Suitability Comparison of Two Potential Putah Creek Salmon Habitats

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1 Suitability Comparison of Two Potential Putah Creek Salmon Habitats Jody Baugh ENVS 121 Field Methods in Environmental Science Instructor: Catherine Ishikawa Fall,

2 Abstract Putah Creek was once a vital part of the Chinook salmon life cycle. In recent years, changes to the creek and surrounding areas may have led to its reduced suitability as prime salmon habitat. Our research team took water quality measurements at two separate Putah Creek sites in an effort to compare them for Chinook salmon habitability. Dissolved oxygen levels, ph, water temperature and alkalinity were measured according to SWAMP and EPA standard water quality methods. Alkalinity was measured using a weak acid titration kit; water velocity was measured using a bucket meter, and substrate categorized with the Wolman Pebble count procedure. The mean DO, ph, temperature and alkalinity collected for Site A were compared to those collected from Site B. Our results show that neither site is an optimal Chinook salmon habitat at this point in time due to multiple unacceptable parameters. In particular, temperatures were above the preferred range for salmonids at both sites, ph levels were elevated above suitable levels at Site A and DO levels at Site B were only 0.25 mg/l above the minimum threshold required by Chinook salmon. More research needs to be done over a larger span of the creek and at different times of the year to account for seasonal changes. Water allocations from the dams and obstacles to spawning such as beaver dams should also be taken into account to gain a better understanding of whether or not Putah Creek has any suitable habitat available for Chinook salmon. Introduction The headwaters of Putah Creek originate in the Mayacamas Mountain Range on the east side of Cobb Mountain. The creek is part of a greatly altered watershed that is roughly 70 miles long. It is regulated both by the Monticello Dam and the Solano Diversion Dam (Putah Creek Council, 2

3 2012). The Monticello Dam allocates the amount of water that is released from the bottom of Lake Berryessa, which is approximately 50 miles northwest of our research site. After the water is released from the lake it must pass over the Solano Diversion Dam, 22 miles from our research site, as well as pass beaver dams and other obstacles along the way (U.S. Department of the Interior, 2004). These dams not only affect temperature and flow by restricting water levels, but they also restrict the levels of gravel and pebbles that would normally be deposited throughout the rest of the creek. One of the most noticeable negative results of water flow alteration to streams, rivers and creeks like Putah Creek is a change in or even a collapse of fish populations (Marchetti & Moyle, 2001). Chinook salmon were once a natural part of the meandering Putah Creek system before the dams, levees and subsequent channelization altered it beyond recognition. Since these changes have taken place, Chinook have become rare visitors to the areas in which they used to spawn regularly. Since so many variables influence the life histories of salmon, it is difficult to pinpoint which factors have caused the Chinook to discontinue the use of Putah Creek as their habitat. Water quality measurements are beneficial because they may help to explain some of the ways in which Putah Creek has become an unattractive habitat or spawning ground for the Chinook. Our research team compared multiple water quality parameters of two separate sites within Putah Creek in an effort to determine which of them may provide a more suitable Chinook salmon habitat if they were to return. Methods Site A is located at the UC Davis Putah Creek Riparian Reserve under the Interstate 80 overpass in Davis, California ( N W), at an approximate elevation of 9 meters 3

4 above sea level. Tests were conducted at this site on Friday, 5 October Site B is located in the Putah Creek South Fork Preserve off of Mace Blvd, south of Davis, California ( N W), at an approximate elevation of 8.5 meters above sea level. Tests were conducted at this site on Saturday, 6 October The climate is Mediterranean, the soils alluvial and the vegetation riparian at both sites. A trip blank that was prepared ahead of time was brought out to each of the sites. A field blank was also used to assure there was no contamination during the tests. Once at the site, we performed a self calibration with the dissolved oxygen meters and calibrated ph meters with ph 7 and ph 10 buffers. The ph measurements were taken in stream and the meters were also used to measure water temperature. Alkalinity was measured using a weak acid titration kit. Each group used the meters and titration kit to take two replicates separately for each parameter from the creek using SWAMP and EPA standard water quality condition measurement methods (CA EPA WRCB, 2012). For sediment size distribution measurements we used the Wolman Pebble count procedure (Wolman, 1954). Once the water quality measurements were completed all of the teams measured flow using two separate methods. The first method used was with a bucket meter applied at 1 m or 2 ft intervals across the creek; the second flow measurement was taken using the floating object method with a pinecone (CA EPA WRCB, 2012). Because water velocity is often overestimated by the floating object method due to differences in surface velocity and water velocities at depth, the results of these measurements were disregarded for the purposes of this comparison. Electrical conductivity was also measured, however because the direct effects of 4

5 electrical conductivity on salmonids has not been clearly defined, these results were also disregarded for the purposes of this study. Results The pebble count data gathered at Site A of Putah Creek yielded particle sizes that spanned the full range of greater than 128 mm to less than 2 mm (Figure 1). The median pebble size for Site A was mm. The pebble count data gathered at Site B of Putah Creek yielded particle sizes from 0.06 mm to 128 mm. The median pebble size for Site B was 9.14 mm. The D50 was 14 mm at Site A while the D50 at Site B was 14.5 mm Cumulative Percent (%) Site B Site A Particle Size (mm) Figure 1: Putah Creek particle size distribution comparison for Sites A and B. 5

6 The average flow measured with the meter for Site A was ± 0.3 ft/s and the average flow measured with the meter for Site B was ± 0.23 ft/s. The average velocity at a mean depth of ± 0.3 cm at Site B was ± 0.3 cm/s and the average velocity at a mean depth of ± 3.5 cm for Site A was ± 2.8 cm/s. The mean temperature, mean ph and mean dissolved oxygen (DO) for Site A were all higher than the mean temperature, mean ph and mean DO measurements of Site B. Mean alkalinity for Site A was lower than that of Site B. Table 1. Means of chemical data for each Putah Creek site. Putah Creek Site Temperature ( C) ph DO (mg/l) DO (% sat) Alkalinity (mg/l CaCO₂) A ± ± ± ± ± 9.3 B ± ± ± ± ± 5.7 Discussion Substrate, temperature, and flow all play important roles in the lifecycle of the Chinook salmon. Because salmon require cold, well oxygenated water to thrive, their absence may serve as an indicator of some form of water quality degradation (US Fish & Wildlife, 2010). According to Whitmore et al. (1960), Chinook salmon will avoid waters with DO concentrations of lower than 6 mg/l and behavior becomes erratic at concentrations near 4.5 mg/l. As reported in Table 1, the DO content of the water both sites were above the 6 mg/l level, however Site B was very close to the avoidance level. 6

7 Spawning salmon typically choose large gravel or pebbles to lay their eggs near. Once a suitable spot is chosen, the female salmon will build a nest or series of nests called redds in the substrate and will then deposit anywhere from 2,000 to 7,000 eggs (Regents of the University of California, 2012). After the eggs are fertilized by the males, the eggs will stay in the gravel for approximately days. When the fry hatch, they must stay in this substrate for another 4 6 weeks to remain safe while having time to absorb the nutrient rich yolk sac (Regents of the University of California, 2012). The larger sediment sizes are more preferable at this time because of their capacity to conceal and shield young salmon. A threshold of D50 is established at 7 mm or greater for conditions to be considered adequate (Bennet 2003). According to Figure 1, both Site A and B meet this threshold. Once the fry finally emerge, they typically occupy small pools along the sides of creeks and stream where they are protected from the heaviest water flow, sometimes after first being swept downstream to lower velocity areas (Regents of the University of California, 2012). According to Raleigh et al. (1986), optimal water velocities for Chinook salmon are between 0 and less than 40 cm/s at depths of greater than or equal to 15 cm. The velocities measured for both test sites were well within these parameters. Optimal ph levels for suitable Chinook salmon habitat is within 7 and 8, according to Raleigh (1986). Site B ph levels were within this range and so considered suitable according to this parameter, but Site A s ph level was too high (Table 1). Although alkalinity itself may have few known direct effects upon salmonids, the capacity of solutes in the water to buffer or neutralize acids is important. Waters with low alkalinity will be more susceptible to fluctuations in ph 7

8 level. These fluctuations can be caused by rain, photosynthesis and agricultural runoff (Rounds, 2012). EPA standards suggest a minimum alkalinity of 20 mg CACO₃ to support aquatic life in freshwater systems (1986). As per Table 1, the alkalinity of both research sites was well above this minimum. Fry and juvenile salmon growth rates are affected greatly by water temperature. The preferred range for young salmon is within C, but they can still survive and grow within 5 19 C (Regents of the University of California, 2012). The mean temperatures for both Site A and Site B (Table 1) were both slightly above this preferable range. According to a study by Williams (2006), temperatures of up to 20⁰C are the limit of what juvenile and adult Salmon can tolerate and the Regents of the University of California (2012), state that steady temperatures above 24 C are typically lethal. While well below the lethal limit, the temperatures at both sites were just barely below the upper limit of what juveniles and adults can tolerate. These temperatures would fluctuate throughout the year however, so it is important to do further study during different seasons and at different times of day in order to get a more complete picture of the temperature of the creek. According to our research, neither Site A nor Site B is an optimal habitat for Chinook salmon. Most notably, the temperatures are too high at both sites. The temperature at Site B was closer to the optimal range for salmon but the DO level for Site A was more suitable than that of Site B. Water velocities and ph levels are within acceptable ranges at both sites, but without proper water temperatures, ph, and DO levels, salmon would not thrive. 8

9 More study would be required to gain a fuller understanding of the suitability of the Putah Creek system as salmon habitat. While the research of this paper is simply a comparison of two different sites on Putah Creek for Chinook salmon habitat suitability, it is not possible to know if either site is actually suitable without more knowledge of what transpires upstream and downstream from these sites. Because all Pacific Salmon are anadromous fish and so migrate to spawn, and because of the complex path that Putah Creek takes, a larger sampling area and more information about the Monticello and Solano Diversion Dam flow patterns would be necessary for a more comprehensive analysis. 9

10 References Bennett, D.H. (2003). Substrate composition and emergence success of fall Chinook salmon in the Snake River. Northwest Science. Vol. 77(2) California Environmental Protection Agency, State Water Resources Control Board. (2012). Surface Water Ambient Monitoring Program Quality Assurance Program Plan. Retrieved October 5, 2012, from Marchetti, M.P. and P.B. Moyle. (2001). Effects of flow regime on fish assemblages in a regulated California stream. Ecological Applications. Vol. 11(2) Putah Creek Council. Putah Creek Watershed. Retrieved October 24, 2012, from Raleigh, R.F., W.J. Miller, and P.C. Nelson. (1986). Habitat suitability index models and instream flow suitability curves: Chinook salmon. U.S. Fish Wildlife. Servo Biol. Rep. Vol. 82(10.122) 64. Retrieved October 25, 2012, from Rounds, S.R., (2012). Water quality information: 6.6 alkalinity and acid neutralizing capacity. U.S. Geological Survey. Retrieved October 24, 2012, from The Regents of the University of California. (2008). California Fish Species. Retrieved October 25, 2012, from United States Environmental Protection Agency, Office of Water Regulations and Standards. (1986). Quality criteria for water Retrieved October 24, 2012, from U.S. Department of the Interior. (2004). Negotiating pays off for Putah Creek salmon. Retrieved October 24, 2012, from 10

11 U.S. Fish & Wildlife Service. (2010). Pacific Salmon, (Oncorhynchus spp.). Retrieved October 24, 2012, from Whitmore, C.M., C.E. Warren, and P. Doudoroff. (1960). Avoidance reactions of salmonid and centrarchid fishes to low oxygen concentrations. Transactions of the American Fisheries Society. Vol Williams, J.G. (2006). Central Valley salmon: a perspective on Chinook and steelhead in the Central Valley of California. San Francisco Estuary and Watershed Science 4. Vol. 14(3) Retrieved from Wolman, M. G. (1954). A method of sampling coarse river bed material. Transactions of the American Geophysical Union, Vol. 35(6)