ANNUAL RUN-SIZE, HARVEST, AND SPAWNER ESCAPEMENT ESTIMATES FOR TRINITY RIVER BASIN CHINOOK AND COHO SALMON AND STEELHEAD (continued)
Spring-Fall Chinook Separation. Analysis of known-race WCW-tagged chinook showed that beginning JW 36 (3-9 Sept) and continuing thereafter, the proportion of fall chinook exceeded that of spring chinook. Therefore, for the purposes of this report, the 33 chinook trapped prior to JW 36 were considered spring-run while the 386 chinook trapped that week and after were considered fall chinook (Figure 3, Table 1).
Spring chinook were the predominant race at JCW through JW 37 (10-16 Sept) after which fall chinook became predominant. The 656 chinook trapped through JW 37 were considered spring chinook while the 738 chinook trapped after JW 37 were considered fall chinook for the purposes of this report (Figure 3, Table 2).
Run Timing. The spring chinook run at WCW was limited to the first two weeks of trapping. Fall chinook catch at WCW peaked (17.6 fish/night) during JW 40 (1-7 Oct) and decreased gradually over the next eight weeks to 0.4 fish/night (Figure 4, Table 1).
At JCW, spring chinook catch peaked (26.3 fish/night) during JW 26 (25 Jun-1 July), decreased and peaked again (18.5 fish/night) during JW 33 (13-19 Aug). Fall chinook catch peaked at 33.0 fish/night during JW 40 (1-7 Oct) and decreased thereafter (Figure 4, Table 2).
Sizes of Trapped Fish. The average sizes of the spring chinook trapped at WCW and JCW, and that entered TRH were similar. Based on the analysis of combined FL distribution for the three sites, the size separating grilse and adult spring chinook was 56 cm FL (Figure 5). Limited information from known-age, CWTed spring chinook that entered TRH supported the 56 cm FL separation of adults and grilse (Appendix 2). Therefore, this season, we considered spring chinook in the Trinity River basin <56 cm FL to be grilse, while adults are >56 cm FL.
Grilse comprised 18.2%, 41.5%, and 28.9% of the spring chinook observed at WCW, JCW, and TRH, respectively.
The fall chinook FL distributions for either weir were not similar in showing the size separation between grilse and adults, but for the TRH and the combined FL distributions, 49 cm FL was the nadir (Figure 6). Size data of known-age, CWTed fall chinook entering TRH also supported the size separation (Appendix 3). Therefore, this season, we considered fall chinook in the Trinity River basin <49 cm FL to be grilse, while adults were >49 cm FL.
Fall chinook grilse comprised 20.7%, 26.4%, and 5.3% of the runs observed at WCW, JCW, and TRH, respectively.
Effectively Tagged Fish. We trapped 656 spring chinook at JCW, of which 610 (233 grilse and 377 adults) were effectively tagged (Appendix 4). The number effectively tagged accounted for tagging mortalities (15), poor-condition untagged fish (27), fish that died prior to tagging (3), and fish from which an angler reported removing the tag (1). The effectively tagged number included 446 (73.1%) reward-tagged fish (173 grilse and 273 adults).
We trapped 386 fall chinook at WCW, one of which was dead in the trap, 21 which were released untagged, and three fish from which anglers had removed the tags. We effectively tagged 361 fall chinook (74 grilse and 287 adults) at WCW during the 1992-93 season (Appendix 5). We placed reward tags on 172 fish (31 grilse and 141 adults), or 47.6%, of the effectively tagged fall chinook at WCW.
We trapped 738 fall chinook at JCW, of which 669 (160 grilse and 509 adults) were effectively tagged (Appendix 5). The fish not effectively tagged included one dead in the trap, 67 released untagged, and one which had its tag removed by an angler.
Reward tags were placed on 249 (86 grilse and 163 adults), or 37.2%, of the effectively tagged fall chinook at JCW.
Incidence of Tags and Fin Clips. Nine of the 31 (29%) spring chinook salmon effectively tagged at WCW were recaptured at JCW. Length of time for migration between the weirs for these fish ranged from 11 to 51 d, averaging 24 d.
Ad-clipped fish comprised 6.1% (2/33) of the spring chinook seen at WCW and 6.9% (45/656) of those seen at JCW (Appendix 4). One of the two Ad-clipped spring chinook Project-tagged at WCW was recovered at TRH. Its CWT indicated it was actually a 1987 brood year fall chinook (Table 3).
Twenty-five (55.6%) of the 45 Ad-clipped spring chinook tagged at JCW were recovered at TRH. Of these, 19 were spring chinook from TRH, one was a naturally produced chinook and five had shed their CWTs (Table 3).
Twenty-one (5.8%) of the 361 fall chinook effectively tagged at WCW were recovered at JCW. Length of time to travel between the weirs for these fish ranged from 13 to 32 d, averaging 22 d.
Ad-clipped fish comprised 3.9% (15/386) of the fall chinook seen at WCW and 5.7% (42/738) of those seen at JCW (Appendix 5). Four of the 15 (26.7%) Ad-clipped fall chinook tagged at WCW were recovered at TRH, all of which were originally marked as juveniles at TRH (Table 3).
Thirteen (30.9%) of the 42 Ad-clipped fall chinook which were tagged at JCW were recovered at TRH. From these, 11 CWTs were extracted, all of which originated from TRH (Table 3).
Incidence of Gill-net and Hook Scars. At both weirs, 8.4% of the spring chinook trapped were gill-net scarred. As noted last year (Lau et al. 1994), gill-net-scarred spring chinook were on average larger than non-gill-net-scarred fish. At JCW the difference in size was statistically significant (t=4.82, d.f.=86, P<.01) while at WCW, it was not (t=1.43, d.f.=17, P>.05).
For fall chinook, 7.8% and 4.6% of the fish trapped at WCW and JCW, respectively, were gill-net-scarred. As with spring chinook, gill-net-scarred fish were larger, on average, than non-gill-net-scarred fish. At both weirs, the differences were statistically significant (JCW: t=3.61, d.f.=47, P<.01; WCW: t=3.52, d.f.=54, P<.01).
Seven of the 610 effectively tagged spring chinook at JCW were ocean-hook-scarred. At WCW, none of the 361 effectively tagged fall chinook bore ocean-hook-scars.
Coho Salmon
Run timing. We trapped the first coho at WCW on 24 September 1992 (JW 39). The average weekly catch of coho peaked (35.0 fish/night) within three weeks of the first capture, then steadily decreased to 1.6 fish/night over the next three weeks. Catches remained near this level through the remainder of the trapping season, ending JW 48 (26 Nov - 2 Dec) (Figure 7). We trapped 405 coho salmon at WCW during the 1992-93 season (Table 4).
The first coho entered the JCW trap on 9 October (JW 41), approximately two weeks after they initially appeared at WCW.
The coho run at JCW was characterized by three peaks occurring at two week intervals starting JW 43 (22-28 Oct). However, the average weekly catch varied only slightly, ranging from 2.0 to 5.5 fish/night throughout most of the trapping season (Figure 7). We trapped 95 coho at JCW during the 1992-93 season (Table 5).
Size of Fish Trapped. The size ranges and mean FLs of coho trapped at WCW and JCW were similar (Appendix 6). The size separating grilse and adult coho was based on the combined length data from coho trapped at WCW, JCW and that entered TRH. The nadir separating grilse and adults was 50 cm FL for TRH and JCW data, and 48 cm FL for WCW data. The combined (TRH, JCW and WCW) data showed the separation between grilse and adults was 50 cm FL (Figure 8). This year all coho <50 cm FL were considered grilse, while larger coho were adults.
Grilse coho comprised 23.0%, 27.1%, and 33.8% of the coho trapped at WCW, JCW, and TRH, respectively.
Effectively Tagged Fish. We trapped 405 coho salmon at WCW of which 403 (93 grilse and 310 adults) were effectively tagged. Two coho were not tagged because they were in poor condition. The effectively tagged coho included 202 (50.1%) reward-tagged fish (54 grilse and 148 adults).
A total of 96 coho salmon was trapped at JCW, of which five were released untagged because they were in poor condition. Thus, 91 coho (22 grilse and 69 adults) were effectively tagged (including six that were originally tagged at WCW). Reward-tagged coho composed 47.6% of the effectively tagged fish (10 grilse and 30 adults), not including the fish originally tagged at WCW.
Incidence of Tags and Fin Clips. We recaptured six coho at JCW that had been tagged at WCW. Their mean migration time was 19.5 d, for a mean migration rate of 4.6 km/d. This is a faster rate of migration than was observed during the 1991 season of 3.4 km/d (Lau et al. 1994).
We trapped 37 Ad-clipped coho at WCW (10 grilse and 27 adults), which comprised 9.1% of the total WCW coho catch (Appendix 6). At JCW, 5.2% (5/96) of the coho trapped were Ad-clipped (one grilse and four adults). Sixteen Ad-clipped coho tagged at WCW and four from JCW were recovered at TRH. CWTs were extracted from 18 Ad-clipped coho, all of which were from TRH (Table 3).
Incidence of Gill-net and Hook Scars. We found gill-net scars on 2.2% and 1.1% of the coho trapped at WCW and JCW, respectively. Slightly higher incidences (4.1% and 1.8%, respectively) were observed last year (Lau et al. 1994).
We found 1.7% and 2.1% of the coho trapped at WCW and JCW, respectively, to be hooked-scarred. All of the hook scars appeared to be of freshwater origin.
Fall-run Steelhead
Run Timing. We caught steelhead each week from 20 August through 2 December (JW 34-48) at WCW (Figure 9). Peak average weekly catch (7.0 fish/night) occurred at WCW during JWs 40 (1-7 Oct) and 44 (28 Oct - 4 Nov). The number of steelhead trapped declined through the end of the trapping season. However, the steelhead run did not appear to be over when we removed the weir for the season. We trapped 190 steelhead (176 adults and 14 half-pounders) at WCW during the 1992-93 season (Table 6).
We caught steelhead intermittently at JCW from JW 27 through JW 49 (2 July - 2 December) (Figure 9). The steelhead run peaked JW 47 (19-25 November) at JCW. We trapped 29 steelhead at JCW during the 1992-93 season (Table 7).
Size of Fish Trapped. Steelhead caught at WCW, JCW, and TRH averaged 56.9, 55.3, and 49.7 cm FL, respectively (Figure 10). The average FL was smaller at TRH than the other sites, primarily because of the large number of sub-adults sampled there. Sub-adult steelhead made up 7.4%, 6.9%, and 22.4% of the steelhead trapped at WCW, JCW, and TRH, respectively. It is likely that many of the sub-adults observed at TRH were actually residualized or resident fish.
Effectively Tagged Fish. We trapped 176 adult steelhead at WCW, 10 of which were released untagged. There were no tagging mortalities, for a total of 166 effectively tagged adult steelhead (Appendix 7). Included in the total were 83 reward-tagged fish.
We trapped and reward-tagged 27 adult steelhead at JCW this season. There were no tagging mortalities, and one tag was removed by an angler, resulting in 26 effectively tagged steelhead (Appendix 7).
Incidence of Tags and Fin Clips. We observed fin clips on 76 adult and nine subadult steelhead at WCW, and 16 adults and one subadult at JCW (Appendix 7). The bulk of these (55.3% at WCW and 70.6% at JCW) were from the 1990 BY released from TRH in March 1991 (Appendix 8). Assuming that all the TRH-produced steelhead captured at the weirs were fin-clipped, 43.2% (76/176) and 59.3% (16/27) of the adults observed at WCW and JCW, respectively, were TRH-produced.
Incidence of Gill-net and Hook Scars. Five (2.8%) of the adult steelhead trapped at WCW had gill-net scars. The mean FL of the gill-net-scarred steelhead was slightly larger (60.0 cm) than the non-gill-net-scarred steelhead (56.8 cm). No gill-net-scarred steelhead were trapped at JCW.
Hook scars were observed on 3.2% (6 fish) and 3.4% (one fish) of the steelhead trapped at WCW and JCW, respectively.
Angler Harvest Regulation. Department of Fish and Game fishing regulations can affect the return of tags each year by limiting harvest. Special quota restrictions were in place during the 1992-93 season, which decreased the number of adult chinook caught by anglers (Appendix 9).
Spring-run Chinook. Anglers returned 36 tags from spring chinook tagged at JCW. These included 32 reward (12 adults and 20 grilse) and four non-reward tags (all grilse). We estimated the harvest rate, based on the return of reward tags, at 4.4% for adults and 11.6% for grilse. The number of days between tagging and reported capture by anglers ranged from zero to 133 d, with a mean time-at-large of 40.5 d.
Fall-run Chinook. Anglers returned only 12 tags (five reward and seven non-reward) from fall chinook salmon tagged at WCW. Reward tags from 2.1% (3/141) of the adults and 6.5% (2/31) of the grilse were returned by anglers. Anglers returned non-reward tags from fall chinook at the rate of 3.4% (5/146) for adults and 4.7% (2/43) for grilse. Since so few tags were returned, and non-reward tags (from adults) were returned at a higher rate than reward tags, we used reward plus non-reward tags to estimate harvest rates. The overall harvest rate of fall chinook upstream of WCW was 2.8% for adults and 5.4% for grilse.
Anglers returned only four tags from the 669 fall chinook effectively tagged at JCW. These tags included three from reward-tagged adults and one from a non-reward-tagged grilse. The overall (reward + non-reward) harvest rate upstream of JCW was 0.6% for grilse and 1.8% for adults.
Coho Salmon. We estimated the overall harvest rate of coho upstream of WCW this season to be 0.2%. Only one of the 403 coho tagged at WCW was reported caught by anglers.
No tags were returned by anglers from coho tagged at JCW. We assumed that no coho were harvested upstream of JCW this season.
Fall-run Steelhead. Anglers returned 12 tags from WCW-tagged steelhead; four non-reward and eight reward tags. Based on the reward tags returned, we estimated anglers caught 9.6% of the steelhead migrating upstream of WCW. The mean size of the fish caught was 52.9 cm FL. The steelhead were caught from zero to 159 d after being tagged, with a mean of 42 d.
Anglers returned four of the 26 reward tags from steelhead tagged at JCW. Based on the tags returned, 15.4% of the steelhead migrating upstream of JCW were caught by anglers. The mean size of the steelhead reported caught was 59.7 cm FL. Anglers captured fish from 83 to 141 d after tagging, with a mean time-at-large of 112 d.
Trinity River Hatchery
Coded-wire Tag Number 065639. Chinook from this CWT group were originally tagged as spring chinook smolts, but based on the timing of their entrance into TRH, appeared to be actually a composite of both spring and fall chinook. These fish began entering TRH early in the season, like the other spring CWT groups, but they continued through the period associated with fall chinook (Table 8). Based on the numbers and timing of these fish entering TRH, we estimated between 50% and 75% of this group were fall chinook. For analysis purposes, we considered fish from this group entering TRH after 15 October to be fall chinook while those entering before that date were considered spring chinook. Why this group consisted of fish from both runs is unknown.
Spring-run Chinook Salmon. Based on CWT recoveries, spring chinook began entering TRH on 14 September (JW 37) and continued through 15 October (JW 42) (Figure 11, Table 8). We estimated that 1,846 spring chinook (533 grilse and 1,313 adults) entered TRH during the 1992-93 season.
We recovered 12 (38.7%) of 31 Project-tagged spring chinook from WCW at TRH (Table 9). The mean FL of the Project-tagged spring chinook from WCW that entered TRH was 3.9 cm less than the mean of those effectively tagged at the weir (Appendix 4). They had been tagged at WCW from 33 to 57 d before entering TRH, with an average of 40.7 d.
We recaptured 279 spring chinook (100 grilse and 179 adults) at TRH that we had tagged at JCW, including four fish which had been tagged at WCW, and recovered at both JCW and TRH. Thus, we recovered 45.7% of the spring chinook which were effectively tagged at JCW (Appendix 4). There was no difference in the mean FL of effectively tagged versus TRH-recovered spring chinook from JCW. The Project-tagged spring chinook from JCW had been at liberty from 15 to 236 d (mean of 67.4 d) before entering TRH.
We recovered 218 Ad-clipped spring chinook at TRH, but CWTs were recovered from only 161 of these fish. The greatest returns of CWT fish were from the 1988 and 1990 BYs that had been released as smolts (CWT numbers 066148 and 0601040103, respectively)
(Table 8).
Fall-run Chinook Salmon. Based on the recovery of CWTs, the first fall chinook entered TRH on 17 September 1992 (JW 38), the run peaked 2 November (JW 44), and decreased steadily through 30 November (JW 48), when the last CWTed chinook entered the hatchery (Figure 11). We estimated that 3,990 fall chinook (211 grilse and 3,779 adults) entered TRH during the 1992-93 season.
We recaptured 101 fall chinook (six grilse and 95 adults) at TRH that we had tagged at WCW (Table 9); this was 28% of those effectively tagged at the weir. These Project-tagged fish ranged from 46 to 89 cm FL, and averaged 66.8 cm FL, 3.9 cm larger than the mean size of those effectively tagged (Appendix 5). Project-tagged fish entered TRH from 12 to 46 d after tagging, averaging 28.2 d.
We recaptured 41.6% of the effectively tagged JCW-tagged fall chinook (41 grilse and 238 adults) at TRH (Table 9). These fish included eight fall chinook that had been previously tagged and released at WCW. JCW-tagged fish recaptured at TRH ranged in size from 40 to 87 cm FL, with a mean of 64.8 cm FL, similar to the mean size of all fall chinook tagged at JCW (Appendix 5). JCW-tagged fall chinook entered TRH from 3 to 41 d after tagging, averaging 11.6 d.
We recaptured 344 Ad-clipped fall chinook at TRH, and recovered 305 CWTs. TRH yearling CWT groups 065632 (1988 BY) and 065634 (1989 BY) comprised 53.4% and 13.1%, respectively, of the CWTs recovered (Table 10).
Coho Salmon. The first coho entered TRH on 13 October 1992 (JW 41), and the number entering TRH increased each week through JW 45 (4-11 November). The largest number of coho (1,045 fish) entered TRH during JW 47 (19-25 November). Coho numbers decreased rapidly during the remainder of the season with the last coho being trapped on 13 January 1993. We counted 3,582 coho (1,210 grilse and 2,372 adults) entering TRH during the 1991-92 season (Table 9).
We recovered 34.5% the effectively WCW-tagged coho (16 grilse and 123 adults) at TRH. Their mean FL (60.0 cm) was 2.6 cm greater than the mean FL of WCW effectively tagged coho (Appendix 6). Coho tagged at WCW had been at liberty from 10 to 63 d before entering TRH, with a mean time-at-large of 27.8 d.
We recovered 63.3% (13 grilse and 44 adults) of the effectively JCW-tagged coho at TRH (Appendix 6). These fish ranged in size from 38 to 69 cm FL, and averaged 57.3 cm FL, the same as the mean size of effectively tagged coho at JCW. The JCW-tagged coho took from 4 to 33 d to migrate to the hatchery, with a mean time-at-large of 10.4 d.
We recovered 321 CWTs from the 359 Ad-clipped coho that entered TRH (Table 11). The CWTs represented two tag-groups: Code numbers 065657 (1990 BY) and 065660 (1989 BY).
Fall-run Steelhead. The steelhead run into TRH began 26 October 1992 (JW 43) and ended 28 March 1993 (JW 13), after which the fish ladder was closed. A total of 586 steelhead (131 sub-adults and 455 adults) entered TRH during the 1992-93 season (Table 12).
Twenty-four WCW-tagged steelhead entered TRH (Table 12). They ranged in size from 48 to 68 cm FL, with a mean of 56.6 cm FL, 1.2 cm smaller than those effectively tagged (Appendix 7). Length of time for these steelhead to travel from WCW to TRH ranged from 27 to 77 d, averaging 45 d.
We recovered seven Project-tagged steelhead from JCW at TRH, including one fish that we had previously tagged at WCW (Table 12). These fish ranged from 49 to 67 cm FL, with a mean of 58.1 cm, 1.3 cm greater than the mean of those effectively tagged at the weir (Appendix 7). Length of time for JCW-tagged steelhead to travel from the weir to TRH ranged from 23 to 146 d, averaging 75.9 d.
We recovered 430 adult steelhead at TRH that had originally been fin-clipped by TFIP personnel. Fin-clipped steelhead accounted for 94.5% of the adult steelhead entering TRH. The bulk of the fin-clipped recoveries (227/430) were from the 1990 BY released as yearlings in 1991 (Appendix 8).
We also recovered 119 steelhead (including sub-adults) from the 1991 BY, released as yearlings from TRH in 1992. These fish ranged in FL from 26-74 cm, averaging 38.4 cm (Appendix 10). Only 23 (19%) of this fin-clip group were >41 cm FL and considered adults. It is probable that the 96 sub-adults recovered were actually residualized fish which had not migrated to the ocean.
