Upper Columbia Spring Chinook Salmon, Steelhead, and Bull Trout Recovery
Current Population Characteristics
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- Upper Columbia Spring Chinook
- Productivity
- Spatial structure and diversity
2.3.3Current Population CharacteristicsThis section describes the current abundance, productivity, spatial structure, and diversity of each population within the Upper Columbia Basin. Some VSP parameters, such as returns per spawner, are not available for recent years because not all fish from recent spawning escapements have returned from the ocean. This section relies heavily on the information provided by NOAA Fisheries (T. Cooney, NOAA Fisheries, personal communication) and the Bull Trout Draft Recovery Plan (USFWS 2002). This plan reports the 12-year geometric mean for abundance and productivity as the appropriate interval to measure current status of spring Chinook and steelhead. The twelve-year period falls within the recommended guidance of the ICBTRT (8-20 years) and represents two to three generations for spring Chinook and steelhead. The geometric mean provides a better indicator of central tendency than the arithmetic mean, which is often skewed by uncommon large and small returns. The geometric mean for productivity (returns per spawner) must be back calculated, based on run reconstruction, for five years previous to the most recent abundance estimate. Upper Columbia Spring ChinookCurrent (from 1960 to present) abundance and production for each population of spring Chinook in the Upper Columbia Basin were based on spawner estimates (spawning escapements) and returns per spawner (spawner to spawner return rates), respectively. Spawning escapement was based on numbers of redds, expanded by an estimated fish/redd ratio of 2.2 fish/redd.39 Returns from each brood-year spawning escapement were estimated by run reconstruction based on age composition. Year-specific age-composition estimates were obtained from spawning ground surveys, tributary fishery samples, or corresponding hatchery returns. Returns from each spawning escapement were estimated by summing up the subsequent returns from each spawning escapement across the appropriate range of future years. See NOAA Fisheries website http://www.nwr.noaa.gov/Salmon-Recovery-Planning/index.cfm for a description of analytical methods, assumptions, and results. WenatcheeAbundanceFrom 1960 to 2003, abundance of age 3+ spring Chinook in the Wenatchee subbasin ranged from 51 to 6,718 fish (Table 2 .1, Figure 2 .7).40 During this period the 12-year geometric mean of spawners in the subbasin ranged from 383 to 3,449 adults (Table 2 .1, Figure 2 .7). The geometric mean at the time of listing (1999) was 417 spawners. ProductivityDuring the period 1960 to 1999, returns per spawner for spring Chinook in the Wenatchee subbasin ranged from 0.06 to 4.59 (Table 2 .1,Figure 2 .7). The 12-year geometric mean of returns per spawner during this period ranged from 0.31 to 1.19 (Table 2 .1, Figure 2 .7). The geometric mean at the time of listing (1999) was 0.74. WDFW has estimated the freshwater productivity (smolts per redd) of spring Chinook in the Wenatchee subbasin for the period 1992-2002 (WDFW, unpublished data). Numbers of smolts and redds were estimated at three different spatial scales: Wenatchee subbasin, area upstream from Tumwater Canyon, and the Chiwawa basin. The geometric mean for the Chiwawa was 364 smolts/redd. The geometric mean for the area upstream of Tumwater Canyon was 250 smolts/redd, while the geometric mean for the total Wenatchee subbasin was 197 smolts/redd (Figure 2 .8). These estimates are not independent, because estimates for the Chiwawa basin are included in the estimate for the area upstream from Tumwater Canyon, which are included in the total Wenatchee subbasin estimate. Habitat downstream of Tumwater Canyon is less productive than the upper watershed. Spatial structure and diversitySpring Chinook currently spawn and rear in the upper main Wenatchee River upstream from the mouth of the Chiwawa River, overlapping with summer Chinook in that area (Peven 1994). The primary spawning areas of spring Chinook in the Wenatchee subbasin include Nason Creek and the Chiwawa, Little Wenatchee, and White rivers (Figure 2 .9). During high abundance years, such as 2001, spring Chinook also spawn in Chiwaukum Creek. Beginning in 2001, the USFWS and the Yakama Nation (YN) planted Leavenworth (Carson stock) adult spring Chinook into Peshastin Creek. The outplanting was part of a study to determine if hatchery adult plants could be used to restore the spring Chinook population in Peshastin Creek. The last outplanting is scheduled for 2005. These fish are not part of the ESU. Spawning in Icicle Creek is from out-of-basin (non-listed) spring Chinook released from the Leavenworth National Fish Hatchery (Chapman et al. 1995). After 1850, the diversity of the Wenatchee population was likely reduced because of hatchery programs, commercial harvest, and habitat degradation. The diversity of the Wenatchee population was also reduced in part because of the Grand Coulee Fish Maintenance Project (GCFMP) and hydropower development. The continued release of out-of-basin spring Chinook from the Leavenworth National Fish Hatchery may have some effect on the diversity of spring Chinook in the Wenatchee subbasin. Tagging studies indicate suggested that stray rates are generally low (<1%) (Pastor 2004).41 Recently, based on expanded carcass recoveries from spawning ground surveys (2001-2004), the straying from Leavenworth National Fish Hatchery and other out-of-basin facilities has accounted for 3-27% of the natural spawner composition upstream from Tumwater Canyon despite the low percentage of the Leavenworth National Fish Hatchery population historically detected straying. The Wenatchee spring Chinook population is currently distributed across four interconnected spawning watersheds (Chiwawa, Nason, White, and Little Wenatchee), which increases population diversity. However, compared to the historical condition, the current distribution of naturally produced spring Chinook in the Wenatchee subbasin is reduced because of the loss of naturally produced fish spawning in tributaries downstream from Tumwater Canyon. When considering the 9 factors (and 12 metrics identified in ICBTRT 2005a and shown in Appendix B) that determine diversity and spatial structure, the Wenatchee spring Chinook population is currently considered to be at a high risk of extinction (Table 2 .2). Two metrics that kept the population from achieving a low risk rating were: (1) Chiwawa hatchery fish (local origin stock) have averaged more than 30% of total spawners and more than 10% of the spawner composition in other non-target major spawning areas and (2) there is a high proportion (3-27%) of out-of-basin hatchery produced fish from the Leavenworth National Fish Hatchery on spawning grounds (Appendix B). Based only on abundance and productivity, the Wenatchee spring Chinook population is not viable and has a greater than 25% chance of extinction in 100 years (Figure 2 .10). Combining all VSP parameters together (using method described in ICBTRT 2005a), the Wenatchee spring Chinook population is not currently viable and has a high risk of extinction (Table 2 .3).42 EntiatAbundanceFrom 1960 to 2003, abundance of age 3+ spring Chinook in the Entiat subbasin ranged from 18 to 1,197 fish (Table 2 .1; Figure 2 .11).43 During this period the 12-year geometric mean of spawners in the subbasin ranged from 90 to 490 adults (Table 2 .1; Figure 2 .11). The geometric mean at the time of listing (1999) was 92 spawners. ProductivityDuring the period 1960 to 1999, returns per spawner for spring Chinook in the Entiat subbasin ranged from 0.16 to 4.72 (Table 2 .1; Figure 2 .11). The 12-year geometric mean of returns per spawner during this period ranged from 0.41 to 1.12 (Table 2 .1; Figure 2 .11). The geometric mean at the time of listing (1999) was 0.76. Presently there are too few data to estimate tributary productivity (smolts/redd) for Entiat spring Chinook. When more data are available, this plan will estimate tributary productivity of Entiat spring Chinook. Spatial structure and diversityHamstreet and Carie (2003) described the current spawning distribution for spring Chinook in the Entiat subbasin as the Entiat River (river mile 16.2 to 28.9) and the Mad River (river mile 1.5-5.0) (Figure 2 .12). The original diversity of the Entiat population was reduced because of hatchery practices, past harvest, hydropower development including dams that blocked passage into the Entiat River, habitat degradation, and releases of out-of-basin stock44 from the Entiat National Fish Hatchery.45 The Entiat River has a history of impoundments from the late 1880s through the first half of the 1900s. The U.S. Bureau of Fisheries surveys in the 1930s noted that three dams without fish passage remained on the Entiat River (Bryant and Parkhurst 1950). Because of its small size (relative to other subbasins in the Upper Columbia) and natural barriers, the Entiat subbasin offers limited numbers of suitable habitat areas for spring Chinook. Therefore, this population would naturally be at a higher risk than other populations in the Upper Columbia because of the naturally limited size of spawning and rearing habitat. When considering the 9 factors (and 12 metrics identified in ICBTRT 2005 and shown in Appendix B) that determine diversity and spatial structure, the Entiat spring Chinook population is currently considered to be at a high risk of extinction (Table 2 .2). Two factors contributed to this high-risk rating and both were related to the Entiat National Fish Hatchery propagating out-of-basin spring Chinook (Appendix B). Based only on abundance and productivity, the Entiat spring Chinook population is not viable and has a greater than 25% chance of extinction in 100 years (Figure 2 .13). Combining all VSP parameters together (using method described in ICBTRT 2005), the Entiat spring Chinook population is not currently viable and has a high risk of extinction (Table 2 .3). MethowAbundanceFrom 1960 to 2003, abundance of age 3+ spring Chinook in the Methow subbasin ranged from 33 to 9,904 adults (Table 2 .1; Figure 2 .14).46 During this period the 12-year geometric mean of spawners in the subbasin ranged from 480 to 2,231 adults (Table 2 .1; Figure 2 .14). The geometric mean at the time of listing (1999) was 480 spawners. ProductivityDuring the period 1960 to 199947, returns per spawner for spring Chinook in the Methow subbasin ranged from 0.05 to 5.21 (Table 2 .1; Figure 2 .14). The 12-year geometric mean of returns per spawner during this period ranged from 0.41 to 1.02 (Table 2 .1; Figure 2 .14). The geometric mean at the time of listing (1999) was 0.51. Presently there are too few data to estimate tributary productivity (smolts/redd) for Methow spring Chinook. When more data are available, this plan will estimate tributary productivity of Methow spring Chinook. Spatial structure and diversitySpring Chinook currently spawn in the mainstem Methow River and the Twisp, Chewuch, and Lost drainages (Scribner et al. 1993; Humling and Snow 2004). A few also spawn in Gold, Wolf, and Early Winters creeks (Figure 2 .15). The original diversity of the Methow population was reduced because of man-made barriers near the confluence, early 1900s hatchery practices, the GCFMP, past harvest, hydropower development, habitat degradation, and the release of out-of-basin stock from the Winthrop National Fish Hatchery.48 The USFWS transitioned from the release of out-of-basin stock to the listed stock from 2000 to 2006 (B. Cates, personal communication, USFWS). The population is currently distributed across three major watersheds (Twisp, Chewuch, and Upper Methow), which increases population diversity and reduces risk from catastrophic events. When considering the 9 factors (and 12 metrics identified in ICBTRT 2005 and shown in Appendix B) that determine diversity and spatial structure, the Methow spring Chinook population is currently considered to be at a high risk of extinction (Table 2 .2; Appendix B). Two factors contributed to this high-risk rating: (1) there is very little divergence occurring within the population; and (2) out-of-basin Carson stock were propagated in the past and the genetic legacy of these out-of-basin fish is still significant in fish used in the state and federal hatchery programs (Appendix B). Based only on abundance and productivity, the Methow spring Chinook population is not viable and has a greater than 25% chance of extinction in 100 years (Figure 2 .10). Combining all VSP parameters together (using method described in ICBTRT 2005), the Methow spring Chinook population is not currently viable and has a high risk of extinction (Table 2 .3). OkanoganAbundanceCurrently, there are no naturally produced spring Chinook in the Okanogan subbasin. A recent run of the Ecosystem Diagnosis and Treatment (EDT) model predicted that a viable population of spring Chinook cannot be maintained currently because of in-basin and out-of-basin factors (see Section 3.7 and Okanogan Subbasin Plan 2005). ProductivityThere is presently no production of spring Chinook in the Okanogan subbasin. Spatial structure and diversitySpring Chinook do not naturally occur within the Okanogan subbasin. In 2002, the USFWS released out-of-basin, Carson-stock spring Chinook smolts and fry into Omak Creek. As noted earlier, these fish are not part of the ESU. Salmon Creek probably has the greatest habitat potential in the U.S. portion of the Okanogan subbasin (Okanogan Subbasin Plan 2005). 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