The California Department of Fish and Game's, Trinity Fisheries Investigations Project conducted an adult spring-run chinook salmon (Oncorhynchus tshawytscha) tagging operation in the South Fork Trinity River below the Hyampom valley from 28 April through 18 July 1991. We marked and released 34 adult and 9 grilse spring-run chinook salmon, 22 of which were tagged with anchor tags and marked with a left ventral fin clip, and 21 were marked with a right ventral fin clip only. As of 18 July 1991, no tags had been returned. Coincident with this operation, 47 fall- or winter-run and 18 spring-run steelhead (O. mykiss) were captured, marked, and released. We will observe and recover adult spring-run chinook salmon during snorkel, spawning, and carcass surveys scheduled for summer and fall 1991 to generate an escapement estimate. We will determine instream life history patterns from analyses of adult and yearling scales, juvenile trapping, and direct observations.
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 (Oncorhynchus tshawytscha) within the South Fork Trinity River (SFTR) basin. This is the first major study of spring-run chinook salmon (spring chinook) in the basin. The only other study was conducted in the summer and fall of 1964 prior to the devastating flood that occurred later 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 salmonids in the SFTR in an effort to track population trends and to evaluate habitat recovery (Healy 1969; Rogers 1970, 1971; Fox 1972; Miller 1974, 1975; Ross and Hawks 1975; Lee 1976; Freese 1979, 1982; LaFaunce 1980; Strate and Underwood 1982; Mitchell 1985; Zustak 1986; Wood 1989; Gerstung 1990). These efforts have been sporadic and made no attempt to determine the complete life history of spring chinook. Reliable, statistically valid, population estimates were not determined.
The current size of the population of spring chinook in the SFTR is not known. Estimates of annual spawner escapements from various sources (see above) 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 fish (LaFaunce 1964). A current, valid population estimate and understanding of life history patterns is crucial to any management or restoration effort.
This is the first year of a five year study of SFTR spring chinook by the CDFG's, Trinity Fisheries Investigations Project (TFIP). As of 18 July 1991, only two and one-half months of work had been completed. Consequently, the results presented here are incomplete. Other elements of our study not covered in this report include a spring chinook spawner survey, carcass recovery effort, angler harvest estimate, and a determination of instream life history patterns.
The study area includes the lower 125 km of the SFTR, the lower 7 km of the East Fork of the SFTR, and the lower 16 km of Hayfork Creek, totaling 148 km of river. Lafaunce (1964) and USFS surveys broke this area into 16 roughly equal sections. We attempted to use these same sections for comparison, but for logistical reasons deviated slightly from their delineations (Figures 1 & 2).
This study is composed of several distinct elements, each generating an escapement estimate or providing information on instream life history. However, due to the timing of the reporting schedule, only the adult trapping and tagging portion of the study designed to monitor the first half of the apparent bimodal immigration of spring chinook will be covered here in any detail.
An adult spring chinook capture and tagging operation was conducted during the spring and early summer of 1991. The 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 2.13 m long by 2.13 m wide and 1.2 m high and was constructed with the weir panels described above. Two 1.1-m panels were placed inside to form a fyke which lead fish into the trap and deterred their escape. The conduit of the "head" or upstream panel was sleeved with clear vinyl tubing and oriented vertically in an effort to minimize potential abrasion to 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 above. Great care was taken to insure that there were no sharp projection inside the trap which might injure trapped fish.
Once trapped, fish were placed in a closed tagging box to allow the use of an anesthetic. However, anesthesia was never necessary, as fish were not difficult to handle. The box was constructed of 1.27 cm thick plywood and measured 48.3 cm wide by 48.3 cm tall, and 91.4 cm long. It was fitted with a nylon tagging cradle and a metric ruler for measuring fork lengths (FL).
Once in the tagging box, fish were examined for marks, scars, and general condition, their FL was measured to the nearest cm, and a scale sample was taken. Fish were then marked in one of two ways. Out of concern for potential tagging mortality, only half the fish were tagged. These fish received a 1/2 left ventral (LV) fin clip and a Floy anchor tag placed on the left side just below the dorsal fin, posterior to the midline. The other half of the fish received a 1/2 right ventral (RV) fin clip. The fish were then sprayed with a 10-20% aqueous solution of Propolyaqua1/ (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 were then placed into a recovery box for 45 to 60 minutes. The recovery box was constructed of plywood and measured 0.61 m wide by 0.61 m tall by 0.91 m long. It was lined with 0.95-cm thick, high density foam padding, and had a closable lid to provide cover. Both the upstream and the downstream ends were constructed of perforated plate (0.32-cm holes) which allowed ample water to flow through the box. Once the recovery time was met, the sliding upstream gate was opened and fish were allowed to leave of their own accord.
All equipment used in the tagging operation, such as the tagging gun, fin clippers, and scale sample knife, were disinfected with 70% isopropyl alcohol prior to each use to minimize the potential of infection.
A digitally recording thermograph was used to continually monitor temperature at the Gates Weir site. The thermograph was protected inside a steel casing and chained to the weir. Prior to the deployment of the thermograph on 23 May 1991, hand held thermometers were used.
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- x 15.2-cm (4- x 6-in.) and 5.1- x 15.2-cm (2- x 6-in.) Douglas fir beams. The aluminum channel is oriented horizontally and the conduit is oriented vertically. The spacing between the conduit pieces is 5.7 cm. The trap construction is also the same as that noted above, except that vinyl tubing (as pipe sleeve) is not used. 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 three weirs were operated 7 days per week, 24 hours per day. Each was serviced every morning and usually staffed 24 hours per day during busy holiday weekends.
The snorkel survey is another element of this project which is already underway. We use a team of two to three individuals, equipped with mask, snorkel, wetsuit, anti-slip footwear or fins, and appropriate safety gear (i.e. rescue rope and first aid kit). We enter the river at approximately 9:00 AM and cover 7.0 to 9.7 km of river per day, depending on the length and difficulty of the river section. The team floats or swims down the river, and records the numbers of adult salmonids and the relative abundance of juvenile salmonids. We also note habitat type and condition, water temperature, presence of tributaries and their respective temperature, presence or absence of summer holding habitat, and other noteworthy features. The most difficult task is finding adult fish. We spend a great deal of effort searching beneath undercut rocks, ledges, vegetation, overhangs, etc., where adult fish hide during daylight hours. Some areas require a good deal of walking and investigation of pools, step-runs, glides, and other habitat types which afford good cover.
Other aspects of the project are spawner and carcass surveys, estimation of angler harvest, and determination of in-stream life history patterns. To accomplish the spawner survey, we will use an aerial survey conducted by helicopter to select sections of the river to be covered in detail by two-person crews, on-foot or in kayaks. The carcass recovery effort will focus on those areas covered in the spawner survey. We will also attempt to determine a tag shedding rate during the carcass survey. An angler harvest estimate will be generated, based upon tag returns and an on-going creel survey. In-stream life history patterns will be determined from analysis of adult and yearling scales, and a juvenile trapping and observation program to be performed during late winter and spring.
Use of Standard Julian Week
All 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 included in the 9th week, and the last day of the year is included in the 52nd week. This procedure allows inter-annual comparisons of identical weekly time periods (Appendix 1).
Obviously, those portions of this project which are yet-to-be performed will not be discussed. Preliminary results and discussion are presented for those portions of the project which are still in progress. All results must be considered preliminary, since spring chinook are believed to have a bimodal entry pattern into the SFTR, and we may only have seen the early entering portion of the run as of 18 July 1991.
Trapping and Tagging
We operated the Gates Weir for 80 days, from 28 April through 18 July 1991. During this period, immigrant and emigrant traps were maintained. On 2 and 3 June we were not able to fish because of vandalism to the weir. We captured, marked, and released 34 adult and 9 grilse spring chinook, 8 unspawned adult winter-run and 18 adult spring-run steelhead from the immigrant trap. We captured, examined, and released 39 out-migrant (spawned) adult fall- or winter-run steelhead from the emigrant trap (Table 1).
Spring chinook captured at the Gates Weir averaged 60.4 cm FL (Figure 3). We established 55 cm FL as the length separating adults and grilse in the mainstem Trinity River. Until we obtain additional length data and analyze our scale collection, we will continue to use this value. However, current data are inadequate to make a final determination at this time. Length data for steelhead captured at the Gates Weir are reported in Chapter III of this annual report, and will not be discussed here.
Operation of the weir was largely successful, but we had some difficulty maintaining its effectiveness. Approximately one-third of the substrate covered by the weir was gravel and course sand. Early in the operation of the weir, as water levels began to drop, the current shifted such that it began to erode and undermine the gravel-based portion of the weir. Consequently, holes continuously formed beneath the weir, and for a few hours on some days fish could pass undetected. As soon as field staff arrived at the site, they would plug the holes with sand bags or large rocks. By late June, these efforts solved the erosion problems. Next season, weir panels will be arranged in a manner that will minimize the undercutting problem. In addition, a more aggressive maintenance schedule should prevent holes from reaching a size that will allow fish to escape past the weir.
The trap design was adequate, but could be improved. Because of the natural cobble bottom, we had some difficulty netting suckers and some steelhead. Our next trap will be constructed with a plywood bottom. The use of vinyl tubing on trap panels as abrasion prevention appears to work well, and will be utilized to a greater extent on our new trap. The nylon fabric, floating cover was very effective and will continue to be used unchanged.
The Floy Anchor tags were quick and easy to apply, and appeared to cause little discomfort to the fish. Depending on the results of our tag effects and tag-shedding study, their use may be continued next season. We hope to develop a tag-shedding rate during the carcass recovery portion of the project. Observations made during the snorkel surveys, spawner survey, and carcass recovery survey will be used to evaluate other possible tagging effects based on signs of fungus, bruising, necrosis, and differential mortality between tagged and untagged fish. If no fungus or other problems associated with tagging are apparent at the end of this season, all spring chinook trapped next season will be tagged as described. If application of Propolyaqua as a prophylaxis to fungus growth is effective, we will continue to use it. No tags had been returned as of 18 July 1991.
Since it has been unnecessary to anesthetize fish before tagging, next season we will utilize a tagging cradle which allows water to flow through it. The cradle will also be designed with a sliding door at the upstream end, so that fish can be released directly from it, thus eliminating one handling operation.
As of 18 July 1991, no spring chinook had been captured at the Hayfork Creek Weir, while 14 had been captured at the Forest Glen Weir. Of these 14 fish, two were RV-clipped, indicating that they were processed through the Gates Weir. Since no tagged fish were recovered, no conclusions or discussion will be attempted at this point regarding our data (Table 2).
The thermographs worked very well and will continue to be used to monitor river temperatures. Data collections are incomplete at this time and, therefore, will not be reported.
As of 18 July 1991, only a small portion of the river had been examined via snorkel survey. The snorkel survey methodology appears adequate and will remain unchanged. Prior to the removal of the Gates Weir, a snorkel survey was completed for that portion of the river below the Gates Weir. Water temperatures ranged from morning lows of 15.5 to afternoon highs of 25oC. We observed 13 adult and one grilse spring chinook, including one dead, 76-cm female. The cause of death was not obvious but did not appear to be predation. However, thermal stress may have been a factor, as water temperatures reached 25oC.
As noted above, we captured and released 43 spring chinook and 65 steelhead at the Gates Weir. Only 15 percent of the steelhead captured showed scars compared to 67 percent of the spring chinook (Table 3).
1. Trapping efficiency at the Gates Weir should be improved through a different arrangement of weir panels and a more rigorous maintenance schedule.
2. A new, slightly larger trap with a plywood bottom should be used to improve dip-netting efficiency. It should also be fitted with a plywood lid and padlocked to prevent entry by unauthorized persons. The use of vinyl tubing as a sleeve over the conduit of trap panels should be expanded in an effort to minimize abrasion to trapped fish.
Fox, C. 1972. Report to supervisor; United States Forest Service, Shasta-Trinity National Forest, 2 August 1972. 15 p. (memo). Available from Trinity Fisheries Investigations Project, P.O. Box 1185, Weaverville, Ca. 96093.
Freese, L. 1979. Summary Report for survey of the South Fork Trinity River, Shasta-Trinity National Forest, United States Forest Service, 2 October 1979. 93 p. (memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Freese, L. 1979. 1982. Personal communication to E. Gerstung, Region I, California Department of Fish and Game, 27 February 1982. 2 p. (memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Gerstung, E. 1990. Observations of summer steelhead and spring chinook in the Forest Glen area, 8 October 1985. 3 p. (file memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Healy, T. 1969. Letter to Fisheries Management Supervisor, Region I, Calif. Dept. of Fish and Game, 29 September 1969. 1 p. (memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
LaFaunce, D. A. 1964. A king salmon spawning survey of the South Fork Trinity River. Calif. Dept. of Fish and Game, Mar. Res. Admin. Rep. No. 67-10. 13 p.
LaFaunce, D. A. 1980. Letter to Fisheries Management Supervisor, Region I, Calif. Dept. Fish and Game, 20 August 1980. 1 p. (memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Lee, D. 1976. Letter to Fisheries Management Supervisor/file, Region I, Calif. Dept. of Fish and Game, 25 October 1976. 1 p. (memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Miller, E. 1974. Letter to Associate Biologist LaFaunce, Region I, Calif. Dept. of Fish and Game, 23 September 1974. 4 p. (memo with maps). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Miller, E. 1975. Letter to Associate Biologist LaFaunce, Region I, Calif. Dept. of Fish and Game, 26 August 1975. 6 p. (memo with maps). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Mitchell, W. 1985. 1984 Salmonid survey for the South Fork Trinity River. Letter to project coordinator, United States Forest Service. 2 p. (memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Rogers, D. 1970. Letter to Associate Biologist LaFaunce, Region I, Calif. Dept. of Fish and Game, 2 August 1970. 1 p. (memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Rogers, D. 1971. Letter to Associate Biologist LaFaunce, Region I, Calif. Dept. of Fish and Game, 26 August 1971. 1 p. (memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Ross, C., and H. Hawks. 1975. Report to supervisor, Shasta-Trinity National Forest, United States Forest Service, 12 June 1975. 5 p. (memo with forms and map). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Strate, B., and T. Underwood. 1982. Report to supervisor, Yolla Bolla Ranger District, United States Forest Service, 7 July 1982. 8 p. (memo with survey forms and map). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Wood, R. 1989. Letter to Associate Fishery Biologist Phil Baker, Region I, Calif. Dept. Fish and Game, 9 September 1989. 2 p. (memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
Zustak, J. 1986. Letter to United States Forest Service Fisheries Planning Unit, Shasta-Trinity National Forest, 22 September 1986. 2 p. (memo). Available from TFIP, P.O. Box 1185, Weaverville, Ca. 96093.
