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ANNUAL RUN-SIZE, HARVEST AND SPAWNER ESCAPEMENT ESTIMATES FOR TRINITY RIVER BASIN CHINOOK AND COHO SALMON AND STEELHEAD (Continued)

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RESULTS AND DISCUSSION

Trapping and Tagging

Spring-run Chinook Salmon

Run Timing. A few spring chinook salmon were mixed with fall-run fish but did not occur in significant numbers when we began trapping operations at WCW on 24 August 1990. Therefore, in this report we assume that no spring chinook were trapped at WCW during the 1990-91 season.

We captured two spring chinook the first week (21-27 May 1990, JW 21) of trapping at JCW, suggesting the run was just getting underway there. The weir was temporarily removed 28 May through 3 June, because of storms, and we did not resume trapping until 7 June 1990 (JW 23). From that week, the spring run increased rapidly and peaked 18-24 June and 9-15 July 1990 (JWs 25 and 28). Catches then generally declined through 13-19 August (JW 33), and then increased slightly through 10-16 September 1990 (JW 37), which we believe was the last week of the spring run (Figure 3). We trapped 1,160 spring chinook at JCW during the 1990-91 season (Table 1).

FIGURE 3. Average number of fall-run chinook salmon trapped per night each Julian week at Willow Creek Weir, and average number of spring- and fall-run chinook salmon trapped per night each Julian week at Junction City Weir in the Trinity River during the 1990-91 season.

TABLE 1. Weekly summary of spring-run and fall-run chinook salmon trapped in the Trinity River at Willow Creek and Junction City weirs during the 1990-91 season

Size of Trapped Fish. Spring chinook trapped at JCW averaged 68.7 cm FL, similar to that in 1989 (Heubach et al. 1992) (Table 2). The nadir in the fork lengths separating grilse and adult spring chinook at JCW was 54 cm, the same as for spring chinook that entered TRH (Figure 4). Therefore, during the 1990-91 season we considered spring chinook in the Trinity River basin <54 cm FL to be grilse, while adults were >54 cm FL. During the 1990-91 season, only 48 (4.1%) of the spring chinook trapped at JCW were grilse (Table 2), which was similar to the proportion of spring chinook grilse (4.1%, 66/1,606) in the TRH sample. The low proportion of grilse is typical of the upper Trinity River basin spring run (Heubach 1984a, 1984b; Heubach et al. 1992).

Incidence of Tags and Hatchery Marks. None of the fish tagged in the lower Klamath River were recaptured at the JCW during the spring run. However, two chinook tagged at WCW were recaptured during the spring run. For this report, we allocate these fish to totals for fall-run chinook at WCW but consider them spring-run chinook at JCW. The reason for classifying these fish differently at the two weirs is simply to maintain a date separating spring and fall chinook runs at the weirs. Except for hatchery-marked (Ad+CWT) fish that are tagged at a weir and subsequently recaptured so the tag can be recovered and decoded, as occurred with these two fish, it is impractical, if not impossible to distinguish every chinook as either a spring-run or fall-run chinook.

We trapped 146 hatchery-marked (Ad+CWT) spring chinook (12.6% of those trapped) at JCW (Table 2). The mean FL of the hatchery- marked spring chinook was not significantly different than that of the unmarked spring chinook (Table 3).

Forty-nine of the 146 hatchery-marked (Ad+CWT) spring chinook which were spaghetti tagged at JCW were subsequently recovered either dead as tagging mortalities, in the spawner survey, or at TRH. Seventy-five percent of the double-marked fish (Hatchery- and Project-marked) we recovered were from the 1986 brood year (BY) and had been released at TRH as yearlings (Table 4).

Incidence of Gill-net and Hook Scars. We observed 156 (13.4%) of the spring chinook at JCW with gill-net scars. The FL of gill-net scarred spring chinook was not significantly different than the non-gill-net scarred fish (Table 3).

Five of 23 (21.7%) of the Project-tagged spring chinook recovered dead had gill-net scars compared to 151 of 1,132 (13.3%) fish that we originally tagged. Although the difference was not statistically significant (X2 =0.92, p>0.60), it follows the observation in 1989 when the tagging mortality rate was higher for gill-net scarred than non-gill-net scarred spring chinook (Heubach et al. 1992). After correcting for tagging mortality, 49 of 146 (33.5%) of the gill-net scarred spring chinook were recovered at TRH while, 391 of 963 (40.6%) of the non-gill-net scarred chinook were recovered at TRH. Again, while not statistically significant (X2 =2.3, p=0.12), it suggests that a slightly greater mortality of gill-net scarred spring chinook than the non-gill-net scarred fish, among those fish that were Project-tagged at the weirs and recovered at TRH.

TABLE 2. Fork lengths of spring-run chinook salmon trapped and tagged in the Trinity River at Junction City Weir and recovered at Trinity River Hatchery during the 1990-91 season

FIGURE 4. Fork lengths of spring-run chinook salmon trapped in the Trinity River at Junction City Weir, and that entered Trinity River Hatchery during the 1990-91 season

TABLE 3. Size differences between marked or scarred vs. Unmarked or unscarred groups of spring- and fall-run chinook and coho salmon, and fall-run steelhead trapped in the Trinity River at Willow Crek and Junction City weirs during the 1990-91 season.

TABLE 4. Release and recovery data for Trinity River Hatchery-produced, coded-wire-tagged chinook salmon that were trapped in the Trinity River at Willow Creek and Junction City weirs, and recovered on spawning surveys or at Trinity River Hatchery during the 1990-91 season.

Eighty-one (7.0%) of the spring chinook trapped at JCW were hook scarred, 39 were healed scars indicating they were from the ocean fishery, and 42 were fresh scars probably acquired in the freshwater fishery. The mean FL of the combined ocean and freshwater hook-scarred chinook was essentially the same as the non-hook-scarred fish (Table 3).

Fall-run Chinook Salmon

Run Timing. All chinook salmon trapped at WCW during the 1990-91 season were considered fall chinook, although there were a few dark-colored fish caught during the first full week of trapping that were probably spring-run fish. From the first full week of trapping, 27 August - 2 September 1990 (JW 35), fall chinook salmon catches increased and peaked 10-16 September (JW 37) (Figure 3). The run then decreased and fluctuated sporadically to a second, smaller peak 29 October - 4 November (JW 44). Thereafter the run decreased each week and the last fall chinook was trapped 4 December (JW 49), suggesting the fall run was over in the lower Trinity River when we removed the weir. We trapped 536 fall chinook at WCW during the 1990-91 season (Table 1).

The fall run began at JCW 17-23 September 1990 (JW 38), three weeks after it began at WCW. The numbers of fall chinook trapped at JCW increased each week through 1-7 October (JW 40), decreased slightly the next week, and peaked 22-28 October (JW 43), six weeks after the peak at WCW (Figure 3). The numbers trapped each week decreased substantially thereafter and we trapped the last fall chinook 30 November (JW 48), two weeks before the weir was removed for the season. We trapped 608 fall chinook at JCW in 1990 (Table 1).

Size of Fish Trapped. The ranges and mean FL of fall chinook trapped at WCW and JCW were essentially the same (t=0.47, p>0.5) (Table 5).

The size separating grilse and adult fall chinook was 53 cm FL at both weirs and TRH (Figure 5). Therefore, this season, we consider all fall chinook <53 cm FL to be grilse and those >53 cm FL are considered adults. Grilse composed 6.3% (34/536) and 9.5% (58/608) of the fall chinook trapped at WCW and JCW, respectively, while they were 21.6% (250/1,158) of the sample at TRH (Figure 5). The difference in the proportions of grilse and adult fall chinook trapped at the two weirs was not statistically significant (X2 =3.5, p>0.05). However, the proportions of grilse and adult fall chinook in both the WCW and JCW samples were significantly different than in the TRH sample (p<0.01).

TABLE 5. Fork lengths of fall-run chinook salmon trapped and tagged in the Trinity River at Willow Creek and Junction City weirs, and recovered at Trinity River Hatchery during the 1990-91 season

FIGURE 5. Fork lengths of fall-run chinook salmon trapped in the Trinity River at Willow Creek and Junction City weirs, and that entered Trinity River Hatchery during the 1990-91 season

Incidence of Tags and Hatchery Marks. We recaptured two fall chinook salmon tagged in the lower Klamath River at WCW. However, only one tag number was legible. The one identifiable fall chinook was recaptured at WCW 58 d after it was tagged in the lower Klamath River, for a mean migration rate of 2.0 km/d. No Klamath River-tagged fish were recaptured at JCW.

Thirty-nine fall chinook tagged at WCW were recaptured at JCW during the fall run (after 15 September 1990). These fish took from 15 to 48 d to migrate to JCW, with a mean of 29 d, for a mean migration rate of 3.0 km/d. The mean number of days it took for fall chinook tagged at WCW to migrate to JCW suggests the fall run began at JCW four weeks after it began at WCW. However data on average catch/night/wk suggests the peak of the fall run at JCW (JW 43) was six weeks after the peak at Willow Creek (JW 37). In 1989 the mean migration rate of fall chinook tagged at WCW and recaptured at JCW was three weeks (Heubach et al. 1992). The reason for the apparent difference in the migration rate in the two years is not known, although in 1990 there were no storm events, as there were in 1989.

Thirty-two (6.0%) and 40 (6.6%) of the fall chinook trapped at WCW and JCW, respectively, were hatchery-marked (Ad+CWT) fish (Table 5). At both weirs the mean FL of the hatchery-marked fall chinook were slightly smaller than the unmarked chinook although the differences were not statistically significant (p>0.30) (Table 3).

Five of the 32 hatchery-marked (Ad+CWT) fall chinook which were spaghetti-tagged at WCW were subsequently recovered either dead as tagging mortalities, in the spawner survey, or at TRH. These fish were from the 1986 and 1987 BY's and had been released at TRH as yearlings (Table 4).

Fourteen of the 40 hatchery-marked (Ad+CWT) fall chinook which were spaghetti-tagged at JCW were similarly recovered. All of them were from the 1986 and 1987 BY's, nine had been released as yearlings and three as smolts, all at TRH (Table 4).

Incidence of Gill-net and Hook Scars. Gill-net scars were observed on 19.6% and 7.5% of the fall chinook trapped at WCW and JCW, respectively. At both weirs, the mean FL of the gill-net

scarred fall chinook was larger than the non-gill-net scarred fish, although the differences were not statistically significant (Table 3).

Seventy-three (13.6%) of the fall chinook trapped at WCW had hook scars. Fifty-five were fish that were hook scarred in the freshwater fishery, while the remainder were of ocean origin. Hook scars were observed on 58 (9.5%) of the fall chinook trapped at WCW. Twenty-four were of freshwater origin, and 34 of ocean origin. At both weirs, the mean FLs of all hook scarred and non-hook scarred fish were statistically similar (Table 3).

Coho Salmon

Run Timing. The first two coho were trapped at WCW 18 September 1990 (JW 38). The catches increased sporadically through 15-21 October (JW 42), decreased the next week and then peaked 29 October-4 November (JW 44) (Figure 6). The numbers of coho trapped decreased dramatically 5-11 November (JW 45), and more slowly thereafter. We trapped the last coho at WCW 7 December 1990 (JW 49). We trapped 271 coho at WCW during the 1990-91 season (Table 6).

The first coho was trapped at JCW 4 October 1990 (JW 40), approximately two weeks after coho initially appeared at WCW. The number of coho trapped per week increased rapidly and peaked 5-11 November (JW 45), one week after the peak at WCW (Figure 6). We continued to trap coho through the last week of operations at JCW (13 December 1990), indicating the coho run had not ended there when we removed the weir. We trapped 160 coho at JCW during the 1990-91 season (Table 6).

Size of Fish Trapped. The mean FLs of coho trapped at the WCW and JCW were statistically similar (t=0.37, p>0.50) (Table 7). The size separating grilse and adult coho is based entirely on the coho that entered TRH this year, because only one coho grilse was trapped at the two weirs. The nadir separating grilse and adult coho that entered TRH was 45 cm FL (Figure 7). Therefore, in this report, all coho <45 cm FL are considered grilse, whereas larger coho are considered adults.

Only one coho grilse was trapped at the weirs this year, and last year, no grilse were trapped (Heubach et al. 1992). It appears the weir panel spacing (5.4 cm) is effective for salmon and steelhead >50 cm, but efficiency decreases rapidly for smaller fish. Apparently, salmon and steelhead <45.0 cm FL can pass through the weir.

Incidence of Tags and Hatchery Marks. None of the coho tagged in the lower Klamath River were recaptured at either weir. Twelve coho tagged at WCW were recaptured at JCW. Their mean migration time was 27 d, for a mean migration rate of 3.2 km/d, which appears to be slower than the pace observed in 1990 (Heubach et al. 1992).

FIGURE 6. Average numbers of coho salmon and steelhead trapped per night each Julian week in the Trinity River at the Willow Creek and Junction City weirs during the 1990-91 season.

TABLE 6. Weekly summary of coho salmon trapped and tagged in the Trinity River at Willow Creek and Junction City weirs during the 1990-91 season.

TABLE 7. Fork lengths of coho salmon trapped in the Trinity River at Willow Creek and Junction City weirs, and recovered at Trinity River Hatchery during the 1990-91 season.

FIGURE 7. Fork lengths of choh salmon trapped in the Trinity River at Willow Creek and Junction City weirs, and that entered Trinity River Hatchery during the 1990-91 season.

Only two coho that appeared to have adipose fin clips were trapped at WCW and none at JCW (Table 7). No coded-wire tags were found in these fish or in the three coho entering TRH that appeared to have adipose fin clips. Therefore, we conclude that no hatchery-marked coho (Ad+CWT) produced at TRH were returning this year. The fish that appeared to be marked (Ad) probably had a natural deformity, because no hatchery-marked coho were expected to return to TRH this year (no 1987 or 1988 BY coho were marked and released at TRH).

Incidence of Gill-net and Hook Scars. Gill-net scars were observed on 6.6% and 2% of the coho trapped at WCW and JCW, respectively. At both weirs, the gill-net scarred fish were slightly larger than the non-gill-net scarred coho, but the differences were not statistically significant (Table 3).

We observed hook scars on 3.7% and 2% of the coho trapped at WCW and JCW, respectively (Table 3). Collectively, ten of the hook scars appeared fresh. The mean FLs of the hook-scarred coho trapped at WCW and JCW were not statistically different from the non-hook-scarred coho observed at their respective weirs (Table 3).

Fall-run Steelhead

Run Timing. Steelhead were trapped the first full week of operations at WCW and every week thereafter. The largest steelhead catches occurred 15-21 October (JW 42) through 29 October - 4 November (JW 44) (Figure 6). The steelhead catch increased slightly during the last week of trapping at WCW, suggesting that the run was not over when we removed the weir. We trapped 325 steelhead at WCW during the 1990-91 season (Table 8).

We trapped the first steelhead at JCW 18 June 1990 (JW 23) and continued to trap an occasional steelhead throughout the summer and early fall (Figure 6). The largest steelhead catches occurred from 24-30 September (JW 39) through 19-25 November (JW 47). As at WCW, we also trapped a relatively large number of steelhead during the last week of operations, indicating the steelhead run was not over at JCW when the weir was removed. We trapped 138 steelhead at JCW during the 1990-91 season (Table 8).

With the exception of the nine steelhead trapped from 18 June through 20 September at Junction City, which we believe were spring-run steelhead, the seasonal catch patterns for fall-run steelhead and coho were strikingly similar at both weirs (Figure 5).

Size of Fish Trapped. The mean FL of steelhead trapped at WCW was slightly larger than that at JCW, but the difference was not statistically significant (t=0.69, p=0.50) (Table 9). The combined mean FL of all steelhead trapped was 62.4 cm. No half-pounder steelhead (< 41 cm FL) were trapped at either weir during the 1990-91 season, and only three half-pounder steelhead were seen at TRH (Figure 8). Apparently, steelhead <50 cm FL, are passing through the weir, as is the case for salmon.

TABLE 8. Weekly summary of fall-run steelhead trapped in the Trinity River at Willow Creek and Junction City weirs during the 1990-91 season.

TABLE 9. Fork lengths of fall-run steelhead trapped and tagged in the Trinity River at Willow Creek and Junction City weirs, and recovered at Trinity River Hatchery during the 1990-91 season.

Incidence of Tags and Hatchery Marks. None of the steelhead trapped at either weir were fin-clipped. One steelhead tagged at the mouth of the Klamath River was recaptured at WCW. The fish had been at liberty for 34 d. We recaptured three steelhead at JCW that had been tagged at WCW. They had been at liberty for 12 to 42 d, for a mean of 28 d.

Incidence of Gill-net and Hook Scars. Twenty-four (7.4%) steelhead trapped at WCW had gill-net scars. We did not see any scars on steelhead trapped at JCW. The mean FL of the gill-net-scarred steelhead at WCW was moderately larger than the non-gill-net-scarred steelhead, but the difference was not statistically different (Table 3).

We observed hook scars on 2% of the steelhead trapped at WCW and JCW (Table 3).

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