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21 April 2013
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Chinook Salmon Management: A Model Based Approach
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STEVEN GRIFFITH, The Pennsylvania State University, Atherton Street, State College, PA
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Steven Griffith
The Pennsylvania State University
Atherton Street, State College, PA 16801
555-555-5555
jek5222@psu.edu
James Korman
The Pennsylvania State University
Atherton Street, State College, PA 16801
555-555-5555
slg5338@psu.edu
Andy Severns
The Pennsylvania State University
Atherton Street, State College, PA 16801
555-555-5555
ajs5929@psu.edu
RH: Griffith et al. • Chinook Salmon Management
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JAMES KORMAN, The Pennsylvania State University, Atherton Street, State College, PA
16801
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ANDY SEVERNS, The Pennsylvania State University, Atherton Street, State College, PA 16801
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ABSTRACT
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There are a series of eight dams that obstruct downward and upstream movement of Chinook
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salmon on the Snake and Columbia rivers. We explored alternatives action other than the status
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quo and dam removal as potentials to increase the endangered Chinook salmon Oncorhynchus
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tshawytscha population in the Marsh Creek sub basin of the Snake River. Those two actions
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were: (1) summer flow augmentation and (2) the removal of non-native predators. Both actions
Griffith et al. 2
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were aimed at increasing egg to smolt survival rate. Summer flow augmentation increased
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survival egg-smolt survival by 15% and non-native predator removal increased egg-smolt
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survival by 23%. Our original matrix model with no management applications yielded a lambda
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of 0.90. With summer flow augmentation, lambda increased to 0.92 and with non-native
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predator removal, lambda increased to 0.94.
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KEY WORDS Chinook salmon, Oncorhynchus tshawytscha, Snake River, Columbia River,
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matrix model, flow augmentation, predator removal,
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Griffith et al. 3
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The Chinook salmon is an anadromous fish species. It spawns in freshwater in the
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spring/summer and the fry then migrate to coast and grow in the saltwater. The yearlings take up
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to 3 months until they migrate to the coast and some stay as long as three years in the freshwater,
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but most only stay about a year (Morrow 1980). They then spend up to 8 years growing in the
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saltwater before they return to their natal freshwater rivers to spawn and die. Their distributions
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are located mostly along the west coast of North America from the Bering Strait in Alaska to
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California and have even been located in the Japanese Islands according to NOAA Fisheries
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website. The Chinook salmon’s demographic data is compiled into age classes because they only
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spawn once a year and once a lifetime. The salmon have the potential to start to spawn at age 2
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when they migrate to their natal streams, but some salmon stay in their saltwater environment
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and do not migrate to spawn until age 8. Spawning occurs most commonly at ages 4-7(Savereide
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and Quinn 2004). The statuses of some of the populations of Chinook salmon have been marked
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as a “species of concern” to an “endangered” status by the Endangered Species Act. This is due
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mostly from anthropologic activities. According to Idaho Fish and Game, historical data suggests
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the Chinook salmon population of the Snake River have been in numbers in excess of 1,000,000,
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and recent data show that this abundance has declined to about 55,000.
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There is not a single activity that is causing the declining populations, but the activities
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with the most impact would be commercial fishing and impeded migration due to damming
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according to the NOAA Fisheries website. The damming of the Snake River has been thought to
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play a major role in the decline of survivorship and low reproduction rates of the Chinook
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salmon. The juveniles have impeded migration to the coast, and the adults have impeded
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migration back to their spawning grounds. There have been recent activities that have increased
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the abundance. The Snake River population reached a low in the early 1990’s of about 2,500, but
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has increased to 55,000 in recent years. The management actions currently in place include fish
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ladders for returning adults, juvenile collection and manually moving down the river, and
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stocking hatchery raised juveniles. Although, population trends have shown a growth in
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population, with the current survivorship and reproduction, the population will decline.
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There is a possibility of increasing the population growth with further management
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actions. Summer flow augmentation has been shown to have a positive effect on the survivorship
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of sub-yearling Chinook (Conner et al. 2003). The multiple dams that are currently in place have
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an impact of the hydrology of the river. The increased temperature and decreased flow decrease
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the survivorship of the salmon. Multiple reservoirs are opened along the Snake River and have
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shown to decrease temperature and increase flow. This results in an increase in survivorship of
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sub-yearling in years with summer flow augmentation by 15% (Conner et al 2003). Another
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possible management action would be a removal of non-native predatory fish. This method has
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shown to have an increase in survivorship by 23% ( Cavallo et al. 2012).
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This study combines data of recent populations’ age class survivorship and fecundity to
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model population growth. The goal of the study is to model possible management options that
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will result an increase of the Chinook salmon population by 10%. To do this we will model the
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population resulting from a status quo action, also model the population from using summer flow
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augmentation, and model the population after predator removal.
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STUDY AREA
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The matrix model data for status quo was from a study by Kareiva et. al. 2000 that took place on
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the Snake River in Idaho. The study was concentrated around four major dams on the river. A
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study researching the effects of flow augmentation took place at 10 different sites along the
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Snake River in Idaho. To monitor effects of predator removal a study by Connor et al. 2003 took
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place on the North Fork Mokelumne River which included a 1.6 km removal site.
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METHODS
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Data regarding demographic rates were gathered from Kareiva et al. 2000. From this data, we
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constructed an age-based matrix model with a pre-breeding census. Demographic rates are
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represented by brood years 1990-1994 (Kareiva et. al. 2000). Propensity to spawn was
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calculated into the survival rates of salmon who had the potential to be reproductively mature
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(ages 3-5). Fecundity was calculated using numerous variables: the number of eggs per female,
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propensity to breed, age specific survival, and their upstream movement survival. We looked at
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ways to alleviate stress and increase the growth rate of the population. The two best methods
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were summer flow augmentation and the removal of non-native predators. Summer flow
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augmentation increased survival by 15% and the removal of non-native predators increased the
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survival by 23% (Cavallo et al. 2012; Connor et al. 2003) We estimated the effects of summer
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flow augmentation in our model by increasing the survival of age 1 by 15%. We estimated the
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effects of removing non-native predators by increasing the survival of age 1 (the most predated
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on) by 23%. We compared the three models amongst each other and made conclusions amongst
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them.
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RESULTS
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The results show the populations decline will be less when summer flow augmentation and
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predator removal are implemented. Figure 1 shows the abundance of Chinook salmon projected
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10 years with actions of status quo, summer flow augmentation, and predator removal. The data
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collected shows that the population has a declining growth rate with an asymptotic lambda of
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0.90. With the increases in survivorship from either management, neither appears to be able to
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make the population be stable or increase. Removal of the predators had the greatest increase of
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survivorship with an increase of 23% in subyearling salmon. This resulted in largest asymptotic
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lambda of 0.94. The summer flow augmentation had an increase in survivorship of 15% and this
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resulted in an increased asymptotic lambda to 0.92. The model shows that if there would be no
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management actions, there would be a 64% decrease in 10 years. Predator removal shows a
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decrease of 45% in ten years. Summer flow augmentation shows a decrease of 52% in ten years.
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DISCUSSION
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The matrix created to model status quo was from a study done by Kareiva et. al. 2000 which
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incorporated 5 age classes. Individuals were modeled to reproduce at age 3, 4, or 5 and die after
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reproduction. Therefore no individuals live past age 5. When we modeled status quo with
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demographics also found in Kareiva et. al. 2000 we calculated an asymptotic lambda of .90
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indicating a current declining population.
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To model our first alternative action we found data from a study by Connor et al. 2003
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which indicated that summer flow augmentation increased the survivorship of sub-yearling
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salmon. The increase in the rate of flow is to aid the return of sub-yearling salmon to the ocean at
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a faster rate. This increase also increases survival of sub-yearling salmon by as much as 23% but
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on average 15% by increasing passage and decreasing predation (Connor et al. 2003). We used
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the 15% average increase in survival to modify our matrix by increasing our value for age class
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one contributing to age class two by 15%. That then resulted in our asymptotic lambda changing
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to .92 which demonstrates an increase in our lambda value and a slower rate of decline of the
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population.
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The second and more productive alternative action was predator removal. In a study by
Cavallo et al. 2012 predators were removed by method of boat electrofishing in order to study
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the effects of predation on sub-yearling salmon. The study found that after removing non-native
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predators from a study site sub-yearling survival increased 23%. We used this increase of 23%
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to modify our matrix by increasing our value for age class one contributing to age class two by
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23%. This change resulted in an asymptotic lambda value of .94 which was the highest lambda
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value we achieved with our alternative actions.
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MANAGEMENT IMPLICATIONS
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The approach we used to estimate increases in Chinook salmon populations can be used by
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managers to project changes in abundance for upcoming years. Our approaches to increase
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survival may be pertinent to other species of pacific salmon facing similar problems. As an
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alternative to dam removal or the status quo, managers can target flow augmentation and non-
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native predator removal during peak times of migration. Our approach found the greatest impact
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on increasing growth rate was at by targeting the survival rate of age 0 – age 1 according to our
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matrix model. Other managers can take the approach of targeting this age class using other
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methods to increase their survival.
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LITERATURE CITED
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Cavallo, B., Merz, J., and Setka, J. 2012. Effects of predator and flow manipulation on Chinook
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salmon (Oncorhynchus tshawytscha) survival in an imperiled estuary. Environmental
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Biology of Fishes DOI: 10.1007/s10641-012-9993-5
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Connor, W. P.; Burge, H. L.; Yearsley, J. R.; Bjornn, T. C. 2003. Influence of flow and
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temperature on survival of wild subyearling fall chinook salmon in the Snake River.
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North American Journal of Fisheries Management 23:362-375.
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Kareiva, P., M. Marvier, and M. McClure. 2000. Recovery and management options for
spring/summer chinook salmon in the Columbia River basin. Science 290:977-979.
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Morrow, J. E., 1980. The freshwater fishes of Alaska. University of. B.C. Animal Resources
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Ecology Library 16:248-249
Savereide, J. W., and T. J. Quinn. 2004. An age-structured assessment model for chinook
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salmon (Oncorhynchus tshawytscha). Fish Aquatic Science 61:974-985
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Table 1. Projection for female Snake River Chinook Salmon
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1
0
0.013075754
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0
0
2
0
0
0.8
0
0
Age (years)
3
0.326169151
0
0
1.23375
0
4
5.015714444
0
0
0
1.05125
5
39.66474481
0
0
0
0
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Figures
Figure 1. Abundance of Snake River Chinook salmon projected from current year (0) to ten
years with summer flow augmentation and predator removal management actions.
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Figure 1.
60000
Abundance
50000
current
40000
30000
Predator removal
20000
Summer flow
augmentation
10000
both
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0
2
4
6
Years
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10
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