Survival of razorback sucker stocked into the lower Colorado River

Survival of razorback sucker stocked into the lower Colorado River Trip Report 20: Palo Verde and Cibola Divisions 1-10 March 2005 Prepared by Darren J. Thornbrugh, Jason D. Schooley, and Brian R. Kesner Submitted by Paul C. Marsh Arizona State University Tempe, Arizona 85287-4501 In behalf of Agreement Number 04FG300034 between Arizona State University and U.S. Bureau of Reclamation Boulder City, Nevada 89006 May 27, 2005

Summary Portions of Palo Verde and Cibola divisions of the Colorado River were surveyed 1-10 March 2005 for presence of razorback sucker Xyrauchen texanus. The study area included portions of the main channel near Interstate 10 bridge, A-7 backwater upper and lower sections, A-10 backwater upper and lower sections, and Sandy Cove (Hippie Hole), all in La Paz County Arizona. Methods were boat electrofishing and trammel netting resulting in contact with a total of 1,865 fish representing at least 16 species. One hundred thirty-two individual razorback suckers accounted for 150 capture records. Sex ratio was 85 juvenile, 18 female, 26 male, and 3 unknown. Mean total length was 35 cm (range 29 to 54 cm) and mean weight was 543 g. Twenty-one of these fish contained PIT tags and we implanted PIT tags in the remaining 111 fish. Three radio tagged razorback suckers were captured, one of which was captured twice. These fish were from a parallel project evaluating post-stocking dispersal. All fish were released near site of capture, less one mortality. Sampling for larvae was conducted at three locations within the study area and a total of 40 razorback sucker larvae were collected. Twenty and fifteen larvae respectively were collected and preserved from Sandy Cove (Hippie Hole) and the upper section of A-10 backwater. A single census, mark-recapture population estimate (Chapman modified Petersen method) of N* = 315 (95% CI 115-788) was calculated for A-7 backwater. The same computational method was used to back-calculate an estimate of N* = 557 (95% CI 311-917) fish stocked into A-10 backwater; a result that compares favorably with the actual number of 689 fish stocked. Introduction Razorback suckers have been repatriated to the lower Colorado River for more than 25 years, but stocking has recently been accelerated to meet requirements of a US Fish and Wildlife Service Biological Opinion of lower river operations (USFWS 1997). Moreover, monitoring of these fish has been largely sporadic and incidental to sport-fish related activities. The purpose of this work is to attempt to assess survival of stocked fish by performing an intensive, opportunistic survey that targets razorback sucker in approximately 282 km of river from Parker Dam downstream to Yuma. The intention is to collect multiple samples from the main channel and all watercraft-accessible backwaters and side channels to assess post-stocking survival, distribution, and abundance of the target species. Population abundance of razorback sucker is Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 2

estimated quantitatively using mark-recapture methods when adequate data are available. Study Area The study area consisted of portions of the main channel in vicinity of the Interstate 10 bridge across the Colorado River at River Mile (RM 1 ) 121, A-7 backwater upper and lower sections, A-10 backwater upper and lower sections, and Sandy Cove (Hippie Hole), all in La Paz County, Arizona (Figs. 1-4). Surveys were conducted on US Bureau of Reclamation (USBR) Palo Verde and Cibola divisions between RM 121 and 99. Methods Primary sampling methods were boat electrofishing and trammel netting. Electrofishing (Smith-Root GPP 7.0) was conducted during evening and nighttime. Before electrofishing, we measured surface water temperature, electrical conductivity, and total dissolved solids (TDS). Field strength was not electronically measured. Trammel nets (46 x 1.8 m x 3.8 cm mesh) were set in the evening, fished overnight, and retrieved the following day. Net set locations were chosen based on water depth (ideally >1.5 m) and habitat (proximal to cover but free of submerged obstacles or debris). Nets were generally set in backwaters and eddies off main channel. Sets were intentionally placed in remote, slightly inaccessible locations. Nominal time for setting nets was at sunset and removal was over a range of times depending on catch. All fish were identified to species when possible and counted by life stage (age-0 [youngof-year plus small bodied species such as red shiner, mosquitofish, and mollies] and age-1+ [adult]) and method of capture. When applicable, native fish were individually measured (total length [TL], in cm), scanned for wire tag or passive integrated transponder (PIT) tag, sexed (male, female, juvenile, and unknown [for fish 40 cm for which gender could not be reliably determined]), and examined for general health and condition. A PIT tag was implanted into the abdominal cavity of natives if none was present, and all fish were released near the site of capture. Voucher specimens up to a total of 10 individuals per non-native species 2 were fixed in 10% formaldehyde, rinsed in fresh water, preserved in 70% ethanol, and deposited into the ASU Collection of Fishes. 1 River miles are measured upstream from the Southerly International Boundary near San Luis, Arizona. 2 This represents the total number of vouchers for the entire study period. Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 3

Exceptional individuals and others exhibiting key characteristics or other features were photographed to provide a permanent record. Nighttime larval sampling was conducted in three backwaters: Sandy Cove, A-10, and A- 7 (Figs. 2-4). Twenty to forty minutes was spent collecting larvae at each site. Brinkmann Q-Beam Starfire II fishing lights were hung over the side of the boat and submerged in the water. Larval fishes were attracted to the lights, captured by finemesh aquarium dip net, and preserved in either 10% formaldehyde or 70% ethanol. Larval fish were returned to the laboratory and identified to species using a computerinteractive key (Snyder et al. 2005). Stocked razorback sucker were collected from A-7 backwater in both January and March 2005, and mark-recapture data from these samples were used to calculate a single census modified Petersen population estimate (Ricker 1975) for that site. The computational formula (Chapman adjustment) for population estimation is N* = (C+1)(M+1)/(R+1) where M = number of fish captured, marked, and returned to the population from an initial sample, C = total number of fish captured in a second sample, and R = number of fish in the second sample that were marked in the first sample. Confidence intervals (CI) were determined using tables from Appendix II in Ricker (1975) with R as the entering variable. The same methods were used with stocking data for February and survey data for March to back-calculate a population estimate for comparison with the known number of stocked fish into A-10 backwater on February 4, 2005. This last exercise was done to validate assumptions of the method and thus ensure that population estimates for lower Colorado River backwaters are unbiased. Results and Discussion Electrofishing and netting combined yielded a total of 1,865 fish representing at least 16 species (Table 1). Largemouth bass Micropterus salmoides accounted for about 26% of the total catch and was the most abundant variety overall, followed by common carp Cyprinus carpio (22%), bluegill sunfish Lepomis macrochirus (21%), razorback sucker Xyrauchen texanus (8%), Lepomis sp. (juvenile sunfishes that could not reliably be assigned to species, 7%), channel catfish Ictalurus punctatus (5%), and redear sunfish Lepomis microlophus (3%). Other species each contributed less than 3% to total catch. Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 4

One hundred thirty-two individual razorback suckers accounted for 150 razorback sucker captures: 112 by trammel netting and 38 by electrofishing. One hundred fifteen fish were captured in the upper section of A-10 backwater and two were taken in the lower section. Twenty-five fish were captured in the upper section of A-7 backwater and 8 in the lower section. No razorback suckers were captured in the main channel or Sandy Cove. Sex determinations were 85 juvenile, 18 female, 26 male, and 3 unknown. Twenty-five of the fish were ripe including 19 males and 6 females. Mean TL was 35.4 cm (range 28.5 to 54.0 cm) and mean weight was 543 g. Wire tags were detected in the left-dorsal musculature of 24 fish, caudal peduncle 3 (CP) of 102 fish, and none was detected in the remaining 6 fish. Twenty-one fish contained PIT tags and we implanted PIT tags in the remaining 111 fish. Sampling resulted in one mortality. All fish were released near site of capture. Seventeen of the razorback suckers we captured had been PIT tagged at Arizona Game and Fish Department Bubbling Ponds State Fish Hatchery and released 4 November or 2 February 2005 (Table 2). Four fish released in November showed nearly identical growth rates (0.5 mm/day) except for one of the fish who s growth rate was about half that of the others. The 13 fish released in February had varying growth rates ranging from nil to 0.33 mm/day, but growth overall was relatively slow because of cold winter temperatures. Four razorbacks that we captured had been PIT tagged by ASU previously during this study. Two of these were recaptured in the same backwater in which they were marked. One razorback was marked in C-7 and moved upstream five miles where it was encountered in A-7 (Fig. 2) 49 days later. Another fish was marked in Oxbow Recreational Area (Fig. 4) at RM 100 and recaptured approximately ten months later 19 miles upstream in A-7 (Fig. 2). Growth rates were variable in these four fish. Electrofishing: A total of 16,564 sec real time (276 min) of boat electrofishing resulted in contact with 1,150 fish representing at least 15 species (Table 1). Catch rate was 69 fish per 1000 sec. Largemouth bass were most abundant (37%), followed by common 3 All razorback suckers stocked into the lower Colorado River are marked with a wire tag. With few exceptions, wire tags were inserted into the left dorsal musculature. After February 4, 2005, fish stocked into A-10 backwater were wire tagged in the right caudal peduncle; however, left vs. right CP cannot be reliably determined for smaller fish. Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 5

carp (17%), bluegill sunfish (17%), Lepomis sp. (juvenile sunfishes that could not reliably be assigned to species, 12%), threadfin shad (5%), razorback sucker (3%), channel catfish (3%), redear sunfish (2%), and striped bass (2%). Other species each comprised 1% or less of the electrofishing catch. The electrical field was observed effective to a maximum depth of about 1.5 m. Water was 1.4-4.3 cooler and conductivity and TDS were 12-40% lower in the main channel compared with backwater (Table 4); these results were unremarkable. Trammel Netting: A total of 43 overnight trammel net sets resulted in contact with 715 fish representing at least 12 species (Table 1). Catch averaged 17 fish per net and ranged from 1 to 40. Common carp was the most abundant species (29%), followed by bluegill sunfish (27%), razorback suckers (16%), channel catfish (9%), largemouth bass (8%), and redear sunfish (5%). Other species each comprised 2% or less of the total trammel net catch. Average trammel netting depth was about 2 m. Nets were retrieved after sunrise and the average set time was about 14 hrs. Comparative Total Fish Catch in Study Area: We have encountered 106 individual razorback suckers with mean TL of 41.2 cm since January 2003 in the upper section of A-7 backwater (1,595 total fish captured in 381 min of electrofishing; 982 fish captured in 48 trammel nets). There have been 23 individual razorback sucker captures (44.4 cm mean TL) in the lower section of A-7 backwater (151 total fish captured in 50 min of electrofishing; 191 fish captured in 16 trammel nets). In the upper section of A-10 backwater there were 100 individual razorback sucker captures (33.5 cm mean TL) among 552 total fish captured in 123 min of electrofishing and 318 fish captured in 18 trammel nets. Efforts in the lower section of A-10 backwater yielded 5 individual razorback suckers (43.4 cm mean TL) among 1,163 fish captured in 180 min of electrofishing plus 391 fish captured in 27 trammel nets. Eight individual razorback suckers (39.1 cm mean TL) were among 367 total fish captured in 39 min of electrofishing and 173 fish captured in 8 trammel nets in Sandy Cove. And last, efforts in the main channel produced no razorback suckers among 269 fish captured in 126 min of electrofishing and 62 fish captured in 11 trammel nets. Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 6

Razorback Sucker Larvae Sampling and Laboratory Identification: A total of 40 larval fish were collected from two sites: 25 from Sandy Cove and 15 from A-10 backwater upper section near the top of the middle culvert; none was taken from A-7 backwater, which was sampled in the upper section near the boat ramp. All specimens were confirmed as larval razorback sucker using keys in Snyder et al. (2005). Single Census (modified Petersen) Population Estimate for A-7 Backwater: Successive collections were made in A-7 Backwater in January and March 2005. In January 44 fish were marked (M) with PIT tags and released back into A-7. In March, 20 fish were captured (C) and 2 of these fish were recaptures (R) from the January sampling event. The population estimate for January 2005 was N* = 315 with 95% CI of 115-788 and 99% CI of 92-859. The small number of recaptures in March means it is likely that the estimate is biased. Preferably, we would like to have four or more recaptures in the second collection to reduce the likelihood of a biased estimate. Regardless, our estimate has significant implications in respect to post-stocking fate of released fish. A total 4,657 fish (including 811 that were PIT tagged) were released to A-7 Backwater in November and December 2004. However, our population estimate in January 2005 was only 315. Thus, stocked fish either dispersed rapidly from the release location, or their mortality rate was high and the fish were no longer in the system to be collected. An additional 689 (including 69 PIT tagged) fish were released in February 2005, and we captured only one PIT tagged fish from this batch, further indicating rapid post-stocking dispersal or mortality. Single Census (modified Petersen) Population Estimate for A-10 Backwater: Using mark-recapture data from a stocking event in February and a survey event in March we performed a population estimation to back-calculate a known number of stocked fish. In this case, 689 fish (70 PIT tagged and RCP wire-tags, 619 marked only with RCP wire-tags) were released in A-10 Backwater on 4 February 2005. A survey was performed in March 2005. Values of 70 (M), 101 (C) and 12 (R), resulted in a backcalculated population estimate for January 2005 of N* = 557 with 95% CI of 311-917 and 99% CI of 274-1114. Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 7

While the estimate of 557 is lower than the actual number stocked (689), the estimate falls within the 95% CI, which suggests the estimate is unbiased. The low estimate most likely was due to chance because it is unlikely that the actual proportion of marked to unmarked fish in the population was perfectly reflected in our March survey. It is unknown whether the capture in A-7 backwater of four RCP wire-tagged fish was an error in the tagging process (i.e., A-7 fish erroneously tagged with A-10 wire-tag locations), or an actual dispersal from A-10 upstream to A-7. Our ability to make single census population estimates means that we are one step closer to being able to monitor emigration and mortality out of A-10. Problems and Solutions Sampling was performed only in Arizona backwaters and main channel because our California Department of Fish and Game scientific collection permit renewal was sill in process. That permit now is in-hand and collections in California waters will resume this autumn. Literature Cited Ricker, W.E. 1975. Computation and Interpretation of Biological Statistics of Fish Population. Bulletin 191. Fisheries Research Board of Canada, Ottawa. 382 pages. Snyder, D.E., K.R. Bestgen, S.C. Seal and C.L. Bjork. 2005. Guide and computer interactive keys to native cypriniform fish larvae of the Gila River basin. Final Report, U.S. Bureau of Reclamation, Phoenix AZ. Larval Fish Lab, Colorado State University, Fort Collins. USFWS. 1997. Final Biological and Conference Opinion on lower Colorado River operations and maintenance - Lake Mead to Southerly International boundary. U.S. Fish and Wildlife Service, Albuquerque NM. 196 pages. Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 8

Figure 1. Study area backwaters, lower Colorado River, Palo Verde Division, 1-10 March 2005. Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 9

Figure 2. Study area backwaters, lower Colorado River, Palo Verde Division, 1-10 March 2005. Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 10

Figure 3. Study area backwaters, lower Colorado River, Palo Verde Division, 1-10 March 2005. Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 11

Figure 4. Study area backwaters, lower Colorado River, Cibola Division, 1-10 March 2005. Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 12

Table 1. Numbers of fish by age (size) class captured by trammel netting and electrofishing, total number caught, and proportion of total catch. USBR Palo Verde and Cibola divisions, lower Colorado River. 1-10 March 2005. Species Common Name Age # Netted # Shocked Total % of Catch Carassius auratus 1 0 3 3 < 1% Goldfish Cyprinella lutrensis 0 0 1 1 < 1% Red Shiner Cyprinus carpio 1 206 200 406 21.8% Common Carp Dorosoma petenense 1 0 55 55 2.9% Threadfin Shad Ictalurus punctatus 1 63 32 95 5.1% Channel Catfish Lepomis gulosus 1 3 6 9 < 1% Warmouth Lepomis macrochirus 1 190 198 388 20.8% Bluegill Sunfish Lepomis microlophus 1 37 24 61 3.3% Redear Sunfish Lepomis sp. 0 1 134 135 7.2% Juvenile Sunfishes 0 0 1 1 < 1% Micropterus dolomieu Smallmouth Bass 1 12 10 22 1.2% 0 0 145 145 7.8% Micropterus salmoides Largemouth Bass 1 54 278 332 17.8% 0 0 20 20 1.1% Morone saxatilis Striped Bass 1 6 0 6 < 1% Poecilia latipinna 1 0 1 1 < 1% Sailfin Molly Pomoxis 1 4 0 4 0.2% nigromaculatis Black Crappie 0 0 2 2 < 1% Pylodictis olivaris Flathead Catfish 1 15 1 16 < 1% Family Cichlidae 1 12 1 13 < 1% Tilapiine fishes Xyrauchen texanus 1 112 38 150 8.0% Razorback Sucker Totals 715 1,150 1,865 Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 13

Table 2. Capture histories for razorback suckers collected March 1-10, 2005, USBR Palo Verde and Cibola divisions, lower Colorado River, with mark (PIT tag number, stocking date, RM1, Sex1, TL1 [mm]), and capture (recapture date, RM2, Sex2, TL2 [mm], WT [g]) event data for population estimation, dispersal data (river miles dispersed and timeframe [days]), and growth rate (mm/day). PIT Stocking date RM1 Sex1 TL1 Capture date RM2 Sex2 TL2 WT TL change 422E4B6436 11/4/2004 119 Female 400 03/07/2005 119 Female 459 1030 59 0 123 0.48 422E503257 11/4/2004 119 Female 385 03/08/2005 119 Female 444 1150 59 0 124 0.48 4236651435 11/4/2004 119 Female 420 03/08/2005 119 Female 450 1220 30 0 124 0.24 423C105029 11/4/2004 119 Female 395 03/07/2005 119 Female 460 1130 65 0 123 0.53 45772B3650 2/4/2005 114 Juvenile 350 03/03/2005 114 Juvenile 359 476 9 0 27 0.33 4579023625 2/4/2005 114 Male 335 03/03/2005 114 Male 335 400 0 0 27 0.00 4579045523 2/4/2005 114 Female 389 03/03/2005 114 Female 390 722 1 0 27 0.04 4579137A78 2/4/2005 114 Juvenile 315 03/03/2005 114 Juvenile 318 338 3 0 27 0.11 45791E6615 2/4/2005 114 Unknown 404 03/02/2005 114 Unknown 409 848 5 0 26 0.19 4579252524 2/4/2005 114 Male 325 03/03/2005 114 Male 325 410 0 0 27 0.00 4579781B73 2/4/2005 119 Juvenile 376 03/07/2005 119 Juvenile 384 706 8 0 31 0.26 4602760525 2/4/2005 114 Juvenile 315 03/02/2005 114 Juvenile 318 332 3 0 26 0.12 4603106308 2/4/2005 114 Juvenile 365 03/03/2005 114 Juvenile 362 570-3 0 27-0.11 4603606231 2/4/2005 114 Juvenile 360 03/02/2005 114 Juvenile 366 588 6 0 26 0.23 460424505A 2/4/2005 114 Juvenile 382 03/02/2005 114 Juvenile 375 702-7 0 26-0.27 46046F355C 2/4/2005 114 Female 436 03/03/2005 114 Female 435 920-1 0 27-0.04 460479285A 2/4/2005 114 Juvenile 335 03/03/2005 114 Juvenile 337 470 2 0 27 0.07 Disp. RM Disp. Time mm/ day Table 3. Capture histories for razorback suckers collected March 1-10, 2005, USBR Palo Verde and Cibola divisions, lower Colorado River, with mark (PIT tag number mark date, RM1, Sex1, TL1 [mm], WT1 [g]) and recapture (recapture date, RM2, Sex2, TL2 [mm], WT2 [g]) event data for population estimation, dispersal data (river miles dispersed and timeframe [days]), and growth rate (mm/day) and (g/day). PIT Mark date RM1 Sex1 TL1 WT1 Recap date RM2 Sex2 TL2 WT2 TL change WT change 407F412831 5/19/04 100 Unkn 402 Unkn 3/8/05 119 Female 505 1374 103 Unkn 19 293 0.35 Unkn 407F4E5178 1/15/05 114 Female 531 1716 3/1/05 114 Female 540 1758 9 42 0 45 0.20 1.07 422D703A15 1/18/05 114 Juvenile 361 506 3/8/05 119 Juvenile 370 650 9 144 5 49 0.18 0.34 422E7B1F18 1/14/05 119 Female 435 950 3/7/05 119 Female 445 1048 10 98 0 52 0.19 0.53 Disp. RM Disp. Time mm/ day g/day Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 14

Table 4. Locality, time, date, temperature, electrical conductivity, and total dissolved solids (TDS), USBR Palo Verde and Cibola divisions, lower Colorado River, 1-10 March 2005. Location Time Date Surface Temp. ( C) Conductivity (µs/cm) TDS (ppm) A-10 Backwater, Upper Section 19:00 3/2/05 17.9 1070 530 A-10 Backwater, Upper Section 18:57 3/3/05 18 1130 563 Sandy Cove (Hippie Hole) 19:40 3/4/05 17 1320 659 A-10 Backwater, Lower Section 19:05 3/1/05 18.2 1180 590 Main Channel 19:15 3/5/05 14.9 883 440 A-7 Backwater, Lower Section 19:00 3/6/05 17.4 1034 517 A-7 Backwater, Upper Section 19:11 3/7/05 18.5 1072 536 A-7 Backwater, Upper Section 18:54 3/8/05 19.2 1078 536 Main Channel 19:10 3/9/05 15.6 782 395 Trip Report 20: Palo Verde and Cibola Divisions, 1-10 Mar 2005 15