— DEPARTMENT OF NATURAL RESOURCES DIVISION OF WILDLIFE RESOURCES

• 1---"N, 7-• ()1 August 30, 1989 I

SEP 2 I ; 1989

I 4s, y mi.;.7.„7... 774- f Mr. Galen L. Buterbaugh, Director Region 6 U.S. Fish & Wildlife Service Denver Federal Center P. 0. Box 25207 Denver, CO 80225-0207

Dear Galen:

Please find enclosed five copies of a proposal prepared by our Lake Powell staff for the introduction of rainbow smelt into Lake Powell. This proposal has been prepared as the most feasible approach to solve the critical forage shortage in Lake Powell and improving the once popular striped bass sport fishery. I would appreciate your distribution of this proposal to the appropriate members of your staff, particularly the Squawfish Recovery Team, so that we can get a thorough and substantive review of its merits.

As you may be aware, this proposal has been under development for a number of years. Major problems have been evident with the shad forage base in Lake Powell, and a number of alternative approaches have been examined. The smelt option as been under development for the last three years. The proposal, in earlier drafts, was presented to the Colorado River Wildlife Council as the first step in assessing both the potential benefits and any likely impacts which could be expected. The Council, which is made up of the seven state wildlife management agencies in the Colorado Basin, was selected as the logical first step to review the proposal, since the agencies have staff devoted to all aspects of the Colorado River fisheries, from both sport fish and native fish aspects. This past spring the Technical Committee of the CRFWC recommended acceptance of the proposal. In July the Council reviewed the proposal and directed us to take the next step and contact other involved agencies. With this final version of the proposal we are now prepared to take that next step.

In addition to sending you the proposal, we have also scheduled a meeting for September 29th, beginning at 10:00 a.m. in our office in Salt Lake City, where we will present the background and rationale supporting the proposal. I would like to invite you and your staff to listen to the proposal and also have your comments. We will not be looking for any final decision at this meeting, since we recognize that detailed technical review of the proposal will likely take longer. We would, however, like to gain some insight into the technical areas of the proposal which cause concern and also explore any other possibilities for solutions to improving the fishery at Lake Powell. Galen Buterbaugh August 30, 1989 Page 2

I invite your careful scrutiny of this draft and would be particularly interested in knowing any specific technical information which indicates the smAlt poses a likely threat to the endangered fishes in the system. We also need to know if the plan is likely to meet its objectives of improving forage for the striped bass population. With visitor use at Lake Powell exceeding that at Yellowstone Park, and a significant portion of that use being directed at fishing, the sport fishery is clearly too important to ignore. We also recognize the extreme value in preserving the native fishes in the Colorado System and, therefore, intend to work closely with you to make sure this, or any otner proposal, will not likely cause any decline in those species.

I look forward to meeting with you and your staff on the 29th and working together to solve this problem. Please let me know how many people to expect. I would also be pleased to provide any additional copies of the proposal which you may need.

Sincerely,

Bruce R. Schmidt Chief of Fisheries

BRS:bbb

Attachment

cc: Michael J. Spear, Regional Director Region 2 John Lancaster, Superintendent Glen Canyon National Park Tim Proven Draft Proposal

INTRODUCTION OF RAINBOW SMELT (OSMERUS MORDAX)

INTO LAKE POWELL, UTAH-ARIZONA

By

A. Wayne Gustaveson

and

Bruce Bonebrake

Lake Powell Fisheries Project Utah Department of Natural Resources Division of Wildlife Resources Timothy H. Provan, Director

August 1989 6 0

TABLE OF CONTENTS

Page

List of Tables

List of Figures ......

Introduction ......

Need for the Introduction ......

Expected Benefits ......

Life History and Ecology of Smelt ...... 2

Description 2 Distribution ...... 3 Habitat 3 Spawning ...... 4 Food Habits ...... 5 Smelt as Forage ...... 6

Possible Negative Impacts of Smelt ...... 6

Potential Displacement of Indigenous Species ...... 7 Humpback Chub ...... 7 Bonytail Chub ...... 9 Razorback Sucker ...... 9 Disease Potential 10 Hybridization ...... 11

Pygmy Smelt as an Alternative ...... 11

Post Introduction Evaluation ...... 11

Expected Behavior of Rainbow Smelt in Lake Powell ...... 11

Summary and Conclusions ...... 12

Literature Reviewed ...... 15

Appendix I Assessment of the Need for Forage Enhancement for the Benefit of Lake Powell Fishes ..... 25

Appendix II Answers to Commonly Asked Questions About Rainbow Smelt 47 LIST OF TABLES

Table Page

1. Stocking history of Lake Powell, Utah 1963-88 . . 26 •

2. Comparison of zooplankton densities (#/m3) in Great Lakes and four reservoirs. Taken from Paulson, 1989 . 44 LIST OF FIGURES

Figure Page

1. Creel rates (fish/angler hour) for largemouth bass, black crappie and all species, Lake Powell, April- June, 1965-85 ...... 30

2. Indicies of total recreational boat use and angling pressure, Lake Powell, 1965-88 ...... 31

3. Mean number of threadfin shad collected per trawl tow, July-September, Lake Powell, 1978-88 ...... 33

4. Catch rates (fish/net day) for walleye and largemouth bass annual netting, Lake Powell, 1971-88 ...... 35

5. Average condition factor (Kfl) of adult and juvenile striped bass at Lake Powell, 1975-88 ...... 37 PROPOSAL

INTRODUCTION OF RAINBOW SMELT (OSMERUS MORDAX) INTO LAKE POWELL, UTAH

INTRODUCTION

This proposal is submitted to the Colorado River Fish and Wildlife Council (CRFWC) for consideration during the 1989 Technical Committee and full council meetings which will be held in February and July, respectively. The format and timing are taken directly from the "procedures for introduction of aquatic organisms into the Colorado River basin" which was adopted in 1987. Background information on Lake Powell fisheries is presented in a report entitled 'Assessment of the Need for Forage Enhancement For The Benefit of Lake Powell Fishes" which is a supporting document (Appendix I). The ideas contained in this document will be presented to the Utah Wildlife Board, Arizona Game and Fish. the Striped Bass Committee of the CRFWC, the Technical Committee CRFWC, and other interested groups as appropriate. Following Council action the refined proposal will be presented to the U.S. Fish and Wildlife Service, upper and lower basin recovery teams, and the National Park Service.

NEED FOR THE INTRODUCTION

It is proposed that rainbow smelt (Osmerus mordax Mitchill) be introduced into Lake Powell to provide additional forage for all game fish. Threadfin shad (Dorosoma pentenense) are cu--ently 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 (Morone saxatilis) population has become stunted with few fish attaining a length in excess of 20 inches. Both walleye (Stizostedion vitreum) and striped bass populations suffer recurring periodic declines in physical condition which is attributable to the lack of sufficient shad forage. Juvenile and some adult striped bass are maintaining body condition by foraging directly on large zooplankton indicating a missing link in the food chain. Primary productivity of the reservoir is under-utilized by the predator impacted shad population. Further discussion of the need is contained in Appendix I.

EXPECTED BENEFITS

The establishment of rainbow smelt would increase forage species diversity and abundance. Since smelt would be thermally partitioned from shad in the stratified reservoir the two species would 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 would 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 would be available to all game fish. Since walleye and striped bass preferentially eat fish when available, more crayfish would be left for centrarchids.

Adding another forage species would 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 would increase in numbers in response to an I increase in plankton abundance.

Smelt grow larger than threadfin shad. Larger and more abundant forage would allow striped bass to attain larger size than at present. The establishment of smelt would lead to an immediate dramatic increase in the ■./ average size of striped bass. Mature striped bass require cooler water temperatures than juveniles. Providing forage to adult striped bass residing in the hypolimnion could shift striped bass biomass from the epilimnion to the depths of Lake Powell. A healthy adult striped bass population would help control recruitment of juvenile bass and thereby reduce total numbers. Larger ,\ striped bass would increase angler interest. Increased angling pressure would / be directed at mature striped bass which would offer some population control of this long lived predator. Increased angling pressure would 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 could benefit the local economy during an otherwise slow period.

LIFE HISTORY AND ECOLOGY OF SMELT

DESCRIPTION

The rainbow smelt is a slender, silver fish, pale green on 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 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 head and fins. The body is elongate, laterally compressed, with average length 178-203 mm. It has a pointed elongate 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, while 356 mm individuals have been taken in Lake Ontario and maritime coastal waters. Smelt less than 100 mm were considered subadult by Argyle (1982) 'n Lake Huron. The shortest mature smelt were 127 mm 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).

2 Total length was 117, 155, and 183 mm at age 2,3, and 4, respectively in Lake Huron (Baldwin 1950), and 152, 185, and 201 mm 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 smelt subsequently established in the entire Great Lakes complex within a 25 year period (Van Oosten 1937, Dymond 1944, Scott and Grossman 1973, Wichers 1980, Bergsted 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 LA 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, ND, in 1971 and subsequently became established downstream in Lake Oahe, SD (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. ,4 During the 1970's and 1980's, Colorado stocked smelt in many small SOFT' impoundments (Clear Creek Res., Twin Lakes, Turquoise Lake, Pueblo Res., Quincy Res., Rampart Res., and Horsetooth Res.) 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 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 (Oncorhvnchus mvkiss) and also provide food for cutthroat (Oncorhvncus 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

3 time. They are sensitive to light and temperature (Scott and Crossman 1973). and Smelt occupied the colder water of Lake Oahe, concentrating within or immediately and below the thermocline. There was a tendency for smaller fish to be distributed she somewhat shallower than the larger fish (Burczynski et al. 1985). Smelt were egg most often found in the hypolimnion at temperatures of 5- 14 C. During the day Ave most smelt were within several meters of the bottom but moved upward to the egg thermocline at night (Burczynski et al. 1987). In Lake Sakakawea smelt suspend in 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 COO' and Swenson 1983). Adult smelt in Lake Michigan occurred at 7-8 C during the C. day and 11-16 C at night. Larval smelt preferred 13-14 C during the day and 5-6 watE C at night (Brandt et al. 1980). A thermal preference of 12.8 C was documented mm a in Lake Champlain, and smelt preferred 6.6-8.3 C in Cayuga Lake, NY (Burbidge in M 1969). or t male Smelt avoid water temperatures higher than 15 C except for periodic matu ventures into surface waters (Rupp 1959). Smelt were not found in Lake Oahe 1964 where no nypolimnion existed and bottom waters exceeded 20 C. In Kennedy Lake, 2 ye NY, the midsummer distribution of smelt was restricted to the hypolimnion where temperatures were less than 13 C. Thermal preference effectively separated fish FOOD 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 inver temperature zone of 6-14 C (Wells 1968). Smelt cannot survive water temperatures own y in excess of 21-26 C (Wichers 1980). Ramps Gordo SPAWNING but f, It ... 13.7elt are typically anadromous fish that spawn in the spring. Like many the s anadromous fish they can live successfully in freshwater and have adapted to many conch' varying habitats. Smelt generally ascend into the mouths of streams not long predal after ice out, usually in Mar-Apr-May, depending on temperature and weather predai (Scott and Crossman 1973). Smelt rarely ascend streams more than a quarter mile Burbi, and usually stop at the first falls which has a drop of over one foot (Baldwin al. 1 1950). At Cold Creek, MI, smelt did not ascend above a zone of rapids within from the lowermost six hundred feet of a creek (Langlois 1935). In the Great Lakes pisci spawning occurs in the mouths of streams and within the lake on gravel shoals. is an Mean survival of fry from shore spawning and stream spawning were similar (Rupp 1965). Smelt hatched from stream spawning populations immediately adapted to shore spawning in a host lake where tributaries were absent (Rupp 1966). Smelt as av; from Lake Champlain, NY, spawned in fairly deep water and did not ascend streams 1971)1 or shallow shoreline areas for spawning (Halnon 1963). Spawning substrate type tiall1 may not affect survival from egg to sac fry stage (Hulbert 1974). than smelt . Spawning has been documented at temperatures ranging between 2-18.3 C found (Hoover 1936, Scott and Crossman 1973). Smelt spawning runs were initiated at that a 4.5 C and peak spawning occurred at 6.1 C in Quabbin Reservoir, Mass. (Hambly Michig 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 and Oa (Jilek 1979). Spawning takes place at night with spawners returning to the lake Mvsis, by day. Male smelt are covered with nuptial tubercles and can easily be (1961) separated from spawning females which feel smooth to the touch (Hoover 1936). Copepo( Two or more tuberculated males maintain positions against a female while eggs Purb ic 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 more than two years old 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 1948).

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 confirmed that smelt are an important predator of fishes (Creaser 1925', 1928;,Kendall 1927; Greene 19301 Rupp 1 8; Burbidge 1969; Delisle 1969; Lackey 1969) Anderson and Smith 1971; Selgeby et al. 1978). MacCrimmon and Pugsley (1971) concluded that "there is no evidence from any study that any segment of the smelt population becomes totally piscivorous, either on a seasonal or permanent basis; or that smelt predation is an obvious factor in the suppression of any sympatric population." r 41L LC u-.C ,C(1' 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 ate Mvsis while larger smelt primarily ate Mvsis and small alewives (Alosa pseudoharenqus) in Lake Michigan. Smelt longer than 180 mm ate three times more fish than smaller individuals. The smallest smelt to consume an alewife was 157 mm (Foltz and Norden 1977). O'Gorman (1974) found the smallest piscivorous smelt to be 143 mm and these smelt consumed fish that averaged 56 mm in 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, MN (Hassinger 1971). Lake Huron smelt relied mainly on Mvsis, 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, MI (Burbidge 1969), Lake Michigan (Crowder et al. 1981), Lake Huron (Reckahn 1970),

5 inland lakes in Minnesota (Hassinger 1970, 1972, Johnson 1963), inland waters of Maine (Rupp 1968), Rampart and Quincy Reservoirs in Colorado (Goettl 1983, 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 ND (Power et al. 1984) and Lake Oahe SD (Schmulbach et al. 1983). Calanoid copepods were the dominant food of smelt in Lake Superior (Seifert 1972). Cayuga Lake, NY, smelt mainly ate Mvsis 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, SD, were found to be "selective planktivores" that preferred larger zooplankters when available (Schmulbach et al. 1983).

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 1984; McCaig and Mullan 1960; Speirs 1972; Stewart 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 122.), northern pike (Esox lucius ) (Berard 1978, Marrone 1987, McCaig and Mullan 1960) and both smallmouth (Microoterus dolomieui) and largemouth bass (Microoterus salmoides) (McCaig and Mullan 1960, Bridges and Hambly 1971, Goettl 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, NE, 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 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, VA (Moore et al. 1985).

POSSIBLE NEGATIVE IMPACTS OF SMELT

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

6 ilt are released simultaneously. The eggs are broadcast over the bottom uickly adhere to the substrate by a short pedicel formed from the outer membrane (Rupp 1965). Individual female smelt produce an average of 25,000 4ith a range of 10,000-43,000 (Baldwin 1950, Bailey 1964, Langlois 1935). ge production per square foot of substrate in Dean Brook, Maine was 5,762 and 32 prolarvae (Rothschild 1961).

Incubation is 10-60 days depending on water temperature (Rupp 1968). r (1978) found that smelt eggs hatch in 8-29 days at temperatures of 4.4-21 ggs hatched between 183 and 195 hours after fertilization at an average temperature of 16.5 C. Unfertilized eggs are 0.8-0.9 mm and swell to 1.0 ter fertilization and water hardening. Egg survival to prolarvae was 1-2% the waters (Rothschild 1961, Rupp 1968). Smelt mature during their second ird growing season. Among two year old smelt in Lake Superior 41% of the and 18% of females were mature. All smelt more than two years old were e. Shortest smelt to reach maturity were 127 mm in Lake Superior (Bailey . Most investigators have found that smelt spawning runs are dominated by r old fish (McKenzie 1958, Van Oosten 1940, Baldwin 1948).

HABITS

Food studies show that smelt feed mainly on plankton, amphipods, and - tebrate insects but also prey on small cohabitating fishes, including their /oung (Hale 1960, Price 1963, O'Gorman 1974). In contrast, studies in New ;hire (Hoover 1936), Green Bay (Schneberger 1937), Lake Huron (Baldwin 1950, )n 1961), and Lake Erie (Ferguson 1965) indicated that smelt seldom ate fish, :ed primarily on zooplankton and bottom fauna. Van Oosten (1953) summarized nowhere have investigators found (game and commercial fishes) present in stomachs of smelt in any significant quantities". Further, Gordon (1961) luded that smelt in Lake Huron were probably not serious competitors or ators. Studies elsewhere have not confirmed that smelt are an important itor of fishes (Creaser 1925, 1928; Kendall 1927; Greene 1930; Rupp 1968; idge 1969; Delisle 1969; Lackey 1969; Anderson and Smith 1971; Selgeby et 1978). MacCrimmon and Pugsley (1979) concluded that "there is no evidence any study that any segment of the smelt population becomes totally ivorous, either on a seasonal or permanent basis; or that smelt predation n obvious factor in the suppression of any sympatric population."

Smelt are opportunistic feeders that feed on small, deepwater organisms vailable. Amphipods dominated the diet of smelt in Maine waters (Flagg ). Smelt smaller than 180 mm ate Mvsis while larger smelt primarily ate s and small alewives (Alosa pseudoharengus) in Lake Michigan. Smelt longer 180 mm ate three times more fish than smaller individuals. The smallest t to consume an alewife was 157 mm (Foltz and Norden 1977). O'Gorman (1974) d the smallest piscivorous smelt to be 143 mm and these smelt consumed fish averaged 56 mm in TL. Smelt examined by Foltz and Norden (1977) in Lake igan fed little in the winter and ceased to feed during spawning.

Smelt used copepods, Daohnia, midge and Hexagenia larvae in West Bearskin Devilfish Lakes, MN (Hassinger 1971). Lake Huron smelt relied mainly on s, but also consumed mayfly, caddis fly and ostracods (Baldwin 1950). Gordon 1) found Lake Huron smelt to eat copepods, cladocerans, insects and fish. pods and cladocerans were the most important food items in Gull Lake, MI bidge 1969), Lake Michigan (Crowder et al. 1981), Lake Huron (Reckahn 1970),

5 inland lakes in Minnesota (Hassinger 1970, 1972, Johnson 1963), inland waters of Maine (Rupp 1968), Rampart and Quincy Reservoirs in Colorado (Goettl 1983, 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 ND (Power et al. 1984) and Lake Oahe SD (Schmulbach et al. 1983). Cal anoid copepods were the dominant food of smelt in Lake Superior (Seifert 1972). Cayuga Lake, NY, smelt mainly ate Mvsis relicta and Pont000reia affinis L 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, SD, were found to be "selective planktivores" that preferred larger zooplankters when available (Schmulbach et al. 1983).

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 1984; McCaig and Mullen 1960; Speirs 1972; Stewart 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 122.), northern pike (Esox lucius ) (Berard 1978, Marrone 1987, McCaig and Mullan 1960) and both smallmouth (Microoterus dolomieui) and largemouth bass (Microoterus salmoides) (McCaig and Mullan 1960, Bridges and Hambly 1971, Goettl 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, NE, 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 lanillocked lakes in the eastern U. S. (Moore et al. 1985, Speirs 1972, Strange21B5, Vincent 1960, Rothschild 1965). Alewives rapidly became the dominant food item in striped bass stomachs after their introduction as forage in Smith Mountain Lake, VA (Moore et al. 1985).

POSSIBLE NEGATIVE IMPACTS OF SMELT

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

6 most often eat their own young because that is what is available in offshore deepwater areas.

Competition with other species that consume large plankton could 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.

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 could 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.

POTENTIAL DISPLACEMENT OF INDIGENOUS 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 primary cause of extirpation of native fishes from regulated portions of the river (Holden and Stalnaker 1975, Behnke and .4(0 Benson 1980). Bulkley and Pimentel (1983) attributed the disappearance of razorback sucker (Xyrauchen texanus) and three other endangered species from the Green River, UT, 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 0,k *f. current river environment is hostile 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).

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

Humpback chub spawning occurs Mar-Jun when water temperatures ar C (Suttkus and Clemmer 1977, Carothers et al. 1981, Minckley et al. 1981, and Zimmerman 1983). Colorado River main channel temperatures near 11 C this time may not be warm enough to even initiate spawning (Maddux et al. The Little Colorado River is generally 9 C warmer than the main channel ( and Zimmerman 1983). If spawning did occur in the main channel or if h chub fry were flushed into the main channel the exposure to 11 C tempe may be lethal (Hamman 1982, Maddux et al. 1987).

The Little Colorado River is unquestionably the most important tr for the continued existence of humpback chub in the Colorado River syst

Maddux et al. (1987) found most yoy humpback chub less than restricted to the Litle Colorado River. Although Maddux et al. (1987 native larval fishes in mainchannel habitats, humpback chub larva conspicuously absent. During a typical year humpback chub spawning is tr by water temperatures near 19 C (Hamman 1982, Maddux et al. 1987). Rainbc avoid temperatures in excess of 15 C (Rupp 1959) and die at 21 C (Wichers Rainbow smelt will not, therefore, be found in proximity of spawning a larval humpback chub. Larval humpback chub exposed to main channel tempe (where smelt could be found) would be lost due to temperature shock 1982).

Yoy humpback chub spend their first summer and fall in the warm trit and grow to about 70 mm during the first year. As the Little cools in October yoy chubs migrate out to the main Colorado River 1987). Smelt generally ingest fish smaller than 56 mm (O'Gorman Å. ,. highly unlikely that smelt and yoy humpback chub will occupy the same temp water while humpback chub fry are still small enough for smelt to eat.

Some overlap of habitat requirements for smelt and humpback chub ma at the mixing zone of the Little Colorado River and Colorado Ri% competition for food and space between the two species will be a Fortunately, humpback chub in this area are normally large enough t predation. Maddux et al. (1987) speculated that increased turbidity i major tributaries, including the Little Colorado River, would separate h of native and non-native fishes and thereby reduce predation on native Rainbow smelt were made more available to predators in turbid waters ( and Matson 1976). Smelt have been found to preferentially eat amphipods 1971) such as Gammarus that are abundant at the confluence. Humpback this location did not eat Gammarus but preferred chironomids, simulids e (Kaeding and Zimmerman 1983). It is possible that smelt may pro, additional food item for humpback chub. Competition for food and space native fish and invading exotics that occupy the same habitat [such as rec (Notropis lutrensis) and fathead minnow (Pimeohales promelas)] is a major to imperiled yoy. Smelt will be thermally separated from native fish la, will not increase the competition that currently exists between the fist,- in warmer water. Wichers (1980) states that, in general, potential conse

8 Jst often eat their own young because that is what is available in offshore eepwater areas.

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

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 quarter mile (Langlois 1935). They are not normally found in warm, silty ater, which is characteristic of Colorado River tributaries during summer flows. t is, therefore, very unlikely that smelt will move upstream from Lake Powell n the Colorado or San Juan Rivers or any of the major tributaries of the lower olorado River.

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

OTENTIAL DISPLACEMENT OF INDIGENOUS SPECIES

Of the many variables affecting distribution of endemic fishes in the olorado River, water temperature seems to be the Most important. Water emperature has been considered the primary cause of extirpation of native fishes -om regulated portions of the river (Holden and Stalnaker 1975, Behnke and - !nson 1980). Bulkley and Pimentel (1983) attributed the disappearance of izorback sucker (Xyrauchen texanus) and three other endangered species from le Green River, UT, to a decline in mean water temperature (from 18 C to 6.8 following the construction of Flaming Gorge Dam. Alteration of discharge and 2mperature regimes downstream from dams and diversions, conversions of riverine cosystems to lacustrine, introduction of non-native fishes and altered water luality have also hastened the decline of native fishes (Miller 1961, Minckley nd Deacon 1968). Declining populations of "big river" fishes indicate that the urrent river environment is hostile to their survival.

Iumpback Chub

A remnant population of humpback chub (Gila cvpha) remains in the lower )asin of the Colorado River centered around the Little Colorado River and four ocations in the upper basin (Valdez and Clemmer 1982). Adult humpback chub were .aptured in the Glen Canyon tailrace in 1967 (Suttkus and Clemmer 1977) but have ot been found in the tailrace recently (Maddux et al. 1987). Displacement of ative fishes from cold, clear western tailwaters is common (Vanicek et al. 970).

7 Maddux et al. (1987) found most humpback chub confined to the Little (benE Colorado River and backwaters 60 miles and further below Glen Canyon Dam in warm 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 Bonyt temperature was 10-11 C.

Humpback chub spawning occurs Mar-Jun when water temperatures are 16-20 and t C (Suttkus and'Clemmer 1977, Carothers et al. 1981, Minckley et al. 1981, Kaeding river and Zimmerman 1983). Colorado River main channel temperatures near 11 C during habit this time may not be warm enough to even initiate spawning (Maddux et al. 1987). team, The Little Colorado River is generally 9 C warmer than the main channel (Kaeding secur and Zimmerman 1983). If spawning did occur in the main channel or if humpback be th chub fry were flushed into the main channel the exposure to 11 C temperatures (Colo may be lethal (Hamman 1982, Maddux et al. 1987). --

The Little Colorado River is unquestionably the most important tributary in da for the continued existence of humpback chub in the Colorado River system. with be thE Maddux et al. (1987) found most yoy humpback chub less than 80 mm by co restricted to the Litle Colorado River. Although Maddux et al. (1987) found bonyt native larval fishes in mainchannel habitats, humpback chub larvae were survi\ conspicuously absent. During a typical year humpback chub spawning is triggered p by water temperatures near 19 C (Hamman 1982, Maddux et al. 1 Razort avoid temperatures in excess of 15 C (Rupp 1959) and die at 21 ' Wichers 1980). Oainbow smelt will not, therefore, be found in proximity

larval humpback chub. Larval humpback chub exposed to main channel temperaturit c)l r • '(where smelt could be found) would be lost due to temperature shock (Hamman hav:: 1982). , ,1 Avy) IW.AALA,' 0* %czior..b( Yoy humpback chub spend their first summer and fall in the warm tributaries die Cu and grow to about 70 mm during the first year. As the Little Colorado River in 19E cools in October yoy chubs migrate out to the main Colorado River (Maddux et al. recrui 1987). Smelt generally ingest fish smaller than 56 mm (O'Gorman 1974). It is 1984; highly unlikely that smelt and yoy humpback chub will occupy the same temperature threat water while humpback chub fry are still small enough for smelt to eat. • latioi

Some overlap of habitat requirements for smelt and humpback chub may occur at the mixing zone of the Little Colorado River and Colorado River but competition for food and space between the two species will be minimal. 1952) Fortunately, humpback chub in this area are norraalajarge enough to avoid 12-16 ( predation. Maddux et al. (1987) speculated that increased turbidity in three Mohave major tributaries, including the Little Colorado River, would separate habitats shallot. of native and non-native fishes and thereby reduce predation on native fishes. carp, c Rainbow smelt were made more available to predators in turbid waters (Swenson repro& and Matson 1976). Smelt have been found to preferentially eat amphipods (Flagg ova in that are abundant at the confluence. Humpback chub at spawn in 1971) such as Gammarus The vio this location did not eat Gammarus but preferred chironomids, simulids and fish gravel (Kaeding and Zimmerman 1983). It is possible that smelt may provide an additional food item for humpback chub. Competition for food and space between native fish and invading exotics that occupy the same habitat [such as red shiner Downwar (Pimephales promelas)] is a major threat (Notroois lutrensis) and fathead minnow desicca yoy. Smelt will be thermally separated from native fish larvae and to imperiled mortali exists between the fish living will not increase the competition that currently Protola in warmer water. Wichers (1980) states that, in general, potential consequences

8 (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.

Bonytail Chub

Bonytail chub (Gila rob sta) 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 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, pers. comm). Restoration by stocking may be the only means of maintaining bonytail chub in the Colorado River basin (Colorado River Fishes Recovery Team, in press; Bozek et al. 1984). i.'.' j Bonytail chub stocked at a total length greater than 80 mm would not be ( 6 in danger of predation from smelt. Bonytail chub are a sedentary insectivore 2 i with a 20 C preferred temperature (Valdez and Clemmer 1982).--Bbligtail 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 chub and humpback chub, but their populations have still declined. A remnant but steady state 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 (Minckley, AZ State Univ, pers. comm.), limited recruitment of razorback sucker presently occurs in Lake Mohave (Bozek et al. 1984; Burrell, NV Dept. Wildlife, pers. comm). The population is further threatened by hybridization with the more common flannelmouth sucker (Catostomus latipinnis).

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. 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, White Bozek et al. (1984) found razorback ova in a few channel catfish and observed carp feeding on the substrate in spawning areas, they found little evidence of extensive predation on the eggs. The violent spawning actions of razorbacks deposits eggs deeply into the loose gravel and protects most eggs from predators.

Razorback suckers usually select nest sites in water less than 1 m deep. Downward reservoir fluctuation 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

9 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. Bozek et al. (1984) speculates that they migrated to dense macrophyte beds of Mvriophillum and Potomegeton that grew at depths of 5- 10 m 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 should allow survival and recruitment of a limited number of razorback suckers in years when these conditions occurred.

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. 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, thus 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 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.

- 6( Bulkley and Pimentel (1983) found razorback suckersAo_prefer a temperature . ,J ' of 23 C. The preferred temperature of razorback is . y__thelethal temperature Y' 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.

Razorback sucker brood stock have performed well in the hatchery growing 4 to 326-456 mm in 2 years (Bozek et al. 1984). Rainbow smelt introduction should not limit maintenance stocking of razorback sucker. There seems to be adequate 1 6 v productivity and living space for both species. (\,0

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, SD by both Utah and SD show these fish to be free of the above mentioned parasites. Histological testing of smelt by Utah's fish pathology laboratory have failed to detect any prohibited pathogens. These investigations will continue. If parsites 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. HYBRIDIZATION

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

PYGMY SMELT AS AN ALTERNATIVE

Lanteigne and McAllister (1983) identified the pygmy smelt, (Osmerus spectrum Cope), 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 would render them more vulnerable to predation, however, which reduces the likelihood of their coping with Lake Powell's large predator populations. Rainbow smelt is the species of choice for introduction into Lake Powell.

POST INTRODUCTION EVALUATION

The smelt introduction will be constantly monitored and reported annually under JOB I (Forage Condition Study) of DJ Project F-46-R which is currently in place at Lake Powell and administered through the Utah Division of Wildlife Resources.

EXPECTED BEHAVIOR OF RAINBOW 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 2000 miles of shoreline. Some smelt would be attracted to the tributaries by the current, but silt bars guarding the San Juan and Escal ante 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 forced deep during the day. They would return to shallow water at night where they would forage on Le plankton.

11 Adult smelt would be forced out of the shallows by warming temper in early April. Adult smelt avoid temperatures above 15 C, which is the n temperature required for centrachid spawning in Lake Powell. Predaceous would not be in the shallows at the same time larval bass, crappie, or s would be emerging. Larval centrarchids use the shallow, warm water (1S as nursery areas. Larval smelt on the other hand still prefer water le! 14 C, suggesting partitioning of yoy smelt and yoy gamefish.

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

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

SUMMARY AND CONCLUSIONS

Rainbow smelt have been demonstrated to be a valuable forage spec many deep cool water lakes. They tend to occupy pelagic and deep water and avoid epilimnetic waters during much of the year. While adult sme sometimes predaceous, they would be separated from small game fish I striped bass) and forage fish by water temperature. Rainbow smelt meet r the criteria for a desirable forage fish (Ney 1981). When smelt hay introduced west of the Mississippi they have been prolific, trot:4 efficient, vulnerable to predation, and appear to be harmless (Goettl Smelt and striped bass are coevolved species both originating in North At coastal waters.

Lake Powell, with its absence of deepwater forage fish, seems tc excellent choice for rainbow smelt introductions. The hypolimnetic wat Lake Powell range from 7.0-12 C during the summer (Merritt 1976) and ar within the smelt's preferred temperature range. Crustacean plankton abt in Lake Powell (Sollberger et al. 1989) is similar to that found in thc Lakes where rainbow smelt are doing quite well. Rainbow smelt would pr( schooling forage fish that occupies the same strata as walleye and stripe during the entire year. Adult smelt would be thermally partitioned frc and yoy gamefish in the stratified reservoir and offer little threat of competition for food or space. Smelt flushed downstream below Lake Powel

12 HYBRIDIZATION

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

PYGMY SMELT AS AN ALTERNATIVE

Lanteigne and McAllister (1983) identified the pygmy smelt, (Osmerus spectrum Cope), 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 would render them more vulnerable to predation, however, which reduces the likelihood of their coping with Lake Powell's large predator populations. Rainbow smelt is the species of choice for introduction into Lake Powell.

POST INTRODUCTION EVALUATION

The smelt introduction will be constantly monitored and reported annually under JOB I (Forage Condition Study) of DJ Project F-46-R which is currently in place at Lake Powell and administered through the Utah Division of Wildlife Resources.

EXPECTED BEHAVIOR OF RAINBOW 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 2000 miles of 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 forced deep during the day. They would return to shallow water at night where they would forage on plankton.

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

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. 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, vulnerable to predation, and appear to be harmless (Goettl 1983).2:— 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 similar to that found in the Great Lakes where rainbow smelt are doing quite well. 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

12 pass through the riverine portions of the system and possibly establish populations in Lake Mead and Lake Mohave. 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 overabundance 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). Further, Berard (North Dakota Fish and Game Dept., personal communication, 1987) flatly states "The rainbow smelt is the salvation of the Missouri River system reservoirs". Smelt would seem to be a beneficial addition to the 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.

Commonly asked questions concerning the proposed smelt introduction are discussed in Appendix II.

13 LITERATURE REVIEWED

kAnddrson, E. D. and L. L. Smith, Jr. 1971. Factors affecting abundance of lake herring (Corecionus artedii) in western Lake Superior. TAFS 100(4):691-707.

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

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

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

Beckman, W.C. 1942. Length-weight relationship, age, sex ratio and food habits of smelt (Osmerus mordax) from Crystal Lake, Benzie County, Michigan. Copeia: 120-124.

----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.

P'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

1980. Ecological investigations of the Missouri mainstream reservoirs in North Dakota. North Dakota Fish and Game Dept. Report No. A-1064.

. 1981. Ecological investigations of the Missouri mainstream reservoirs in North Dakota. North Dakota Fish and Game Dept. Report No. A-1070.

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

Bigelow, H. B. and W. C. Schroeder. 1953. Fishes of the Gulf of Maine. USFWS, Fish. Bull. No. 74, Vol. 53, 577 pp.

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. UNLV Las Vegas, NV.

Brandt, S. B. 1980. Spatial segregation of adult and young-of-the-year alewives across a thermocline in Lake Michigan. TAFS 109:469-478.

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

Breder, Q. M. Jr., and R. F. Nigrelli. 1936. The winter movements of the landlocked alewife, Pomolobuspseudoharengus. Zoologica21(13):273-291. Bridges, C. H. and L. S. Hambly. 1971. A summary of 18 years of sa management at Quabbin Reservoir, Mass. In: Reservoir Fisheri Limnology. G. E. Hall (ed). AFS Special Pub. No. 8:243-254.

Brooks, J. L. 1968. The effects of prey size selection by lake plankti Syst. Zool. 17(3):273-291.

Bulkley, R. V. and P. Pimental. 1983. Temperature preference and avoida adult razorback suckers. TAFS 112:601-607.

Burbidge, R.G. 1969. Age, growth, length-weight relationship, sex rati food habits of smelt (Osmerus mordax) from Gull Lake Michigan. 98:631-640.

Burczynski, J. J., G. M. Marrone and P. H. Michaletze. 1985. Echo surv Lake Oahe for rainbow smelt abundance estimation July 1983 and Biosonics Inc., 4520 Union Bay Place N. E. Seattle, WA 98105. 8

Burczynski, J. J., P. H. Michaletz, and G. M. Marrone. 1987. Hydroac assessment of the abundance and distribution of rainbow smelt i Oahe. NAJFM 7:106-116.

Burr, B. M. and R. L. Mayden. 1980. Dispersal of rainbow smelt, (0 mordax), into the upper Mississippi River. American Midland Natu 104:198-201.

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

Christie, W. J., J. M. Fraser, and S. J. Nepszy. 1972. Effects of s introductions on salmonid communities in oligotrophic lakes. J. Res. Bd. Canada 29:969-973.

Clayton, G.R. 1976. Reproduction, first year growth and distribut anadromous rainbow smelt, Osmerus mordax, in the Parker Rive Island South Estuary, Massachusetts. M. S. Thesis. Univ. of Amherst. 102 pp.

Cooper, J. E. 1978. Identification of eggs, larvae, and juveniles the r smelt, (Osmerus mordax), with comparisons to larval alewife, pseudoharengus) and gizzard shad, (Dorosoma cepedianum). 107:56-62.

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

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

16 LITERATURE REVIEWED

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

-gyle, R. L. 1982. Alewives and rainbow smelt in Lake Huron: midwater and bottom aggregations and estimates of standing stocks. TAFS 111:267-285.

Iiley, M.M. 1964. Age, growth, maturity, and sex composition of the American smelt, (Osmerus mordax), of western Lake Superior. TAFS 93:382-395.

ildwin, N. S. 1950. The american smelt, (Osmerus mordax), of South Bay, Manitoulin Island, Lake Huron. TAFS 78:176-180.

2ckman, W.C. 1942. Length-weight relationship, age, sex ratio and food habits of smelt (Osmerus mordax) from Crystal Lake, Benzie County, Michigan. Copeia: 120-124.

ehnke, 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.

erard, 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

1980. Ecological investigations of the Missouri mainstream reservoirs in North Dakota. North Dakota Fish and Game Dept. Report No. A-1064.

1981. Ecological investigations of the Missouri mainstream reservoirs in North Dakota. North Dakota Fish and Game Dept. Report No. A-1070.

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

igelow, H. B. and W. C. Schroeder. 1953. Fishes of the Gulf of Maine. USFWS, Fish. Bull. No. 74, Vol. 53, 577 pp.

ozek, 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. UNLV Las Vegas, NV.

3randt, S. B. 1980. Spatial segregation of adult and young-of-the-year alewives, across a thermocline in Lake Michigan. TAFS 109:469-478.

3randt, S. B., J. J. Mangnuson and L. B. Crowder. 1980. Thermal habitat partitioning by fishes in Lake Michigan. Can. J. Fish and Aquatic Science 37(10):1557-1564.

3reder, C. M. Jr., and R. F. Nigrelli. 1936. The winter movements of the landlocked alewife, Pomolobuspseudoharengus. Zoologica21(13):273-291.

15 (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). AFS Special Pub. No. 8:243-254.

Brooks, J. L. 1968. The effects of prey size selection by lake planktivores. Syst. Zool. 17(3):273-291.

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

Aurbidge, It.G. 1969. Age, growth, length-weight relationship, sex ratio, and food habits of smelt (Osmerus mordax) from Gull Lake Michigan. TAFS 98:631-640. vBurczynski, J. J., G. M. Marrone and P. H. Michaletze. 1985. Echo surveys on DL Lake Oahe for rainbow smelt abundance estimation July 1983 and 1984. Biosonics Inc., 4520 Union Bay Place N. E. Seattle, WA 98105. 89 pp.

- '- Burczynski, J. J., P. H. Michaletz, and G. M. Marrone. 1987. Hydroacoustic Dy, assessment of the abundance and distribution of rainbow smelt in Lake Oahe. NAJFM 7:106-116. EME Y'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. Fer

.4arothers, 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 .c' i s and selected tributaries from Lee's Ferry to Separation Rapids. Final Rept. to WPRS, Contract No. 7-07-30-X0026. Museum of Northern AZ, Flagstaff, AZ. Fl a(

Christie, W. J., J. M. Fraser, and S. J. Nepszy. 1972. Effects of species introductions on salmonid communities in oligotrophic lakes. J. Fish. Res. Bd. Canada 29:969-973.

Clayton, G.R. 1976. Reproduction, first year growth and distribution of anadromous rainbow smelt, Osmerus mordax, in the Parker River-Plum Island South Estuary, Massachusetts. M. S. Thesis. Univ. of Mass. Amherst. 102 pp. Flagc

/ 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 cepedianum). TAFS Foltz 107:56-62.

v 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. Georg, Arts and Letters 10:427-431.

16 Crowder, L. B. 1980. Alewife, smelt and native fishes in Lake Michigan: 6 Competition or predation? Environmental Biology of Fishes 5(3):225-233.

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 fl' and Aquatic Sci. 38(6):662-668.

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

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

Dunstall, T.G. 1980. Aspects of the population dynamics of rainbow smelt C, (Osmerus mordax) and alewife, (Alosapseudoharengus) -Areview. Ontario Hydro. Res. Div. Rep. No. 80-382-K, Ontario, Canada. 50 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 .

Emery, A. R. 1973. Preliminary comparisons of day and night habits of freshwater fish in Ontario lakes. J. Fish. Res. Bd. Canada 30:761- 774.

v 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. Fisk, L. and C. E. von Geldern Jr. . Review of the use of forage fish in r California. Cal. Dept. Fish and Game. v'eFlagg; L. N. 1971. Striped bass and smelt survey. Proj. AFS-4-4. Maine Dept. of Marine Resources, Final Rept.

. 1972. The anadromous smelt fishery of Maine. Maine Dept. of Marine 0 Resources Research Bull. No. 33.

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

1/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.

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

. 1977. Seasonal changes in food consumption and energy content of smelt, (Osmerus mordax), in Lake Michigan. TAFS 106(3):230-234.

George, C. J. and J. H. Gordon II. 1976. Observations on the rainbow smelt in Lake George, New York. New York Fish and Game 23(1):13-19.

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

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

Gordon, W. C. 1961. Food of the American smelt in Saginaw Bay, Lake TAFS 90(4):439-443.

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

Guest, W. C. 1986. Blueback herring evaluation. D. J. Rept. F-31- R-12 Parks and Wildlife Dept., Austin, TX. 57 pp.

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

Hale, J. G. 1960. Some aspects of the life history of the smelt (, mordax) in western Lake Superior. In: C. R. Burrows and A. B. Er eds. Minnesota Fish and Game Investigations. Minn Dept. Cons 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 F-1-R-10, Job No. 6. New York Fish and Game. 94 pp.

Hambly, L. S. 1970. Lake trout study. D. J. Proj. F-36-R-2, Massachusetts Div. of Fisheries and Game.

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

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

Hart, J. L. and R. G. Ferguson. 1966. The american smelt. Trade News 19

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

1971. Examination of stomach contents of lake trout and smelt fr Bearskin and Devilfish Lakes. D.J. Proj. F-26-R-2, Job 1-2. Mi Div. of Fisheries and Wildlife.

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

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

18 .owder, L. B. 1980. Alewife, smelt and native fishes in Lake Michigan: Competition or predation? Environmental Biology of Fishes 5(3):225-233.

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

.eyer, 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.

Install, T.G. 1980. Aspects of the population dynamics of rainbow smelt (Osmerus mordax) and alewife, (Alosa pseudoharengus) -Areview. Ontario Hydro. Res. Div. Rep. No. 80-382-K, Ontario, Canada. 50 pp.

'mond, J. R. 1944. Spread of the smelt (Osmerus mordax) in the Canadian waters of the Great Lakes. Canadian Field Naturalist 58:12-14 . lery, A. R. 1973. Preliminary comparisons of day and night habits of freshwater fish in Ontario lakes. J. Fish. Res. Bd. Canada 30:761- 774.

Tguson, 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.

sk, L. and C. E. von Geldern Jr. __. Review of the use of forage fish in California. Cal. Dept. Fish and Game.

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

1972. The anadromous smelt fishery of Maine. Maine Dept. of Marine Resources Research Bull. No. 33.

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

agg, 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.

ltz, 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.

. 1977. Seasonal changes in food consumption and energy content of smelt, (Osmerus mordax), in Lake Michigan. TAFS 106(3):230-234.

)rge, C. J. and J. H. Gordon II. 1976. Observations on the rainbow smelt in Lake George, New York. New York Fish and Game 23(1):13- 19.

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

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

e. Gordon, W. C. 1961. Food of the American smelt in Saginaw Bay, Lake Huron. TAFS 90(4):439-443. He ,—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.

Guest, W. C. 1986. Blueback herring evaluation. D. J. Rept. F-31- R-12. Texas Her Parks and Wildlife Dept., Austin, TX. 57 pp.

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

e---Hale, J. G. 1960. Some aspects of the life history of the smelt (Osmerus Hoic 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. Hoov v/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. Hulb Hambly, L. S. 1970. Lake trout study. D. J. Proj. F-36-R-2, Job No. VI-1. Massachusetts Div. of Fisheries and Game.

. 1972. Quabbin Reservoir smelt study. D. J. Proj. F-36-R -4, Job V1-3. JiIe Massachusetts Div. of Fisheries and Game.

.Alamman, R. L. 1982. Spawning and culture of humpback chub. Prog. Fish-Cult 44:213-216. Johns Hart, J. L. and R. G. Ferguson. 1966. The american smelt. Trade News 19:22-23.

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 Kaedi Wildlife.

. 1971. Examination of stomach contents of lake trout and smelt from West Bearskin and Devilfish Lakes. D.J. Proj. F-26-R-2, Job 1-2. Minnesota Kenda* Div. of Fisheries and Wildlife. Kircht . 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. Kirk,

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. Kohler

18 i/Havey, K. A. 1973. Effects of a smelt introduction on growth of landlocked salmon at Schoodic Lake, Maine. TAFS 102:392-397.

Havey, K. A. and K. Warner. 1970. The landlocked salmon, Salmo salar, its life (- history and management in Maine. Joint Publ. Sport Fishery Institute, ' Washington, D. C. and Maine Dept. Inland Fish and Game. Augusta, Maine. 129 pp.

v-fleist, 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.

Herron, R. C. 1980. Annotated bibliography on introductions of some species 0 of fishes as forage for predatory fish into various waters. Utah Coop. - Fish Unit. Utah State Univ. Logan, UT. 135 pp.

Hile, R., G. F. Lunger, and H. J. Buettner. 1953. Fluctuations in the fisheries of state of Michigan waters of Green Bay. USFWS Fish. Bull. 54:1-34.

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

v/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.

k'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. 5-#1.44.44 l/Kaeding, L. R. and M. A. Zimmerman. 1983. Life history and ecology of the humpback chub in the Little Colo'rado and Colorado Rivers of the Grand Canyon. TAFS 112:577-594.

Aendall, W. C. 1927. The smelts. Bull U. S. Bur. Fisheries 42(101 5):217-375.

v/kircheis, F. W., and J. G. Stanley. 1981. Theory and practice of forage fish management in New England. TAFS 110(6):729-737.

Kirk, J. P. and W. D. Davies. 1985. Competitive influences of gizzard shad on largemouth bass and bluegill in small impoundments. Proc. SEAFWA 39:116-124.

Kohler, C. C., and J. J. Ney. 1980. Suitability of alewife as a pelagic forage fish for southeastern reservoirs. Prod. Ann. Conf. SEAFWA 34:137-150.

19 // Lackey, R. T. 1969. Food interrelationships of salmon, trout, alewives and smelt in a Maine lake. TAFS 98:641-646.

vLanglois, 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

Li, H. W. and P. B. Moyle. 1981. Ecological analysis of species introductions into aquatic systems. TAFS 110(6):772-782.

Lievense, S. J. 1954. Spawning of american smelt, Osmerus mordax, in Crystal Lake, Benzie County, Michigan. Copeia:232-233.

MacCallum, W. R. and H. A. Regier. 1970. Distribution of smelt, Osmerus mordax, and the smelt fishery in Lake Erie in the early 1960's. J. Fish. Res. Bd. Canada 27(10):1823-1846. P' 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.

/fladdux, 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. U. S. B. R. Contract #4-AG-40-01810. AZ Fish and Game, Phoenix, AZ. 291 pp.

Magnuson, J. J. 1976. Managing with exotics - a game of chance. TAFS 105:1-9. 0

0.-McAda, C. W. and R. S. Wydoski. 1980. The razorback sucker, Xvrauchen texanus, in the upper Colorado River basin. USFWS 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. TAFS 89(1):27-31.

McCullough, R. D, and J. G. Stanley. 1979. Feeding niche dimensions in larval rainbow smelt (Osmerus mordax). International Council for the \./ exploration of the sea, ICES/ELH FM4, Copenhagen, Denmark.

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

. 1964. Smelt life history and fishery in the Miramichi River, New 0 ,Brunswick. Fish. Res. Bd. Canada Bull. 144:77.

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

/11iller, R. R. 1961. Man and the changin9 fish fauna of the American southwest. Papers Michigan Academy of Science, Arts and Letters 46:365-404.

20 v/Mlills, E. L. and A. Schiavone, Jr. 1982. Evaluation of fish communities through assessment of zooplankton populations and measures of lake productivity. NAJFM 2:14-27.

"A‘ckley, C. 0., S. W. Carothers, J. W. Jordan, and H. D. Usher. 1981. Observations on the humpback chub, Gila cvoha, within the Colorado and Little Colorado Rivers, Grand Canyon National Park, AZ. National Park Service Trans. Proc. Ser., Washington D. C.

041inckley, W. L. 1983. Status of the razorback sucker, X rauchen texanus, in the lower Colorado River. The Southwest Naturalist 28(2):165-187.

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

'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. SEAFWA 39:108-115.

Murawski, S. A., and C. F. Cole. 1978. Population dynamics of anadromous rainbow smelt, (Osmerus mordax), in a Massachusetts river system. TAFS 107(4):535-542.

vNey, J. J. 1981. Evaluation of forage fish management in lakes and reservoirs. TAFS 110(6):725-728.

Noble, R. L. 1981. Management of forage fish in impoundments of the southern 0 United States. TAFS 110(6):738-750.

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

p/Power, G. J. and J. B. Owen. 1984. Status of the walleye population in lake Sakakawea and factors affecting their abundance. D. J. Proj. F-2-R-30, Study VIII, Report No. A-1108. North Dakota State Game and Fish Dept. 15 pp.

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

v 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.

Prince, E. D. and D. H. Barwick. 1981. Landlocked blueback herring in two South Carolina Reservoirs; reproduction and suitability as stocked prey. NAJFM 1(1):41-45.

/ v Reckahn, J. A. 1970. Ecology of young lake whitefish (Coredonus clupeaformis), in South Bay, Manitoulin Islands, Lake Huron. Biology of Coregonid Fishes. Univ. of Manitoba Press, Wimipeg Can. 437-460 p.

21 -"Rothschild, B. J. 1961. Production and survival of eggs of the american smelt, (Osmerus mordax), in Maine. TAFS 90(1):42-48.

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

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

. 1 65., shore spawning and survival of eggs of the american smelt. TAFS 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, Maine.

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

,,'Schmulbach, J. C., T. J. Banek, and M. K. Musyl. 1983._ Bionomics of the rainbow smelt (Osmerus mordax) in Lake Oahe, So. Dakota. Univ. of So. Dakota. and Dept. Game Fish and Parks. 149 pp.

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

/Scott, W. B. and E. J. Grossman. 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 (Corecionus artedii) in western Lake Superior. J. Fish. Res. Bd. Canada 35:1457-1463.

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

Sinley, J. R. 1978. Fish forage species introductions. Environmental Assessment Report, D. J. Proj. F-53-R-3. Colorado Div. Wildl. 6 pp.

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

Smith, S. H. 1970. Species interactions of the alewife in the Great Lakes. TAFS 99:754-765.

''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.

22 Squires, T. A., L. Flagg, and L. Austin. 1977. Smelt management plan. Completion report; Projects AFSC-13/FWAC-2, Seg 22 and 24, Maine Dept. ( r) of Marine Resources.

Stanley, J. G., and P. J. Colby. 1971. Effects of temperature on electrolyte balance and osmoregulation in the alewife, (Alosa psuedoharengus),.in fresh water and sea water. TAFS 100:624-638.

Stedman, R. M., and R. L. Argyle. 1985. Rainbow smelt (Osmerus mordax) as predators of young bloaters (Corecionus hovi) in Lake Michigan. J. Great Lakes Research 11(1):40-40.

VStewart, D. J., J. F. Kitchell, and L. B. Crowder. 1981. Forage fishes and their salmonid predators in Lake Michigan. TAFS 110(6):751-7 63. ).k e'C

2, Straftge, 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. SEAFWA 39:108-115.

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

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

644Wenson, W. A. and M. L. Matson. 1976. Influence of turbidity on survival, growth and distribution of larval lake herring (Coregonus artedii). TAFS 105:541-545.

Tanner, H. 1975. Salmonids in lakes. Michigan State Univ., East Lansing, MI 9 PP. ,,-'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. AFS, 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.

1947. Mortality of smelt, Osmerus mordax, in Lakes Huron and Michigan during the fall and winter of 1942-43. TAFS 74:310-337.

1947. The smelt, Osmerus mordax Great Lakes, Fish. Invest. US Bur. Fish. Ann Arbor, Michigan. (mimeo).

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

23 v-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.

Wagner, W. C. :1972. Utilization of alewives by inshore piscivorous fishes in Lake Michigan. TAFS 101:55-63. IN

Wales, J. H. 1962. Introduction of pond smelt from Japan to California. Cal. whe Fish and Game 48:(2):141-142. The cra Warfel, H. E., T. P. Frost, and W. H. Jones. 1943. The smelt,Osmerus mordax, kok in Great Bay, New Hampshire. TAFS 72:257-262. cra tro Seasonal depth distribution of fish in southeastern Lake L. 1968. fist Michigan. USFWS Fish. Bull. 67:1-15. aftt Wells L. and A. L. Mclain. 1972. Lake Michigan: effects of exploitation, introductions, and eutrophication on the salmonid community. J. Fish. recc 29(6):889-898. Res. Bd. Canada pete posi / Literature review of the rainbow smelt (Osmerus mordax) v Wichers, B. 1980. Pett pertaining to possible introduction into Wyoming. WY Game and Fish. and crap Wiedenheft, B. 1987. A fish called cisco. Montana Outdoors. Montana Dept. Lake of Fish, Wildlife and Parks. p. 34-37. impor Wydoski, R. S., and D. H. Bennett. 1981. Forage species in lakes and reservoirs of the western United States. TAFS 110(6):764-771. begat matur exploitation i-Youngs, W. D. and R. T. Oglesby. 1972. Cayuga Lake: effects of fishE and introductions on the salmonid community. J. Fish. Res. Bd. Canada reprc 24:787-794. also and w Zilliox, R. G. and W. D. Youngs. 1958. Further studies of the smelt in Lake threa , Champlain. N. Y. Fish and Game J. 5(2):164-174. bass number

to man must or wan expect Powell expect approa when o Constar •;r4 i's04111-1-M*111- IV\ 0,0 q)" 1 Ni$1■16 n 111). '0011N. Appendix I

ASSESSMENT OF THE NEED FOR FORAGE ENHANCEMENT FOR THE BENEFIT OF LAKE POWELL FISHES

INTRODUCTION

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 (Micropterus salmoides), black crappie (Pomoxis nigromaculatus), rainbow trout (Oncorhvnchus mvkiss) and kokanee salmon (Oncorhvnchus nerka kennerlvi) (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. The kokanee fisheries were discontinued soon after stocking.

The need for additional forage to support the sport fisheries was recognized early and resulted in the introduction of threadfin shad (Dorosoma petenense) 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 60's and early 70's which gained Lake Powell a national reputation as a bass and crappie fishery. Walleye (Stizostedion vitreum) were never introduced into Lake Powell but a population grew from stock present when the reservoir was impounded. This fishery peaked in the early 80's.

Striped bass (Morone saxatilis) fingerling were introduced in 1974 and began contributing to the sport fishery in 1979, the year they became sexually mature. At the time of introduction it was uncertain if the striped bass fisheries could be maintained by natural reproduction. 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 limited 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.

Large, man-made reservoirs present great challenges to those attempting to manage them. Often the reservoir and the fish dictate to the manager what must occur. Walleye established in the reservoir where they were not planned or wanted. Striped bass reproduced within the reservoir where they were pot expected to spawn. Yet, at the same time, bass and crappie fisheries at Lake Powell performed better than expected. Threadfin shad performed well their expected role as forage organisms even though winter water temperatures- often approach lethal levels. Striped bass produced fisheries that peaked at a time when other Lake Powell fisheries were declining and unable to support the constantly increasing angling pressure.

25 Table 1. Stocking history of Lake Powell, Utah, 1963-88

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 1

1964 Largemouth Bass 1,000,000 2-3" Warm Creek-Last Chance Aerial 1 Largemouth Bass 250,000 2-3" Escalante (mouth) 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 I S 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 19 Black Crappie 350 6" Wahweap Creek Truck Black Crappie 9,000 3" Wahweap Creek Truck 197 1965 Rainbow Trout 4,383,525 2-3" Reservoir Wide Aerial Rainbow Trout 40,000 5" Wahweap Creek Truck 198

Black Crappie 30,000 1" Wahweap Creek Truck 198 Black Crappie 4,700 4" Wahweap Creek Truck 198 1966 Rainbow. Trout 2,140,000 2-3" Reservoir Wide Aerial

1967 Rainbow Trout 344,049 4-5" Wahweap-Warm Creek Aerial 198: Rainbow Trout 103,205 4-5" Hall's X-ing-Bullfrog Barge Rainbow Trout 102,590 4-5" Red Canyon Barge 1984

1968 Rainbow Trout 201,364 3-5" Wahweap Creek Barge 1985 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 ------1986 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

26 Table 1. Continued

Year Species Number Size Area Method

1972 NO STOCKING ------

1973 Rainbow Trout 233,400 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 Smallmouth Bass 19,360 2-4" Good Hope Bay Aerial Smallmouth Bass 26,328 2-4" Neskahi Canyon Aerial Smallmouth Bass 702 10-15" Hite-Dirty Devil Riv. Truck

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

27 Table 1. Continued C Year Species Number Size Area Method

1987 Smallmouth Bass 220 3-6" Wahweap-Warm Creek Truck a Smallmouth Bass 24,200 2-3" West Canyon Aerial , Smallmouth Bass 7,200 2-3" Nokai Canyon Truck b 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 at Bass 10,880 2" Navajo Canyon Aerial Smallmouth an do an 0., thl fi: St. cat 70' pas man

THR

are Riv com and pop Pow pel bas peak (Fl rec ver in comp occu They shor avai

that peak matey areas Lake Powell is constantly changing. Fisheries management must be just as dynamic and flexible to be effective. The purpose of this paper is to present the current status of Lake Powell fisheries and how they have evolved.

Then we will present our predictions for the future and some management alternatives that could beneficially alter Lake Powell fisheries of 1995 and beyond.

CURRENT STATUS OF LAKE POWELL FISHERIES

Over the past 20 years, fishing at Lake owell has been good enough to attract anglers from all over the world. Whe, the reservoir was young, bass and crappie fishing was outstanding. 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 (Figure 1). Fishing pressure has been steadily increasing throughout the life of the reservoir (Figure 2). Despite the increase in fishing pressure the catch rate for all species of fish combined in 1985 was still near the historic average of 0.4 fish per hour. More fishermen are catching fish just as often as those anglers that fished Lake Powell in the 70's. This means that more fish are currently being harvested than in the past. The game fish of Lake Powell still provide a quality experience for the many fishermen that utilize them each year.

THREADFIN SHAD

Sufficient forage is the key to producing a successful fishery. 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 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 3). 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 does occur in non-peak years but yoy shad are not forced into the pelagic zone by competition for food and space. Trawl and sonar sampling confirm that shad , occupy the upper 10 meters in the water column in the stratified reservoir. They are not found below the thermocline. In most years shad are 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 3). A peak did not materialize in 1987 with no shad being collected in trawl samples in most areas of the reservoir. Shad were also absent from 1988 pelagic trawl

29 1.3— 1.2------All Species A -I % ------Black Crappie 1.1- I \ I \ Larg•moulh Bas s .. 1.0- 1 a I o 1 • 0.9- 1 1 1 .. 0.8- I 1 —• i a 1 . c 0.7- i 1 / r....) .. 0.6- -- I \ 1 cp • \ (' /‘ \ / \ a. 0.5- \ // \ / *I \ .c %.--. : % ■ / \ _O 0.4- \ \ sr. / /. / ‘.. . / 0.3- / ■ . / ‘‘\ i % / v ... 0.2- -....,

0.1-

I I r . ■ 65 66 67 68 69 70 71 72 73 74 75 76 7? 78 79 80 81 82 83 841 85 Y. • r

Figure 1. Creel rates (fish/angler hour) l or l argemouth bass, black crappie aud all species, Lake Powell, April-Julie 19b5-l9t3 . 450 —

400

350 ^

300 Total 250

200

150 Fishing 1 00

50

0 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 2. indices of total recreational boat use and angling pressure, Lake Powell, 1965-1988. sampling. The current state of the shad population is a predator impacted resource. There is not enough pelagic forage available to maintain healthy body condition (K factor) in those species (walleye and striped bass) which depend almost entirely on threadfin shad for sustenance.

OTHER FORAGE ORGANISMS

Other forage fish consumed by Lake Powell's game fish include bluegill (Lepomis macrochirus), green sunfish (Lepomis cvanellus), red shiner (Notroois lutrensis) and carp (Cvorinus c.rpio). Crayfish (Orconectes virilis), zooplankton, and aquatic insects are also consumed. Most of these organisms are eaten by shorebound game fish and yoy of all species. In years when shad numbers are low the predatory burden on these 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 4). 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 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 the later 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 from other game fish. 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. Year

Figure 3. Mean number of threddfin shad collected per trawl tow, July-September, Lake Powell, 1987-88. 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 (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.

BLACK CRAPPIE

Crappie abundance has declined in much the same manner and for the same reasons as stated for largemouth bass. Crappie are even more dependent on brush than largemouth. Crappie prefer to nest on substrate with a bush 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 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.

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 4). Walleye were notoriously hard for anglers to catch in the 70's but a good fishery occurred in the early 80's. 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.

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.

34 Walleye

6

5

4

3

2 ...... • •

1

0 i I I 1 l i f i l i i f i l I 71 73 75 77 '79 81 E3 85 87 72 74 FID 82 4 813. Year

Largemouth Bass

. . .

; I t , 71 73 75 77 4 79 81 83 85 87 72 7 75 ET) K2 Ftot Yeur gure 4. Catch rates (fish/net day) for walleye and largemouth bass annual netting, Lake Powell, 1971-88.

35 CATFISH

Channel catfish (Ictalurus punctatus) and yellow bullheads (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 8-14 inch 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 ips.), and razorback suckers (Xvrauchen texanus) have been sampled. Adults probably migrate into the reservoir to forage before returning to the river where they live most of the time.

STRIPED BASS

Striped bass were first stocked in 1974. Natural reproduction was first detected in 1979 at which time stocking was curtailed 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 3) combined to produce the first signs of striped bass malnutrition. Condition factors for adult striped bass declined to approximately 1.0 (Figure 5). 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 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 zooplankters and maintain good body condition.

The striped bass sport fishery gained wide public acceptance 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. During 1982- 1983 most anglers were happy with their trophies. Despite the poor physical condition of some fish it was still an acceptable fishery.

36 75 76 77 78 79 80 81 82 83 84 85 86 87 88

SAMPLE YEAR

Figure 5. Average condition factor (KU) of adult and juvenile striped bass at Lake Powell, 1975-1988. During 1985 the average size of all striped bass sampled declined 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, 393 mm in 1987, and 348 mm in 1988. Striped bass have increased slightly in physical condition as size decreased. Condition is currently holding near 1.0 to 1.1.

Physical condition and growth of striped bass varied in direct relation to the abundance of threadfin shad (Figures 3 and 5). Shad have failed to produce their expected cyclical peak in abundance in 1987. There has been 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. a u, Unlimited natural reproduction is a mixed blessing. The immediate result was the overcropping of the shad supply with a subsequent decline in e; the quality of the fishery. If forage were less limiting, large striped bass cc could be produced in a quantity substantial enough to satisfy the fishing Pr desires of a much larger angling public than currently utilizes Lake Powell. Increased angling pressure created by a rejuvenated striped bass fishery could RE 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, pers. comm. 1985). Harvesting 1 million 4 pound fish would be a mind boggling wo fishery. ba: cot occ MANAGEMENT OPTIONS per les NO ACTION and hay Taking no action would leave the Lake Powell fisheries about where they to presently exist. Shad reproduction would occur in the turbid water at the Any back of coves and canyons. As yoy shad ventured out of the turbid water they fai would meet intense predation by juvenile striped bass, walleye, black bass, exp and crappie. Shad recruitment would be depressed by predation. Shad would seldom occur in the pelagic zone. Without an open water shad population striped bass growth would remain slow and physical condition would be the marginal. The striped bass population would be dominated by juvenile fish in spil marginal condition, attempting to maintain themselves on zooplankton. A rele substantial harvest of small striped bass (less than 20 inches) would occur bass every 2nd or third year. The striped bass trophy fishery would decline each targf year with fewer individuals recruiting to trophy size. This fishery would be tf closely parallel what is now occurring at Lake Mead. reprc benef Walleye would not recruit in sufficient numbers to create the type of Spill fishery seen in the early 1980's. The lack of a deep cool water forage fish spawn would not allow the type of population expansion necessary for anglers to be to fi predictably Successful in capturing walleye. buoys reest The black bass population would build as smallmouth broodstock become more abundant and produced 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 would remain stable as they

3P 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 would occur. In low water years largemouth recruitment would be poor. Forage would 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.

Black crappie production could 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.

Other fisheries would remain as presently constituted. The remnant adult population of threatened and endangered species that currently use the upper reservoir would remain until those individuals present finally die of old age. No reproduction of these big river fishes has been identified or is expected within the confines of the reservoir. Some limited spawning may occur in the tributaries, but any young produced would be subjected to predation from Lake Powell predators as they venture into the reservoir.

REGULATION CHANGES

Drastic regulation changes aimed at reducing the striped bass population would probably not have the desired effect. Removing the limit from striped bass would 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 could 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 were 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 decrease satisfaction with his fishing experience.

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 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 should be the very fish that should be targeted for harvest before they can reproduce. Reopening the buoy area for the months of April and May would 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 fisherman access and removing the sacks would reestablish the restricted area.

_39 COMMERCIAL FISHERY FOR STRIPED BASS

Creating a commercial fishery for game fish would be a basic de from the philosophy of noncommercialization of protected wildlife whic espoused by both AZ and UT. Selling game fish to restaurants has been recurring problem in Utah. If the sale of striped bass were legalized game fish species could be sold illegally under the guise of legal str bass. The enabling legislation that created Lake Powell specifically commercial fishing within the recreation area.

A more pressing problem is effecting an economically feasible m capturing striped bass commercially. Non selective gill nets could no used because of the impact on nontarget species. Towed nets and purse would be most effective in large bays most often used as play areas by recreationists and fishermen. While it would be possible to effective capture striped bass in commercial netting equipment, conflict and con between commercial fishermen, sport anglers, and boating enthusiasts w substantial from the very outset of a commercial fishing program.

The importance of Lake Powell in generating revenue for the sta UT and AZ from license sales and associated monies spent by those who lake is unquestioned. Those anglers who pay the bills for this fisher exist must be given priority over the needs of a private commercial fi who would need many exclusive guarantees to make his operation economi, successful.

INTRODUCING A DEEP WATER FORAGE FISH

Introducing a forage fish that preferred cool water and primari inhabited the zone at and below the thermocline could be beneficial to various fisheries. Shad, which normally occupy warm shallow zones, wo, probably not compete with a deep water fish for food or space in the stratified reservoir. They would interact in the winter when shad are actively feeding and after shad had obtained a size larger than usuall consumed by the new forage fish. Predatory pressure of striped bass a, walleye would be diverted to the new forage fish allowing the shad pop to rebuild to the extent that food availability would allow.

Plankton availability has not changed dramatically since the on work was done in the 1960's (Sollberger et al. 1989). The productivit allowed large populations of pelagic shad to exist is still present in reservoir. Since a pelagic shad population does not now exist, much o primary productivity of the reservoir is utilized only by pelagic juve, striped bass and inefficiently converted to fish flesh. Most of the p is found above the thermocline. There is plankton in the deep water z, plankton abundance is similar at times to plankton abundance of the Gr Lakes (Table 2) where deepwater forage fish are established.

If a deepwater forage fish were established, the most obvious fi benefit would be walleye and striped bass. Both species would have fo' available in their cool water habitat. They would not have to forage i, warm epilimnion when the lake is stratified. Centrarchids would benef indirectly since shad in the epilimnion would not be shared with adult bass and walleye.

40 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 would occur. In low water years largemouth recruitment would be poor. Forage would 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.

Black crappie production could 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.

Other fisheries would remain as presently constituted. The remnant adult population of threatened and endangered species that currently use the upper reservoir would remain until those individuals present finally die of old age. No reproduction of these big river fishes has been identified or is expected within the confines of the reservoir. Some limited spawning may occur in the tributaries, but any young produced would be subjected to predation from Lake Powell predators as they venture into the reservoir.

REGULATION CHANGES

Drastic regulation changes aimed at reducing the striped bass population would probably not have the desired effect. Removing the limit from striped bass would 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 could 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 were 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 decrease satisfaction with his fishing experience.

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 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 should De the very fish that should be targeted for harvest before they can reproduce. Reopening the buoy area for the months of April and May would )enefit the fisheries and cause no safety problems near the spillways. Spillway operation would not be expected until June in any year at which time ;pawning and congregation of fish near the dam is complete. Opening the area :o fishing could be done without removing the buoys. Simply covering the woys with sacks would allow fisherman access and removing the sacks would 'eestablish the restricted area.

39 COMMERCIAL FISHERY FOR STRIPED BASS

Creating a commercial fishery for game fish would be a basic departure from the philosophy of noncommercialization of protected wildlife which is espoused by both AZ and UT. Selling game fish to restaurants has been a recurring problem in Utah. If the sale of striped bass were legalized, other game fish species could be sold illegally under the guise of legal striped bass. The enabling legislation that created Lake Powell specifically denies commercial fishing within the recreation area.

A more pressing problem is effecting an economically feasible method of capturing striped bass commercially. Non selective gill nets could not be used because of the impact on nontarget species. Towed nets and purse seines would be most effective in large bays most often used as play areas by recreationists and fishermen. While it would be possible to effectively capture striped bass in commercial netting equipment, conflict and contention between commercial fishermen, sport anglers, and boating enthusiasts would be substantial from the very outset of a commercial fishing program.

The importance of Lake Powell in generating revenue for the states of UT and AZ 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 fisherman who would need many exclusive guarantees to make his operation economically successful.

INTRODUCING A DEEP WATER FORAGE FISH

Introducing a forage fish that preferred cool water and primarily inhabited the zone at and below the thermocline could be beneficial to the various fisheries. Shad, which normally occupy warm shallow zones, would probably not compete with a deep water fish for food or space in the stratified reservoir. They would interact in the winter when shad are not actively feeding and after shad had obtained a size larger than usually P_ consumed by the new forage fish. Predatory pressure of striped bass and walleye would be diverted to the new forage fish allowing the shad population to rebuild to the extent that food availability would allow.

Plankton availability has not changed dramatically since the original sh work was done 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 of primary productivity of the reservoir is utilized only by pelagic juvenile poi striped bass and inefficiently converted to fish flesh. Most of the plankton cer is found above the thermocline. There is plankton in the deep water zone and plankton abundance is similar at times to plankton abundance of the Great Lakes (Table 2) where deepwater forage fish are established. Thr 19E If a deepwater forage fish were established, the most obvious fish to bod benefit would be walleye and striped bass. Both species would have forage str available in their cool water habitat. They would not have to forage in the str warm epilimnion when the lake is stratified. Centrarchids would benefit 500 indirectly since shad in the epilimnion would not be shared with adult striped of bass and walleye. nor

40 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 introduction of new forage species would provide more food for all game species.

A deepwater forage fish would have no effect on the remnant adult population of threatened and endangered fish in the reservoir. Since "big river" fish do not reproduce in the reservoir the new forage fish would not interact with yoy endangered species. There may be some interaction of endemic fish with forage fish in the tributaries. The new forage fish may provide food for the adult endemic species.

Downstream migration of a deep water forage fish is likely. It is important that any candidate forage fish would not potentially harm the important tailwater trout fisheries, nor cause irreparable damage to existing fisheries downstream. It is unlikely that a new forage fish would migrate upstream above Lake Powell due to the swift, silty nature of the inflowing rivers. Criteria used in selecting a deepwater forage fish would certaihly take these and other considerations into account. Minimum criteria reviewed prior to an introduction would include but not be limited to: 1) reproductive potential, 2) population stability, 3) trophic efficiency, 4) vulnerability to predation, 5) innocuousness (Ney 1981).

INTRODUCING A 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 TX-OK 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 innularis), black crappie, and various sunfish (Centrarchid sop.). 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 bervllina), drum (Aplodinotus qrunniens), 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 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 is designated as trophy size fish by the OK Department of Wildlife. Striped bass have not detrimentally effected other fisheries, nor have they continued to increase in population abundance until they

41 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 50's. 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 psuedohsarenous), blueback herring (Alosa_ aestivalisl, and various centrarchids, perch (Percidae spp.), 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."

Lake Powell is not Lake Texoma nor Santee-Cooper. There are environmental differences inherent that cause different results to occur. However, other fisheries exist in man-made reservoirs where striped bass have been for over 20 years, where they reproduce, and where they seem to be in balance with the system around them. This fact offers hope that striped bass can, in fact, be managed and live in concert with other fisheries.

Striped bass are not without problems, but they are a permanent part of the Lake Powell and Colorado RivAr fisheries. They cannot be ignored. Attempting to solve striped bass problems through well thought out, thoroughly La researched management schemes could result in a tremendously successful fishery that would complement those fisheries already in place. Lai Failure comes only by giving up hope. We can succeed by making the right choice at the right time.

GRE

Bea

Bul

Lake (aye see

Lake (aver

42 Table 2. Comparison of zooplankton densities (#/W) in the Great Lakes and four reservoirs. Taken from Paulson 1989.

April May June July

Lake Huron -- 1971 lake transect 5,646 5,476 10,427 26,427 (2,315) (2,245) (4,275) (10,835)

-- 1975 S. Lake Huron 9,454 12,980 126,127 184,139 (3,876) (5,322) (51,712) (75,497)

-- 1980 whole lake 12,024 11,471 20,210 131,739 (4,930) (4,703) (8,286) (54,013)

Lake Ontario (1970) 4,585 11,363 17,754 67,320 (1,880) (4,659) (7,279) (27,601)

Lake Erie 30,461 39,600 497,651 347,139 (12,489) (16,236) (204,137) (142,327)

Lake Superior (1973) 3,200 3,500 2,800

Lake Michigan (1979) 19,556 79,980 234,039 -- 76 um net (8,018) (32,792) (95,956)

-- 156 um net 9,366 52,185 164,346 (3,840) (21,396) (67,382)

GREAT LAKES AVERAGE 12,434 14,127 100,979 144,744 (5,098) (6,432) (47,111) (67,659)

Beaver Reservoir (1965-66) 22,600 16,000 19,800 800

Bull Shoals Reservoir (1965-66) 24,600 23,500 13,500 6,500 (1965)

Lake Mead (1988) (average of F2 and F6 stations- see Table 7) 23,085 11,360 7,023 6,173 (10,480) (5,877) (4,234) (2,867)

Lake Powell (1987-88) (average PW01-PW06) 17,613 8,845 • 6,460 (9,059) -- (3,833) (3,388) (Aug)

43 REFERENCES CITED

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, 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, Ut. 35 pp.

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.

Hutchings, John. 1985. Pers.Comm. Nevada Division of Wildlife. State Mailroom Complex, Las Vegas, NV 89157.

May, B. E., C. Thompson, and S. P. Gloss. 1975. Impact of threadfin shad (Dorosoma petenense) introduction of four centrarchids. Utah Division of Wildlife Resources. Pub. No. 75-4. 22 pp.

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

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

Ney, J. J. 1981. Evolution of forage fish management in lakes and reservoirs. Transactions of the American Fisheries Society 110:725-728.

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, UNLV, Las Vegas, NV. 72 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

45

,

:. • • . • . M. ' " e £ QS 9Vsri :..i z fl 229 r •

I Er" r:2rri ."; •

4 1 r '" • " 7„. 9- :' PA. ! Appendix II

ANSWERS TO COMMONLY ASKED QUESTIONS ABOUT RAINBOW SMELT!

STRIPED BASS POPULATION CONTROL

I. Why not reduce striped bass population by commercial fishing?

Enabling legislation that created Glen Canyon National Recreation Area specifically prohibits commercial fishing. It is illegal to sell game fish in UT and AZ. Legalization of selling striped bass commercially puts other white fleshed fish (bass, crappie and walleye) in danger of illegal sale under the guise of striped bass.

The current striped bass population with small fish in marginal physical condition would most likely not be commercially profitable and would only be seasonally available for harvest. Purse seining or trawling would be done in areas of high boat use (bays) as dictated by lake morphology and would not be highly productive as seen by past experience. Negative interactions between commercial fishermen and recreational boaters and fishermen would undoubtably develop.

Gill netting would be the most effective method of harvest but would result in by-catch mortality of non-target sport and endangered species. The importance of Lake Powell in generating revenue for UT, AZ, and NPS from license sales and associated monies spent by those who use the lake is unquestioned. Those anglers and boaters who pay the bills for this recreation area to exist must be given priority over the needs of private commercial fisherman who would need many exclusive guarantees to make his operation economically successful while generating very little revenue.

2. Why not remove the limit from striped bass and increase harvest?

Removing the limit from striped bass would not significantly increase angler harvest since the majority of anglers do not presently catch their limit. It may, in fact, reduce harvest. Anglers want to "catch their limit". They may be willing to spend extra time and effort to achieve some artificial goal of 10, 15 or 20 fish. This extra effort may not be expended if they have no artificial goal to reach. A "no limit" fisheries has less status and less acceptance by the angling public. It may be possible to increase harvest by increasing the limit to a number that is obtainable without placing the limit so high that the average angler usually can not achieve it and, therefore, has less satisfaction with his fishing experience. UOWR is recommending a limit increase to twenty fish to our board for 1990. A similar proposal will be presented in Arizona.

Removing the limit from game fish often results in wasting game, as many fisherman then consider the species a "trash fish" not worthy of harvest or effort to catch. It is not UDWR policy to encourage such attitudes.

47 • , 3. Can the striped b.a. ,s population be`cOntro 140 by interroptingiThe life cycle at some vulnerable stage?

Striped bass are the top level predator in the lake without r natural enemies. Eggs and larvae are the„most,vmlnerable life stage bilt9-sheer'numbers favor striped bass proliferation. Striped bass are pelagic spawnervan& eggs settle onto the substrate wherever they are .spawned,-',:which includes a-,Vsist,areas of Lake Powell. Eggs and larva?- ere iulnerable at this point'trut,'seggt hatch quickly and larvae grow fast.er - itif'il17te:Servoie spawning only -,k'biolngical7 control of lake wide proportilen'ivotilThaVe:anyi .,chance- of success;' '.A „Prolific species that occupies the zone where itapsers spawn and are known to'eat fish eggs and larvae would appeaHthe most `s'erisibie solution (e.g. rainboeinielt). PRODUCTIVITY 9 3 l "' '‘ 1. Odes adequate prOducti,vi,tyexlo li,i,it:iii,jo:.3itAtirt:,;.ak;ailiitional forage ifisin'f' - r - . Sol I berger'. et a) .5.198- 9 stitched'seel ar ti ye"' Plinkton abundance in Lake iiorwell and concluded that While Lake Powell is oligotrophic with3 chl-a near 2 ugh 1 that plankton densities varied between 3,000 and 26,000 m jvtheApper 40 in of the water column. Most of the plankton is confined to the productive surfacejayers but plankton is available, throughoutr the„,mkter- tr,colfumn- , t.,1004 m. Plankton abundance in April; at bake Powell ,Wai 17,60,11/m'compareckAo 23,-000 at Lake ,'Mead, 24,600 at Bull Shoals Aft,nand12,4t0 'average JO „Great• , .4..akes. I K R , - , . c c z Plankton dat`a -a s not.:eayz teeiiim6aPi' duá to different sampling Afienniiluei and reporting Methods. Plankton also peaks at different times in different, locations. It is not easy -nor cost effective i.tRisamplw,planktOn, often enough to record actual population dynamics in'thkkOptypieral animals. Plankton teilds, i ,„,i,1-2 to congregate, and is not evenly diitH4tedwithinta body of water makfng',...., interpretation- of sapplingdata eVelfmei'n, ffi;Filtt.f, But Oven the problems with plankton' datk yie, rtcfh* plankton tetbe''reacy,- 13i.4 vavajlatileveto ',take , Powell fishes: particularlý-.141 S.prin_qtAtielivhen Most ip,k0vAlatespay4TAng,Landfneed plenty of fo&d. n:; • to insure Noy 4 • 2. If piscivorOits,- L' r,stgisied b ( 'bass are Capable of'depressing planktivorous shad why wouldn't they do theysame to smelt? The assumption upon which this question is based is that -plefiktonid production is not adequate to allow shad to withstand piscivorous 9redation, In actuality shad are healthy and . well fed, they ..re :114:4 eiatery ate% mã11 size A Shad nexer oli.itgrow-,the-preferred "prey,sliteigr4tpriikeckfbasst and *in confined to the waters iahovetire., tbermoffifte during rnia;4.,4f the year ;: They -'maintain— themselves in the ;reservbir rbyliicting in•yarp,"i.‘urhid-water where sfelpid- bass , are ineffi.cii*oct mdatonS.09411feif- the annual .yoy shad s crop has been reddeed to cu a point:mherelOrtpedrbais cans no longer* forage profitably on shad, striped bass Sh retreatAi• openwatee.and forage directly on plankton. it Smelt are larger than shad and may grow to a size larger than preferred an by juvenile striped bass. They would retreat to the depths of the lake when faced with severe predatory pressure which _would isolate them from the huge population of juvenile striped bass. With, tmelt utilizing the depths and 'Shad hiding in the shallows there is more than 'twice the possibility of some forage ma fish making it through a full season. Addin9 species diversity spreads the se.

49 predatory burden and increases the chance of forage stability developing. There is also a greater chance that pelagic plankton will be consumed by forage fish instead of direct consNmption by topleVel predators.

SMELT MIGRATION i. i1 r C 9 1 1. Why won't smelt go upstream from Lake. Powell?

OverwliCming evidence shows thit'imelt,,,Hpsctreem migration is stopped by barriers or'rfills with a one foot vertie41',Oro0,,,Jhe, extremely turbulent rapids and fills - Of Cataract Canyon are' nOelk.aVersealyanadramous spawning striped bass during ' their spawning run. Smelt violld hays- no. need to go upstream in, the heavily sill-laden water where adequate 'spawnipOiravel -does not exist when the lake supplileS, all of the smelt spawning requirements.

The San Juan River is not as turbulent and wild as the Colorado but still has rapids that would confine smelt to,the oheaCwaters of Lake Powell. Smelt l also tendi to avoid turbid waters incr ghatild therefore avoid the inflow areas as they have 'done at Lake McConahy NB (D., glli#0n-K,NOraska Game Pish and Parks,,1 pers. comm.) ,0 ' 9*2 r 003 'v9W fl H • 2. Will : smelt go downstream? C 4 T1::D n r 1, a '4 t . T10/J0V SrWt will estabflshTfh 1mpoth,dhients - which strati fy during the summer-. Striped,fress now occupy andrardAhi over stiOpli iri, alt impoundhients in whieh snielt would establish. The increaSed - foWage -base in all of these impoundments would 4 benefit the sport fisheries of the downstrea9mqates in,ther saffier- manner. stated. in this r, iq „ I •■ 3. 1411,1 smelt establish in tributaries agdibackwaters downtrm E vidence from the Missouri9,Wiltq4444, River isystems has shown that smelt will pass through river sstemso r annualtiaMrsi but they do not , establish populations. Smelt 4me_ 4rOcirtOt ,*Age itemvoms[ai hastk ,in, 3 I many blue-ribbon trout ta1lwateVs'intlAllivq40 systenn,-,11,stien-gt-St!ggens that they would improve theeloragetlfilation tfarlivphy trout inlailwater fisheries below 'reservoirs where they became established. They have not had a detrimental - effect on native or exotriitc 11.,mw:zaat,eirl,fish popylations in •a'eive0:system:, • 0 .1 Z.- 17111 SMELT PISCIVORY 1.1,Df y • nor, • . . iv7,1.:F Are sm0 opl7Rgla5eous? ,t2,,, E. :q • • Yes. Smeif4 ats saffol619 '-tlt ite 4va ilable -to them -1 inthetY life zone. Smelt are confined tickEtherAV61 ;iat rnOtthe letatimnicin and' btlOw,Lin' the - strati fi reservai rs that v th4S1 Lake. ; Rowel 1 .f that life zone _is, currently .oCCppied- by adult fish:, edgt aritrrar,ifae of striped.bassiLimi Shad are confined to the epilimnion during stratification Smelt caul on1y üt „. items that are ,available. In this situation smelt could eat other—tmelt, eggs and larvae of striped bass, and plankton.

, There will be an overlap of habitati between smelt and shad' at the thermocline. Shad at this point are surplus fish that will be eaten. It doesn't matter if smelt eat shad and then are in turn eaten. Shad brood stock are still separated"from smelt. Yoy smelt and game fi,Sh may overlap but smelt of this size

-50 are not piscivorous. There may be some competition for plankton between these two groups but we view that as a healthy situation when Lake Powell's pelagic plankton population is presently being utilized only by striped bass.

SMELT IMPACT ON ENDEMIC SPECIES

The potential for smelt to impact the endemic species is discussed in the text of the proposal. Please refer to the section "Potential Dispacement of Indigenous Species."

BAIT BUCKET INTRODUCTION OF SMELT IN OTHER WATERS

Would smelt be moved by anglers to waters where they are not wanted?

Forage fish are not moved illegally as commonly as sport fish. We should give consideration and concern to this possibility but not let this deter the introduction. We currently possess the means to control bait bucket introductions by law enforcement and education programs. We should emphasize the potential impact of smelt on cold water fish populations if used in the wrong water. If other opposition can be overcome, then the merits of the introduction would outweigh the possible negative aspects.

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