CHAPTER IV. RUN-SIZE, ANGLER HARVEST, AND SPAWNER ESCAPEMENT OF CHINOOK AND COHO SALMON IN THE TRINITY RIVER BASIN (Continued).
RESULTS AND DISCUSSION
We captured 150 spring chinook salmon during the first night of trapping at JCW, indicating the run was well underway on 4 June, when trapping began. Over 300 chinook were trapped the first and third weeks of the survey, but catches declined by the fifth week (Table 1). The spring run at JCW appeared to peak during JW 25 (18-24 June), then catches generally declined through the end of the run in JW 37 (10-16 Sept.) (Figure 3). We trapped 1,512 spring chinook salmon at JCW during the 1989-90 season.
The high initial catches at JCW during the first week of trapping may have been due to reaction of the spring chinook to a sudden decrease in discharge below Lewiston Dam from approximately 56.7 m/s that occurred through 23 May, to 28.4 m/s through 29 May, and down to 9.9 m/s in June, when trapping began. Spring chinook in the Trinity River apparently migrate faster in response to lower flows or coincident higher water temperatures and decrease their migration rate during higher flows resulting in generally lower water temperatures (Schaffter, Heubach and Hubbell, 1979, Heubach 1984).
Only 63 spring chinook were trapped at WCW, and represent fish that remained in the Klamath or lower Trinity rivers during the summer (Table 1), since they had the darkened coloration which indicated they had been in freshwater for some time.
The size of spring chinook trapped at JCW ranged from 41 to 92 cm FL, averaging 67.6 cm FL, while those trapped at WCW ranged from 44 to 83 cm FL and averaged 69.5 cm FL (Table 2). The difference in the mean size of spring chinook trapped at the two weirs was not statistically significant (t=1.8, p=.09).
The nadir in the length frequency separating grilse and adult spring chinook trapped at JCW appeared to be 48 cm FL (Figure 4). Too few grilse were trapped at WCW to distinguish the nadir. However, 48 cm FL is the size separating known-age, hatchery-marked (Ad+CWT) grilse and adult spring chinook that entered TRH. For the 1989-90 season, we considered spring chinook in the Trinity River basin <48 cm FL to be grilse, while adults were >48 cm FL. During the 1989-90 season, only 28 or 1.6% of the spring chinook trapped at JCW and three (4.7%) of those trapped at WCW were grilse (Table 2). Too few fish were tagged at WCW to test for differences between sites in the ratio of grilse to adults.
Tagging operations in the lower Klamath River and at WCW did not begin until the spring run was essentially past JCW. Consequently, no tagged fish from these sites were recaptured at JCW during the spring run of 1989.
We trapped 198 hatchery-marked (Ad+CWT) spring chinook at JCW in 1989, which comprised 13.1% of all the fish caught there. The mean FL of the hatchery-marked fish was 68.1 cm, similar to the mean for all spring chinook (Table 2).
Only five (7.9%) of the 63 spring chinook trapped at WCW during the 1989-90 season were hatchery-marked fish, and all were adults, as at JCW (Table 2).
Forty-eight hatchery-marked spring chinook, representing four CWT groups, were spaghetti-tagged at JCW and subsequently recovered either dead in the spawning survey, or at TRH. All but seven of them were fish from the 1985 or 1986 BYs which had been released as yearlings (Table 3). Two fish that had shed their CWT were also recovered.
Two hatchery-marked spring chinook, which were spaghetti-tagged at WCW and subsequently recovered in the spawner survey, were from the 1986 BY and had been released as yearlings (Table 3).
Two hundred seventeen (14.4%) of the spring chinook trapped at JCW had gill-net scars. These fish ranged in size from 53 to 82 cm FL and averaged 67.2 cm FL, similar to the average for all spring chinook trapped at JCW (67.6 cm).
We attempted to evaluate the tagging mortality rates of gill-net scarred and non-gill-net-scarred spring chinook to determine if the added stress of the trapping and tagging process affected the survival of gill-net scarred fish. We recovered the carcasses of 6.7% (14/207) of the gill-net scarred and 3.0% (38/1,259) of the non-gill-net-scarred spring chinook tagged at JCW during the 1989-90 season. The difference in the carcass recovery rates of gill-net scarred and non-gill-net-scarred fish was statistically significant (X2=4.1, p=0.04), and may imply that the added stress of the trapping and tagging process adversely affected the survival of spring chinook which had previously encountered a gill net.
(Table 2) (Figure 4) (Table 3)
The recovery rate at TRH of effectively tagged, gill-net scarred (18.6%) and non-gill-net-scarred (18.2%) spring chinook was essentially the same, after correcting for initial tagging mortality. Therefore, the survival of gill-net scarred spring chinook salmon after the initial tagging mortality, was similar to non-gill-net-scarred fish in 1989.
Seventy-four (4.9%) of the spring chinook trapped at JCW had hook scars, 30 (2.0%) were healed scars indicating they were from the ocean fishery, and 44 (2.9%) were fresh scars probably acquired in the freshwater fishery. Spring chinook with ocean hook scars averaged 70.4 cm FL, and those with freshwater hook scars averaged 69.8 cm FL, both similar to the mean Fl of all spring chinook trapped at JCW (67.6 cm FL).
The 1989 fall chinook run appeared to start at WCW on 30 August (JW 35). Fall chinook catches increased gradually each week, peaked JW 38 (17-23 Sept.), and gradually decreased through JW 42 (15-21 Oct.), when the weir was washed out (Table 1) (Figure 3). We trapped 1,392 fall chinook at WCW during the 1989-90 season.
The fall run began at JCW during JW 38, three weeks after it began at WCW. Catches of fall chinook gradually increased each week and peaked JW 41 (7-14 Oct.), again, three weeks after the peak at WCW (Figure 3), then decreased substantially during JW 42. When we resumed trapping operations at JCW during JW 45 (5-11 Nov.), after the late October storms, the major portion of the fall run had passed the weir site (Figure 3). The last fall chinook was trapped at JCW on December 12 (JW 49), about two weeks before the weir was removed for the season. We trapped 541 fall chinook at JCW during the 1989-90 season (Table 1).
Fall chinook trapped at WCW ranged in size from 40 to 88 cm FL and averaged 65.4 cm FL (Table 4). Fall chinook captured at JCW ranged from 40 to 111 cm FL and averaged 65.9 cm FL, essentially the same as at WCW. The size separating grilse and adults was 52 cm FL at both weirs and TRH (Figure 5). Therefore, this season, we consider all fall chinook <52 cm FL to be grilse, and those >52 cm FL to be adults. Grilse comprised 6.5% (90/1,392) of the fall chinook trapped at WCW, but only 3.1% (17/541) of those trapped at JCW. However, the difference in the composition of grilse and adult fall chinook at the two weirs was not statistically significant (X2=1.09, p=0.30).
Five fall chinook tagged by other CDFG projects at two locations in the lower Klamath River were recaptured at WCW. Two fish tagged at the Klamath River mouth were recaptured 12 d and 13 d after tagging. Three fish tagged at river km 5.1 were at liberty from 7 to 10 d, averaging 8 d. The mean migration rate for all five fish was 13.8 km/d.
Four fall chinook tagged at Klamath River km 5.1 were recaptured at JCW. They had been at liberty for 15 d to 30 d, averaging 25 d, for a mean migration rate of 7.7 km/d.
Twenty-three fall chinook tagged at WCW were recaptured at JCW. These fish took from 10 d to 35 d to migrate to JCW, averaging 21 d, for a mean migration rate of 6.9 km/d. The mean number of days it took for WCW-tagged fall chinook to migrate to JCW agrees with the fall run beginning and peaking at JCW three weeks after it began and peaked at WCW.
Ninety-five (6.8%) of the fall chinook trapped at WCW were hatchery-marked fish (Ad+CWT), whereas at JCW, 47 (8.6%) of the fall run were marked (Table 4). The difference in the proportion of hatchery-marked chinook between the two sampling sites was not statistically significant (X2=0.89, p=0.35). The mean FLs of hatchery-marked fall chinook were 65.2 cm and 66.2 cm at WCW and JCW, respectively, similar to the average size for all fish trapped at the respective trapping sites (Table 4).
Coded-wire tags were recovered from 30 TRH-produced chinook salmon trapped at WCW, indicating they were from two release groups of yearling fall chinook (Table 3). In addition, three chinook were recovered that had shed their CWT.
Coded-wire tags were recovered from 26 fish trapped at the JCW Weir, which indicated they were from one smolt and three different yearling release groups of TRH-produced chinook salmon (Table 3). An additional hatchery-marked chinook had shed its CWT.
At both WCW and JCW, exactly 15.3% of the fall chinook we trapped had gill-net scars. These fish ranged from 46 cm to 84 cm FL at WCW, averaging 63.4 cm FL, and ranged from 57 cm to 85 cm FL at JCW, averaging 68.6 cm FL.
One hundred twenty-one (8.7%) of the fall chinook trapped at WCW had hook scars, 60 (4.3%) were fresh scars received in the freshwater fishery, and 61 (4.4%) were healed scars acquired in the ocean fishery. Forty-nine (9.1%) of the fall chinook trapped at JCW had hook scars, 37 (6.8%) were of freshwater origin, and 12 (2.3%) were of ocean origin. In contrast, only 2% of the spring chinook trapped at JCW had ocean hook scars, and only 2.9% of them had freshwater hook scars.
We trapped the first coho at WCW on 25 September 1989 (JW 39). The coho run at WCW increased the next week and appeared to peak during JW 41 (8-14 Oct.) (Table 5). The coho run still appeared strong at WCW when the weir was washed-out and damaged by the late October storms (JW 43) (Figure 6). We trapped 471 coho at WCW during the 1989-90 season.
The first coho was trapped at JCW on 10 October (JW 41), approximately two weeks after the coho run appeared at WCW. The number of coho trapped increased the next week and continued to increase after the two week hiatus in trapping in late October (JW 43 & 44). The coho run at JCW peaked during JW 46 (12-18 Nov.) and declined steadily thereafter (Figure 6). The last coho was trapped at JCW on 12 December 1989, approximately a week before we removed the weir for the season. We trapped 660 coho at JCW during the 1989-90 season (Table 5).
Coho trapped at WCW ranged in size from 48 cm to 76 cm FL, for a mean of 65.4 cm FL. Coho trapped at JCW were similar to those trapped at WCW, ranging in size from 52 cm to 78 cm FL, for an average of 66.0 cm FL (Table 6).
We used length data from hatchery-marked (Ad+CWT) coho entering TRH to establish the size separating grilse from adults for all fish as 46 cm (Figure 7). Therefore, in this report all coho <46 cm FL are considered grilse, whereas larger coho are adults.
We did not trap grilse coho at either weir. Possible explanations are that there were few coho grilse in the 1989 run, or small coho did not enter the trap. We do not believe the conduit spacing on the weir or trap allowed small coho to escape as we trapped a number of salmonids as small as 40 cm FL.
No coho tagged in the lower Klamath River were recaptured at WCW, but one was recaptured at JCW. It had been at liberty for 36 d. Three coho tagged at WCW were recaptured at JCW. The mean liberty time was 18 d for a mean migration rate of 4.8 km/d.
Hatchery-marked (Ad+CWT) fish comprised 24% and 9.1% of the coho trapped at WCW and JCW, respectively (Table 6). Hatchery-marked coho trapped at both weirs ranged from 59 to 72 cm FL for similar mean sizes of 61.1 cm FL (WCW) and 66.2 cm FL (JCW) (Table 6).
Assuming there were no stray coho trapped at either weir, all of these hatchery-marked fish were coho of the 1986 BY released from TRH in March, 1988. We recovered 11 of the hatchery-marked coho tagged at WCW and 29 of those tagged at JCW (Table 3).
(Table 5) (Figure 6) (Table 6) (Figure 7)
Gill-net scars were observed on 11.6% and 3.5% of the coho trapped at WCW and JCW, respectively. We cannot explain why the proportion of gill-net scarred coho was so much lower at JCW than at WCW (X2=27, p<0.01). Gill-net scarred coho from both weirs ranged from 60 to 76 cm FL, for a mean of 67.9 cm FL, which appeared to be slightly larger than the unscarred coho trapped at either site (Table 6).
Hook scarred fish comprised 8.9% of the coho trapped at WCW and 4.1% of the coho trapped at JCW. Fish with hook scars of ocean origin comprised 2.6% of all coho trapped at WCW and 1.5% of those trapped at JCW, and 6.3% and 2.6% of the fish from each site, respectively, had freshwater hook scars.
