ASSESSMENT OF A FORAGE FISH INTRODUCTION INTO LAKE POWELL

Prepared by:

A. Wayne Gustaveson

Henry R. Maddux

and

Bruce L. Bonebrake

Lake Powell Fisheries Project

Utah Department of Natural Resources Division of Wildlife Resources 1596 West North Temple Salt Lake City, Utah 84116

Timothy H. Provan Director

March 1990 TABLE OF CONTENTS

Page

List of Tables ...... vi

List of Figures .....viii

Purpose and Need ...... 1

Description of Affected Environment ...... 2- Location ...... 2 Fishery Resources 4 Threadfin Shad ...... 7 Other Forage Organisms ...... 9 Largemouth Bass 9 Smallmouth Bass 9 Black Crappie 11 Walleye 11 Catfish 12 Threatened and Endangered Species 12 Striped Bass ...... 12 Environmental Components Not Affected 14 Commercial Concerns 14 Recreation ...... 14

Alternatives ...... 15 Introduction ...... 15 Lake Powell Management Objectives 15 Economic Benefits 16 Alternatives Evaluated ...... 16 Proposed Action - Rainbow Smelt Introduction ...... 17 Pygmy Smelt 17 Multi-Species Forage Complex ...... 17 Commercial Fishery ...... 17 Regulation Changes ...... 17 No Action 17

Discussion of Alternatives ...... 18 Rainbow Smelt Introduction ...... 18 Pygmy Smelt 19 Multi-Species Forage Complex ...... 19 Commercial Fishery ...... 20 Regulation Changes ...... 21 No Action 22

Comparative Analysis ...... 23 Selection Standards 23 Alternatives Considered But Dismissed 24 Increasing Reservoir Productivity 24 Stocking Additional Threadfin Shad ...... 24 TABLE OF CONTENTS (Continued)

Page

Introducing Some Form of Sterile Striped Bass 25 Stripercides ...... 25 Limit or Disrupt Spawning 25 Introduce Predator for Striped Bass 25 Create Large Protected Shad Nursery Areas 25 Other Candidate Species Considered But Dismissed ...... 26

Analysis of Environmental Consequences ...... 27 Expected Benefits 27 Lake Powell Productivity and Plankton Abundance 28 Life History and Ecology of Rainbow Smelt 28 Description 28 Distribution ...... 29 Habitat 30 Spawning ...... 30 Food Habits 31 Disease Potential 32 Hybridization 33 Smelt as Forage 33 Expected Behavior of Smelt in Lake Powell 33 Threatened and Endangered Species 35 Humpback Chub 35 Bonytail Chub 37 Razorback Sucker ...... 37 Other Environmental Components ...... 37

Summary and Conclusions ...... 39

Documentation of Consultations ...... 40 Public Meetings 40 Colorado River Fish and Wildlife Council 41 Other Public Meetings 41 Federal Agency Consultation 42

Literature Cited ...... 43

-iv- LIST OF TABLES

Table Page

1. Stocking history of Lake Powell, Utah-Arizona, 1963-86 . 5

2. Alternatives comparison matrix of selection standards . 24

3. Species considered for introduction into Lake Powell . . 26

-vi- LIST OF FIGURES

Figure Page

1. Indices of total recreational boat use and angling pressure Lake Powell, 1965-88 3

2. Mean number of threadfin shad collected per trawl tow July-September, Lake Powell, 1977-89 ...... 8

3. Catch rates (fish/net day) for walleye and largemouth bass during annual trend gillnetting at Lake Powell, 1972-88 10

4. Mean condition factor (Kfl) of adult and juvenile striped bass at Lake Powell, 1975-89 ...... 13

i PURPOSE AND NEED

The purpose of this action is to enhance forage conditions for all fish species currently established in Lake Powell by introducing a deep, cold water planktivorous forage fish, such as rainbow smelt (Osmerus mordax). Once established, rainbow smelt could increase forage species diversity, provide forage for fish occupying the cool water zone, more efficiently utilize plankton in the pelagic zone and expand escape habitat utilized by forage species.

An over population of piscivorous predators resulting from unlimited striped bass (Morone saxatilis) reproduction has placed extreme predatory pressure on threadfin shad (Dorosoma petenense), the only pelagic forage fish present in Lake Powell. The shad population has been impacted by predation to the point that it no longer provides adequate forage for pelagic or deep water predators. The striped bass population has become stunted with few fish attaining a length in excess of 500 mm (20 in). Adult striped bass move into the deep cooler water as they mature. They are not able to successfully compete with juvenile striped bass which forage on the annual shad crop in the warmer shallow water areas. Both walleye (Stizostedion vitreum) and striped bass populations suffer recurring periodic declines in physical condition which is attributable to the separation of predator and prey and the lack of sufficient shad forage. Juvenile and some adult striped bass are having to forage directly on large zooplankton to maintain body condition, indicating an inadequate forage base for a major part of the predator population.

Over the past 25 years, fishing at Lake Powell has been good enough to attract anglers from all over the world. When the reservoir was young and filling, largemouth bass (Micropterus salmoides) and black crappie (Pomoxis nigromaculatus) fishing was outstanding. Angler catch rates in 1979 for largemouth bass and black crappie were 0.22 and 0.16 fish/h; by 1984 catch rates had declined to 0.05 and 0.03 fish/h and by 1988 had declined to 0.04 and 0.00 fish/h, respectively. More recently the fisheries have been dominated by walleye and striped bass. Over the life of the reservoir, anglers have been able to catch a mixed bag of fish at an average rate near 0.4 fish per hour (Scott and Gustaveson 1989). Fishing pressure has steadily increased throughout the life of the reservoir until recently (Figure 1).

The striped bass sport fishery gained wide public recognition from 1979-1985. The fish were large and easy to catch. Many people came to the lake just to fish for striped bass. The average size of sport caught fish harvested between 1979 and 1984 was 620 mm (24.4 in). This was easily the largest fish that the average Lake Powell angler had caught in a lifetime. As striped bass predation depleted shad stocks from the pelagic zone condition of adult striped bass dramatically declined. During 1982-1983 most anglers were happy with their trophies despite their poor physical condition of some fish. During 1985 the average length of all striped bass sampled declined from 620 mm to 555 mm (21.8 in) and condition factor fell to near 0.90. Anglers began to become dissatisfied at this point. By the spring of 1986 striped bass averaged 497 mm (19.5 in). They further declined in size to 423 mm (16.5 in) by the fall of 1986, and 393 mm (15 in) in 1987. During the winter of 1987 a massive die-off eliminated most striped bass between 500-800 mm (20-31 inches) from the population. Total length declined to 348 mm (13.7 in) in 1988 and

-1- rebounded slightly to 355 mm (14 in) in 1989. Smaller striped bass typically have better condition factors (Kfl) than larger fish. Condition is currently averaging near 1.0 to 1.1. A Kfl factor greater than 1.1 is the value where striped bass become acceptable to anglers.

DESCRIPTION OF AFFECTED ENVIRONMENT

LOCATION

Lake Powell was impounded by Glen Canyon Dam on the Colorado River, 9.7 km (6 mi) south of the Utah-Arizona border. The lake's main purpose was water storage and regulation as well as hydroelectric power generation within the Colorado River Storage Project (CRSP). The 300 km-long (186 mi) reservoir is confined to the deep narrow canyon of the Colorado River and its tributaries. Most of the 2,930 km (1,820 mi) of shoreline is comprised of sandstone cliffs and talus slopes. Only a few side bays offer relief from the vertical canyon walls. Average depth of the reservoir is 50.9 m (167 ft) and the maximum capacity is 3.32 x 108 m3 and 160,000 surface acres (Johnson and Merritt 1979).

Lake Powell is an oligotrophic, warm monomictic, canyon reservoir (Johnson and Merritt 1979). Stratification generally begins in April and often persists into December. Surface temperatures range between extremes of 6.7 and 29.4 C. Secchi readings are typically 3-9 m, although readings as high as 13 m have been recorded (unpublished data, Utah Division of Wildlife Resources, Page, AZ).

Lake Powell, within Glen Canyon National Recreation Area, has become a popular tourist attraction with an annual visitation of over 3 million per year. It offers boating, fishing, hiking and associated recreational opportunities.

The regulated Colorado River below Lake Powell flows through Grand Canyon National Park 445 km (277 mi) from Glen Canyon Dam to Lake Mead. Lake Mead, formed by Hoover Dam, supplies most of the storage and regulation in the lower Colorado River Basin, providing for irrigation, municipal and industrial uses, power generation, flood control, and recreation.

Lake Mohave, formed by Davis Dam, backs water about 100 km (67 mi) upstream to Hoover Dam. Storage in Lake Mohave is used for reregulation of releases from Hoover Dam, for meeting treaty requirements with Mexico, and for power generation. The river then flows through a natural channel for about 16 km (10 mi) below Davis Dam at which point the river enters Mohave Valley 53 km (33 mi) above the upper end of Lake Havasu.

Lake Havasu behind Parker Dam impounds 72 km (45 mi) of river and serves as a forebay from which the Metropolitan Water District of Southern California pumps water into the Colorado River Aqueduct. Lake Havasu also serves as forebay for the Central Arizona Project pumping plants and aqueducts. Lake Havasu is used to control floods originating below Davis Dam and above Parker Dam.

-2- 450

400

350

300

0 c 250 CO 0

00 _1= 700 150

100

50

65 67 69 71 73 75 77 79 81 83 85 87 66 68 70 72 74 76 78 80 82 84 86 88

Year

figure 1. indices of total recreational boat use and angling pressure, Lake Powell, 1965-1988. The river then flows 444 km (276 mi) below Davis Dam to the Mexican border. Important structures within this reach include Headgate Rock Dam, Palo Verde Diversion Dam, and Imperial Dam which serve as diversionary structures with practically no storage.

FISHERY RESOURCES

Fisheries investigations have been conducted on Lake Powell since 1963 when the reservoir began filling. Many changes have occurred since then. The first fish stocked were largemouth bass, black crappie, rainbow trout (Oncorhynchus mykiss) and kokanee salmon (Oncorhynchus nerka) (Table 1). The bass and crappie fisheries thrived as the reservoir filled and expanded. The rainbow trout fishery provided excellent fishing near the dam but only fair to poor fishing on a lakewide basis. Trout populations had to be maintained by stocking and the lack of lakewide harvest led to a management decision to discontinue that fishery. The kokanee fisheries were also discontinued soon after stocking for the same reasons.

The need for additional forage to support the sport fisheries was recognized early and resulted in the introduction of threadfin shad in 1968-1969. The introduction was successful and quickly produced positive results (May et al. 1975, Hepworth and Gloss 1976, Hepworth and Pettengill 1980). An exceptional sport fishery developed in the late 1960's and early 1970's which gained Lake Powell a national reputation as a bass and crappie fishery. Walleye were never introduced into Lake Powell but a population grew from stock present when the reservoir was impounded. The walleye fishery peaked in the early 1980's.

Striped bass fingerlings were introduced in 1974 and began contributing to the sport fishery in 1979, the year they became sexually mature. At the time of introduction striped bass were not expected to reproduce successfully. It was soon discovered that striped bass natural reproduction occurred not only in the Colorado River above Lake Powell but also in the reservoir proper (Gustaveson et al. 1984). Growing striped bass and walleye populations exerted extreme predatory pressure on the threadfin shad forage base. Finally, in 1982, 1983, 1985, and 1986 striped bass and walleye populations suffered declines in physical condition and numbers directly attributable to lack of adequate forage. Neither population has shown signs of recovery to date.

-4- Table 1. Stocking history of Lake Powell, Utah-Arizona, 1963-1988.

Year Species Number Size Area Method

1963 Largemouth Bass 924,000 2-3" Warm Creek-Aztec Aerial

Rainbow Trout 3,000,000 2" Reservoir Wide Aerial Rainbow Trout 800,000 2-4" Wahweap Creek Truck Rainbow Trout 35,000 4" Hall's Crossing Truck

Kokanee Salmon 600,000 1-2" Kane Creek Truck

1964 Largemouth Bass 1,000,000 2-3" Warm Creek-Last Chance Aerial Largemouth Bass 250,000 2-3" Mouth Escalante Aerial Largemouth Bass 250,000 2-3" Rincon Aerial Largemouth Bass 500,000 2-3" Bullfrog Creek Aerial

Rainbow Trout 3,000,000 2-3" Dam-Bullfrog Creek Aerial Rainbow Trout 325,650 5-8" Hite Truck Rainbow Trout 365,730 5-8" Wahweap Creek Truck

Kokanee Salmon 35,000 2-3" Wahweap Creek Truck

Black Crappie 350 6" Wahweap Creek Truck Black Crappie 9,000 3" Wahweap Creek Truck

1965 Rainbow Trout 4,383,525 2-3" Reservoir Wide Aerial Rainbow Trout 40,000 5" Wahweap Creek Truck

Black Crappie 30,000 1" Wahweap Creek Truck Black Crappie 4,700 4" Wahweap Creek Truck

1966 Rainbow Trout 2,140,000 2-3" Reservoir Wide Aerial

1967 Rainbow Trout 344,049 4-5" Wahweap-Warm Creek Aerial Rainbow Trout 103,205 4-5" Hall's Crsng-Bullfrog Barge Rainbow Trout 102,590 4-5" Red Canyon Barge

1968 Rainbow Trout 201,364 3-5" Wahweap Creek Barge

Threadfin Shad 1,500 1-4" Wahweap Creek Truck

1969 Rainbow Trout 251,238 5" Wahweap Creek Barge

Threadfin Shad 200,000 Egg-fry Wahweap Creek Spawning mats

1970 NO STOCKING -

1971 Rainbow Trout 281,000 4-5" Bullfrog Barge Rainbow Trout 527,000 4-5" Wahweap Creek Barge Rainbow Trout 40,000 4-6" Warm Creek Barge

-9- Table 1. Continued.

Year Species Number Size Area Method

1972 NO STOCKING ------

1973 Rainbow Trout 233,400 5" Wahweap Creek Truck

1974 Striped Bass 49,885 2-3" Wahweap Creek Truck

1975 Striped Bass 94,878 2-3" Wahweap Creek Truck

1976 Rainbow Trout 50,000 3-6" Wahweap Creek Truck

Striped Bass 35,752 2-3" Wahweap Creek Truck Striped Bass 19,305 2-3" Bullfrog Aerial

1977 Rainbow Trout 18,600 5" Wahweap Creek Truck

Striped Bass 86,003 2-3" Wahweap Creek Truck Striped Bass 52,650 2-3" Bullfrog Aerial

1978 Striped Bass 169,469 2-3" Wahweap Creek Truck Striped Bass 84,821 2-3 Bullfrog Aerial-Truck

1979 Striped Bass 222,550 2-3" Wahweap Creek Truck

1980 Rainbow Trout 13,210 6" Wahweap Creek Truck

1981 NO STOCKING

1982 Smallmouth Bass 3,100 2-4" Warm Creek Truck Smallmouth Bass 59 10-15" Warm Creek Truck

1983 NO STOCKING

1984 Smallmouth Bass 26,600 2-4" Wahweap-Warm Creek Truck Smallmouth Bass 4,000 2-4" Stanton Creek Aerial

1985 Smallmouth Bass 13,289 2-4" Wahweap Creek Truck Smallmouth Bass 12,389 2-4" Antelope Canyon Truck Smallmouth Bass 22 10-15" Antelope Canyon Truck Smallmouth Bass 31,995 2-4" Rincon Aerial Smallmouth Bass 19,390 2-4" Good Hope Bay Aerial Smallmouth Bass 26,328 2-4" Neskahi Canyon Aerial Smallmouth Bass 702 10-15" Hite-Dirty Devil River Truck

1986 Smallmouth Bass 12,758 2-4" Escalante River Aerial Smallmouth Bass 8,136 2-4" Piute Farms Wash Truck Smallmouth Bass 6,123 2-4" Wahweap Creek Truck

-6- Table 1. Continued.

Year Species Number Size Area Method

1987 Smallmouth Bass 220 3-6" Wahweap-Warm Creek Truck Smallmouth Bass 24,200 2-3" West Canyon Aerial Smallmouth Bass 7,200 2-3" Nokai Canyon Truck 3,150 2-4" Piute Farms Truck

1988 Smallmouth Bass 20,536 2" Knowles/Cedar Canyon Aerial Smallmouth Bass 24,643 2" Llewellyn/Cottonwood Aerial Smallmouth Bass 4,307 2" Middle Rock Creek Aerial Smallmouth Bass 10,745 2" San Juan (mouth) Aerial Smallmouth Bass 10,800 2" Navajo Canyon Aerial

Threadfin Shad

Sufficient forage is the key to producing most successful sport fisheries. Threadfin shad are currently the only pelagic forage fish in Lake Powell and the Colorado River drainage. An open water shad population occurs when intraspecific competition forces young-of-the-year (yoy) shad from their preferred habitat in warm shallow coves and canyons into the pelagic zone (Moczygemba and Morris 1977). Pelagic shad populations have been sampled with mid water trawling since 1977 in Lake Powell and found to be cyclical in abundance (Gustaveson et al. 1985). The pelagic shad population was virtually unexploited prior to 1979 when striped bass began to exert significant predatory pressure on shad. A shad population peak occurred in 1978 followed by a naturally occurring low point in 1980 (Figure 2). Peaks occurred again in 1981 and 1984 suggesting a 3 year recurring cycle in population abundance. The off years are represented by very low numbers of shad in the open water zone. Shad reproduction occured in non-peak years but yoy shad were not forced into the pelagic zone by competition for food and space and therefore were not available to midwater trawl sampling nor pelagic predators. Trawl and sonar sampling confirmed that shad occupy the upper 10 meters in the water column in the stratified reservoir. They were not found below the thermocline. In most years shad were available to shorebound predators such as largemouth bass and crappie but not always available to cool water fish such as walleye and striped bass.

The 1987 shad population was expected. to exhibit the peak in numbers that has occurred at three year intervals. Unfortunately, each succeeding peak since 1978 has been progressively smaller (Figure 2). A peak did not materialize in 1987 with no shad being collected in trawl samples in most areas of the reservoir. Shad were completely absent from pelagic trawl sampling in 1988 and 1989. The shad population is not currently available to those species (walleye and striped bass) which depend almost entirely on threadfin shad for sustenance.

-7- Figure 2.Meannumberofthreadfinshadcollectedpertrawltow,July-September

SHAD/TRAWL TOW 2000 — 3000 — 4000 1000 — 200 400 60 80 Lake Powell,1977-89. 1977 197819791980198119821983198419851986198719881989

-8- YEAR Other Forage Organisms

Other forage fish consumed by Lake Powell's game fish include bluegill (Lepomis- macrochirus), green sunfish (Lepomis cyanellus), red shiner (Notropis lutrensis) and carp (Cyprinus carDio). Crayfish (Orconectes virilis), zooplankton, and aquatic insects are also consumed. Most of these organisms are eaten by game fish associated with the littoral zone and yoy of all species. In years when shad numbers are low the predatory burden on these other species is increased.

Largemouth Bass

The highest relative abundance of largemouth bass, as measured by annual spring gill netting, occurred in 1972. The population has since fluctuated in a generally downward trend (Figure 3). The last 5 years have shown a stabilization of the largemouth population at a level below that seen in peak years, but probably quite similar to bass populations in other deep, oligotrophic canyon lakes.

The decline of the largemouth bass population can best be related to the decline of brushy cover in the lake. As the reservoir filled, the floodplain of the Colorado River was inundated and flooded new brushy habitat annually. In more recent years the annual spring flood was contained by the cliffs surrounding the Colorado River basin, adding little in the way of brushy substrate. Rising water in the springtime was seen as a vertical increase on the steep canyon walls. With time, the flooded desert vegetation decomposed and was eliminated. The reservoir reached full pool in 1980 and then began an annual fluctuation pattern. As the lake level declined each fall, the thin layer of soil covering the rocky substrate was lost. Woody terrestrial plants and shrubs disappeared and have not reestablished under this water management regime. The annual crop of yoy bass relied heavily on brush for nursery and escape cover. Without brush, recruitment of bass is limited by predation. Without increased recruitment, largemouth bass are not expected to expand in number beyond their current population level.

Floods occurred in 1983 and 1984 causing the reservoir to fill above full pool. With flooding of new soil and brush largemouth bass experienced high yoy survival and recruitment. The largemouth fishery in 1987 was the best seen in the past 5 years and directly attributable to high survival of young bass in the flood years.

Smallmouth Bass

Smallmouth bass were introduced in 1982 to supplement the black bass population which was recognized to be declining. While largemouth bass prefer shallow, weedy cover, smallmouth seek out rocky substrate for spawning and thrive in deeper water with rocky structure. Smallmouth fry are adept at utilizing rocky substrate for escape cover while largemouth fry seek out brush and shallow water to escape predators.

The smallmouth bass introductions have been quite successful. Many satellite populations have been established throughout the lake. Natural reproduction has been documented at many of these locations and annual growth rates have been comparable to largemouth bass collected at the same locations

-9- c 0b 4

\ Largemouth Bass m 3

/"\ • /. \ /. \. 2 \

1 1 1 E 1 1 1 1 1 1 [ 1 1 M 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 Year

5

4 Walleye, 0 T5 3

2 •

\ j \ I \ '

/ \./

I I f I I I I . 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 Year

Figure 3. Catch rates (fish/net day) for walleye and largemouth bass during annual trend gillnetting at Lake Powell, 1972-88.

-10- (Gustaveson et al. 1988). The population is building and smallmouth are beginning to be harvested in fair numbers by Lake Powell anglers. It presently appears that smallmouth are well adapted to Lake Powell and they will provide an acceptable sport fishery in concert with largemouth bass. These fisheries require an angler with some expertise before success is achieved and do not attract the average or inexperienced angler.

Black Crappie

Crappie abundance has declined in much the same manner and for the same reasons as have largemouth bass. Crappie are even more dependent on brush than largemouth. Crappie prefer to nest on substrate with brush or some other structure near to provide overhead cover. Crappie yoy become somewhat pelagic at a length of 10-20 mm. Without brush in the water column for protective' cover these young are easy prey for all predatory fish.

The future for crappie is not bright. With the present annual water fluctuation it is not possible to grow enough terrestrial brush in one growing season to provide nursery and escape cover for the next year's crop of fry. Rising water in the spring covers barren ground that was only recently exposed. Crappie populations are presently confined to localized areas where environmental conditions are favorable for completion of the entire life cycle. Crappie are resilient and prolific enough to "hang on" in some areas of the lake with suitable structure but they will never again achieve the population densities that made them a favorite with anglers in the early 1970's. The decline of this fishery reduced success of anglers and has contributed to the recent decline in fishing pressure.

Walleye

Walleye were present in the Colorado River drainage when Lake Powell was impounded. Walleye numbers slowly increased as the reservoir filled. Early lake conditions were probably more favorable for centrarchids, as rising water inundated the flat, brushy Colorado River floodplain. When the lake began to fill the Colorado River gorge, deep rocky habitat was created which favored walleye proliferation. The walleye population boomed in the late 1970's and peaked in 1981 - one year after the reservoir filled (Figure 3). Walleye were notoriously hard f6r anglers to catch in the 1970's but a good fishery occurred in the early 1980's when the walleye population was at a numerical peak. Walleye numbers declined in 1982 and 1983 in response to the decline in shad forage. Anglers again experienced difficulty catching walleye as fish numbers declined below the relative abundance threshold that seems to separate good fishing from poor fishing (Figure 3).

Walleye seem to be limited only by available forage. Sufficient habitat is available for spawning and recruitment. Some predatory pressure is probably exerted on yoy walleye in years when shad abundance is low and shad are not available to buffer walleye from other predators. Under the present conditions walleye will continue to be a minor contributor to Lake Powell sport fisheries. Walleye continue to be a significant predator on other game and forage fish in Lake Powell despite their poor showing in the anglers' creel. Catfish

Channel catfish (Ictalurus punctatus) and yellow bullhead (Ictalurus natalis) create a popular seasonal fishery in Lake Powell. Neither species achieves large size due to the great depth of the lake and the lack of an extensive littoral zone. These bottom dwellers are often forced to forage in the water column rather than in the littoral zone to which they are accustomed. Catfish provide a good summertime fishery lakewide for 200-355 mm (8-14 in) fish, and an excellent fishery for bigger fish near the San Juan and Colorado River inflow areas. These fisheries are not expected to change greatly with time.

Threatened and Endangered Species

Fishes endemic to the Colorado River were predominant in the drainage before Lake Powell was impounded. These "big river" fishes are not now known to complete their life cycle in the reservoir and occurrence of adults in the reservoir is rare. During the past decade a few adult squawfish (Ptvchocheilus lucius), chubs (Gila spp.), and razorback suckers (Xyrauchen texanus) have been collected and released. Flannelmouth suckers (Catostomus latipinnis) were abundant in the 1960's but have steadily declined with time and presently are rarely collected. A few adults may migrate into the reservoir and reside there until returning to the river to spawn. Lake Powell tributaries and headwaters may be important to these fishes but the lake environment is not suitable for spawning or survival of the young of these riverine species.

Striped Bass

Striped bass were first stocked in 1974. Natural reproduction was first detected in 1979 at which time stocking was discontinued so impact of natural reproduction could be evaluated. Growth of introduced fish was rapid with little intraspecific competition and an abundant shad population. A significant sport fishery emerged in 1979, coinciding with striped bass sexual maturity. The sport fishery peaked in 1982-1983 when the first generation of naturally reproduced fish attained sexual maturity. In 1982 high numbers of striped bass and low numbers of shad (Figure 2) combined to produce the first signs of striped bass malnutrition. Condition factors for adult striped bass declined -to approximately 1.0 (Figure 4). Many of the older fish, which were hardest hit by the lack of forage, were easy game for anglers and were harvested during 1982-1983. Many of the larger fish, especially those in the poorest condition, were eliminated from the population by sport harvest or natural mortality. The subsequent shad population peak in 1984 allowed striped bass adults to again gain acceptable physical condition. However, with the small shad crop produced in 1985 and 1986, physical condition of all ages of striped bass fell to new low levels. During the winter of 1986-1987 evidence of a die-off of adult striped bass was seen throughout Lake Powell. During the spring of 1987 striped bass over 500 mm (20 inches) made up a small percentage of the total population. Subadult striped bass were still present in large numbers since they were able to forage on large zooplankton and maintain good body condition.

Physical condition and growth of striped bass has varied in direct relation to the abundance of threadfin shad (Figures 2 and 4). Shad failed to produce their expected cyclical peak in abundance in 1987. There has been

-12-

1.8 —

1.6 — Juvenile

1.4 --

1.2 ...... Adult FACTOR (Fork length) K

0.8 1

.75 76 77 78 79 80 81 82 83 84 85 86 87 88 89

SAMPLE YEAR

Figure 4. Mean condition factor (Kfl) of adult and juvenile striped bass at Lake Powell, 1975-89.

-13- virtually no open water shad population since 1984. Striped bass cannot be expected to regain trophy size or attain acceptable physical condition until adequate pelagic forage is again available.

Unlimited natural reproduction is a mixed blessing. The immediate result was the overcropping of the shad supply with a subsequent decline in the quality of the fishery. If forage were less limiting, larger striped bass could be produced in a quantity substantial enough to satisfy the fishing desires of a much larger angling public than currently utilizes Lake Powell. Increased angling pressure created by a rejuvenated striped bass fishery could help stabilize the population. An annual harvest in excess of 1 million fish has been reported at Lake Mead (John Hutchings, Nevada Department of Wildlife, personal communication 1985). Harvesting 1 million 4 pound fish from lake Powell is possible. But anglers have not been willing to exert the pressure needed for that type of harvest unless desireable fish are present. Angling pressure has declined since size has decreased from 4-10 pound striped bass down to 1 pound striped bass. The reduction in fishing pressure has further compounded the striped bass overpopulation problem.

ENVIRONMENTAL COMPONENTS NOT AFFECTED

The evaluated alternatives do not affect the flood plains/wetlands, water quality, terrestrial wildlife, prime and/or unique farmland, cultural resources, agriculture, or residential concerns.

COMMERCIAL CONCERNS

Although fishing pressure continues to decline, visitation to Glen Canyon National Recreational Area is increasing. Businesses which are not directly related to supporting anglers are not affected by the decrease in anglers use of Lake Powell. However, businesses which directly support fishing by supplying bait, tackle, etc. are affected. Local businesses including restaurants and motels have complained of the loss of anglers. Prior to the shad collapse excellent striped bass fishing attracted more anglers. Many anglers who would travel to Lake Powell to catch large healthy striped bass are not attracted by small fish in poor condition.

The introduction of rainbow smelt will have little affect on nonfishing use of Lake Powell. Local businesses in areas adjacent to lake access points will have increased business opportunities due to an increase in anglers. Economic benefits during periods of good fishing can be substantial. However, no economic analysis of a smelt introduction on businesses has been conducted.

RECREATION

Striped bass are an important component of the Lake Powell Fishery. As catch rates of largemouth bass and black crappie declined, due to changes in the reservoir as a result of filling and lake maturation, striped bass provided new recreational opportunities for anglers. Catch rates of striped bass filled the void left by declining stocks of largemouth bass and black crappie. Under current predator-prey conditions, small striped bass in

-14- marginal condition are no longer meeting the needs of Lake Powell's anglers. Fishing pressure, measured as fishing-boat days, has declined from 128,186 in 1985 to 98,148 in 1988. This represents a decrease of 23% directly attributable to declines in the striped bass fishery. The reestablishment of a quality striped bass fishery will restore recreational opportunities to at least former levels.

ALTERNATIVES

INTRODUCTION

The elimination of the pelagic shad population and subsequent decline in physical condition and abundance of walleye and striped bass caused great concern for the future of Lake Powell fisheries. The similar occurrence of striped bass declines in Lake Mead and Lake Havasu indicated that a basin wide problem was occurring and some action was needed. The Colorado River Wildlife Council's Striped Bass Committee raised the alarm and began searching for possible solutions in 1983. Utah proposed forage fish introductions as one solution. Biologists from various states including Utah conducted literature reviews to find appropriate candidates for introduction or other solutions to the problem. During this same period, the Utah Division of Wildlife Resources initiated more liberal bag limits in an attempt to reduce juvenile striped bass numbers thus allowing resurgence in the threadfin shad population. Creel limits were increased from 2 to 4 fish in 1983 and from 4 to 10 fish in 1984. Shad numbers increased somewhat in 1984 but collapsed in 1985 and have remained suppressed through 1989. Lake Powell regulations have again changed in 1990 to allow a daily bag limit of 20 striped bass. Under the guidelines of the Utah Division of Wildlife's Strategic Management Plan, alternatives for management of the Lake Powell fishery were discussed and evaluated on both the regional and state levels.

LAKE POWELL MANAGEMENT OBJECTIVES

Utah has developed a strategic plan for the comprehensive management of the State's wildlife resources. Two management concepts are applicable to Lake Powell, One, described as the basic yield concept, prescribes the management of a water to optimize yields of acceptable size fish for the general public's satisfaction; the other, for trophy fish, prescribes the management of a water to produce fewer but larger fish for a more discriminating constituency.

As already outlined, Lake Powell supports a diverse population of warm water sport fishes that contribute in varying degrees to the sport fishery. Generally most of these fishes have supported an extensive basic yield fishery providing a satisfactory rate of catch of modest but acceptable sized fish. The striped bass, however, has demonstrated the capability to grow to trophy size, when in balance with its forage supply, and, therefore, has the potential to provide a highly valued trophy fishery in addition to a substantial yield of smaller fish.

To meet or exceed minimum acceptable catch rates size and quality for a basic yield fishery, the Utah Division of Wildlife's strategic plan prescribes the maintenance of a minimum catch rate of 0.5 fish per hour for fish in

-15- acceptable physical condition, and the following average sizes for each species of fish:

SPECIES LENGTH (mm) RANGE (mm) Largemouth Bass 305 [12"] 203-381 Smallmouth Bass 305 [12"] 178-356 Black Crappie 229 [9n] 178-279 Walleye 356 [14"] 254-406 Striped Bass 457 [18"] 381-533 Channel Catfish 305 [12"] 229-381

Striped bass also fall within guidelines for trophy fish management standards which call for an average catch of 0.05 fish per hour for trophy size fish 21 inches (533 mm) and larger.

ECONOMIC BENEFITS

Anglers visitation and use at Lake Powell has shown an average annual • increase of 17% from 1966-1985 (Scott and Gustaveson 1986). However, from 1985-1988 fishing pressure has decreased 23% while visitation and other recreational uses at Lake Powell have increased annually (Gustaveson et al. 1989). If fishing pressure would have continued to increase 17% each year, pressure in 1988 would have been 205,304 boat-days of fishing, therefore, the partial collapse of the Lake Powell fishery has resulted in a net loss of 107,156 boat-days of fishing in 1988. The total fishing boat-days lost represents 278,606 angler-days (mean angler/boat from 1975-1985 was 2.6). The U.S. Fish and Wildlife Service (1988) in their 1985 National Survey reported average expenditures per day for .freshwater anglers to be $23.19. The result, therefore, was a minimum loss of $6.5 million in expenditures for fishing on Lake Powell in 1988. These losses directly affect local and state economies. Because of distances from Lake Powell to major population centers, this estimate is extremely conservative. In 22 years of creel census on Lake Powell 49% of all anglers were from states other than Utah or Arizona (Scott and Gustaveson 1986). On a national average only 20% of anglers fished in states other than their residence (U.S. Fish and Wildlife Service 1988). Lake Powell's prominence as an excellent family and trophy fishery attracted anglers nationwide. In a valuation study on the Glen Canyon Dam tailwater, it was estimated that the value of the fishery would increase 56% if the chance of catching a trophy fish were doubled (Glen Canyon Environmental Studies 1987). The result of any alternative (action or no action) which fails to return the Lake Powell fishery to its national prominence results in minimum direct losses of $6.5 million/year in fisheries related revenue.

ALTERNATIVES EVALUATED

The alternatives which are described in this section were recommended by various state and federal biologists who reviewed early proposals for management of the Lake Powell fishery. The alternatives attempted to approach the problem from a wide spectrum of approaches. Because of the importance of Lake Powell to Utah and anglers throughout the Western United States, it is imperative that the alternative selected reverse the present trend of declines in angler use and satisfaction. It has been demonstrated that a successful striped bass fishery in Lake Powell meets this need. Alternatives include

-16- rainbow smelt introduction, pygmy smelt introduction, a multi-species forage complex introduction, allowing commercial harvest, regulation changes, and no action with emphasis on other components of the fishery. Various alternatives that were considered and dismissed are also described.

PROPOSED ACTION - RAINBOW SMELT INTRODUCTION

Rainbow smelt, a deep-water pelagic fish, would be introduced into Lake Powell as an additional forage for striped bass and walleye and other game fish, and to buffer the existing threadfin shad population from collapse caused by predation or environmental factors. Based on selection standards and giving full consideration to endangered species the introduction of rainbow smelt was chosen as the best alternative.

PYGMY SMELT INTRODUCTION

Pygmy smelt, an obligate planktivore throughout life, would be introduced into Lake Powell in an attempt to buffer predation on the existing threadfin shad population.

MULTI-SPECIES FORAGE COMPLEX

Introduce a multi-species forage complex into Lake Powell to provide additional forage for striped bass and other game fish species in an attempt to provide a stable prey base.

COMMERCIAL FISHERY

Regulations permitting commercial fishing on Lake Powell would be enacted. Methods and seasons would be established by regulating authorities. Licensing, incidental catch of other species, and other concerns would also be addressed.

REGULATION CHANGES

Bag limits on striped bass would be increased or removed. Harvest w be permitted next to Glen Canyon Dam, an area of seasonally high concentrations. The release of live striped bass back into the water would be prohibited.

NO ACTION

Striped bass and walleye populations would be allowed to remain in poor condition providing reduced recreational benefits. Anglers would be encouraged through education to take advantage of other fish species within Lake Powell or be directed to fish other waters where a preferred target species is available.

-17- DISCUSSION OF ALTERNATIVES

RAINBOW SMELT INTRODUCTION

Introducing a forage fish that prefers cool water and primarily inhabits the zone at and below the thermocline can be beneficial to a variety species. Shad, which normally occupy warm shallow zones, will not compete with a deep water fish for food or space in the stratified reservoir. They will interact in the winter when shad are not actively feeding and after shad have obtained a size larger than usually consumed by the new forage fish. Predatory pressure of striped bass and walleye will be diverted to the new forage fish allowing the shad population to rebuild to the extent that predation and food availability will allow.

Plankton availability has not changed dramatically since the initial investigations in the 1960's (Sollberger et al. 1989). The productivity that allowed large populations of pelagic shad to exist is still present in the reservoir. Since a pelagic shad population does not now exist, much of the primary productivity of the reservoir is utilized only by pelagic juvenile striped bass and inefficiently converted to fish flesh. Most of the plankton are found above the thermocline. There are plankton in the deep water zone and plankton abundance is similar at times to plankton abundance of the Great Lakes where deep water forage fish are established (Sollberger el al. 1989).

If a deep water forage fish was established, the most obvious fish to benefit would be walleye and adult striped bass. Both species would have forage available in their cool water habitat. They would not have to forage in the warm epilimnion when the lake is stratified. Centrarchids would benefit indirectly since shad in the epilimnion would not be as heavily cropped by adult striped bass and walleye.

The most pressing reason to establish another forage fish would be to provide adequate forage for all game species in years when shad are at a low point in their cycle. In years of low shad production more open water plankton would be available to other species. Increased production of prey from the introduction of new forage species will provide more food for all game species.

A deep water forage fish will have no effect on the remnant adult population of threatened and endangered fish in the reservoir. Since "big river" fish have not been found to reproduce in the reservoir, the new forage fish will not interact with yoy endangered species. There may be some incidental interaction of endemic fish with rainbow smelt in the tributaries if smelt spawn in the inlet areas of tributaries but the impact is expected to be minimal and not detrimental to the resident fishes in those areas. Valdez (1990) concluded that the smelt posed no threat to the endangered fishes inhabiting Cataract Canyon and Lake Powell.

Downstream migration of a deep water forage fish is likely. It is important that any candidate forage fish will not potentially harm the important tailwater trout fisheries, nor cause irreparable damage to existing fisheries downstream. It is unlikely that the rainbow smelt will migrate upstream above Lake Powell due to the swift, silty nature of the inflowing rivers and rapids that forms barriers to upstream migration. Smelt in other

-18- waters have shown no tendency to become established in riverine environments. Minimum criteria reviewed prior to selection of rainbow smelt included but was not limited to: 1) reproductive potential, 2) population stability, 3) trophic efficiency, 4) vulnerability to predation, 5) innocuousness (Ney 1981).

PYGMY SMELT

Lanteigne and McAllister (1983) identified the pygmy smelt (Osmerus spectrum) as a valid lacustrine sibling species distinguishable from rainbow smelt. Transplant experiments demonstrate that gill raker and vertebral counts do not change significantly when pygmy smelt populations are transplanted to different environments. Spawning times of pygmy smelt are later and do not overlap with those of rainbow smelt when the two species are in the same lake. Pygmy smelt do not engage in long distance spawning movements. The pygmy smelt is a planktivore throughout its life with no piscivorous tendencies. It grows more slowly (125 mm TL), has lower longevity, and spawns at a younger age. Pygmy smelt are characterized as non- migratory (Lanteigne and McAllister 1983, Hadley 1982). Introduction of pygmy smelt may reduce the possibility of smelt predation on larval fishes and migration downstream from Lake Powell. Pygmy smelt prefer warmer and shallower water than rainbow smelt which may increase competition for plankton between pygmy smelt and other species. Their smaller size will render them more vulnerable to predation, however, which reduces the likelihood of their coping with Lake Powell's large predator populations. If pygmy smelt were unable to establish in Lake Powell, anglers dissatisfaction would remain high and fishery objectives would not be met.

MULTI-SPECIES FORAGE COMPLEX

The best method to insure adequate forage for all species would be to duplicate the forage regime that exists in other waters with conditions similar to Lake Powell, yet without the acute forage problem that exists here. Lake Texoma is a 35,600 ha reservoir on the Red River which forms the Texas- Oklahoma border. It was impounded in 1944. Average depth is 9.5 m with maximum depth of 28 m. The reservoir contains largemouth bass, spotted bass (Micropterus punctulatus), white bass (Morone chrvsops), white crappie (Pomoxis annularis), black crappie, and various sunfishes (Centrarchid spp.). Striped bass were introduced in 1965 and found to be naturally reproducing in 1973. Forage species include threadfin shad, gizzard shad (Dorosoma cepedianum), inland silversides (Menidia beryllina), drum (Aplodinotus grunniens), blacktail shiner (Notropis venustus), and other minor species (Mauck 1986).

Striped bass fed mainly on schooling forage fish despite the abundance of other forage species. White bass also utilized the pelagic shad population. Other forage organisms were mainly used by shorebound centrarchids.

Striped bass produced over-abundant year classes in 1982 and 1985. Threadfin shad winter killed in 1981-1982. Floods disturbed the reservoir in 1982. Striped bass responded to these catastrophic events by suffering poor body condition during 1982. Yet, due to the diversity of the forage base, the

-19- striped bass fishery has recovered and provides excellent fishing for large striped bass. Between 1983-1986, 30-50% of all striped bass caught exceeded 500 mm (19.6 in) which are classified as trophy size fish by the Oklahoma Department of Wildlife. Striped bass have not detrimentally effected other fisheries, nor have they continued to increase in population abundance until they depleted all forage in the reservoir. The striped bass population seems to be as close to "balanced" as possible for this prolific, long-lived predator.

Striped bass were landlocked in Santee-Cooper reservoir in 1941. Natural reproduction was described during the 1950's, however, because of changes in water quality, river regulation, and increasing vegetation; reproduction is now limited. This reservoir has existed for over 40 years and still consistently produces successful striped bass, centrarchid, and catfish fisheries. Forage is more diverse at Santee-Cooper with the main species being threadfin and gizzard shad, alewife (Alosa psuedoharengus), blueback herring (Alosa aestivalis), and various centrarchids, carp, and catfish. Stevens (1957) described the striped bass fishery there to be "...very successful, a positive influence upon the ecology of the total fish population, and worth millions of dollars and countless hours of pleasure to the people of South Carolina."

A multi-species forage complex at Lake Powell could create a more balanced predator-prey system less susceptible to cyclic collapse. A mix of some or all of the pelagic forage species such as threadfin shad, gizzard shad, alewives, blueback herring, and rainbow smelt would provide a forage rich environment for adult game fish. Some or all of these species would be seasonally available to predators. The additional prey species competing for food would utilize the lake's plankton base to its fullest extent. Juvenile striped bass would not have the luxury of feeding on plankton in the pelagic zone as it would be cropped by the more efficient forage fish. Adult striped bass are better equipped to forage on a fish diet and would have the competitive advantage over juveniles. Striped bass would grow faster on a fish diet and then be forced by physiological change into the cooler temperature strata as they matured (Schaich 1979). Striped bass recruitment should be reduced in a system where sizeable numbers of adult stripers are present.

Plankton is finite in oligotrophic Lake Powell and introduction of a forage complex would make it difficult to predict which species of forage would become dominant. Some species may not successfully compete and may not proliferate. The multiple species concept has greater risk involved since all of the newly mentioned species have greater potential for negative interaction with established fishes. Striped bass in Lake Powell would be benefitted most by this alternative but the downstream impacts outweigh the expected benefits (Table 2).

COMMERCIAL FISHERY

Creating a commercial fishery for game fish would be a basic departure from the philosophy of noncommercialization of protected wildlife which is espoused by Arizona, Utah, and the National Park Service. Selling game fish to restaurants has been a recurring problem in Utah. If the sale of striped

-20- bass was legalized, other game fish species could be sold illegally under the guise of legal striped bass. The enabling legislation that created Glen Canyon National Recreation Area specifically forbids commercial fishing within the recreation area.

A more pressing problem is affecting an economically feasible method of capturing striped bass commercially. Non selective gill nets could not be used because of the impact on nontarget game and endangered species. Towed nets and purse seines would be most effective in large bays most often used as play areas by recreationalists and anglers. While it would be possible to effectively capture striped bass in commercial netting equipment, conflict and contention between commercial fishers, sport anglers, and boating enthusiasts would be substantial from the very outset of a commercial fishing program. Because of the poor physical condition and small fish size of striped bass finding a commercial outlet is questionable. If effective, a commercial fishery would be desireable only during periods when the striped bass population was threatening the forage fish population.

The importance of Lake Powell in generating revenue for the states of Utah and Arizona from license sales and associated monies spent by those who use the lake is unquestioned. Those anglers who pay the bills for this fishery to exist must be given priority over the needs of a private commercial anglers who would need many exclusive guarantees to make his operation economically successful.

REGULATION CHANGES

Drastic regulation changes aimed at reducing the striped bass population will probably not have the desired effect. Removing the limit from striped bass will not significantly increase angler harvest since most anglers do not consistently catch limits of striped bass at the present time. There are occasions when fish are congregated and easy to catch, and more than 10 fish per angler can be taken. It is more likely, however, that anglers catch less than a limit of fish on a given day. Anglers want to "catch their limit" and may spend an extra hour trying to catch the tenth fish. They would not have that artificial goal to reach if there was no limit. It may be possible to achieve some increase in harvest by increasing the limit to 15-20 fish. Any higher increase would place the average angler in the position of usually failing to catch his limit and thereby decreased satisfaction with his fishing experience.

Striped bass bag limits on Lake Powell have already been increased, however, because of poor fish quality, fishing pressure has decreased. The resulting decrease in harvest is a trend which will probably continue without further action. Regulations prohibiting the release of live striped bass could potentially affect the number of striped bass presently released alive but would be of little consequence in controlling population numbers. The end result would be marginal striped bass being discarded on beaches and at public facilities potentially creating environmental and health concerns.

An increased harvest of spawning fish could be achieved by reopening the sanctuary created between the dam and the buoy line uplake from the spillways. Striped bass are attracted to current created as the water is released through

-21- penstocks of Glen Canyon Dam. Large schools of adult striped bass stage in this artificial sanctuary area prior to spawning and are easy targets for anglers. These fish are easy to find, easy to catch, and are the very fish that should be targeted for harvest before they can reproduce. Reopening the buoy area for the months of April and May will benefit the fisheries and cause no safety problems near the spillways. Spillway operation would not be expected until June in any year at which time spawning and congregation of fish near the dam is complete. Opening the area to fishing could be done without removing the buoys. Simply covering the buoys with sacks would allow angler access and removing the sacks would reestablish the restricted area.

NO ACTION

Taking no action will leave the Lake Powell fishery about where it presently exists with a possible continued decline in fishing pressure and satisfaction. Shad reproduction will occur in the turbid water at the back of coves and canyons. As yoy shad venture out of the turbid water they will meet intense predation by juvenile striped bass, walleye, black basses, and crappie. Shad recruitment will be depressed by this predation. Shad will seldom occur in the pelagic zone. Without an open water shad population striped bass growth will remain slow and physical condition will remain below acceptable levels. The striped bass population will be dominated by juvenile fish in marginal condition, attempting to maintain themselves on zooplankton. Zooplankton will continue to be cycled inefficiently to fish flesh by planktivorous striped bass instead of plantivorous forage species. The striped bass trophy fishery will continue to decline each year with fewer individuals recruiting to trophy size. This fishery will closely parallel what is now occurring at Lake Mead.

Walleye will not recruit in sufficient numbers to create the type of fishery seen in the early 1980's. The lack of a deep cool water forage fish will not allow the type of population expansion necessary for anglers to be predictably successful in capturing walleye.

The black bass population will build as mature smallmouth become more abundant and produce more young. Smallmouth recruitment would be better than that of largemouth due to the difference in habitat utilization between the two species. The largemouth population will remain stable as they presently fully utilize the littoral brushy habitat available to them. In years when the water is unusually high and new brush is flooded, more recruitment may occur. In low water years largemouth recruitment will be poor. Forage will not be a limiting factor for black bass since they are opportunistic feeders that survive well on a diet of centrarchids and crayfish. They do eat shad when they are available. Historically, black bass have been difficult for less than avid angler to catch. They provide little opportunity to less experienced anglers and are not considered a popular family fishery.

Black crappie production can only be improved by addition of more brush in the reservoir. Crappie production is higher in years when shad production is low. However, predation on yoy crappie increases without a strong shad population to buffer predation on the new crop of young crappie.

-22- One primary concern with no action is that with increased dissatisfaction with the fishery the potential for illicit introductions increases. Bait bucket introductions may include species which are providing forage in other striped bass fisheries but which will serious impact threatened and endangered fish species throughout the Colorado system. No action may generate an image of ineffective management on the part of state and federal agencies and result in members of the fishing public taking actions to correct the problems themselves.

COMPARATIVE ANALYSIS

SELECTION STANDARDS

Five selection standards were used in evaluating the alternatives:

I. Lake Powell management objectives - The selected alternative should be the alternative that most satisfactorily meets the sport fishery objectives set forth by the state's strategic plan.

2. Effects on threatened and endangered species - The selected alternative should have no potential effect on endangered fishes in the upper and lower basins of the Colorado River.

3. Technical feasibility - The selected alternative must be determined to be technically feasible within the immediate future. Alternatives should be limited to possibilities within the present knowledge boundaries of fisheries and all science in general.

4. Monetary constraints - The selected alternative should have only short term costs within present budget guidelines. Excessive initial or long term costs affects feasibility of alternatives.

5. Socioeconomic considerations - Lake Powell is Utah's largest body of water and presently has more fishing pressure than any other Utah water. Through meetings and correspondence, anglers have expressed their dissatisfaction with Lake Powell fisheries in their present condition. The selected alternative should restore angler satisfaction with the sport fishery without negatively affecting other resource values.

-23- Table 2. Alternatives comparison matrix of selection standards.

Selection Standards Fisheries T&E Monetary Technical Socio- Alternatives Objectives Protection Constraints Feasibility Economic

Rainbow Smelt Introduction

Pygmy Smelt Introduction

Multi-Species Forage Complex Introduction ++ +

Commercial Fishery

Regulation Changes -- + + +

No Action -- + o ++

+ meets standards ++ exceeds standards o neutral - does not meet standards -- serious deficit

ALTERNATIVES CONSIDERED BUT DISMISSED

Increasing Reservoir Productivity

Fertilization studies on Lake Mead demonstrated that although plankton productivity could be increased, fertilization resulted in increased numbers of juvenile striped bass, compounding problems of improving fish condition. Improving productivity without deviating from a monotypic pelagic forage fish system did not achieve the desired results. Fertilization increased the boom and bust cycle predator prey relationship now existing at Lake Mead (Dr. L. Paulson, UNLV, personal communication, 1989; J. Hutchings, NV Dept. of WIldlife, personal communication, 1990).

Stocking Additional Threadfin Shad

Although the threadfin shad population in Lake Powell is suppressed, reproduction still occurs each year in the backs of canyons (Gustaveson et al. 1985). The turbid waters reduce predator effectiveness and provide refuge for small populations. However, sufficient numbers remain to restock the reservoir if predatory pressure could be reduced. The stocking of threadfin

-24- shad would benefit the fishery only if enough could be stocked annually to overcome predatory pressures on existing fish. This option is neither technically nor economically feasible.

Introducing Some Form of Sterile Striped Bass

Although triploid striped bass are being developed, stocking this fish would not reduce the number of viable adults. Few striped bass are required to perpetuate the population because of their high fecundity. Lake wide spawning which now occurs negates the effectiveness of introducing sterile striped bass. If a hybrid striped bass was introduced it seems mathematically impossible for sterile striped bass to produce enough non-viable gametes to effective reduce fecundity of the total population.

Stripercides

A piscicide which selectively kills only striped bass has not been developed. Other common piscicides such as Rotenone are not selective and would kill all remaining adult fishes which reside within Lake Powell. The size and depth of Lake Powell make this alternative both technically and economically infeasible. The application of a stripercide over 1820 miles of shoreline cannot logistically be accomplished in any reasonable amount of time.

Limit or Disrupt Spawning

Using gill nets in the upper end of Lake Powell to capture spawning adults or limit upstream passage to spawning areas was recommended. However, striped bass reproduction has been documented lakewide and selective netting would be technically infeasible. The use of explosives in areas of spawning would be nonselective and include the potential for killing all species of fishes in the area. This alternative would also cause concerns for public safety. Neither method is technically feasible.

Introduce Predator For Striped Bass

Striped bass grow quickly and attain a size large enough to avoid predation from any known freshwater predator. The only vulnerable lifestages are egg, larvae, and yoy. Striped bass will prey on other smaller striped bass. A predator would have to be pelagic to encounter striped bass eggs and l arvae. Rainbow smelt may eat stiped bass eggs and larvae.

Create Large Protected Shad Nursery Areas

Block netting large areas of the reservoir to prevent striped bass from entering was recommended. Threadfin shad would be reared in these areas and then released to provide forage for striped bass. The contour and depth of the reservoir make this alternative technically and economically impractical. It is unlikely striped bass could be effectively removed or excluded from these areas.

-25- OTHER CANDIDATE SPECIES CONSIDERED BUT DISMISSED

Forage organisms with potential to solve the problem of striped bass and walleye forage limitations must meet some basic requirements. Fish species must be schooling and pelagic to satisfy the narrow prey search image of striped bass. Fish must have narrow coldwater thermal requirements to fit into the presently unoccupied deep water niche that is available. The species must be prolific, trophically efficient, and vulnerable to predation by striped bass. A candidate species must be able to survive in Lake Powell to be considered.

Reason for rejection of species

1. Species not found to be a schooling fish that occupies the pelagic zone.

2. Species able to occupy a broad range of habitats and temperatures; not confined to the cold water pelagic zone resulting in habitat overlap with imperiled endemic species.

3. Species without a reasonable expectation of becoming established due to specific habitat or behavioral requirements.

4. Species not available to striped bass, usually occupies the littoral zone.

5. Individuals of species quickly attain a size too large to provide forage for most game fish.

Table 3. Species considered for introduction into Lake Powell.

SPECIES CONSIDERED SCIENTIFIC NAMES REJECTION CRITERION

Mississippi silverside Menidia audens 1,2,4 Brook silverside Labidesthes sicculus 1,2,4 Lake chubsucker Erimyzon sucetta 1,2 Blueback herring Alosa aestivalis 2 Alewife Alosa pseudoharengus 2 American shad Alosa sapidissima 2,5 Gizzard shad Dorosoma cepedianum 2,5 Longjaw cisco Coregonus alpenae 3 Lake herring Coregonus artedii 1,5 Deepwater cisco Coregonus johannae 3 Kiyi Coregonus kiyi 3 Bonneville cisco Prosopium gemmiferum 3 Pond smelt Hypomesus olidus 2 Delta smelt Hypomesus nipponensis 2 Lake chub Couesius plumbeus 3 Utah chub Gila atraria 3 Silver chub Hybopsis storeriana 2 Emerald shiner Notropis atherinoides 1,4

-26- Table 3. Continued.

SPECIES CONSIDERED SCIENTIFIC NAMES REJECTION CRITERION

Spottail shiner Notropis hudsonius 2,4 Trout-perch Percoosis omiscomavcus 2 Razorback sucker Xvrauchen texanus 1,4,5 Suckers (general) Catostomidae 1,4,5 Mottled sculpin Cottus bairdi 1,4 Striped mullet Mugil cephalus 3 Humpback chub Gila cvoha 1,3 Bonytail Gila elegans 1,3 Roundtail chub Gila robusta 1,3 Colorado Squawfish Ptvchocheilus lucius 1,3,5 Daces Cvorinidae 1,4

ANALYSIS OF ENVIRONMENTAL CONSEQUENCES

EXPECTED BENEFITS

The establishment of rainbow smelt in Lake Powell will increase forage species diversity and abundance. Since smelt will be thermally partitioned from shad in the stratified reservoir the two species will occupy different niches thereby more effectively channeling primary productivity to all fish eating predators. Smelt would provide food for deep water predators which are thermally restricted to the cool water of the stratified reservoir. Striped bass and walleye will consume smelt during all seasons. Shorebound centrarchids would primarily consume shad, other centrarchids and crayfish (Orconectes virilis) during the summer and utilize smelt after fall turnover. More forage will be available to all game fish. Since walleye and striped bass preferentially eat fish when available, more crayfish will be left for centrarchids.

Adding another forage species will increase the chances of maintaining a more stable supply of forage. When one species was at a population low point it is likely that the other species will increase in numbers in response to an increase in plankton abundance.

Smelt grow larger than threadfin shad. Larger and more abundant forage will allow striped bass to attain larger size than at present. The establishment of smelt will lead to an immediate dramatic increase in the average size of striped bass. Mature striped bass prefer cooler water temperatures than juveniles (Schaich 1979). Providing forage to adult striped bass residing in the hypolimnion can shift striped bass biomass from the epilimnion to the depths of Lake Powell. A healthy adult striped bass population can help balance that population with a more even mix of adult and juvenile fish. Larger striped bass will increase angler interest. Increased angling pressure will be directed at mature striped bass which will offer some

-27- population control of this long lived predator. Increased angling pressure will also increase revenue gained from license sales, boat rentals, and money spent during angler visits to Lake Powell.

Smelt are a much sought after food and sport fish in New England, the Great Lakes and the Missouri River reservoirs (McKenzie 1958, Flagg 1984, Scott and Crossman 1973; Marrone, SD Dept. Game Fish and Parks, personal communication, 1987). A dipnet and hook-and-line fishery is enjoyed by thousands of anglers annually. A similar sport fishery for smelt could develop in Lake Powell during the early spring season when other lake uses are at a minimum. A smelt run in the spring will benefit the local economy during an otherwise slow period.

LAKE POWELL PRODUCTIVITY AND PLANKTON ABUNDANCE

The Lake Mead Limnological Research Center at the University of Nevada, Las Vegas was contracted to study plankton abundance at Lake Powell from August 1987 to June 1988. They found that Lake Powell fit the classification of an oligotrophic lake based on Chlorophyll-a (Chl-a) measurements which averaged about 1.5 ug/1 within the range of 0.5-5.0 ug/l. Inorganic nitrogen was readily available but bio-available phosphorous was limiting resulting in the low Chl-a measurements. Chl-a measurements were often higher near the inflow ares in the upper extremities of the reservoir.

Zooplankton abundance in Lake Powell has changed little since early studies in the 1960's. Zooplankton densities were studied in the newly filling Lake Powell by Arizona Game and Fish Department (Stone and Rathbun 1969). Zooplankton densities were reported to be less than 50 plankters/1 in the upper 30 m (100 ft) and rarely exceeded 20/1 in the same stratum at down lake stations. Zooplankton studies during 1981-82 showed similar densities at all stations with values rarely exceeding 20/1 (Sollberger et al. 1989). In 1987-88 zooplankton densities were normally less than 20/1 in the upper 40 m (130 ft) of the water column within the range of 3-26 plankters/1. About 70% of the zooplankton was found in the upper 10 in (30 ft). The population was dominated by nauplii and copepodites (Sollberger et al. 1989).

Under these conditions the threadfin shad population was able to establish in the reservoir in 1969. Shad proliferated and maintained an abundant pelagic population until the 1980's when striped bass eliminated them from the open water. Plankton abundance has not appreciably diminished and is still available to pelagic fish. It is presently utilized only by juvenile striped bass, carp, and infrequently by centrarchids.

LIFE HISTORY AND ECOLOGY OF RAINBOW SMELT

Description

The rainbow smelt is a slender, silver fish, pale green on the back with iridescent reflections on the sides. The head is moderately long and eyes moderately large. The fins are generally clear. The soft rayed dorsal is located mid-body with the origin over the origin of the pelvic fins. A well

-28- developed adipose fin is present and the caudal is deeply forked. The cycloid scales are thin and deciduous, lateral line incomplete, and peritoneum silvery with dark speckles. Landlocked smelt often have black pigment on the head and fins. The body is elongate, laterally compressed, with average length 178-203 mm (7-8 in). It has a pointed elongated snout, large mouth and teeth on tongue and vomer (Scott and Crossman 1973).

Smelt landlocked in small lakes often attain a maximum size of 102 mm (4 in), while 356 mm (14 in) individuals have been taken in Lake Ontario and maritime coastal waters. Smelt less than 100 mm (4 in) were considered subadult by Argyle (1982) in Lake Huron. The shortest mature smelt were 127 mm (5 in) in Lake Superior (Bailey 1964). Smelt grew 40-50 mm during the first year (Rupp 1968). The greatest growth increment occurs during the second year prior to sexual maturity (Burbidge 1969). Total length was 117, 155, and 183 mm (4.6, 6.1, and 7.2 in) at age 2,3, and 4, respectively in Lake Huron (Baldwin 1950), and 152, 185, and 201 mm (6, 7.2, and 7.9 in) at the same age in Lake Superior (Bailey 1964).

Distribution

The original range of the Atlantic rainbow smelt appears to be restricted to the Atlantic coast between Labrador and New Jersey. Indigenous landlocked smelt occurred in many New England and eastern Canadian waters. Smelt were introduced into Lake Michigan in 1906-1912 and subsequently established in the entire Great Lakes complex within a 25 year period (Van Oosten 1937, Dymond 1944, Scott and Crossman 1973, Wichers 1980, Bergstedt 1983). In 1978 smelt were found in the upper Mississippi River drainage, presumably migrating out of Lake Michigan via the Chicago Canal-Illinois River into the Mississippi River. It was felt that smelt would not survive the summer in the Mississippi due to its preference for colder water (Burr and Mayden 1980). Four smelt were collected from the Mississippi River in Louisiana in 1979 some 900 miles downriver from the mouth of the Illinois River. The Mississippi was in flood stage during these collections and fish were suspected to be the result of spawning occurring upriver (Suttkus 1980). Smelt did not establish a population since no recent reports of smelt occurring in the lower Mississippi have been found.

Smelt were introduced into Lake Sakakawea, North Dakota in 1971 and subsequently became established downstream in Lake Oahe, South Dakota (Berard 1978, Burczynski et al. 1985). Smelt are found in down stream impoundments of the Missouri River but they are not found in large numbers in Lewis and Clark and Francis Case Reservoirs, because these waters do not stratify and thereby develop a coldwater zone (G. Marrone, South Dakota Dept. of Game Fish and Parks, personal communication, 1987). They are not established in the Missouri River below these two reservoirs.

During the 1970's and 1980's, Colorado stocked smelt in many small impoundments (Clear Creek Reservoir, Twin Lakes, Turquoise Lake, Pueblo Reservoir, Quincy Reservoir, Rampart Reservoir, and Horsetooth Reservoir) as a forage species (Goettl 1983, Goettl and Jones 1984, Sinley 1979). Smelt were also stocked by Nebraska in Lake McConaughy, 1983-85, as forage for trout and striped bass. To date, successful recruitment of smelt has not been

-29- documented in Lake McConaughy possibly due to severe thermal and oxygen stratification in this eutrophic, turbid reservoir on the North Platte River (D. Ellison, Nebraska Game and Parks, personal communication, 1987).

South Dakota introduced smelt as forage for brown trout (Salmo trutta) in Pactola Reservoir in the Black Hills in 1982. Smelt were intended to buffer brown trout predation of stocked rainbow (Oncorhynchus mykiss) and also provide food for cutthroat (Oncorhynchus clarkii). Smelt reproduction has been documented but the population has not fully. developed (R. Ford, So. Dakota Game, Fish and Parks, personal communication, 1987).

Habitat

Smelt are schooling, pelagic fishes, inhabiting midwaters of lakes or inshore coastal waters. They do not inhabit streams or rivers except at spawning time. They are sensitive to light and temperature (Scott and Crossman 1973). Smelt occupied the colder water of Lake Oahe, concentrating within or immediately below the thermocline. There was a tendency for smaller fish to be distributed somewhat shallower than the larger fish (Burczynski et al. 1985). Smelt were most often found in the hypolimnion at temperatures of 5-14 C. During the day most smelt were within several meters of the bottom but moved upward to the thermocline at night (Burczynski et al. 1987). In Lake Sakakawea smelt suspend in 27-38 m (90-125 ft) during the summer (Berard 1978). In the Great Lakes smelt inhabit water temperatures of 6-16 C during the summer (Ferguson 1965, Wells 1968, Heist and Swenson 1983). Adult smelt in Lake Michigan occurred at 7-8 C during the day and 11-16 C at night. Larval smelt preferred 13-14 C during the day and 5-6 C at night (Brandt et al. 1980). A thermal preference of 12.8 C was documented in Lake Champlain, and smelt preferred 6.6-8.3 C in Cayuga Lake, NY (Burbidge 1969).

Smelt avoid water temperatures higher than 15 C except for periodic ventures into surface waters (Rupp 1959). Smelt were not found in Lake Oahe where no hypolimnion existed and bottom waters exceeded 20 C. In Kennedy Lake, NY, the midsummer distribution of smelt was restricted to the hypolimnion where temperatures were less than 13 C. Thermal preference effectively separated fish populations and reduced predation and competition between smelt and yoy game fish (Johnson 1963). In Lake Michigan, smelt move in increasing numbers from a pelagic existence to a bottom existence as they grow older and inhabit the temperature zone of 6-14 C (Wells 1968). Smelt cannot survive water temperatures in excess of 21-26 C (Wichers 1980).

Spawning

Smelt are typically anadromous fish that spawn in the spring. Like many anadromous fish, they can live successfully in freshwater and have adapted to many varying habitats. Smelt generally ascend into the mouths of streams not long after ice out, usually in March-May, depending on temperature and weather (Scott and Crossman 1973). Smelt rarely ascend streams more than a quarter mile and usually stop at the first falls which has a drop of over one foot (Baldwin 1950). At Cold Creek, Michigan, smelt did not ascend above a zone of rapids within the lowermost six hundred feet of a creek (Langlois 1935). In the Great Lakes spawning occurs in the mouths of streams and within the lake on gravel shoals. Mean survival of fry from shore spawning and stream spawning were similar. Smelt hatched from stream spawning populations

-30- immediately adapted to shore spawning in a host lake where tributaries were absent (Rupp 1965). Smelt from Lake Champlain, New York, spawned in fairly deep water and did not ascend streams or shallow shoreline areas for spawning (Halnon 1963). Spawning substrate type may not affect survival from egg to sac fry stage (Hulbert 1974).

Spawning has been documented at temperatures ranging between 2-18.3 C (Hoover 1936, Scott and Crossman 1973). Smelt spawning runs were initiated at 4.5 C and peak spawning occurred at 6.1 C in Quabbin Reservoir, Mass. (Hambly 1972). Spawning may last for 3 weeks but the peak is seldom longer than a week. The composition of the spawning population is primarily males at the start, equal numbers of each sex during the peak, and primarily females in the latter portion (Jilek et al. 1979). Spawning takes place at night with spawners returning to the lake by day. Male smelt are covered with nuptial tubercles and can easily be separated from spawning females which feel smooth to the touch (Hoover 1936). Two or more tuberculated males maintain positions against a female while eggs and milt are released simultaneously. The eggs are broadcast over the bottom and quickly adhere to the substrate by a short pedicel formed from the outer shell membrane (Rupp 1965). Individual female smelt produce an average of 25,000 eggs with a range of 10,000-43,000 (Baldwin 1950, Bailey 1964, Langlois 1935). Average production per square foot of substrate in Dean Brook, Maine was 5,762 eggs and 32 prolarvae (Rothschild 1961).

Incubation is 10-60 days depending on water temperature (Rupp 1968). Cooper (1978) found that smelt eggs hatch in 8-29 days at temperatures of 4.4-21 C. Eggs hatched between 183 and 195 hours after fertilization at an average water temperature of 16.5 C. Unfertilized eggs are 0.8-0.9 mm and swell to 1.0 mm after fertilization and water hardening. Egg survival to prolarvae was 1-2% in Maine waters (Rothschild 1961, Rupp 1968). Smelt mature during their second or third growing season. Among two year old smelt in Lake Superior 41% of the males and 18% of females were mature. All smelt older than two years were mature. Shortest smelt to reach maturity were 127 mm in Lake Superior (Bailey 1964). Most investigators have found that smelt spawning runs are dominated by 2 year old fish (McKenzie 1958, Van Oosten 1940, Baldwin 1950).

Food Habits

Food studies show that smelt feed mainly on plankton, amphipods, and invertebrate insects but also prey on small cohabitating fishes, including their own young (Hale 1960, Price 1963, O'Gorman 1974). In contrast, studies in New Hampshire (Hoover 1936), Green Bay (Schneberger 1937), Lake Huron (Baldwin 1950, Gordon 1961), and Lake Erie (Ferguson 1965) indicated that smelt seldom ate fish, but fed primarily on zooplankton and bottom fauna. Van Oosten (1953) summarized "... nowhere have investigators found (game and commercial fishes) present in the stomachs of smelt in any significant quantities". Further, Gordon (1961) concluded that smelt in Lake Huron were probably not serious competitors or predators. Studies elsewhere have not demonstrated that smelt are an important predator of fishes (Creaser 1925, 1927; Kendall 1927; Greene 1930; Rupp 1968; Burbidge 1969; Lackey 1969; Anderson and Smith 1971; Selgeby et al. 1978). MacCrimmon and Pugsley (1979) concluded that "there is no evidence from any study that any segment of the smelt population becomes totally piscivorous, either on a seasonal or

-31- permanent basis; or that smelt predation is an obvious factor in the suppression of any sympatric population."

Smelt are opportunistic feeders that feed on small, deepwater organisms as available. Amphipods dominated the diet of smelt in Maine waters (Flagg 1971). Smelt smaller than 180 mm (7 in) ate Mysis while larger smelt primarily ate Mysis and small alewives (Alosa pseudoharengus) in Lake Michigan. Smelt longer than 180 mm (7 in) ate three times more fish than smaller individuals. The smallest smelt to consume an alewife was 157 mm (6 in) (Foltz and Norden 1977). O'Gorman (1974) found the smallest piscivorous smelt to be 143 mm (5.6 in) and these smelt consumed fish that averaged 56 mm (2.2 in) in total length (TL). Smelt examined by Foltz and Norden (1977) in Lake Michigan fed little in the winter and ceased to feed during spawning.

Smelt used copepods, Daphnia, midge and Hexagenia larvae in West Bearskin and Devilfish Lakes, Minnesota (Hassinger 1971). Lake Huron smelt relied mainly on Mysis, but also consumed mayfly, caddis fly and ostracods (Baldwin 1950). Gordon (1961) found Lake Huron smelt to eat copepods, cladocerans, insects and fish. Copepods and cladocerans were the most important food items in Gull Lake, Michigan (Burbidge 1969), Lake Michigan (Crowder et al. 1981), Lake Huron (Reckahn 1970), inland lakes in Minnesota (Hassinger 1970, 1972, Johnson 1963), inland waters of Maine (Rupp 1968), Rampart and Quincy Reservoirs in Colorado (Goettl 1983, Goettl and Jones 1984) and the Mississippi River (Burr and Mayden 1980). Smelt fed mainly on zooplankton in Maine, but also used insects and isopods (Lackey 1969). Zooplankton was the major food item in Lake Simco, Ontario (MacCrimmon and Pugsley 1979). The large cladoceran, Leptodora kindtii, was important in the diet in Lake Sakakawea, North Dakota, (Power 1984) and Lake Oahe, South Dakota (Schmulbach et al. 1983). Calanoid copepods were the dominant food of smelt in Lake Superior (Siefert 1972). Cayuga Lake, New York, smelt mainly ate Mysis relicta and Pontoporeia affinis (Youngs and Oglesby 1972).

Both rainbow smelt and alewives may cause a restructuring of the plankton communities by eliminating larger species of zooplankton and thereby allowing an increase in algal blooms (Kircheis and Stanley 1981, Mills and Schiavone 1982). Rainbow smelt in Lake Oahe, South Dakota, were found to be "selective planktivores" that preferred larger zooplankters when available (Schmulbach et al. 1983).

Disease Potential

Smelt readily adapt to a new environment and can be introduced with spawning adults, egg transfers or a combination of both. Spawning adults would be the preferred method of introduction. Smelt are host to a number of parasites, particularly Glugea hertwigi, an aesthetically undesirable parasite which forms white cysts inside the body cavity (Scott and Crossman 1973).

Examinations of spawning smelt from Lake Oahe, South Dakota, by both Utah and South Dakota show these fish to be free of the above mentioned parasites. Histological testing of smelt by Utah's fish pathology staff have failed to detect any prohibited pathogens. These investigations will continue. If parasites of concern are found in the future, an introduction of fertilized eggs would be used instead of adult stocking to avoid transfer of the parasite.

-32- Hybridization

There is no potential for hybridization of smelt with any other species of fish presently occurring in the Colorado River system.

Smelt As Forage

The value of rainbow smelt as a forage fish has been well documented. It is widely used for food by lake trout (Salvelinus namavcush), other trouts, and salmon species and often makes up the majority of their diets (Hassinger 1970, 1971, 1972; Hassinger and Close 1984; Lackey 1969; Goettl and Jones 1984; McCaig and Mullan 1960; Speirs 1972; Stewart et al. 1981). Introductions of smelt into various waters for forage have resulted in increased growth and numbers of game species such as trout and salmon (Hambly 1972, Hassinger and Close 1984, Havey 1973), walleye, pickerel (Esox sop.), northern pike (Esox lucius) (Berard 1978, Marrone 1987, McCaig and Mullan 1960) and both smallmouth (Microoterus dolomieui) and largemouth bass (Micropterus salmoides) (McCaig and Mullan 1960, Bridges and Hambly 1971, Goettl and Jones 1984).

The occurrence of striped bass together with rainbow smelt in freshwater lakes and impoundments is rare. Striped bass exist with introduced rainbow smelt in Lake McConaughy, Nebraska, however, the recently introduced smelt have not yet become established (Ellison, D., Nebraska Game and Parks, personal communication, 1987). Striped bass coevolved with smelt in their original range in the North Atlantic and utilize smelt in New England coastal waters (Flagg et al. 1976). Alewives, which occupy nearly identical habitats to smelt, have been found to be valuable forage in several landlocked lakes in the eastern U. S. (Moore et al. 1985, Speirs 1972, Strange et al. 1985, Vincent 1960, Rothschild 1965). Alewives rapidly became the dominant food item in striped bass stomachs after their introduction as forage in Smith Mountain Lake, Virginia (Moore et al. 1985). Alewives were separated spatially and temporally from gizzard shad in Smith Mountain Lake, Virginia, and the two species were found to peacefully coexist without negative impacts (Tisa et al. 1985).

Expected Behavior of Smelt in Lake Powell

Rainbow smelt in Lake Powell would be expected to spawn in February or March at about the same time that walleye presently spawn. Water surface temperatures would be at the yearly minimum (between 7-12 C) just prior to spring warming. Adult smelt would move into the shallows and spawn on the ubiquitous talus rockslides that comprise much of Lake Powell's 2930 km (1820 ml) shoreline. Some smelt would be attracted to the tributaries by the current but silt bars guarding the San Juan and Escalante Rivers would limit upstream movement. Smelt would run into the Colorado River to the base of the first rapid in Cataract Canyon. Bottom substrate in this area is composed of fine silt which would limit survival of yoy. Most successful reproduction would occur within the lake.

Some overlap of habitats of adult rainbow smelt and walleye fry is expected. Smelt may limit recruitment of walleye. The smelt spawning run would last about 3 weeks with most spawning occurring within a one week period. Larval smelt hatch in about 10 days at 12 C. Most smelt would be hatched by the end of March. Larval smelt are light sensitive and would be

-33- forced deep during the day. They would return to shallow water at night where they would forage on plankton.

Adult smelt would be forced out of the shallows by warming temperatures in early April. Adult smelt avoid temperatures above 15 C, which is the minimum temperature required for centrachid spawning in Lake Powell. Predaceous smelt would not be in the shallows at the same time larval bass, crappie, or sunfish would be emerging. Larval centrarchids use the shallow, warm water (19-27 C) as nursery areas. Larval smelt on the other hand still prefer water less than 14 C suggesting partitioning of yoy smelt and yoy gamefish.

Shad spawn when early morning water temperatures reach 20.5 C, normally in mid May. Shad then remain in the upper 10 m (30 ft) during the summer. Shad and adult smelt would be separated by the thermocline. Yoy smelt are more temperature tolerant and may interact with shad at the thermocline. In Lake Powell, however, shad are currently using warm shallow water at the backs of the canyons. There is no open water shad population. Smelt will initially be able to utilize pelagic plankton which is currently used only by juvenile striped bass. If smelt buffer the predation on shad as expected, the shad population will gradually increase and again occupy the open water. As the open water shad population increases, adult shad and smelt will share the plankton resource at the thermocline.

Cooling temperatures in the fall begin to break down lake stratification by November. Smelt will then be free to interact with all species. By this time striped bass predation will have reduced the annual smelt crop to a smaller number which will overwinter by retreating to the depths to avoid predation. The yoy of most species (all except bluegill, green sunfish and the youngest shad) will be larger than can be consumed by adult smelt. Shad and smelt may interact at this time but larger shad will be too large to be eaten, thus ensuring that shad broodstock is available to spawn the following year.

Predation on larval fishes is a concern since smelt will eat small fish and eggs when available. Fortunately, smelt will be partitioned by temperature in the stratified reservoir from larval shad and game fish (except perhaps striped bass fry). YOY gamefish will be in the shallows while piscivorous smelt will be below the thermocline, which may be 60-100 feet deep. Some interaction of smelt and yoy game fish will occur during winter after yoy game fish have grown large enough to evade smelt predation (greater than 80 mm). Smelt have also been shown to eat very little in the winter (Foltz and Norden 1977). Smelt most often eat their own young because that is what is available in offshore deepwater areas.

Competition with other species that consume large plankton may be a problem since smelt may reduce the abundance of large plankters. Some dietary overlap will occur between shad, yoy game fish and smelt. In years when both forage species are abundant, plankton will be utilized to its fullest potential. Presently, pelagic plankton populations are utilized only by striped bass. Smelt introduction would cause a more efficient cycling of nutrients.

-34- Smelt will not migrate up streams that possess falls of 1 foot or greater (Baldwin 1950). They are not strong swimmers and seldom go upstream more than a quarter mile (Langlois 1935). They are not normally found in warm, silty water, which is characteristic of Colorado River tributaries during summer flows. It is, therefore, very unlikely that smelt will move upstream from Lake Powell in the Colorado or San Juan Rivers or any of the major tributaries of the lower Colorado River.

Downstream migration of smelt is expected. Smelt colonized the Missouri River system within 8 years of introduction (Wichers 1980). Smelt presence in tailwaters has been beneficial to trout fisheries in the Missouri River system (Art Talsma, So. Dakota Dept. of Game Fish and Parks, personal communication). Smelt pass through tailwaters but do not establish reproducing populations. Smelt will likely establish populations in Lake Mead and Lake Mohave. The lack of development of a strong thermocline may prevent smelt from completing their life cycle in Lake Havasu. They are not likely to be found in the river below Lake Havasu.

THREATENED AND ENDANGERED SPECIES

Of the many variables affecting distribution of endemic fishes in the Colorado River, water temperature seems to be the most important. Water temperature has been considered the major cause of extirpation of native fishes from regulated portions of the river (Holden and Stalnaker 1975, Behnke and Benson 1980). Bulkley and Pimentel (1983) attributed the disappearance of razorback sucker (Xyrauchen texanus) and three endangered species from the Green River, Utah, to a decline in mean water temperature (from 18 C to 6.8 C) following the construction of Flaming Gorge Dam. Alteration of discharge and temperature regimes downstream from dams and diversions, conversions of riverine ecosystems to lacustrine, introduction of non-native fishes and altered water quality have also hastened the decline of native fishes (Miller 1961, Minckley and Deacon 1968). Declining populations of "big river" fishes indicate that the current river environment is not conducive to their survival.

Humpback Chub

A remnant population of humpback chub (Gila cvpha) remains in the lower basin of the Colorado River centered around the Little Colorado River and four locations in the upper basin (Valdez and Clemmer 1982). Adult humpback chub were captured in the Glen Canyon tailrace in 1967 (Suttkus and Clemmer 1977) but have not been found in the tailrace recently (Maddux et al. 1987). Displacement of native fishes from cold, clear western tailwaters is common (Vanicek et al. 1970).

Maddux et al. (1987) found most humpback chub confined to the Little Colorado River and backwaters 97 km (60 mi) and further below Glen Canyon Dam in waters that were warmer than the main channel of the Colorado River. Juvenile humpback chub were found in water averaging 15.2 C while the main channel temperature was 10-11 C.

Humpback chub spawning occurs Mar-Jun when water temperatures are 16-20 C (Suttkus and Clemmer 1977, Carothers et al. 1981, Minckley et al. 1981,

-35- Kaeding and Zimmerman 1983). Colorado River main channel temperatures near 11 C during this time may not be warm enough to even initiate spawning (Maddux et al. 1987). The Little Colorado River is generally 9 C warmer than the main channel (Kaeding and Zimmerman 1983). If spawning did occur in the main channel or if humpback chub fry were flushed into the main channel the exposure to 11 C temperatures may be lethal (Hamman 1982, Maddux et al. 1987).

The Little Colorado River is unquestionably the most important tributary for the continued existence of humpback chub in the Colorado River system.

Maddux et al. (1987) found most yoy humpback chub less than 80 mm (3 in) restricted to the Little Colorado River. Although Maddux et al. (1987) found native larval fishes in main channel habitats, humpback chub larvae were conspicuously absent. During a typical year humpback chub spawning is triggered by water temperatures near 19 C (Hamman 1982, Maddux et al. 1987). Rainbow smelt avoid temperatures in excess of 15 C (Rupp 1959) and die at 21 C (Wichers 1980). Rainbow smelt will not, therefore, be found in proximity of spawning adult or larval humpback chub. Larval humpback chub exposed to main channel temperatures (suitable to smelt) would be lost due to temperature shock (Hamman 1982).

Yoy humpback chub spend their first summer and fall in the warm tributaries and grow to about 70 mm (3 in) during the first year. As the Little Colorado River cools in October yoy chubs migrate out to the main Colorado River (Maddux et al. 1987). Smelt generally ingest fish smaller than 56 mm (2 in)(0'Gorman 1974). It is highly unlikely that smelt and yoy humpback chub will occupy waters of the same temperature while humpback chub fry are still small enough for smelt to eat.

Some overlap of habitat requirements for smelt and humpback chub may occur at the mixing zone of the Little Colorado River and Colorado River. High flows in the Colorado result in a ponding effect at the mouth of the Little Colorado River. Low flows would separate habitats of smelt and humpback chubs. Competition for food and space between the two species will be minimal. Fortunately, humpback chub in this area are normally large enough to avoid predation. Maddux et al. (1987) speculated that increased turbidity in three major tributaries, including the Little Colorado River, would separate habitats of native and non-native fishes and thereby reduce predation on native fishes. Rainbow smelt were made more available to predators in turbid waters (Swenson and Matson 1976). Smelt have been found to preferentially eat amphipods (Flagg 1971) such as Gammarus that are abundant at the confluence. Humpback chub at this location did not eat Gammarus but preferred chironomids, simulids and fish (Kaeding and Zimmerman 1983). It is possible that smelt may provide an additional food item for omnivorous adult humpback chub. Competition for food and space between native fish and invading exotics that occupy the same habitat [such as red shiner (Notropis lutrensis) and fathead minnow (Pimephales promelas)] is a major threat to imperiled yoy. Smelt will be thermally separated from native fish larvae and will not increase the competition that currently exists between the fish living in warmer water. Wichers (1980) states that in general, potential consequences (beneficial or adverse) of a smelt introduction will be less for littoral and warmwater species (such as humpback chub) than for pelagic and coldwater species.

-36- Bonytail Chub

Bonytail chub (Gila robusta) is the rarest of Colorado River native fishes and the nearest to extinction (Behnke and Benson 1980). Bonytail chub are a riverine species that has been precluded from using riverine Colorado river habitat below Lake Powell by cold water releases from reservoirs (Colorado River Fishes Recovery team, in press). Individual fish, if captured, are removed and transferred to secure refugia (Marsh, AZ State Univ, personal communication 1989). Restoration by stocking may be the only means of maintaining bonytail chub in the Colorado River basin (U. S. Fish and Wildlife Service 1987, Bozek et al. 1984).

Bonytail chub stocked at a total length greater than 80 mm (3 in) would not be in danger of predation from smelt. Bonytail chub are a sedentary insectivore with a 20 C preferred temperature (Valdez and Clemmer 1982). Bonytail chub would be the least likely native species to be in competition or in danger of predation by cold-water, planktivorous rainbow smelt. Recovery efforts to reestablish bonytail chub would place chubs in warmwater habitats where smelt could not survive.

Razorback Sucker

Razorback suckers have weathered the impoundment and control of the Colorado River better than bonytail chubs and humpback chubs but their populations have still declined. A remnant but static population exists in Lake Mohave and other sites in the lower basin. Minckley (1983) speculates that the razorback sucker in Lake Mohave are old adults (30+ years) which will eventually die out. Others suggest that since the population is statistically as abundant in 1988 as it was in 1975 (W. Minckley, AZ State Univ, personal communication 1988), limited recruitment of razorback suckers presently occurs in Lake Mohave (Bozek et al. 1984; Burrell, NV Dept. Wildlife, personal communication 1988).

Bulkley and Pimentel (1983) found razorback suckers to prefer a temperature of 23 C. The preferred temperature of razorback is above the lethal temperature range of smelt. Adult smelt and razorback suckers will select different temperature strata in Lake Mohave. Yoy smelt and razorback suckers also prefer different temperatures.

Spawning has been reported to occur at 14-18 C in Lake Havasu (Douglas 1952) and 12-18 C in Lake Mead (Jonez and Sumner 1954). Spawning occurred at 12-16 C in the Yampa River (McAda and Wydoski 1980). Razorback sucker in Lake Mohave have been observed spawning from Nov-May at temperatures of 10-15 C over shallow gravel flats. However, Jonez and Sumner (1954) define the historic spawning period to be 1 March-15 April in Lake Mead and March-July in Lake Mohave.

Minckley (1983) believes that direct predation on ova by carp, channel catfish and centrarchids contributes to the failure of natural reproduction in Lake Mohave. However, Bozek et al. (1984) found razorback ova in a few channel catfish and observed carp feeding on the substrate in spawning areas but found little evidence of extensive predation on the eggs. Bozek et al. (1984) suggested that violent spawning actions of razorbacks deposited eggs deeply into the loose gravel and could have protected most eggs from

-37- predators. Maddux and Kepner (1988) examined stomach contents of carp observed foraging over an active bluehead sucker (Catostomus discobolus) spawning site and found no sucker ova but contained food items dislodged during the spawning act.

Razorback suckers usually select nest sites in water less than 1 m (3 ft) deep. Reservoir drawdown during both winters of 1982 and 1983 allowed desiccation of 70% of sucker redds and would have accounted for most of the mortality that occurred at the egg and larval stages (Bozek et al. 1984). Protolarval and mesolarval razorback sucker were collected in gravel of spawning areas at Lake Mohave, but no older yoy were collected. As razorback sucker grow they remain in the gravel substrate until the late mesolarval stage. Larvae then migrate to another niche.

The fate of razorback sucker larvae is then open to speculation. Bozek et al. (1984) speculated that larvae migrated to dense macrophyte beds of MyriophOlum and Potamogeton that grew at depths of 5-10 m (15-30 ft) along the silty bottom edges of gravel terraces during the summer of 1982. The dense cover of the macrophytes and sedentary behavior of the sucker then allowed survival and recruitment of a limited number of razorback suckers in years when these conditions occurred.

If Bozek et al. (1984) are correct, then smelt and yoy razorback suckers would be in the same life zones during the smelt spawning run. They may possibly use the same spawning gravel. But the same mechanisms that are now protecting razorback suckers from predation will also protect them from smelt. First, adult smelt normally cease feeding during spawning (Foltz and Norden 1977). Second, razorback sucker eggs and larvae would be buried in the gravel where smelt could not directly prey on them. Third, smelt eggs adhere to the gravel by a short pedicel that is formed immediately after fertilization. Fourth, smelt eggs would be available to channel catfish and carp and may buffer razorback eggs from predation.

After spawning is completed, adult smelt would be forced into the depths by increasing water temperatures. Juvenile suckers would remain hidden, first in the gravel and then in macrophytes rendering them unavailable to adult smelt prior to their departure from the spawning areas. Young smelt are not predaceous and would not consume larval suckers. Larval smelt and yoy razorback suckers may compete for plankton but they will be located in the most productive zone of the reservoir at a time when plankton abundance is peaking.

Deacon (personal communication, UNLV, 1989) who is a coauthor of Bozek et al. (1984) states that "extensive research done since that report by Minckley and colleagues at Arizona State University.. .overwhelmingly demonstrate recruitment (of razorback sucker) is highly unlikely to be occurring in Lake Mohave". If this is the case it seems that the hope for recovery of a riverine fish in lacustrine habitat that now exists in Lake Mohave is not possible. The species may be preserved in the lake with a stocking program but recovery of the species in Lake Mohave is unlikely.

-38- Razorback sucker brood stock have performed well in the hatchery growing to 326-456 mm (13-18 in) in 2 years (Bozek et al. 1984). Rainbow smelt introduction should not impact maintenance stocking of razorback suckers. There seems to be adequate productivity and living space for both species.

OTHER ENVIRONMENTAL COMPONENTS

The introduction of rainbow smelt will have no effect on existing flood plains/wetlands, water quality, terrestrial wildlife, prime and/or unique farmland, cultural resources, agriculture, or residential concerns.

SUMMARY AND CONCLUSIONS

Rainbow smelt have been demonstrated to be a valuable forage species in many deep cool water lakes. They tend to occupy pelagic and deep water zones and avoid epilimnetic waters during much of the year. While adult smelt are sometimes predaceous, they would be separated from small game fish (except striped bass) and forage fish by water temperature when the reservoir is stratified. When stratification breaks down young fish of most species have grown to large enough size to avoid predation of adult smelt.

Rainbow smelt meet many of the criteria for a desirable forage fish (Ney 1981). When smelt have been introduced west of the Mississippi they have been prolific, trophically efficient, and vulnerable to predation (Goettl 1983). Smelt and striped bass are coevolved species both originating in North Atlantic coastal waters.

Lake Powell, with its absence of deepwater forage fish, seems to be an excellent choice for rainbow smelt introductions. The hypolimnetic waters of Lake Powell range from 7.0-12 C during the summer (Merritt 1976) and are well within the smelt's preferred temperature range. Crustacean plankton abundance in Lake Powell (Sollberger et al. 1989) is comparable to that found in the Great Lakes where rainbow smelt are established. Rainbow smelt would provide a schooling forage fish that occupies the same strata as walleye and striped bass during the entire year. Adult smelt would be thermally partitioned from shad and yoy gamefish in the stratified reservoir and offer little threat of direct competition for food or space. Smelt flushed downstream below Lake Powell would pass through the riverine portions of the system and possibly establish populations in Lake Mead and Lake Mohave where productivity and striped bass concerns are similar to those in Lake Powell. Rare and endangered endemic fishes would have minimal interaction with smelt and would not face significant competition for food and space.

Rainbow smelt have the potential to become established in Lake Powell despite the over abundance of predators that currently exist. They would provide forage for striped bass and walleye, and potentially allow shad to be utilized by littoral predators. Smelt have proven to be beneficial in the Missouri River system and without significant negative impacts (Schmulbach et al. 1983, G. Marrone, So. Dakota Dept. of Game and Parks, personal communication, 1987). Smelt would seem to be a beneficial addition to the

-39- Colorado River system. They would be found in locations occupied by naturally reproducing striped bass and provide a constant source of forage for the dominant predator in the Colorado River system.

DOCUMENTATION OF CONSULTATIONS

PUBLIC MEETINGS

Striped Bass Committee - Subcommittee of Colorado River Fish and Wildlife Council. Meets annually and reports to Technical Committee. Committee report then presented to full Council meeting as a portion of Technical Committee report. Composed of biologists from UT, AZ, NM, NV, and CA.

1979 - Committee notified of possible striped bass reproduction in Lake Mead and Lake Powell.

1980 - Dramatic decrease in physical condition of striped bass in Lake Mead. Suspected problems developing with forage base.

1982 - Committee opposed to change in nutrient loading of Lake Mead through Vegas Wash sewage effluent because of negative impact on forage base. In- reservoir spawning of striped bass documented in Lake Powell.

1983 - Striped bass forage deficiency identified with subsequent decline in physical condition of striped bass throughout the system - Lake Powell to Lake Havasu. Committee began literature search for possible forage enhancement of Colorado River system.

1984 - Rainbow smelt proposed as possible forage fish for system. South Dakota presented smelt life history in Missouri River system to Committee.

1985 - Nevada and Arizona began joint project to enhance forage base at Lake Mead by fertilization.

1986 - Striped bass creel limits liberalized throughout Colorado River basin to increase harvest of juvenile striped bass. All minimum size limits removed. California confirmed occurrence of in-reservoir striped bass reproduction in Lake Havasu. Nevada proposed stocking trout in Lake Mead to test theory of striped bass forage shortage, instead of stocking exotic forage fish.

1987 - Committee recommended stricter guidelines for introduction of exotic species in the Colorado River.

1988 - Utah submitted formal proposal to introduce rainbow smelt into Lake Powell to enhance the forage base. Majority of voting members opposed introduction. Oklahoma reported on successful striped bass fishery at Lake Texoma where diverse forage base sustains a healthy natural reproducing striped bass population.

1989 - Utah resubmitted revised proposal to introduce rainbow smelt into Lake Powell. Majority of voting members supported the proposed introduction.

-40- COLORADO RIVER FISH AND WILDLIFE COUNCIL

Membership - Wildlife Directors of Basin States, CA, AZ, NM, CO, UT, NV, and WY. Meet annually.

Striped Bass Committee reported above actions to Council each year.

1987 - Council instituted stricter guidelines for introductions of exotic species.

1988 - Rainbow smelt proposed introduction into Lake Powell presented to Council. No action taken due to vote of Technical Committee opposing introduction.

1989 - Technical Committee favorably recommended introduction of smelt into Lake Powell. Council deferred action until proposal given Environmental Assessment type public review.

OTHER PUBLIC MEETINGS

August 21, 1987 - Smelt proposal presented to Utah State Legislative committee representatives at Bullfrog, Lake Powell, UT. Committee endorsed concept.

October 1987 - Utah Bass Federation meeting in Salt Lake City. Smelt proposal presented, bass clubs asked to help restrain members from taking any illegal action on their own. Clubs accepted suggestion. They would be willing to wait for DWR to proceed through required channels.

January 11, 1988 - Smelt proposal presentated to Utah Wildlife Board in Salt Lake City at regularly scheduled public meeting. Board endorsed concept.

January 15, 1988 - Smelt proposal sent to media in Utah, Arizona, Nevada, and California for public information. News releases appeared in newspapers, magazines, and television in the four states.

April 16, 1988 - Smelt presentation to Tri-State Commission (Wildlife Commissions from California, Nevada, and Arizona) at Bullhead City, AZ. Commissioners deferred action pending outcome of CRFWC decision making process.

January 1989 - Utah's annual public meetings to discuss the fishing proclamation addressed Lake Powell, notified public of problem and expected action. Anglers were asked to be patient while preliminary research was conducted to determine advisability of smelt transplant.

December 1989 - Meeting with Utah Bass Federation. Progress on forage enhancement of Lake Powell explained. Members cautioned to be patient while debate over smelt introduction continues.

-41- FEDERAL AGENCY CONSULTATION

Sept 1989 - FWS Region 6 - Denver Smelt proposal presentated to Region 6 staff who suggested giving more attention to alternatives before proceeding with the smelt introduction. EA type review recommended.

November 1989 - FWS Region 2, National Park Service Glen Canyon National Recreation Area - Page, Arizona Smelt proposal presented to Region 2 and Glen Canyon National Recreation Area staff who opposed any introduction of fish into the Colorado River system. Suggested working with the species that currently exist in the system and educating anglers to learn to accept the fisheries that are presently available.

-42- LITERATURE CITED

Anderson, E. D. and L. L. Smith, Jr. 1971. Factors affecting abundance of lake herring (Coregonus artedii) in western Lake Superior. Trans. Am. Fish. Soc. 100(4):691-707.

Argyle, R. L. 1982. Alewives and rainbow smelt in Lake Huron: midwater and bottom aggregations and estimates of standing stocks. Trans. Am. Fish. Soc. 111:267-285.

Bailey, M.M. 1964. Age, growth, maturity, and sex composition of the American smelt, (Osmerus mordax), of western Lake Superior. Trans. Am. Fish. Soc. 93:382-395.

Baldwin, N. S. 1950. The american smelt, (Osmerus mordax), of South Bay, Manitoulin Island, Lake Huron. Trans. Am. Fish. Soc. 78:176-180.

Behnke, R. J. and D. E. Benson. 1980. Endangered and threatened fishes of the Upper Colorado River Basin. Extension Service Bulletin 503A, Colorado State Univ. Ft. Collins, CO.

Berard, E. E. 1978. Investigate the influence of smelt on the walleye population in Lake Sakakawea. D. J. Report F-2-R-25 VI. North Dakota Fish and Game Dept. Rept. No. A-1055

Bergstedt, R. A. 1983. Origins of rainbow smelt in Lake Ontario. J. Great Lakes Res. 9(4):582-583.

Bozek, M. A., L. J. Paulson, and J. E. Deacon. 1984. Factors affecting reproductive success of bonytail chubs and razorback suckers in Lake Mohave. Tech. Rept. No. 12. USFWS Contract No. 14-16-0002-81-251. Un. Las Vegas.

Brandt, S. B., J. J. Magnuson and L. B. Crowder. 1980. Thermal habitat partitioning by fishes in Lake Michigan. Can. J. Fish and Aquatic Science 37(10):1557-1564.

Bridges, C. H. and L. S. Hambly. 1971. A summary of 18 years of salmonid management at Quabbin Reservoir, Mass. In: Reservoir Fisheries and Limnology. G. E. Hall (ed). American Fisheries Society Special Pub. No. 8:243-254.

Bulkley, R. V. and P. Pimental. 1983. Temperature preference and avoidance by adult razorback suckers. Trans. Am. Fish. Soc. 112:601-607.

Burbidge, R.G. 1969. Age, growth, length-weight relationship, sex ratio, and food habits of smelt (Osmerus mordax) from Gull lake Michigan. Trans. Am. Fish. Soc. 98:631-640.

Burczynski, J. J., G. M. Marrone and P. H. Michaletz. 1985. Echo surveys on Lake Oahe for rainbow smelt abundance estimation July 1983 and 1984. Biosonics Inc., 4520 Union Bay Place N. E. Seattle, WA 98105. 89 pp.

-43- Burczynski, J. J., P. H. Michaletz, and G. M. Marrone. 1987. Hydroacoustic assessment of the abundance and distribution of rainbow smelt in Lake Oahe. N. Am Jour. Fish Management 7:106-116.

Burr, B. M. and R. L. Mayden. 1980. Dispersal of rainbow smelt, (Osmerus mordax), into the upper Mississippi River. American Midland Naturalist 104:198-201.

Bureau of Reclamation. 1988. Glen Canyon Environmental Studies. Upper Colorado Region. Salt Lake City.

Carothers, S. W., N. H. Goldberg, G. G. Hardwick, R. Harrison, G. W. Hofknecht, J. W. Jordan, C. 0. Minckley, and H. D. Usher. 1981. A survey of the fishes, aquatic invertebrates and aquatic plants of the Colorado River and selected tributaries from Lee's Ferry to Separation Rapids. Final Rept. to Water and Power Resources Service, Contract No. 7-07-30-X0026. Museum of Northern AZ, Flagstaff, AZ.

Cooper, J. E. 1978. Identification of eggs, larvae, and juveniles the rainbow smelt (Osmerus mordax) with comparisons to larval alewife (Alosa pseudoharengus) and gizzard shad (Dorosoma cuedianum). Trans. Am. Fish. Soc. 107:56-62.

Creaser, C. W. 1925. The establishment of the atlantic smelt in the upper waters of the Great Lakes. Papers Mich. Acad. Arts and Letters 5:405-424.

. 1927. The food of the yearling smelt from Michigan. Papers Mich. Acad. Arts and Letters 10:427-431.

Crowder, L. B., J. J. Magnuson and S. B. Brandt. 1981. Complementarity in the use of food and thermal habitat by Lake Michigan fishes. Can. J. Fish and Aquatic Sci. 38(6):662-668.

Douglas, P. A. 1952. Notes on the spawning of the humpback sucker (Xyrauchen texanus). Cal. Fish and Game 38(2):149-155.

Dreyer, R. and W. R. Persons. 1986. Review of potential forage fish introductions for Lake Mead. D. J. Report F-14-R-14. Arizona Game and Fish Dept. 32 pp.

Dymond, J. R. 1944. Spread of the smelt (Osmerus mordax) in the Canadian waters of the Great Lakes. Canadian Field Naturalist 58:12-14 .

Ferguson, R. G. 1965. Bathymetric distribution of American smelt (Osmerus mordax) in Lake Erie. Great Lakes Res. Div., Pub. No. 13. Univ. Michigan. p 47-60.

Flagg, L. N. 1971. Striped bass and smelt survey. Proj. AFS-4-4. Maine Dept. of Marine Resources, Final Rept.

. 1984. Evaluation of anadromous fish resources. Project AFS-21-R. Maine Dept. of Marine Resources.

-44- Flagg, L. N., T.S. Squires, and L. Austin. 1976. Striped bass management plan. Maine Dept. Marine Res. Completion Rept. Proj. No. AFSC-13/FWAC-2, Segments 22 and 24. 29 pp.

Foltz, J. W. and C. R. Norden. 1977. Food habits and feeding chronology of rainbow smelt, (Osmerus mordax), in Lake Michigan. NOAA Fish. Bull. 75(3):637-640.

Goettl, J. P. Jr. 1983. Evaluation of fish forage organisms. D. J. Report F-53-R. Colorado Div. of Wildlife.

Goettl, J. P. and M. S. Jones. 1984. Evaluation of fish forage organisms. D. J. Report F-53-R. Colorado Div. of Wildlife.

Gordon, W. C. 1961. Food of the American smelt in Saginaw Bay, Lake Huron. Trans. Am. Fish. Soc. 90(4):439-443.

Greene, C. W. 1930. The smelts of Lake Champlain. In: A Biological survey of the Champlain watershed. Supp. to 19th Ann. Rept., N. Y. Cons. Dept.

Gustaveson, A. W., T. D. Pettengill, J. E. Johnson and J. R. Wahl. 1984. Evidence of in-reservoir spawning of striped bass in Lake Powell, UT-AZ. North American Journal of Fisheries Management 4:540-546.

Gustaveson, A.W., B.L. Bonebrake, S.J. Scott and J.E. Johnson. 1985. Lake Powell fisheries investigations. 5-year Completion and 1984 Annual Performance Report. Dingell-Johnson Project F-28-R. Pub. No. 85-12. Utah Division of Wildlife Resources. Salt Lake City. 73 pp.

Gustaveson, A. W., B. L. Bonebrake, K.Christopherson, J. E. Johnson. 1988. Lake Powell Fisheries Investigations. 1987 Annual Performance Report. Dingell-Johnson Project F-46-R. Utah Division of Wildlife Resources. Salt Lake City. 29 pp.

Gustaveson, A. W., B. L. Bonebrake, and K. Christopherson. 1989. Lake Powell Fisheries Investigations. 1988 Annual Performance Report. Dingell Johnson Project F-46-R-4. Utah Division of Wildlife Resources. Salt Lake City. 35 pp.

Hadley, W.F. 1982. Draft environmental impact statement on the proposed introduction of forage fish into Fort Peck Reservoir. Montana Dept. Fish, Wildlife and Parks. 30 pp.

Hale, J. G. 1960. Some aspects of the life history of the smelt (Osmerus mordax) in western Lake Superior. In: C. R. Burrows and A. B. Erickson, eds. Minnesota Fish and Game Investigations. Minn Dept. Cons., Div. Fish and Game, Sect. Res. Plan. Fish. Ser. No. 2:25-41.

Halnon, L. C. 1963. Historical survey of Lake Champlain's fishery. D. J. Proj. F-1-R-10, Job No. 6. New York Fish and Game. 94 pp.

Hambly. 1972. Quabbin Reservoir smelt study. D. J. Proj. F-36-R-4. Massachusetts Div. of Fisheries and Game.

-45- Hamman, R. L. 1982. Spawning and culture of humpback chub. Prog. Fish-Cult 44:213-216.

Hassinger, R. 1970. Evaluation of the role of smelt in inland lake trout lakes. D. J. Prog. Rept. No. F-26-R-1. Minnesota Div. of Fisheries and Wildlife.

. 1971. Examination of stomach contents of lake trout and smelt from West Bearskin and Devilfish Lakes. D.J. Proj. F-26-R-2. Minnesota Div. of Fisheries and Wildlife.

. 1972. Examination of stomach contents of lake trout and smelt from West Bearskin and Devilfish Lake, Minn. D. J. Rept. F-26R- 3. Minnesota Div. of Fisheries and Wildlife.

Hassinger, R. L. and T. L. Close. 1984. Interactions of lake trout and rainbow smelt in two northeastern Minnesota lakes. D. J. Proj. F-26-R. Minnesota Div. of Fisheries and Wildlife. 40 pp.

Havey, K. A. 1973. Effects of a smelt introduction on growth of landlocked salmon at Schoodic Lake, Maine. Trans. Am. Fish. Soc. 102:392-397.

Heist, B. G. and W. A. Swenson. 1983. Distribution and abundance of rainbow smelt in western Lake Superior as determined from acoustic sampling. J. Great Lakes Research 9:343-353.

Hepworth, D. K., and S. P. Gloss. 1976. Food habits and age-growth of walleye in Lake Powell, UT-AZ, with reference to introduction of threadfin shad. Utah Division of Wildlife Resources. Pub. No. 76-15. 13 pp.

Hepworth, D. K., and T. D. Pettengill. 1980. Age and growth of largemouth bass and black crappie in Lake Powell, UT-AZ, with reference to threadfin shad introduction. Utah Division of Wildlife Resources. Pub. No. 80-22. 20 pp.

Holden, P. B. and C. B. Stalnaker. 1975. Distribution and abundance of mainstream fishes of the middle and upper Colorado River basins, 1967- 1973. Trans. Am. Fish. Soc. 104:217-231.

Hoover, E. E. 1936. The spawning activities of freshwater smelt, with special reference to the sex ratio. Copeia 85-91.

Hulbert, P. J. 1974. Factors affecting spawning site selection and hatching success in anadromous rainbow smelt (Osmerus mordax). M. S. Thesis. Univ. of Maine, Orono, 44 pp.

Jilek, R., B. Cassell, D. Peace, Y. Garya, L. Riley, and T. Siewart. 1979. Spawning population dynamics of smelt, (Osmerus mordax). J. Fish. Biology 15:31-35.

-46- Johnson, F. 1963. The status of the smelt, (Osmerus mordax), and native fish populations in Kennedy Lake, Itasca County, four years after the first appearance of smelt. Minnesota Dept. of Conservation Investigational Report 272.

Johnson, N. M. and D. H. Merritt. 1979. Convective and advective circulation of Lake Powell, UT-AZ, during 1972-1975. Water Resources Research 15:873-884.

Jonez, A. and R. C. Sumner. 1954. Lake Mead and Mohave Investigations. DJ Project F-1-R. Nevada Fish and Game Commission. 186 pp.

Kaeding, L. R. and M. A. Zimmerman. 1983. Life history and ecology of the humpback chub in the Little Colorado and Colorado Rivers of the Grand Canyon. Trans. Am. Fish. Soc. 112:577-594.

Kendall, W. C. 1927. The smelts. Bull U. S. Bur. Fisheries 42:217-375.

Kircheis, F. W., and J. G. Stanley. 1981. Theory and practice of forage fish management in New England. Trans. Am. Fish. Soc. 110(6):729-737.

Lackey, R. T. 1969. Food interrelationships of salmon, trout, alewives and smelt in a Maine lake. Trans. Am. Fish. Soc. 98:641-646.

Langlois, T. H. 1935. Notes on the spawning habits of the American smelt. Copeia(3)141-142.

Lanteigne, J., and D. E. McAllister. 1983. The pygmy smelt, Osmerus spectrum Cope, 1870, a forgotten sibling species of eastern North American fish. National Museum of Natural Science. Syllogeus No. 45. Ottawa, Canada

MacCrimmon, H. R. and R. W. Pugsley. 1979. Food and feeding of the rainbow smelt (Osmerus mordax) in Lake Simcoe, Ontario. Canadian Field Naturalist 93:266-271.

Maddux, H. R. and W. G. Kepner. 1988. Spawning of bluehead sucker in Kanab Creek, Arizona (Pisces: Catastomidae). The Southwestern Naturalist 33:364-365.

Maddux, H. R., D. M. Kubly, J. C. deVos, Jr., W. M. Persons, R. Staedicke and R. L. Wright. 1987. Effects of varied flow regimes on aquatic resources of Glen and Grand Canyons. Final Report. US Bureau of Reclamation Contract #4-AG-40-01810. Arizona Fish and Game, Phoenix. 291 pp.

Mauck, P. E. 1986. Striped bass research study. Population trends (Texoma Reservoir). Federal Aid Project F-29-R. Oklahoma Department of Wildlife Conservation. 13 pp.

May, B. E., C. Thompson, and S. P. Gloss. 1975. Impact of threadfin shad (Dorosoma petenense) introduction on four centrarchids. Utah Division of Wildlife Resources. Pub. No. 75-4. 22 pp. McAda, C. W. and R. S. Wydoski. 1980. The razorback sucker, Xyrauchen texanus, in the upper Colorado River basin. US Fish and Wildlife Service Technical Papers No. 99. 15 pp.

McCaig, R. S. and J. W. Mullan. 1960. Growth of eight species of fishes in Quabbin Reservoir, Massachusetts in relation to age of reservoir and introduction of smelt. Trans. Am. Fish. Soc. 89(1):27-31.

McKenzie, R. A. 1958. Age and growth of smelt of the Miramichi River, New Brunswick. J. Fish. Res. Bd. Canada 15(6):1313-1327.

Merritt, D. H. 1976. Advective circulation in Lake Powell, UT-AZ. M. S. Thesis. Dartmouth College. Hanover NH. 86 pp.

Miller, R. R. 1961. Man and the changing fish fauna of the American southwest. Papers Michigan Academy of Science, Arts and Letters 46:365-404.

Mills, E. L. and A. Schiavone, Jr. 1982. Evaluation of fish communities through assessment of zooplankton populations and measures of lake productivity. North Am. Jour. Fish. Management 2:14-27.

Minckley, C. O., S. W. Carothers, J. W. Jordan, and H. D. Usher. 1981. Observations on the humpback chub (Gila cypha) within the Colorado and Little Colorado Rivers, Grand Canyon National Park, AZ. National Park Service Trans. Proc. Ser., Washington D. C.

Minckley, W. L. 1983. Status of the razorback sucker (Xyrauchen texanus) in the lower Colorado River. The Southwest Naturalist 28(2):165-187.

Minckley, W. L. and J. E. Deacon. 1968. Southwestern fishes and the enigma of "endangered species". Science 159:1424-1432.

Moczygemba, J. H. and D. J. Morris. 1977. Statewide striped bass study. Federal Aid Project F-31-R-3. Final Report. Texas Parks and Wildlife Department. 30 pp.

Moore, C. M., R. J. Neves, J. J. Ney, and D. K. Whitehurst. 1985. Utilization of alewives and gizzard shad by striped bass in Smith Mountain Lake, VA. Proc. SE Ass. Fish and Wildl. Comm. 39:108-115.

Ney, J. J. 1981. Evaluation of forage fish management in lakes and reservoirs. Trans. Am. Fish. Soc. 110(6):725-728.

O'Gorman, R. 1974. Predation by rainbow smelt, (Osmerus mordax), and young-of-the-year alewives, (Alosa pseudoharengus), in the Great Lakes. Prog. Fish Cult. 36(4):223-224.

Power, G. J. and J. B. Owen. 1984. Ichthyoplankton and zooplankton of the upper Van Hook Arm, Lake Sakakawea, North Dakota in 1983. Univ. of North Dakota, Grand Falls, ND.

Price, J. H. 1963. A study of the food habits of some Lake Erie fish. Ohio Biol. Surv., Bull., N. S. 2(1):1-89. Reckahn, J. A. 1970. Ecology of young lake whitefish (Coregonus clupeaformis), in South Bay, Manitoulin Islands, Lake Huron. Biology of Coregonid Fishes. Univ. of Manitoba Press, Winnipeg Can. 437-460 p.

Rothschild, B. J. 1961. Production and survival of eggs of the american smelt, (Osmerus mordax), in Maine. Trans. Am. Fish. Soc. 90(1):42-48.

. 1965. Aspects of the population dynamics of the alewife, (Alosa pseudoharengus), in Cayuga Lake, N. Y. American Midland Naturalist 74:479-496.

Rupp, R. S. 1959. Variations in the life history of the American smelt in inland waters of Maine. Trans. Am. Fish. Soc. 88:241-252.

. 1965. Shore spawning and survival of eggs of the american smelt. Trans. Am. Fish. Soc. 94:160-168.

. 1968. Life history and ecology of the smelt (Osmerus mordax) in inland waters of Maine. D. J. Proj. F-10-R. Final Report. Maine Dept. of Inland Fisheries and Game. Augusta, ME.

Rupp, R. S. and M. A. Redmond. 1966. Transfer studies of ecological and genetic variations in the American smelt. Ecology 47:(2).

Schaich, B. A. 1979. A biotelemetry study of spring and summer habitat selection by striped bass in Cherokee Res. TN. M. S. Thesis. University of Tennessee, Knoxville. 206 pp.

Schmulbach, J. C., T. J. Banek, and M. K. Musyl. 1983. Bionomics of the rainbow smelt (Osmerus mordax) in Lake Oahe, SD. Univ. of SD. and Dept. Game Fish and Parks. 149 pp.

Schneberger, E. 1937. The biological and economic importance of the smelt in Green Bay. Trans. Am. Fish. Soc. 66:139-142.

Scott, S. J. and A. W. Gustaveson. 1989. A creel census summary of twenty- two years at Lake Powell, UT 1964-1985. Utah Division of Wildlife Resources. Publication No. 89-10 Salt Lake City. 32 pp.

Scott, W. B. and E. J. Crossman. 1973. Freshwater fishes of Canada. Fish. Res. Bd. Canada. Bull. 184.

Selgeby, J. H., W. R. MacCallum, and D. V. Swedberg. 1978. Predation by rainbow smelt (Osmerus mordax) on lake herring (Coreoonus artedii) in western Lake Superior. J. Fish. Res. Bd. Canada 35:1457-1463.

Siefert, R. E. 1972. First food of larval yellow perch, white sucker, bluegill, shiner, and rainbow smelt. Trans. Am. Fish. Soc. 101:219-225.

Sinley, J. R. 1979. Fish forage species introductions. D. J. Proj. F-53-R-4. Colorado Div. Wildlife.

-49- Sollberger, P. J., P. D. Vaux and L. J. Paulson. 1989. Investigation of vertical and seasonal distribution, abundance and size structure of zooplankton in Lake Powell. Lake Mead Limnological Research Center. Environmental Research Center, University of Nevada, Las Vegas. 72 pp.

Speirs, G. D. 1972. The landlocked alewives value as a forage fish in Echo Lake, Mt. Desert Island, Maine. M. S. Thesis. Univ. of Maine, Orono. 43 pp.

Stevens, R. E. 1957. The striped bass of the Santee-Cooper reservoir. Proceedings of the Southeastern Association of Game and Fish Commissioners 11:253-264

Stewart, D. J., J. F. Kitchell, and L. B. Crowder. 1981. Forage fishes and their salmonid predators in Lake Michigan. Trans. Am. Fish. Soc. 110(6):751-7 63.

Stone, J. L. and N. L. Rathbun. 1969. Reservoir fisheries investigations: creel census and plankton studies. Glen Canyon Unit, Colorado River Storage Project, Federal Aid Project. F-17-R. AZ Game and Fish Dept.

Strange, R. J., K. D. Lee and D. C. Peterson. 1985. Age and growth food habits, and forage value of the alewife in Watauga Res., Tennessee. Proc. SE Ass. Fish and Wildl. Agencies. 39:108-115.

Suttkus, R. D. 1980. The rainbow smelt (Osmerus mordax) in the lower Mississippi River near St. Francisville, LA. American Midland Naturalist 104(2):394.

Suttkus, R. D. and G. H. Clemmer. 1977. The humpback chub (Gila cvpha) in the Grand Canyon area of the Colorado River. Occasional papers Tulane Univ. Museum of Natural History 1:1-30.

Swenson, W. A. and M. L. Matson. 1976. Influence of turbidity on survival, growth and distribution of larval lake herring (Coregonus artedii). Trans. Am. Fish. Soc. 105:541-545.

Tisa, M. S., J. J. Ney and D. K. Whitehurst. 1985. Spacial and temporal distribution of larval alewifes and gizzard shad in a Virginia reservoir. S.E. Ass. Fish and Wildl. Agencies. 39:65-73.

U. S. Fish and Wildlife Service. 1987. Bonytail Chub (Gila Elegans) Recovery Plan. Region 6, Denver, CO. 40 pp.

U. S. Fish and Wildlife Service. 1988. 1985 National survey of fishing, hunting, and wildlife associated recreation. Washington, D. C. 167 pp

Valdez, R. A. 1990. The endangered fish of Cataract Canyon. Final Report prepared for the U S Department of Interior, Bureau of Reclamation, Salt Lake City, Utah. Contract No. 6-CS-40-03980, Fisheries Biology and Rafting. Bio/West Report No. 134-3. 94 pp + appendices. t

Valdez, R.A. and G. H. Clemmer. 1982. Life history and prospects for recovery of the humpback and bonytail chub. Pp. 109-119 in W. H. Miller, H. M. Tyus, and C.A. Carlson, eds. Fishes of the upper Colorado River system: present and future. West. Div. American Fisheries Society, Bethesda, MD.

Van Oosten, J. 1937. The dispersal of smelt (Osmerus mordax) in the Great Lakes region. Trans. Am. Fish. Soc. 66:160-171.

Van Oosten, J. 1940. The smelt - (Osmerus mordax) Mimeo Rept. Mich. Cons. Dept., 13 pp.

. 1953. The Smelt (Osmerus mordax). Mich. Dept. Cons., Fish Div. Pamphlet No. 8, 13pp.

Vanicek, C. D., R. H. Kramer, and D. R. Franklin. 1970. Distribution of Green River fishes in Utah and Colorado following closure of Flaming Gorge Dam. Southwest Naturalist 14(3):297-315.

Vincent, R. E. 1960. Experimental introductions of fresh water alewives. Progressive Fish Culturist 22:38-42.

Wells, L. 1968. Seasonal depth distribution of fish in southeastern Lake Michigan. US Fish and Wildl. Ser. Fish. Bull. 67:1-15.

Wichers, B. 1980. Literature review of the rainbow smelt (Osmerus mordax) pertaining to possible introduction into Wyoming. WY Game and Fish.

Youngs, W. D. and R. T. Oglesby. 1972. Cayuga Lake: effects of exploitation and introductions on the salmonid community. J. Fish. Res. Bd. Canada 24:787-794.

-51-