POTENTIAL FOR TRANSFER OF NON-NATIVE

FISH IN CENTRAL ARIZONA PROJECT CANAL WATERS

TO THE GILA RIVER SYSTEM

by

William J. Matter

School of Renewable Natural Resources

University of Arizona

Tucson, AZ

December 1990 TABLE OF CONTENTS

Page

I. INTRODUCTION ..... 1 II. PURPOSE ..... 2 III. METHODS AND SCOPE OF WORK ..... 3 IV. CURRENT DISTRIBUTION OF FISH ..... 4 STRIPED BASS ...... 4 WHITE BASS ...... 5 BLUE TILAPIA ..... 6 TRIPLOID GRASS CARP ...... 7 RAINBOW SMELT ...... 8 V. POTENTIAL SITES OF FISH ESCAPE ..... 9 WATER RELEASED FROM LAKE PLEASANT ...... 9 WATER RELEASED FROM CAP OR SRP CANALS ...... 10 WATER RELEASED FROM GRIC AND SCIDD CANALS .... 12 HUMAN TRANSPORT OF FISH .... 17 VI. ENVIRONMENTAL REQUIREMENTS, LIFE HISTORY AND SPECIES INTERACTIONS .... 19 STRIPED BASS .... 19 WHITE BASS .... 26 BLUE TILAPIA .... 30 TRIPLOID GRASS CARP .... 32 RAINBOW SMELT .... 35 VII. ASSESSMENT OF POTENTIAL FOR TRANSPORT AND REPRODUCTION .... 38 STRIPED BASS .... 39 WHITE BASS .... 46 BLUE TILAPIA .... 50 TRIPLOID GRASS CARP .... 54 RAINBOW SMELT .... 55 VIII. POTENTIAL IMPACTS ON FISH OF ARAVAIPA CREEK . .... 57 STRIPED BASS .... 57 WHITE BASS .... 58 BLUE TILAPIA .... 58 TRIPLOID GRASS CARP .... 59 RAINBOW SMELT .... 59 IX. POTENTIAL IMPACTS ON FORAGE OF BALD EAGLES . . 60 X. RECOMMENDATIONS ...... 62 INTRODUCTION The Central Arizona Project (CAP) Aqueduct is designed to deliver water from the Colorado River to central and southern Arizona for agricultural, municipal and industrial uses. A detailed description of the Aqueduct, its pumping stations and the Aqueduct route are presented by Mueller (1990). Only a brief

summary is provided below and in Figure 1. The 335-mile canal system begins at Lake Havasu on the

Colorado River. Water is lifted to the Hayden-Rhodes Aqueduct and carried to Lake Pleasant, on the Agua Fria River. CAP water will be stored in Lake Pleasant during the winter and released to the Aqueduct in the summer after completionof new water retention and conveyance structures at the lake. The Hayden- Rhodes Aqueduct continues from Lake Pleasant to the Salt River

where it passes under the Salt River and joins the Salt-Gila Aqueduct. The Salt River Project (SRP) interconnects with the CAP at this juncture. The Salt-Gila Aqueduct transports water south and beneath the Gila River bed. Distribution canals (e.g., the Pima Lateral Feeder Canal, the Hohokam Lateral Extension Canal, and the Santa Rosa Canal and turnouts to the Florence-Casa

Grande Canal) deliver CAP water from the Salt-Gila Aqueduct to the Gila River Indian Community (GRIC), the San Carlos Irrigation and Drainage District (SCIDD), and other area agricultural water users. The Salt-Gila Aqueduct carries water to the Tucson Aqueduct, which flows south under Interstate 10 and the Santa

1 Fig.1 ARIZONA DRAINAGES AND THE C.A.P.

POWELL LAKE

0\-

LAKE MEAD

LAKE ri:HAVE FLAGSTAFF

9-

LAKE HAVASJ

LAKE

)-ERSESH:ERESOWOIR

LAKE R_EASANT BARTLETT RESERVOIR 0 C RECISEVEL CANAL PHOENIX 0 4 %

SAN CARLOS

4,711 CREEK 4 0 rn v A GREEK 7I ipp r z s co m z s REDfIc'D "s' pwas

TUCSCN LEGEND ti PERENNIAL STREAM cV INTERMITTENT STREAM iv C.A.P. CANAL Cruz River and west of Tucson to the southern boundary of the San Xavier District of the Tohono O'odham Nation.

PURPOSE Several non-native species of fish will be transported in CAP water and will be introduced to the irrigation systems receiving water from the CAP. A literature review and analysis of the potential for introduction of non-native fishes into waters of central Arizona was presented by Grabowski et al. (1984). However, since then, the decision was made to deliver CAP water to the San Carlos Irrigation and Drainage District

(SCIDD) and the Gila River Indian Community (GRIC) irrigation systems (U.S. Bureau of Reclamation 1989). The close proximity of these canal systems to the Gila River (Figure 2) has focused attention on the possibility of water and fish being delivered into the river bed and resulting in the introduction of non- native fish into the Gila River and its tributaries above

Ashurst-Hayden Dam. The potential for introduction of non-native fish into waters (e.g., Arivaipa, Redfield Canyon and Hotsprings Creeks) with threatened or endangered native fish species (i.e., spikedace, Meda fulgida; loach minnow, Tiaroga cobitis; roundtail chub, Gila robusta) is of special concern. The general objectives of this study are: 1) to update life history information on the species studied by Grabowski et al. (1984), striped bass (Morone saxatilus), white bass (M. chrysops), and blue tilapia (Tilapia aurea), in order to reassess

2 the potential for these species to survive and reproduce in the CAP Aqueduct and lateral canals, and the potential of fish to be transported into drainages in central Arizona where they currently do not exist, 2) to provide this same information for two species not previously reviewed, rainbow smelt (Osmerus mordax) and triploid hybrid grass carp (Ctenopharyngodon idella), 3) to assess the potential impacts of these non-native fish on the existing aquatic communities in natural waters. Also, we will identify areas where fish are likely to escape from irrigation waters into drainages of central Arizona and recommend how to reduce or prevent the movement of fish into these waters.

METHODS AND SCOPE OF WORK We conducted a literature review to find pertinent information on fish existing in Lake Havasu, Lake Pleasant, the Salt and Gila Rivers, Picacho Reservoir and the CAP Aqueduct system. Several data bases (i.e., AGRICOLA, NTIS, Monthly Catalog, BIOSIS and Zoological Record) were searched to find information related to the ecological requirements of the species of concern. The review included primary journals and secondary sources such as symposia and management agency reports. Interviews of agency personnel involved in work with the fish species of concern were conducted and documented where appropriate. Potential sites for the release of non-native fish in CAP waters were identified in meetings with representatives of

3 the GRIC, the SCIDD, and the Bureau of Reclamation, and were verified by on-site inspection. Assessment of the potential for fish transfer and potential for damage will concentrate on the Gila River system upstream of Ashurst-Hayden Diversion Dam and natural drainages in the region that may come in contact with water from the CAP system.

CURRENT DISTRIBUTION OF FISH A survey of the distribution of fish in waters of central Arizona and the CAP (Table 1) indicates that a broad variety of non-native species already have become established in streams and reservoirs of the region. The primary focus on fish transfer through movement of CAP water concerns species not yet introduced or established. STRIPED BASS Between 1962 and 1964, striped bass were stocked into Lake Havasu by the California Department of Fish and Game, Arizona Game and Fish Department and the Fish and Wildlife Service and have developed naturally reproducing populations. The fish can be found throughout the lower Colorado River. Mueller (1990) has documented changes in the number, size, and distribution of striped bass in the CAP Aqueduct. A number of striped bass have been able to reside and grow in Reach 1 of the Hayden-Rhodes Aqueduct and may be capable of contributing eggs and larvae to downstream areas. Striped bass now occur throughout the CAP, however only 2% of all striped bass collected were found below Table 1.Distribution of fish in the CAP Aqueduct and in waters contiguous with or in close proximity to the Aqueduct.

SITES

• R. Res. 41 Carlos ,•

_; Salt

_; • San

SPECIES OF CONCERN

Morone chrYsoos 1,5 a, gaxatilis 1 9 9 9 Tilaclig ure 5 12 11 3

OTHER EXOTICS

Ictiobus cwrinellus 10

Lepomis cyanellus 1 9 s 1,8 10 1 11 9 8 2 4 9 L. macrochirus 1 9 1,5 1,8 10 1 11 1 9 8 4 9 L. micolophus 1 9 s 10 11 Micropterus dblomie4 10 E. solmoides 1 9 1,5 1,8 10 1 11 9 8 2 4 3 9 Pomoxis snnularis 1,5 P. pigromacutatuS 1 9 1,5 8 10 1 11 9 s

Porosoma petenense 1 9 1,5 1,8 10 1 11 9 8 4 9

Carassius auratus 1 9 1,5 11 8 4 Cyprinus carpio 1 9 1,5 1,8 10 1 11 9 8 2 Notemigonus crysoleubus 1,5 Cypromella lutrensis 1 9 1 1 1 11 2 4 Pimephales promotes 11 2 4 7

Ameirus metes 11 4 3 A. natalis 1 9 10 11 Ictalurus punctatus 1 9 1,5 1,8 10 1 11 8 2 4 3 Pilodictis oliyaris 1 9 1,8 10 11 9 8

Morone mississippiensis 10 1 11 Table 1. Continued

SITES

3 Res.

0 C.

• • R. Pleasant L. Salt Aravaipa

OTHER EXOTICS - continued

Stizostedion vitreum 10 13 13

Gambusia affinis 1 1,5 1 1 11 2 4 3 Poecilia latipinne 1

Oncorhynchus mykiss 1 13 1 11 47 Satvelinus fontinaiis 1 1 11 47

NATIVE SPECIES

Catostomus clarki 1 10 1 11 2 4 6,7 4 9 G. insignia 1,5 1 11 9 a 2 6,7 4 C. latipinnis Xyrauchen texanuS 1 9 14 1 Aoosia chrysogaster 1 1 11 2 4 6,7 4 Gila eleoans G. intermedia 6,7 G. robusta 1 11 4 Neck' fulgide 4 Ptychochetius luclus Phinichthva oscutue 6,7 4 Tiaroga cobltis 4

1 e Grabowski et el. (1984); 2 so Kepner et al. (1983); 3 mg Jalde and Baucom (1983); 4 = Jackson et at. (1987); 5 • Norgensen (1990); 6 • Griffith and Tierech (1989); 7 • Natter and Hill (1988); 8 • Brooks (1986) end Jim Johnson, VMS, pers. comm.); 9 a Mueller (1990); 10 • Warnecke (1988); 11 • Harsh and Minckley (1982); 12 = BioSystems Analysis, Inc. (1988); 13 = L. Riley (Az G&F, pers. comm.); 16 • N. Jakle (USSR, pers. comm.) Reach 1 (the first 27.4 km of open canal below the Buckskin Mountain tunnel at the head of the aqueduct), which is deeper, wider, and subject to lower water velocities than the remainder of the aqueduct. Striped bass will gain access to Lake Pleasant after it is connected with the CAP, and early life stages probably will be carried into lateral canals that supply water users. One large (about 20 in) striped bass and several dozen fingerlings have been seen in the Santa Rosa Canal near the Gila River and Ak-Chin Indian Reservations in 1989 and 1990 (Tony Porti, University of Arizona Maricopa Agricultural Center, pers. comm.). Although no specimens were collected, fish were baited to the surface with pelleted fish food, and visual identification was made. Several private aquaculturists have listed striped bass as a potential species for culture, but the species is not yet being raised (Bill Silvey, Arizona Game & Fish Dept., pers. comm.). Hybrid fish (striped bass x white bass) are being raised on the Ak-Chin Indian Reservation (Tony Porti, University of Arizona Maricopa Agricultural Center, pers. comm.). WHITE BASS Lake Pleasant supports the only population of white bass in the state. Once the reservoir is connected to the CAP Aqueduct, young white bass eventually will be carried to canal sites below the interconnection (Mueller 1990). The distribution of white bass in Lake Pleasant, relative to the depth of the water outlet

5 tunnels, is not known, nor is the susceptiblity of white bass to entrainment. BLUE TILAPIA Blue tilapia were stocked by the Arizona Game and Fish Department in the late 1960's in the drainage above Alamo Lake in western Arizona (Grabowski et al. 1984), and subsequently became established in the reservoir. Tilapia may have passed or will pass out of Alamo Lake, into the Bill Williams River and into Lake Havasu. However, no tilapia have been taken from Lake Havasu during regular fish surveys (Grabowski et al. 1984, Brad Jacobson, Arizona Game and Fish Dept., pers. comm.) nor from the

CAP Aqueduct (Mueller 1990). Several Tilapia aurea were collected from Lake Pleasant in 1988 (Morgensen 1990) for the first time. Thus, the species may enter the Aqueduct once Lake Pleasant is connected to the system even if Tilapia are not established in Lake Havasu. Tilapia were collected recently from Saguaro Lake (BioSystems Analysis,

Inc. 1988), the first record in the Salt River system. Tilapia also have been reported from the Verde River below Horseshoe Lake (Larry Riley, Arizona Game and Fish Dept., pers. comm.). Many

(>500) Tilapia (probably T. aurea) were collected in the upper most reach of the SRP South Canal during a "dryup" on November 2, 1990. This section of the canal is immediately downstream of

Granite Reef Dam and upstream of an electric fish barrier which prevents upstream movement of fish. The most likely source of these fish is the Granite Reef Forebay, the lower most perennial

6 reach of the Salt River (Larry Riley, Arizona Game and Fish

Dept., pers. comm.) It was feared that Tilapia would be introduced to the Salt and Verde Rivers through CAP water, but the species already has entered the systems independent of the CAP. Both river systems and the Aqueduct may act as sources for further spread of the species.

Tilapia also were collected from Picacho Reservoir in 1982

(Jakle and Baucom 1983). Recent dry-up of the reservoir and concurrent draw-down of the feeder canals presumably has eliminated them (Will Hayes, Arizona Game and Fish Dept., pers. comm.), but the reservoir clearly offers a habitable environment for Tilapia.

TRIPLOID GRASS CARP Grass carp have been used widely for biological control of aquatic vegetation. However, concern over the adverse effects of naturally reproducing populations in waters receiving them (intentionally or non-intentionally) have blocked the use of grass carp in many areas. Triploid fish (three sets of chromosomes) have been produced by several types of treatments to newly fertilized eggs, and these triploids are expected to be functionally sterile. The State of Arizona has a permitting system for the introduction and use of triploid grass carp for control of aquatic weeds. Fish may be added to "closed" aquatic systems and fish must be certified as triploid and free of specific agents of disease. The Central Arizona Water Conservation District (which

7 operates the CAP) has permits to introduce triploid grass carp into the Hayden-Rhodes and Tucson Aqueducts, and currently has the fish in selected reaches. Bar screens (2-inch spacing) are used to prevent movement of grass carp (stocked at a size with a minimum head width of 2.25 in) out of canals. Triploid fish also have been stocked in selected SRP canals fitted with bar screens. These fish are not likely to enter other waters unless transported by humans or lost from canals subject to catastrophic failure. RAINBOW SMELT The Utah Department of Natural Resources has proposed to introduce rainbow smelt into Lake Powell to provide an additional forage fish for striped bass and other piscivores (Gustaveson et al. 1990). Striped bass have undergone a reduction in growth and body condition, and numbers of threadfin shad (Dorosoma petenense), the primary forage for striped bass, have been sharply reduced in recent years. Overpopulation of striped bass and resultant overexploitation of shad are the suggested causes of these changes (Gustaveson et al. 1990). Rainbow smelt are a

pelagic, deep-water (cool-water) planktivore that may be more

available to striped bass and walleye than are shad, which occupy inshore and warm water areas not readily available to striped bass. If rainbow smelt are introduced to Lake Powell, they probably would be carried to waters downstream. Eventually they could reach Lake Havasu and be available for entrainment and

8 transport in the CAP Aqueduct. The decision to introduce rainbow smelt to Lake Powell has not been made yet.

POTENTIAL SITES OF FISH ESCAPE The sites for assessment of the potential for fish escape were identified in consultation with biologists from the Bureau of Reclamation, the Fish and Wildlife Service and Arizona Game and Fish Department. The scenarios of concern include: 1) water released from Lake Pleasant into the Agua Fria River, 2) water released from the CAP or SRP canals into the Salt River bed below Granite-Reef Dam, 3) water released from canals in or the near Ak-Chin and Gila River Indian Communities and the San Carlos Irrigation and Drainage District to the Gila River bed below Ashurst-Hayden Diversion Dam, and 4) transfer of fish from any of these waters by humans.

WATER RELEASED FROM LAKE PLEASANT Water from Lake Pleasant is released to a small downstream reservoir and is diverted for irrigation at Camp Dyer Diversion Dam or passes over the diversion spillway into the Agua Fria River bed, which is normally dry. Spill over the diversion dam has occurred only six times during the 70-year period of record by the USGS; in the 1941, 1966, 1978, 1979, 1980, and 1983 water years (Boner 1988). Under normal operations in the future, water will be delivered from the Hayden-Rhodes Aqueduct to Lake Pleasant via the Waddell Canal in the winter and released from Lake Pleasant

9 to the aqueduct during the summer. Water would be released to the Agua Fria River only during flood conditions or for safety of the dam. Data from the hydrologic engineering section of BR indicate that: 1) no water will be released for floods up to the 25-year flood, 2) water will start to be released through the river outlet tunnels (located at about 90 and 194 ft below the water surface) at flows somewhere between the 25 and 50-year flood, and all of the water expected to be released up to and during the 50-year flood (9,000 cfs) can pass through the river outlet works and the pump-generating plant bypass (capacity 9,500 cfs), 3) somewhere between the 50 and 100-year flood, water from the reservoir surface will have to be released over the spillway, and, at the 100-year flood, 11,000 cfs is expected to be released; 9,500 cfs from deep in the reservoir and 1,500 cfs from the surface of the reservoir. These data indicate that release of water to the Agua Fria will continue to be a relatively rare event. Releases during floods up to the 50-year flood are likely to transport only cool water species because of the depth of the outlets. Warm water fish in surface waters will be released over the spillway in floods somewhat greater than the 50-year flood.

WATER RELEASED FROM CAP OR SRP CANALS Water in the CAP Aqueduct passes under the Salt River bed just downstream of Granite Reef Dam. A turnout structure and the CAP/SRP Interconnection facility on the south side of the river allows water to be delivered to the Arizona and South Canals

10 "downstream" of their connection to the Granite Reef forebay. Electrical fish barriers in the Arizona and South Canals above the connection with the CAP are designed to prevent upstream movement of fish to the Granite Reef Forebay (and the lower Salt River). Water also can be delivered to the river bed below Granite Reef Dam for proposed groundwater storage or for emergency release of excess flood water from the CAP/SRP Interconnection or from the Hayden-Rhodes Aqueduct (Salt River

Project 1988). Other provisions for emergency release of storm waters in the lower SRP canal system into the Salt River bed are potential avenues for release of non-native fish. Also, flooding and failure of some SRP canals running south of the Salt River could result in release of water that eventually could run to the Gila River below Ashurst-Hayden dam, but such an event is remote (Tim Phillips, Salt River Project, pers. comm.). Granite Reef Dam and the electric fish barriers in the SRP canals are regarded as an effective barrier to upstream movement of fish (except by human transport) into the upper Salt and Verde Rivers (Salt River Project 1988, Martin Jakle, Bureau of Reclamation, pers. comm.). Fish released to the Salt River could reach waters with native fish by traveling downstream to the confluence of the Salt and Gila Rivers and then moving upstream in the Gila and San Pedro Rivers.

11 WATER RELEASED FROM GRIC AND SCIDD CANALS The Gila River is impounded by Coolidge Dam (forming San Carlos Lake) primarily to store water for irrigation. Water released from the dam flows about 68 miles in the Gila River bed to Ashurst-Hayden Diversion Dam and is diverted into the Florence-Casa Grande Canal. The Gila River Indian Community, a primary user of Gila River water, agreed to leave a portion of its water allocation in San Carlos Lake during 1989 in order to provide a minimum pool to prevent significant fish die-offs (U.S. Bureau of Reclamation 1989). CAP water has been made available temporarily to replace the water retained in the reservoir. This CAP water has been transferred from the Salt-Gila Aqueduct to the Pima Lateral Canal (Figs. 2 & 3), a lateral canal off of the Florence-Casa Grande Canal via the Pima Lateral Feeder Canal (PLFC) in 1989. An electrical fish barrier was installed in the Pima Lateral Canal above the point of entry of the PLFC to block fish carried in CAP water from moving upstream into the Florence- Casa Grande Canal and on to the Gila River above Ashurst-Hayden Dam (Fig. 3). In 1990, CAP water was delivered to the Pima Lateral Canal via the PLFC and to the Florence-Casa Grande Canal via the Hohokam-Casa Grande Extension turnout. An electrical fish barrier was installed near the head of the Florence-Casa Grande Canal (about 2 miles downstream from the Ashurst-Hayden Dam) to prevent fish carried in CAP water from moving upstream into the Gila River above the dam (Fig. 3).

12 FIGURE 2 GILA RIVER INDIAN COMMUNITY GENERAL LOCATION MAP

-GRANIrt REEF DAM

taa r- In • 'motive MARICOPA_ COUNTY Ft act PHOIENIX PINAL COUNTY 0

Imp, Apache Jet C•NAL ..„...... -- _____m,—•-•■,<-----' \ 44 ° ergi ta e COAX II weRICOPA i .... . CANAL COLON , L.. 4... 1 \ Milted

I Clteeeller 0

I GILA ‚I. RIVER Jet

MARICOPA COUNTY

're MAL COUNTY C3

$UYTES ' DAM SITE

IOC C4•4t ewes ASHUR ST- on HAYDEN 00 AK PLO NNNNN CANAL DIVERS ION CHIN DAM COMMUNITY INDIAN RESERVATIO

PloottNcr -cAs. ANANOt ..... AIINI1VIV — PICACHO rileolle14 RESERVIOR

SANYA 03A atINNNO

N CANA.. San Carlos Lake Arrows show direction of flow

ttte4 °41 Sa Coolidge Dam ,u4 0 A.V1et 4 -- S4teduct CPP- t eVb SJ Ashunt-Hayden o Diversion Dam North Side Canal • , 44' Electric Fish Barrier s Return • !i • S. ./ •5 Flow / • • r / • • 4,4 ••K • Retwn • 44i Flow •

40/0 Key TO TURNOUTS (LISTED IN ORDER OF CONSTRUCTION) Return T1 Cue Grande Extension Turnout Flow Electric Fish Barrier Ti . Pima Lateral Turnout 13 Florence Cross Cut Turnout Pima Lateral 14 = Florence Canal Turnout 15= North Side Canal Turnout .1 NIL Return r % Flow Hohokam Canal (Not to Scale) TI

FIGURE 3. CURRENT AND PLANNED CAP TURNOUTS AND RELATION TO MAJOR CANALS AND WATERWAYS (MODIFIED FROM BUREAU OF RECLAMATION 1990). There is concern that with continued delivery of CAP water to water users near the Gila River drainage, fish will gain access to the Gila River system by downstream movement in lateral canals and transport to the river bed with accidental or purposeful spillage of water. Water carried in the lateral canals may find its way to the Gila River bed below Ashurst- Hayden Dam in several ways:

1. Heavy local and regional rains may cause excess water to be carried in canals. This water may be released through spillways to washes or land areas that slope to the Gila River bed. The two most upstream spillways occur in the SCIDD canal system at about 2.5 and 6 miles below Ashurst- Hayden Dam. These outlets are used infrequently (only once

in the past 3 years) and released water does not always run all of the way to the river before becoming subsurface (Tom Neuman, San Carlos Irrigation and Drainage District, pers. comm.). However, storm events that result in release of water through spillways often will also result in surface flows in the Gila River below Ashurst-Hayden Dam, increasing the potential for fish passage above the dam when fish are released with water through spillways. 2. The Pima Lateral Canal goes under the Gila River in the Olberg siphon at the Olberg bridge east of Sacaton, Arizona (about 30 miles below Ashurst-Hayden Diversion Dam). Trash racks at the siphon are cleared of debris by opening gates at the siphon entrance and sluicing water across the racks

13 and into the Gila River bed. Sluicing occurs regularly, sometimes two times per week. The sluice gate is also used to release excess water from storm flows to the river bed. A permanent pond has been created in the river bed below the sluiceway. No other such sites of regular water release have been identified. 3. Most irrigation canals are built to withstand storm flows associated with a 25-year event, but heavy rainfall in very localized areas can produce overland and wash flows that cause canal failure and spillage of water (Jeff Harlan, U.S. Bureau of Reclamation, Arizona Operations, pers. comm.). These local events are far more frequent than true 25-year storms. Such storm-caused failure is more likely for unlined than for lined canals, especially when rodent burows occur in the canal sides. Spillage of water from earthen canals is likely to occur from at least one site in the SCIDD and GRIC systems each year (Tom Neuman, San Carlos

Irrigation and Drainage District, pers. comm.). Water spilled from most of the GRIC canals flows toward the Gila River bed. Water spilled from more southern canals (i.e., the Hohokam Canal, Florence-Casa Grande Extension west of

Picacho Reservoir, and Santa Rosa Canal and their lateral canals) flows toward the Santa Cruz River bed. Fish carried in water released from these sites would have to survive transport to the Santa Cruz River, move downstream to the confluence with the Gila River (near the confluence with the

14 Salt River), and ascend the Gila River to Ashurst-Hayden Dam, and pass "through" the dam to gain access to the perennial reach of the Gila River. Thus, transport of fish to the Gila River above Ashurst-Hayden Dam is far more likely to occur with failure of GRIC and SCIDD canals bordering the Gila River and close to the dam than with failure of canals near the Santa Cruz River (and its tributaries). 4. Some excess irrigation water is stored in long, narrow "sumps" or ponds and pumped into distribution canals when needed. There are 2-3 of these sumps on the Gila River Indian Reservation that are permanent and currently hold fish. These sumps are not within the 100-year floodplain of the Gila River so are not likely to be captured by the river during storm flows, but these sumps could fill, breach and spill water that could flow to the river. Excess water carried in the Santa Rosa Canal is stored in a large sump at the downstream terminus of the canal, on the southwest boundary of the Ak-Chin Indian Reservation. Spillage from this reservoir-like sump is rare, but would flow into the Vekol Wash and downstream to the Santa Cruz River bed. Fish released from this site would have to travel to the confluence of the Santa Cruz and Gila Rivers and ascend the Gila River past Ashurst-Hayden Dam to reach the perennial Gila River. This would be a far more unlikely event than transport of fish released to the Gila River near the dam.

15 5. Picacho Reservoir is an irrigation water wasteway, a storage area for storm runoff and irrigation water, and a sedimentation basin for SCIDD. Water is diverted to Picacho Reservoir primarily through the Florence-Casa Grande Canal (Fig. 2). Water and fish held in the reservoir have no direct route for spillage into the Gila or Santa Cruz River beds. However, the reservoir may offer habitat for the survival and proliferation of non-native fish and thereby enhance the probability of the presence of fish in canal waters contiguous with Picacho Reservoir and indirectly enhance the chances of fish transport with spillage of canal waters. However, Picacho Reservoir is shallow, warm, susceptible to low dissolved oxygen (Jakle and Baucom 1983), and is subject to severe changes of water level. These conditions will limit its suitability for some fish species of concern.

Fish that enter the Gila River via any of the modes noted above could move to the base of Ashurst-Hayden Dam if there is sufficient flow in the river. Although the river is frequently dry, data on water flow from the USGS (Bureau of Reclamation 1990) indicate that an average of about 18,000 acre-feet of water are sluiced or spilled at Ashurst-Hayden Dam each year. Thus, each year there usually will be opportunities for fish released to the Gila River bed to travel to the base of the Ashurst-Hayden Dam. Opportunities for fish to pass "through" or around the dam are probably lower than for movement to the dam, but probably at

16 least one storm event in most years will offer access to the Gila

River above the dam. The Ashurst-Hayden Dam is not an effective barrier to upstream movement of fish (U.S. Bureau of Reclamation 1989, Appendix A), so that fish can gain access to the Gila River and its tributaries above the dam. HUMAN TRANSPORT OF FISH

Unauthorized transport and release of fish by private citizens has been and continues to be a common phenomenon. Quantification of the frequency of such transport is virtually impossible due to: 1) the circumstantial nature of the evidence (species appear at sites with no obvious natural route of introduction), 2) the inability to document numbers of "unsuccessful" introductions (i.e., fish are released but do not survive and reproduce so are not found), 3) the anecdotal nature of even official records. Despite these difficulties, it is safe to conclude that unauthorized transport of fish by humans is common, probably more common than even many biologists would estimate. As an example, I will summarize some of the reports of fish transport encountered during preparation of this document. Grabowski et al. (1984) reported that white bass probably were first introduced to Elephant Butte Lake on the Rio Grande River, New Mexico by anglers, and only later were stocked by the State Game and Fish Department. Unauthorized transport of white bass has continued, with introductions in the Pecos River drainage and into Lake Farmington in the San Juan River drainage

17 (Mike Hatch, New Mexico Department of Game and Fish, pers. comm.). In his survey of fish in the CAP Aqueduct, Mueller (1990) found Sonora and desert sucker. He suggests that the most likely route for their introduction was by human transport. He also documented the presence of adult largemouth bass in a section of the Aqueduct only a few weeks after it was filled by pumps that adult bass could not negotiate. Mueller received verbal reports that these fish were purposefully stocked by canal construction workers. A 27-lb striped bass was caught by an angler fishing in one of the urban lakes in the Mesa, Arizona area in 1990 (Larry Riley, Arizona Game and Fish Department, pers. comm.). Although water is supplied to the lake via the SRP system, several conditions make it highly unlikely that this fish entered the lake with a water delivery. Angler transport is the most likely explanation for its presence.

Mueller (1990) documented the occurrence of "trespass angling" in the CAP Aqueduct. Fishing is permitted (and occurs) in irrigation sumps on the GRIC lands. Anglers are quite likely to transport fish from canal waters to other water bodies and, conversely, to release fish from streams and reservoirs into canals. Fish carried in CAP water may be at least as likely to reach the Gila River above Ashurst-Hayden Dam by human transport as by release to the river bed below the dam during spillage of irrigation water.

18 ENVIRONMENTAL REQUIREMENTS, LIFE HISTORY AND SPECIES INTERACTIONS

The purpose of this material is to update the review of environmental requirements, life history and species interactions by Grabowski et al. (1984). Information on populations residing in inland reservoirs and canal systems was the primary focus of this review. Generally no discussion is provided if new materials are virtually identical to past findings or if no new reports were found. STRIPED BASS In reservoirs and tailwaters, adult striped bass are found near sharp dropoffs and submerged islands and trees (Lamprecht and Shelton 1986, Hampton et al. 1988). In riverine areas, adults occur along shorelines with structure, such as rocky banks or obstructions that create eddies (Cheek et al. 1985). Recent information on habitat selection by striped bass continues to suggest that water temperature and dissolved oxygen are the most important (and most well studied) conditions that effect the distribution of striped bass of all life stages.

Coutant (1985) provides more evidence for the "temperature oxygen squeeze" concept he introduced earlier to account for summer die-offs, decreased fecundity and susceptibility to

crowding stress observed in striped bass throughout the U.S. (see review by Matthews 1985). The temperature-oxygen squeeze is created by the restriction of striped bass, especially larger fish, to the zone of deep, cool waters near or below the thermocline in reservoirs. The habitable part of this zone

19 shrinks as dissolved oxygen is depleted and fish are "squeezed" into the remaining waters with acceptable temperature and oxygen. Clearly, temperature and oxygen should be treated together, however, for convenience, these environmental features will be reviewed separately. Temperature Adults Grabowski et al. (1984) found the reported tolerance range for adult striped bass to be from 10.5-26 C, and that adults avoided waters over about 25 C. Recent work suggests that the upper limit may be slightly higher than 26 C. Adult and subadult striped bass in Lake Texoma, Oklahoma-Texas, concentrated above the "chemocline" in water at 28.5 C and dissolved oxygen of 7.2 mg/liter during summer stratification (Matthews et al. 1985). Fish were forced into these waters because of oxygen depletion at greater depths. For most of July to the beginning of September, the entire water column in Lake Texoma had temperatures above 25 C or dissolved oxygen below 2.0 mg/liter. There was no evidence of summer die-off. In Wilson Reservoir, Kansas, a well-mixed, non-stratifying reservoir, Hampton et al. (1988) regularly tracked adult striped bass in water over 25 C for 2 months, but oxygen was never below 6 ppm. Fish were exposed to a maximum temperature of 27 C. No mortality was reported. In Keystone Reservoir, Zale et al. (1988, Fed. Aid Fish Restor. Rpt. cited in Matthews et al. 1989) found adult striped

20 bass tolerating temperatures up to 29 C. Large striped bass have been seen in the tailwater below Lake Havasu when the epilimnetic water released from the dam was near 30 C (W.L. Minckley, Arizona

State University, pers. comm.). Despite the possibility that adult striped bass may be able to tolerate waters beyond 26 C, most recent data indicate that they will avoid such temperatures if possible. Adult and subadult fish move from the main body of reservoirs into or near cool tributaries when reservoir temperature exceeded 24-26 C (Cheek et al. 1983, 1985, Moss 1985). Alternatively, fish may move from a lake-wide distribution to localized deep-water sites with cool temperatures and adequate oxygen (Coutant 1985, Matthews et al. 1985, Matthews et al. 1989).

Subadult and Juvenile Fish Data presented by Kellog and Gift (1983), and Coutant et al. (1984) confirm the conclusion by Grabowski et al. (1984) that smaller striped bass prefer and are more tolerant to high temperatures than are adults (tolerance range for subadults = ?-

30 C and for juveniles = 7.2-35 C). Matthews et al. (1989) found that when surface waters exceeded 22 C, large fish could not be found, medium sized fish (1.36-2.27 kg) were significantly less abundant but small fish (<1.36 kg) were still abundant. Catch per unit effort for small fish fell significantly when temperatures exceeded 29 C. Kellog and Gift (1983) found that juvenile striped bass (33-41 mm TL) prefer temperatures near 27

C, and the upper incipient lethal temperature probably is 33-34 C.

21 Larvae and Eggs The data by Hassler (1988) on lethal, tolerance and optimum temperature for eggs and larvae of striped bass are similar to the summary by Grabowski et al. (1984). The tolerance range for larvae is 12-26.7 C and for eggs is 10-27 C. Dissolved Oxygen Grabowski et al. (1984) reported that adult and juvenile striped bass can tolerate oxygen levels down to about 1 mg/liter, but the optimum is greater than 5 mg/liter. Recent reports support this conclusion. Adult fish were limited to areas of Watts Bar Reservoir, Tennessee, where dissolved oxygen was >4.0 mg/liter (Cheek et al. 1985), and to areas with >3-4 mg/liter in Lake Texoma (Matthews et al. 1985). Striped bass <1.36 kg generally were found throughout Lake Texoma (because of their ability to tolerate a broad range of temperatures), but avoided areas with <6 mg/liter oxygen in the summer. Cornacchia and Colt

(1984) found that larval striped bass are extremely sensitive to gas bubble disease from oxygen supersaturation. This sensitivity decreases quickly with age. Foods And Feeding The most significant issue concerning food and feeding in striped bass is their degree of flexibility in prey choice. Some authors have suggested that striped bass are unable to switch

from clupeid prey to alternate foods (Matthews et al. 1988), even when striped bass are nearly starving and alternate prey are available. This is inconsistent with some earlier reports,

22 reviewed by Crance (1984) and Grabowski et al. (1984), of a more catholic diet. Coutant (1985) suggested that prey were not available to starving striped bass in Cherokee Reservoir, Tennessee, because prey were in water at 28-29 C, apparently too warm for striped bass to enter for foraging. Subadult striped bass in Lake Mead depended heavily on threadfin shad (88% of stomach volume), and rarely took other fish species (Wilde and Paulson 1989). However, invertebrates were commonly taken in the spring and shad were relatively rare in the diet despite no perceptible change in the abundance of shad over this time. Striped bass in the CAP Aqueduct fed heavily on shad, but also took a variety of food items, especially after adult shad were virtually eliminated (Mueller 1990). In fact, Mueller (1990) concluded that striped bass seem to have a competitive advantage over other fish in the CAP with regard to food. Fish became the primary food once striped bass reached about 170 mm TL in Clyde York Lake, Tennessee (Curry and Wilson 1985).

The switch from invertebrate prey (primarily crustaceans and immature insects) to fish prey occurred when striped bass were about 200 mm TL in Cherokee Reservoir (Saul et al. 1983). Spawning And Reproduction The review by Crance (1984) indicates that successful spawning in striped bass usually requires a large volume of swift water running over rock to fine gravel substrates. The water flow must be sufficiently swift and stable to keep eggs and newly

23 hatched larvae suspended (>34 hours for eggs; 3-4 days for larvae). This translates to a minimum stream length of about 52 km (33 miles) with a minimum velocity of 30.5 cm/s (1 ft/s) (Crance 1984). However, the number of variables that impact these "minima" make them rules-of-thumb at best. For example, Gustaveson et al. (1984) found strong evidence of successful spawning in the main body of Lake Powell. This unusual phenomenon may be related to unique conditions of dissolved oxygen, water movement and lake substrate that permit survival of eggs and larvae. Mueller (1990) found some striped bass reaching sexual maturity in the first reach of the CAP canal, but no evidence of spawning was found. Self sustaining populations of striped bass virtually require a large reservoir (minimum size of 1,200 ha; Crance 1984) for the rearing and maturation of young and for maintenance of a

clupeid forage base. Movements And Residence In Streams Tagging studies have shown that different populations of

striped bass differ in their annual movements (Coutant 1985). Although the classic pattern for anadromous stocks is to ascend

large rivers during the spawning season and then to move downstream, some striped bass have remained in freshwater(Crance 1984), especially in cool tailwaters of dams, rather than returning to warm coastal areas (Coutant 1985). Lamprecht and Shelton (1986) found that radio-tagged striped bass moved out of a reservoir and upstream into an arm of the Alabama River,

24 Alabama, to spawn in the spring, but these fish remained in the tailwater of Thurlow Dam after the spawning season. They resided in the tailwater until early winter, when cold water from the upstream reservoir triggered fish to retreat to the downstream reservoir. Striped bass also have been found in the Colorado

River above Lake Mead, well outside of the spawning season (Bill Persons, Arizona Game and Fish Dept., pers. comm.). These fish may be seeking forage in the river due to a shortage of prey in the reservoir. Striped bass have been encountered only in the main channel of the Colorado River and at the mouths of major tributaries, but not within any tributaries. For example, no striped bass have been collected in the Bill Williams River between Lake Havasu and Alamo Lake (Brad Jacobson, Arizona Game and Fish Dept., pers. comm.) or in the San Juan River flowing into Lake Powell despite repeated surveys (Mike Hatch, New Mexico Department of Game and Fish, pers. comm.). Again, several studies have shown that striped bass will approach and enter streams feeding reservoirs when cool, oxygenated stream water offers a "refugium" from a temperature- oxygen squeeze in the reservoir (Cheek et al. 1983, 1985, Moss 1985). Such movements do not occur out of Elephant Butte Reservoir, New Mexico because of the lack of adequate surface flows over much of the year and high stream temperature (Paul Turner, New Mexico State University, pers. comm.).

25 WHITE BASS Although white bass are native to large rivers, most recent studies have focused on reservoir habitats (Hamilton and Nelson (1984). These authors note that the species is generally associated with the epipelagic zone of moderately large to large reservoirs and with some reservoir tailwaters. In New Mexico and probably throughout the Southwest, a large reservoir is virtually required for white bass to establish large, self-sustaining populations (Jim Brooks, USFWS, Dexter National Fish Hatchery, pers. comm.). However, Jim Hatch (New Mexico Game and Fish, pers. comm.) suggests that white bass may be reproducing and residing in perennial reaches of the Pecos River mainstream between reservoirs. Adult white bass move into lotic areas to spawn and the adhesive eggs can resist displacement by moderate flows once attached to substrates. Newly hatched larvae have been assumed to be highly vulnerable to displacement by stream flows, but Starnes et al. (1983) found larval white bass able to select low- velocity refugia near bottom substrates in the Holston River, Tennessee. These authors note other recent evidence that larvae of white bass may not be passively transported at the average velocity of stream waters as many entrainment models previously assumed. Temperature As with striped bass, young white bass prefer and tolerate higher temperatures than do adult fish. Grabowski et al. (1984)

26 reported the upper limit to be 31 C for adults, 35 C for YOY and 26 C for larvae and eggs. Hamilton and Nelson (1984), in a review, report similar data. They conclude that the optimum temperature for white bass is 28-29.5 C and that fish are typically found in waters at 19-28 C in summer. Dissolved Oxygen Hamilton and Nelson (1984) reported that white bass were severely stressed at 2 ppm dissolved oxygen and that 1 ppm at 21- 24 C was lethal. Foods and Feeding The review by Hamilton and Nelson (1984) characterized white bass as opportunistic feeders. Shad and alewife are preferred prey but white bass shift readily to macroinvertebrates or zooplankton if forage fish are rare. Germann and Bunch (1985) studied the diet of adult white bass (225-415 mm TL) in Clarks Hill Reservoir, Georgia. Threadfin shad was the predominant prey, comprising 67.5% by volume. Other fish prey included darters, crappie, yellow perch, and sunfish (29.6% of total volume of prey). Sunfish alone accounted for almost 22% of the volume of items. Insects were most common in the diet in the spring (found in about 14% of the fish but made up only 2% of volume of foods). Work by Saul et al. (1982) supports earlier findings that YOY white bass consume primarily cladocerans and chironomids during their first year. The size at which white bass shift to high levels of fish prey may vary, but occurred at about 12.5 cm

27 in Cherokee Reservoir, Tennessee. Hamilton and Nelson (1984) concluded that diets of YOY can vary hourly, seasonally and annually depending on availability of prey. It seems that white bass are regarded as more opportunistic and flexible feeders than are striped bass. Interactions With Other Fish Species

Davine and Shiozawa (1984) studied the co-occurrence of carp and white bass in Utah Lake, Utah. They suggest that the "disruptive foraging" behavior of carp could displace white bass in areas with cover, but that white bass could use more open habitats. No direct observations of such species interactions were made. Movements And Residence In Streams Hamilton and Nelson (1984) noted that data on riverine habitat for white bass are scarce. The movement of white bass out of reservoirs and into feeder streams for spawning is well documented (Grabowski et al. 1984), but there is little information on residency in streams. Jim Brooks (USFWS, Dexter National Fish Hatchery, pers. comm.) has found young white bass in tributaries of the Pecos River, New Mexico (e.g., the Rio Felix) for some months after spawning, but large fish were not found with them, so long-term residency probably is not occurring. He also has documented movement of young white bass as far as 30-40 river miles above Brantley Reservoir in the fall, possibly to forage on stream cyprinids. However, most streams feeding reservoirs on the Pecos

28 River are too small, too warm or too intermittent to support such movements, and adult fish are not in these systems except during spawning. However, white bass are found throughout the perennial reaches of the Pecos River between reservoirs, especially in tailwaters of reservoirs and at sites where irrigation returns join the river (Mike Hatch, New Mexico Game and Fish, pers. comm.). J. Brooks feels that the presence of white bass in streams in New Mexico is dependent on existence of the species in adjacent reservoirs, and the impact of these fish on native fish is still largely unknown. Similarly, white bass move up the Rio Grande River from Caballo Reservoir to the tailwater of Elephant Butte Lake and can be found, at times, in the river between the reservoirs (Ernie Jacquez, New Mexico Game and Fish Department, pers. comm.). Again, their presence in the river is incidental to the presence of the population in the reservoir. Dr. Paul Turner (New Mexico State University, pers. comm.) has found young white bass in the river above Elephant Butte Lake for short periods, but generally flows are too low. Surveys of the Agua Fria River above Lake Pleasant have not shown white bass to occur (Sue Morgensen, Arizona Game and Fish Dept., pers. comm.). Carp move into this part of the Agua Fria River until water depth falls to a few inches. Thus, some fish can and do move into the river, but white bass apparently are not stimulated to do so.

29 BLUE TILAPIA As noted by Grabowski et al. (1984), Tilapia are cold- sensitive and temperature plays a major role in its successful expansion to new waters. Temperature Many of the studies reviewed by Grabowski et al. (1984) suggested that the lower lethal temperature for Tilapia aurea is 6.0-6.5 C, but that some mortality is often seen when temperatures drop below 10 C. Stauffer et al. (1988) concluded that their tests of acclimation and cold shock indicated a lower lethal temperature between 8-11 C. They found that fish acclimated to 15 C suffered no mortality at 11 C, 95% mortality at 8 C and 100% mortality at 5 C and 3 C over 96 hours. Fish exposed to gradual changes of temperature (i.e., 3 C/hour and 1 C/hour) showed increased resistance times. These tests probably are more applicable to conditions in nature. Zale (1987) reviewed reports of Tilapia using stenothermal spring runs when adjacent water bodies cooled in winter. This supports earlier reports that Tilapia are adept at finding thermal refuges. Foods And Feeding Tilapia are viewed as omnivorous opportunists. They ingest filamentous algae, phytoplankton, zooplankton, benthic invertebrates, detritus (Drenner et al. 1984) and possibly eggs and larvae of fish (Shafland and Pestrak 1983). Mallin (1986) found that detritus made up a large part (77 to 99%) of stomach

30 contents of Tilapia aurea living in the heated water from a power plant at Lake Julian, North Carolina. He reported that fish survived periods of low plankton by processing large amounts of detritus. Benthic animals were rare in the diet. Drenner et al. (1984) and Vinyard et al. (1988) have focused on the ability of

Tilapia aurea to filter-feed on plankton and to alter plankton populations. They found that Tilapia suppressed populations of several crustacean and rotifer zooplankton, especially non- evasive species, and large-bodied phytoplankton. It is unlikely that food plays a limiting role in the distribution of Tilapia. Interactions With Other Fish Species Grabowski et al. (1984) cited several authors who felt that predation by largemouth bass would control numbers of Tilapia. However, Hulon and Williams (1982) found that numbers of Tilapia aurea increased at a rate of 400-500%/year in a Florida lake with largemouth bass, some of trophy size. Also, Shafland and Pestrak (1983) reviewed data showing suppression of production of largemouth bass in the presence of Tilapia in nature and in controlled trials in ponds. They speculated that behavioral

interactions between Tilapia and largemouth bass, rather than direct competition for spawning sites, caused sufficient "harassment" of bass to suppress production of young. The review of interactions between Tilapia and other aquatic species offered by Taylor et al. (1984) suggests that impacts are most likely to be associated with displacement or harassment of

native species when Tilapia reach high densities. The broad

31 flexibility in diets of cichlids also was cited as a probable avenue for impact on native fish. Movements And Residence In Streams The review by Grabowski et al. (1984) notes that Tilapia have successfully colonized a broad range of habitats, including flowing waters. They are abundant in the irrigation canals and agricultural drains near Yuma, Arizona and in the irrigation systems of southern California. Temperature is probably the most important variable in the distribution of Tilapia in streams just as in lakes and reservoirs. Although Tilapia are common in Alamo Lake, Arizona, they have not been found in the streams above the lake. The temperature and irregularity of flow in these feeder streams may limit distribution of Tilapia (Bill Kepner, Environmental Protection Agency, pers. comm.). Also, Tilarda were not taken in the Agua Fria River above Lake Pleasant, but the species is still relatively rare in the lake. The morphology of Tilapia probably restricts it to relatively low flow areas within swiftly flowing waterways. TRIPLOID GRASS CARP

The U.S. Bureau of Reclamation (1990) compiled a

comprehensive review of literature on the life history and environmental requirements of diploid and triploid grass carp. I found no new works that offered additional pertinent information. Materials from the Bureau review that pertain to transfer of fish to the Gila River system are highlighted below.

32 Temperature, Dissolved Oxygen, Salinity Grass carp can tolerate a broad range of environmental conditions. They can occupy waters from 0 to >32 C, with oxygen < 1 mg/liter and salinity up to 10-14 ppt.

Foods and Feeding Adults

There are contradictions in the literature on preferred plants. In general, the more tender, succulent plants are highly preferred by all ages, although larger fish will consume "tougher" plants. Plants not preferred include filamentous algae, Eichhorina, Pharagmites, Carex, Juncus, Valisneria and Myriophyllum. In closed settings without vegetation to feed on, grass carp have taken small fish, cladocerans, tubifex worms, sowbugs and other invertebrates. Young grass carp (weighing 2 to 5 lbs) may consume materials equivalent to several times their body weight each day and large fish may still consume their body weight in foods each day. Their maximum weight is over 100 lbs, with some fish reported to be over 400 lbs. Fish in the southern U.S. attain 8-10 lbs in 1-2 years. Larvae and Juveniles

Larvae begin feeding on small plankton, primarily rotifers and algae, and shift to larger items such as cladocerans. Fingerlings (about 5 cm) begin feeding on aquatic vegetation, and vegetation soon becomes the bulk of the diet.

33 Interactions With Other Fish Species Small grass carp may compete with the young of other species for plankton prey, however, this feeding stage is brief in grass carp. Also, only large fish will be present in irrigation canals. The impacts of larger grass carp normally are associated with high levels of removal of vegetation, leading to reduced cover, feeding and spawning habitat for other fish. Movements in Streams and Canals The native range of grass carp is the low-gradient reaches of the larger rivers of eastern China and the U.S.S.R. It is a large fish that occupies large water. Presumably it is a powerful swimmer in order to negotiate through such waters. In the All American and Coachella Canals of California, grass carp were reluctant to move upstream through check structures or turbulent water drops. Frequent water level fluctuations in canals appear to increase downstream movement.

Potential For Reproduction in Triploid Fish Contrary to early expectations, triploid grass carp develop gonadal tissue and may produce gametes. However, laboratory work with these materials (see BR review) indicates that few of these gametes produce fertile eggs, even when mixed with normal (2 N) gametes, and the few embryos that were produced were inviable.

This report concluded that triploid fish would be "functionally sterile", especially under field conditions. However, the report noted that the ploidy and fertility of eggs from 3N females still

34 need to be studied to increase confidence that triploid fish are

"functionally sterile".

RAINBOW SMELT A review of literature on the life history and environmental requirements of rainbow smelt was prepared by the Utah Department of Natural Resources (Gustaveson et al. 1990) as part of an assessment of the potential impact of introducing the species to Lake Powell. This document, and an informative review of it by Elrod et al. (1990), cover nearly all of the important works on rainbow smelt. Materials from these reports and from several other articles that pertain to concerns of transfer of fish to the Gila River system are highlighted below. Rainbow smelt are a slender, laterally compressed, silver fish. They average 178-203 mm (7-8 in), but may be smaller in small, landlocked lakes or larger in large bodies like the Great Lakes. They typically are anadromous, but are native to some landlocked waters in New England and eastern Canada, and have been introduced to other inland lakes. In inland waters, they may ascend streams in early spring to spawn (MacCrimmon et al. 1983) or spawn along gravel shoals in some lakes. Spawning has occurred in waters ranging from 2-18.3 C. Eggs adhere to substrates and develop in 10-60 days, depending on temperature. Young hatched from eggs laid in streams move downstream and grow

in lakes or coastal zones.

35 Temperature Smelt are schooling, pelagic fish that live in cool, midwater areas near or below the thermocline of lakes. Preferred summer temperatures range from 6-16 C. Rainbow smelt avoid water >15 C and are unable to survive water >23-26 C (Tin and Jude 1983, Elrod et al. 1990). Foods and Feeding Rainbow smelt feed primarily on deepwater invertebrates such as copepods, cladocerans, amphipods, mysids and insects. Prey may be taken from the water column or from the bottom (Evans and Loftus 1987). Gustaveson et al. (1990) suggested that there is no evidence that smelt are an important predator on fish, but

Evans and Loftus (1987) and Elrod et al. (1990) suggest that they show more piscivory, mostly on larval fish, than reported by others. The preference of smelt for larger zooplankton may alter the structure of plankton communities in lakes. Interaction With Other Fish Species The review by Evans and Loftus (1987) on rainbow smelt in the Great Lakes region concludes that the species most affected by the introduction of smelt are cold- or cool-water fish that occupy a niche similar to that of juvenile or adult smelt. Some fish have undergone increased growth after introduction of smelt, but recruitment fell in lake whitefish, juvenile lake trout and walleye after introduction of smelt.

36 Movement and Residence In Streams

Gustaveson et al. (1990) concluded that rainbow smelt do not inhabit streams or rivers except during spawning runs. Also, they reported that the species rarely ascends more than about a quarter mile in streams during spawning, and are usually stopped at sites where water falls >1 ft. However, Elrod et al. (1990) noted that rainbow smelt in Lake Huron run 3.5 miles upstream to spawn, and smelt in Lake Ontario reportedly traversed two fish ladders and moved about 7 miles up the Black River in New York. Smelt in reservoirs on the Missouri River pass through the dams and are found in tailwaters (Gustaveson et al. 1990). However, these fish have not established reproducing populations in tailwaters.

37 ASSESSMENT OF POTENTIAL FOR TRANSPORT AND REPRODUCTION The probability that non-native fish from irrigation canals will be introduced into natural waters is a product of the probabilities of several other conditions, including: 1. the presence of fish in canal water, 2. "spillage" of canal water to a natural drainage (e.g., Gila River),

3. presence of water in the natural drainage, 4. suitable quality of water in the natural drainage,

5. continuity of water between the site of escape and the site of concern. These issues will be addressed in the assessment of the likelihood of fish transfer. Also, the "success" of introduction of non-native fish might fall into at least three levels: 1. Only a few individual fish are introduced during infrequent events, reproduction is precluded, and the probability and duration of survival of these individuals is

small, 2. Fish are introduced regularly, reproduction is precluded, but populations grow due to survival and

continuous recruitment from canal waters, 3. Introduced fish survive and reproduce (i.e., become "established") in receiving waters. Non-native fish may reach waters with threatened and endangered species (e.g., Aravaipa Creek) by: 1) moving from any of the potential sites of release (noted above) to the base of

38 Ashurst-Hayden Dam, pass the dam to the Gila River above, move up 37 miles in the Gila River to the mouth of the San Pedro River, and then ascend the San Pedro to its tributaries (about 12 miles to Aravaipa Creek), all during a single storm event, or 2) reaching the Gila River above the Ashurst-Hayden Dam and surviving there over sufficiently long periods (months to years) so that movements to the tributaries of the San Pedro may be possible during any of several periods of water interconnection, interconnections that need not entail flood flows per se. The second scenario, where resident (but not necessarily reproducing) populations of non-native fish occur in the Gila River and thereby render the river a "reservoir" of exotic species not currently present, seems so much more likely to occur than the first scenario that only the second will be treated. STRIPED BASS

Presence and Survival in Canals Striped bass currently occur throughout the CAP Aqueduct

(Mueller 1990), but no adult fish have been collected below Reach 1 of the Hayden-Rhodes Aqueduct. Few adult striped bass occur in a large California canal, the Coachella Canal, which carries water diverted from the Colorado River near Yuma, Arizona (Rich Thiery, Coachella Valley Water District, pers. comm.) Also, the abundance of all fish in the CAP Aqueduct, including striped bass, has dropped sharply as the volume of water transported has increased and lentic-like conditions have been lost. Mueller (1990) suggests that warming of canal water above 26 C may

39 account for the absence of large striped bass in lower sections of the Aqueduct, and that densities and biomass of fish are likely to continue to decrease as rates of water transport increase. However, the high thermal tolerance of young striped bass (up to 35 C) makes all canal waters potential zones of survival. Furthermore, as noted by Mueller (1990), releases of cool water from the hypolimnion of Lake Pleasant may enhance the survival and abundance of striped bass downstream. There is insufficient data and experience to predict the numbers of striped bass that will occur in the CAP in the future, but the swiftly flowing water and limited forage base of the aqueduct make it far from optimal habitat for survival and proliferation of the species. It is clear that at least some individuals, especially early life history stages, will continue to occur throughout the CAP and the canal systems receiving CAP water. As these fish grow, they will become increasingly susceptible to thermal stress and mortality. Young striped bass that reach Picacho Reservoir probably will be able to survive and grow there in most years. Anoxic conditions that occur during occasional reservoir draw-downs will cause high mortality. As striped bass grow, they will become more susceptible to thermal stress and mortality when Picacho reaches its warmest temperatures. Reproduction of striped bass is extremely unlikely to occur in Picacho Reservoir, but numbers of fish are likely to increase through recruitment from canals. The presence of striped bass in Picacho Reservoir probably will

40 not greatly alter the probability of fish transport in canal waters, but will increase the probability of transport by anglers. Transfer To The Gila River Water released from SCIDD and GRIC Canals

The regular release of water to the Gila River bed at the

Olberg trash racks ensures that some striped bass will be released regularly. The more irregular spillage of water from the two SCIDD wasteways within 6 miles of Ashurst-Hayden Dam and from failure of canals near the Gila River will increase the chances that striped bass will be present in the river bed when there also is sufficient surface water to permit movement to the dam. Data are inadequate to predict the number of striped bass likely to move above the dam in any given opportunity for passage, but the relative rarity of large striped bass in CAP waters should result in low numbers of fish successfully moving above the dam. The presence of "sumps" (essentially long narrow ponds) along the Gila River Indian Community canal system does not seem to contribute much to the probability of transport of striped bass in water releases beyond the threat posed by canal releases or failure alone. Reproduction of striped bass in the lateral canals and sumps is extremely unlikely. Even survival of striped bass in sumps is less likely than in the CAP Aqueduct because water temperatures will certainly be higher in the lateral canals

and sumps. Since larger fish, especially fish >100 mm (>about 4

41 inches) are more sensitive to thermal stress, primarily small fish are likely to survive summer conditions in sumps. All of the sumps on the Gila River Indian Reservation are outside of the 100-year flood plain. The probability that water in sumps will be diverted to the river probably is less likely than diversion of water from canals due to storm flows. The structure and location of the large sump at the terminus of the Santa Rosa Canal make it even less likely to fail than smaller sumps off of GRIC canals.

Water Released From Lake Pleasant. From The CAP/SRP Interconnection and SRP Canals

The release of water from Lake Pleasant to the Agua Fria

River will be no more likely after completion of the CAP system than before the project. Releases will coincide with storms of about a 25-year recurrence interval. The rarity of such releases, the much greater distances fish would have to travel to reach Ashurst-Hayden Dam and the harsh water conditions (e.g., high velocity and suspended particles) likely to be encountered at the intersection of the Agua Fria, Salt, and Gila Rivers during storm flows make this avenue of fish transport far less likely than the scenarios of release from the GRIC. The opportunity for fish released into the Salt River to reach Ashurst-Hayden Dam seems comparable to the scenario for fish released from Lake Pleasant, assuming that water release from SRP canals is about a 25-year event. Even if releases are more frequent, the great distances fish would have to travel make

42 this avenue of fish transfer far less likely than for release from the Gila River Indian Community area. Survival And Reproduction In The Gila River Above Ashurst-Hayden A review of the environmental and biological conditions associated with reproducing populations of striped bass suggests that their succesful reproduction in the Gila River between San Carlos Reservoir and the Ashurst-Hayden Dam is very unlikely because: 1. irregular flows may allow eggs and larvae to settle out with abundant fine sediment before sufficient development or be swept out of the reach and into SCIDD canals or over Ashurst- Hayden Dam before sufficient development (average travel time for water from Coolidge Dam to Ashurst-Hayden Dam is 36 to 48 hours); 2. high seasonal water temperatures and periods of low flow will stress adult fish and lead to occassional die-offs; 3. the lack of a large reservoir precludes development of an abundant plankton forage base for young fish or an abundant clupeid forage fish base for older fish. Kepner et al. (1983) found that the Gila River between Coolidge Dam and Ashurst-Hayden Dam supports low diversity and numbers of fish and invertebrates. They concluded that long periods of continuous high flows during the irrigation season and high levels of suspended sediments (especially below the confluence of the San Pedro River) result in reduced habitat diversity, scouring of the bottom and deposition of fine sediments in the river. These conditions limit primary and

43 secondary production over much of the year, and will limit the opportunities for reproduction and the numbers of striped bass that could be supported. However, some striped bass that reach the Gila River above Ashurst-Hayden Dam probably will survive there, even if reproduction normally is not possible. Water released from the hypolimnion of San Carlos Lake will result in suitable temperatures for survival over part or all of the

warmest months. Temperatures from the USGS station at Kelvin (19 miles above Ashurst-Hayden Dam) seldom have exceeded 25 C and surface water is present all year at this site. Young striped bass will be better equipped than adults to tolerate warmer temperatures that occur during periods of low flow and to make use of a broader array of invertebrate and vertebrate forage items. Numbers of striped bass would grow primarily through

"recruitment" from movement of fish past Ashurst-Hayden Dam, a process unable to be quantified but certainly far more limited than potential recruitment to populations able to undergo regular successful spawning. As fish grow, they will become more

susceptible to forces of mortality due to high temperatures, low flows, and low levels of appropriate forage. Low levels of recruitment and early mortality due to poor habitat and forage availability would keep numbers of resident fish at low levels. Movement, Survival and Reproduction In The San Pedro River and Its Tributaries Successful reproduction of striped bass in the San Pedro River is more remote than in the Gila River because water flows

44 are even more irregular and temperaturers are frequently several degrees warmer (sometimes exceeding 31 C; USGS station near Mammoth). However, physical water conditions are frequently within the tolerable range for striped bass, so that survival is possible even if reproduction is not. However, high levels of sediment, low levels of forage and a scarcity of cover work against survival of striped bass.

There generally are two periods when there is continuity of water flow from the Gila River to the San Pedro River and on to Aravaipa Creek, during summer monsoon rains and during winter frontal storms. The duration of continuity of flow is shorter in the summer (hours to days) than in the winter (days to weeks), and water temperatures are probably farther from preferred values in the summer than in the winter. Thus, movement of striped bass would be more likely in winter.

There is some evidence of young striped bass moving into streams outside of the spawning season, but all of these observations involve waters much larger than the San Pedro River

(or any of its tributaries) and often involve use of cool streams by reservoir fish as thermal refuges in summer. There are no data to suggest that striped bass have or will select for conditions likely to occur in the San Pedro River. However, the occassional movement of a striped bass, especially a young (small) fish, into the San Pedro and its tributaries during the period when water quality is within the tolerable range cannot be precluded, especially over the life of the CAP.

45 WHITE BASS Presence and Survival in Canals White bass do not currently occur in the CAP canal, but Mueller (1990) predicts that they will be entrained from Lake Pleasant and transferred wherever CAP water flows. White bass are more tolerant than striped bass to high temperatures and low oxygen, so they are at least as likely to be able to persist in the CAP Aqueduct, and more likely to survive in lateral canals and sumps and in Picacho Reservoir. White bass are recovered from irrigation canals along the Pecos River in New Mexico when the canals are drained for maintenance. The number of fish entrained from Lake Pleasant and likely to occur in canals in Arizona cannot be predicted yet. However, the vertical distribution of oxygen in Lake Pleasant may limit the opportunities for entrainment of white bass. Morgensen (1990) reported that a thermocline forms in May in Lake Pleasant at about 8 m deep. There is virtually no oxygen in the water below the thermocline during stratification (May - October). Water releassed from the lake and diverted to the CAP Aqueduct will be withdrawn from well below the thermocline, so is not likely to carry many fish when the lake is stratified (if anoxia still occurs). As with striped bass, white bass probably will survive and grow in Picacho Reservoir, but not reproduce. Their presence in the reservoir is more likely to increase chances of fish transport by anglers than by movement through associated canals.

46 Transfer to the Gila River

The scenarios for transfer of striped bass (outlined above) are much the same for white bass. The most probable sites for transfer of white bass are in the area near Ashurst-Hayden Dam. The irregularity of releases from Lake Pleasant and the distances fish must travel from the Santa Cruz River, Lake Pleasant or the SRP canals to Ashurst-Hayden Dam make the potential for transfer of fish from these sites extremely small relative to the sites near the dam. At least one storm event in most years will offer access to the Gila River above the dam. The frequency of fish transfer during these opportunities cannot be predicted, but is likely to occur eventually. Survival and Reproduction in the Gila River above Ashurst-Hayden Data on the combination of environmental conditions that permit successful reproduction in the Southwest are not well understood. Grabowski et al. (1984) note that attempts to establish white bass in the lower Colorado River and at some sites in New Mexico have failed for unknown reasons. The review by Grabowski et al. (1984) of successful introductions in the Southwest and comments I received from biologists in New Mexico indicate that all reproducing populations in the Southwest are associated with moderate to large-sized reservoirs with inflowing streams. Although there is growing evidence of extensive movements of white bass in perrenial streams connected to reservoirs, there is no evidence that the species could sustain

47 itself in streams alone, without resident populations in adjacent reservoirs. White bass would seem to be more likely to be capable of reproducing in the Gila River than are striped bass because the eggs of white bass are adhesive and develop while attached to substrates. Eggs would not be as readily swept from the river as would eggs of striped bass. Also, the broader temperature tolerance and highly flexible diet of white bass should make them more likely to survive in the Gila River. However, virtually all of the field evidence for Southwestern waters suggests that the lack of a large reservoir on the Gila River will preclude successful establishment of a self-sustaining population of white bass. As with striped bass, some white bass that reach the Gila River above Ashurst-Hayden Dam probably will survive, even if reproduction is not possible. Numbers of white bass could grow through "recruitment" from movement of fish past Ashurst-Hayden Dam, an event of much lower frequency than "natural recruitment".

The broader tolerances and more flexible diet of white bass should give them an advantage for survival over striped bass. However, they are not likely to fare better than the fish currently found in the middle Gila River. The poor conditions of habitat and forage would limit the numbers of white bass that could be supported,.

48 Movement, Survival, and Reproduction in the San Pedro River and its Tributaries Successful reproduction of white bass in the San Pedro River is more remote than in the Gila River because water flows are relatively small and irregular and appropriate substrate for attachment and development of eggs is scarce. Again, the lack of a reservoir and its associated forage base also make establishment of a self-sustaining population unlikely. However, water conditions are frequently within the tolerable range for white bass, so that survival is possible even if reproduction does not occur.

There is some evidence of young white bass using stream environments in the Southwest during all or part of the year, not just during spawning. However, all of these observations involve waters larger and with more consistent flow than the San Pedro River or its tributaries. There are no data to suggest that white bass have or will select for conditions likely to occur in the San Pedro River. For example, white bass apparently do not move into the Aqua Fria River above Lake Pleasant or into the Black River, a small tributary of the Pecos River, New Mexico. However, the occasional movement of white bass, especially a young fish, into the San Pedro and its tributaries when water quality is within the tolerable range cannot be precluded, especially over the life of the CAP.

49 BLUE TILAPIA Presence And Survival In Canals Blue tilapia do not currently occur in the CAP Aqueduct. Their presence in Lake Pleasant and in SRP canals and their apparent spread in the Salt River system below Saguaro Lake make their introduction to the aqueduct likely in the future. The broad environmental tolerances and flexible diet of Tilapia ensure that they will be able to survive in the CAP. They are sensitive to cold; mortality usually begins below 10 C and the reported lower lethal limit is between 6-10 C. The lowest temperature in the CAP reported by Mueller (1990) was 9.1 C. Temperatures may get lower in some lateral canals, but some fish will persist in sumps or areas offering "thermal refuge". Grabowski et al. (1984) summarized numerous reports of Tilapia in irrigation canals and agricultural drains. However, not all canals offer quality environments that support large populations. For example, Mueller et al. (1989) found that Tilapia were rare or absent in sampled reaches of the Coachella Canal, California

(earthen and concrete-lined canals) even though Tilapia were stocked at one time and continually enter the system with Colorado River water. Grabowski et al. (1984) noted that Tilapia might be able to reproduce in canals if they could find quiet water areas for spawning. Although T. aurea are mouthbrooders, they select substrates similar to those used by many centrarchids over which to spawn. The evidence of spawning by carp, largemouth bass and bluegill in the CAP (Mueller 1990) suggests

50 that Tilapia also would find some areas suitable for spawning (primarily in forebays of pumping plants). These areas and areas suitable for survival and growth of young will be at a minimum when water velocities reach their peak with full operation of the CAP. Thus, Tilapia may not reach high densities in the CAP, but probably will be present throughout much of the system. Habitat for survival and reproduction of Tilapia is more likely to occur in lateral canal systems receiving CAP water than in the CAP. Lateral canal systems offer lower water velocities and more areas of protection. Earthen sumps along the GRIC system support populations of warm water fish, and will support Tilapia. Tilapia will suffer heavy mortality during some cold periods and during annual dewatering of canals (late October to early December), but will persist in sites of perennial water and will be introduced continually from the CAP.

Tilapia were once abundant in Picacho Reservoir (Jakle and Baucom 1983) and will surely proliferate if introduced again.

Movement of Tilapia out of Picacho Reservoir may increase the occurrence of fish in canals and thereby increase the chances for transport with spillage of water.

Transfer To The Gila River The scenarios for transfer of striped bass (outlined above) are much the same for Tilapia. The most probable sites for transfer are near the Ashurst-Hayden Dam. Fish that are released from Lake Pleasant or from SRP canals are even less likely than

51 striped bass or white bass from these sites to be able to reach the base of Ashurst-Hayden Dam. Tilapia probably are less capable of traversing the dam than are striped or white bass, but eventually they could reach the river above the dam.

Survival And Reproduction In The Gila River Above Ashurst-Hayden Water temperatures recorded at the USGS gage at Kelvin, Arizona (19 miles above Ashurst-Hayden Dam) fall below 10 C in most years and should result in some winter mortality of Tilapia. However, water temperature is tolerable over most of the year and probably exceeds 22 C long enough to permit successful reproduction.

Tilapia are capable of feeding on invertebrates, aquatic vegetation or detritus so they are more likely to find forage than many other fish species. However, benthic scour during long periods of continuous high flow during the irrigation season reduce even these foods (Kepner et al. 1983). The high flows also limit quiet water areas needed by Tilapia. These conditions and occasional winter mortality probably will keep numbers of

Tilapia low even if successful reproduction can occur. Movement, Survival And Reproduction In The San Pedro River And Its Tributaries Water temperature in the San Pedro River is appropriate for reproduction over part of the year. Low temperatures are likely to cause mortality in some winters. The exceptional levels of fine sediment in the river (Kepner et al. 1983) will limit

52 available forage and cover. These conditions will limit the numbers of Tilapia even if reproduction occurs. Although there generally are periods of continuous flow from

Aravaipa Creek to the San Pedro River in the summer and the winter, cool winter flows probably are less conducive to upstream movement of Tilapia. Periods of water connection are shorter in the summer but eventually may result in the introduction of

Tilapia to Aravaipa Creek, despite the expected rarity of Tilapia in the San Pedro River. However, Tilapia from Alamo Lake in western Arizona do not ascend or reside in the feeder streams to the reservoir. Winter temperatures in Aravaipa Creek, especially at the lower end, can fall below 5 C, but such low temperatures are not maintained for more than several hours (Minckley 1981). This would be lethal to some but not all Tilapia, Temperatures <8C must be sustained for 2-3 days or more for complete mortality.

Summer temperatures would be tolerable and might permit reproduction. However, the areas where Tilapia tend to become abundant (e.g., the lower Colorado River and irrrigation systems near Yuma) are warmer and have more low velocity water than Aravaipa Creek. Short periods of flood flow seem to have far more impact in reducing non-native than native fish (Minckley

1981). Tilapia should be at least as susceptible to losses due to storm flows as are the non-native fish currently found in

Aravaipa Creek. Because of these conditions, it is unlikely that

Tilapia will be abundant in Aravaipa Creek. However, it is

53 likely that some Tilapia occassionally will occur in the creek once they are found in the Gila and San Pedro Rivers. TRIPLOID GRASS CARP

Presence And Survival In Canals Grass carp should be able to easily tolerate conditions in the CAP Aqueduct. These fish will not be transported out of the CAP and throughout the canal system because of bar screens placed in the CAP aqueduct. Fish would be released only by failure or overflow of these large canals during extraordinary storm events. Transfer To The Gila River Fish would have to be transported directly from the CAP aqueduct to the Gila River, since grass carp will not occur in the lateral canals discussed above for other fish species. I have no data on the probability of such an event. However, a storm event severe enough to breach or overflow the CAP Aqueduct and carry grass carp to the Gila River would probably create flow conditions in the Gila River unlikely to readily permit upstream movement of grass carp.

Survival in the Gila River Above Ashurst-Hayden

Grass carp that reach the Gila River above Ashurst-Hayden will find water quality within their tolerances. At times of the year, aquatic vegetation will be scarce, but some foods will be available. Only relatively large fish could be present, and the rarity of release from canals should result in the presence of few fish. If fish are introduced, they may survive for some years because the species is long lived.

54 Movement And Survival In The San Pedro River

And Its Tributaries Water temperature and other water quality conditions in the San Pedro River normally would be tolerable to grass carp, but the high levels of fine sediment and irregular flows would limit available forage and cover. Also, the grass carp is a large species that normally inhabits large, low gradient rivers and would not be expected to readily enter shallow, low volume streams like the San Pedro River or its tributaries. Their size and swimming ability might allow them to ascend the San Pedro during storm flows, but the poor water quality likely to occur during storm events probably would discourage such movements. The low number of grass carp ever likely to be residing in the Gila River and the inappropriateness of conditions in the San Pedro River, make residency and movements of hybrid grass carp in the San Pedro River and its tributaries a very unlikely event. Even if entry were to occur, only a very few fish would likely be involved, greatly limiting the potential for significant damage, especially since reproduction is not an issue.

RAINBOW SMELT

If rainbow smelt are introduced to Lake Powell, they will be carried to downstream reservoirs (Gustaveson et al. 1990, Elrod et al. 1990). Smelt will occur in the CAP Aqueduct if they reach and proliferate in Lake Havasu.

55 Rainbow smelt are more sensitive to warm water temperatures than any of the other species of concern. They avoid water >15 C and will suffer mortality above 23 C. Water in the CAP Aqueduct, the lateral canals and sumps, Picacho Reservoir and in the Gila River and its tributaries exceeds 23 C many days each year. This will restrict survival of rainbow smelt to cool-weather periods each year and generally should preclude survival, growth to sexual maturity and successful reproduction. The lack of a large reservoir on the Gila River with a cool, oxygenated pyholimnion and an abundant plankton community also works against the survival and reproduction of smelt.

Rainbow smelt that reach the Gila River system during cool periods may compete with other fish for plankton and benthic invertebrates. However, the small size and low number of smelt likely to be present and the limitedperiod of survival will reduce the potential for smelt to pose a significant threat to aquatic species in the Gila River system, including fishes in Aravaipa Creek.

56 POTENTIAL IMPACTS ON FISH OF ARAVAIPA CREEK

Aravaipa Creek is not the only tributary of the San Pedro River with native fish, but has a uniquely diverse fauna, including two fish listed federally as threatened species (spikedace and loach minnow) and one fish listed by the State as threatened in Arizona (roundtail chub). Also, Aravaipa Creek is the closest drainage to the confluence of the San Pedro and Gila

Rivers; Redfield Canyon, Hotsprings Creek and the upper San Pedro River are progressively more distant and protected more frequently from invasion by non-native fish due to dry reaches of stream bed in the San Pedro River and the tributaries. STRIPED BASS

The potential impact of striped bass on the fauna of Aravaipa Creek of most concern involves predation on invertebrates and native fish. Striped bass are highly predaceous and shift to fish prey early in life. Data on the life history of striped bass and experience with the species in the Southwest suggest that they do not move into nor occupy waters as small and irregular in flow as the San Pedro River or

Aravaipa Creek. Thus, movement into Aravaipa Creek probably would be a relatively rare event, if it occurred at all, and likely would involve a low number of young individuals that would not mature and reproduce in the creek. The impact of a rare introduction of a "few" (<5) small striped bass may not be much greater than the impact of non-native predatory fish already known to occur occassionally or regularly in the creek (e.g.,

57 green sunfish, largemouth bass, yellow bullhead, mosquitofish). However, at a minimum, careful monitoring of fish movement into the San Pedro River and Aravaipa Creek should be conducted to verify the presence or absence of striped bass and their longevity. Over many years of observation, Minckley has found a strong positive relation between increased water flows from Aravaipa Creek and increased incidence of non-native fishes (W. L. Minckley, Dept. of Zoology, Arizona State University, pers. comm.). Changes in watershed management and decreases in groundwater use in the Aravaipa and San Pedro River areas may increase stream flows sufficiently to increase the probability of fish introduction and damage from a variety of non-native fishes. WHITE BASS Most of the discussion above, for striped bass, also holds for white bass. Field data suggest that white bass occur in some stream environments but not in systems as small as the San Pedro

River or Aravaipa Creek. White bass potentially could impact fauna through predation, but their probability of occurrence, of reaching significant abundance, and of surviving for long periods in Aravaipa Creek is low. A commitment to systematic monitoring should be made to verify these predictions.

BLUE TILAPIA Tilapia are more likely to impact native fish through negative behavioral interactions (e.g., harassment or occupation of spawning areas) associated with high numbers of fish rather than through predation (Taylor et al. 1984). Tilapia probably

58 will survive and breed in the Gila and San Pedro Rivers, but are not likely to achieve the abundance they exhibit in warm, quiet, highly productive waters. The occurrence of Tilapia in Aravaipa Creek is quite possible in the future, but they are not likely to grow to large numbers due to cold temperatures and high water velocities. This should limit their potential for harm to the native fauna.

TRIPLOID GRASS CARP It is highly unlikely that carp of the size that occur in the CAP Aqueduct would voluntarily move into and reside in a small stream like Aravaipa Creek. If a grass carp reached the creek, it could consume relatively large amounts of aquatic vegetation and some benthic invertebrates, but these impacts probably would be restricted to the deepest waters, the sites most likely occupied by such large fish. Again, grass carp should never be abundant in the Gila River and are less likely to occur in the San Pedro River. The presence of even a single grass carp in Aravaipa Creek would be an exceptional event, and more likely to occur by human transport than by natural movement.

RAINBOW SMELT If rainbow smelt reached Aravaipa Creek, they would probably be able to persist for only a few months at best. The broad fluctuation in water velocity and high summer water temperatures would eliminate smelt. They may compete with native fishes for some benthic invertebrates, and smelt may consume some juvenile fish. However, the low number of smelt likely to be present and

59 the relatively brief period of survival would make smelt less of a threat to native fish than are non-native fish already present in Aravaipa Creek.

POTENTIAL IMPACTS ON FORAGE OF BALD EAGLES A small nesting population of bald eagles (Haliaeetus leucocephalus) occurs in Arizona. An active nesting area has been found on the Gila River downstream from Coolidge Dam (BioSystems 1990). Channel catfish, carp and Sonora and desert suckers are the most common fish prey taken by bald eagles throughout Arizona, and make up a large part of eagle diets. Suckers become vulnerable to predation by eagles during feeding and spawning activities in shallow areas of streams (BioSystems 1990). Carp also become vulnerable when feeding and spawning in shallows, but dead carp also are taken by eagles. The deep water and protected areas used by catfish make them difficult for eagles to catch. Dead or dying catfish provided most of the catfish foraged by eagles (BioSystems 1990).

The introduction of striped bass and white bass into the Gila River is unlikely to result in significant changes to forage available to eagles. Neither fish species is likely to undergo successful reproduction or to sustain large numbers. Some individuals certainly will survive in the Gila River if introduced and will prey on fish species used by eagles.

However, striped and white bass will be exposed to high water temperatures and other environmental conditions likely to cause

60 death or morbidity and resultant vulnerability to predation by eagles. Thus, loss of potential eagle forage to white white and striped bass may be balanced by the addition of both species to the forage base.

Tilapia are likely to reproduce and proliferate in the Gila River, but should be highly vulnerable to predation in shallow waters and when cold temperatures reduce their activity or cause death. Tilapia are not known to exclude carp or catfish from aquatic systems, and are not likely to be better able than Sonora or desert suckers to deal with the fluctuating flows of the Gila River below San Carlos Reservoir.

Triploid grass carp probably will not significantly impact eagle forage because of the very low probability of introduction, the low number of individuals likely to be present if introduction occurs, and the probable inability of triploid grass carp to reproduce. Grass carp in shallow water may be vulnerable to predation by eagles.

Rainbow smelt will not find suitable environments year-round in the Gila River. Thus, they would only occur in low number and would survive for relatively short periods if introduced. These conditions would preclude a significant impact on eagle forage.

61 RECOMMENDATIONS The greatest danger of non-native fish arises when the introduction of only a few individuals is likely to lead to the establishment of a self-sustaining population capable of significant harm to native organisms. Among the fishes of concern in this report, only Tilapia are likely to establish self-sustaining populations. However, even if they become established in the Gila River, it is not clear that they will cause significant harm to native fish. All of the other species of concern are not likely to establish self-sustaining populations in the Gila River even if introduced repeatedly. This raises the issue of whether new efforts to block the transport of fish should be made and whether current efforts should be maintained. Current efforts to block transport of fish (i.e., bar screens for grass carp and electric fish barriers for all other species) are probably not adequate to preclude eventual transport of fish in spilled irrigation waters and storm flows to the Gila River drainage below Ashurst-Hayden Dam, but they do reduce the probability of large numbers of fish moving into the river above the dam. White bass and striped bass could have little impact if they occur in low numbers, and they would become abundant in the Gila River only if large numbers of fish are able to pass into the river above the dam and survive there. The routes of fish transport, other than through the Florence-Casa Grande Canal (protected by an electric fish barrier near China Wash), are sufficiently rigorous to limit the number of fish

62 likely to be introduced. Thus, the barrier limits the potential for impact. The probability of triploid grass carp escaping to the Gila River and becoming numerous enough to cause significant damage seems remote. Current measures to block escape of grass carp from the CAP Aqueduct are probably adequate. The environmental requirements of rainbow smelt will probably block reproduction and limit their survival in the Gila River if they are introduced. Current efforts to block fish transport will reduce the chances for introduction of smelt and therefor reduce the chances for harm even though they are not likely to persist for long or in large numbers in the river.

In summary: 1. The China Wash fish barrier hinders the introduction of non-native fish, and although it may prove to be inadequate to indefinitely prevent introductions, its ability to reduce the frequency of introduction for some species is of value. The barrier should be inspected and tested periodically to ensure its effectiveness.

2. The electric fish barrier in the Pima Lateral Canal appears to serve no significant function now that CAP water is delivered to the Florence-Casa Grande Canal.

3. Regular monitoring for the presence and abundance of the fish species of concern in the Gila and San Pedro Rivers should be conducted in order to verify or modify the predictions made in this report.

4. The presence of fish in the CAP Aqueduct increases the proximity of non-native fish to sensitive waters, but there probably is no barrier to fish movement that will preclude transport of fish by humans. A program of public education and awareness of the dangers and illegality of fish transport may reduce the incidence of transport of fish by humans, but is unlikely to be completely effective.

5. The release of water and fish to the Gila River drainage below Ashurst-Hayden Dam provides an avenue for fish to enter the Gila River above the dam. The special hydrologic circumstances necessary for this avenue to be available and

63 the rigors of the trip will limit the numbers of fish able to pass in any given opportunity. This avenue could be blocked by: I. structural changes to Ashurst-Hayden Dam that would make it a more effective barrier to fish movement, 2. cessation of release of water to the Gila River drainage below the dam, or 3. cessation of delivery of CAP water to water users near the Gila River drainage. All of these actions bear significant "costs" that are probably not commensurate with the levels of probable harm attributable to the introduction of the fish species of concern. Implementation of any of the three alternatives will not preclude introduction of these non-native fish to the Gila River by other means, especially by human transport.

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67 Mallin, M. A. 1986. The feeding ecology of the blue tilapia (Tilapia aurea) in a North Carolina reservoir USA. Pages 323-326 in Redfield, G., J. F. Taggart, and L. M. Moore. Proc. of Fifth Annual Conference and International Symposium on Applied Lake and Watershed Management, Lake Geneva, Wisconsin, USA, November 13-16, 1985. North American Lake Management Society, Washington, D.C. Marsh, P. C., and W. L. Minckley. 1982. Fishes of the Phoenix metropolitan area in central Arizona. North American Journal of Fisheries Management 4:395-402.

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66 TAKE• PRIDE IN United States Department of the Interior AMERICA BUREAU OF RECLAMATION ARIZONA PROJECTS OFFICE 23636 N. 7TH STREET P.O. BOX 9980 IN ma REFER TO: PHOENIX, ARIZONA 85068 APO-150 ENV-4.00 DEC. 1 7 199l 90011020 4319

Memorandum

To: Interested Agencies and Individuals

From: Chief, Environmental Division

Subject: Review of the Draft Report "Potential for Transfer of Nonnative Fish in Central Arizona Project Canal Waters to the Gila River System" (Due Date January 7, 1991) (Fish and Wildlife)

Enclosed for your review is a copy of the subject report. This report has iled to assess the question concerning the effects of rans ish into the Gila River system and was prepared Dr. William J. ool of Renewable Resources, University of Arizon Tucson, Arizon fer may be brought about by the operation of the Central Arizona ect (CAP). We expect to use this report as the basis for a biological assessment which will be completed to assess possible impacts to endangered species.

This report has been conducted under a condensed schedule because of the need for CAP water by the farmers in the San Carlos Irrigation Project. These farmers may need irrigation water as early as March 1991, depending on the crops grown. If the present drought continues, they will need water to irrigate their land. Therefore, a timely decision to deliver CAP water to them is needed.

Based on the urgency of this project, we will need your review comments no later than January 7, 1991. If we have not received yo c s by this date we will assume you have no comments. Please di ct your com nts to Mr. Marty Jakle at the above address or Fax number 02-870-6753. V appreciate your cooperation in this review. If y need any addit' nal information, please contact Mr. Jakle at 602-870 6764.

Enclosure ARIZONA STATE UNIVERSITY

Department of Zoology Tempe, Arizona 85287-1501 ( 602) 965-6518 7 January 1991

Mr. Bruce D. Ellis Ref. APO-150 ENV-4.00 U.S. Bureau of Reclamation 90011020 4319 Arizona Projects Office 23636 North Seventh Street Post Office Box 9980 Phoenix, Arizona 85068

Dear Mr. Ellis;

I have reviewed the draft report 'Potential for Transfer of Nonnative Fish in Central Arizona Project Canal Waters to the Gila River System" and generally concur with its conclusions. It is, however, largely an academic exercise, since most species with which it deals are too laroe to inhabit the relatively tiny waters of concern. I concur that rainbow smelt, a smaller species that has yet to be (and I hope will never) be introduced in the system, would surely find these central Arizona waters too severe to survive. If they do not, we are in deep trouble. I am pleased that the problems of human transfer are so heavily emphasized; they are important. I suggest that even more emphasis might be placed on the probability that humans will in fact, place these fishes in places where their survival will be most likely (e.g., streamside ponds, etc.), and that escapes from fish-farming operations may be more of a threat than introduction from water delivery canals.

Unfortunately, the report does not deal (except in Table 1) with the real threat of interconnected waterways throughout Arizona--that is, the transport of smaller, non-native fishes and of a general homogenation of the fauna, neither of which can be avoided. To the small, isolated, native-fish habitats such as Aravaipa Creek, etc., movements of sunfishes (Lepomis spp.), red shiner (Cyprinella lutrensis; which, by the way is misspelled in Table 1), catfishes, and poeciilids, is far more important that that of larger species. I suggested as early as 1969 (I think) in a small report to the Bureau of Reclamation that your agency consider reviewing the overall potential problem of transport of organisms and their propagules in general, not just fishes, between the Mohave and Sonoran deserts, and into proximity of the Chihuahuan Desert, by the CAP development. The real, long-term problems may be plants and bugs, rather than fishes! Thank you for allowing me to review the document; If I can provide further input, please let me know..

W. L. Minckley Professor of Zoology