Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Prepared for New Mexico Interstate Stream Commission Albuquerque, New Mexico

Prepared by SWCA Environmental Consultants

April 2007

Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Prepared for

New Mexico Interstate Stream Commission Albuquerque, New Mexico

Prepared by

Ann M. Widmer1, Jon W. Kehmeier1, and Joseph J. Fluder, III2

1SWCA Environmental Consultants 295 Interlocken Blvd., Suite 300 Broomfield, CO 80021

2SWCA Environmental Consultants 5647 Jefferson St., NE Albuquerque, NM 87109

April 2007

Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

EXECUTIVE SUMMARY Artificial eggs (gellan beads) were used to characterize the retention and transport of silvery minnow eggs through the Albuquerque and Isleta reaches during spring 2005. This project occurred as three experiments, which quantified the retention of artificial eggs 1) between Angostura and San Acacia during high flow immediately following the arrival of a flood pulse (high flow ascending limb); 2) between Isleta and San Acacia at high flow without an ascending hydrograph (constant high flow); and 3) between Angostura and South Diversion Channel at low flow (constant low flow). These experiments enabled comparisons of egg retention between the Albuquerque and Isleta reaches under three flow conditions. Retention of artificial eggs was highest during the high flow ascending limb experiment, when inundation of floodplain areas and in-channel features would have been greatest (range 1.9% to 13.8% beads retained per km). Retention was 1.07 times higher in the Albuquerque Reach compared to constant low flow and 3.19 times higher in the Isleta Reach compared to constant high flow. Average egg retention rates were higher in the Isleta Reach than the Albuquerque Reach at all flows sampled. Egg retention was 4.78 times higher in the Isleta Reach than the Albuquerque Reach during the high flow ascending limb experiment; the magnitude of this difference was likely due to floodplain connection in the Isleta Reach.

Rio Grande silvery minnow distribution, as measured by catch per unit effort, appears to be roughly correlated with calculated bead retention rates. The majority of silvery minnow captured in the Isleta and Albuquerque reaches in April, May, and June 2005 were located in river kilometers 260 to 211, a section of the Isleta Reach that demonstrated consistently high rates of bead retention.

Results suggest that egg retention habitat is limited in the Albuquerque Reach, consistent with the results of other studies. It may be worthwhile to repeat the study at flow rates similar to the 2005 flows to assess whether the habitat restoration work conducted and planned for the reach is successful in retaining a higher proportion of beads.

At both the flows tested, egg retention habitat in the Isleta Reach appeared to be high quality; bead retention rates in this reach were comparable to the highest rates measured on the Pecos River (Kehmeier et al. 2004). A study to identify the habitat features that retain eggs in the Isleta Reach could be valuable to restoration efforts in the Albuquerque Reach and elsewhere. It may also be useful to identify the sections of the Isleta Reach that retain the greatest numbers of eggs to enable more focused conservation efforts.

ii Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

TABLE OF CONTENTS Page INTRODUCTION ...... 1 METHODS ...... 4 Artificial Eggs ...... 4 Study Location and Timing...... 4 Bead Collector...... 8 Hydrology Model...... 9 Bead Velocity and Retention Calculations ...... 9 Model of Egg Retention in the Albuquerque and Isleta Reaches ...... 13 RESULTS ...... 15 Experiment 1: High Flow Ascending Limb...... 17 Experiment 2: Constant High Flow ...... 22 Experiment 3: Constant Low Flow ...... 27 Summary of Reach-wide Retention ...... 32 Comparison of Bead Retention and Silvery Minnow Distribution...... 32 Comparison of Modeled Egg Retention Using Hypothetical Uniform Distribution ...... 32 DISCUSSION ...... 35 CONCLUSIONS...... 39 RECOMMENDATIONS ...... 39 REFERENCES...... 40

LIST OF TABLES Table Page 1 Bead release and collection sites on the Rio Grande for the three egg retention experiments in 2005...... 5 2 Collection of silvery minnow eggs and fish by MECs during the three bead drift experiments...... 16 3 Average bead velocities through study reaches during three sampling events in 2005 based on arrival of peak bead densities...... 16 4 Total numbers of beads released and collected, estimated bead totals, and reach-specific retention rates during the high flow ascending limb experiment. Empty cells indicate no beads were released, collected, or estimated at that site...... 20 5 Distance (km) to retain different proportions of eggs at transport rates observed during the high flow ascending limb experiment...... 20 6 Total numbers of beads released and collected, estimated bead totals, and reach-specific retention rates during the constant high flow experiment. Empty cells indicate no beads were released, collected, or estimated at that site...... 25 7 Distance (km) to retain different proportions of eggs at transport rates observed during the constant high flow experiment...... 25 8 Total numbers of beads released and collected, estimated bead totals, and reach-specific retention rates during the constant high flow experiment. Empty cells indicate no beads were released, collected, or estimated at that site...... 30

iii Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

LIST OF TABLES (continued)

Table Page 9 Distance (km) to retain different proportions of eggs at transport rates observed during the constant low flow experiment...... 30 10 Reach-wide retention rates calculated from the three bead retention experiments...... 32

LIST OF FIGURES Figure Page 1 Range of the silvery minnow and reaches of the Middle Rio Grande...... 3 2 Mean daily discharge at Albuquerque during three egg retention experiments in 2005 and the mean daily discharge for years 1974 – 2005 for months April-August (USGS Albuquerque Central Gage)...... 5 3 Bead release and collection locations (river kilometer)...... 7 4 Use of Moore egg collector (MEC) to sample beads...... 8 5 Extrapolated rates of bead passage through the channel (beads/15 min) at Calabacillas collection site using both MECs (top) and with the faulty flow meter omitted (bottom).. 11 6 Extrapolated rates of bead passage through the channel (beads/15 min) at South Diversion Channel collection site using both MECs (top) and with the faulty flow meter omitted (bottom)...... 12 7 Modeled hydrograph during the high flow ascending limb experiment...... 18 8 Instantaneous number of yellow beads passing through the river channel at each collection site during the high flow ascending limb experiment...... 19 9 Modeled egg retention in the Albuquerque and Isleta reaches based on bead retention rates observed during the high flow ascending limb experiment and calculated spring silvery minnow population distribution...... 21 10 Modeled hydrograph during the constant high flow experiment...... 23 11 Instantaneous number of red beads passing through the river channel at each collection site during the constant high flow experiment...... 24 12 Modeled egg retention in the Isleta Reach based on bead retention rates observed during the constant high flow experiment and calculated spring silvery minnow population distribution...... 26 13 Modeled hydrograph during the constant low flow sampling event...... 28 14 Instantaneous number of red beads passing through the river channel at each collection site during the July sampling event...... 29 15 Modeled egg retention in the Albuquerque Reach based on bead retention rates observed during the constant low flow experiment and calculated spring silvery minnow population distribution ...... 31 16 Modeled egg retention in the Albuquerque and Isleta reaches based on bead retention rates observed during the high flow ascending limb experiment and hypothetical uniform silvery minnow population distribution...... 34

iv Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

LIST OF APPENDICES Appendix A Description of Bead Release and Collection Sites B Maps of the Bead Release and Collection Sites C Bead Collection Dates and Times

v Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

INTRODUCTION

The endangered Rio Grande silvery minnow (silvery minnow, Hybognathus amarus) is a member of a specialized reproductive guild, which spawns by releasing semi-buoyant, non- adhesive eggs into the river current (Platania and Altenbach 1998). Stimulated by high flow conditions (Platania and Dudley 2003) and increased water turbidity (Personal communication, M. Hatch and C. Altenbach 2006), silvery minnow release up to 3,500 eggs per reproductive event, which are immediately fertilized by accompanying males and water- harden to 2.9–3.7 millimeters (mm), becoming nearly neutrally buoyant (Platania 1995; Platania and Altenbach 1998). Eggs and larvae drift passively with the current until entrained or until larvae develop air bladders and can actively seek low-velocity nursery habitats (3 to 5 days post-spawning) (Platania 1995). The distance traveled during this time depends on the channel morphology, water velocity, and rate of larval development. Unimpeded, Platania (1995) estimated that silvery minnow eggs and larvae could be transported up to 360 kilometers (km) downstream (5 days at 3 kilometers per hour [km/hr]). However, short reaches of high quality habitat may be capable of entraining large numbers of eggs. Egg retention models for another member of this pelagic-spawning guild, the Pecos bluntnose shiner (Notropis simus pecosensis), indicated that 90% of the eggs released in the Pecos River during high flows are retained within 50 km of river in broad complex channel reaches with a large interaction between the channel bed and flows (Kehmeier et al. 2004; Medley et al. in review).

The reproductive strategy of the silvery minnow is hypothesized to be a survival mechanism in response to dynamic geomorphic and hydrologic conditions in rivers of the Southwest, as the drift of eggs and larvae from upstream reaches supplements the population in intermittent reaches downstream (Platania and Altenbach 1998). The silvery minnow population as a whole would be displaced downstream over time if it were not for life history strategies that counter downstream transport, although the specific strategies used by the silvery minnow are not well understood. The downstream transport of eggs and larvae may be counteracted by the upstream movement of adults (Cowley et al. 2005) or juvenile fish (Dudley et al. 2005). Alternatively, the timing and location of spawning may have evolved to maximize local egg retention, minimizing the need for upstream movement (Medley et al. in review). A study using artificial eggs on the Pecos River has suggested that the retention of pelagic drifting eggs is greatest if eggs are released soon after the arrival of a flood wave, when the rate of flood wave attenuation and channel storage is greatest (Kehmeier et al. 2004; Medley et al. in review). This timing has been observed in several pelagic-spawning cyprinids in the region (Platania and Altenbach 1998).

The silvery minnow currently inhabits a 275-km section of the Rio Grande located between Cochiti Dam and Elephant Butte Reservoir, New Mexico (Bestgen and Platania 1991), which is fragmented into four reaches (Cochiti, Albuquerque, Isleta, and San Acacia) by three diversion dams (Figure 1). Monitoring data indicate that the silvery minnow population is often concentrated in the downstream reaches (Dudley and Platania 2001, 2002), suggesting that the mechanisms used by this species to counter downstream transport may not work in all years or under all conditions. Downstream displacement is hypothesized by some to occur because the diversion dams (Angostura, Isleta, and San Acacia) act as instream barriers and prevent silvery minnows from moving upstream after hatching (Platania 1995; U.S. Fish and

1 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Wildlife Service [USFWS] 2003). Downstream displacement might also result from habitat degradation or sub-optimal flows in upstream reaches, which could decrease the local production, retention, and survival of silvery minnow eggs and larvae. Channel and flow modifications in the Middle Rio Grande have reduced channel sinuosity and island abundance, thereby decreasing the availability of edge habitat where silvery minnow eggs or larvae might settle out of the current (Porter and Massong 2004a). These modifications have also decreased the availability of nursery habitats, which are warm, shallow, productive areas, often located in shoreline or island inlets, abandoned side channels, and backwaters inundated by spring flows (Pease 2004).

The rates of silvery minnow egg retention in each reach and the distribution of retained eggs throughout the silvery minnow range are believed to directly influence population distribution and, ultimately, the persistence of the species. Understanding the mechanisms of egg retention and the current egg retention rates in the Middle Rio Grande is important to promote sound, scientifically based recovery actions for the silvery minnow. Most individual silvery minnows live only one year (Bestgen and Platania 1991), so successful annual spawning is key to the survival of the species (USFWS 2003). The objective of this study was to quantify egg and larval drift characteristics in the Middle Rio Grande in the Albuquerque and Isleta reaches under three different flow conditions. These data may be used to begin to develop scenarios to manage the river system to benefit the silvery minnow while conserving water resources to the extent possible. Specifically, the major goals of this study include the following:

1. Characterize the retention and transport of silvery minnow eggs in the Middle Rio Grande between Angostura and San Acacia diversion dams a. Between Angostura and San Acacia at high flow immediately following the arrival of a flood pulse (high flow ascending limb); b. Between Isleta and San Acacia at high flows without an ascending hydrograph (constant high flow); and c. Between Angostura and South Diversion Channel at low flow (constant low flow). 2. Compare and contrast egg retention a. At high flow ascending limb vs. constant low flow in the Albuquerque Reach; b. At high flow ascending limb vs. constant high flow in the Isleta Reach; c. Between the Albuquerque and Isleta reaches. 3. Use available information about the distribution and abundance of the present adult silvery minnow populations in a transport and retention model to make predictions about how habitat restoration, river management, and program activities might affect silvery minnow egg and larval drift and distribution. 4. Correlate egg retention rates to habitat and/or channel characteristics including sinuosity, width/depth ratios, overbank potential, mid-channel bar and island density, etc. Note: this final objective will be completed in an addendum to this report.

2 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Figure 1. Range of the silvery minnow and reaches of the Middle Rio Grande.

3 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

METHODS

The study was conducted on the Rio Grande between Angostura Diversion Dam and San Acacia Diversion Dam. Silvery minnow eggs were simulated with gellan gum beads (beads), which were released into the thalweg and collected at sites downstream on three occasions (May, June, and July sampling periods). Beads were collected using Moore egg collectors (MECs) (Altenbach et al. 2000) for approximately 20 to 30 hours at sites downstream after the collection of the first bead; these data and modeled river discharge were used to calculate rates of egg passage past each collection point and to estimate egg retention in the reach. The study methodology is described in detail below.

Artificial Eggs

Gellan gum beads (Technology, Flavors, and Fragrances, Inc., Amityville, New York, USA) were used as surrogates for silvery minnow eggs. Gellan beads have been previously utilized to simulate drifting eggs and larvae in numerous studies related to Pecos bluntnose shiner (Kehmeier et al. 2004; Widmer and Kehmeier 2006), Rio Grande silvery minnow (Porter and Massong 2003, 2004b, 2006), and striped bass (Morone saxatilis) (Davin et al. 1999; Will et al. 2001; Reinert et al. 2004).

Gellan beads approximate the size, shape, and specific gravity of silvery minnow eggs. Gellan beads are roughly spherical and 3 to 4 millimeters (mm) in diameter. Silvery minnow eggs are 2.9 to 3.7 mm in diameter (Platania and Altenbach 1998) with a mean specific gravity of 1.00598 ± 0.00018 grams per cubic centimeter (g/cm3) (45 minutes post fertilization) to 1.00281 ± 0.00007 g/cm3 (12 hours post fertilization) (Cowley et al. 2005). The buoyancy of silvery minnow eggs also changes dynamically with water salinity, but is very similar to that of gellan beads between 0.5 and 4.0 parts per thousand (ppt) salinity (Cowley et al. 2005).

Beads were received in six 208-liter (L) drums with packing syrups. The beads were drained and soaked in tap water for at least one week to rinse residual syrups and to achieve a specific gravity approximately equal to that of silvery minnow eggs. The number of beads in each drum was estimated at approximately 3.38 million based on extrapolation from several 100- milliliter (mL) aliquots.

Study Location and Timing

The study was broken into three experiments, each occurring in a different month, to characterize egg retention under different flow conditions: high flow ascending limb, constant high flow, and constant low flow (Figure 2, Table 1). The field portion of both “constant flow” experiments occurred at relatively stable periods within the larger descending limb of the hydrograph. Because beads were released and collected during relatively constant flow, the bead retention calculations reflect predicted egg retention at constant flow. Both high flow experiments occurred at higher-than-average flows, with flows exceeding the bankfull channel and inundating lower floodplain areas in the Isleta Reach during the high flow ascending limb experiment. The river discharge during the low flow experiment was slightly below the historical average.

4 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Beads were released below Angostura and/or Isleta diversion dams to separately characterize retention in the Albuquerque and Isleta reaches. Collection sites were spaced relatively evenly throughout the study reach (Figure 3), although site placement was limited by reasonable river access. The release and collection sites are described in Appendix A and their locations shown in Appendix B.

7000 Experiment 1: High flow on the ascending limb Average of 31 6000 Experiment 2: Constant Years of Record high flow

2005 5000

4000 Experiment 3: Constant low flow 3000

2000 Mean (cfs) Daily Discharge 1000

0 April May June July August

Month

Figure 2. Mean daily discharge at USGS Albuquerque Central Gage during three bead retention experiments in 2005 and the mean daily discharge for years 1974 through 2005 for months April through August.

5 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Table 1. Bead release and collection sites on the Rio Grande for the three egg retention experiments in 2005. Distances Between Number of Experiment Release Sites Collection Release Sites and Experiment Beads Released, Dates (RK) Sites (RK) Collection Sites in Color, and Time RK 550 Bridge 9.33 (327.82)

Calabacillas 29.28 (307.87) Below 3 barrels South Angostura yellow Diversion 51.33 Diversion 5/12/2005 at Channel Dam (337.15) 07:08 (285.82) High flow 5/12/2005 – ascending Los Lunas 5/14/2005 82.71 limb (254.44) San Acacia 148.38 (188.77)

Los Lunas 3 barrels 18.02 Below Isleta (254.44) orange Diversion 5/12/2005 at Dam (272.46) San Acacia 16:19 83.69 (188.77)

Los Lunas 18.02 (254.44) 3 barrels Below Isleta Constant 6/22/2005 – red Veguita Diversion 47.47 high flow 6/24/2005 6/22/2005 at (224.99) Dam (272.46) 08:40 San Acacia 83.69 (188.77)

550 Bridge 9.33 (327.82) Below 3 barrels Calabacillas Constant 7/7/2005 – Angostura yellow 29.28 (307.87) low flow 7/8/2005 Diversion 07/07/2005 at Dam (337.15) 06:20 South Diversion 51.01 Channel (286.14) RK = river kilometers

6 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Figure 3. Bead release and collection locations (river kilometer).

7 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Bead Collector Artificial eggs were collected using MECs (Altenbach et al. 2000) at the collection sites for approximately 20 to 30 hours after the initial arrival of eggs, or until low egg counts were consistently recorded (Table C-1). Each site had a MEC in the water at all times and data were collected in 15-minute (min) or 30-min intervals, depending on bead density in the channel.

The MEC is a device similar to a sluice-box, with a rectangular opening at its upstream end (width = 45 centimeter [cm]; height = 33 cm), parallel sides (length = 119 cm), and an open top (Altenbach et al. 2000). The bottom is a framed fiberglass window screen (1.6-mm mesh) installed at a 23-degree angle relative to the top of the box. Metal fence posts support the unit in the water so that the rectangular opening is positioned just below the water’s surface but no water passes over the open top of the box (Figure 4). Water passes in through the rectangular opening and out through the screen; eggs, insects, and other debris are retained on the screen for inspection and/or collection. Beads collected during each collection interval were counted in the field. A General Oceanics flow meter mounted in the center of the rectangular opening continually measured flow of water through the MEC during bead collection periods.

Artificial eggs were collected in water 0.6 to 1.2 meters (m) deep, regardless of river flows. MECs were sometimes repositioned during the sampling period to improve data collection or for the safety of the field crew. This study assumed that the beads had mixed evenly across the river channel prior to arrival at the collection site. Based on this assumption, the position of the MEC in the river channel should not matter, as the instantaneous bead density should be consistent across the channel. Bead passage rates could be extrapolated from bead collection rates so long as the flows through the MEC were accurately measured and the river discharge was accurately modeled.

Direction of flow

Figure 4. Use of Moore egg collector (MEC) to sample beads.

8 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Hydrology Model Modeled river flows were used instead of U.S. Geological Survey (USGS) gage-measured flows, because gages were not present at all collection sites and some gage data were considered unreliable. All the 15-min data for the sand bed gages on the Rio Grande should be viewed with caution, particularly during high flow events, because the bottom of the river channel can undergo both scour and deposition during such events. The Albuquerque Gage is one such gage. In such cases, models most likely provide more accurate data (personal communication, R. Schmidt-Petersen 2007).

River flows were modeled throughout the study reach for each experimental period. Site- specific discharges predicted by the model were used in bead passage calculations instead of USGS gage data, because gages were not available at all sites, and some were considered unreliable at high flows. The Middle Rio Grande flood routing model Flo-2D (Tetra Tech, Inc. 2002) was used to develop downstream hydrographs during the three experiments.1 “The Flo-2D model is a simple volume conservation model that can distribute a flood hydrograph through the system. It is a two-dimensional model that numerically routes a river flow over a grid of surface points while predicting the area of flooding and how much the flood wave is slowed by the floodplain” (URGWOPS DEIS 2006).

Measured 60-min flow hydrographs from the Rio Grande at San Felipe and Jemez River below Jemez Dam USGS gages were used as input to the Flo-2D model. The model was run for three time periods to coincide with the three egg retention experiments. The first run covered the period from May 9 to May 16, 2005; the second run covered the period from June 19 to June 26, 2005; and the third run covered the period from July 4 to July 11, 2005. Downstream hourly flow hydrographs were generated each bead release and collection site. Discharge estimates from the model were then broken down into 15-min intervals, assuming a linear change in discharge between hours. Modeled discharge data were used in all channel- wide bead passage calculations.

Bead Velocity and Retention Calculations Bead velocities were calculated for comparison among discharges and river reaches by dividing the distance traveled (km) by the time passed. Time passed was the difference between the time the beads were released and the time the peak bead density was observed. The first bead of a color was usually collected 15 min to 1 hour before peak bead density was achieved. Time to maximum bead density was used rather than time to first bead collected so that the calculated velocity would describe the movement of the majority of beads released.

The number of beads of a specific color passing a collection site during 5 days was quantified by extrapolating sample data. Five days represents the time that eggs and larvae passively drift before larvae are able to actively seek suitable rearing habitat (Platania and Altenbach 1998). Water column bead densities were calculated from the number of beads collected in a MEC, divided by the volume of water passing through each drift net during the same interval, and reported as beads per cubic meter. Volume of water passed was the product of the net opening (square meters [m2]), velocity (meters per second [m/s]) at the mouth of the MEC,

1 Hydrology modeled by Nabil Shafike, New Mexico Interstate Stream Commission

9 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande and time interval (s). The average bead passage rate through the channel (beads/second) for each 15-min sampling interval was calculated as the product of bead density and modeled discharge (m3/s) during the collection period, under the assumption that the beads were uniformly distributed across the channel. This is a standard assumption in these types of studies and is the basis of the simple, one dimensional models frequently used to describe solute and particle transport (Runkel 1998).

Data from two collection sites, Los Lunas and Calabacillas, were discarded from the high flow ascending limb experiment. Collection sampling was initiated too late at Los Lunas to quantify the first pulse of yellow beads moving through the channel. Furthermore, the orange beads released below Angostura Diversion Dam were faded and could not be reliably distinguished from yellow beads at the Los Lunas collection site. Data at Calabacillas were discarded because the calculated bead density rates were suspiciously low. The main channel at Calabacillas could not be safely sampled during the high flow with ascending limb experiment, so crews sampled a smaller perennial side channel. In retrospect, it appears that bead density in the side channel was not representative of bead density in the main channel.

Data from two MECs during the constant low flow experiment were discarded. The field collection sheets noted repeated problems with flow meters in MECs (e.g., “meter jammed”), one each at Calabacillas and South Diversion Channel collection sites, and the faulty equipment was used throughout the experiment. Evidence of the problems with these flow meters is apparent in the estimates of instantaneous bead passage; the numbers of beads passing through the channel consistently moves up or down every other sampling period as the MECs are alternated (Figures 5a and 6a). Interpolated values of bead passage (mean of values preceding and following) were used in place of omitted values in subsequent calculations (Figures 5b and 6b).

10 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

350000 a 300000

250000

200000

150000

100000 Beads passedBeads in 15 min 50000

0 1 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97 103 Number of 15-min sampling periods

250000 b 200000

150000

100000

Beads passedBeads in 15 min 50000

0 1 7 13 19 25 31 37 43 49 55 61 67 73 79 85 91 97 103 Number of 15-min sampling periods

Figure 5. Extrapolated rates of bead passage through the channel (beads/15 min) at Calabacillas collection site using both MECs (top) and with the faulty flow meter omitted (bottom).

11 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

250000 a 200000

150000

100000

Beads passedBeads in15 min 50000

0 1 4 7 1013161922252831343740434649525558616467707376798285 Number of 15-min sampling periods

100000 90000 b 80000

70000 60000

50000

40000 30000

Beads passedBeads in 15min 20000 10000

0 1 4 7 1013161922252831343740434649525558616467707376798285 Number of 15-min sampling periods

Figure 6. Extrapolated rates of bead passage through the channel (beads/15 min) at South Diversion Channel collection site using both MECs (top) and with the faulty flow meter omitted (bottom).

12 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Total number of beads passing a site in a 5-day period was estimated as the sum of a two-step calculation. First, the total number of beads passing a collection site during the sampling period was calculated as the sum of the beads passing through the channel in each 15-min collection period (beads/15 min). When 30-min collection periods were used, the number of beads passing through the channel was calculated (beads/30 min) and then divided in half, yielding two 15-min periods with equal numbers of beads. Second, the numbers of beads passing in days 2 through 5 were estimated from regression of the bead passage rates during the last few hours of the collection period. The power regression best fit the data from most sites. The estimated number of beads that passed each sampling location during days 2 through 5 was added to the numbers that passed during the sampling period to estimate total bead passage at each location for a 5-day period.

The method of estimating the bead passage during days 2 through 5 is less conservative than previous SWCA Environmental Consultants (SWCA) reports (Kehmeier et al. 2004; Widmer and Kehmeier 2006). The previous reports assumed an even rate of bead passage in days 3 through 5, yielding an overestimate of bead passage and conservative estimates of bead retention rates. This method could not be applied to the Rio Grande data, because bead collection occurred for shorter periods of time and the collection rates did not steady by the end of day 2 at several of the collection sites. When the bead collection rate from the end of day 2 was applied to days 3 through 5, the estimated number of beads passing the downstream sites was artificially high and often exceeded the number of beads that had passed the upstream site (i.e., indicating that the channel was producing beads rather than retaining them). The regression method of estimating bead passage in days 3 through 5 was considered more accurate, although producing less conservative estimates of bead retention.

The number of beads of each color passing different collection sites was analyzed using a simple empirical model that assumed a negative exponential decay between release and collection sites (Equation 1), and was used to calculate the instantaneous bead retention rate (r) between the sites:

=Δ+ )()( exBeadsxxBeads Δ⋅− xr (1)

Where: Δ+ xxBeads )( = number of beads reaching the bead collection site at river kilometer x + Δx ; xBeads )( = number of beads entering the reach at river kilometer x; r = bead retention rate (1/km); and Δx = distance traveled to the next downstream collection site (km). The negative sign on the retention rate (r) indicates a decrease in beads per kilometer, or the rate at which beads are retained and lost to downstream transport.

Model of Egg Retention in the Albuquerque and Isleta Reaches A spreadsheet model2 was constructed to simulate the fate of silvery minnow eggs over a 5- day period for a natural spawn. The analysis model (Equation 1) used to calculate bead retention rates for each study reach was used to predict downstream egg transport in 1-km increments (Δx = 1).

2 Spreadsheet model used was developed by Orrin B. Myers, University of New Mexico

13 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

The approximate spring distribution of the silvery minnow was derived from catch per unit effort data (fish per 100 cubic meters) collected in 2005 by the American Southwest Ichthyological Research Foundation in the months of April, May, and June. These capture data were assumed to accurately represent the relative silvery minnow densities at the sample locations. Mean fish densities were calculated for nine sites on the Rio Grande between Angostura and San Acacia. The calculated fish density from a sampling location was applied to every kilometer downstream of that location until the next sampling location was reached. The resulting distribution was assumed to represent the relative distribution of breeding adults in the Rio Grande. The proportion of adult silvery minnows per river kilometer was determined by normalizing the area under the distribution curve to one. The proportional distribution of adults in each river kilometer was assumed to represent the source and relative magnitude of eggs released during a natural spawning event.

Proportional egg distribution was input into each 1-km model grid cell. Reach-specific bead retention rates estimated in this study were used to calculate the number of eggs moving between model grid cells. For example, the number of eggs retained in a grid cell was calculated as the number of eggs entering the cell multiplied by [1 – exp(-r⋅Δx)]. Recall that Δx =1, so this term drops out in the model. The number of eggs entering a cell is the number spawned into the cell plus eggs from the upstream cell after subtracting retention. Model calculations were verified by inputting data from a given bead release and collection, and by reproducing the observed cumulative retention for the reach. The model was subsequently used to predict spatial patterns of per-kilometer egg retention and cumulative egg retention in the Rio Grande.

Egg retention models were run using the following:

1. The high flow ascending limb (Experiment 1) retention rates and the calculated spring silvery minnow population distribution.

2. The constant high flow and constant low flow (Experiments 2 and 3) retention rates combined (i.e., high flow retention rates were used in the Isleta Reach, and low flow retention rates were used in the Albuquerque Reach) and the calculated spring silvery minnow population distribution.

3. The high flow ascending limb (Experiment 1) retention rates and a hypothetical uniform silvery minnow population distribution.

The distribution of egg retention predicted by the model was compared to the distribution of silvery minnow in late summer (July, August, and September). Presumably, the silvery minnow population distribution would be largely influenced by young of the year fish in late summer, so correlation between late summer silvery minnow density and predicted egg retention would provide support for the model. Population distribution in late summer was determined as for the spring.

14 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

RESULTS

Rates of bead retention and transport varied among reaches and hydrologic conditions. However, the number of beads passing through the channel decreased with distance from the release sites for all three experiments. Peaks in beads collected (i.e., bead density) were observed at all collection sites shortly after the initial arrival of a bead pulse. High magnitude, short duration, rapidly decaying peaks in bead numbers were observed in collection sites closest to release sites. Consistent with flow patterns, smaller and more prolonged peaks of bead numbers were observed at collection sites farther from release sites.

In addition to beads, field crews collected silvery minnow eggs, larval fish, and young of year fish in the MECs. Silvery minnow eggs were collected at four sites in May during the high flow ascending limb experiment, with the highest numbers of eggs at San Acacia (Table 2). San Acacia was the only site in the Isleta Reach where silvery minnow eggs were collected in June during the constant high flow experiment; larger numbers of larval fish were collected at the other sites. Young of year fish were captured at relatively low densities in the Albuquerque Reach during the July low flow experiment, but no larval fish or silvery minnow eggs were observed. The collection of silvery minnow eggs at the majority of sites during the high flow ascending limb experiment supports observations that silvery minnow spawn following flood pulses and suggests that this first experiment best simulated a natural spawn.

Calculated bead velocity increased with river discharge: average bead velocities were highest during the high flow ascending limb experiment and lowest during the constant low flow experiment (Table 3). The maximum bead velocity calculated was 5.70 km/hr between 550 Bridge and Calabacillas in May. The minimum was 1.65 km/hr between Calabacillas and South Diversion Channel in July. In the Albuquerque Reach, the bead velocities in July were approximately half those observed at the same sites in May.

Specifics on hydrology, bead collection, and calculated bead retention are described separately for each experiment in the sections below.

15 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Table 2. Collection of silvery minnow eggs and fish by MECs during the three bead drift experiments.

Silvery Minnow Eggs Collected per Larval Fish or YOY Fish Collected 100 m3 Water Sampled per 100 m3 Water Sampled

Location High Flow High Flow Constant Constant Constant Constant Ascending Ascending High Flow Low Flow High Flow Low Flow Limb Limb

550 Bridge 0.02 - 0 0 - 0.22 YOY

Calabacillas 0.06 - 0 0 - 0.19 YOY South Diversion 0 - 0 0 - 0.29 YOY Channel Los Lunas 0.04 0 - 0 0.18 larvae -

Veguita - 0 - - 0.33 larvae -

San Acacia 5.05 11.98 - 0 0.05 larvae - - Site not sampled.

Table 3. Average bead velocities through study reaches during three sampling events in 2005 based on arrival of peak bead densities.

Bead Velocity (km/hr) Reach Reach Length High Flow Constant Constant (km) Ascending High Flow Low Flow Limb Below Angostura Diversion Dam to 550 9.30 4.39 - 3.49 Bridge 550 Bridge to Calabacillas 19.95 5.70 - 2.49

Calabacillas to South Diversion Channel 22.05 3.39 - 1.65

Below Isleta Diversion Dam to Los Lunas 18.02 * 3.38 -

Los Lunas to Veguita 29.45 - 3.02 -

Veguita to San Acacia 36.22 * 3.29 - * Could not calculate bead velocity from bead collection data. - Site not sampled.

16 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Experiment 1: High Flow Ascending Limb Beads were released into the channel below Angostura Diversion Dam shortly after the arrival of the flood pulse, which was created by a scheduled release of water from Cochiti Dam (Figure 7). The flood pulse increased river flows by approximately 500 cubic feet per second [cfs], and these higher flows were maintained for the duration of the experiment. The flows were high enough to inundate floodplain areas in the Isleta Reach, but not in the Albuquerque Reach.

Bead density in the channel decreased over time and with distance from the release site (Figure 8). The highest in-channel bead density was recorded at the 550 Bridge, 9.3 km downstream of the Angostura Diversion Dam release site. No yellow beads were collected at San Acacia, indicating 100% retention between the Albuquerque and Isleta reaches. Much of this retention may have occurred in the Isleta Reach, as only 1 of the 10.4 million orange beads released from below Isleta Diversion Dam was captured at San Acacia.

Calculated 5-day bead retention rates from the high flow ascending limb experiment ranged from r = -0.0195 (1.88% per km) in the reach between 550 Bridge and the South Diversion Channel to r = -0.1497 (13.8% per km) in the reach between South Diversion Channel and San Acacia (Table 4). At the highest retention rate, 5 km of river would be required to retain 50% of the eggs released at a point location and 15 km to retain 90%. At the lowest retention rate, 36 km of river would be required to retain 50% of the eggs released and 118 km to retain 90% (Table 5).

The retention of silvery minnow eggs was modeled through the Albuquerque and Isleta reaches using the bead retention rates from the high flow ascending limb experiment and spring silvery minnow population distribution. The sampling data indicated that silvery minnow were more abundant in the Isleta Reach than the Albuquerque Reach in April, May, and June of 2005, with the exception of relatively high silvery minnow density at the Central Avenue crossing in Albuquerque (RM 295). Large numbers of translocated and captive-bred silvery minnows have been released at the Central Avenue crossing by the USFWS and City of Albuquerque refugium staff, perhaps explaining this local abundance. The model found that 98.3% of the eggs produced in the Albuquerque and Isleta reaches would be retained upstream of the San Acacia Diversion Dam, with most retention occurring in the Isleta Reach (Figure 9). Approximately 23.5% of the eggs produced in the Albuquerque Reach would be retained upstream of Isleta Diversion Dam, whereas 97.8% of the eggs produced in the Isleta Reach would be retained upstream of San Acacia Diversion Dam.

17 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

6000

5500

5000

Angostura Modeled (cfs) Modeled Flow Rate

550 Bridge

South Diversion Channel 4500 Isleta

San Acacia

Time of Yellow Bead Release

Time of Yellow Peak Bead Density

4000 5/9/2005 5/10/2005 5/11/2005 5/12/2005 5/13/2005 5/14/2005 5/15/2005 5/16/2005 5/17/2005 5/18/2005

Date

Figure 7. Modeled hydrograph during the high flow ascending limb experiment.

18 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

1,200,000 550 Bridge

South Diversion Channel

1,000,000 San Acacia

800,000

600,000

400,000 Passage (beads 15 min) /

200,000

0 9:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 5/12/2005 5/13/2005

Date and Time

Figure 8. Instantaneous number of yellow beads passing through the river channel at each collection site during the high flow ascending limb experiment.

19 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Table 4. Total numbers of beads released and collected, estimated bead totals, and reach-specific retention rates during the high flow ascending limb experiment. Empty cells indicate no beads were released, collected, or estimated at that site. South Angostura 550 Bridge Diversion Isleta San Acacia Channel River Kilometer 337.15 327.82 285.82 272.46 188.77 Reach Length 0 9.33 42 13.36 83.69 (km) Actual Number of Beads Released (in bold) and Collected Yellow 10,140,000 2,091 548 0 Orange 10,140,000 1 Estimated Number of Beads that Passed Collection Site During Sampling Yellow 4,620,978 2,037,097 0 Orange 1,990 Estimated Number of Beads that Passed Collection Site Between Sampling and Day 5 Yellow 7,464 85 0 Orange 0 Estimated Total Beads Passed After 5 Days (% of Total Released) 4,628,442 2,037,182 0 Yellow (45.6%) (20.1%) (0%) 1,990 Orange (0.02%) Bead Retention Rate (r) in Reach Immediately Upstream All -0.0843 -0.0195 -0.1497

Table 5. Distance (km) to retain different proportions of eggs at transport rates observed during the high flow ascending limb experiment.

Transport Kilometers Necessary to Retain Different Proportions (%) of River Reach Rate Eggs (1/km) 10% 25% 50% 75% 90% Below Angostura Diversion Dam to 550 -0.0843 1 3 8 16 27 Bridge 550 Bridge to -0.0195 5 15 36 71 118 South Diversion Channel South Diversion Channel -0.1497 1 2 5 9 15 to San Acacia

20 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

a ge ur t id nas ta s Br u i labacillas C ngo a D A 550 C S Isleta Los L Vegu San Acacia 2.5 -0.0843 -0.0195 -0.1497 100

Proportion of Eggs Retained 90

2.0 Proportion of Silvery Minnow, 80 Spring 2005

Proportion of Silvery Minnow, 70 Late Summer 2005

1.5 Cumulative Egg Retention 60

50

1.0 40 Proportion Per Km (%)

30 Cumulative Eggs Retained (%)

0.5 20

10

0.0 0 0 102030405060708090100110120130140150 Distance from Angostura Dam (km)

Figure 9. Modeled egg retention in the Albuquerque and Isleta reaches based on bead retention rates observed during the high flow ascending limb experiment and calculated spring silvery minnow population distribution.

21 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Experiment 2: Constant High Flow The constant high flow experiment examined retention in the Isleta Reach of the Rio Grande. Beads were released below Isleta Diversion Dam and collected downstream during a period of stable flow, approximately 5,250 cfs (Figure 10). This constant high flow level is slightly lower than flows observed during the high flow ascending limb experiment after the arrival of the flood pulse. The floodplain was not inundated in the Isleta Reach during the constant high flow experiment.

A sharp peak in bead density occurred at Los Lunas that decayed rapidly but did not stabilize over the collection period; small peaks in bead density were observed toward the end of the field sampling period (Figure 11). Peaks in bead density at the other sites were more prolonged and of smaller magnitude.

Calculated 5-day retention rates from the constant high flow experiment were fairly consistent and ranged from r = -0.0436 (4.3% per km) in the reach between Los Lunas and Veguita to -0.0504 (4.9% per km) in the reach between Veguita and San Acacia (Table 6). At the highest retention rate, 14 km of river would be required to retain 50% of the eggs released at a point location and 46 km to retain 90%. At the lowest retention rate, 16 km of river would be required to retain 50% of the eggs released and 53 km to retain 90% (Table 7).

The retention of silvery minnow eggs was modeled through the Isleta Reach using the bead retention rates from the constant high flow experiment and spring silvery minnow population distribution. The model found that 82.9% of the eggs produced in the Isleta Reach would be retained upstream of San Acacia Diversion Dam under constant high flow (Figure 12). This is 14.9% less than the total predicted to be retained under high flow ascending limb.

22 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

6000 Isleta

Los Lunas

Veguita 5500 San Acacia

Time of Bead Release

Time of Peak Bead Density 5000

4500 Modeled FlowModeled Rate (cfs)

4000

3500 6/18/2005 6/19/2005 6/20/2005 6/21/2005 6/22/2005 6/23/2005 6/24/2005 6/25/2005 6/26/2005 6/27/2005 6/28/2005 Date

Figure 10. Modeled hydrograph during the constant high flow experiment.

23 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

600,000 Los Lunas

Veguita 500,000 San Acacia

400,000

300,000

200,000 Passage (beads 15 min) /

100,000

0 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 0:00 1:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 6/22/2005 6/23/2005 6/24/2005

Date and Time

Figure 11. Instantaneous number of red beads passing through the river channel at each collection site during the constant high flow experiment.

24 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Table 6. Total numbers of beads released and collected, estimated bead totals, and reach- specific retention rates during the constant high flow experiment. Empty cells indicate no beads were released, collected, or estimated at that site.

Isleta Los Lunas Veguita San Acacia

River Kilometer 272.46 254.44 224.99 188.77 Reach Length 0 18.02 29.45 36.22 (km) Actual Number of Beads Released (in bold) and Collected

Red 10,140,000 1,169 574 175

Estimated Number of Beads that Passed Collection Site During Sampling

Red 4,184,149 1,124,532 186,651

Estimated Number of Beads that Passed Collection Site Between Sampling and Day 5

Red 1,669 34,607 4

Estimated Total Beads Passed After 5 Days (% of Total Released)

Red 4,185,818 (41.3%) 1,159,139 (11.4%) 186,655 (1.8%)

Bead Retention Rate (r) in Reach Immediately Upstream

All -0.0491 -0.0436 -0.0504

Table 7. Distance (km) to retain different proportions of eggs at transport rates observed during the constant high flow experiment.

Transport Kilometers Necessary to Retain Different Proportions (%) of Eggs River Reach Rate (1/km) 10% 25% 50% 75% 90%

Below Isleta Diversion -0.0491 2 6 14 28 47 Dam to Los Lunas

Los Lunas to Veguita -0.0436 2 7 16 32 53

Veguita to San Acacia -0.0504 2 6 14 28 46

25 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

s a aci una c L A leta s eguita an Is Lo V S -0.0491 -0.0436 -0.0504 3.0 100

90 Proportion of Eggs Retained 2.5 80 Proportion of Silvery Minnow, Spring 2005 70 2.0 Proportion of Silvery Minnow, Late Summer 2005 60 Cumulative Egg Retention 1.5 50

40 Proportion Per Km (%) 1.0 30 Cumulative Eggs Retained (%) Retained Eggs Cumulative

20 0.5

10

0.0 0 0 1020304050607080 Distance from Isleta Dam (km)

Figure 12. Modeled egg retention in the Isleta Reach based on bead retention rates observed during the constant high flow experiment and calculated spring silvery minnow population distribution.

26 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Experiment 3: Constant Low Flow The constant low flow experiment examined retention in the Albuquerque Reach of the Rio Grande. Beads were released below Angostura Diversion Dam and collected downstream during a period of relatively stable flow, approximately 1,700 cfs (Figure 13). This constant low flow level was about 3,500 cfs below flows in the previous experiments. No overbank flows were observed during either experiment in this reach.

Distinct peaks in bead density were observed at 550 Bridge and Calabacillas, and a smaller- magnitude, prolonged peak was recorded at South Diversion Channel (Figure 14). The magnitude of the peak bead density at 550 Bridge and South Diversion Channel was about half of the peak during the high flow with ascending limb experiment.

Calculated 5-day retention rates from the constant high flow experiment were fairly consistent and ranged from r = -0.0051 (0.5% per km) in the reach between 550 Bridge and Calabacillas to -0.1202 (11.3% per km) in the reach between Angostura and 550 Bridge (Table 8). At the highest retention rate, 6 km of river would be required to retain 50% of the eggs released at a point location and 19 km to retain 90%. At the lowest retention rate, 136 km of river would be required to retain 50% of the eggs released and 451 km to retain 90% (Table 9).

Unusually high rates of bead retention were observed in the reach between Angostura Diversion Dam and 550 Bridge in both May (-0.0843) and July (-0.1202); it is uncertain whether these retention rates are legitimate, or if the 550 Bridge collection site was located too close to the release site. If there was not sufficient distance between the release and collection sites, the beads may not have been allowed enough time to mix evenly throughout the channel.

The retention of silvery minnow eggs was modeled through the Albuquerque Reach using the bead retention rates from the constant low flow experiment and spring silvery minnow population distribution. The model found that only 15.02% of the eggs produced in the Albuquerque Reach would be retained upstream of Isleta Diversion Dam under constant low flow (Figure 15). This is 8.5% less than the total predicted to be retained under high flow ascending limb.

27 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

2200

Angostura

Highway 550

2000 Calabacillas

South Diversion Channel

1800 Time of Bead Release

Time of Peak Bead Collection

1600 Modeled Flow Rate (cfs)

1400

1200

1000 7/3/2005 7/4/2005 7/5/2005 7/6/2005 7/7/2005 7/8/2005 7/9/2005 7/10/2005 7/11/2005 7/12/2005 7/13/2005 Date

Figure 13. Modeled hydrograph during the constant low flow sampling event.

28 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

700,000 550 Bridge

Calabacillas 600,000 South Diversion Channel

500,000

400,000

300,000 Passage(Beads min) 15 / 200,000

100,000

0 7:00 8:00 9:00 0:00 1:00 2:00 3:00 4:00 5:00 6:00 7:00 8:00 9:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 22:00 23:00 10:00 11:00 12:00 13:00 14:00 15:00 16:00 17:00 18:00 19:00 20:00 21:00 7/7/2005 7/8/2005

Date and Tim e

Figure 14. Instantaneous number of red beads passing through the river channel at each collection site during the July sampling event.

29 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Table 8. Total numbers of beads released and collected, estimated bead totals, and reach-specific retention rates during the constant high flow experiment. Empty cells indicate no beads were released, collected, or estimated at that site. South Diversion Angostura 550 Bridge Calabacillas Channel River Kilometer 337.15 327.82 307.87 286.14

Reach Length (km) 0 9.33 19.95 21.73

Actual Number of Beads Released (in bold) and Collected

Yellow 10,140,000 5,604 3,684 3,021

Estimated Number of Beads that Passed Collection Site During Sampling

Yellow 3,206,792 2,650,797 1,809,005

Estimated Number of Beads that Passed Collection Site Between Sampling and Day 5

Yellow 96,281 333,351 469,476

Estimated Total Beads Passed After 5 Days (% of Total Released)

Yellow 3,303,073 (32.6%) 2,984,148 (29.4%) 2,278,481 (22.5%)

Bead Retention Rate (r) in Reach Immediately Upstream

All -0.1202 -0.0051 -0.0124

Table 9. Distance (km) to retain different proportions of eggs at transport rates observed during the constant low flow experiment.

Transport Kilometers Necessary to Retain Different Proportions (%) of River Reach Rate Eggs (1/km) 10% 25% 50% 75% 90% Below Angostura Diversion Dam to 550 -0.1202 1 2 6 12 19 Bridge 550 Bridge to -0.0051 21 56 136 272 451 Calabacillas Calabacillas to -0.0124 8 23 56 112 186 South Diversion Channel

30 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

s e a ill ura idg st ac o b la ng 50 Br DC A 5 Ca S 7.0 -0.1202 -0.0051 -0.0124 100

Proportion of Eggs Retained 90 6.0 Proportion of Silvery Minnow, 80 Spring 2005

5.0 Proportion of Silvery Minnow, 70 Late Summer 2005

Cumulative Egg Retention 60 4.0

50

3.0 40 Proportion Per Km (%)

30 2.0 CumulativeRetained (%) Eggs

20 1.0 10

0.0 0 0 1020304050 Distance from Angostura Dam (km)

Figure 15. Modeled egg retention in the Albuquerque Reach based on bead retention rates observed during the constant low flow experiment and calculated spring silvery minnow population distribution.

31 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Summary of Reach-wide Retention

The overall per-km retention in the Isleta Reach was 4.8 times higher than overall retention in the Albuquerque Reach during the high flow ascending limb experiment (Table 10). The overall per-km retention rate for the Isleta Reach was 3.1 times higher in the Isleta Reach during the high flow ascending limb experiment (r = -0.1497) than during the constant high flow experiment (r = -0.0477), presumably due to the availability of floodplain storage areas during the high flow ascending limb experiment. The difference in bead retention in the Albuquerque Reach between the high flow ascending limb and constant low flow experiments was less dramatic. The overall per-km retention in the Albuquerque Reach was only 1.06 times higher during the high flow ascending limb experiment (r = -0.0313) than the constant low flow experiment (r = -0.0293).

Table 10. Reach-wide retention rates calculated from the three bead retention experiments.

Reach-wide Bead Retention Rate (% retained per km) Reach High Flow Ascending Constant Low Constant High Flow Limb Flow

Albuquerque -0.0313 (3.1%) - -0.0293 (2.9%)

Isleta -0.1497* (13.9%) -0.0477 (4.7%) -

*Calculated from South Diversion Channel to San Acacia.; - Not sampled

Comparison of Bead Retention and Silvery Minnow Distribution

Based on catch data in 2005, the distribution of the silvery minnow population shifted downstream between spring and late summer in 2005 (Figure 9). These additional fish could be young of year (i.e., new fish) or adults that moved downstream after spawning; the catch per unit effort data were not size specific. During both seasons, the highest silvery minnow density in the study area was observed in the Isleta Reach, especially in the section between river kilometers 260 and 211. This section had relatively high rates of bead retention in both the high flow ascending limb and constant high flow experiments. Compared to the Isleta Reach, catch data indicated that silvery minnow were relatively scarce in the Albuquerque Reach. Bead retention was relatively poor in this reach, except between Angostura Diversion Dam and 550 Bridge.

Comparison of Modeled Egg Retention Using Hypothetical Uniform Distribution

Silvery minnow egg retention was modeled using a hypothetical uniform silvery minnow distribution and bead retention from the high flow ascending limb experiment (Figure 16). The comparison between this model and the same model using the calculated spring silvery minnow distribution (Figure 9) examines the influence on silvery minnow distribution on predicted cumulative egg retention. The predicted number of eggs to be cumulatively

32 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande retained in the Albuquerque and Isleta reaches was not greatly different between the two models: 95.9% (uniform distribution) compared to 98.3% (spring distribution). However, the distribution of retained eggs changed; the percentage of eggs predicted to be retained in the Albuquerque Reach increased from 23.5% to 35.5%. Population distribution had the greatest influence on predicted egg retention in the reach that exhibited the poorest bead retention. Given the relatively poor bead retention rates observed in most of the Albuquerque Reach during the high flow on ascending limb, the model predicts that 118 km would be required to retain 90% of the eggs from their release location. The Albuquerque Reach is only 64.7 km long, so the point at which the eggs are released had a large influence on whether the eggs were predicted to be retained upstream of Isleta Dam. Accordingly, the model with the highest number of silvery minnow on the upstream end of the Albuquerque Reach (the uniform population distribution model) predicted the highest percentage of eggs retained upstream of Isleta Dam. Silvery minnow distribution was predicted to have less influence on total in-reach egg retention in the Isleta Reach because relatively few kilometers would be required to retain eggs (15 km to retain 90% during high flow ascending limb conditions).

33 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

ra ge illas u c rid a ta ost B ui g 50 eg An 5 Calab SDC Isleta Los Lunas V San Acacia -0.0843 -0.0195 -0.1497 3.5 100

Proportion of Eggs Retained 90 3.0 Proportion of Silvery Minnow, 80 Spring 2005

2.5 Cumulative Egg Retention 70

60 2.0

50

1.5 40 Proportion Per Km (%)

30 1.0 (%) Retained Eggs Cumulative

20 0.5 10

0.0 0 0 102030405060708090100110120130140150 Distance from Angostura Dam (km)

Figure 16. Modeled egg retention in the Albuquerque and Isleta reaches based on bead retention rates observed during the high flow ascending limb experiment and hypothetical uniform silvery minnow population distribution.

34 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

DISCUSSION

The high snowmelt runoff flows in 2005 enabled this study to examine bead retention under three different hydrologic conditions (Figure 2). River discharge during the high flow ascending limb experiment and constant high flow experiment far exceeded the drought-level flows observed in the previous 5 years (2000 through 2004). These two high flow experiments examined retention under conditions that were favorable for silvery minnow spawning, as evidenced by the number of silvery minnow eggs captured during these experiments. A 50-fold increase in silvery minnow abundance documented between October 2004 and October 2005 (Dudley et al. 2005) confirmed that 2005 was an exceptionally important year for the silvery minnow population in the Middle Rio Grande.

Silvery minnow recruitment appears to be correlated with the magnitude and duration of spring and summer flows, and therefore also correlated with the availability of nursery habitat and other egg retention habitats. For the years 1993 through 2005, mean October catch rates of silvery minnow were significantly positively correlated with the magnitude and duration of peak flows during the spawning season (May through June) and negatively correlated with periods of low flow (Dudley et al. 2005). Historically, years of good snowpack produced flows in the Middle Rio Grande that peaked in late spring and resulted in periods of sustained flooded habitat (Dudley et al. 2005). The above average spring runoff in 2005 inundated mid- channel and bank-attached bars for several weeks, providing ample habitat for rearing silvery minnow (Porter and Massong 2006).

Bead retention was substantially higher in the Isleta Reach than the Albuquerque Reach during the high flow ascending limb experiment, although flow magnitude was similar in both reaches. The high flow ascending limb egg retention model indicated that about 23.5% of the eggs released by silvery minnow in the Albuquerque Reach would be retained upstream of Isleta Diversion Dam and 97.8% of the eggs produced in the Isleta Reach would be retained upstream of San Acacia (Figure 9). Most of the eggs produced in the Albuquerque Reach that pass the Isleta Diversion Dam and are not diverted into the Isleta Diversion Channel were predicted to be retained upstream of the San Acacia Diversion Dam because of the high retention rates observed in the Isleta Reach. The number of eggs that might be lost to the channel was not evaluated by this study. Differences in bead retention rates between the reaches during the high flow ascending limb experiment are likely due to changes in the channel shape and degree of interaction between the channel bed and flows, especially inundation of vegetated surface areas. Porter and Massong (2006) found that bead retention in the Rio Grande, New Mexico, was generally highest in flooded shoreline areas (especially shelves) and on flooded island and sand bar surfaces, habitat features most abundant at high flow. At a river discharge of 5,700 cfs, minor overbank flooding occurs upstream of Isleta and more substantial overbank flooding occurs downstream (Mussetter Engineering, Inc. 2002). Overbank flows were observed in the Isleta Reach, but not the Albuquerque Reach, during the high flow ascending limb experiment. Overbank storage due to floodplain connection could account for the greatly increased bead retention in the Isleta Reach.

The bead retention rates in the Albuquerque and Isleta reaches were higher during the high flow ascending limb experiment than during the constant flow experiments. The bead retention rate was 3.1 times higher during the high flow ascending limb experiment than the

35 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande constant high flow experiment in the Isleta Reach and 1.1 times higher during the high flow ascending limb experiment than the constant low flow experiment in the Isleta Reach. Bead retention rates at high and low flows could not be directly compared in this study because those experiments occurred in different reaches. Flows were constrained by the river channel during both experiments in the Albuquerque Reach, although greater inundation of in-channel features (e.g., islands) during the high flow ascending limb experiment may have caused the observed increase in egg retention over the low flow experiment. In-channel features were inundated during both experiments in the Isleta Reach, but the floodplain was only connected during the high flow ascending limb experiment. This floodplain connection and the timing of the bead release to take advantage of increasing channel and floodplain storage appears to have greatly increased bead retention in the Isleta Reach over the already high rate of bead retention under constant high flow conditions. These results suggest that inundated in- channel features retained beads, but at a smaller magnitude than the connected floodplain. Although the same mechanisms may have been responsible for retaining beads (e.g., inundated vegetation) both in the floodplain and on in-channel features, the surface area of the floodplain would be much greater.

Fish sampling data indicated that the majority of the silvery minnow above San Acacia Diversion Dam were located in river kilometers 260 through 211 in spring 2005 (Figure 9), extending from 6 km north of Los Lunas to 14 km south of Veguita. Consistent with this observation, most of the silvery minnow eggs collected during the study were downstream of the Los Lunas to Veguita reach, with the highest numbers of eggs collected at the San Acacia site (Tables 4 and 6). The distribution of silvery minnow did not change greatly between spring and late fall in 2005 (Figure 9). The translocated and/or stocked fish that were abundant at the Central Avenue crossing in the spring had dispersed by late summer. The population distribution also appeared to shift downstream between spring and late summer, with higher densities of fish observed in the Isleta Reach in late summer than spring. The increase in silvery minnow density in the Isleta Reach may have been caused by an influx of young of year fish in the downstream reach or the downstream movement of adults. The silvery minnow distribution in both seasons appears to be roughly correlated with the calculated rates of bead retention, except for the section between Angostura Diversion Dam and 550 Bridge, which had high bead retention but few fish (Figure 9 and Figure 15). These findings are consistent with those on the Pecos River, where Pecos bluntnose shiner abundance was also positively correlated with bead retention rate (Kehmeier et al. 2004).

The short section between Angostura Diversion Dam and 550 Bridge had exceptionally high egg retention rates both in the high flow ascending limb experiment (r = -0.0843) and constant low flow experiment (r = -0.1202). The beads were released directly into the thalweg at Angostura Diversion Dam and should have quickly mixed throughout the river channel. However, it is possible that the distance between Angostura Diversion Dam and 550 Bridge (9.3 km) was not adequate to allow even mixing throughout the channel. Sampling at 550 Bridge in May occurred adjacent to the thalweg (Appendix A). If the bead density adjacent to the thalweg was lower than bead density in the thalweg, the egg retention rate upstream would have been overestimated and the egg retention downstream underestimated. A similar problem occurred in a 9.6-km reach on the Pecos River above Sumner Dam, although sampling had occurred much further from the thalweg in that study (Widmer and Kehmeier 2006). It is also possible that egg retention really was exceptionally high below Angostura

36 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Diversion Dam, since the Santa Ana Pueblo Tribe had recently completed river restoration work in this reach.

To create a sustainable population of silvery minnow in the Albuquerque Reach, the results of this study indicate that egg retention needs to be improved and the silvery minnow population supplemented at the upstream end of this reach. Over 50% of the eggs produced in the Albuquerque Reach were modeled to drift downstream into the Isleta Reach using the bead retention rates calculated from both the high flow ascending limb and constant low flow experiments. At the retention rates observed in the majority of the Albuquerque Reach (i.e., excluding Angostura Diversion Dam to 550 Bridge), 36 km would be required to retain 50% of the eggs produced during high flow ascending limb conditions from the point of release, and 56 to 136 km would be required during constant low flow conditions (Table 5). For reference, the Albuquerque Reach is 64.7 km in length. Less than 50% of the eggs produced in the Albuquerque Reach were predicted to be retained because the majority of silvery minnow were located in the downstream half of the reach in 2005. Modeled egg retention in the Albuquerque Reach would increase if the egg retention rate were increased or if the silvery minnow distribution were shifted upstream.

The Bureau of Reclamation has conducted several years of research in the Albuquerque Reach to identify channel features that retain silvery minnow eggs in the Middle Rio Grande and to evaluate the relative effectiveness of man-made nursery habitats (shoreline inlets) using gellan beads (Porter and Massong 2003, 2004b, 2006). Eggs and beads were retained in both off-channel inlets and in constructed nursery habitats, although natural inlets had higher rates of egg retention and appeared less prone to sedimentation between years (Porter and Massong 2003, 2004b; Massong et al. 2004). Highest bead retention was in Arroyo Calabacillas (Calabacillas), a natural habitat where channels in the arroyo fan become inundated at high water. Most of the beads retained at this site were observed to “linger” on a vegetated shelf outside the inlet; few beads were observed entering the inlet directly from the Rio Grande channel (Porter and Massong 2004b, Massong et al. 2004). Subsequent sampling in the Albuquerque Reach (April, May, and June 2005) found highest gellan bead retention on shelves (68.2% of total captured), in inlets (8.5%), and around large woody debris (7.4%). Larval fish were primarily captured in inlets (42.5%), shelves (31.8%), and side channels (22.9%). Eggs and larval fish were also captured on mid-channel and bank-attached bars (Porter and Massong 2006).

The findings of the present study superficially conflict with those of Porter and Massong (2004b), who reported the highest bead retention at Calabacillas. Although the movement of beads substantially slowed through the Calabacillas section in both Albuquerque Reach experiments (Table 3), the reach from 550 Bridge to South Diversion Channel (encompassing the Calabacillas section) demonstrated the lowest egg retention rates in the study area (Tables 4 and 8). Differences in the results of the two studies are likely due to the scales at which bead retention was evaluated. While the egg retention at Calabacillas may be high locally, as reported by Porter and Massong (2004b), the reach as a whole may have poor retention as reported here. If so, retention in the reach could potentially be improved if the channel were modified to contain more of the physical features observed locally at Calabacillas.

37 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

The New Mexico Interstate Stream Commission (NMISC) has proposed to develop and construct silvery minnow habitat within the Albuquerque Reach of the Rio Grande to increase the retention of drifting eggs, create nursery habitats for larval fish, and provide low-velocity winter habitats for adult and juvenile fish. Towards this end, the NMISC started a 35-acre river restoration project in the Albuquerque Reach in late December 2005, months after the completion of the field portion of this study. Monitoring is ongoing to evaluate the efficacy of restoration techniques and their contribution to the riverine environment and the recovery goals of the silvery minnow. With only one year of monitoring data, it is not yet known if this restoration project has substantially increased egg retention in the reach. The NMISC has also recently (January 2007) begun work to modify 85 acres of riparian habitat in the Albuquerque Reach. It may be useful to repeat this study after the completion of these habitat restoration projects to evaluate whether bead retention in the Albuquerque Reach is increased.

Silvery minnow stocking is recommended after habitat restoration in the Albuquerque Reach. Movement studies indicate that hatchery-raised individuals can be released back to the wild with adequate retention in or near original release sites (Platania et al. 2003; Remshardt 2005), can experience survival of at least 2 years after release, and may ultimately contribute to future spawning efforts (Remshardt 2005). Even if egg production is not increased in the Albuquerque Reach through silvery minnow stocking, low numbers of eggs and larvae can result in greatly increased recruitment success if sufficient nursery habitat is made available (Dudley et al. 2005).

Bead retention rates observed in the Isleta Reach in June were comparable to the highest retention rates observed on the Pecos River (Dudley and Platania 2000; Kehmeier et al. 2004; Widmer and Kehmeier 2006), although it is important to consider that a more conservative method was used to calculate the bead retention rates in the Pecos River studies than in the present study. A study of the egg retention habitat in the Isleta Reach between river kilometers 260 and 211 could provide valuable insight for habitat restoration efforts in the Albuquerque Reach and elsewhere. As flows may become intermittent in the Isleta Reach during dry years, it would also be worthwhile to identify the areas of highest egg retention and evaluate flows in those areas. If flows are not continuous in highly productive areas, focused efforts might be made to provide year-round water to these locations.

38 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

CONCLUSIONS

• Bead retention was substantially higher in the Isleta Reach than the Albuquerque Reach. However, egg retention models suggest that the majority (>90%) of eggs that drift from the Albuquerque Reach into the Isleta Reach would be retained upstream of San Acacia. • Bead retention was highest in both the Albuquerque and Isleta reaches when beads were released on the ascending limb of the hydrograph, the period when the inundation of floodplain and in-channel features was highest. • Connected floodplain areas may be capable of retaining large numbers of silvery minnow eggs. The influence of overbank flows appeared to be much greater than the influence of inundated in-channel features on bead retention, perhaps due to the relative surface areas inundated. • Silvery minnow distribution (calculated from catch rate data) appears roughly correlated with the calculated bead retention rates. The highest silvery minnow densities were observed in the Isleta Reach, an area that had high bead retention rates in both the high flow ascending limb and constant high flow experiments. • In order to create a sustainable population of silvery minnow in the Albuquerque Reach, improvements need to be made to egg retention habitat and adult habitat.

RECOMMENDATIONS

• Build on the work done by the Bureau of Reclamation to identify the habitat features that most efficiently entrain silvery minnow eggs, especially in the Isleta Reach. Use this data to inform habitat improvement projects. • Improve habitat in the Albuquerque Reach to enhance egg retention. • Consider repeating this experiment in the Albuquerque Reach to evaluate the improvement in egg retention after completion of habitat improvement projects. Keep in mind, however, the sensitivity of this study design may not be sufficient to detect a difference. • Stock silvery minnow in the Albuquerque Reach during or after the completion of habitat improvement projects in this reach. Stock fish in the upstream end of the reach, near Angostura Diversion Dam, if habitat is appropriate. • Identify areas of highest bead retention in the Isleta Reach and then evaluate year- round flow conditions in those areas. If flows are intermittent, focused efforts to provide continuous flow to these locations may improve silvery minnow recruitment.

39 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

REFERENCES

Altenbach, C.S., R.K. Dudley, and S.P. Platania. 2000. A new device for collecting drifting semibuoyant fish eggs. Transactions of the American Fisheries Society 129(1):296–300.

Bestgen, K.R., and S.P. Platania. 1991. Status and conservation of the Rio Grande silvery minnow, Hybognathus amarus. The Southwestern Naturalist 36(2):225-232.

Cowley, D.E., J. Alleman, R.R. McShane, P.D. Shirey, and R. Sallenave. 2005. Effects of salinity and suspended sediment on physical properties of the egg of Rio Grande silvery minnow (Hybognathus amarus). New Mexico Water Resources Research Institute, New Mexico State University, Las Cruces, NM. May 2005. 13 pp.

Davin, W.T., C. Ethridge, C. Babb, and S. Hileman. 1999. Estimation of striped bass (Morone saxatilis) egg drift rate in the lower Savannah River. Final report to the U.S. Army Corps of Engineers, Savannah District. December 1999. 68 pp.

Dudley, R.K., and S.P. Platania. 2000. Downstream transport rates of drifting semibuoyant cyprinid eggs and larvae in the Pecos River, NM. Division of Fishes, Museum of Southwestern Biology, Department of Biology, University of New Mexico, Albuquerque. 57 pp.

Dudley, R.K., and S.P. Platania. 2001. 2000 population monitoring of Rio Grande silvery minnow. Prepared for the U.S. Bureau of Reclamation, Albuquerque, NM by the NM Ecological Services Field Office, Albuquerque, NM, U. S. Fish and Wildlife Service.

Dudley, R.K., and S.P. Platania. 2002. 2001 population monitoring of Rio Grande silvery minnow. Prepared for the U.S. Bureau of Reclamation, Albuquerque, NM by the NM Ecological Services Field Office, Albuquerque, NM, U. S. Fish and Wildlife Service.

Dudley, R.K., S.P. Platania, and S.J. Gottlieb. 2005. Rio Grande silvery minnow population monitoring program results from 2004. Prepared for the U.S. Bureau of Reclamation, Albuquerque, NM, by the American Southwest Ichthyological Research Foundation, Albuquerque, NM. April 15, 2005. 50 pp.

Hatch, M., and C. Altenbach. 2006. Personal communication with Joseph Fluder, SWCA. June 2006.

Kehmeier, J.W., C.N. Medley, and O.B. Myers. 2004. Assessment of Pecos bluntnose shiner egg and larval drift potential in the Pecos River, New Mexico. Prepared for the New Mexico Interstate Stream Commission, Albuquerque, NM, by SWCA Environmental Consultants, Albuquerque, NM. September 13, 2004. 39 pp.

Massong, T., M. Porter, and T. Bauer. 2004. Design improvements for constructed Rio Grande silvery minnow nursery habitat. U.S. Bureau of Reclamation Science and Technology Program, Albuquerque, NM. September 2004. 26 pp.

40 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Medley, C.N., J.W. Kehmeier, O.B. Meyers, and R.A. Valdez. In review. Simulated transport and retention of pelagic fish eggs during an irrigation release in the Middle Pecos River, New Mexico. Submitted to the Journal of Freshwater Ecology.

Mussetter Engineering, Inc. 2002. Geomorphic and sedimentologic investigations of the Middle Rio Grande between Cochiti Dam and Elephant Butte Reservoir. Prepared for the New Mexico Interstate Stream Commission, Albuquerque, NM.

Pease, A.A. 2004. An assessment of critical nursery habitat features for larval and juvenile fishes in the Middle Rio Grande, New Mexico. Master of Science thesis, University of New Mexico, Albuquerque, NM. August 2004. 34 pp.

Platania, S.P. 1995. Reproductive biology and early life-history of Rio Grande silvery minnow, Hybognathus amarus. Report prepared for the U.S. Army Corps of Engineers, Albuquerque, NM. February 15, 1995. 22 pp.

Platania, S.P., and C.S. Altenbach. 1998. Reproductive strategies and egg types of seven Rio Grande basin cyprinids. Copeia 3:559-569.

Platania, S.P., and R.K. Dudley. 2003. Spawning periodicity of Rio Grande silvery minnow, Hybognathus amarus, during 2002. Report prepared for the U.S. Bureau of Reclamation, Albuquerque, NM, by the American Southwest Ichthyological Research Foundation, Albuquerque, NM. June 10, 2003. 42 pp.

Platania, S.P., M.A. Farrington, W.H. Brandenburg, S.J. Gottlieb, and R.K. Dudley. 2003. Movement patterns of the Rio Grande silvery minnow Hybognathus amarus in the San Acacia Reach of the Rio Grande during 2002. Report prepared for the U.S. Bureau of Reclamation, Albuquerque, NM, by the American Southwest Ichthyological Research Foundation, Albuquerque, NM. June 10, 2003. 31 pp,

Porter, M.D., and T.M. Massong. 2003. Progress report 2003, contributions to delisting the Rio Grande silvery minnow: egg habitat identification. Bureau of Reclamation, Albuquerque, NM. September 2003. 12 pp.

Porter, M.D., and T.M. Massong. 2004a. Habitat fragmentation and modifications affecting distribution of the Rio Grande silvery minnow. GIS/Spatial Analyses in Fishery and Aquatic Sciences, Fishery and Aquatic GIS Research Group: 421-432.

Porter, M.D., and T.M. Massong. 2004b. Progress report 2004, contributions to delisting the Rio Grande silvery minnow: egg habitat identification. Bureau of Reclamation, Albuquerque, NM. September 2004. 18 pp.

Porter, M.D., and T.M. Massong. 2006. Progress report 2005, contributions to delisting the Rio Grande silvery minnow: egg habitat identification. Bureau of Reclamation, Albuquerque, NM. January 2006. 39 pp.

41 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Reinert, T.R., T.A. Will, C.A. Jennings, and W.T. Davin. 2004. Use of egg surrogates to estimate sampling efficiency of striped bass eggs in the Savannah River. North American Journal of Fisheries Management 24:704-710.

Remshardt, W.J. 2005. Experimental augmentation and monitoring of Rio Grande silvery minnow in the Middle Rio Grande, New Mexico: Annual report June 2003-May 2004. U.S. Fish and Wildlife Service, Albuquerque, NM. May 17, 2005. 38 pp.

Runkel, R.L. 1998. One-dimensional transport with inflow and storage (OTIS): A solute transport model for streams and rivers. U.S. Geological Survey, Water Resources Investigation Report 98-4018.

Schmidt-Petersen, R. 2007. Personal communication with Ann Widmer, SWCA. February 2007.

Tetra Tech, Inc. 2002. Development of the Middle Rio Grande Flo-2D Flood Routing Model Cochiti to Elephant Butte. Prepared for the Bosque Initiative Group, U.S. Fish and Wildlife Service, and U.S. Army Corps of Engineers. February 3, 2002.

URGWOPS DEIS. 2006. Draft environmental impact statement for the Upper Rio Grande water operations. Available http://www.spa.usace.army.mil/urgwops/deis/, accessed March 2007. January 2006.

U.S. Fish and Wildlife Service (USFWS). 2003. Designation of critical habitat for the Rio Grande silvery minnow. Federal Register 68(33):8087-8135.

Widmer, A.M., and J.W. Kehmeier. 2006. Artificial egg retention and displacement during a managed irrigation release in the Pecos River between Santa Rosa Dam and Sumner Reservoir, New Mexico. Prepared for the New Mexico Interstate Stream Commission, Santa Fe, NM, by SWCA Environmental Consultants, Broomfield, CO. November 2006. 28 pp plus appendices.

Will, T.A., T.R. Reinert, and C.A. Jennings. 2001. Assessment of spawning sites and reproductive status of striped bass, Morone saxatilis, in the Savannah River Estuary. Final report for project 10-21-RR251-144, January 2000 to January 2001. Report to the Georgia Ports Authority, Savannah, GA. 42 pp.

42 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

APPENDIX A Description of Bead Release and Collection Sites

Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Angostura Diversion Dam (Release Site) River Kilometer 337.18 • Beads were dispersed ~0.6 river miles below the dam into the thalweg during May and July. • In May, emergent vegetation was present at the release location • Substrate was sandy-silt with cobble

550 Bridge (Collection Site) River Kilometer 327.82 • In May beads were collected adjacent to the thalweg just off the left-bank o Sampling occurred 15-25 feet from what was then the bank • In July beads were collected adjacent to or within the thalweg off the left-bank of an exposed bar that was inundated in May • There was emergent vegetation present around the site in May • Substrate was cobble

Calabacillas Arroyo (Collection Site) River Kilometer 307.87 • In May beads were collected off the right-bank in a 75- to 90-foot channel o The river channel was partitioned into two channels; the 75- to 90-foot channel and the “main” portion of the river which was ~250-300 feet wide o Sampling occurred in the middle of the partitioned channel o The river was partitioned by a vegetated island o Flow was sufficient through the channel o Sampling could not be conducted in the “main” channel due to safety concerns o The 75- to 90-foot channel has flowing water all year round, even at flows <500 cfs o The channel was approximately 3 feet deep o The substrate was sandy-silt with cobble • In July beads were collect in the middle of the “main” channel within the thalweg o Jetties line the east bank, or left-bank, and facilitate an increase in depth o Depth varied with the shifting sand but was 1.5-2.5 feet deep o The substrate was predominantly sand o A storm event occurred near the end of the sampling period

South Diversion Channel (Collection Site) River Kilometer May 285.82; June 286.14 • In May beads were collected on the right-bank on an inundated bar with emergent vegetation o The substrate was predominantly sand o Depth varied from 1.5-2.5 feet deep o Sampling occurred 25-30 feet from the bank o The bar is not inundated at <1000 cfs o The channel is partitioned by a vegetated island o The thalweg hugs the left-bank of the river o Sampling could not occur in the thalweg due to safety concerns • In July beads were collected near the middle of the channel in or adjacent to the thalweg o Sampling occurred 25-30 feet from the bank o Depth varied from 2.0-3.0 feet deep

A-1 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

o The sampling site used in May was no longer inundated

Isleta Diversion Dam (Release Site) River Kilometer 272.46 • Beads were dispersed ~0.1/0.2 river miles below the dam into the thalweg during May and June • Emergent vegetation was present at the release location • The substrate was silty-sand

Los Lunas (Collection Site) River Kilometer 254.44 • In May beads were collected off the right-bank adjacent to the thalweg o Sampling occurred 15-40 feet from the bank • In June beads were collected off the right-bank adjacent to the thalweg o Sampling occurred 15-40 feet from the bank o The substrate was predominantly sand

Veguita (Collection Site) River Kilometer 224.99 • No sampling occurred in May • In June beads were collected upstream of Abo Arroyo o Two MECs were initially set-up in a narrow channel closer to the left-bank with minimal flow due to the fact that one person was working both MECs and safety concerns o Once the second person arrived, the MECs were separated by a sparsely vegetated island/bar with one MEC remaining in the narrow channel and the other being adjacent to the thalweg on the opposite side of the island o The substrate was predominantly shifting sands near the thalweg and sandy-silt with minimal cobble at the narrow channel

San Acacia (Collection Site) River Kilometer 188.77; Salado River Kilometer 190.70 • In May beads were collected along the right-bank adjacent to the thalweg (RK 117.3) o The river was not partitioned o Collection occurred 5 feet from the bank because of safety concerns o Depth was 2.5 to 4.0 feet o After a few hours the site was washed out and moved upstream to the Rio Salado inflow (RK 118.5) o This site had sandy-silt with cobble • In June beads were collected on the right-bank adjacent to the thalweg (RK 188.77) o Collection occurred only a few feet from the bank because of safety concerns o Substrate is typically sandy-silt with cobble at this location

A-2 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

APPENDIX B Maps of the Bead Release and Collection Sites

Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Figure B-1. Location of bead release site below Angostura Diversion Dam during the high flow ascending limb experiment (May) and constant low flow experiment (July).

B-1 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Figure B-2. Locations of bead collection sites below 550 Bridge during the high flow ascending limb experiment (May) and constant low flow experiment (July).

B-2 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Figure B-3. Locations of bead collection sites at Calabacillas during the high flow ascending limb experiment (May) and constant low flow experiment (July).

B-3 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Figure B-4. Locations of bead collection sites at South Diversion Channel during the high flow ascending limb experiment (May) and constant low flow experiment (July).

B-4 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Figure B-5. Location of bead release (drop) site below Isleta Diversion Dam during the high flow ascending limb experiment (May) and constant high flow experiment (June).

B-5 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Figure B-6. Locations of bead collection sites at Los Lunas during the high flow ascending limb experiment (May) and constant high flow experiment (June).

B-6 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Figure B-7. Location of the bead collection sites at Veguita during the constant high flow experiment (June).

B-7 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Figure B-8. Locations of bead collection sites at San Acacia during the high flow ascending limb experiment (May) and constant high flow experiment (June).

B-8 Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

APPENDIX C Bead Collection Dates and Times

Characterization of Rio Grande Silvery Minnow Egg and Larval Drift and Retention in the Middle Rio Grande

Table C-1. Bead collection dates and times. Begin End Total Collection Experiment Location Collection Collection Time (hours) 5/12/2005 at 5/13/2005 at 550 Bridge 21.75 08:15 06:00 5/12/2005 at 5/13/2005 at Calabacillas 26.25 11:15 13:30 High flow ascending South Diversion 5/12/2005 at 5/13/2005 at 21.25 limb Channel 15:45 13:00 5/13/2005 at 5/13/2005 Los Lunas 15.25 04:00 19:15 5/13/2005 at 5/14/2005 at San Acacia 26.50 15:45 18:15 6/22/2005 at 6/23/2005 Los Lunas 22.25 12:30 10:45 6/22/2005 at 6/23/2005 at Constant high flow Veguita 31.15 15:15 22:30 6/23/2005 at 6/25/2005 at San Acacia 20.25 05:00 01:15 7/7/2005 at 7/8/2005 at 550 Bridge 30.75 07:00 13:45 7/7/2005 at 7/8/2005 at Constant low flow Calabacillas 29.45 10:00 15:45 South Diversion 7/7/2005 at 7/8/2005 at 29.15 Channel 16:30 21:45

C-1