish for the snorkel survey run-size estimate purposes.
To determine the run-size above the Gates Weir, we used Chapman's version of the Petersen Single Census Method (Ricker 1975):
N = (M+1) (C+1) , where
(R+1)
N = estimated run size; M = number of fish effectively tagged or marked at the Gates Weir; C = the total number of chinook salmon observed during snorkel or carcass recovery surveys, or at recovery weirs; and R = number of fish tagged or marked at the tagging weir which were later seen during the snorkel or carcass recovery surveys, or at recovery weirs.
In using this method, we assumed that fish trapped and marked or tagged were a random and representative sample of the population; marked or tagged, and unmarked fish were equally likely to be observed in snorkel and carcass surveys, and captured at recovery weirs; tagged and marked fish were randomly distributed throughout the population; marked or tagged, and unmarked fish did not suffer any differential mortality; all tagged and marked salmon were recognized upon recovery at weirs or during the carcass recovery survey; and that only tagged fish would be recognized as such during snorkel surveys.
Some data collected 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 during leap years is added to the 9th week, and the last day of the year is included in the 52nd week. This procedure allows inter-annual comparisons of similar weekly periods.
