AN EXPERIMENTAL A N PECIES MONITORING AND C S UAN …...129 . 130 Table 4. Spearman’s rank correlation results testing temporal variation in median TL of Channel ... 144 by reach

AN EXPERIMENTAL APPROACH TO NONNATIVE 1 SPECIES MONITORING AND CONTROL IN THE SAN 2 JUAN RIVER: 2016-2017 3 DRAFT REPORT 4 PREPARED FOR: 5

SAN JUAN RIVER BASIN RECOVERY IMPLEMENTATION PROGRAM 6 7

PREPARED BY: 8

BOBBY R. DURAN 9

BRIAN A. HINES 10

NATHAN R. FRANSSEN 11

SCOTT L. DURST 12

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An Experimental Approach to Nonnative Species Monitoring and Control in the San Juan River: 2016-2017 Draft

NONNATIVE SPECIES MONITORING AND CONTROL EXPERIMENTAL DESIGN IN THE 23 SAN JUAN RIVER: 2016-2017 24

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PREPARED BY: 26

BOBBY R. DURAN 27

[email protected] 28

NEW MEXICO FISH AND WILDLIFE CONSERVATION OFFICE, 29

U.S. FISH AND WILDLIFE SERVICE, ALBUQUERQUE, NEW MEXICO 30

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BRIAN A. HINES 33


UTAH DIVISION OF WILDLIFE RESOURCES, MOAB, UTAH 35

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NATHAN R. FRANSSEN 38


AND 40

SCOTT L. DURST 41


SAN JUAN RIVER RECOVERY IMPLEMENTATION PROGRAM OFFICE, 43

U.S. FISH AND WILDLIFE SERVICE, ALBUQUERQUE, NEW MEXICO 44

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mailto:[email protected]:[email protected]:[email protected]


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SUBMITTED TO: 50

SAN JUAN RIVER BASIN RECOVERY IMPLEMENTATION PROGRAM 51

BIOLOGY COMMITTEE 52

5/16/1853

EXECUTIVE SUMMARY 54 55

1. The San Juan River’s nonnative fish control program was modified in 2016-2017 to 56 facilitate quantification of the effects of nonnative fish removal on native and nonnative 57 fishes. 58

59 60 2. The river between Shiprock, New Mexico and Mexican Hat, Utah was stratified by 61

geomorphic reach. Within each geomorphic reach, the river was further divided into 62 treatment (removal) and control reaches (no removal). 63

64 65 3. Age-specific exploitation rates for Channel Catfish were higher in 2016 (Upper section: 66

57.1% juveniles, 48.8% adults; Lower section: 15% juveniles, 20% adults) than 2017 67 (Upper section: 14.3% juveniles, 18.8% adults; Lower section: 11% juveniles, 9% adults). 68

69 70 4. Substantial variation in CPUE was observed among reaches over time and nonnative 71

removal effort showed little demonstrative effects. 72

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5. Population estimates in control and removal reaches were not affected by nonnative 74 removal in 2017. 75

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6. Nonnative fish removal did not alter the size structure of Channel Catfish in removal 78 reaches in 2016, but size of Channel Catfish in 2017 were significantly smaller in four out 79 of five removal reaches compared to their paired control reach. 80

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7. Nonnative fish removal did not alter the CPUE of Colorado Pikeminnow and had a 82 negative effect on CPUE of Razorback Sucker in removal reaches. 83

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8. Channel Catfish demonstrated high upstream movement rates in 2016; however, 85 movement rates in 2017 were less directional. 86

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9. Our results suggest the current rates of exploitation are too low to cause measurable 88 effects on the CPUE or population abundance Channel Catfish population due to 89 movement and recruitment of fish, but removal efforts are having measurable effects 90 on the size structure of the population. 91

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TABLE OF CONTENTS 93

EXECUTIVE SUMMARY .......................................................................................................................................... i 94

INTRODUCTION ................................................................................................................................................... 1 95

OBJECTIVES ........................................................................................................................................................ 2 96

METHODS .......................................................................................................................................................... 3 97

RESULTS ............................................................................................................................................................. 6 98

TEMPORAL VARIATION IN CPUE ..................................................................................................................... 7 99

TEMPORAL VARIATION IN POPULATION ESTIMATES OF CHANNEL CATFISH AND ENDANGERED FISHES .......................... 11 100

TEMPORAL VARIATION IN SIZE STRUCTURE OF CHANNEL CATFISH .......................................................................... 14 101

SPATIAL VARIATION IN SIZE STRUCTURE OF CHANNEL CATFISH.............................................................................. 16 102

EFFECTS OF REMOVAL ON CPUE OF FISHES ....................................................................................................... 17 103

CHANNEL CATFISH MOVEMENT ....................................................................................................................... 21 104

EXPLOITATION RATES..................................................................................................................................... 28 105

RARE FISH COLLECTIONS ................................................................................................................................ 29 106

DISCUSSION ........................................................................................................................................................ 30 107

LITERATURE CITED ............................................................................................................................................... 31 108

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LIST OF TABLES 117

Table 1. The total number of removal passes by specific river miles from treatment and control 118 reaches, Geomorphic Reach (Georeach), Section of River, and agency responsible for 119 removal efforts.………………………………………………………………………………………....……………………5 120

121 Table 2. Results from Spearman’s rank correlations testing for temporal variation in CPUE of each 122

species in each removal reach in the Upper Section of river in 2016 and 2017. Significant 123 correlations are denoted in bold font………………………….…………....………………………………….10 124

125 Table 3. Results from Spearman’s rank correlations testing for temporal variation in CPUE of each 126

species in each removal reach in the Lower Section of river 2016 and 2017. Significant 127 correlations are denoted in bold font…………………………………………………………………………….11 128

129 Table 4. Spearman’s rank correlation results testing temporal variation in median TL of Channel 130

Catfish among removal reaches in 2016 and 2017..……………………………………………………….16 131 132 Table 5. Results of Kruskal-Wallis nonparametric test results (and Dunn’s post hoc tests) for 133

differences in the TL of Channel catfish in reaches of interest. First trip, removal reach is 134 (A), last trip, removal reach is (B), first trip, control reach is (C), and last trip, control reach 135 is (D). (*) in B-D indicates size structure was smaller in removal reaches compared to 136 controls..………………………………………………………………………………………....……………………………17 137

138 Table 6. Mixed model beta estimates for the effects of removal on delta-CPUE from the start and 139

end of the experiment. Significant effects are highlighted in bold. The Upper and Lower 140 sections were analyzed separately due to unequal removal efforts……………………………….18 141

142 Table 7. Number of fish tagged (that were recaptured) by reach and proportion of fish recaptured 143

by reach in 2016. No movement is bordered black (gray filled), downstream movement is 144 red, upstream is green. “UP” refers to fish collected upstream, out of the study 145 area..………………………………………………………………………………………....………………………………….22 146

147 Table 8. Number of fish tagged (that were recaptured) by reach and proportion of fish recaptured 148

by reach in 2017. No movement is bordered black (gray filled), downstream movement is 149 red, upstream is green.………………………………………………………………………………………………….23 150

151 Table 9. Results from pairwise Dunn’s tests assessing for differences in movement rates of 152

juvenile Channel Catfish among years..………………………………………………………………………….25 153 154 Table 10. Results from pairwise Dunn’s tests assessing for differences in movement rates of adult 155

Channel Catfish among years. A (*) indicates significantly lower rates of movement…….25 156 157

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LIST OF FIGURES 161

Figure 1. Schematic describing geomorphic reaches by river mile and sampling locations of 162 treatment and control reaches. The plot also depicts where the two agencies were responsible 163 for nonnative fish removal (NMFWCO and UDWR)……………………………………………………………………..4 164

Figure 2. Spatial and temporal depiction of sampling and nonnative removal trips on the San 165 Juan River in 2016 (top panel) and 2017 (bottom panel). Discharge (cfs) at the USGS gauge at 166 Four Corners is colored in blue…………………………….……………………………………………………………………..6 167

Figure 3. Mean CPUE (Fish/hr) ± 1 S.E. of juvenile Channel Catfish (top row), adult Channel 168 Catfish (second row), Colorado Pikeminnow (third row), and Razorback Sucker (bottom row) 169 during each trip from the Upper Section of river, in removal (black symbols) and control (gray 170 symbols) reaches. Removal effort consisted of 18 passes in removal reaches. Each column 171 groups the removal and control reach in each geomorphic reach from up- to downstream (left 172 to right). The control reaches only have four samples because they were sampled twice during 173 spring and fall (i.e., one marking pass and one recapture pass)…………………………………………………..8 174

Figure 4. Mean CPUE (Fish/hr) ± 1 S.E. of juvenile Channel Catfish (top row), adult Channel 175 Catfish (second row), Colorado Pikeminnow (third row), and Razorback Sucker (bottom row) 176 during each trip from the Lower Section of river, in removal (black symbols) and control (gray 177 symbols) reaches. Each column groups the removal and control reach in each geomorphic reach 178 from up- to downstream (left to right). The control reaches only have two samples because they 179 were only sampled during the first and last pass of the year (i.e., one marking pass and one 180 recapture pass)…………………………………………………………………………………………………………………………..9 181

Figure 5. Results from Lincoln-Peterson population estimates (95% CI) for juvenile (top panel) 182 and adult (bottom panel) Channel Catfish between seasons and among reaches. The (*) denotes 183 a significant differences (95% CI) between seasons…………………………………………………………………12 184

Figure 6. Results from Lincoln-Peterson population estimates (95% CI) for Colorado Pikeminnow 185 (top panel) and Razorback Sucker (bottom panel between seasons and among 186 reaches………………………………………………………………..……………………………………………………………………13 187

Figure 7. Results from Lincoln-Peterson population estimates (95% CI) for all fish among all 188 reaches (combined treatment and control reaches) and seasons……………………………………………..14 189

Figure 8. Boxplots of sizes of Channel Catfish (TL) collected in each reach over different trips in 190 the Upper Section of river. Raw values were plotted rather than boxplots in cases where too few 191 individuals were collected (e.g., GeoReach 5, Removal reach, Trips 1 and 2). The high and low 192 outliers of each box denote the 95th and 5th percentiles, respectively…………………………………….15 193


Figure 9. Boxplots of sizes of Channel Catfish (TL) collected in each reach over different trips in 194 the Lower Section of river. The high and low outliers of each box denote the 95th and 5th 195 percentiles, respectively..…………………………………………………………………………………………………………15 196

Figure 10. Mean (1 S.E.) CPUE of each species in 2016 and 2017 in the upper section. The 197 horizontal dotted line in each plot denotes no change in CPUE between 198 seasons..……………………………………………………………………………………………………………………………………19 199

Figure 11. Mean (1 S.E.) CPUE of each species in 2016 and 2017 in the lower section. The 200 horizontal dotted line in each plot denotes no change in CPUE…………………………………………………20 201

Figure 12. Boxplots of movement rates (RM/Month) by tagging reach for all Channel Catfish 202 tagged and recaptured in 2016 (upper panel) and 2017 (lower panel). Each reached is coded by 203 geomorphic reach followed by treatment or control (3U and 3L refer to the Upper and Lower 204 sections, respectively). The upper and lower outliers of each box represent the 95th and 5th 205 percentiles.……………………………………………………………………………………………………………………………….26 206

Figure 13. Boxplots of movement rates (River Miles/Month) by year for juvenile Channel Catfish 207 (top panel) and adult Channel Catfish (bottom panel). The upper and lower outliers of each box 208 represent the 95th and 5th percentiles.……………………………………………………………………………………27 209

Figure 14. Exploitation rates for all life stages combined of Channel Catfish in the upper 210 treatment reaches by trip in 2016-2017. The right Y-axis is mean discharge for each 211 trip.…………………………………………………………………………………………………………………………………………..29 212

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INTRODUCTION_____________________________________________________________ 224

The introduction and establishment of nonnative fishes has been recognized as one of 225 several factors leading to the decline of native fish populations. The control of nonnative fishes 226 has become an increasingly important management action in programs aimed at the recovery of 227 federally protected species. The San Juan River is home to two federally endangered fishes, 228 Colorado Pikeminnow Ptychocheilus lucius and Razorback Sucker Xyrauchen texanus. The 229 establishment of Channel Catfish Ictalurus punctatus and Common Carp Cyprinus Carpio has 230 been identified as a detriment to the recovery of Colorado Pikeminnow and Razorback Sucker 231 (USFWS 2002a, b). Reducing the impacts of nonnative fishes has specifically been identified as a 232 management element in the San Juan River Basin Recovery Implementation Program’s Long 233 Range Plan (U.S. Fish and Wildlife Service 2014): 234

Element 3 - Management of Nonnative Aquatic Species 235

Goal 3.1 Control Problematic Nonnative Fishes. 236

Action 3.1.1 Develop, implement, and evaluate the most effective strategies for 237 reducing problematic nonnative fish. 238

Task 3.1.1.1 Mechanically remove nonnative fish to achieve objectives 239

Removal efforts by the New Mexico Fish and Wildlife Conservation Office (NMFWCO) 240 began on a limited basis in 1998 with intensified efforts beginning in 2001. These efforts focused 241 from PNM Weir to Hogback Diversion (River Mile (RM) 166.6 - 159.0). In addition to this section, 242 intensive nonnative removal from Hogback Diversion to Shiprock Bridge (RM 158.7 – 147.9) has 243 been conducted since 2003. Based on observed increases in Channel Catfish abundance, efforts 244 were expanded in 2008 to include intensive removal from Shiprock Bridge, New Mexico to 245 Mexican Hat, Utah (RM 147.9 – 52.9). Since the threat of nonnative fishes exists and there was 246 concern that Striped Bass Morone saxatilis and other Lake Powell fishes may colonize and 247 establish reproducing populations within the San Juan River (Gustaveson et al. 1984), the Utah 248 Division of Wildlife Resources (UDWR) initiated the mechanical removal of nonnative fishes in 249 the lower San Juan River from Mexican Hat, Utah to the Clay Hills Crossing (RM 2.9) beginning in 250 2002. 251

Since implementation of annual intensive nonnative fish removal in 2001, the structure 252 of the fish community in the San Juan River has changed substantially (Franssen et al. 2014a). 253 On an annual basis, Colorado Pikeminnow and Razorback Sucker densities (i.e., CPUE) have 254 increased over time, nonnative Common Carp densities have decreased, and Channel Catfish 255 densities have decreased, but only in upper reaches of the river (Franssen et al. 2014a, Franssen 256 et al. 2014b). However, the relative contribution of nonnative fish removal via electrofishing, 257 other management actions and environmental factors in driving these changes is unclear. For 258 example, establishing a causal linkage between nonnative fish removal or other management 259 actions (e.g., flow manipulation, habitat restoration) and changes in endangered fish densities is 260


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difficult due to the heavily augmented nature of these populations. Conversely, temporal 261 variation (or the lack of) in the densities of nonnative fishes following removal efforts are 262 potentially more directly related, but this variation is also not exempt from other environmental 263 factors (e.g., flow variation and reduced immigration). Given the spatial and temporal 264 inconsistencies of the current nonnative fish removal program as well as the multiple biotic and 265 abiotic factors contributing to temporal variation in densities of fishes, it is not surprising effects 266 of this management action have been difficult to elucidate. 267

Based on annual population estimates of Channel Catfish (Duran et al. 2015, Hines et al. 268 2015), it was apparent the level of nonnative fish removal effort previously put forth would 269 likely not suppress recruitment enough to induce system-wide population decline of this 270 species. Nonetheless, removing individual Channel Catfish from the river by definition lowers 271 their densities, which has the potential to directly impact endangered fishes through reduced 272 competition or predation as well as indirectly through deleterious effects of electrofishing on 273 native fishes. Yet, these potential direct (or indirect) effects of the San Juan River’s nonnative 274 fish removal program has been difficult to assess due to the complications mentioned above. 275

In a collaborative effort, nonnative fish removal efforts were redesigned in 2016 to 276 evaluate by what factor and for how long Channel Catfish densities are lowered and the 277 responses of native fish densities to electrofishing and nonnative fish removal. The experiment 278 was designed to assess the effects of nonnative fish removal on Channel Catfish and the two 279 endangered fishes over each year of effort. The river between Shiprock, New Mexico and 280 Mexican Hat, Utah was stratified by geomorphic reach to help control for natural longitudinal 281 variation in fish densities. Within each geomorphic reach, the river was further divided into 282 treatment and control reaches. Lengths of treatment and control sub-reaches within each 283 geomorphic reach were demarcated to maximize the sample size of collections used for 284 comparisons to increase statistical power. No electrofishing took place in control reaches 285 (except for the marking passes, and first recapture trip to generate population estimates). While 286 not electrofishing in control reaches and returning Channel Catfish to the river confounds effects 287 of electrofishing and removal of Channel Catfish in this study design, the exact mechanisms (i.e., 288 electrofishing or removing Channel Catfish) behind the potential effects observed are not 289 particularly important for guiding management actions at this time (i.e., we don’t have other 290 feasible mechanisms for removing large numbers of Channel Catfish at the scale proposed). 291 Moreover, we likely gained more insight into the effects of electrofishing on endangered fishes 292 by not electrofishing control reaches. The objectives of the study design are as follows: 293

1. Spatially demarcate removal and control reaches on the San Juan River in order to 294 statistically evaluate responses of fishes to nonnative fish removal via electrofishing. 295

2. Assess Channel Catfish CPUE and size distributions within removal reaches over time 296 using nonnative fish removal data. 297


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3. Compare Channel Catfish, Razorback Sucker, and Colorado Pikeminnow CPUE 298 between control and treatment reaches using sub-adult and adult fish community monitoring, 299 and nonnative fish removal data. 300

4. Compare Channel Catfish size distributions between control and removal reaches 301 using sub-adult and adult fish community monitoring, and nonnative fish removal data. 302

5. Quantify movement of tagged Channel Catfish among treatment and control reaches 303 over the summer. 304

On December 1, 2016, the SJRIP conducted a Nonnnative Fish Removal Workshop. 305 During this workshop, results from the 2016 removal efforts were presented and discussed 306 among participants from the Biology Committee and Peer Reviewers. As a result of these 307 discussions, the Biology Committee developed several options for nonnative removal in 2017 308 and a ranking system was developed to determine the preferred option. This ranking process 309 resulted in a recommendation by the Biology Committee to move forward with nonnative 310 removal in 2017. Key components to the preferred choice included focusing efforts prior to 311 spring runoff (based on 2016 results), conducting pre- and post-removal population estimates 312 for Channel Catfish, Razorback Sucker, and Colorado Pikeminnow; and continuing to have both 313 control and treatment reaches. 314

METHODS______________________________________________________________________ 315

Study Design 316

In both 2016 and 2017, the entire study area was contained between Shiprock, New 317 Mexico (RM 147.9) and Mexican Hat, Utah (RM 52.9). Within the study area, five different 318 sections were demarcated by geomorphic reach, and by the agencies responsible for conducting 319 sampling, and then further divided into either a control or treatment reach. This design allowed 320 for discrete and paired sections of river with presumably similar environmental conditions that 321 served as five separate longitudinal experimental units (Fig. 1). 322


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Figure 1. Schematic describing geomorphic reaches by river mile and sampling locations of 324 treatment (black squares) and control reaches (grey squares). The plot also depicts where the 325 two agencies were responsible for nonnative fish removal (NMFWCO and UDWR). 326

All nonnative fish removal efforts occurred between March and September before 327 annual sub-adult and adult fish community monitoring (i.e., fall monitoring) and efforts were 328 made to limit the amount of electrofishing during spawning periods of Colorado Pikeminnow. 329 Before removal of nonnative fishes was initiated, the initial densities of Channel Catfish, 330 Colorado Pikeminnow, and Razorback Sucker were indexed using electrofishing (i.e., Catch Per 331 Unit Effort Fish/Hr; CPUE in each RM) in the entire study area using two electrofishing rafts 332 during the first pass of the year. This first pass was also used to capture and mark (with floy 333 tags) individual Channel Catfish > 200 mm total length (TL) to quantify exploitation rates and 334 estimate population sizes, as well as quantify movement rates. After the initial marking pass in 335 2017, the first recapture pass served to estimate population sizes of Channel Catfish and the 336 endangered fishes in all the control and treatment reaches and to remove Channel Catfish in the 337 treatment reaches. Subsequent removal passes only occurred in treatment reaches. The 338 subsequent passes were used to recapture and remove Channel Catfish in three-river-mile 339 sampling units and to quantify size structure of Channel Catfish in each treatment reach (all fish 340 were measured from samples until at least 150 individuals are measured in each reach). All 341 endangered fishes were collected, measured and PIT tagged if untagged. Two different agencies 342 cooperatively contributed to nonnative fish removal. The NMFWCO conducted sampling in the 343 upper section from RM 147.9-93.6, and the UDWR sampled the lower section from RM 93.6-344 52.9 (Table 1). 345

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Table 1. The total number of removal passes by specific river miles from treatment and control 348 reaches, Geomorphic Reach (Georeach), Section of River, and agency responsible for removal 349 efforts. 350

Agency Section Georeach Treatment RMs Removal passes

NMFWCO Upper 5 Treatment 147-139 18

Control 138-131 1

4 Treatment 130-118 18

Control 117-106 1

3 Treatment 105-100 18

Control 99-93.6 1

UDWR Lower 3 Treatment 93.6-77 8

Control 76-68 1

2 Control 67-60 1

Treatment 59-52.9 8

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In 2017, the NMFWCO conducted a total of nine removal trips using four electrofishing 352 rafts per trip (i.e., 18 individual passes) from late March through late September (Fig. 2). The 353 lower section received less effort with UDWR conducting eight trips with two electrofishing rafts 354 per trip (8 individual passes). The NMFWCO completed five consecutive removal trips in the 355 upper section during the spring, resulting in 10 intensive removal passes in the treatment 356 reaches from March – April. Four consecutive removal trips were completed in the treatment 357 reaches during August, resulting in a total of 18 removal passes for the year in each treatment 358 reach in the upper section. The tenth removal trip of the year was changed in 2017 from a 359 removal pass to a marking pass to be able to generate post-removal population estimates using 360 annual fall monitoring as the recapture pass. This post-removal population estimate was 361 compared to the pre-removal population estimate to evaluate the effect of removal in each 362 section. Both sections then received a second marking pass in the fall. The final densities and 363 population estimates of Channel Catfish, Colorado Pikeminnow and Razorback Sucker were then 364 quantified from a final electrofishing sampling pass (i.e., fall monitoring) conducted by the U.S. 365 Fish and Wildlife Service’s Grand Junction Fish and Wildlife Conservation Office (GJFWCO) in late 366 September. Fish were sampled and CPUE was quantified in every RM during this final pass. 367


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Figure 2. Spatial and temporal depiction of sampling and nonnative removal trips on the San 371 Juan River in 2016 (top panel) and 2017 (bottom panel). Discharge (cfs) at the USGS gauge at 372 Four Corners is colored in blue. 373

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Results________________________________________________________________________ 376

Most of the following data are purposely presented with minimal summarization and 377 transformations so the reader may easily interpret raw data values. Sample sizes used in 378 summary statistics can be derived by the number of river miles sampled in each reach and pass. 379 However, it will be important to note that the sampling unit was one RM for the marking and fall 380 monitoring passes, while the sampling unit was three RMs during each removal pass. 381


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Without some penalty for multiple comparisons, the overall numbers of statistical tests 382 we conducted have likely inflated our Type I error rate (i.e., false positives). Because there are 383 several procedures to statistically account for multiple comparisons, and because it could be 384 argued these procedures may not be necessary in all cases, we present raw p-values from all 385 tests and the number of tests conducted so the reader can adjust significance levels if they see 386 fit. Accordingly, any statistical significance we discuss in the document will be made at the 387 unadjusted α=0.05 level. 388

Several age-classes of each species were collected during the experiment. Therefore we 389 grouped Channel Catfish into two age-classes: juveniles (as 200 – 299 mm Total Length [TL] 390 [ICTPUNJUV] and adults (300+ mm TL [ICTPUNADU]). Because the vast majority of Colorado 391 Pikeminnow collected were juveniles, we used one age class for all individuals (PTYLUC). Most 392 Razorback Suckers were adults, so we combined these individuals into one age class as well 393 (XYRTEX). 394

Statistical evaluation 395

The experiment focused on evaluating changes in CPUE and population abundances of 396 the three species as well as changes in the size structure of Channel Catfish over space and time 397 in control and treatment reaches. We also quantified movement of Channel Catfish in order to 398 understand how movement of fish may have impacted observed variation in CPUE, population 399 abundance, and size structure of this species. We first evaluated temporal variation of each 400 species’ CPUE within each treatment reach in the river’s upper and lower sections. Second, we 401 used population estimates to assess changes in population size among treatment and control 402 reaches. Third, we tested for temporal variation in size structure in removal reaches and tested 403 for differences in starting and ending sizes of fish in both control and treatment reaches. Forth, 404 we quantified changes in CPUE of each species between the start of the experiment and the end 405 of the experiment in each RM and tested for effects of removal in each paired reach. Finally, we 406 assessed longitudinal variability in movement of Channel Catfish in 2017 and compared annual 407 movement rates to rates observed in previous years. 408

Temporal variation in CPUE 409

1. Ho:Nonnative fish removal does not alter the CPUE of Channel Catfish over time. 410

We tested for temporal trends in the CPUE of each species (or age class) over time in 411 only removal reaches. To do so, we calculated the mean CPUE of each reach (using one RM as 412 the sample unit from the first and last pass, and three RMs for each removal pass) from each 413 trip (Fig. 3). 414

We tested for temporal variation in CPUE of each species using Spearman’s rank 415 nonparametric correlations using trip as the variable representing time. Sample sizes for each 416 test were n = 9 in reaches of the Lower Section and n = 12 the Upper Section. In the Upper 417 Section, most tests revealed significant temporal trends in CPUE (Table 2). The strongest trends 418


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were detected in both age classes of Channel Catfish in most reaches. Generally, CPUE of 419 Channel Catfish and Colorado Pikeminnow increased over time while Razorback Sucker CPUE 420 decreased in some reaches. Fewer temporal trends were detected in the Lower Section of river 421 where only juvenile Channel Catfish decreased over time in Reach 2 (Table 3). Significant 422 temporal patterns in CPUE were generally similar in 2016 and 2017. 423

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Figure 3. Mean CPUE (Fish/hr) ± 1 S.E. of juvenile Channel Catfish (top row), adult Channel 426 Catfish (second row), Colorado Pikeminnow (third row), and Razorback Sucker (bottom row) 427 during each trip from the Upper Section of river, in removal (black symbols) and control (gray 428 symbols) reaches. Removal effort consisted of 18 passes in removal reaches. Each column groups 429 the removal and control reach in each geomorphic reach from up- to downstream (left to right). 430 The control reaches only have four samples because they were sampled twice during spring and 431 fall (i.e., one marking pass and one recapture pass). 432

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Figure 4. Mean CPUE (Fish/hr) ± 1 S.E. of juvenile Channel Catfish (top row), adult Channel 435 Catfish (second row), Colorado Pikeminnow (third row), and Razorback Sucker (bottom row) 436 during each trip from the Lower Section of river, in removal (black symbols) and control (gray 437 symbols) reaches. Each column groups the removal and control reach in each geomorphic reach 438 from up- to downstream (left to right). The control reaches only have two samples because they 439 were only sampled during the first and last pass of the year (i.e., one marking pass and one 440 recapture pass). 441


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Table 2. Results from Spearman’s rank correlations testing for temporal variation in CPUE of 442 each species in each removal reach in the Upper Section of river in 2016 and 2017. Significant 443 correlations are denoted in bold font. 444

2016 2017

Reach Species r p r p

5 ICTPUNJUV 0.870 0.001 0.863 0.001

ICTPUNADU 0.590 0.046 0.902 0.001

PTYLUC 0.769 0.005 0.636 0.030

XYRTEX -0.608 0.040 -0.448 0.147

4 ICTPUNJUV 0.720 0.011 0.881 0.001

ICTPUNADU -0.839 0.001 0.510 0.094

PTYLUC 0.804 0.003 0.811 0.002

XYRTEX -0.413 0.184 -0.545 0.070

3 ICTPUNJUV 0.818 0.002 0.734 0.009

ICTPUNADU -0.741 0.008 0.049 0.886

PTYLUC 0.161 0.619 0.727 0.010

XYRTEX -0.657 0.024 -0.867 0.001

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Table 3. Results from Spearman’s rank correlations testing for temporal variation in CPUE of 453 each species in each removal reach in the Lower Section of river 2016 and 2017. Significant 454 correlations are denoted in bold font 455

2016 2017

Reach Species r p r p

3 ICTPUNJUV 0.261 0.470 0.633 0.076

ICTPUNADU -0.467 0.178 0.433 0.250

PTYLUC -0.648 0.049 0.433 0.250

XYRTEX -0.600 0.073 -0.483 0.194

2 ICTPUNJUV 0.152 0.682 -0.700 0.043

ICTPUNADU -0.539 0.113 -0.417 0.270

PTYLUC -0.552 0.104 -0.433 0.250

XYRTEX -0.600 0.073 -0.467 0.213

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Temporal variation in population estimates of Channel Catfish and Endangered Fishes 458

2. Ho:Nonnative fish removal does not change the estimates of population sizes in removal 459 reaches over time. 460

We used the first marking pass and the first removal pass to estimate reach-specific 461 population sizes in the spring and fall in 2017 (marking and recapture passes occurred in each 462 season). To quantify abundances of Channel Catfish and the endangered fishes we used Lincoln-463 Peterson mark recapture estimates with the Chapman correction. 464

Overall, reach-specific estimates were poor due to limited numbers of fish marked and 465 recaptured (Figures 5 & 6). The only differences found between spring and fall occurred with 466 adult Channel Catfish in Reach 5T where numbers of adult Channel Catfish increased between 467 seasons (Figure 5). No other differences were observed at the reach specific level. 468


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Figure 5. Results from Lincoln-Peterson population estimates (95% CI) for juvenile (top panel) 470 and adult (bottom panel) Channel Catfish between seasons and among reaches. The (*) denotes 471 a significant differences (95% CI) between seasons. 472

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Figure 6. Results from Lincoln-Peterson population estimates (95% CI) for Colorado Pikeminnow 475 (top panel) and Razorback Sucker (bottom panel between seasons and among reaches. 476

We then conducted population estimates at the entire treatment level (i.e., all 477 treatment reaches were combined and all control reaches were combined). Similar to reach-478 specific estimates, low recapture rates precluded low variation around estimates for all species 479 and reaches (Fig. 7.) 480

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Figure 7. Results from Lincoln-Peterson population estimates (95% CI) for all fish among all 484 reaches (combined treatment and control reaches) and seasons. 485

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Temporal variation in size structure of Channel Catfish 487

3. Ho:Nonnative fish removal does not alter the size structure of Channel Catfish over time. 488

We evaluated temporal trends in the size structure of Channel Catfish in removal 489 reaches. We first calculated the median size of Channel Catfish (above 200 mm TL) in each reach 490 during each pass in the Upper Section (Fig. 8) and the Lower Section (Fig.9). We then used 491 Spearman’s rank correlations to test for temporal trends of median sizes of Channel Catfish 492 using trip number as our measure of time. 493


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Figure 8. Boxplots of sizes of Channel Catfish (TL) collected in each reach over different trips in 495 the Upper Section of river. Raw values were plotted rather than boxplots in cases where too few 496 individuals were collected (e.g., GeoReach 5, Removal reach, Trips 1 and 2). The high and low 497 outliers of each box denote the 95th and 5th percentiles, respectively. 498

499

Figure 9. Boxplots of sizes of Channel Catfish (TL) collected in each reach over different trips in 500 the Lower Section of river. The high and low outliers of each box denote the 95th and 5th 501 percentiles, respectively. 502

Temporal trends in the size structure of Channel Catfish were evident in the Upper and 503 Lower Sections of river where all removal sections showed decreasing TL over time except for 504 lower Reach 3 (Table 4). 505

506

507

508

509

510


16

Table 4. Spearman’s rank correlation results testing temporal variation in median TL of Channel 511 Catfish among removal reaches in 2016 and 2017. 512

2016 2017

Section Reach Species r p r p

Upper 5 ICTPUN -0.914 0.001 -0.762 0.006

4 ICTPUN -0.972 0.001 -0.795 0.002

3 ICTPUN -0.895 0.001 -0.963 0.001

Lower 3 ICTPUN -0.511 0.132 -0.711 0.021

2 ICTPUN -0.176 0.632 0.232 0.520

513

Spatial variation in size structure of Channel Catfish 514

5. Ho:Nonnative fish removal does not alter the size structure of Channel Catfish in removal 515 reaches. 516

We then tested for differences in TL among the first and last passes in the removal and 517 control reaches using a nonparametric Kruskal-Wallis test in each reach. When the overall test 518 was significant, we followed it with Dunn’s posthoc comparisons of only the comparisons of 519 interest. We compared the first pass in each removal reach (denoted A) to the last pass in the 520 removal reach (denoted B), as well as the first pass in the control reach (denoted C) and last 521 pass in the control reach (denoted D). 522

When testing for differences in the size structure of Channel Catfish among groups in 523 each reach, all tests detected significant differences in the sizes of fish (Table 5). Generally, 524 differences in the size structure of Channel Catfish varied between trips in both the removal and 525 control reaches, and contrary to 2016, size of Channel Catfish in 2017 were significantly smaller 526 in 4 out of 5 removal reaches compared to their paired control reach (see “B-D” in Table 5). 527

528

529

530

531

532

533


17

534

Table 5. Results of Kruskal-Wallis nonparametric test results (and Dunn’s post hoc tests) for 535 differences in the TL of Channel catfish in reaches of interest. First trip, removal reach is (A), last 536 trip, removal reach is (B), first trip, control reach is (C), and last trip, control reach is (D). (*) in B-537 D indicates size structure was smaller in removal reaches compared to controls. 538

P

Year Section Reach Χ2 p

A-B A-C C-D B-D

2016 Upper 5 46.2 0.001

0.0001 0.4462 0.0001 0.3269

4 8.6 0.04

0.0658 0.0161 0.1482 0.3604

3 17.4 0.001

0.0069 0.0011 0.0404 0.3770

Lower 3 38.3 0.001

0.0001 0.0458 0.0010 0.3576

2 22.0 0.001

0.0227 0.0614 0.0001 0.2476

2017 Upper 5 28.2 0.001

0.0001 0.4670 0.0060 0.0130*

4 64.8 0.001

0.0001 0.0750 0.0001 0.0230*

3 14.7 0.001

0.0020 0.3510 0.0060 0.0862

Lower 3 18.5 0.001

0.0001 0.1060 0.3210 0.0260*

2 11.5 0.01 0.3420 0.0190 0.0170 0.0050*

539

Effects of removal on CPUE of fishes 540

4. Ho:Nonnative fish removal does not alter the CPUE of Channel Catfish in removal reaches 541 compared to control reaches (after controlling for initial CPUE). 542

& 543

6. Ho:Nonnative fish removal does not alter the CPUE of Colorado Pikeminnow and Razorback 544 Sucker Catfish in removal reaches. 545

To assess the effect of nonnative fish removal on Channel Catfish and the two 546 endangered fishes, we only used the catch rates from the first and last passes of the year to 547 quantify changes in fish densities between removal and control reaches (Fig. 8). To do so, we 548 quantified the change in CPUE between the first and last pass in each river mile (i.e., delta- 549 CPUE). We then used a mixed model predicting delta-CPUE using Treatment (Removal or 550


18

Control) as a fixed factor and Year and Geomorphic Reach (paired group of each Removal and 551 Control reaches, n = 5) as random factors. 552

Results from the mixed model revealed no discernable effects of removal on any fish/size class 553 except for XYRTEX with negative effects (Table 6). See Figures 10 & 11 for further details. 554

Table 6. Mixed model beta estimates for the effects of removal on delta-CPUE from the start and 555 end of the experiment. Significant effects are highlighted in bold. The Upper and Lower sections 556 were analyzed separately due to unequal removal efforts. 557

Section Species Removal Estimate SE

Random Effects

Upper ICTPUNJUV 0.07 0.67 Year & Reach

ICTPUNADU 2.14 1.72 Year & Reach

PTYLUC 0.19 0.53 Year & Reach

XYRTEX -2.27 1.05 Year & Reach

Lower ICTPUNJUV -1.45 2.51 Year & Reach

ICTPUNADU 3.85 4.09 Year & Reach

PTYLUC 0.46 0.45 Year & Reach

XYRTEX 0.10 0.68 Year & Reach


19

558

Figure 10. Mean (1 S.E.) CPUE of each species in 2016 and 2017 in the upper section. The horizontal 559 dotted line in each plot denotes no change in CPUE between seasons. 560

561

562

563


20

564

Figure 11. Mean (1 S.E.) CPUE of each species in 2016 and 2017 in the lower section. The horizontal 565 dotted line in each plot denotes no change in CPUE. 566

567

568

569

570

571

572

573


21

Channel Catfish movement 574

7. Ho:Channel Catfish do not move among reaches. 575

We assessed movement of individually floy-tagged Channel Catfish and endangered fishes 576 recaptured in 2016 and 2017; Tables 7 & 8). Movement rate was quantified for fish by calculating the 577 distance (negative distances indicated downstream movement) and time between captures. Initial 578 investigations of the data indicated fish demonstrated consistent, downstream movements immediately 579 after tagging (up to ten days), therefore we limited the data set to fish recaptured >10 days after 580 tagging. 581

We assessed variation in movement rates of fish spatially among all reaches based on where 582 they were initially tagged in 2016 and 2017. Channel Catfish movement rates in 2016 were generally 583 leptokurtic and upstream skewed, but movement rates in 2017 were less directional (Tables 8 & 9, 584 Figure 12). 585

586

587

588

589

590

591

592

593

594

595

596

597

598

599

600


22

Table 7. Number of fish tagged (that were recaptured) by reach and proportion of fish recaptured by 601 reach in 2016. No movement is bordered black (gray filled), downstream movement is red, upstream is 602 green. “UP” refers to fish collected upstream, out of the study area. 603

Recaptured Reach

SPECIES Tag Reach Tagged 2T 2C 3LC 3LT 3UC 3UT 4C 4T 5C 5T UP

ICTPUN 5T 3

1.00

5C 18

0.06 0.39 0.50 0.06

4T 75 0.01

0.85

0.13

4C 27

0.81 0.07 0.11

3UT 15

0.60

0.33

0.07

3UC 20

0.05 0.50

0.30 0.05 0.10

3LT 11

0.27

0.09

0.64

3LC 6

0.17 0.17

0.67

2C 11

0.27

0.18

0.27

0.27

2T 14 0.43

0.07 0.07

0.21

0.14

0.07

PTYLUC 5T 11

0.27

0.73

5C 0

4T 12

0.08 0.08 0.58

0.25

4C 0

3UT 3

0.67

0.33

3UC 0

3LT 17

0.59

0.06

0.24

0.12

3LC 2

0.50

0.50

2C 3

0.67

0.33


23

2T 8 0.75

0.13

0.13

XYRTEX 5T 129

0.01 0.01 0.02 0.02 0.91 0.03

5C 10

0.50 0.40 0.10

4T 161 0.01

0.01 0.02 0.02 0.92

0.02 0.01

4C 5

0.60 0.20 0.20

3UT 37

0.05

0.78 0.03 0.11 0.03

3UC 7

0.57 0.29 0.14

3LT 33

0.06 0.85

0.09

3LC 2 0.50

0.50

2C 1

1.00

2T 4 0.50 0.25 0.25

604

605

606

607

608

609

610

611

612

613

614

615

616


24

Table 8. Number of fish tagged (that were recaptured) by reach and proportion of fish recaptured by 617 reach in 2017. No movement is bordered black (gray filled), downstream movement is red, upstream is 618 green. 619

Recaptured Reach

SPECIES Tagged Reach Tagged 2C 2T 3LC 3LT 3UC 3UT 4C 4T 5C 5T

ICTPUN 5T 5 0.20 0.80

5C 2

0.50

0.50

4T 16

0.06

0.19 0.75

4C 17

0.35 0.18 0.29

0.18

3UT 7

0.86

0.14

3UC 4

0.25 0.75

3LT 30

0.03 0.03 0.63 0.10 0.03

0.13

0.03

3LC 13

0.31 0.54

0.08 0.08

2T 18 0.11 0.78

0.06

0.06

2C 24 0.50 0.04 0.04 0.04

0.04

0.25

0.08

PTYLUC 5T 17 0.06 0.12 0.82

5C 3

0.33 0.67

4T 20

0.05

0.05 0.80 0.10

4C 3

0.67 0.33

3UT 6

0.50 0.50

3UC 1

1.00

3LT 21

0.05 0.76

0.05

0.14

3LC 3

1.00

2T 5

0.60

0.20

0.20


25

2C 6 0.67

0.17

0.17

XYRTEX 5T 79 0.01 0.01 0.01 0.11 0.10 0.75

5C 21

0.24 0.62 0.14

4T 89

0.09 0.79 0.07 0.06

4C 29

0.07

0.21 0.66

0.03 0.03

3UT 29

0.03 0.03 0.28 0.45 0.10 0.07 0.03

3UC 12

0.42 0.50 0.08

3LT 64

0.08 0.88 0.02 0.02

0.02

3LC 18 0.22

0.67 0.06

0.06

2T 10 0.10 0.90

2C 8 0.63 0.25 0.13

620

To quantify the relative movement rates of Channel Catfish in 2016 and 2017 to four previous 621 years, we conducted nonparametric Kruskal-Wallis tests by year for both juvenile and adult Channel 622 Catfish and then conducted post hoc analyses using Dunn’s test. Kruskal-Wallis tests revealed significant 623 differences in movement rates among years for both juvenile (Χ2 = 33.5, p


26

630

Table 10. Results from pairwise Dunn’s tests assessing for differences in movement rates of adult 631 Channel Catfish among years. A (*) indicates significantly lower rates of movement. 632

Year 2011 2012 2013 2014 2016

2012 0.209

2013 0.085 0.248

2014 0.001 0.002 0.042

2016 0.001 0.001 0.001 0.004

2017 0.033 0.095 0.233 0.307 0.013*

633

634

635

636

637

638

639

640

641


27

642

643

Figure 12. Boxplots of movement rates (RM/Month) by tagging reach for all Channel Catfish tagged and 644 recaptured in 2016 (upper panel) and 2017 (lower panel). Each reached is coded by geomorphic reach 645 followed by treatment or control (3U and 3L refer to the Upper and Lower sections, respectively). The 646 upper and lower outliers of each box represent the 95th and 5th percentiles. 647

648

2016

2017


28

649

Figure 13. Boxplots of movement rates (River Miles/Month) by year for juvenile Channel Catfish (top 650 panel) and adult Channel Catfish (bottom panel). The upper and lower outliers of each box represent the 651 95th and 5th percentiles. 652

One tool used to measure the efficacy of nonnative fish removal on the San Juan River was the 653 calculation of exploitation rates from mark/recapture data. Exploitation rates, u, were estimated as the 654 proportion of recaptured marked fish to marked fish, u = R/M, where, R represents number of 655 recaptured fish and M represents number of marked fish. Exploitation rates for juvenile and adult 656 Channel Catfish in 2016 and 2017 include only fish that were tagged in treatment reaches and 657 subsequently recaptured in a treatment reach. Fish that were tagged in control reaches and recaptured 658 in treatment reaches were not included in the 2016-2017 exploitation rates. 659


29

Exploitation Rates 660

The tagging trip in 2017 took place March 13 -17. This was one week earlier than the tagging 661 trip in 2016, and was the earliest trip of the year under the new study design. A total of 243 Channel 662 Catfish were tagged in the upper section, control and treatment reaches combined, during 2017. The 663 number of fish tagged in 2017 represented a 31.2 % reduction when compared to 2016 in this section. In 664 the upper section, there were only 94 Channel Catfish (14 juveniles) tagged in the treatment reaches in 665 2017 compared to 301 (seven juveniles) tagged in treatment reaches during 2016. Numbers of Channel 666 Catfish tagged in the lower treatment reaches was similar among years with 307 fish tagged in 667 treatment reaches in 2016 and 351 fish tagged in treatment reaches in 2017. 668

Upper treatment reaches exploitation rates in 2017 for juvenile Channel Catfish were 14.3% and 669 18.8% for adults, compared with 11% for juvenile Channel Catfish and 9% for adult Channel Catfish in 670 the lower treatment reaches. Exploitation rates for all size classes of Channel Catfish in the upper 671 reaches were lower in 2017 compared to rates observed in 2016. Upper treatment reaches exploitation 672 rates in 2016 for juvenile Channel Catfish were 57.1% and 48.8% for adults, compared with 15% for 673 juvenile Channel Catfish and 20% for adult Channel Catfish in the lower treatment reaches. 674

The majority of 2016 upper section recaptures occurred during trips 1-6, prior to spring runoff. 675 Only eight fish were recaptured after the spring flow release, trips 7-10. This result prompted the 676 recommendation to focus the majority of the 2017 effort in the spring, prior to runoff. We had planned 677 to conduct eight removal trips in the spring 2017. Early spring runoff out of the Animas River led to 678 higher than expected flows in 2017 and these flows could have resulted in the lower exploitation rates 679 observed in 2017. In 2016, all upper section spring trips were conducted when the river discharge was < 680 1,500 CFS. In 2017, there were no spring trips during flows less than 1,500 CFS and trips 6-8 had to be 681 postponed to the fall due to flows exceeding 3,000 CFS (Figure 14). These unfavorable sampling 682 conditions could have also contributed to the lower exploitation rates and poor population estimates 683 observed 2017 as a result of limited numbers of fish being marked and recaptured. 684


30

685

Figure 14. Exploitation rates for all life stages combined of Channel Catfish in the upper treatment 686 reaches by trip in 2016-2017. The right Y-axis is mean discharge for each trip. 687

Rare Fish Captures 688

In addition to nonnative fishes, NMFWCO and UDWR collected data on any rare fishes 689 encountered during removal efforts. In 2016, nonnative fish removal crews sampling in the upper 690 removal reaches collected a total of 320 Colorado Pikeminnow and 1,423 Razorback Sucker. Crews 691 sampling the lower reaches in 2016 collected 218 Colorado Pikeminnow and 264 Razorback Sucker. Of 692 these fish, 32 individual adult Colorado Pikeminnow >450 mm TL were collected. In 2017, a total of 852 693 Colorado Pikeminnow and 1,691 Razorback Sucker were collected in the upper section and 342 Colorado 694 Pikeminnow and 590 Razorback Sucker were collected in the lower section. Of these fish, 36 Colorado 695 Pikeminnow >450 mm total length were collected. These data document the increasing numbers of 696 endangered fish, particularly adult Colorado Pikeminnow, inhabiting the San Juan River and the strides 697 the SJRBRIP is making towards recovery. 698

699

700

701

702


31

Discussion____________________________________________________________________________ 703

The San Juan River’s nonnative fish control program was modified in 2016-2017 to facilitate 704 quantification of the effects of nonnative removal on native and nonnative fishes. This modification was 705 designed to assess yearly effects of nonnative fish removal on Channel Catfish and the two endangered 706 fishes, Razorback Sucker and Colorado Pikeminnow. While analyses of this modification showed 707 significant temporal trends in CPUE of Channel Catfish and a significant temporal trend in the size 708 structure of Channel Catfish, the modification did not reveal a significant positive response of 709 endangered fishes to nonnative removal and it did not significantly alter the CPUE of Channel Catfish in 710 removal reaches compared to control reaches. Effects of this modified management action have been 711 difficult to quantify and to understand. Many environmental factors could have contributed to the 712 variation observed among removal passes and between years such as flow, turbidity, and other 713 environmental variations that are difficult to tease apart. Common Carp catch rates have drastically 714 declined riverwide since the initiation of intensive nonnative removal and Common Carp collections 715 continue to be infrequent riverwide. Since increasing effort in 2008, Channel Catfish abundance has 716 fluctuated, but no noticeable, riverwide declines have been observed in this section; however, 717 noticeable declines in Channel Catfish abundance have been observed in the smaller, more discrete 718 reaches of the upper San Juan River. These smaller reaches have also received the most amount of 719 effort (i.e., electrofishing hours per river mile). 720

After the sampling period in 2017, the San Juan River Basin Recovery Implementation Program 721 convened another nonnative fish workshop to discuss results from the modified management during 722 2016-2017 and to plot a course for future nonnative fish management efforts on the San Juan River. 723 Several options were presented and ultimately agreement among the Biology Committee for one option 724 was realized. It was determined that work in 2018 and 2019 would support efforts towards a diet study 725 being conducted by Kansas State University, SOW 18-26 Incidence and consumption of endangered 726 fishes by Channel Catfish (Ictalurus punctatus) in the San Juan River, to quantify the predatory effects 727 Channel Catfish have on the two endangered fishes. Additionally, it was determined that a mark-728 recapture study would be initiated for Channel Catfish to generate more precise population estimates, 729 detection probabilities, and annual survival rates. Data from both stomach contents analysis (i.e., 730 percent predation) and abundance/survival estimates (number of predatory fish), when used in concert, 731 will aid the SJRBRIP in the development of a future nonnative fish management program that will be 732 commensurate with the level of threat. 733

734

735

736

737

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Literature Cited 739

Duran, B.R. 2015. Endangered fish monitoring and nonnative species monitoring and control in the 740 upper/middle San Juan River: 2014. Final report to the San Juan River Basin Recovery Implementation 741 Program. Albuquerque, NM. 742

Franssen, N.R., S.L. Durst, K.B. Gido, D.W. Ryden, V. Lamarra, and D.L. Propst. 2014a. Long-term 743 dynamics of large-bodied fishes assessed from spatially intensive monitoring of a managed desert 744 river. River Research and Applications doi: 10.1002/rra.2855 745

Franssen, N.R., J.E. Davis, D. Ryden and K.B. Gido. 2014b. Fish community responses to mechanical 746 removal of nonnative fishes in a large southwestern river. Fisheries 39:352–363. 747

Gustaveson, W. A., T. D. Pettingill, J. E. Johnson, and J. R. Wahl. 1984. Evidence of in-reservoir spawning 748 of striped bass in Lake Powell, Utah-Arizona. North American Journal of Fish Management 4: 540-546. 749

Hines, B. 2015. Endangered fish monitoring and nonnative fish control in the lower San Juan River 2014. 750 Final report to the San Juan River Basin Recovery Implementation Program. Albuquerque, NM. 751

San Juan River Basin Recovery Implementation Program. 2014. Long Range Plan. U.S. Fish and Wildlife 752 Service, Albuquerque, NM. 753

U.S. Fish and Wildlife Service. 2002a. Colorado Pikeminnow (Ptychocheilus lucius) Recovery Goals: 754 amendment and supplement to the Colorado Squawfish Recovery Plan. U.S. Fish and Wildlife Service, 755 Mountain-Prairie Region (6), Denver, Colorado. 756

U.S. Fish and Wildlife Service. 2002b. Razorback Sucker Xyrauchen texanus Recovery Goals: amendment 757 and supplement to the Razorback Sucker Recovery Plan. U.S. Fish and Wildlife Service, Mountain-Prairie 758 Region (6), Denver, Colorado 759

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AN EXPERIMENTAL A N PECIES MONITORING AND C S UAN …...129 . 130 Table 4. Spearman’s rank correlation results testing temporal variation in median TL of Channel ... 144 by reach