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State of The Resources Agency DEPARTMENT OF FISH AND GAME

A STUDY OF TRINITY RIVER STEELHEAD EMIGRATION

Anadromous Fisheries Branch

Anadromous Fisheries Branch

Administrative Report No. 77-5 'TRIIIITY KIVER BASIN RESOURCE LIBRARY

Anadromous Fisheries ~ranchZ/

ABSTRACT

This report describes a 1974-1976 study of steelhead emigration in the Trinity River, California.

Fyke net catches at two stations were used to calculate indices of the numbers of wild and hatchery steelhead leaving the Trinity River in the springs of 1974, 1975 and 1976.

The successful spring smolt emigration for hatchery and wild fish was generally confined to fish at least 150 mm (6 inches) -FL. Trinity Hatchery produced an estimated 16.3 to 60.5% of the successful spring Trinity River smolt emigration during the years 1974, 1975 and 1976.

L/ Anadromous Fisheries Branch Administrative Report No. 77-5. Submitted December 1976. This work was performed as part of Anadromous Fish Conservation Project California AFS-20, "Trinity River Projectl1, supported by Anadromous Fish Act funds. 2/ This report wasmtten by Steven N. TayloJ and is based on data from a program planned by Paul M. Hubbell. The 1974 and 1975 investigations were conducted by Richard J. Hallock; 1976 investigations were conducted by William Heubach. Others who contributed include California Department of Fish and Game employees Edward Miller, John Shaver, Richard Haley, John Rowell, Frank Hall, Charles Brown, Anne Gerolamy, and Nanci Dong, and U. S. Fish and Wildlife Service employees Jody Hoffman, Dave Patula and Gary Rankel. The California Department of Water Resources and the U. S. Bureau of Reclamation were cooperators in the study and both made important contributions. INTRODUCTION

Background "The Trinity River, [~i~ure11 located in northwestern California, drains 2,965 square miles of largely mountainous terrain in Trinity and Humboldt Counties. The river, principal tributary to the , originates approximately 20 miles southwest of Mount Shasta in rugged canyons between the Scott Mountains on the northwest and the Eddys on the east. It enters the Klamath at Weitchpec, about 42 river miles upstream from the Pacific Ocean. Altitudes in the basin range from about 9,000 feet in the headwaters to 275 feet where the Trinity and Klamath join." (Prom Hubbell 1973.)

Before the mid-1960's the upper Trinity supported an annual run of several thousand steelhead (Salmo gairdnerii gairdnerii), and an important steelhead sport fishery. The average of annual adult counts at Lewiston, 1958-1964 was 3,034 (~ubbell,ibid. ).

Lewiston Dam, part.of the U. S. Bureau of Reclamation's Trinity River Project, was completed in 1962. It is an absolute barrier to anadromous fish migration. Trinity Hatchery was built to mitigate for upstream salmon and steelhead habitat losses caused by the project.

Unfortunately, the steelhead mitigation program has not been successful; the numbers of steelhead entering Trinity River Hatchery (1966-73 average, 249 fish) are far below the preproject runs past Lewiston (~rinityHatchery records).

Numerous hypotheses have been asserted to explain low adult steelhead return rates to the Trinity River. Collectively, they consider problems in every stage of steelhead life history. Hubbell (ibid.) summarized these hypotheses and proposed several studies designed to determine the causes of the observed changes. The ultimate objective of this program is to restore Trinity River salmon and steelhead runs to preproject levels.

This paper presents the results of a 3-year juvenile steelhead emigration study, the first of Hubbell's proposed studies to be implemented.

The objectives of this study were to estimate: I. The temporal migration patterns of wild- and hatchery-produced smolts and parr in the Trinity River. 2. The numbers of smolts and parr reaching Big Bar, approximately 105 river km (65 miles) from the mouth of the Trinity. 3. The numbers of smolts and parr reaching Weitchpec (the mouth of the Trinity). 4. The sizes of fish collected at each of these sites. 5. The spring emigration pattern of juvenile steelhead (hatchery and wild fish combined) in the Klamath River near its confluence with the Trinity River. + ------0 REGON CALIFORNIA

A NETTING SITES USGS MONITORING STATIONS

SCALE IN MILES 0 10 20 30 40 50 SCALE IN KILOMETERS

Figure 1. Map of the study area. METHODS

Planting of ~roductio$/ Fish

All hatchery steelhead released in the Trinity River in 1974, 1975, and 1976 were fin marked before release.

A sample was drawn from every production group several days before release, and the fish in the sample measured.

In February of 1975 and 1976 yearling steelhead were graded to separate fish which presumably would reach 150 rnm (6 inches) FL by May 1, and those which would not. The larger yearlings were planted each spring and the smaller yearlings were held over for release as two-year-olds the following springs. Further, in February 1976 the two-year-old steelhead on hand were graded to separate fish larger and smaller than 197 mrn (7-3/4 inches) TL. All classes resulting from grading were distinguished by differing finyarks.

The planting of all production steelhead was done within 8 km (5 miles of the hatchery) (planting data are summarized in Table 1).

Fyke Net Sampling

Netting Gear and Operations

Downstream-moving fish were captured in fyke nets at two locations in the Trinity River--Big Bar, which is approximately 74 km (46 miles) downstream from the Trinity River Hatchery, and Weitchpec (the confluence of the Trinity and Klamath ~ivers),about 179 km (111 miles) downstream from the hatchery. The Weitchpec sampling site was approximately 183 m (200 yards) from the actual mouth of the Trinity.

Fish moving downstream were also eke-netted in the Klarnath River at a point approximately 183 m (200 yards) upstream from its junction with the Trinity.

The sampling gear consisted of 10-m (35-ft) long eke nets with live boxes attached to the cod ends, and was similar in design to the gear used and described in detail by Healey (1973). The nets were constructed of 3-, 3- and 4.6-m (lo-, 10- and 15-ft) sections of 7.6-, 5.1- and 2.5-cm (3-, 2- and 1-inch) stretch mesh net, respectively. The frames forming the upstream openings of the nets were approximately 3 m wide and 1.4 m tall (9 x 4.5 ft). The nets were held in position with cables attached to the bank. .

One net was fished at Big Bar all three study years. At Weitchpec, one net was fished in 1974; and in 1975 and 1976 two nets were fished, from 3- 14 m (3-15 yards) apart. A single net was fished in the Klamath at Weitchpec all three years.

3/ Production fish are fish released in the normal hatchery production program. The term is used to distinguish them from smaller groups of fish released near downstream netting sites to test the efficiency of the nets. Table 1

Summary of Production Steelhead Releases Made in the Trinity River, 1974-1976 (All Fish Released Were Reared at Trinity River Hatchery Except 1974 Broodyear Mad River Group Which Was Reared at Mad River Hatchery)

Brood Mean Mark year Strain Location ~ate(s) Number FL (mm)

Ad-LV 1973 0.5 km from hatchery 5/ 6/74 61,000 122.2

Ad-RV 1973 Washougal 8 km from hatchery 5/3-6/74 67,200 154.0

LV 1973 Trinity River 8 km from hatchery 5/2-3/74 195,020 149.2

RV 1973 Trinity Brood* 0.5 km from hatchery 5/ 6/74 62,270 142.8

D-LM 1974 Trinity River 0.5 km from hatchery 5/ 5/75 16,906 191.6

D-RM 1974 Mad River 0.5 km from hatchery 5/5-6/75 50,550 178.8

RV 1975 Trinity River 0.5 km from hatchery 4/23-5/3/76 98,607 198.8 and at hatchery Ad-RV 1975 Klamath River 0.5 km from hatchery 4/23-5/3/76 111,966 164.2 (Iron Gate Hat. ) and at hatchery Ad 1975 Washougal 0.5 km from hatchery 4/23/76 24,394 177.3

LV 1975 Trinity River At hatchery 4/23/7 6 31,509 198.0

Ad-LV 1974 Klamath River 0.5 km from hatchery 4/23/76 37,221 185.2 (Iron Gate Hat.) LP 1974 Trinity River 0.5 km from hatchery 4/ 1/76 21,630 238.9

Ad-LP 1974 Klamath River 0.5 km from hatchery 4/ 1/76 9,750 256.6 (Iron Gate Hat.) * Progeny of Trinity Hatchery brood stock. Spring netting began in either March or April each year, and continued into June (Table 2). Table 2

Spring Fyke-net Sampling Periods, Trinity and Klamath Rivers, 1974-1976

# Trinity River at Trinity River at Klamath River at Big Bar Weitchpec Weitchpec

April 24-June 28, 1974 April 17-June 28, 1974 April 17-June 27, 1974 March 4-June 21, 1975 March 7-June 21, 1975 March 13-June 21, 1975 March 5-June 16, 1976 March 5-June 18, 1976 March 5-June 5, 1976

In 1974 a single net was also fished intermittently in the Trinity at Weitchpec from September 14 through November 30 to determine if a significant downstream movement of juvenile hatchery-reared steelhead was occurring in the fall.

In the Trinity, so long as there was no danger of their washing away, the nets were positioned in the fastest-flowing water at each site. In the Klamath, boat traffic past the netting site necessitated placing the net near the edge of the main channel, rather than in the center of it. The gear at all sites was repositioned often (daily during some periods), as flows fluctuated.

In the Trinity, the nets were removed from the water when rising flows reached about 142 m3/sec (5,000 cfs) at Big Bar and about 212 rn3/sec (7,500 cfs) at Weitchpec. When discharge appeared to be dropping, the nets were kept in the water re ardless of how high the water was. When discharge exceeded about 142 m I/sec (5,000 cfs) the gear was kept out ofthe maximum- velocity area of the channel (the gear was probably much less effective under these conditions).

High or rising flows prevented or complicated netting operations in the Trinity in 1974 until May 1, and in 1975 until mid-April, from April 25-30, and from May 15-23. High or rising flows were not a problem in fall 1974 or spring 1976. Only in 1975 did high flows require removal of the nets after the marked hatchery fish had been released.

Netting operations in the Klamath were not interrupted by high or rising flows in either 1974or 1976. In 1975, however, high water forced removal of the Klamath net for the periods March 17-April 3, April 24-27 and May 14-21.

All nets were tended twice daily, usually between 0800 and 1000 and between 1500 and 1700. At these times fish contained in the live boxes were processed and then returned to the river. Processing the Samples

Every study year, all net-caught steelhead were measured to the nearest rnrn (FL),- and all marks recorded. In 1976 each wild steelhead captured was also categorized as either a "smolt" or a "parrrT, based on: (1) presence of parr marks, (2) rrlooseness" of the scales, (3) apparent condition ("fatT1or TTslimrl),and (4) darkening of the posterior caudal fin margin. The categorization was subjective to some extent, but size was not one of the criteria used. The presence of parr marks was the .criterion given the greatest weight in fish which appeared to be transitional. Any fish with visible parr marks was categorized as a parr . Flows and Water Temperatures

No consistent measurements of temperature or flow were collected either at the planting area or at the netting sites. However, records are available from United States Geological Survey (usGS) monitoring stations located close enough to the three Trinity areas so that the measurements at the monitoring stations approximate conditions at the planting and sampling sites. Daily streamflows (Figure 2) and water temperature maxima (~igures3 and 4) are presented for the USGS monitoring stations at: (1) Lewiston, (2) Burnt Ranch, approximately 32 river km (20 miles) downstream from the Big Bar netting site, and (3) Hoopa, approximately 16 river km (10 miles) upstream from the Weitchpec sampling site (Figure 1).

Estimating Emigration

The catch during any period may be used to estimate the numbers of fish reaching the netting site during that period if it is possible to make a reasonable approximation of the net efficiency?/ during that period. -? - L Before the 1974-76 experiments began, it was known vulnerability of a grou of fish moving downstream could be affected by (17 attributes of the fish which influenced their behavior (larger, "wilderTr, healthier fish may be better able to avoid the nets) and (2) physical factors which affect the operation of the sampling gear (size of net, net placement, velocity of flow, etc.). The following is a discussion of the methods used to estimate net efficiencies.

The design for estimating net efficiency included periodically (approximately weekly) releasing small groups of steelhead, (from several hundred to about 4,00O/group) of strains identical to those released in the production program each year. These tests were conducted each study year in the Trinity at Weitchpec and in 1976 at Big Bar.

41 The term "net efficiencyTTin this report is used to connote the number of steelhead caughtf the number reaching the netting site. MARCH I APRIL I MAY I JUNE Figure 2. Daily mean flows at three Trinity River monitoring stations (data preliminary and supplied by the California Department of Water Resources ) . 26 - - 24 - HOOPA 22 - - 20 - - 18 - - 16 - - - 14 - - - - 12 - - - - 10 - - 8 - - 0 - - 0 6- - <- - - Z r; 4- - r4 - - + 2- - i - < - 0.- I I I - - a. w - - W - = 22 - + - BURNT RANCH 2 20- W a - 2E 18 + - 16 - 14 - - - 12 - - - 10 - - - 8 - - - 6 - - - 4 - - 2 - -

0 Ill 1 I 30 MARCH 1 APRIL I MAY I JUNE Figure 3. Daily water temperature maxima at two Trinity River monitoring stations. (Data preliminary and supplied by the California Department of Water Resources.) 20 - 18 - 1974 t -.. ::-. .. 0 .:. . . 0 - 1975 . '..:a- - 16 - ....,. ..-. :.:" - -x 1976 ...... i' 14- t-": r: - X y.. ' :/' d . 0. ,... C . - => 12- -1 - - - n= W - ," 4- W

+ 2- - *lo 0 1111: II*lo MARCH I APRIL I MAY I JUNE

Figure 4. Daily water temperature maxima, Trinity River at Lewiston (data from U. S. Geological Survey records; 1976 data preliminary, subject to revision). No efficiency tests were conducted in the Klamath River.

The efficiency fish were released at each station approximately 274 m (300 yards) upstream from the netting sites. For each strain, the efficiency fish were of comparable size and had fin marks identical to those of the production fish. The efficiency fish were additionally marked with either a maxillary or caudal nip or a cold brand to identify release location (Big Bar or ~eitchpec)and time (day or night). Approximately one-half the efficiency test fish were released in the daytime (between 0800 and 1100) and one-half at night (between 1830 and 2100).

: Prior to the experiments, it was presumed the test fish would move the 274 m (300 yards) downstream soon after release, and that in all other ways their behavior would approximate that of the production fish moving past the netting sites. Provid.ing the above were true, expanding the catches by the results of the efficiency tests would produce estimates of emigration, corrected for error caused by changing net efficiency.

The generalized model used to expand catches was as follows:

Expanded catch = catch x efficiency fish released efficiency fish recaptured

Day and night catches were treated separately. In 1974 and 1975 the netting periods were stratified by week (actual dates of efficiency fish releases were not recorded) and the Weitchpec catches in each week were expanded by the results of the respective efficiency tests. Big Bar..catches (1974 and 1975) were not expanded because efficiency tests were not consistently conducted there.

In 1976 the daily catches were expanded using the efficiency test nearest in time.

RESULTS

Daily Catches and Temporal Migration Patterns--Trinity River

Hatchery Steelhead--1974

Four groups of fin-marked steelhead were planted in 1974, all during the period May 3 through May 6 st able 1). Two groups, the Trinity River- and the Washougal-strain fish were released about 8 km (5 miles) downstream from the hatchery. The other two groups, the Trinity brood stock- and the Eel River-strain fish, were released at a weir about 0.5 km (0.3 miles) downstream from the hatchery. The two groups released farthest downstream were captured earlier at both netting stations than the other two groups(see median dates of recapture:/ in Table 3 and Figures 4a and 4b). - One-half the catch occurred on or before this date; one-half on or after it. Dates are calculated separately for the Big Bar and Weitchpec sites. Table 3

Catches of Steelhead in the Trinity River at Big Bar and Weitchpec, 1974-1976

Caught at Caught at Median recapture dates Median recapture dates -Big Bar Weitchpec Days Days Date Mark Strain Number %* Number %? Big Bar elapseCk* Weitchpec elap~eC~'~ 1974 Ad-LV Eel River 103 0.17 3 0.01 5/28/74 22 6/ 7/74 32 Ad-RV Washougal 3,672 5.46 646 0.96 5/15/74 12 5/17/74 14 LV Trinity River 2,510 1.29 198 0.10 5/23/74 21 5/18/74 16 RV Trinity brood 610 0.98 29 0.05 6/ 2/74 27 5/30/74 24 Unmarked (wild) steelhead 2,823 - 2,029 - 5/15/74 - 5/11/74 -

1975 D-LM Trinity River 84 0.50 154 0.91 5/30/75 25 5/31/75 26 D-RM Mad River 781 1.55 613 1.21 5/13/75 8 5/28/75 23 Unmarked (wild) steelhead 3,077 - 4,114 - 5/13/75 - 5/23/75 - 1976 RV Trinity River 1,618 1.64 (yearlings ) Ad-RV Iron Gate 148 0.13 (yearlings ) Ad Washougal 516 2.16 (yearlings) LV Trinity River 393 1.25 (small 2-yr-olds) Ad-LV Iron Gate 109 0.29 (small 2-yr-olds ) LP Trinity River 139 0.65 (large 2-yr-olds) Ad-LP Iron Gate 12 0.12 (large 2-yr-olds) Unmarked (wild) parr 14,848 - Unmarked (wild) smolts 2,833 - Unmarked (wild) steelhead 17,849***-

* % of number originally released, ** Between earliest date of planting and median recapture date. *** Total includes some fish caught that were not classified parr or smolt. n = BIG BAR I = WEITCHPEC Ad - RV WASHOUGAL STRAIN - - 67,200 RELEASED 5/3-6174 - n = BIGBAR - - I = WEITCHPEC - - - - - h ------

I I 11111111 c-. n I I I I I I I I I I I 1 I - UNMARKED ( WILD - - - - -L

J 11111111 I I I 1 I I I I I I I 1 I 1

APRIL I MAY I JUNE igure 5b. Daily Big Bar and Weitchpec fyke net steelhead catches, 1974. (Other 1974 daily catches appear in Figure 5a.) Modes in daily catches of the Washougal- and Trinity-strain fish occurred at Big Bar about 10 days after release, and Weitchpec about two weeks after release. The Eel River- and the Trinity brood stock-strain fish exhibited no discernible modes in daily catches.

Hatcherv Steelhead--1975

Two groups of marked steelhead were released in 1975. Both groups were released at the weir 0.5 km (0.3 miles) below the hatchery.

Mad River-strain steelhead (marked D-RM) first appeared in the Big Bar net May 7 (two days after release) and in the Weitchpec nets May 10 (five days af3er release) (Figure 6).

Trinity-strain steelhead (marked D-LM) first appeared in the Big Bar net May 12 (seven days after release). They first appeared in the Weitchpec nets May 23 (18 days after release) (Figure 6).

The catches (percent of fish released) of Mad River-strain fish were greater at both netting sites, but declined earlier than those of the Trinity River-strain fish. The median recapture data at Big Bar for the Mad River- strain fish was May 13; for the Trinity River-strain fish it was approximately two weeks later (~ay30) (Table 3).

The nets at both Big Bar and Weitchpec were kept out of the water during the period May 15 through May 20, 1975, when the river was too high for sampling. Steelhead catches during periods immediately preceding and following this sampling lapse indicated that during the lapse there may have been considerable movement of both groups of hatchery fish, plus wild fish past the sampling sites (Figure 6). Indeed, it is possible that the peak movement of any or all of the groups occurred during this period.

Hatchery Steelhead--1976

Seven groups (three classes) of marked hatchery steelhead were released in 1976; three strains of yearlings, two strains of nsmallu two-year-olds, ranging from 150 to 203 mrn (6-8 inches) FL and two strains of 711arge1rtwo- year-olds, all at least 203 mrn (8 inches)~~. Each of the above classes included a group of Trinity-strain fish an'iq-a group of Iron Gate-strain fish; the third yearling group was Washougal-strain (Table 1).

The Trinity- and Iron Gate-strain fish of each class were released on the same dates. Trinity-strain fish of each class were captured consistently earlier than the Iron Gate fish of the same class (see median recapture dates, Table 3; and Figures 7a and 7b).

The Washougal-strain yearlings median recapture dates followed the planting date by nine days at Big Bar, and 13 days at Weitchpec we able 3 and Figure 7b). n = BIG BAR I = WEITCHPEC 100 - LV TRINITY RIVER STRAIN - 90 - SMALL TWO YEAR OLDS - - 31,509 RELEASED 4/23/76 - 60 - I = WEITCHPEC - 50 - - 40 - - 30 - - 20 - - 10 - - I -I I. .. - I 1 I I I I I 1 I -I 2 40- Ad - LV IRON GATE STRAIN k 30- SMALL TWO YEAR OLDS 37,221 RELEASED 4/23/ 76 - z 20- - W IO- - - - ILL1 I I. I I 2 0 I I I 1 -I I I I I I I I I I I I I I - L' 0 60- Ad WASHOUGAL STRAIN 'T 50- YEARLINGS - I 0 - - t 40 24,394 RELEASED 4/23/76 - n 30- 20 - - 10 - - I Ill t I I I 11 lrn I I 0 1 lL,S I I I I I I I I I I I I I I I I I -I I 30 - LP TRINITY Rl VER STRAl N 20 - LARGE TWO YEAR OLDS 21,630 RELEASED 41 1 I76 - 10 - - s. -m t I.T, - 0. I I I I I I I I I I I I I I I I I t 30 - - - Ad - LP IRON GATE STRAIN 20 LARGE TWO YEAR OLDS 9,750 RELEASED 41 1 / 76 - 10 - - - n I I - - rh I- - . 0 I I I I I I I I I I I I I I I I . 5 10 15 20 25 j01 5 10 15 20 25 ;II 5 10 15 20 25 30 APRIL MAY JUNE Figure 7b. Daily Big Bar and Weitchpec fyke net steelhead catches, 1976. (Other 1976 daily catches appear in Figures 7a and 7c.)

C - 19 -

Wild Fish

Peak catches of wild fish at Weitchpec occurred May 16 in 1974, and on May 23 and May 26 in 1975 and 1976 (~igures5b, 6 and 7c). 'The Weitchpec median recapture dates a able 3) precisely match the peaks in daily catches in 1975 and 1976. In 1974 the Weitchpec median recapture date (May 11) precedes the peak in daily catches, in spite of the fact that netting began more than a month later in 1974 than in the other two years. This results because 1974 catches also declined earlier than in the other two years. In 1974 5% of the wild steelhead were caught in June, compared to 29% in 1975 and 14% in 1976.

Big Bar daily catches peaked in April in 1975 and 1976 and.on May 16 in 1974. In all years Big Bar catches declined from late May through mid-June. In 1974 and 1975 Big Bar catches swung upward on the last few days of netting, during the third week in June.

In 1976 (the only year parr and smolts were distinguished in the sampling) daily catches of parr peaked in early April at Big Bar. At Weitchpec, few parr were captured at any time, but most were captured during the last week in May and the first week in June. Daily catches of smolts peaked in mid- May at Big Bar, and in late May at Weitchpec.

Fall 1974 Netting Observations in the Trinity River at Weitchpec

To determine if sigr,ificant numbers of the residual hatchery yearlings were leaving the river in the fall, fyke netting at the Weitchpec site in the Trinity River was resumed September 14. The net was fished one day/week from that date through October, five days/week the first two weeks of November, and one day/week through the rest of November.

Seventy juvenile steelhead were captured in 19 days of netting. Only one of the 70 bore a fin-clip identifying it as part of the spring 1974 Trinity Hatchery release; it was a Trinity River strain (LV) individual. The 70 fish averaged 112 mm (4.4 inches) -FL; they ranged in size from 67 to 176 mm (2.6-6.9 inches) FL.

Size at Release and at Recapture

Fish released in 1974 were much smaller than fish released in 1975 and 1976. The mean fork lengths by production group at planting in 1974 ranged from 122.2 to 154.0 mm (4.8-6.1 inches) (~igure8). The two groups of fish released in 1975 (Mad River- and Trinity-strain yearlings) averaged 179 and 192 mrn (7.0 and 7.6 inches) -FLY respectively (Figure 9).

40

3 0 RV TRINITY BROOD fl COMBINED CATCHES AT BIG BAR AND WEITCHPEC

20 MEAN AT PLANTING = 142.8 MM

10

0

301 l\7:RiNITI RIVER

MEAN AT PLANTING = 149.2 MM n = 2122 1

MEAN r_L AT PLANTING = 154.0 MM

1974 3 0 1 Ad - LV EEL AVER

50 100 150 200 250 300 350 FORK LENGTH Figure 8. Comparison of length frequencies at release, and at recapture in downstream fyke nets, of marked hatchery steelhead released in the Trinity River. HATCHERY SAMPLE D - RM MAD RIVER COMBINED CATCHES AT BIG BAR AND WEITCHPEG MEAN a AT PLANTING 178.8 MM

Ad - LP IRON GATE LARGE 2-YEAR-OLDS MEAN AT PLANTI NG = 256.6 MM NO RECAPTURE HISTOGRAM BECAUSE ONLY n = 938 I7 FISH WERE EVER RECAPTURED

LARGE 2- YEAR - OLDS

MEAN FL AT PLANTING = 238.9 MM

RV TRINITY RIVER

MEAN FL AT PLANTING = 198.8 MM

5 0 100 150 200 250 300 350 FORK LENGTH Figure 9. Comparison of length frequencies at release, and at recapture in downstream fyke nets, of marked hatchery steelhead released in the Trinity River. The mean sizes of the three yearling groups and two tfsmalllttwo-year-old groups released in 1476 ranged from 164 to 199 mm (6.5-7.8 inches) FL. The "largety Trinity-strain two-year-olds averaged 239 mm (9.4 incheq FL, and the "largev Iron Gate two-year-olds, 257 mm (10.1 inches) (~igures9 and 10).

L There was little or no disparity between length frequency at release and at recapture in any of the groups containing only fish at least 150 mm (6 inches) FL (the 1975- and 1976-released hatchery fish) (Figures 9 and 10). There was, however, considerable disparity between the length frequencies at release and at recapture in all four groups of hatchery fish released in 1974. Very few fish smaller than 150 mm (6 inches) -FL released in 1974 were recaptured in the nets (~igure8).

The length distributions of wild fish captured at Big Bar in all three years sampled were bimodal, with one peak in the 80-100 mm (3.1-3.9 inch) range and another in the 150-170 mm (5.9-6.7 inch) range (~igure11). The minimum separating the two modes occurred at roughly 130 mm (5.1 inches) FL each year. -

At Big ~ar,most of the unmarked fish netted were less than 130 mm (5.1 inches) FL in 1975 and 1976, but in 1974 relatively few of these smaller fish werrcaptured. At Weitchpec, few fish less than 130 mm (5.1 inches) FL were captured in any year (Table 4).

Table 4

Percentages of Total Unmarked Steelhead Caught That Wereel30 mm -FL Caught at Catch at Year Big Bar Weitchpec

The length frequencies of fish classified in 1976 as either smolts or parr alone were unimodal. The 1976 length frequency distributions of smolts captured at Weitchpec and Big Bar were almost identical, the modes of both distributions being in the 150- to 170-mm (5.9- to 6.7-inch) -FL range. The mode for parr captured in 1976 at Big Bar was between 80 and 100 mm (3.1-3.9 inches) FL, matching the Big Bar mode for smaller fish observed in both 1974 and 197r

In 1976 the parr captured at Weitchpec were larger than parr captured at Big Bar (Figure 11). C] HATCHERY SAMPLE COMBINED CATCHES AT BIG BAR SMALL 2 - YEAR - OLDS

MEAN AT PLANTING = 198.0 MM

Ad - LV IRON GATE SMALL 2- YEAR - OLDS MEAN AT PLANTING = 185.2 MM

1976 Ad WASHOUGAL YEARLINGS t MEAN -FL AT PLANTING = 177.3 MM n = 1220

Ad - RV IRON GATE

MEAN FL AT PLANTING = 164.2 MM

FORK LENGTH Figure 10. Comparison of length frequencies at release, and at recapture in downstream fyke nets, of marked hatchery steelhead released in the Trinity River. 40 CATCH AT BIG BAR 1976 CATCH AT WEITGHPEC - 30- SMOLT

i: 1975 WILD ( PARR AND SMOLTS NOT SEPARATED IN SAMPLING W 301

50 100 150 200 250 300 350 FORK LENGTH Figure 11. Comparison of lengths of unmarked (wild) steelhead caught at Big Bar with those caught at Weitchpec, 1974-1976. Efficiency Test Results and Expanded Catches

Each study year, the proportions of efficiency fish recaptured fluctuated considerably with time. The highest recapture percentages usually occurred during the first two weeks in May (Tables 5-8). Seasonal percentages of Weitchpec-released fish recaptured ranged from 6.2% in 1975 to 1.6% in 1976.

Day-released efficiency fish were recaptured in lower preport.ions than night-released efficiency fish in all study years. The least disparity between recovery percentages of day-released and night-released fish was observed in 1975. This was a relatively high flow year, and though turbidity measurements were not taken in any year, field biologists believed that the water was muddier in 1975 than in the other years of the study.

In 1976 (the only year records of efficiency test results by strain were kept) there were consistent differences among steelhead strains in the percentages recaptured (~ables9 and 10).

Expanded catches appear in Tables 11 and 12.

Klamath River Observations

Steelhead Migration Past Weitchpec, 1974-1976

Steelhead catches in the Klamath River were consistently smaller than those obtained in the Trinity during the three years. The smaller catches there are attributed to the fact the Klamath net could not be fished in the swifter, center parts of the channel because of the river's large size and the movement of boats up and down past the netting site.

Total catches of unmarked (wild plus hatchery) steelhead in 1974, 1975 and 1976 were 281, 944 and 178, respectively.

Because of the relatively small numbers of fish netted, timing of peak migrations past Weitchpec in the three years is not readily apparent in the daily catch data. Consequently, 15-day running averages of the catch were used to help identify these peaks. Results indicate that in both 1974 and 1976, peak downstream movements of juvenile steelhead past Weitchpec occurred about the end of the second week in May. In 1975 the peak appeared to occur about the end of May.

Size of Captured Klamath Migrants

The 1974 and 1975 length distributions of unmarked (wild plus hatchery) steelhead captured in the Klarnath were unimodal. In each year, a pronounced peak occurred in the 150-170 mm (5.9-6.7 inch) range. The 1976 length distribution, by comparison, showed an apparent, but much less distinct mode in the same 150-170 mm (5.9-6.7 inch) range, but also showed a second, more distinct mode in the 80-100 mm (3.1-3.9 inch) range. The minimum separating the two modes in 1976 occurred at about 130 mm (5.1 inches) -FL. Table 5

Results of 1974 Weitchpec Efficiency Tests

Day-released efficiency fish Night-released efficiency fish Day + Night Week Number Recaptured Number Recaptured Number -Recaptured released released Number % released Number % released Number %

TOTALS 10,570 178 1,7 8,503 206 2.4 19,073 384 2.0

Table 6

Results of the 1975 Weitchpec Efficiency Tests

Day-released efficiency fish Night-released efficiency fish Da + Night Week Number Recaptured Number d Reca tured released released Number % released released 6%

TOTALS 7,344 378 5.1 6,637 486 7.3 13,981 864 6.2 Table 7

Results of 1976 Big Bar Efficiency Tests

Day-released efficiency fish Night-released efficiency fish Day t Night

Week Number Reca~tured.L Week Number Reca~turedL Number Reca~tured+ released released Number X released released Number X released Number X

TOTALS 12,975 40 0.3 12,514 85 0.7 25,489 125 0.5 * Estimated Table 8

Results of 1976 Weitchpec Efficiency Tests I Day-released efficiency fish Night-released efficiency fish Day + Night heek Number Reca~tured Week Number Reca~tured Number Recaptured d. .. A released released Number % released released Number % released Number %

TOTALS 11,547 77 0.7 11,919 294 2.5 23,466 371 1.6 Table 9

Night-efficiency Test Results, 1976, Presented by Mark (strain)

Big Bar releases Weitchpec releases Recovered Recovered Recovered Number Big Bar Weitchpec Released Weitchpec Mark released Number % Number % Weitchpec Number %

TOTALS 12,514 8 5 0.7 8 8 0.7 11,919 294 2.5

-- - * Estimated

Table 10

Day-efficiency Test Results, 1976, Presented by Mark (Strain)

Big Bar releases Weitchpec releases Kecovered Kecovered Kecoverea Number Big Bar Weitchpec Released Weitchpec Mark released Number % Number % Weitchpec Number %

------TOTALS 12,9 75 4 0 0.3 66 -0.5 11,547 77 0.7 * Estimated Table ll

Production Fish Released and Recaptured, and Weitchpec Expanded Catches, 1974 and 1975

Weitchpec % (of Number Big Bar Weitchpec expanded number

Mark... - released catch catch catch released) 1974 Unmarked steelhead 2,823 2,029 91,057

------I------Ad-RV Washougal SIX. 67,200 3,672 646 30,024 44.7 LV Trinity R. Str. 195,020 2,510 198 10,662 5.5 RV Trinity R. 62,270 610 29 4,924 7.9 (brood stock str. ) Ad-LV Eel R. St.. 61,000 103 3 193 0.3

TOTALS, marked fish 385,490 6,895 2,905 45,803 11.7 1974

Unmarked steelhead 3,077 4,114 68,290 --____------D-RM Mad R. Str. 50,550 7 81 613 13,313 26.3 D-LM Trinity R. Str. 16,906 84 154 3,728 22.1

TOTALS, marked fish 1975 67,456 865 767 17,041 25.3

Table 12

Expanded Big Bar and Weitchpec Catches, 1976

Expanded % of Expanded % of Big Bar number Weitchpec number Mark Released catch released catch released Unmarked parr Unmarked smolts Unmarked steelhead

Ad Washougal Str. RV Trinity R. Str. LV Trinity R. Str. Ad-RV Iron Gate Str. Ad-LV Iron Gate Str. LP Trinity R. Str. Ad-LP Iron Gate Str.

TOTALS, marked steelhead 335,077 299,774 89.5 80,112 23.9 The percentages of unmarked steelhead captured in the Klamath River in 1974, 1975 and 1976 that were less than 130 mm (5.1 inches) -FL were 15.6% (44 fish), 4.1% (39 fish) and 48.9% (87 fish), respectively.

The length frequencies of fish classified as either parr or smolts alone in 1976 were unimodal. The length mode for parr was between 80 and 100 mm (3.1-3.9 inches) -FLY while that for snolts was between 160-180 mm (6.3-7.1 inches) -FL.

DISCUSSION

Emigration Patterns

Wild Fish

Moffett and Smith (1950) fyke-netted steelhead at Lewiston during the period 1942-1946. They observed movements of 20-50 mm (0.8-2.0 inch) TL fish from May through July, little movement of fish of any size during7he period August through December, and strong movements of 50 to 110 mm (2.0-4.3 inch) FL fish during the period January through May. The peak catches of the~e(~resurnab1~yearling) fish occurred in April.

Their data are not suitable for judgements about the timing of movements of fish which would be considered smolts today; they caught only 30 fish bigger than 130 rnm (5.1 inches) TL during their four years of netting (they indicated that their gear was noFeffective on these larger fish).

Healey (1973) also fyke-netted steelhead at several locations in the Trinity River from 1968 through 1971. He netted at Big Bar in 1968 and 1969. He never netted near Weitchpec.

Like Moffett and Smith, Healey caught 20-50 mm (0.8-2.0 inch) FL fish in May and June, though he caught very few of them (77). His catches~onsisted primarily of fish 50-130 mm (2.0-5.1 inches) FL. He caught fish in this size range in all months from November througr~une,but the peak month was April.

Healey's results differed substantially from those of Moffett and Smith in that Healey successfully netted significant numbers of steelhead greater than 130 mm (5.1 inches) FL. Catches of these larger (presumably two-year- old or older) steelhead aEo peaked in April, but endured somewhat later in the spring than the yearling catches. In May the catches of fish greater than 130 mm (5.1 inches) -FL exceeded the catches of yearling fish. In the 1974-1976 study, fyke netting was conducted only during the months March through June (except for the limited sampling done in the Trinity in Fall 1974). In 1974.and 1975 high and fluctuating flows interfered with netting operations in the Trinity until about May 1. one the less, the 1975 and 1976 observations indicated that the movement of wild steelhead past Big Bar peaked in April, and that most fish moving during this peak period were in the 50-130 mm (2.0-5.1 inch) FL range. The greatest movement of fish over 130 mm (5.1 inches) -FL pastxig Bar in these two years occurred from late April to early May, The proportion of these larger fish in the catch was greatest in May because their movements endured somewhat later than those of the 50-130 mm (2.0-5.1 inch) FL fish. These generalizations are consistent with the data presented by ~Gle~(1973).

Though consistent sampling at Big Bar in 1974 was conducted only after May 1, the catches indicated that the peak fish movements occurred later in 1974 than in the other two years. Catches in 1974 increased from May 2 to a peak on May 16, then fell off rapidly. The lengths of fish in the catch suggest that the difference in timing was caused by an almost complete absence in 1974 of steelhead less than 130 rnrn (5.1 inches) -FL able 13).

Table 13

Proportions of Big Bar May Catch ~130rnm -FL

The 1974-1976 study is distinguished from the earlier studies in that sampling was conducted in both the Trinity and Klamath Rivers at Weitchpec.

Fyke-net catches in the Trinity at Weitchpec peaked between mid- and late May in all three study years. Comparisons of peaks in daily catches and the median dates of capture indicate that fish movements there occurred earlier in 1974 than in the other two years. In 1974 the peak catch occurred May 16; the median capture date was May 11. The peaks in daily catches precisely matched the median dates of capture in 1975 and 1976 (May 23 and May 21, respectively). The differences among median recapture dates resulted primarily from variations in how late the emigrations endured (~igures5b, 6 and 7c, and Table 3).

The timing of wild steelhead movements past Weitchpec in the Trinity during the three-year study approximated those of unmarked (wild plus hatchery) fish in the Klamath. The timing of unmarked steelhead smolt movements in both the Trinity and Klamath Rivers in 1974-76 coincide closely with those reported for other areas (~oyal1972).

Though there were big differences among years in the size composition of fish caught at Big Bar, catches in the Trinity at Weitchpec every year were comprised primarily (90% or more) of fish at least 130 mm (5.1 inches) FL. The Weitchpec sampling was done during years of widely disparate spring- flow conditions. March-June flows were much higher than average in both 1974 and 1975, and much lower than average in 1976 (Table 14). Table 14

Monthly Mean Flows, Trinity River at Hoopa, 1974, 1975 and 1976, vs Means of Monthly Means, 1967-1976

March April May June

1974 14,290 14,750* 5,967 3,337 1975 20,120* 9,242 8,771" 4,683* Means of Monthly Means, 1967-1976 10,841 7,140 4,988 2,611 1976 5,287 4,200 2,760 1,303

* Highest mean for this month since at least 1967.

Apparently, regardless of the age-size composition of juvenile steelhead above Big Bar, the spring emigration past Weitchpec is limited primarily to fish at least 130 mm (5.1 inches) FL. This appears to be the case over a broad range of flows. -

Hatchery Fish

Of the thirteen groups of marked fish released in the Trinity River in the springs of 1974 through 1976, two were released April 1 (the large two-year- olds released in 1976), and the remaining 11 were released each year during the same two-week period from April 23 to May 6.

Some marked fish were captured at the netting sites as soon as two days following planting. Median capture dates, however, ranged from April 19 to June 2 at Big Bar and from May 2 to June 7 at Weitchpec.

Though differing dates and places of release confounded comparisons in many cases (earlier-released fish tended to reach netting sites earlier) there were apparent differences in emigration timing among strains. These are illustrated by differences in the lapses between planting dates and the median capture dates. Overall, these lapses ranged from six to 31 days at Big Bar, and from 13 to 40 days at Weitchpec.

Washougal-strain fish, released only in 1974 and 1976, reached both netting sites sooner than any other yearling group released in those years. Median capture dates in 1974 and 1976 respectively, followed planting dates by nine and 12 days at Big Bar, and 13 and 14 days at Weitchpec. Washougal-strain fish released in 1971 exhibited this same prompt downstream movement (Healey, 1973). In 1976 Iron Gate-strain steelhead in each of three classes (yearlings, "small two-year-oldsl', and "large two-year-oldsly) reached the netting sites later than the comparable groups of Trinity-strain fish (~igures7a and 7b). A comparison of median recapture dates indicates the Iron Gate fish, moved downstream about two weeks later than the Trinity-strain fish.

Though small differences like these in the timing of juvenile fish movements may have an impact on survival rates, no implication of such effect is intended here. It is noteworthy, however, that the percentages captured in the Big Bar nets were inversely correlated (significant at .05 level) with the lapses between planting and median recapture dates (r = 0.56, n = 13).

The Importance of Size at Release

The comparison of length frequencies at release with those of fish captured in the fylce nets (Figures 8-10) strongly indicates that most of the spring- released hatchery steelhead shorter than about 150 mrn (6 inches) -FL failed to emigrate when released.

Haley (1974) in August and September 1974 sampled the Trinity River and some of its tributaries with electrofishing gear and a rod and reel, collecting as many juvenile salmonids as possible. For each fish he caught, he recorded the length, mark (if any), llconditionlr, and the date and location of capture. When Haley encountered a successful sport fisherman he included the fisherman's catch in the sample.

Haley examined 361 unmarked and 52 marked juvenile steelhead. Three of the marked fish were marked Ad (only) and were presumably (~d-RV-or Ad-LV-marked fish with regenerated or incompletely removed ventral fins. Haley (1974) wrote: "Most ofthe marked fish were caught near Lewiston, while most of the unmarked steelhead were caught between Grass Valley Creek and Weitchpecrl.

Haley did not imply a relationship between his catches and sizes of the fish when released. However, his data, along with our fyke net data, support the assertion that the smaller fish have a greater tendency to residualize (Table 15). Table 15

Comparison of Numbers of Steelhead Caught in August-September 1974 With Size at Release and With Spring Net Catches

Mark (headings in order of increasing size at release) Ad-LV RV LV Ad-RV

Captured Aug.-Sept. 1974 23 10 15 1 Recapture rate*, Aug.-Sept. 1974 37.7 16.1 7.7 1.5 catches (X 10-5) Recapture rate* Big Bar net 0.17 0.98 1.29 5.46 Recapture rate* Weitchpec nets 0.01 0.05 0.10 0.96 Average -FL at release (mm) 122 143 149 154

* ~atch/numberreleased.

HaleyTs observations do not directly relate to judgements about the numbers of these fish successfully emigrating from the Trinity during the fall or winter following planting. The small number of steelhead (70 wild and one marked steelhead) caught during the 1974 fall fyke-netting indicated that few were emigrating then. Studies elsewhere have resulted in the conclusions that small fish tend to residualize, and such residualization generally results in lower overall adult return rates (Royal1972).

Expanded Catches as Population Estimates

When the 1974-1976 efficiency tests were designed it was presumed that the test fish, once released, would immediately move downstream the 274 m (300 yards) to the nets. Accepting the expanded catches as valid point estimates of the populations requires that this be approximately true.

Only in 1976 were efficiency tests consistently conducted at both Big Bar and Weitchpec, hence the emphasis of this discussion is on the 1976 results.

For four of the seven 1976 production groups the expansion of catches produces numbers reaching Big Bar greater than the numbers originally released.

At Big Bar the 0.7% overall recapture rate of night-released efficiency fish is less than the 0.8% recaptured ofthe same strains, released approxi- mately 48 km (30 miles) upstream from Big Bar.

A total of 516 Ad-marked (~ashougalstrain, lrproductionlr fish) were captured at Big Bar. This represents 2.16% of the 24,394 released in 1976. If the recapture rate of production fish is representative of numbers of these fish moving past the net, average net efficiency at Big Bar could be as low as 2.16% only if there were no significant residualization or mortality of these Washougal-strain fish prior to the time they reached Big Bar. Logic dictates that the real net efficiency at Big Bar was considerably greater than that indicated by the efficiency tests. Estimating emigration by directly expanding daily catches using the efficiency test results would produce an error for one group (the Washougal-strain fish) of at least 89%.

Such systematic error would result if significantly less than 100% of the Big Bar released fish did not move the 274 m (300 yards) downstream after they were released, or if the efficiency fish were released in a manner which would cause them to miss the net at a rate greater than that of the emigrating production fish.

The evidence for systematic error is not so clear-cut for the Weitchpec sampling, since expanding the catches produces numbers which are always smaller than the numbers of production fish originally released. But the values for expanded Weitchpec catches must also be extremely sensitive to the behavior of the efficiency fish. The Weitchpec expanded catches, as those at Big Bar, are of questionable value as point estimates.

Expanded Catches as Indices of Emigration

If one assumes that the systematic error produced by expanding the daily catches is approximately the same at either station for all groups captured, the numbers produced (Tables 11 and 12) may be regarded as indices of numbers reaching the sampling sites, useful for comparing the different groups. Further (if the assumption is true) these numbers, divided by the original numbers released, produce proportions which may be regarded as indices of emigration rates.

Perhaps the most disconcerting aspect of this approach is the lack of proportionality between the 1976 Big Bar and Weitchpec indices. The ratios of Big Bar:Weitchpec indices in 1976 ranged from 14,7:1 for the large two- year-old Trinity-strain fish, to 1.0:1 for the Iron Gate-strain yearlings.

It is impossible to favor the results of one station over another on the basis of sampling error alone. However the catches at Big Bar would be more apt to reflect rrinstreamrrfish movements (distinguished from active emigration) than those at Weitchpec. This may partially explain the lack of proportionality, and may be justification for favoring the Weitchpec indices over those at Big Bar as estimators of successful emigration rates.

Estimated Limits of Wild Fish Populations

The difficulties in making point estimates of marked fish populations at the netting sites also apply to estimates of wild fish populations. If however, the sampling gear was equally effective for wild and hatchery fish of the same size, the catches provide a means of estimating the percentages of spring smolt production attributable to the hatchery each season (Table 16). Because the numbers of hatchery fish reaching the sampling sites must be smaller than the numbers originally released, the logical upper limits (Table 16) of the wild populations of steelhead 2130 mm (5.1 inches) FL reaching the sampl- ing sites may be calculated solving the equalities suchFhat:

The maximum wild population <

marked fish1130 mm FL released x unmarked fish2130 mm FL captured marked fish2130 mm FL recaptured

For example, at Weitchpec, 1974:

The maximum wild populationc241,827 x 1,894 2,905

The maximum wild populationc157,666

The resulting estimates indicate that from 1974 through 1976 the Trinity system upstream from Big Bar produced from about 1/4 to 1/2 of the wild, spring-emigrating smolts produced in the whole Trinity system.

Table 16

Hatchery Releases, Catches, and Estimated Upper Limits of Populations Reaching the Netting Sites, for Wild Steelhead2130 mm -FL Hatchery Big Bar fish Big Bar catches wild yYear released mar ed opulation

- Hatchery Weitchpec fish Weitchpec catches wild Year released marked unmarked % marked population REFERENCES

Haley, Richard (unpublished). Location of marked steelhead in the Trinity River: September, 1974. [calif. Dep. Water Res . Contract Services : Fish and Wildlife Evaluation Project, Red Bluff. Ca. (office files, 1974) 8 p.] . Healey, Terrance B., Jr. 1973. Studies of steelhead and salmon emigration in the Trinity River. Calif. Dep. Fish and Game. Anad. Fish. Admin. Rep. 73-1. 37 p.

Hubbell, Paul M. (unpublished). Program to identify and correct salmon and steelhead problems in the Trinity River Basin. Calif. Dep. Fish and Game Anad. Fish. Branch. (A report to the Trinity River Basin Fish and Wildlife Task Force, August 1973.) 70 p.

Moffett, James W., and Stanford H. Smith. 1950. Biological investigations of the fishery resources of the Trinity River, California. U. S. Fish and Wildlife Service Spec. Sci. Rept.--Fish, (12): 71 p.

Royal, Loyd A. 1972. An examination of the anadromous trout program of the Washington State Game Department. Wash. Dep. Game, 176 p. + appendixes.