Feasibility of Fish Passage at Alameda Creek Diversion Dam

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Feasibility of Fish Passage at Alameda Creek Diversion Dam7.1.1 PROVIDE ACCESS TO ADDITIONAL QUANTITY OFHABITAT TO INCREASE NATURAL PRODUCTIONAs described in Section 6.1, detailed data regarding the extent and suitability of steelhead spawningand rearing habitat above ACDD are limited. From what is known of the habitat above ACDD,however, it appears that there is sufficient habitat to increase natural steelhead production to levelsabove what could be achieved without access to this habitat. The ACDD Fish Ladder option wouldlikely meet this goal, although future study of upstream habitat is merited, especially in conjunctionwith further design analysis of passage at ACDD.7.1.2 CONTRIBUTE TO SPECIES RECOVERY THROUGHINCREASED NATURAL PRODUCTIONPassage design components should maximize capture efficiency and minimize stress due to handling,in order to result in a long-term spawner replacement ratio of greater than 1:1 (see Section 6.2). Withthe ACDD Fish Ladder option, passage-related productivity would depend primarily on ladderefficiency. Assuming the ladder is well designed, efficiency is expected to be high and losses areexpected to be minimal. It is likely that this option would increase natural production, potentiallycontributing to species recovery.7.1.3 PROVIDE ACCESS TO HISTORICAL HABITATHistorically, the steelhead population in the Alameda Creek Watershed was probably functionallyindependent of populations in other watersheds (Spence et al., 2008), although population estimatesare not available (Leidy et al., 2005). The presence of a possible impediment to fish migration, LittleYosemite, below ACDD in Alameda Creek (see Sections 2.3.1 and 6.1), may raise questions aboutthe frequency at which habitat above ACDD was historically accessible to immigrating steelhead.Historic coastal steelhead populations in the Alameda Creek Watershed are adapted to streams withhighly variable flow conditions, however, and steelhead populations do not need access to the oceanevery year to persist (Gunther et al., 2000). The degree to which habitat above Little Yosemite (andACDD) was historically accessible could possibly be determined by genetic evaluation of O. mykissin the Alameda Creek Watershed from above and below Little Yosemite. A study of genetic diversityin O. mykiss populations from the Russian River basin found that fish above dams were similar tothose from below-barrier sites but fish above natural barriers were highly divergent and hadsignificantly lower genetic diversity (Deiner et al., 2007), presumably due to long-standing isolationfrom populations below the barriers.7.1.4 PROTECT OR ENHANCE THE GENETIC INTEGRITYAND/OR DISTINCTNESS OF STOCKSHeritable genetic variation is the basis for evolutionary change and is essential if natural selection isto operate. Genetic diversity exists at three fundamental levels: genetic variation within individuals(heterozygosity), genetic differences among individuals within a population, and genetic differencesamong populations. Populations can exist from an extreme of complete isolation and no geneticexchange with other populations, to the opposite extreme of free genetic exchange amongpopulations. Meffe et al. (1997) suggest the following guidelines for genetically based conservationpractices:1. Large genetically effective population sizes are better than small ones because they will losegenetic variation more slowly.ACDD Passage June 2009 Page 7-2
7.0 Evaluation of the Biological Benefit of Two Passage Options2. The negative effects of genetic drift and inbreeding are inversely proportional to population size.Thus, avoid managing for small population sizes.3. Management of wild populations should be consistent with the history of their genetic patternsand processes. For example, historically isolated populations should remain isolated unless otherconcerns dictate that gene flow must occur. Gene flow among historically connected populationsshould continue at historical rates, even if that calls for assisted movement of individuals.Sufficient life-history diversity must exist to sustain a population through short-term environmentalperturbations and to provide for long-term evolutionary processes. The metrics and benchmarks forevaluating the diversity of a population should be evaluated over multiple generations and include:1. The proportion of the diversity of a life-history trait or traits that existed historically that aremaintained in the existing population.2. The historic (natural) levels and origins of gene flow and genetic diversity relative to the existingpopulation.3. The degree to which the existing population successfully uses available habitats.4. The resilience of the existing population, and its ability to adapt to environmental fluctuations.Review of the fisheries literature suggests that a minimum of 100 breeding pairs of steelhead wouldensure sufficient genetic diversity for a genetically viable population (Langston and Zemlak, 1998)(see Section 6.2).A rainbow trout population currently exists in the Upper Alameda Creek Sub-Watershed. Despiterecent isolation and some stocking, the genome of the historic steelhead population is expected to befairly well preserved in populations isolated above ACDD. Limited genetic research conducted byNielsen (2003) suggests that this population is closely related to Central California Coast steelheadand is likely composed primarily of the isolated, historic steelhead population. Although isolation ofa small population can result in genetic drift and a reduction in genetic fitness (Campbell et al., 1999),Deiner et al. (2007) report that construction of modern dams does not appear to have isolatedO. mykiss populations for long enough to result in a loss of genetic diversity. The East Bay RegionalPark District reports that private property owners have intermittently planted rainbow trout below theOhlone section of upper Alameda Creek for 50 years prior to 1995 (Leidy et al., 2005), and the originof these trout is unknown. Studies conducted in nearby Santa Clara Valley streams, however, suggestthat stocking has had little effect on the genetic composition of most San Francisco Estuary streamO. mykiss (Garza and Pearse, 2008). While steelhead access to the area has been blocked for manyyears, rainbow trout above ACDD likely retain most of the unique genetic character of nativesteelhead, despite prior stocking of hatchery rainbow trout.Facilitating fish passage could potentially introduce some out-of-basin genetic stocks to upperAlameda Creek. Considering the number of hatchery steelhead produced in the Central Valley, thereis a potential for some fish from the California Central Valley DPS to stray into Alameda Creek.However, maintaining a population of at least 100 breeding pairs of steelhead in the Alameda CreekWatershed should allow for adequate within basin genetic diversity. Meffe and Carroll (1997) reportthat some level of gene flow among connected populations is desirable. Some low level of strayingmay even increase the genetic diversity and fitness of the population. Facilitating gene flow amongO. mykiss isolated above ACDD and other O. mykiss populations in the Alameda Creek Watershed(through the provision of passage at ACDD and elsewhere in the watershed) may have a positiveACDD Passage June 2009 Page 7-3
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T E C H N I C A L M E M O R A N D U
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Feasibility of Fish Passage at Alam
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1.0 Introduction1 INTRODUCTION1.1 B
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24Alamo680DanvilleAlameda CreekWate
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oleyriesSanCalaveras Creekalaveras
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(a)(b)Alameda Creek Diversion Dam (
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2.0 Setting2.3.2.1 ALAMEDA CREEK DI
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2.0 Settingalmost never submerged;
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2.0 SettingRainbow trout are the sa
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2.0 SettingA number of future proje
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Page 91 and 92: 10.0 References10 REFERENCESAACE (A
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Feasibility of Fish Passage at Alameda Creek Diversion Dam

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