American Fisheries Society Symposium 80:15–23, 2013 © 2013 by the American Fisheries Society

History of Management in the

Wayne Gustaveson* and Georg Blommer Utah Division of Wildlife Resources Post Office Box 1446, Page, Arizona 86040, USA

Abstract.—The discovery of landlocked populations of striped bass saxatilis in Santee–Cooper Reservoir, and Kerr Reservoir, Vir- ginia prompted a rush to stock striped bass in other inland waters of the United States, including impoundments in the Colorado River. Fisheries managers re- sponsible for Colorado River waters studied existing literature and predicted that it would be unlikely for successful natural reproduction of striped bass in these systems. Striped bass population development proved unique in the Colorado River system, which is marked by nutrient-poor, well-oxygenated waters with limited forage. Natural reproduction did occur in these reservoirs despite the lack of current previously thought to be essential for successful reproduction, resulting in high survival. Developing populations were sometimes overabundant to the point of forage elimination from pelagic zones. Lack of prey limited growth and temporarily reduced reproduction. Eventually forage returned, increasing striped bass growth and maturity, which led to more reproduction (a “boom and bust” cycle). Planned low-impact, low-abundance adult trophy fisheries produced by managed stocking were replaced by high-abundance juvenile fisheries with high catch rates produced by natural reproduction. In most years, juvenile striped bass living in warm surface waters proved to have the competitive advantage over adults for limited forage.

Colorado River Historical Overview and Burrell 2013, this volume). The last im- poundment was completed in 1963 when Glen The preimpoundment Colorado River was Canyon Dam was closed, forming Lake Powell characterized by harsh environmental condi- (Utah and Arizona), which is 300 km long with tions ranging from muddy spring floods ex- 3 3 a surface area of 65,000 ha when full. ceeding 8,495 m /s to flows less than 8 m /s in The Colorado River watershed is mostly drought plagued summer months. Hoover Dam devoid of agricultural and commercial devel- was completed in 1935, creating , opment, which has been the main cause of the first impoundment on the river and one of nutrient enrichment in many of the nation’s the largest reservoirs by volume in the United impoundments and river systems. Colorado States (Figure 1). At full pool, Lake Mead is River impoundments are characterized by low 63,900 ha with a maximum depth of 177 m phosphorus and nitrogen levels. The new lakes and maximum length of approximately 184 filled deep canyons carved out by the Colorado km. Two smaller but significant reservoirs fol- River with limited littoral zones. Seven native lowed. Lake Havasu (1938) and Lake Mohave species that thrived in the river prior to (1952) were constructed downstream (Stewart impoundment were poorly suited for life in the * Corresponding author: [email protected] new lake environment. Introduced nonnative

15 16 gustaveson and blommer

Figure 1. Map of Colorado River drainage with large reservoirs included. history of striped bass management in the colorado river 17 sport and species dominate the fish tion would not be sufficient to maintain a sport communities that developed in these reservoirs. fishery” (R. Stone, Utah Division of Wildlife Resources, personal communication). Hatchery Striped Bass History rearing ponds were built near Lake Powell to meet the anticipated annual stocking require- Many new impoundments were constructed ment. The initial 1974 stocking in Lake Pow- in the United States between 1930 and 1970. ell came from , California, and North Striped bass Morone saxatilis trapped in Santee– Carolina genetic stock (May and Hepworth Cooper Reservoir (South Carolina) impound- 1975). Over time, most of the fish stocked in ments and Kerr Reservoir (Virginia–North Car- Lake Powell came from North Carolina and olina) survived and reproduced (Van Horn 2013, the California Delta stock (Hepworth et al. this volume). Land-locked striped bass provided 1976; Gustaveson et al. 1979). fisheries managers a top-level predator that pro- duced charismatic trophy fish for anglers while Natural Reproduction controlling overabundant forage fish popula- tions. A nationwide rush to stock striped bass in Based on the literature (Bailey 1975), biologists reservoirs ensued as fish managers hoped to reap stocking Colorado River reservoirs believed the biological and recreational rewards. Biolo- that most reservoir striped bass populations gists in the Southeast quickly determined that were not self-sustaining. Most thought that most striped bass populations in reservoirs failed fingerling introductions would be required to to reproduce because the semibuoyant eggs support a continuing sport fishery. However, in would settle to the bottom without supporting the late 1970s, reports from Arizona and Ne- water currents and die due to siltation or lack of vada suggested that evidence of striped bass dissolved oxygen. Barkuloo (1970) proclaimed natural reproduction had been found. Striped that “striped bass eggs and larvae must be sus- bass reproduction in Lake Mead was first pended by current to prevent settling and death noted in 1973 and in every year since (Allan by suffocation.” This finding guided managers in and Roden 1978). Possible spawning sites in- the Colorado River basin who contemplated in- cluded areas where river current could suspend troduction of striped bass. eggs and larvae, as the literature suggested, but Biologists at the California Department of spawning sites were also suspected in reservoir Fish and Game stocked the first striped bass into locations with minimal current. The Lake Mead the Colorado River in 1959 (St. Amant 1959). analysis by Allan and Roden (1978) referenced Young-of-year striped bass were seined from the an important but overlooked hatchery experi- San Joaquin River Delta and transported over- ment conducted by Bayless (1968) confirming land to the Colorado River near Blythe, Califor- that “suspension of striped bass eggs by water nia. All stocked striped bass were descendants of current is not necessary for a successful hatch fish that were transported from the East Coast in provided eggs are not subjected to suffocation 1879 and stocked in the delta near San Francisco by silt or water quality.” Bay. Collaborative stocking efforts from 1962 to Evidence of striped bass natural reproduc- 1969 by state wildlife agencies in Arizona, Cali- tion in Lake Powell was first discovered in 1979 fornia, and Nevada created thriving striped bass and annually thereafter. Initially, it was thought populations in Lake Mead, Lake Havasu, and that reproduction was confined to the Colorado the connecting river reaches (Edwards 1974). River above the lake where river current could Popular striped bass sport fisheries developed, suspend eggs and larvae. The spawning site was which included trophy-sized adults. in or below Cataract Canyon, a 19-km gorge Striped bass were stocked by the Utah Di- containing 23 sets of rapids. Striped bass ap- vision of Wildlife Resources in Lake Powell in parently used less than 20 km of river above the 1974. It was initially thought that “reproduc- reservoir because ripe striped bass adults were 18 gustaveson and blommer collected below but not above Cataract Canyon density current in the reservoir that could not during spawning season (Persons and Bulkley have assisted in moving larvae from the inflow 1982). any closer to the dam than 190 km (D. Mer- During spring 1979, striped bass - ritt, U.S. Bureau of Reclamation, personal com- ing was discovered in the lower reservoir near munication). Instead, striped bass larvae were the dam. In spring of most years, prespawn- captured 295 km downstream from the inflow. ing striped bass aggregated near Glen Canyon If spawning occurred only at inflow areas and Dam. These fish seemed attracted to the cur- larval fish were distributed by reservoir cur- rent created as water was drawn through the rents, then larval fish should have been found dam penstocks. With time and warming, the throughout the reservoir. In contrast, there was aggregation left the 165-m-deep dam forebay a preponderance of young striped bass at two and moved to nearby coves where spawning oc- distinct locations, the inflow and again at the curred. Most fish left the prespawning staging dam. It was evident from these analyses that area simultaneously during early May as water these young striped bass found near the dam surface temperature reached 16–19°C, which were the result of successful in-reservoir spawn- is the generally accepted peak spawning tem- ing (Gustaveson et al. 1984). perature range (Setzler et al. 1980). Spawning Over the years, it has been confirmed that sites were located near the dam where floating striped bass spawning occurs annually in Lake masses of dead (unfertilized) eggs were clearly Powell, Lake Mead, Lake Mohave (Liles 1985), visible. J. D. Bayless (South Carolina Wildlife and Lake Havasu. Eggs and larval striped bass and Marine Resources Department, personal also pass through the dams to provide addi- communication) found that unfertilized eggs tional recruits to downstream lakes and canals would float but that immediately after fertiliza- as water is delivered from the Colorado River tion, eggs would sink 0.3 m in 27 s. Settling to locations in California, Nevada and Arizona rate slowed with time, but eggs still descended (Stewart and Burrell 2013). 0.3 m every 60 s some 24 h after fertilization (Gustaveson et al. 1984). Population Dynamics An oxygen-temperature profile taken in spawning coves near the dam showed oxygen Initial growth of Lake Powell and Lake Mo- levels of 8.4 mg/L near the surface and 13.2 have striped bass was comparable to other fast mg/L on the substrate in 9 m of water. Siltation growing cohorts in the United States (Liles was insignificant in these coves on the rock and 1985; Gustaveson 1999). Striped bass spawn- sand substrate during the brief 48-h incubation ing was first discovered in Lake Powell in 1979, period (Hardy 1978). Thus, eggs settling on the and stocking was terminated that same year. bottom of Lake Powell had adequate oxygen petenense the only pe- for normal development. lagic forage fish in Lake Powell, were well es- Collection of larval striped bass 18–22 mm tablished before striped bass were introduced, total length (TL) with midwater trawl and me- having been stocked in 1968 and 1969 to pro- ter tow net samples confirmed successful repro- vide forage for reservoir centrarchids and the duction of striped bass near the dam. The col- anticipated introduction of striped bass (Gus- lected larvae were determined not to be derived taveson 1999). By 1982, threadfin shad stocks from the river upstream of the reservoir. Prolar- were reduced, likely by predation from the vae are capable of swimming at 4 d of age and rapidly growing striped bass population. From could be expected to travel great distances if as- 1982 to 1990, pelagic shad remained in low sisted by strong mainstream reservoir currents. abundance and were often eliminated entirely However, studies of density currents using total from open water, presumably by striped bass dissolved solids as an indicator showed a weak predation (Figure 2). Shad persisted in warm history of striped bass management in the colorado river 19

Figure 2. Pelagic shad abundance (vertical bars) compared to adult and juvenile striped bass con- dition, K(fl) (K factor based on fork length), 1976–2011, Lake Powell.

thermal refuges in turbid water in the backs ited a population peak every third year with two of many canyons where striped bass foraging moderate production years in between. Shad success was limited. Growth of striped bass population peaks in 1981 and 1984 resulted decreased during periods of low forage (Gus- in high cohort survival, increased growth, and taveson 1999). Adult striped bass suffered mal- improved physical condition of striped bass. nutrition while young striped bass maintained Condition of striped bass declined in 1982 and body condition on a zooplankton diet (Figure 1985–1989 to levels where adult fish were thin 2). As striped bass numbers peaked and forage and juvenile fish smaller than expected. fish abundance declined, back-calculated to- Juvenile striped bass were able to maintain tal length of each age-class declined 100–125 higher condition than adults partly because they mm compared to lengths observed in the first occupied the same niche as shad in the warm 5 years of striped bass expansion. Striped bass epilimnion. When adult and juvenile striped were shorter and did not live as long, and some bass competed for limited shad resources that never gained sexual maturity. Most of the popu- were located in the pelagic epilimnion, smaller lation was composed of immature fish 300–400 fish thrived while condition of adults declined. mm TL, which were as young as age 2 or as old Adult striped bass preferred cooler tempera- as age 6 (Gustaveson 1999). When Lake Powell tures and were forced into deeper, cooler water shad abundance increased in 2002, striped bass of the metalimnion and away from shad (Cou- growth and condition immediately improved. tant 1985, 2013, this volume; Thompson and Striped bass condition (K factor based on Rice 2013, this volume). Juvenile striped bass fork length [K(fl)]) in Lake Powell (Gustaveson resided in and tolerated the warm surface lay- 1999) correlated with shad abundance (Figure ers. The ontogenetic separation of striped bass 2). The initial expanding population (1975– size-classes favored juvenile fish at the expense 1981) was consistently healthy, with K(fl) near of adults. 1.3 despite cyclical swings in shad abundance. Colorado River striped bass fisheries are Prior to striped bass establishment, shad exhib- thus characterized by a boom and bust cycle. 20 gustaveson and blommer The initial stocked or naturally reproduced A thriving gizzard shad population was es- striped bass fed on abundant threadfin shad tablished and remains in Morgan Lake today populations, grew rapidly with high condition (Knowles 2002). Some gizzard shad escaped factors, matured, and spawned. Shad popula- into the San Juan River during flood events and tions then declined, and striped bass were less moved downstream to Lake Powell. Gizzard well fed. Spawning decreased when schooling shad apparently from Lake Powell were found adult striped bass with poor body condition in Lake Mead in 2008. This larger pelagic for- probably were no longer able to produce viable age fish likely will pass through the dams and eggs (similar to that observed by Coutant 1987 river system until it invades all Colorado River in Tennessee). Adult striped bass numbers de- impoundments downstream from Lake Powell, clined in years of forage shortage, but a relatively which will in turn influence the predator–prey small successful year-class was produced annu- relationships for striped bass in each of these ally as a few females exceeding 10 kg spawned reservoirs. From the experience in Lake Pow- with young precocious males. These fast-grow- ell, it appears that additional forage provided ing females grew to larger size and were able to by gizzard shad will be advantageous to striped consume pelagic common carp Cyprinus carpio bass in forage-poor years and waters. Gizzard and sport fish of a size unavailable to the major- shad adults eat benthos and grow beyond the ity of schooling striped bass due to mouth gape mouth gape of all but the largest stripers in limitations. Threadfin shad abundance eventu- the system. In 2009, for instance, gizzard shad ally rebounded, allowing rapid growth, followed added significantly to the forage base of Lake by spawning of the remaining striped bass. Powell. The ratio of gizzard shad to threadfin Similar population swings were seen in shad captured in midwater trawl samples was each impoundment from Lake Powell to Lake almost equal. How the boom-bust cycle will be Havasu. In most years, juvenile striped bass affected in the Colorado River basin is unclear. dominated the fish assemblage, with larger Both threadfin and gizzard shad occupy many numbers of adults occurring on occasion. Lake Southeast reservoirs where striped bass and Mohave has the best habitat conditions for a striped bass hybrids currently thrive without sustained population of larger adult fish in the such a boom and bust population cycle. upper lake, which is fed by the constantly cold oxygenated tailwater released from Hoover Management Implications Dam (Stewart and Burrell 2013). Shad forage has been absent from Lake Mohave for the past Striped bass were introduced into the Colorado decade, resulting in a striped bass population River basin 50 years ago. Results differed from composed of fish less than 350 mm existing expectations of those who planned the intro- on plankton and trophy adults that forage on ductions, both for population management via stocked rainbow trout and other fish species not stocking and for development of a fishery for available to smaller stripers. Fish size and con- trophy-sized striped bass. Natural reproduction dition fluctuates in Lakes Mead, Havasu, and outpaced the planned stocking program. A few Powell, depending on forage abundance during large trophy fish (20–27 kg) were taken shortly each particular year. after the initial introductions but are now un- The unintentional introduction of gizzard common. Nonetheless, some striped bass ex- shad D. cepedianum into Lake Powell in 2000 ceeding 13 kg are still taken each year from the added an additional pelagic forage fish that various impoundments. may affect the boom and bust cycle. Gizzard More importantly, striped bass weighing shad were present in a load of from 1 to 2 kg are very abundant, depending on from a federal fish hatchery in Texas, which the lake and year, and provide a popular fish- were stocked into Morgan Lake, New Mexico. ery. The trophy fish goal has been replaced by history of striped bass management in the colorado river 21 quality where many fish are caught. In (Lamprecht et al. 2013, this volume). In each Lake Powell, there is no striped bass creel limit, case, a fishery for young fish has predominated allowing those so inclined to harvest more than over a fishery for large, trophy-sized fish. 100 fish per day (Figure 3). In Lake Mohave, A Web page, www.wayneswords.com, is there is no limit on striped bass less than 500 devoted to providing Lake Powell fishing and mm. Liberal creel limits exist in all Colorado recreational information to the angling public. River lakes. In years of low forage, creel sur- The goal is to provide detailed and timely infor- vey catch rates exceeding two fish per hour are mation to Lake Powell fishers, allowing them common. Management plans for such prolific to catch more fish, especially striped bass. As populations that can overwhelm the forage base 3 million visitors come to Lake Powell each require maximizing harvest. Innovative plans to year, those that would not normally fish while balance predator and prey numbers include lib- enjoying a recreational trip are encouraged to eral catch regulations combined with informa- try fishing. The Web site has been successful as tion dissemination to encourage more anglers evidenced by many fishers who have received to participate in harvesting striped bass. fishing information and found it helpful. They There have been other inland locations are now submitting personal, successful fishing where natural reproduction, either known in ad- techniques and locations to the Web site, keep- vance or unexpected, has dictated management ing the information current and broad-based. plans for striped bass. The most well known are It is common for results of a successful fishing Lake Texoma (Texas and Oklahoma), John S. trip to be displayed on the Internet in a mat- Kerr (Virginia and North Carolina), and the ter of hours. Arriving anglers with Internet or Santee–Cooper reservoirs (South Carolina) “smart phone” access can immediately use the

Figure 3. Angler harvest of striped bass in Lake Powell, Utah–Arizona, estimated by creel survey. 22 gustaveson and blommer information about a hot fishing technique or ceedings of the 28th Annual Conference location. In the age of catch and release else- Southeastern Association of Game and Fish where, the opportunity to “catch and keep” in Commissioners 28(1974):54–68. Colorado River reservoirs is a bonus. Barkuloo, J. M. 1970.Taxonomic status and repro- Anglers of all skill levels come from across duction of striped bass (Morone saxatilis) in the United States to harvest striped bass dur- Florida. U.S. Bureau of Sport Fisheries and ing times of high abundance. Colorado River Wildlife, Technical Paper 44, Washington, reservoirs often have a mix of shad and striped D.C. Bayless, J. D. 1968. Striped bass hatching and hy- bass schools in surface feeding events (striper bridization experiments. Proceedings of the boils) that are exciting to the fishing public and 21st Annual Conference Southeastern As- glamorous enough to entice nonfishers to join sociation of Game and Fish Commissioners in the sport. The end result is increased harvest 21(1967):233–244. and license sales. At Lake Powell, harvest is Blommer G. L., and A. W. Gustaveson. 2007. limited only by the will of the angler to care for Lake Powell fisheries investigations. Utah the number of fish caught. Since striped bass Division of Wildlife Resources, Completion are often the largest fish ever caught by many report, May 2004–April 2007, Salt Lake City. anglers, the fishery is extremely popular. In Coutant, C. C. 1985. Striped bass, temperature, 2006, 1.67 million striped bass were harvested and dissolved oxygen: a speculative hypoth- (Blommer and Gustaveson 2007). Compara- esis for environmental risk. Transactions tively, in 2009, a high forage abundance year, American Fisheries Society 114:31–61. harvest was estimated to be 700,000 striped Coutant, C. C. 1987. Poor reproductive success bass at Lake Powell. of striped bass from a reservoir with reduced In summary, striped bass reproduce within summer habitat. Transactions of the Ameri- the main stem reservoirs and the connecting can Fisheries Society 116:154–160. Colorado River and its tributaries. Low nutri- Coutant, C.C. 2013. When is habitat limiting ent loading provides adequate oxygen on the for striped bass? Three decades of testing substrate for settling eggs to hatch. This makes the temperature–oxygen squeeze hypothesis. striped bass populations within the Colorado Pages 65–91 in J. S. Bulak, C. C. Coutant, and J. A. Rice, editors. Biology and management River system nearly unique. Management of this of inland striped bass and hybrid striped bass. prolific species must address adequate harvest to American Fisheries Society, Symposium 80, prevent stunting or death by starvation. Fisheries Bethesda, . are cyclical with great population fluctuations. Edwards, G. B. 1974. Biology of the striped bass Predator populations periodically recover and Morone saxatilis in the lower Colorado River rebound creating periods of low or high fish har- (Arizona–California–Nevada). Master’s the- vest, depending on prey population abundance. sis. Arizona State University, Phoenix. Fisheries vary but are generally classified as suc- Gustaveson, A. W. 1999. Cyclical population dy- cessful and highly sought after by those desir- namics of self-sustaining striped bass in Lake ing a unique experience of fishing for a highly Powell, Utah-Arizona, 1974–1998. Utah Di- favored game fish in the incredibly beautiful red vision of Wildlife Resources, Salt Lake City. rock country of the desert Southwest. Gustaveson, A. W., T. D. Pettengill, M. J. Otten- bacher, and R. S. Stone. 1979. Lake Powell References post impoundment investigations. Utah Di- vision of Wildlife Resources, Annual Per- Allan C. A., and D. L. Roden. 1978. Fish of Lake formance Report January 1978–December Mead and Lake Mohave. Nevada Department 1978, Publication Number 79–8, DJ Project of Wildlife, Biological Bulletin No. 7, Reno. F-28-R-7, Salt Lake City. Bailey, W. M. 1975. An evaluation of striped bass Gustaveson, A. W., T. D. Pettengill, J. E. Johnson, introductions in the southeastern US. Pro- and J. R. Wahl. 1984. Evidence of in-reser- history of striped bass management in the colorado river 23 voir spawning of striped bass in Lake Powell, North American Journal of Fish Manage- Utah–Arizona. North American Journal of ment 2:403–408. Fisheries Management 4:540–546. Setzler, E. M., W. R. Boynton, K.V. Wood, H. H. Hardy, J. D., Jr., 1978. Development of of Zion, L. Lubbers, N. K. Mountford, P. Frere, the Mid Atlantic Bight: an atlas of the egg, L. Tucker, and J. A. Mihursky. 1980. Synopsis larval and juvenile stages. Volume III. U.S. of biological data on striped bass, Morone sax- Fish and Wildlife Service, Biological Servic- atilis (Walbaum). NOAA (National Oceanic es Program, FWS/OBS-78/12, 394 p, Wash- and Atmospheric Administration) Technical ington, D.C. Report NMFS (National Marine Fisheries Hepworth, D. K., A. W. Gustaveson, R. Biggins. Report) 433. 1976. Post impoundment investigations. St. Amant, J. A. 1959. Striped bass introduced Utah Division of Wildlife Resources, Annual into the Colorado River. California Depart- Performance Report January 1975, Publica- ment of Fish and Game 45:353. tion Number 76–21, DJ Project F-28-R-4, Stewart, W. T., and M. Burrell. 2013. Striped bass Salt Lake City. dispersion and effects on fisheries manage- Knowles, S. 2002. Fish and Wildlife blunders in ment in Lakes Mohave and Pleasant, Colora- Lake Powell. Salt Lake Tribune (August 27). do River basin. Pages 431–448 in J. S. Bulak, Lamprecht, S. D., M. D. Mauck, and V. J. DiCen- C. C. Coutant, and J. A. Rice, editors. Biol- zo. 2013. Natural reproduction: how it has af- ogy and management of inland striped bass fected striped bass management of John H. and hybrid striped bass. American Fisheries Kerr and Santee–Cooper reservoirs and Lake Society, Symposium 80, Bethesda, Maryland. Texoma. Pages 413–430 in J. S. Bulak, C. C. Thompson J. S., and J. A. Rice. 2013. The rela- Coutant, and J. A. Rice, editors. Biology and tive influence of thermal experience and for- management of inland striped bass and hy- age availability on growth of age 1–5 striped brid striped bass. 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