Predator Fish Monitoring at Installed Large Wood Structures – Sammamish River Habitat Enhancement Projects Redmond, Washington RMDX 0000-0047 Prepared for: City of Redmond Public Works Department Redmond, Washington 98073 Prepared by: David Evans and Associates, Inc. 415 118th Avenue Southeast Bellevue, Washington 98005 October 2007 Table of Contents 1.0 Introduction............................................................................................................. 1 1.1 Study Area.......................................................................................................... 1 2.0 Methods................................................................................................................... 3 3.0 Results.....................................................................................................................5 4.0 Conclusions............................................................................................................. 8 5.0 References............................................................................................................... 9 List of Tables Table 1. Date, time, and water temperature during snorkeling and angling surveys.......... 5 Table 2. Species captured and date of capture during angling surveys. ............................. 5 Table 3. Stomach contents of captured predatory fish........................................................ 6 Table 4. Date and number of each species observed during snorkel surveys within all reaches.................................................................................................................. 6 Table 5. Number and percent of fish species associated with installed wood structures within Reaches 2-4............................................................................................... 7 Figures Figure 1. Predator Study ..................................................................................................... 2 Figure 2. Predator Study ..................................................................................................... 4 List of Appendices Appendix A: Literature Review Appendix B: Photographs P:\r\RMDX00000047\0600INFO\EP\Report\07-1026_Predator Study Report.doc Predator Fish Monitoring October 2007 Sammamish River Habitat Enhancement Projects Page i Abbreviations and Acronyms cm centimeters DEA David Evans and Associates, Inc. HEP Habitat Enhancement Project RWMP River Walk Master Plan WDFW Washington Department of Fish and Wildlife WRIA Water Resource Inventory Area P:\r\RMDX00000047\0600INFO\EP\Report\07-1026_Predator Study Report.doc Predator Fish Monitoring October 2007 Sammamish River Habitat Enhancement Projects Page ii Executive Summary This report summarizes efforts to determine predation of juvenile salmon around installed large wood structures on a rehabilitated reach of the Sammamish River in Redmond, Washington. David Evans and Associates, Inc. biologists angled and snorkeled during May 2007 in the study area to accomplish the goals of this project. The goals of this project include: Conduct a brief review of existing information relating to predator fish/juvenile salmon interactions. Determine predation of juvenile salmon by fish within the study area. Determine presence of juvenile salmon fish predators around installed wood structures. Predators observed in the study area included northern pikeminnow (Ptychocheilus oregonensis), smallmouth bass (Micropterus dolomieui), cutthroat trout (Oncorhynchus clarki), rainbow trout (O. mykiss), and sculpin sp. (Cottus sp.). Cutthroat trout, rainbow trout, and sculpin sp. were all less than 200 millimeters long and likely did not prey on juvenile salmon. We did not find a large percentage of predators or juvenile salmon associating with installed large wood structures. Northern pikeminnow and smallmouth bass were greater than 9.5 inches (24 centimeters) and were capable of eating juvenile salmon. However, we did not find any juvenile salmon in the stomach contents of 26 northern pike minnow and 2 smallmouth bass. Although northern pike minnow were abundant, their stomach contents were generally empty. All of the captured northern pikeminnow were gravid and were on a spawning migration. Considering the results of this study and the fact that most of the juvenile salmon migrate past the study area before June (i.e. before water temperatures are high enough for increased predation), and that most of the juvenile salmon are greater than 3 inches (7.5 centimeters—a large enough size to avoid predation), it is likely predation in the study area during May is low and not influenced by installed wood structures. P:\r\RMDX00000047\0600INFO\EP\Report\07-1026_Predator Study Report.doc Predator Fish Monitoring October 2007 Sammamish River Habitat Enhancement Projects Page iii 1.0 Introduction This report summarizes efforts to determine predation of juvenile salmon around installed large wood structures on a rehabilitated reach of the Sammamish River (Figure 1). The City of Redmond has implemented several Habitat Enhancement Projects (HEPs) as phases of the River Walk Master Plan (RWMP), resulting in rehabilitation of habitat in several reaches of the Sammamish River and adjacent uplands (Appendix A). During the permit approval process for the most recent HEP phase, questions arose regarding the benefits of installed large wood structures on a relatively warm, slow moving river system such as the Sammamish River. Agency staff was concerned about the possibility that large wood structures may provide shelter for piscivorous fish which may prey on juvenile salmon migrating downstream. In response, the City of Redmond authorized David Evans and Associates, Inc. (DEA) to investigate predator use and predation of juvenile salmon in and around installed large wood structures. The goals of this project include the following: Conduct a brief review of existing information relating to predator fish/juvenile salmon interactions (Appendix B). Determine predation of juvenile salmon by predators within the study area. Determine presence of juvenile salmon predators around installed wood structures. We accomplished these goals by: Angling near installed wood structures; Snorkeling reaches with installed wood structures. 1.1 Study Area The Sammamish River is part of Water Resource Inventory Area (WRIA) 8 located in Central Puget Sound (Figure 1). The Sammamish River connects Lake Sammamish with Lake Washington. It is a low gradient river with dense aquatic vegetation (Elodea sp. and Myriophylum sp.) in the spring and summer months. In the summer, water temperatures regularly exceed 68 degrees Fahrenheit (20 degrees Celsius). The river is channelized, straightened, and lacks woody structures. Despite these habitat deficiencies, the Sammamish River and its major tributary, Bear Creek, support runs of wild anadromous salmonids, including Chinook salmon (Oncorhynchus tshawytscha), that are listed as threatened under the Endangered Species Act. P:\r\RMDX00000047\0600INFO\EP\Report\07-1026_Predator Study Report.doc Predator Fish Monitoring October 2007 Sammamish River Habitat Enhancement Projects Page 1 Figure 1. Predator Study amma S m i s h R i v e r Project Location Puget Sound k e e r C r a Be L a k e L a W k e a s S h a i m Elliott Bay g n m t a o m n i s h I s s a q u a h C r e e k Legend Predator Study City of Redmond Watebody Snohomish County Streams ¯ City of Redmond RMDX00000047 0369121.5 Figure 1 Kilometers October 2007 P:\r\RMDX00000047\0600INFO\EP\Report\07-1026_Predator Study Report.doc Predator Fish Monitoring October 2007 Sammamish River Habitat Enhancement Projects Page 2 There is also a hatchery located upstream of the study area on Issaquah Creek. This hatchery produces coho (O. kisutch) and Chinook salmon. Approximately 500,000 Coho salmon averaging 5 to 6 inches (12.7 to 15.2 centimeters [cm]) long and 2,000,000 Chinook salmon averaging 3 inches (7.6 cm) long are released each year. 2.0 Methods DEA biologists angled and snorkeled during the month of May in the study area to accomplish the goals of this project. The study area included the Sammamish River near river mile 11 (17.7 kilometer), near the bridge crossings of NE 85th Street and NE 90th Street (Figure 2). We timed our snorkel events to coincide with the peak outmigration of juvenile Chinook salmon from Bear Creek. Bear Creek is approximately one kilometer upstream of the study area. Previous years of monitoring by Washington Department of Fish and Wildlife (WDFW) showed the peak outmigration of juvenile Chinook salmon occurred in May (WDFW 2005; WDFW 2006; WDFW 2007). Primary releases of Chinook juveniles from a hatchery on Issaquah Creek (also upstream) occur slightly later than the Bear Creek timing. In 2007, most of the hatchery releases occurred in late May and early June (personal communication with Issaquah Salmon Hatchery manager). Angling included hook and line sampling in the evening and morning. Angling consisted of: Two anglers spin casting lures in areas with good bank access (Reach 2 and 3); Landing predators and euthanizing them for stomach content analysis; Analyzing stomach content which included cutting out and opening the digestive tract from the esophagus to the anus; Identifying stomach contents and storing in ethanol. We snorkeled four 328-foot (100 meter) reaches. Reach 1 is downstream of any rehabilitated reaches in the RWMP and did not include any installed wood structures. Reaches 2, 3, and 4 are between the bridge crossings