Arroyo Seco and Nacimiento Rivers Index Reach Monitoring Dive Count Surveys

Monterey County Water Resources Agency 890 Blanco Circle Salinas, CA 93902

October 28, 2014

Contents Introduction ...... 5 Methods ...... 5 Nacimiento River ...... 5 Arroyo Seco River ...... 8 Arroyo Seco River Results ...... 9 Site 1 ...... 10 Site 2 ...... 11 Site 3 ...... 12 Site 4 ...... 13 Presence and Absence Surveys ...... 14 Discussion...... 15 Nacimiento River Results ...... 16 Site 1 ...... 18 Site 2 ...... 21 Site 3 ...... 22 Site 4 ...... 25 Discussion...... 26 Work Cited ...... 29

List of Figures

Figure 1: Counting lanes defined...... 7 Figure 2: Block net established on the Nacimiento River...... 7 Figure 3: Diver recording data on waterproof cuff (right) and sample of data recording cuff with length estimate scale (not to scale in image)...... 8 Figure 4: Isolated pooling on the Arroyo Seco River Gorge, on September 18, 2014...... 9 Figure 5: Arroyo Seco Index Reach Monitoring Site Map...... 10 Figure 6: Arroyo Seco River Site 1 comparison between 2013 and 2014 oriented downstream...... 11 Figure 7: Arroyo Seco River Site 2 oriented upstream...... 12 Figure 8: Arroyo Seco River Site 3 oriented upstream...... 13 Figure 9: Arroyo Seco River Site 4 comparison between 2013 and 2014 oriented upstream...... 13 Figure 10: Diver evaluating an isolated pool on the Arroyo Seco River...... 14 Figure 11: Arroyo Seco River Isolated pools evaluated for the presence of O. mykiss...... 14 Figure 12: Sacramento pikeminnow and California roach observed in isolated pools on the Arroyo Seco River...... 15 Figure 13: Nacimiento River Index Reach Monitoring Map...... 17 Figure 14: Ocular evaluation of all sites on the Nacimiento River...... 18 Figure 15: Nacimiento River Site 1 oriented upstream...... 19 Figure 16: limited visibility in the Nacimiento River Site 1...... 20 Figure 17: Nacimiento River Site 1 fish observation data by morphospecies per pass and estimated lengths...... 20 Figure 18: Nacimiento River Site 2 oriented downstream...... 21 Figure 19: Nacimiento River Site 2 fish observation data by morphospecies per pass and estimated lengths...... 22 Figure 20: Nacimiento River Site 3 oriented downstream...... 23 Figure 21: Nacimiento River Site 3 fish observation data by morphospecies per pass and estimated lengths...... 24 Figure 22: O. mykiss observed in the Nacimiento River at Site 3...... 24 Figure 23: Nacimiento River Site 4 oriented upstream...... 25 Figure 24: Nacimiento River Site 4 fish observation data by morphospecies per pass and estimated lengths...... 26 Figure 25: O. mykiss size distribution based upon average number of fish per reach...... 27 Figure 26: Standardized average O. mykiss counts per site based upon the fish per 100 m calculation. .. 28

List of Tables

Table 1: Habitat type classifications as in Ode (2007)...... 6 Table 2: Ocular estimate scale with verbal descriptor defined (Ode, 2007)...... 6 Table 3: Nacimiento River Site 1 sampling area parameters and water quality data...... 19 Table 4: Nacimiento River Site 1 O. mykiss data...... 20

Table 5: Nacimiento River Site 2 sampling area parameters and water quality data...... 21 Table 6: Nacimiento River Site 2 O. mykiss data...... 22 Table 7: Nacimiento River Site 3 sampling area parameters and water quality data...... 23 Table 8: Nacimiento River Site 3 O. mykiss data...... 24 Table 9: Nacimiento River Site 4 sampling area parameters and water quality data...... 25 Table 10: Nacimiento River Site 4 O. mykiss data...... 26

Introduction

In accordance to the Section 7 biological opinion SWR/2003/2080, (BO) conducted by the National Marine Fisheries Service (NMFS) the Monterey County Water Resources Agency (Agency) performed index reach monitoring for South Central California Coast Steelhead (Oncorhynchus mykiss) (O. mykiss) on the Arroyo Seco and Nacimiento Rivers. Index reach monitoring has occurred on both rivers at an annual interval since 2010. The monitoring attempts to achieve an understanding of juvenile O. mykiss response to changes in stream flow as well as distributional information, rearing densities, and to provide samples for determining the proportion of the population derived from anadromous stocks. Based on previous evaluation of habitat conditions multipass depletion backpack electrofishing was deemed the most appropriate sampling method. This method allowed for population estimates to be extrapolated and for a variety of habitat types to be sampled. In 2014, permit constraints by California Department of Fish and Wildlife made electrofishing an unviable option. The Agency decided to conduct index reach monitoring using multi‐pass dive counts. Through these dive counts the Agency was able to estimate O. mykiss rearing densities and determine population spatial distribution throughout each system. Data collection methods were crafted to create anecdotal comparisons between previous years index reach monitoring using electrofishing. No direct statistical comparisons were able to be achieved due to the variation in collection methods.

Both river systems were experiencing below average flow conditions due to the drought conditions. Index Reach Monitoring in the Arroyo Seco River was unable to be conducted, as no flow was present within the sampling area. Only isolated pools remained, with no continuity. The Nacimiento River was at a reduce flow condition as a conservation measure.

Methods

Nacimiento River Four reaches were sampled over a two day period on the Nacimiento River. In order to create a continuous data set from the previous year’s efforts, sampling occurred in three of the same reaches sampled in 2013. An additional site was added mid‐river to create better spatial distribution. Reach length changed from previous years to better facilitate dive count protocol. Block nets were established at both the upstream and downstream end of the reach. As required by the BO, all sampling sites exceeded 30.0 m length.

Each sampling location was habitat typed and features were classified as either a cascade fall, rapid, riffle, run, step‐run, glide, or pool (Ode, 2007) (table 1). Each sampling site contained at least two distinct habitat types. Habitat typing was left to the discretion of the principle investigator. Ode (2007), served as guidelines, but specifics in terms of depth and velocities

were only considered and not used as a definitive parameter. Average wetted width and depth was estimated and the presence of any anthropogenic influences (bridge, dam, etc.) was noted.

Habitat Type Description Cascades Short, high gradient drop in stream bed elevation often accompanied by boulders and considerable turbulence High gradient drop in elevation of the stream bed associated with an Falls abrupt change in the bedrock

Sections of stream with swiftly flowing water and considerable surface Rapids turbulence. Rapids tend to have larger substrate sizes than riffles Shallow sections where the water flows over coarse stream bed particles Riffles that create mild to moderate surface turbulence (< 0.5 m deep, > 0.3 m/s) A series of runs that are separated by short riffles or flow obstructions Step‐Run that cause discontinuous breaks in slope Sections without flow obstructions. The stream bed is typically even and Runs the water flows faster than it does in a pool (> 0.5 m deep, > 0.3 m/s) A section of stream with little or no turbulence, but faster velocity than Glides pools (< 0.5 m deep, < 0.3 m/s) A reach of stream that is characterized by deep, low‐velocity water and a Pool smooth surface (> 0.5 m deep, < 0.3 m/s)

Table 1: Habitat type classifications as in Ode (2007).

Ambient conditions as well as water chemistry (dissolved oxygen and temperature) were collected at all sampling sites. Ocular estimates (based on percentage of coverage in the sampling reach (table 2)) were recorded on aquatic algae, macrophytes/emergent vegetation, boulders, woody debris, undercut banks, overhanging vegetation, rootwads, and artificial structures. Each habitat feature was ranked on a 0‐4 point scale with 0 being absent and 4 being very heavy presence (Table 2). Primary and secondary substrate types were determined based upon ocular estimates (Ode, 2007).

Ocular Estimate Scale Percent 0% <10% 10‐40% 40‐75% >75% Coverage Descriptor Absent: 0 Sparse: 1 Moderate: 2 Heavy: 3 Very Heavy: 4

Table 2: Ocular estimate scale with verbal descriptor defined (Ode, 2007).

Standard Dive Count (Snorkel Survey) techniques (as in Johnson et. al, 2007 and Thurow, 1994) using dual‐pass detection with no calibration was used. Two divers working in tandem moved

upstream counting and identifying fish in designated coounting lanes. Lane designation can be seen in Figure 1. Each numbered fish corresponds with the numbered diver who will count the fish. Fish moving out of one diver’s lane into another diver’s lane will be counted by the divers whose lane the fish moved into (Figure 1).

Figure 1: Counting lanes defined.

Each reach was isolated using 1/4” delta mesh block nets on both the up and downstream end of the reach (Figure 2). The sampling reach was surveyed using two replicate counts, with a 30 minute cessation between counts.

Figure 2: Block net established on the Nacimiento River.

All habitats were sampled within the established reach. All habitat features including open bars and complex cover (snags, undercuts, and eddies) were sampled. A set of hand signals and verbal communication was developed by the dive teams (Bonar, 2009). All fish were counted and given an estimated length. All fish encountered other than O. mykiss were grouped into “morphospecies” assemblages based upon family. Species were grouped as Catostomidae (suckers), Cyprinidae (minnows), and Centrarchidae (sunfish). All other fish encountered outside of these major families were classified as others. Once a species was positively identified to species within the morphospecies group, the common name was communicated to the onshore observer and noted on the datasheet. Individual counts of each species within the “morphospecies” group were not recorded, only presence. All data was recorded on waterproof cuff using a grease pen while underwater (Figure 3) and transferred to datasheets once the dive was complete. Diver’s used a length estimate scales on the dive cuff to insure accurate length estimates (Figure 3).

Figure 3: Diver recording data on waterproof cuff (right) and sample of data recording cuff with length estimate scale (not to scale in image).

Due to the nature of this work assumptions were made in order to interpret the work. At all of the sites, it was assumed that emigration and immigration were prevented by the erection of upstream and downstream block nets. It was also assumed that observation efficiency did not change between passes and that divers did not become more efficient observing fish, nor did fish learn to avoid the divers between passes. During the sampling effort it was determined that habitat complexities contributed to count differences in minnow morphospecies. These fish were often observed amongst rooted aquatic vegetation, and other habitat features that limited visibility.

Arroyo Seco River All sampling that occurred in the Arroyo Seco River was limited due to the drought conditions. No evidence of flow was present. All water within the channel was isolated in pools. The surveys conducted were dives consisting of presence and absence evaluation. No block nets were used as the conditions left no opportunity for immigration or emigration in the reach.

Surveys commenced at the downstream end of the pool and proceeded in an upstream direction.

Arroyo Seco River Results

Monitoring occurred on the Arroyo Seco River on September 17 and 18. All sampling days were sunny and clear with temperatures in the mid to upper 220.0°C. The Arroyo Seco River was not flowing, but wetted deep pools were present. No continuity of flow was observed throughout the entire length of critical habitat for Steelhead (Figure 4). All four sampling locations (Figure 5) from the 2013 sampling effort were revisited. These sites did not have flow and had conditions that did not facilitate snorkeling. Visibility was less than 50 cm and temperature exceeded 20° C with dissolved oxygen levels less than 6.0 mg/l. No snorkeling occurred in these sites, but site observations can be seen below. Snorkeling did not occur upstream of site 1, but efforts were made to locate end of flow.

Figure 4: Isolated pooling on the Arroyo Seco River Gorge, on September 18, 2014.

Figure 5: Arroyo Seco Index Reach Monitoring Site Map.

Site 1

This was the most upstream site sampled in 2013 and has been sampled during each monitoring year. In none of the previous years had flow been absent from this reach (Figure 6).

Water remained in isolated pools amongst boulders and bedrock formations. Water was not flowing between pools so isolated pools were stagnant.

Figure 6: Arroyo Seco River Site 1 comparison between 2013 and 2014 oriented downstream.

Three species of fish were observed (shore based) in the isolated pool including, Sacramento pikeminnow (Ptychocheilus grandis) and Sacramento Sucker (Catostomus occidantalis). A third species of minnow (Cyprinid, spp.) was observed that appeared to be either California Roach (Lavinia symmetricus) or hitch (Lavinia exilicauda). All fish observed in this reach were less than 150 mm. No non‐native species were observed in the issolated pooling.

The conditions present were not conducive to rearing of juvenile or adult O. mykiss. The absence of flow and potential of daily temperature fluctuations in the pools indicates that O. mykiss were not likely to be present. At 9:30 AM on Sepptember 18th, the temperature in the isolated pool was 20. 7 °C with dissolved oxygen levels at 6.28 mg/L.

Site 2 This site is located downstream of site 1 and is on the downstream end of the Arroyo Seco Gorge. This site was sampled in 2013, 2012, and 2011. The pool at the downstream of the reach had isolated water, but the run up stream was dry with no pooling (Figure 7).

Figure 7: Arroyo Seco River Site 2 oriented upstream.

Green sunfish (Lepomis cyanellus), a black bass (spotted or largemouth) species (Micropterrus spp.), and an unidentified minnow species were observed in the shallows of the pool. The black bass and green sunfish were the most abundant species observed. The presence of non‐native species at this site was recorded in previous years sampling events.

Site 3 This site is 0.17 km downstream of Site 3 and was samplled during all monitoring years. The reach that was sampled was completely dry with no isollated pooling (Figure 8). It appeared as if the reach had been unable to support fish for an extended period of time. Areas of potential isolated pooling showed no standing water and only wet soil.

Figure 8: Arroyo Seco River Site 3 oriented upstream.

Site 4 This site was the furthest downstream and was only sampled in 2013. This site was developped last year, as a site used in previous years was not wetted. This reach was comppletely dry expect for areas of isolated pooling in the downstream end of the reach (Figure 9). The wetted portion was shallow and had a high abundance or organic materrial in the streambed. No fish were observed in the reach, but in pooled areas downstream, black bass species were present.

Figure 9: Arroyo Seco River Site 4 comparison between 2013 and 2014 oriented upstream.

Presence and Absence Surveys Dives were conducted upstream of Site 1 in isolated pools to determine if O. mykiss were rearing in the pools (Figure 10). Dives started at the downstream end of the pool and moved upstream. The visibility was limited with a secchi disk only visible at only 1.2 m laterally through the water column. A total of 6 pools were evaluated that ranged from 20 m to 55 m in length and had depths greater than 2.0 m (Figure 11). Often the bottom of the pool was not visible and depths could not be determined. Fish were seen during the dives, including Sacramento pikeminnow, Sacramento sucker, and California roach (Figure 12), but no O. mykiss were observed.

Figure 10: Diver evaluating an isolated pool on the Arroyo Seco River.

Figure 11: Arroyo Seco River Isolated pools evaluated for the presence of O. mykiss.

Figure 12: Sacramento pikeminnow and California roach observed in isolated pools on the Arroyo Seco River.

Discussion The severe drought conditions in California created undesirable habitat conditions for O. mykiss, not seen on the Arroyo Seco River since the monitoring program began in 2010. The absence of flow in the upper reaches eliminated areas of high oxygenation, cover, and potential of drift feeding. In the previous year’s index reach monitoring effort, the highest concentration of fish were found higher in the watershed in cascade and plunge poool type habitat. The natural occurring flow cessation has limited potential habitat to isolated pools. During snorkel surveys conducted of April and May of 2014 (see Arroyo Seco River Out‐migrant Monitoring section), O. mykiss were not observed in pool habitats. All occurrences were associated with cascades and other gradient changes, which created turbulent well oxygenated areas. The presence of only isolated pools with no inflow does not support trends of O. mykiss habitation seen in previous survey efforts.

Though no O. mykiss were observed it does not mean they are not persisting in the Arroyo Seco River. The water clarity conditions, presence of undercut granite banks, and overall depth of the pools limited the success of the survey. Depths in the pools exceeded 2.0 m, and could potentially be as deep as 10.0 m. O. mykiss could have been seeking refugia in the depths of deep pools, where temperature was lower, hypoheric flows were prresent, and potential of benthic feeding can occur.

In 2013, non‐native fish contributed to 31.0% of the total abundances collected (using electrofishing) (Leal et al., 2014). Various species of sunfish were observed persisting in the isolated pools in the lower reaches (downstream of Arroyo Seco Gorge), and based upon visible

observations, were the most abundant species present. The conditions created by the absence of flow support life history of these fish. The conditions in the upper reaches of the Arroyo Seco River had same conditions as the lower reaches, but no non‐native species were observed. The current isolated conditions will limit the spread of non‐native predatory fish to the upper reaches, but the potential for invasion increases when connectivity resumes with higher populations in the lower reaches.

The impacts of the severe drought conditions will not be known until flow is reestablished and sampling can commence as it has in previous years. The lack of connectivity with the Salinas Lagoon and Pacific Ocean (2 years) has eliminated access of adult steelhead to the Arroyo Seco River, so reproduction from anadromous stocks has not occurred. These breaks in the anadromous cycle occur naturally and can rebound if the duration is not prolonged.

Nacimiento River Results

Data collection occurred on the Nacimiento River on October 21 and 22. All sampling days were primarily sunny and clear with temperatures in the low 20°C. Sampling occurred during the drought conditions flow reduction. Daily average flow for October 21 was 34 cfs and 35 cfs for October 22, at the USGS 11149400 Nacimiento River below Nacimiento dam near Bradley, CA stream flow gage. Four sampling locations were selected (Figure 13). Three sites used in the 2013 index reach survey (Sites 1, 2, and 4) were reevaluated using the new method, and a new site was added mid‐reach to improve spatial distribution.

Figure 13: Nacimiento River Index Reach Monitoring Map.

All sites habitat conditions were evaluated using the ocular estimate method sttated in the methods section. These results are graphed jointly to provide a visual comparison of site

conditions (Figure 14). Variations of habitat conditions are directly related to location within the watershed and current flow conditions. Each evaluated parameter is not ranked based upon its benefit to O. mykiss, and an overall higher value on the graph does not necessarily indicate better habitat. The value within each stacked bar indicate the scale value defined in Table 2.

Figure 14: Ocular evaluation of all sites on the Nacimiento River.

Site 1 This site is located 2.33 km downstream of the Nacimiento Dam and is on the Camp Robert’s Military Base property. This site was sampled in 2013, but it was expanded upstream this year to cover more habitat types. This sampling reach consisted of a narrow riffle flowing into a pool to a riffle, with a gradient change formed by a bar, which flowed into a run (Figure 15 and Table 3). Anthropogenic inputs such as a large steel drum and other debriis created variability in flow in the run section. Overhanging vegetation and woody debris was spparse (Figure 14), but the habitat had complexities in terms of gradient changes annd undercut banks. The gradient change below the pool created adequate depth and flow to support drift feeding and summer rearing and water quality conditions (Table 3) were suitable for O. mykiss.

Figure 15: Nacimiento River Site 1 ooriented upstream.

Site 1 Pool (22%) Riffle (28%) Run (50%) Wetted Width Depth Length (mean) (mean) 10.0 m 0.5 m 90.0 m Temperature Dissoolved Oxygen Visibility (°C) (mg/l) 1.2 m 16.1 8.61 Primary Substrate Secondary SSubstrate Cobble Gravel Table 3: Nacimiento River Site 1 sampling area parameters and water quality data.

Visibility in this reach made observational data collection difficult (Figure 16). Pass 1 observation period was 20 minutes and Pass 2 was three minutes shorter at 17 minutes. Total abundance in the reach was estimated between 10 and 13 fish with one O. mykiss observed during each pass. Counts of each morphospecies other than O. mykiss varied between passes (Figure 17). The total population estimate for O. mykisss in Site 1 with assumptions in place was one fish with a standardized estimated 1.11 fish per 100 m (Table 4)). Aside from O. mykiss, Sacramento suckers and Sacramento pikeminnow were positively identified.

Figure 16: limited visibility in the Nacimiento River Site 1.

Figure 17: Nacimiento River Site 1 fish observation data by morrphospecies per pass and estimated lengths.

Nacimiento River Site 1 O. mykiss Countts Pass 1 Pass 2 1 1 Average O. mykiss Per 100 m 1.11 fish Table 4: Nacimiento River Site 1 O. mykiss data.

Site 2 This site is located 3.82 km downstream of the Nacimiento Dam and is on the Camp Robert’s Military Base property. This site was sampled in 2013, but it was expanded downstream this year to cover more habitat types. This sampling reach consisted of a run flowing into a riffle, with a transition into a pool (Figure 18 and Table 5). Overhanging vegetation and woody debris was sparse (Figure 14), but the habitat complexities in thhe form of right bank dominated undercut banks and a large boulder structure created habitat for rearing O. mykiss. Water quality in the reach (table 5) showed conditions that were adequate to support O. mykiss.

Figure 18: Nacimiento River Site 2 oriented downstream.

Site 2 Pool (17%) Riffle (42%) Run (41%) Wetted Width Depth Length (mean) (mean) 7.0 m 0.5 m 59.0 m Temperature Dissoolved Oxygen Visibility (°C) (mg/l) 1.4 m 17.7 9.68 Primary Substrate SSecondary Substrate Cobble Gravel Table 5: Nacimiento River Site 2 sampling area parameters and water quality data.

Visibility in this reach made observational data collection difficult, but it was greater than what was observed in Site 1. Pass 1 observation period was 30 minutes and Pass 2 was five minutes shorter at 25 minutes. Total abundance in the reach was estimated between 10 and 13 fish with four O. mykiss observed during Pass 1 and five on Pass 2. Counts of each morphospecies varied between passes (Figure 19). The total population estimate for O. mykiss in Site 1 with assumptions in place was a minimum of four and a maxiimum of five, with a standardized estimated 5.93 fish per 100 m (Table 5). Aside from O. mykiss, Sacramento suckers, Sacramento pikeminnow, prickly sculpin (Cottus asper), and speckled dace (Rhinichthys osculus) were positively identified.

Figure 19: Nacimiento River Site 2 fish observation data by morrphospecies per pass and estimated lengths.

Nacimiento River Site 2 O. mykiss Countts Pass 1 Pass 2 4 5 Average O. mykiss Per 100 m 5.93 fish Table 6: Nacimiento River Site 2 O. mykiss data.

Site 3 This site is located 12.40 km downstream of the Nacimiento Dam and is on the Camp Robert’s Military Base property. This site was not sampled in 2013, but was added to increase spatial distribution. This sampling reach consisted of a riffle with a small rapid that flowed into a long uniform run (Figure 20 and Table 7). Overhanging vegetaation was sparse but the presents of boulders, undercut banks, and an artificial structure (concrete) creating a rapid created

beneficial habitat for O. mykiss (Figure 14). Water quality in the reacch (Table 7) showed conditions that were adequate to support O. mykiss.

Figure 20: Nacimiento River Site 3 oriented downstream.

Site 3 Riffle (18%) Run (72%) Rapid (10%) Wetted Width Depth Length (mean) (mean) 8.6 m 0.4 m 80.0 m Temperature Dissoolved Oxygen Visibility (°C) (mg/l) 2.2 m 19.5 10.87 Primary Substrate SSecondary Substrate Cobble Gravel Table 7: Nacimiento River Site 3 sampling area parameters and water quality data.

Visibility improved as distance progressed downstream,, but was still a limiting factor of the survey. Pass 1 observation period was 25 minutes and Pass 2 was two minutes longer at 27 minutes. Total abundance in the reach was estimated between 60 and 61 fish with three O. mykiss observed during Pass 1 and two on Pass 2. Counnts of each morphospecies varied between passes (Figure 21). The total population estimate for O. mykiss in Site 1 with assumptions in place was a minimum of two and a maximum of three, with a standardized

estimated 3.13 fish per 100 m (Table 8). Aside from O. mykiss (Figure 22), Sacramento suckers and Sacramento pikeminnow were positively identified.

Figure 21: Nacimiento River Site 3 fish observation data by morrphospecies per pass and estimated lengths.

Nacimiento River Site 3 O. mykiss Countts Pass 1 Pass 2 3 2 Average O. mykiss Per 100 m 3.13 fish Table 8: Nacimiento River Site 3 O. mykiss data.

Figure 22: O. mykiss observed in the Naacimiento River at Site 3.

Site 4 This site is located 17.83 km downstream of the Nacimiento Dam and is 2.27 km upstream of the confluence with the Salinas River. This site was sampled in 2013, but it was expanded both up and downstream to increase the diversity of the sampling reach. This sampling reach consisted of a riffle flowing into a large run that flowed into a short plunge riffle, which flowed into a pool (Figure 23 and Table 9). Overhanging vegetation was sparse but undercut banks and woody debris were present (Figure 14). Water quality in the reach (table 9) showed conditions that were adequate to support O. mykiss.

Figure 23: Nacimiento River Site 4 ooriented upstream.

Site 4 Riffle (23%) Run (50%) Pool (27%) Wetted Width Depth Length (mean) (mean) 12.33 m 0.3 m 110.0 m Temperature Dissoolved Oxygen Visibility (°C) (mg/l) 3.0 m 18.5 10.54 Primary Substrate Secondary SSubstrate Gravel Sand Table 9: Nacimiento River Site 4 sampling area parameters and water quality data.

Visibility was greatest at this site and allowed lane to bank visibility for both divers. Pass 1 observation period was 45 minutes and Pass 2 was six minutes shorter at 39 minutes. Total abundance in the reach was estimated between 73 and 110 fish with no O. mykiss observed in either pass. Counts of each morphospecies varied between passes (Figure 24), which can be contributed to rooted aquatic vegetation and other cover present in the reach. The total population estimate for O. mykiss in Site 4 with assumptions in place was zero fish, with a standardized estimated 0.0 fish per 100 m (Table 10). Sacramento suckers and Sacramento pikeminnow were positively identified along with a potential prickly sculpin.

Figure 24: Nacimiento River Site 4 fish observation data by morrphospecies per pass and estimated lengths.

Nacimiento River Site 4 O. mykiss Countts Pass 1 Pass 2 0 0 Average O. mykiss Per 100 m 0.0 fish Table 10: Nacimiento River Site 4 O. mykiss data.

Discussion O. mykiss were encountered at all reaches except Site 4 which is the most downstream site. This is the first year during the Index Reach Monitoring pprogram that more than one O. mykiss was encountered. The dive count method associated with the flow reduction lead to sampling success and a better estimate of O. mykiss populations. The resultss still indicate that O. mykiss are in low abundance, but they do persist and show variation in size classes. An O. mykiss over

150 mm was observed, but most fish fell into the 100‐150 mm size class (Figure 25). No fish under 100 mm were observed, which would indicate that all fish were of the age 1 year or older. Based on the conditions during the data collection it is possible that fish under the 100 mm were not encountered. The limited visibility and rooted aquatic vegetation could have limited the success rate of observing fish under 100 mm, especially species that are less gregarious and more wary.

Figure 25: O. mykiss size distribution based upon average number of fish per reach.

O. mykiss were distributed to a point a minimum of 17.83 km downstream of the dam. It would be expected that higher densities would be found in the upper reacches of the watershed, as temperature would be lower, and the gradient would inncrease creating more benthic diversity. The highest density was at Site 2 (Figure 26). This reachh had beneficial habitat in the form of undercut banks and a boulder formation that created diverse flow conditions. Site 1, had limited diversity in flow and lacked boulders. Woody debris was present in Site 1, but was settled in the pool section and did not create variability in flow. All fish observed in Sites 2 and 3 were associated with boulders or riprap that created complex flows. O. mykiss appeared to be associated with beneficial habitat more than specific position in tthe river.

Figure 26: Standardized average O. mykiss counts per site based upon the fish per 100 m calculation.

The dive count method used in the 2014 Index Reach Monitoring associated with the lower flows provided O. mykiss observations that were higher than observed in previous years. It did not provide as much detailed information on the presence of other species, and may have created sample bias in terms of smaller fish observationn, but did achieve the goal of assessing O. mykiss abundance and distribution in the system. Though historiically non‐native species presence in the Index Reach Monitoring is low, this year’s effort yielded no observations of nonnative species. Many other species accounted for in the previous year’s effort were not seen or positively identified with the dive count method. Based upon an average of the standardized average O. mykiss counts the estimated fish per 100 m would be 2.54 fish for the entire Nacimiento River. With an estimated river length of 19.62 km the total number of O.. mykiss would be approximately 500 fish. This estimate is an extrapolation based upon limited data, but provides an idea of the potential population within the Nacimiento River.

Work Cited

Bonar, S. C., Hubert, W. A., and Willis D. W., editors. (2009). Standard Method for Sampling North American Freshwater Fishes. American Fisheries Society, Bethesda, Maryland.

Johnson, D.H., Shrier, B.M., O’Neal, J.S., Knutzen, J.A., Augerot, X., O’Neil, T.A., & Pearson, T.N. (2007). Salmonid Field Protocols Handbook: Techniques for Assessing Status and Trends in Salmon and Trout Populations. American Fisheries Society, Bethesda, Maryland:

Leal, C.C., Krafft, E.A., and Voss, T.E. (2014). Salinas Valley Water Project Annual Fisheries Report for 2013. Monterey County Water Resources Agency, Salinas, CA.

NMFS [National Marine Fisheries Service]. 2007. Biological Opinion: Monterey County Water Resource Agency, Salinas Valley Water Project in Monterey County, California. File Number: SWR/2003/2080 (Admin. No.:151422SWR2003SR8711). NMFS Southwest Region, Long Beach, CA.

Ode, P. (2007). Standard operation procedure for collecting benthic macroinvertebrate samples as associated physical and chemical data for ambient bioassessment in California. California State Water Control Board.

Thurow, R. F. (1994). Underwater Methods for Study of Salmonids in the Intermountain West. United States Department of Agriculture (Forest Service), Ogden, UT.