U.S. Fish and Wildlife Service Columbia River Fish and Wildlife Conservation Office
Literature Review of Survival, Age at Return, Straying, Life History Diversity and Ecological Effects of Subyearling and Yearling Hatchery Release Strategies for Fall Chinook Salmon
Jennifer Poirier and Doug Olson
U.S. Fish and Wildlife Service Columbia River Fish and Wildlife Conservation Office
Vancouver, WA 98683
April 20, 2017
ii
Disclaimers The findings and conclusions in this report are those of the authors and do not necessarily represent the views of the U.S. Fish and Wildlife Service. The mention of trade names or commercial products in this report does not constitute endorsement or recommendation for use by the federal government. The correct citation for this report is: Poirier, J. and D. Olson. 2017. Literature review of survival, age at return, straying, life history diversity and ecological effects of subyearling and yearling hatchery release strategies for fall Chinook salmon. U.S. Fish and Wildlife Service, Columbia River Fish and Wildlife Conservation Office, Vancouver, WA. 20 pp. www.fws.gov/columbiariver/publications.html
1
Executive Summary Fall Chinook salmon in the Columbia and Snake River basins express two distinct juvenile migratory patterns as a result of dam-related environmental change and hatchery management practices. Fish hatcheries have traditionally released juvenile fall Chinook as subyearlings to simulate historic migration timing of native stocks, but many facilities have also utilized a yearling release strategy to improve juvenile survival and adult returns. This review was undertaken to gather relevant literature and summarize the current state of knowledge regarding the effects of fall Chinook release timing on survival, maturation schedule, harvest rates, straying, life history diversity, and ecological impacts. Fifty relevant documents were identified during the literature review process. Table 1 lists reports by author and publication year and highlights the major themes reviewed in each document. Surprisingly few documents directly compared the yearling and subyearling release strategy (i.e. within a hatchery stock), nevertheless important differences exist between the two strategies that may influence the future stability of hatchery stocks. The following list summarizes the major themes found in the reviewed literature.
• The presence of multiple life history types can ensure population resiliency against
environmental change. • Maintaining the genetic diversity of hatchery stocks by promoting all life history types
present in the basin may enhance the stability and resiliency of fall Chinook populations against further environmental change.
• Subyearlings account for the predominant life history pattern for naturally produced fall Chinook salmon.
• There can be a hatchery survival advantage for rearing subyearling fall Chinook to a longer size or for an extended period; however, extended hatchery rearing periods can lead to increased fish pathology issues.
• Hatchery fall Chinook released as yearlings generally have higher overall survival and/or higher return rates than fall Chinook released as subyearlings; however, survival advantages can also be hatchery/location dependent.
• Rearing subyearling fall Chinook at high-densities within a raceway was also identified as a means to enhance adult production. Increasing the number of fish per raceway may compensate for reduced survival of subyearlings by yeilding a greater number of returning adults per unit of rearing space.
• There is some evidence that slowing the growth of juveniles and special low fat experimental diets may decrease the instance of early maturity in hatchery fall Chinook.
2
• Hatchery fall Chinook released as yearlings generally return at younger average ages and often return as minijacks and jacks at a much higher frequency than hatchery subyearlings.
• Generally, subyearling releases returned a higher proportion of adults at a larger size that were available for harvest, whereas the yearling release had higher survival but returned a higher proportion of mini-jacks and jacks.
• Stray rates likely depend on a combination of factors including hatchery rearing conditions, life history, broodstock history, natural enviromental conditions, and genetics.
• Ecological studies on predation and competition were difficult to quanitify regarding subyearling and yearling release strategies; however, predation could be higher from yearling releases feeding on younger, smaller fish, whereas the likelihood of instream competition may be higher for a subyearling hatchery release. It was also noted that ecological impacts may be minimized by specific hatchery management actions regarding release timing, location of release and magnitude of release.
3
Table 1. Summary of references by author, publication date, and theme reviewed for comparing the effects of subyearling and yearling releases of fall Chinook salmon.
References
Anchor Env. And Natural Resources Consultants (2005) XArnsberg and Kellar (2013) X XBanks and LaMotte (2002) XBugert et al. (1997) X X XCalifornia HSRG (2012) X XClarke et al. (2016) X XClarke et al. (2015) X X X XClarke et al. (2013) X XConnor et al. (2005) X X XConnor et al. (2004) XDeHart (2008, 2009, 2010) XFowler and Banks (1980) XFowler et al. (1980) XGoudy (2016) X XHankin and Logan (2010) X X XHankin (1990) X X XHarstad et al. (2014) XHayes and Carmichael (2002) X XHegg et al. (2013) XJohnson et al. (2012) XKeefer and Caudill (2014) XKostow (2009) XMarsh et al. (2007) XMartin and Wertheimer (1989) XMilks et al. (2009) XMiller et al. (2010) XMuir and Coley (1996) XMyers et al. (1998) XNaman and Sharpe (2012) XPearsons (2008) XPearsons and Fritts (1999) XQuinn (1997) XRosenberger et al. (2017) X X XSeidel and Mathews (1977) X XSholes and Hallock (1979) X X XStrange and McCovey (2008) XTatara and Berejikian (2012) XTipping (2011) X XUSFWS (2007) XVøllestad et al. (2004) XWarner et al. (1961) X X XWeber and Fausch (2003) XWeitkamp et al. (2015) XWestley et al. (2013) XWilliams et al. (2008) XWilliamson et al. (2010) XYoung et al. (2013) XZimmerman et al. (2003) X
Survival
Ageat
Return
Straying
LifeHistory
EcologicalIm
pacts
Harvest
4
Table of Contents
Executive Summary ....................................................................................................................................... 1
Introduction .................................................................................................................................................. 5
Methods ........................................................................................................................................................ 5
Results & Discussion ..................................................................................................................................... 6
Life History Diversity ................................................................................................................................. 6
Survival ...................................................................................................................................................... 7
Adult Age at Return and Potential Harvest Implications .......................................................................... 9
Straying ................................................................................................................................................... 11
Ecological Impacts................................................................................................................................... 13
References .................................................................................................................................................. 15
5
Introduction
Hatchery production programs are faced with the challenge of releasing sufficient numbers of fish to maximize contribution to ocean and freshwater fisheries while assuring adequate escapement to meet mitigation requirements and hatchery spawning needs. To fulfill these obligations, managers frequently modify juvenile salmonid rearing or release strategies to increase survival and abundance of adult returns. Production techniques may include increasing or decreasing pond densities, slowing or accelerating growth (via feed rations or water temperature), or rearing fish for longer or shorter durrations. Fish hatcheries in the Columbia and Snake River Basins have traditionally released juvenile fall Chinook (Oncorhynchus tshawytscha) as subyearlings to mimic the historic migration timing of native stocks. Over time, high post release mortality and poor adult returns thought to be associated with the smaller size of subyearlings and declining environmental conditions during smolt outmigration (i.e., elevated water temperature, low flow), have prompted a number of facilities to transition all or a portion of their fall Chinook production to a yearling release strategy. Furthermore, if survival is suffienctly high enough for a yearling release strategy, fewer juvenile fish can be reared and released and subsequently will require fewer adult broodstock to sustain overtime.
This review presents a brief summary of literature specifically pertaining to fall Chinook subyearling and yearling release strategies with a focus on five major themes: life history diversity, survival, adult age at return and potential harvest implications, straying, and ecological effects. The purpose of this document is to consolidate available literature of subyearling and yearling fall Chinook release strategies to inform future research projects and help guide hatchery management decisions in the Columbia River basin.
Methods The preliminary search for literature was very broad; covering a wide geographic range. However, due to the specific nature of the topic (i.e., subyearling and yearling fall Chinook), the majority of relevant material was associated with the Columbia River basin. Documents included in this summary were primarily acquired by performing an online literature search (e.g., Google Scholar) and examining references cited within reports. Published and unpublished literature were included, although only the most recent versions of annual progress reports that could be found online were used. In addition to the online search, a request for literature was also submitted to the U.S. v. Oregon Production Advisory Committee to supplement the initial search (for example see Goudy 2016, and Rosenberger et al. 2017).
6
Results & Discussion
Life History Diversity Wild upriver bright fall Chinook salmon in the Columbia River Basin historically expressed an ocean-type (subyearling) life history pattern (Myers et al. 1998). Significant natural production areas can currently be found in the Deschutes River, Yakima River, Snake River, and Hanford Reach area of the Columbia River (Connor et al. 2005; Williams et al. 2008; Miller et al. 2010; Hegg et al. 2013; Clarke et al. 2016). In the mid-1990s researchers discovered that a portion of fall Chinook in the Snake River delay migration and overwinter in reservoirs or other freshwater locations before continuing migration the following spring as yearling smolt. This shift to a yearling migration strategy is thought to be a direct result of large-scale changes to environmental conditions associated with the construction and operation of hydroelectric dams (Connor et al. 2005; Williams et el. 2008; Hegg et al. 2013).
The reservoir life history (i.e. yearling) has been observed in wild fall Chinook populations originating from the Snake Basin, but tends to be more prevalent in hatchery stocks. Connor et al. (2005) analyzed scales of wild fall Chinook spawners collected from the adult fish bypass system at Lower Granite Dam during 1998-2003. Of the 384 wild fish sampled, 41% were found to be yearling ocean emigrants versus 51% of hatchery spawners (N=475). Hegg et al. (2013) also found evidence of a yearling migration pattern in the Snake River using otolith microchemistry. Otoliths were recovered from 120 wild adult spawners at Lyons Ferry Hatchery from 2006 to 2008. Results indicated that 62% of wild fish had followed a yearling life history pattern with the highest occurrence of the yearling life history strategy found in the Clearwater River (77% of juveniles). The Clearwater is considerably colder than the Snake River and authors speculate that later juvenile emergence and slower growth associated with cooler water temperatures has led to the expression of a yearling life history (Hegg et al. 2013).
Whether the expression of a yearling life history strategy in the Snake Basin is an adaptive (phenotypic) or evolutionary response to large scale environmental change is unknown. Williams et al. (2008) suggests that change in migration tactics may be a combination of both factors. The initial shift to a yearling life history was likely an adaptive response to changes in historic habitat conditions that lowered growth opportunity and delayed migration, but differential survival of yearling emigrants (see Survival section below) and heritability of life history traits has influenced a selective response that has perpetuated the trait. Current environmental conditions within the Snake Basin may favor the yearling life history strategy, but this could change with time. Williams et al. (2008) warns if the yearling migration tactic is an evolutionary response and river conditions revert to a more natural state (through habitat
7
restoration or dam removal), fall Chinook populations may be unable to respond or adapt quickly and will suffer further declines or potential extinction. Maintaining the genetic diversity of hatchery stocks by promoting all life history types present in the basin may enhance the stability and resiliency of fall Chinook populations against further environmental change (Connor et al. 2005; Miller et al. 2010).
Diversity in juvenile migration strategy has also been observed in California’s Central Valley fall Chinook populations. Wild fall Chinook typically emigrate from natal streams in February-March as fry (<55mm), in mid-April-May as smolts (>75mm), or during an intermediate period as parr (56-75mm). Hatchery production and flow management in the basin has focused almost entirely on a ‘larger’ life history type, releasing 98% of juveniles as smolts (54-65% of total releases) or parr (35-45% of total releases). Miller et al. (2010) used otolith microchemistry and structural analysis to quantify the contribution of juvenile life history types in a returning adult population. A total of 395 otoliths were collected from adult fall Chinook during the Oregon ocean troll fishery in 2006. Of the 100 fish identified as Central Valley fall Chinook, 20% were found to have emigrated as fry, 48% as parr, and 32% as smolt. The proportion of fry within the adult sample is believed to represent natural production as fry usually comprise less than 2% of total hatchery production in any given year. Results of the study suggest that all life history types are present and contribute to adult returns even though the vast majority of hatchery production is focused on larger life history types. The authors propose the presence of multiple life history types ensures population resiliency against environmental change and therefore management should focus on maintaining life history diversity rather than promoting a desired physical characteristic.
Survival The majority of studies reviewed have found that fall Chinook released as yearlings have higher overall survival and/or return at higher rates than subyearling fall Chinook (Warner et al. 1961; Seidel and Mathews 1977; Sholes and Hallock 1979; Hankin 1990; Bugert et al. 1997; Hayes and Carmichael 2002; Connor et al. 2005; Milks et al. 2009; Hankin and Logan 2010; California HSRG 2012; Arnsberg and Kellar 2013; Clarke et al. 2015; Rosenberger et al. 2017). Those cases where smolt to adult survival of subyearlings exceeded that of yearling releases were in the minority (USFWS 2007; Hankin and Logan 2010; Clarke et al. 2015; Rosenberger et al. 2017).
Research suggests that rearing fall Chinook longer or releasing juveniles at a larger size may increase post release survival (Seidel and Mathews 1977; Fowler and Banks 1980; Fowler et al. 1980; Martin and Wertheimer 1989; Hankin 1990; Bugert et al. 1997; Connor et al. 2004; Hankin and Logan 2010; Tipping et al. 2011; Goudy 2016). In the Columbia River basin, yearling
8
hatchery fall Chinook are reared an average of 10 months longer and released in spring when river conditions are more ammenable for downstream migration and passage through hydroelectric dams. A larger size at release is thought to benefit juveniles by lessening vulnerability to predation, increasing the speed of emigration, and improving foraging ability in the estuary (Bugert et al. 1997; Connor et al. 2004).
There is also some indication that a longer rearing time and larger size at release may improve post release and adult survival of fall Chinook released as subyearlings. At Spring Creek National Fish Hatchery, subyearling tule fall Chinook have been released as fingerlings in March at 100/lb – 183/lb, in April at 49/lb – 128/lb, and in May at 36/lb – 134/lb (USFWS 2007). Compared to March, extended rearing to April and May typically resulted in higher percent survival to adult; however, it was also noted that in some years extended rearing to May resulted in fish health problems prior to release. Fish health problems were also noted for extended rearing to the yearling stage for the Yakima River fall Chinook program (Goudy 2016).
Hankin (1990) analyzed tag recovery data from three hatcheries that release subyearling and/or yearling fall Chinook (i.e., Iron Gate, Trinity River, and Bonneville Hatcheries). Juveniles were released from these facilities as subyearlings during early summer (June-July), fall (October-November), or as yearlings the following spring (March-April). Although average survival (to age 2) of yearling fall Chinook was highest (5.7%), survival of subyearlings released in October-November was comparable to that of yearlings (5.4%) and considerably higher than subyearling fall Chinook released during the traditional months of June-July (2.0%).
Tipping (2011) examined the effect of size at release on adult returns. Subyearling fall Chinook released from Priest Rapids Hatchery were graded into ‘large’ and ’small’ length groups during tagging and released in mid-June. Although the sample size was relatively small, results indicate that survival rates for ‘large’ fish were nearly double those of ‘small’ fish, and a greater number from the ‘large’ subyearling release groups were recovered as adults in both years of the study (2003 and 2004).
Connor et al. (2004) observed improved post release survival of subyearling reared to a larger size. Lyons Ferry Hatchery experimentally reared three groups of subyearlings to different lengths in order to determine the optimal rearing treatment and maximize performance of juveniles following release. Small (70-76mm), Medium (84-89mm), and large (90-103mm) subyearling fall Chinook were reared for the same five month time period, but rearing treatments were altered to accelerate or slow growth. In this study, large subyearlings emigrated more quickly and had higher downstream migration survival than medium and small subyearling release groups in both years of the study (1997 and 1998).
9
Rearing subyearling fall Chinook at high-densities within a raceway was also identified as a means to enhance adult production. Increasing the number of fish per raceway may compensate for reduced survival of subyearlings by yeilding a greater number of returning adults per unit of rearing space (Seidel and Mathews 1977; Hankin 1990; Martin and Wertheimer 1989). In Banks and LaMotte (2002), Tule fall Chinook subyearlings at Spring Creek National Fish Hatchery were reared at normal density (364,000 fish per pond) in addition to three reduced densities. Although fish reared at the lowest density (91,000 fish per pond) obtained the largest size at release, coded wire tag recovery data indicated adult survival rate was generally not affected by rearing density; however, adult yield from the normal density treatment was consistently greater than the ponds with reduced density, producing an average of 53 additional adults for every 1,000-fish increase in stocking density. In a rearing density study published by Clarke et al. (2013), upriver bright (URB) fall Chinook subyearlings at Umatilla Hatchery were reared at three experimental pond densities. At the end of the two year study, there was no significant difference in juvenile weight, outmigration survival, travel time, or smolt to adult survival between the density groups. However, the highest density treatment (400,000 fish per raceway) produced nearly twice as many adults as the low density (200,000 fish per raceway) and 27% more adults than the medium density (300,000 fish per raceway) treatment.
Adult Age at Return and Potential Harvest Implications Age at return
A growing body of evidence suggests that larger smolts tend to mature earlier and return at younger ages (e.g., VØllestad et al. 2004). Early maturation of hatchery fall Chinook may be influenced by rapid growth associated with the rearing environment (e.g., water temperature, food availability, diet content), or the practice of rearing juveniles to the yearling stage to obtain a larger size at release (Zimmerman et al. 2003; DeHart 2008; DeHart 2009; Harstad et al. 2014).
Adult return data in the Columbia and Snake Rivers indicates that hatchery fall Chinook released as yearlings generally return at a younger average age (DeHart 2010), and often return as minijacks (0-ocean) and jacks (1-ocean) at a much higher frequency than juveniles released as subyearlings (Zimmerman et al. 2003; Connor et al. 2005; Marsh et al. 2007; DeHart 2010; Young et al. 2013; Clarke et al. 2015; Goudy 2016; Rosenberger et al. 2017). For example, between 1993 and 2000, minijacks from yearling hatchery releases comprised 3.6-82.1% of fall Chinook salmon returns to the Umatilla River (Zimmerman et al. 2003). Tipping (2011)
10
observed a similar pattern at Priest Rapids Hatchery where the release of ‘large’ subyearlings returned significantly more jacks than ‘small’ subyearlings.
In general, most studies found that hatchery fall Chinook released as subyearlings had a lower rate of jack returns than hatchery yearlings (DeHart 2009; DeHart 2010). While there is evidence that early maturity is present in wild populations that exhibit a reservoir-type (i.e., yearling) life history pattern (Young et al. 2013; Connor et al. 2005), hatchery programs produce significantly more minijacks and jacks than natural populations. Furthermore, counts of minijacks and jacks tend to be highest in the Snake River where release of yearling fall Chinook is more common (DeHart 2009; Young et al. 2013). The only exception to the trend for early maturation of yearling fall Chinook was found outside of the Columbia River basin at Iron Gate and Trinity River Hatcheries in Northern California. Two independent studies observed that subyearling fall Chinook released in June-July tended to mature earlier than both subyearlings released in October-November and yearlings released in March-April (Hankin 1990; Hankin and Logan 2010). This outcome was attributed to subyearling fish entering the ocean at an earlier date and obtaining a larger size at age 2 and age 3 which induced early maturation.
High minijack and/or jack returns represent a direct loss of fish available for harvest and hatchery broodstock (Harstad et al. 2014). There is some evidence that slowing the growth of juveniles may decrease the instance of early maturity in hatchery fall Chinook. Umatilla Hatchery initiated a three year diet study to explore whether feed composition and rations could reduce the percentage of precocial males returning to the facility. Preliminary results from one complete brood year indicate that fish fed experimental rations (i.e., low fat-low ration, low fat-high ration, high fat-low ration, high fat-high ration) produced fewer minijacks (8/10,000 smolts) compared to control groups (71/10,000 smolts). Jack rates were variable between experimental groups with fish fed the high fat-low ration diet producing significantly more jacks. Fish fed the low fat-low ration diet produced the largest combined number of age 4 and age 5 adults, however, this group tended to have higher in-hatchery mortality than other treatment groups (Clarke et al. 2015).
Size and harvest rates
A potential consequence of larger size at age (besides early maturation) may be an increased suseptibility to harvest. In some cases, when fish were released as yearlings they were below the length limit for commericial harvest at maturity. In other cases the yearling release resulted in higher harvest. The following are specific case histories:
Subyearling fall Chinook released from Iron Gate and Trinity River Hatcheries had a higher age 3 ocean harvest rate than age 3 yearling fall Chinook from the same brood year (Hankin 1990; Hankin and Logan 2010). Yearling fall Chinook were an average of 45mm (Iron Gate) and 29mm
11
(Trinity River) shorter than subyearlings, and as a result were below the minimum length limit for commercial harvest. The authors add that the size difference between subyearling and yearling salmon was negligible by age 4, and harvest rates were near equal or higher for age 4 yearling fall Chinook. Warner et al. (1961) also found that yearling fall Chinook contributed very little to ocean commercial fisheries. A total of 20,579 marked fall Chinook were released into the American River (Gold River, CA), to test the effectiveness of rearing fish to a yearling age. In the three years following the release, an estimated 88 fish were captured in commercial troll fisheries while 732 returned to the American River and Nimbus Hatchery. Tag recoveries indicate that over 53% of marked fish matured at age 3, therefore fish were available for harvest only a short time and were presumably under the 26 inch commercial size limit due to less time and growth in saltwater. Within the Snake River, Rosenberger et al. (2017) reported on four side by side comparisons of yearling and subyearling release groups. The yearling release resulted in higher harvest rates when combining both adult and jack size fish. The yearling release also resulted in more jack size fish being harvested. The harvest rate of adult size fish, excluding jacks, from the yearling and subyearling release was more mixed. Three additional studies comparing harvest rates of yearling and subyearling fall Chinook releases had variable results. Sholes and Hallock (1979) found that yearlings released from Feather River Hatchery (Oroville, CA) contributed 12 times more to fisheries than fingerlings released from Coleman and Nimbus Hatcheries (brood years 1967, 1969 and 1970). Commercial and sport fishery harvest rates were relatively equal for yearling and subyearling fall Chinook released from Priest Rapids Hatchery from 1985-1990 (Bugert et al. 1997), versus Umatilla Hatchery where some years showed higher harvest rates for yearlings (run years 2010-2012), and some were higher for subyearlings (2013, 2014)[Clarke et al. 2015].
Straying “For a wild fish, home is the natal stream where it is incubated, hatched, and emerged. For transplanted fish, the ancestral locality or the hatchery where they are reared and the locality where they are released could both be considered homes. Salmon as a group generally home to natal sites to spawn. The other side of the homing ‘coin’ is straying.” Quinn 1997.
Straying can be positive. For example straying may provide temporary cool-water refuge during migration, or even exploratory movement for colonizing favorable habitat. Straying can also be detrimental to recipient populations through direct competition, displacement, decreased genetic diversity, lowered reproductive success, or reduced fitness of offspring (Weber and
12
Fausch 2003; Williamson et al. 2010; Johnson et al. 2012; Keefer and Caudill 2014). The hatchery rearing environment (e.g., use of well water, stable flow and temperature) transport strategies (e.g., hatchery transfers, outplanting, barging) and release practices (i.e. release during inappropriate developmental stages), potentially inhibit or interrupt the olfactory imprinting process leading to increased straying of returning adults (Keefer and Caudill 2014).
A small number of studies have directly compared straying between fall Chinook subyearling and yearling release strategies. In the Mid-Columbia River in the Umatilla River basin, stray rates of subyearling fall Chinook at Umatilla Hatchery often exceed those of yearling releases (Hayes and Carmichael 2002; Clarke et al. 2013; Clarke et al. 2015; Clarke et al. 2016). The subyearling stray rate in 2014 was 40.2% with a 10 year range of 10.4-63.6%, whereas the yearling fall Chinook stray rate was 23.4% with a range of 3.0-25.0% (Clarke et al. 2015). The persistently high stray rate of subyearlings is thought to be due to mismatched timing between release and juvenile developmental stage. Subyearling fall Chinook are reared in Umatilla Hatchery approximately four months prior to release and may not be physiologically prepared to imprint when they are first exposed to Umatilla River water (Clarke et al. 2015). The high stray rate of Umatilla Hatchery subyearlings could also be associated with rearing juveniles on well water. Hatcheries often rear fish on well water to reduce exposure to pathogens or increase growth, but it lacks the unique mix of organic and inorganic chemicals necessary for precise imprinting to the home stream (Keefer and Caudill 2014; Clarke et al. 2015; Clarke et al. 2016). Finally, straying of Umatilla Hatchery subyearlings may be a function of declining river conditions (i.e., low flow, high temperature, agriculture/industrial pollution) when adults return in fall (Clarke et al. 2016).
In contrast to the Umatilla Hatchery, fall Chinook releases from Lyons Ferry Hatchery show relatively high fidelity to the Snake River with yearlings straying at a higher rate than subyearlings. Over 4 million coded-wire tagged salmon were released from Lyons Ferry hatchery from 1985-1990. Of the 9,910 tags recovered, a total of 177 (125 yearlings, 52 subyearlings) were ultimately recovered as strays outside the Snake River. Bugert et al. (1997) attributed this low stray rate to using fish endemic to the Snake River for brood stock, releasing juveniles in active parr-smolt transformation, and outplanting fish in locations that allowed for a period of downstream migration in their natal river. Westley et al. (2013) also compared stray rates between yearling and subyearling fall Chinook at Lyons Ferry Hatchery during release years 1995-2004 and found that stray rates of yearling release groups were 2.5 times higher than subyearling release groups. The authors speculate the longer freshwater residence of yearling fish may disrupt natural growth patterns, endocrine activity and imprinting schedule that is characteristically observed for ocean-type fall Chinook.
13
Ecological Impacts Hatchery programs that rear fall Chinook can favor a yearling release strategy for a number of reasons. Yearling fish are larger and are easier to tag (Hankin and Logan 2010), are less susceptible to predation (Bugert et al. 1997; Connor et al. 2004), and generally have higher post release and/or smolt to adult survival requiring fewer broodstock along with lower juvenile release numbers (Warner et al. 1961; Seidel and Mathews 1977; Sholes and Hallock 1979; Hankin 1990; Bugert et al. 1997; Hayes and Carmichael 2002; Connor et al. 2005; Milks et al. 2009; Hankin and Logan 2010; California HSRG 2012; Arnsberg and Kellar 2013; Clarke et al. 2015). The hatchery release of yearling fall Chinook can raise some ecological concerns as well. Yearling fall Chinook are typically larger than naturally produced fall Chinook from the same stock (Arnsberg and Kellar 2013; Weitkamp et al. 2015), which may give them a competitive advantage over wild fish, or increase the tendancy for piscivory if prey-sized fish are present (Sholes and Hallock 1979; Pearsons 2008).
Yearling hatchery salmonids are capable of consuming prey approximately 45% of their own length (Pearsons and Fritts 1999), consequently, wild fish below this size threshold are highly susceptible to predation (Naman and Sharpe 2012). It is largely assumed that predation by hatchery yearlings on wild fry and subyearlings is minimal because hatchery origin smolts have no previous experience capturing natural prey and may be less aggressive when first released into the natural environment (Anchor Environmental and Natural Resources Consultants 2005). Nevertheless, Sholes and Hallock (1979) observed significant predation on naturally produced fall Chinook fingerlings by yearling fall Chinook in the Feather River, CA. Predation by yearling hatchery fall Chinook on emerging salmon fry was also a concern in the Green/Duwamish Watershed in Puget Sound, Washington. Stomach content analysis of yearling fall Chinook captured in a screw trap on the Green River found predation to be minimal (0.38 salmon/stomach), but sample size was small (n=8). As a precautionary measure, hatchery yearlings are released in early May after wild subyearling Chinook have grown and are too large to consume (Anchor Environmental and Natural Resources Consultants 2005).
Within the Columbia River, Muir and Coley (1996) characterized the diet composition of actively migrating yearling Chinook salmon smolts (hatchery and wild) at Lower Granite, McNary and Bonneville dams. Yearling fish consumed a variety of insects and amphipods, but fish comprised a minimal component of the diet (3.5-8.0% of total stomach content). Naman and Sharpe (2012) reviewed 14 freshwater salmonid predation studies from the Pacific Northwest and California and found that predation by hatchery yearlings on wild subyearlings was generally low, ranging from 0.00 – 0.54 subyearlings per hatchery fish. The authors caution however, that releasing large numbers of hatchery yearlings into the natural environment at
14
the same time may have a cumulative negative effect resulting in the loss of a high percentage of wild fish (Naman and Sharpe 2012).
The greatest potential for hatchery fish predation on wild fish exists when smolts are released in close proximity to emerging juvenile salmon, or when hatchery fish spend an extended time in freshwater. Yearling fall Chinook reared at Lyons Ferry and Iron Gate Hatcheries are released in April which coincides closely with wild fall Chinook emergence from the gravel in mid-April/June. Hatchery yearlings commonly migrate to the sea relatively quickly (Arnsberg and Kellar 2013) and occupy a different ecological niche than emerging fish so predation is likely low. Predation by hatchery subyearling fall Chinook on wild populations is doubtful because subyearlings are similar in size to natural fall Chinook at release (Weitkamp et al. 2015) and would be physically unable to prey upon most fish until they attain a larger size (Anchor Environmental and Natural Resources Consultants 2005).
Competition for freshwater resources (i.e. food, habitat) commonly occurs in areas where hatchery and wild fish overlap such as freshwater rearing areas, reservoirs, estuaries, and the open ocean (Pearsons 2008). The magnitude of competitive interactions may be influenced by the duration of cohabitation, environmental conditions (i.e., water temperature, discharge, productivity, habitat complexity), and the speed with which hatchery fish emigrate to the ocean. Hatchery subyearling fall Chinook share a similar life history and ecological niche with wild conspecifics which increases the likelihood of competitive interactions (Pearsons 2008; Tatara and Berejikian 2012). Subyearling fall Chinook are released in May to mid-June when wild fall Chinook are present in the basin or beginning active migration (Connor et al. 2005; Strange and McCovey 2008; Arnsberg and Kellar 2013). Marginal river conditions at the time of release could intensify competition further by forcing hatchery and wild fish to share food and limited space in thermal refugia (Strange and McCovey 2008; California HSRG 2012). Effects of competition may be intensified in areas like the estuary where multiple species and stocks converge and reside concurrently for months at a time (Weitkamp et al. 2015). To minimize hatchery/wild fish interactions, there are a number of measures that hatchery managers may utilize or experiment with (e.g., releasing fewer fish, staggering releases, releasing fish at the appropriate size and time, releasing fish in active parr-smolt transformation, releasing fish downstream of species of concern; Kostow 2009).
15
References Anchor Environmental and Natural Resources Consultants. 2005. Evaluation and assessment of hatchery and wild salmon interactions in WRIA 9. Prepared for the WRIA 9 Steering Committee, Seattle, Washington. 89p. Arnsberg, B. D. and D. S. Kellar. 2013. Nez Perce Tribal Hatchery monitoring and evaluation
project: fall Chinook salmon (Oncorhynchus tshawytscha) supplementation in the Clearwater River Subbasin. Annual progress report to Bonneville Power Administration, Project number 1983-350-003, Portland, Oregon.
Banks, J. L. and E. M. LaMotte. 2002. Effects of four density levels on tule fall Chinook
salmon during hatchery rearing and after release. North American Journal of Aquaculture 64:24-33.
Bugert, R. M., G. W. Mendel, and P. R. Seidel. 1997. Adult returns of subyearling and yearling fall Chinook salmon released from a Snake River hatchery or transported downstream. North American Journal of Fisheries Management 17:638-651. California Hatchery Scientific Review Group (California HSRG). 2012. California hatchery review
project Appendix VIII: Iron Gate Hatchery fall Chinook program report. Prepared for the U.S. Fish and Wildlife Service and Pacific States Marine Fisheries Commission. June 2012. 100p.
Clarke, L. R., W. A. Cameron, and R. W. Carmichael. 2016. No evidence of increased survival or decreased straying from acclimating subyearling fall Chinook salmon to release locations in the Umatilla River of Oregon. North American Journal of Fisheries Management 36:161-166. Clarke, L. R., W. A. Cameron, and R. S. Hogg. 2015. Umatilla Hatchery monitoring and
evaluation. Annual progress report to Bonneville Power Administration, Project number 1990-005-00, Portland, Oregon.
Clarke, L. R., W. A. Cameron, and R. W. Carmichael. 2013. Density effects on subyearling fall Chinook salmon during hatchery rearing in raceways with oxygen supplementation and after release. North American Journal of Aquaculture 75:18-24.
Connor, W. P., J. G. Sneva, K. F. Tiffan, R. K. Steinhorst, and D. Ross. 2005. Two alternative juvenile life history types for fall Chinook salmon in the Snake River Basin. Transactions of the American Fisheries Society 134: 291-304.
16
Connor, W. P., S. G. Smith, T. Andersen, S. M. Bradbury, D. C. Burum, E. E. Hockersmith, M. L. Schuck, G. W. Mendel, and R. M. Bugert. 2004. Postrelease performance of hatchery yearling and subyearling fall Chinook salmon released into the Snake River. North American Journal of Fisheries Management 24:545-560.
DeHart, M. November 19, 2010. Breakdown of ocean-age of returning PIT-tagged adult fall
Chinook at Lower Granite Dam in 2010 [Memorandum]. Fish Passage Center, Portland, Oregon.
DeHart, M. October 29, 2009. Fall Chinook jack count 2009 [Memorandum]. Fish Passage Center, Portland, Oregon. DeHart, M. September 22, 2008. Chinook jack passage at Priest Rapids Dam [Memorandum]. Fish Passage Center, Portland, Oregon. Fowler, L. G. and J. L. Banks. 1980. Survival rates of three sizes of hatchery-reared fall Chinook Salmon. U.S. Fish and Wildlife Service Technology Transfer Series 80-3. Fowler, L. G., R. E. Burrows, B. D. Combs, and J. L. Banks. 1980. The effect of size and time of release of fall Chinook salmon fingerlings on adult survival. U.S. Fish and Wildlife Service Technology Transfer Series 80-3. Goudy, M. 2016. Yakama Nation “Yearling versus Subyearling” experimental rearing strategy
summary, YN Prosser Hatchery 2008-2013, Yakima River, YKFP Fall Chinook Project, September 20, 2016.
Hankin, D. G. and E. Logan. 2010. A preliminary analysis of Chinook salmon coded-wire tag
recovery data from Iron Gate, Trinity River and Cole Rivers hatcheries, brood years 1978-2004. Arcata (CA): Contract report prepared for the Hoopa Valley Tribal council. 65p.
Hankin, D. G. 1990. Effects of month of release of hatchery-reared Chinook salmon on size at
age, maturation schedule, and fishery contribution. Oregon Department of Fish and Wildlife, Informational Report 90-4. 42p.
Harstad, D. L., D. A. Larsen, and B. R. Beckman. 2014. Variation in minijack rate among hatchery populations of Columbia River Basin Chinook salmon. Transactions of the American Fisheries Society 143:768-778.
Hayes, M. C. and R. W. Carmichael. 2002. Salmon restoration in the Umatilla River: A study of
straying and risk containment. Fisheries 27(10):10-19.
17
Hegg, J. C., B. P. Kennedy, P. M. Chittaro, and R. W. Zabel. 2013. Spatial structuring of an evolving life-history strategy under altered environmental conditions. Oecologia 172:1017-1029.
Johnson, R.C., P.K. Weber, J.D. Wikert, M.L. Workman, R.B. MacFarlane. M.J. Grove, and A.K.
Schmitt. 2012. Managed metapopulations: Do salmon hatchery ‘sources’ lead to in-river ‘sinks’ in conservation? PLoS ONE 7(2):e28880. doi:10.1371/journal.pone.0028880.
Keefer, M. L. and C. C. Caudill. 2014. Homing and straying by anadromous salmonids: a review
of mechanisms and rates. Reviews in Fish Biology and Fisheries 24:333-368. Kostow, K. 2009. Factors that contribute to the ecological risks of salmon and steelhead hatchery programs and some mitigating strategies. Reviews in Fish Biology and Fisheries 19:9-31. Marsh, D. M., J. R. Harmon, N. N. Paasch, K. L. Thomas, K. W. McIntyre, W. D. Muir, and W. P.
Connor. 2007. A study to understand the early life history of Snake River Basin fall Chinook salmon. Annual report to the Walla Walla District Northwestern Division U.S. Army Corps of Engineers, Washington.
Martin, R. M. and A. Wertheimer. 1989. Adult production of Chinook salmon reared at different densities and released as two smolt sizes. The Progressive Fish-Culturist 51:194-200. Milks, D., M. Varney, and M. Schuck. 2009. Lyons Ferry Hatchery evaluation fall Chinook salmon annual report: 2006. Washington Department of Fish and Wildlife, Olympia, Washington. Report #FPA 09-04. Miller, J. A., A. Gray, and J. Merz. 2010. Quantifying the contribution of juvenile migratory
phenotypes in a population of Chinook salmon Oncorhynchus tshawytscha. Marine Ecology Progress Series 408: 227-240.
Muir, W. D. and T. C. Coley. 1996. Diet of yearling Chinook salmon and feeding success during downstream migration in the Snake and Columbia Rivers. Northwest Science 70:298305. Myers, J. M., R. G. Kope, G. J. Bryant, D. Teel, L. J. Lierheimer, T. C. Wainwright, W. S. Grant, F. W. Waknitz, K, Neely, S. T. Lindley, and R. S. Waples. 1998. Status review of Chinook salmon from Washington, Idaho, Oregon, and California. U.S. Dept. Commer., NOAA Tech. Memo. NMFS-NWFSC-35, 443 p.
18
Naman, S. W. and C. S. Sharpe. 2012. Predation by hatchery yearling salmonids on wild subyearling salmonids in the freshwater environment: A review of studies, two case histories, and implications for management. Environmental Biology of Fishes 94:21-28. Pearsons, T. N. 2008. Misconception, reality, and uncertainty about ecological interactions and risks between hatchery and wild salmonids. Fisheries 33:278-290. Pearsons, T. N. and A. L. Fritts. 1999. Maximum size of Chinook salmon consumed by juvenile Coho salmon. North American Journal of Fisheries Management 19:165-170. Quinn, T. 1997. Homing, straying, and colonization. In: Genetic effects of straying of non-native
hatchery fish into natural populations: Proceedings of the workshop. NOAA Technical Memorandum NMFS-NWFSC-30.
Rosenberger,S., W. Young, D. Milks, B. Arnsberg, and D. Wickard. 2017. Snake River hatchery
fall Chinook salmon age-at-release performance evaluation white paper. Idaho Power, Nez Perce Tribe, and Washington Department of Fish and Wildlife, January 2017.
Seidel, P. R. and S. B. Mathews. 1977. 1971-72 brood fall Chinook time/size at release study.
Washington Department of Fisheries, Service Contract Report 777. 36p. Sholes, W. H. and R. J. Hallock. 1979. An evaluation of rearing fall-run Chinook salmon, Oncorhynchus tshawytscha, to yearlings at Feather River Hatchery, with a comparison of returns from hatchery and downstream releases. California Fish and Game 65:239-255. Strange, J. and B. W. McCovey, JR. 2008. Fish release strategies at Iron Gate Hatchery: 2007 fall yearling Chinook salmon emigration behavior. Yurok Tribal Fisheries Program, Final Technical Memorandum. 11p. Tatara, C. P. and B. A. Berejikian. 2012. Mechanisms influencing competition between hatchery and wild juvenile anadromous Pacific salmonids in fresh water and their relative competitive abilities. Environmental Biology of Fishes 94:7-19. Tipping, J. M. 2011. Effect of juvenile length on Chinook salmon survivals at four hatcheries
in Washington State. North American Journal of Aquaculture 73:164-167.
U.S. Fish and Wildlife Service (USFWS). 2007. Carson, Spring Creek, Little White Salmon, and Willard National Fish Hatcheries assessments and recommendations. Final report from the Columbia River Basin Hatchery Review Team, Pacific Region Fishery Resources, Portland, Oregon. https://www.fws.gov/pacific/fisheries/Hatcheryreview/index.cfm VØllestad, L. A., J. Peterson, and T. P. Quinn. 2004. Effects of freshwater and marine growth rates on early maturity in male Coho and Chinook salmon. Transactions of the American Fisheries Society 133:495-503.
19
Warner, G.H., D. H. Fry, Jr., and A. N. Culver. 1961. History of yearling king salmon marked and
released at Nimbus Hatchery. California Fish and Game 47:343-355. Weber, E.D. and K.D. Fausch. 2003. Interactions between hatchery and wild salmonids in
streams: differences in biology and evidence for competition. Canadian Journal of Fisheries and Aquatic Sciences 60:1018-1036.
Weitkamp, L. A., D. J. Teel, M. Liermann, S. A. Hinton, D. M. Van Doornik, and P. J. Bentley. 2015. Stock-specific size and timing at ocean entry of Columbia River juvenile Chinook salmon and steelhead: Implications for early ocean growth. Marine and Coastal Fisheries: Dynamics, Management, and Ecosystem Science 7:370-392. Westley, P. A. H., T. P. Quinn, and A. H. Dittman. 2013. Rates of straying by hatchery-produced
Pacific salmon (Oncorhynchus spp.) and steelhead (Oncorhynchus mykiss) differ among species, life history types and populations. Canadian Journal of Fisheries and Aquatic Sciences 70:735-746.
Williams, J. G., R. W. Zabel, R. S. Waples, J. A. Hutchings, and W. P. Connor. 2008. Potential for
anthropogenic disturbances to influence evolutionary change in the life history of a threatened salmonid. Evolutionary Applications 1:271-285.
Williamson, K.S., A.R. Murdoch, T.N. Pearsons, E.J. Ward, and M.J. Ford. 2010. Factors influencing the relative fitness of hatchery and wild spring Chinook salmon (Oncorhynchus tshawytscha) in the Wenatchee River Washington, USA. Canadian Journal of Fisheries and Aquatic Sciences 67:1840-1851.
Young, W., D. Milks, S. Rosenberger, B. Sandford, and S. Ellis. 2013. Snake River fall Chinook salmon run reconstruction. Lower Snake River Compensation Project, Fall Chinook Salmon Review. Clarkston, Washington. Zimmerman, C. E., R. W. Stonecypher, JR, and M. C. Hayes. 2003. Migration of precocious male hatchery Chinook salmon in the Umatilla River, Oregon. North American Journal of Fisheries Management 23:1006-1014.
20
U.S. Fish and Wildlife Service Columbia River Fish and Wildlife Conservation Office 1211 SE Cardinal Court, Suite 100 Vancouver, WA 98683
April 2017 www.fws.gov/columbiariver
