title
Lake Powell post-impoundment investigations : 1978 annual performance report
author
Array ( [0] => Gustaveson, A. Wayne [1] => Pettengill, Thomas D. [2] => Ottenbacher, Michael J. [3] => Stone, Roderick )
abstract
UDWR Publication Number 79-8
date
1979-01-01
organization
Utah. Division of Wildlife Resources
species
Array ( [0] => Not Specified )
file_path
https://grey-lit.s3.wasabisys.com/lake-powell-post-impoundment-investigations-1978-annual-performance-report.pdf
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https://grey-lit.s3.wasabisys.com/lake-powell-post-impoundment-investigations-1978-annual-performance-report-pdf-1-788x1024.jpg
content
N 4650P6.13: Lak / q 7 ~ UTAH OEPOSITOR't SYSTEM Lake Powell NOV2o m79 AH STATE LIBRARY ostimpoundment Investigations .. 1978 Annual Performance Report Utah Division of Wildlife Resources Publication Number 79-8 Dingell-Johnson Project Number F-28-R-7 LAKE POWELL POSTIMPOUNDMENT INVESTIGAT IONS Annual Performance Report January 1978 - December 1978 A. Wayne Gustaveson Project Leader Thomas D. Pettengill Project Biologist Michael J. Ottenbacher Project Biologist Roderick Stone Supervisor Fisheries Research Publication Number 79-8 Dingell-Johnson Project Number F-28-R-7 [email protected] UTAH STATE DIVISION OF WILDLIFE RESOURCES 1979 An Equal Opportunity Employer Douglas F. Day Director TABLE OF CONTENTS Page LIST OF TABLES . iii LIST OF FIGURES v INTRODUCTION JOB NUMBER I. THREADFIN SHAD STUDY 3 Background 3 Methods 4 Results 7 Discussion 7 References Cited 13 II. MEASUREMENT OF FISHERIES HARVEST, PRESSURE, AND SUCCESS 14 Background 14 Methods 14 Resul ts 16 Discussion 20 References Cited 26 III. INDEX TO ANNUAL FISH POPULATION TRENDS 28 Background 28 Methods 29 Resul ts 31 Annual Netting 31 Electrofishing 33 Discussion ... 33 Page Recommendations 38 References Cited 39 IV. STRIPED BASS CULTURE 40 Background 40 Methods 41 Results 43 Discussion 46 Recommendations 48 References Cited 49 V. EVALUATION OF STRIPED BASS INTRODUCTIONS 50 Background 50 Methods 50 Results 51 Discussion 52 References Cited 56 ii Table 1. 2. , 3. LIST OF TABLES Mean biomass (g ) per t r awl tow of young- of - the- year thread fin shad co llected be- tween June and October 197 8 . .. . Surface temperatur es at the th r ee sites during May and June of 1977 1978 . . . . . . . • . . . . trawling and ~st imated fishing pr essure (angler trips)~ by access area and month , Lake Powell , March- September 1978 ...... .. . . 4 . Catch rates (fish/angler hour) by species Page · • . . . . 11 11 • · . . . . . 17 and access area , Lake Powell , March- September 1978 . . . . . . . .. .... . . . .. 19 5 . Catch rates ( f i sh /angler ho ur ) by species and month, Lake Powel l , March- September 1978 . . . . . . .. . ...... 20 6 . Corrected est imates of fishing pressur e (angler tr i ps ) by access ar ea and month , Lake Powe l l , April-September 1977 . .... . .. . .. 23 7 . Numbe r and catch r ate ( i n pa r entheses) of fish caught in gill nets , Lake Powell , March 1978 . Catch rates are in fish per net • . . . 8 . Numbe r and mean catch r ate ( in parentheses ) of fish caught by electrofishing, Lake Powell, August- September 1978 . Catch rates · • . . . . 32 are fish per hour of electro fishing . . . . . . . . . . 34 9. Catch rate and the pe r centage of the catch by species and year , annual gi ll netting , Lake Powell, 1971 -1 978 . . . . . . . . . . . . . . 36 10. Young-of-the-year bass and crappie per hour of electro fishing for August-September 1977 and 1978 , Lake Powell ...• . 38 11. Fertil i zation rates of cultur e po nds, 1978 42 12. Production of fingerl i ng striped bass, 1978 44 13. Stocki ng record of striped bass introduced i nto Lake Powell . . . . . . . . . . . . 52 iii Table 14. Comparison of growth rates from various studies. All to total length .. . . . of striped bass data converted 15. Food habits, by season, of striped bass collected in Lake Powell during 1911 and Page 53 1918 . • .• . . • • . • . . . . • . . . • • . . . . . 55 • iv .... Figure 1 . 2. 3. LIST OF FIGURES Lake Powell showing trawling locations Mean number of young-of-the-year shad captured per trawl haul in Wahweap Bay • . • . . . . . . Mean number of young-of-the-year shad captured per trawl haul in Bullfrog Bay . . . . . 4. Mean number of young-of-the-year shad captured Page 6 8 9 per trawl haul at Hite . . . . . • .. • . • . 10 5. Residence of anglers censused at Lake Powell, March-September 1978 by access area. . •.•. 18 6 . Indices of total recreational boat use and angling pressure, Lake Powell, 1965-78 .•.. . 22 7 . Mean catch rates for all species, largemouth bass and black crappie during April, May and June 1965-78, Lake Powell . . .. • .•..•.. . 24 8 . Species composition by percent of the average Lake Powell angler's creel 1964-78 .... .. 25 9. Lake Powell showing electrofishing and annual netting locations . . . . . . . • . . • . 30 10. Catch rates (fish/net) of largemouth bass and walleye fr om annual netting 1971-78, Lake Powell ... 35 11. Timing of fry introduction in relation to stage of nauplii copepod abundance. Production of fingerlings per acre listed for each pond ... • 45 v INTRODUCTION This report is submitted as a progress report for fisheries investi- gations conducted on Lake Powell by the Utah Division of Wildli'fe Resources from January 1 through December 31, 1978. The project was funded, in part, by Federal Aid to Fish and Wildlife Restoration, Project Number F-28-R. Fisheries investigations on Lake Powell began in July 1963, shortly after impoundment, and have continued to the present. Much of the initial work included physical and chemical descriptions of the reservoir and life history work on game species as sport fisheries developed. Current work has included evaluations of established fisheries, population studies of threadfin shad (Dorosoma petenense) and creation of a striped bass (Morone saxatilis) fishery. A regular creel census program was conducted to measure the magnitude and nature of sport fishing pressure and success. Largemouth bass (Micropterus salmoides) and black crappie (Pomoxis nigromaculatus) remained the dominant species creeled. Annual netting surveys were conducted to assess annual trends in game fish population dynamics. Bass numbers remained high, along with plentiful numbers of walleye (Stizostedion vitreum vitreum). A study of thread fin shad was begun to better understand the nature of this important forage species that has become the dominant food item for most of the reservoir's game species. 2 Experimental striped bass culture was conducted to develop techniques for raising fry to fingerling size suitable for stocking in Lake Powell. For the fifth consecutive year, fingerlings raised from cultural experiments were stocked in the reservoir. Striped bass interaction with its environment and contribution to the creel have been studied since initial introduction in 1974. Background THREADFIN SHAD STUDY JOB 1 Threadfin shad are the most important forage fish in Lake Powell. Shad were first introduced into Lake Powell in 1968 and subsequently became the predominant food item of all major game species (Hepwor th and Gloss 1976; May et al. 1975a and 1975b). Shad are typically pelagic and not readily sampled with conventional entrapment gear. The major objective of this study was to develop, through midwater trawling, an adequate system for sampling threadfin shad. Data collected in 1976, 1977 and 1978 were used to determine shad population indices and monitor monthly and annual population fluctuations. Additional information was obtained on shad spawning periodicity. Striped bass, a pelagic predator, were introduced into Lake Powell in 1974 to utilize the dense shad population. Previously established game fishes generally were restricted to the littoral zones of Lake Powell. Threadfin shad population data collected in 1976, 1977 and 1978 will form a baseline for future comparisons in determining possible impacts of the expanding striped bass population on thread fin shad abundance. 4 Methods Trawling was performed with an 8.53 m (28 ft) steel-hulled work boat. Two Marco W0650 hydraulic winches powered by Vickers hydraulic pumps were run directly from the boat's inboard engines. Dual controls made it possible to run both winches in tandem or individually. The trawl was designed after that described by von Geldern (1972). It measured 3.05 m (10 ft) square at the mouth, 15.24 m (50 ft) long with bar mesh net tapering from 20.3 cm (8 in) in the throat to 0.32 cm (1/8 in) at the cod end. A pair of depressors and hydrofoils, attached at the corners of the mouth, functioned to hold the net open while fishing. Galvanized wire rope cables (0.48 cm dia.; 3/16 in) running from each winch were used in deploying and retrieving the trawl. A standard tow was developed and used to permit consistent sampling and replication. During each tow, the boat was operated at 1,100 rpm's (1.6 mlsec or 3.6 mph) while 60.96 m (200 ft) of cable was played out and immediately retrieved. The average volume of water sampled was 8,178.44m3 (288,597 ft 3), and the maximum depth fished was about 10.7 m (35 ft). The oblique tow allowed equal sampling of the water column from the surface to maximum depth, rather than sampling shad from anyone depth. For consistency, sampling was done at night when shad were distributed in a dense and uniform pattern in the epilimnion, rather than grouped in schools as found during the day (Houser and Dunn 1967; Netsch et al. 1971). Sample nights were selected during the period between new moon and first quarter to ensure dark nights and eliminate variability caused by moonlit nights. 5 Three trawling transects were selected to sample lake areas near the dam (Wahweap) midway uplake (Bullfrog) and near the Colorado River inlet (Hite) (Fig. 1). Wahweap Bay was sampled two nights per month and Bullfrog and Hite were sampled one night per month . Wahweap, Bullfrog and Hite were sampled on consecutive nights to allow comparison under approximately similar times and conditions. Four standard tows were made per sample night. Lighted buoys, permanently fixed in position, were used to mark trawl transects. One sonar transect was run each sample night before trawl samples were taken. The boat was operated at an idle speed of 800 rpm's for a period of eight minutes, while sonar transects were run over the t rawl ing course . The trawl selectively captured larval and juvenile shad with adults taken infrequently. Larval and juvenile shad were differentiated by total length after criteria presented by Barnes ( 1977) . Larval shad were designated as shad smaller than 25 mm (1 in ) while juveniles were between 25 mm and 50 mm (2 in). All shad collected were immediately preserved in a 10% formalin solution. Number of fish, weight of catch , average total length and range were determined for each haul. Monthly temperature profile data were collected using an ARA Model FT-2 electronic the rmometer. Temperature profiles were made at each of the three regular trawling locations. Temperatures were measured at one- foot intervals between the surface and 100 feet. II) c: .2 -CII g 6 ~ .-- ~ ... - 7 Results Shad were first observed spawning at Wahweap on 15 May 1978 and at Bullfrog on 29 May 1978. A very heavy spawning run was observed at Bullfrog on 7 June 1978. No spawning observations were made at Hite. At least a few adults continued to spawn at all three locations until August 1978. • • Larval shad were first collected at Wahweap on 5 July and at Bullfrog on 6 July 1978. No collections were made at Hite until 3 August 1978 because of vast quantities of driftwood flushed downstream with the high spring runoff. Larval shad were collected at Wahweap and Hite through the first week of October . No larval shad were found at Bullfrog after the first week of September. Young-of-the-year shad populations peaked at Wahweap in August, Bullfrog in September and probably October at Hite (Figs. 2 , 3 and 4). Peak densities we re 257 y-o-y shad/1,000 m3 at Wahweap, 324 y-o-y shad/1,000 m3 at Bullfrog and 660 y-o-y shad/1,000 m3 at Hite, representing increases of 40-180% above the 1977 maximum populations. Changes in biomass general ly followed monthly population trends (Table 1). Monthly biomass values at Bullfrog and Wahweap were well above last year while values at Hite showed a slight increase. Discussion Hepworth et al. (1978) reported that during the spring of 1977 , shad spawning began near Hite and proceeded downlake towards Wahweap. • 2400 1978 • 2000 I .. • 1600 "3 CIl J: '- Q) a.. "0 1200 CIl .c (f) -0 • , T'-. • '- Q) . / -...... 1977 .0 800 E / . • :::J \ z c , CIl // , Q) , ~ , \ 400 , , , , 1976 \ 0...1 • • T ------, i June July Aug. Sept . Months Figure 2. Mean number of young-of-the-year shad captured per trawl haul in Wahweap Bay. 8 • Oct . 9 2800 1978 • 2400 2000 • :::J • co J: .... Q) Cl. 1600 "0 co ..c (/') -0 .... Q) 1200 .Q E :::J Z c: co Q) :::E 800 1977 ,. " " " • .'" 400 o~ ____ ~ ______ ~ ____ ~ ______ ~ ____ ~ June July Aug. Sept Months Figure 3. Mean number of young-of-the-year shad captured per trawl haul in Bullfrog Bay. Oct. 5600 4800 4000 ::l ~"" 1977 0 ~ 60 4 0 20 - - T O T A L B O A T S - - - - F IS H IN G B O A T S ". -- -- .... /' ~ . - . - " -- -- -- -- -- -- -- -- - , .- r - - - - - - ... -.. .... . "" ..... " " " ' . . . . ; ' , -- -- - " " 1 9 6 5 1 9 6 6 1 9 6 7 1 9 6 8 1 9 6 9 1 9 7 0 1 9 7 1 1 9 7 2 1 9 7 3 1 9 7 4 1 9 7 5 1 9 7 6 1 9 7 7 1 9 7 8 YE AR F ig u re 6 . In d ic e s o f to ta l re c re a ti o n a l b o a t u se an d an g li n g p re ss u re , L ak e P o w e ll , 1 9 6 5 -7 8 . N N 23 Table 6. Corrected estimates of fishing pressure (angler trips) by , access area and month, Lake Powell, April-September 1977 . Month Wahweap Bullfrog Hall's Hite Total Percent April 9,432 15,458 7,822 9,317 42,029 18.7 May 33,900 17,554 8,418 7,089 66,961 29.8 June 25,316 6,023 4,099 9,283 44,721 19.9 July 13,383 3,915 1,104 4,480 22,882 10.2 August 10, 394 3,072 1 ,772' 2,280 17,518 7.8 September 8,953 6,721 3,827 10,986 30,487 13.6 Total 101,378 52,743 27,042 43,435 224,598 100.0 Since annual netting data from 1971-78 (see Job II I ) provide an index of the numbers of largemouth bass, factors other than those affecting the absolute numbers of catchable-sized bass are influencing angler catch rates. Spearman's rank correlation coefficient (Snedecor and Cochran 1971) showed no significant correlation (5% level) between annual netting catch rates and angler catch rates from 1971-78. Although angler success has been relatively low for the past several years , there was also no significant correlation between success and reservoir age as measured by the above test. Analysis of the species composition of the average anglers' creel also failed to provide any obvious clues as to the cause(s) for the decline in angler catch rates (Fig. 8). The composition of the catch has not changed appreciably since the early 1970's. Angler success is most likely affected by a combination of the factors mentioned above, with certain variables becoming more important than others in a given year. Nonetheless, the steady decline in catch rates since 1975 warrants continued attention and efforts to more clearly define probable causes. ~ ~ 0 :t: ..: '" ,..., to :ii , :t: til H ~ ~ '" H i:l tI: u H ...: u 1 .3 1 .2 1 .1 1 .0 0 .9 0 .8 0 .7 0 .6 1 - -.. .. , 0 .5 , 0 .4 0 .3 0 .2 0 .1 I' , - L A R G E M O U T H B A S S I ' I \ I \ I \ I \ I \ I \ I \ I \ I \ "'" .-.. ... \ i • • .. ~ , . ... .. \ ,. ," ". .. .. .. . B L A C K C R A P P IE - - A L L S P E C IE S / ! ~ , / ' , / : " ,' " / : ". , , , '- _ _ / l . . . ' / , . , / , .. ' : ... , .: " . : ~ , : .... , . " . " , --- --, £/ : .......... ~ , , ... ... ... ... ... ... . .. , . ' . ' . ' ... .. " . ' . ' . '" 19 65 19 66 19 67 19 68 19 69 19 70 19 71 19 72 19 73 19 74 19 75 19 76 19 77 19 78 Y EA R F ig u re 7. M ea n c a tc h r a te s fo r a ll sp e c ie s, la rg em o u th b as s an d b la c k c ra p p ie d u ri n g A p ri l, M ay an d Ju n e 1 9 6 5 -7 8 , L ak e P o w el l. • N ..,. 1 0 0 90 80 :<: 70 u H ...: 6 0 u ~ 0 H 50 &1 u .,: 40 '" P< 30 20 1 0 • L A R G E M O U T H B A S S o BLA C K C R A P P IE ~ R A IN B O W T R O U T ~ C H A N N E L C A T F IS H . . O T H E R 1 9 6 4 1 9 6 5 1 9 6 6 1 9 6 7 1 9 6 8 1 9 6 9 1 9 7 0 1 9 7 1 1 9 7 2 1 9 7 3 1 9 7 4 1 9 7 5 19 76 1 9 7 7 1 9 7 8 YE AR F ig u re 8 . S p e c ie s c o m p o si ti o n b y p e rc e n t o f th e a v e ra g e L ak e P o w el l a n g le r 's c re e l 1 9 6 4 - 7 8 . N V I REFERENCES CITED Gloss, S., B. E. May, and R. Stone. 1974. Colorado River drainage reservoirs and tailwaters fisheries management investigation and surveys. Annual Prog. Report, Fed. Aid. in Fish Restoration, F-28-R-2. Utah Div. Wildl. Res. Pub. No. 74-11. 10 pp. Gustaveson, A. W., F. M. Stowell, and D. K. Hepworth. (in press). A review of fishing success and pressure on Lake Powell, 1964-1976. Utah Div. Wildl. Res. 33 pp. Hepworth, D. K., A. W. Gustaveson, and R. Biggins. 1976. Lake Powell postimpoundment investigations. Annual Perf. Report, Fed. Aid in Fish Restoration, F-28-R-4. Utah Div. Wildl. Res. Pub. No. 76-21. 37 pp. Hepworth, D. K., A. W. Gustaveson, and F. M. Stowell. 1977. Lake Powell postimpoundment investigations. Annual Perf. Report, Fed. Aid in Fish Restoration, F-28-R-5. Utah Div. Wildl. Res. Pub. No. 77 -1 3. 6 1 pp. Hepworth, D. K., A. W. Gustaveson, F. M. Stowell, and D. L. Archer. 1977. Lake Powell postimpoundment investigations. Annual Perf. Report, Fed. Aid in Fish Restoration, F-28-R-6. Utah Div. Wildl. Res. Pub. No. 78-5. 60 pp. 26 May, B. E., and D. Hepworth. 1976. Lake Powell postimpoundment investigations. Annual Prog. Report, Fed. Aid in Fish Restoration, F-28-R-3. Utah Div. Wildl. Res. Pub. No. 76-3. 42 pp. Rathbun, N. L. Lake Powell February 1, 1970. Glen Canyon Unit-Colorado River storage project, fisheries investigations, creel census studies. 1969-January 31, 1970. Ariz. Game and Fish Dept. 66 pp. Snedecor, G. W., and W. G. Cochran. 1971. Statistical methods. Iowa State Univ. Press, Ames. 593 pp. Stone, J. L. 1965. Glen Canyon Unit-Colorado River storage project, reservoir fisheries investigation, creel census, and plankton studies, July 1, 1964-January 31, 1965. Ariz. Game and Fish Dept. 60 pp. 1966. Glen Canyon Unit-Colorado River storage project, reservoir fisheries investigations, creel census, and plankton studies, February 1, 1965-January 31,1966. Ariz. Game and Fish Dept. 40 pp. 1967. Glen Canyon Unit-Colorado River storage project, reservoir fisheries investigations, creel census, and plankton studies, February 1, 1966-January 31, 1967. Ariz. Game and Fish Dept. 41 pp. 1971. Glen Canyon Unit-Colorado River storage project, Lake Powell fisheries investigations, February 1, 1970-January 31, 1971. Ariz. Game and Fish Dept. 50 pp. 1972. Glen Canyon Unit-Colorado River storage project, Lake Powell fisheries investigations, February 1, 1971-January 31, 1972. Ariz. Game and Fish Dept. 52 pp. Stone, J. L., and N. L. Rathbun. 1968. 27 River storage project, Lake Powell February 1, 1967-January 31, 1968 . Glen Canyon Unit-Colorado fisheries investigations, Ariz. Game and Fish Dept. 56 pp. 1969. Glen Canyon Unit-Colorado River storage project, Lake Powell fisheries investigation, creel census and plankton studies, February 1, 1968-January 31, 1969. Ariz. Game and Fish Dept. 61 pp. Background INDEX TO ANNUAL FISH POPULATION TRENDS Job III Logistical problems usually preclude estimates of absolute numbers of fish in large reservoirs. In such instances, catches from a standardized program of gill netting may provide indices of relative abundance (Moyle 1950; Gooch 1977). A program of annual standardized gill-net sampling has been conducted at Lake Powell since 1971 (Gloss et al. 1974; May and Hepworth 1976; Hepworth et al. 1976, 1977 and 1978) to monitor gross changes in population densities or species composition. In general, past gill-net catches have been dominated by largemouth bass and walleye, with walleye showing an increase in relative numbers since the early 1970's. Since gill nets are selective with respect to size and species of fish (Lagler 1968), a program of electrofishing was initiated in 1977 to obtain information on the segments of the Lake Powell fisheries which were poorly sampled by gill nets; e.g., young-of-the-year game fish. Standardized annual sampling by electrofishing may also provide an indication of future year-class strength and information on recruitment. 29 Methods Gill-net sampling was conducted during March 1978 at Padre Bay, Cha Canyon, Rincon and Red Canyon (Fig. 9). Gangs of ten 30.48 m (100 ft) experimental gill nets (mesh sizes 25, 38, 51 and 76 mm) were fished for three consecutive days at each station. On occasion, only nine nets were used per set due to equipment loss. Nets were set perpendicular to the shoreline in rock and rubble habitat. Fish were removed at 24-hour intervals, measured to the nearest millimeter (TL) and weighed to the nearest 5 g. Scales were taken from selected specimens of all game fish species for future age and growth analysis. The electrofishing boat was a 8.5 m Yukon Delta with fiberglass hull. An Onan 7.5 kw generator provided electrical power for the lighting system and a Coffelt Model RF-10 electroshocker. Five 1.8 m cables which hung from a front-mounted boom served as positive electrodes. The negative electrode consisted of two 4.6 m cables trailing from both sides of the boat. Output voltage of the electro- shocker was 150-200 v dc, which was sequenced to the five positive electrodes so that each electrode was pulsed one time per second . The sampling crew consisted of a driver and one or two netters. Sampling began after dusk and continued for two to six hours. Similar shoreline habitat was electrofished at each station. All captured fish were measured to the nearest millimeter (TL) and released at the station of capture. The time during which the electroshocker was in operation was recorded and a catch rate (fish/hour of electrofishing) was calculated for each species. Largemouth bass less than 175 mm TL and black crappie U t , ~ X A n n u al n e tt in g s it e o E le c tr o fi sh in g s it e I Mi I~ S I o 5 1 0 C an yo n K n o w le s C an yo n F ig u re 9 . L ak e P o w el l sh o w in g e le c tr o fi sh in g a n d an n u al n e tt in g lo c a ti on s . w o 31 less than 125 rnm TL were considered young-of-the-year. Five stations-- Rincon, Hall's Creek Bay, Crappie Cove (Bullfrog Bay) Bass Rock (Bullfrog Bay) and Knowles Canyon (Fig. 9)--were electrofished three nights each. Each station was sampled at approximately one week intervals from mid-August to mid-September. Results Annual netting. A total of 792 fish were captured in 116 nets (Table 7). The highest catch rate occurred at Red Canyon (254 fish or 8.5 fish/net), while the lowest was found at Padre Bay (163 fish or 5.8 fish/net). Walleye and , largemouth bass accounted for over 80% of the total catch. Crappie, channel catfish and carp each comprised about 5% of the total. Although largemouth bass and walleye made up the majority of fish netted at all stations, the catch of these two species varied greatly between individual stations. Only six walleye were netted at Cha Canyon, while 136 bass were taken there. Conversely, at Padre Bay, bass made up only 10% of the catch and walleye accounted for 71%. About a third of the fish netted at Rincon and Red Canyon were bass; walleye made up about one half of the catch at these two stations. Crappie made up from 0.6% (Padre Bay) to 11% (Cha Canyon) of the catch at individual stations. Rainbow trout were netted at Cha Canyon and Padre Bay. Striped bass were also taken in limited numbers at Padre Bay. 32 Table 7. Number and catch rate (in parentheses) of fish caught in gill nets, Lake Powell, March 1978. Catch rates are in fish per net. Percent Padre Cha Red of Species Bay Canyon Rincon Canyon Total Catch Largemouth bass 15 136 67 85 303 38.7 (0.5) (4.9) (2.2) (2.8) (2.6) Walleye 109 6 93 122 330 42. 1 <3.9 ) (0.2 ) <3.1) (4.1) (2.8 ) Black crappie 1 21 5 11 38 4.9 ( tal (0.8) (0.2) (0.4) (0.3) Bluegill 0 3 1 1 5 0.6 (0.0) (0. 1) t) t) t) Green sunfish 1 1 1 9 12 1.5 ( t ) t ) t ) (0.3) (0. 1 ) Channel catfish 7 7 13 7 34 4.3 (0.3) (0.3) (0.4) (0.2) (0.3) Carp 13 10 3 13 39 5.0 (0.5) (0.4) (0. 1) (0.4) (0.3) Flannelmouth sucker 1 0 0 2 3 0.4 t ) (0.0) (0.0) t ) t ) Rainbow trout 6 7 0 0 13 1.7 (0.2) (0.3) (0.0) (0.0) (0. 1) Brown trout 1 0 0 0 1 0.1 t ) (0.0) (0.0) (0.0) (0.0) Striped bass 9 0 0 0 9 1.1 (0.3) (0.0) (0.0) (0.0) t ) Yellow bullhead 0 1 0 4 5 0.6 (0.0) ( t ) (0.0) (0. 1) t ) Total 163 192 183 254 792 (5.8) (6.9) (6. 1) (8.5) (6.8) at = Less than 0.1 fish per net. 33 Electrofishing. A total of 1,829 fish were captured in 15 nights of electrofishing (11.5 hours actual shocking time) for an overall catch rate of 159 fish / hr. Green sunfish and young-of-the-year largemouth bass were captured most often, making up 40 and 34% of the total sample, respectively (Table 8). The highest catch rates for both y-o-y bass and y-o-y crappie • occurred at Crappie Cove in Bullfrog Bay. The lowest catch rates for both of these groups occurred at Knowles Canyon--green sunfish and bluegill making up the majority of the sample there. Relatively high catch rates for y-o-y bass and y-o-y crappie were recorded for Hall's Creek Bay (bass = 61 fish/hr; crappie = 21 fish/hr) and Bass Rock in Bullfrog Bay (bass = 58 fish/hr; crappie = 29 fish/hr). The catch rate of y-o-y bass at Rincon was intermediate (49 fish/hr) while the catch rate for y-o-y crappie was relatively low there (7 fish/hr). Several juvenile and adult bass were also captured during electrofishing at Hall's Creek Bay and at Bass Rock. Discussion Annual netting. The 1978 annual netting catch rates for bass and walleye both showed an increase over the 1977 rates (Fig. 10 and Table 9). This increase was evident at all sample stations. The species composition of the catch was similar to that of past years and demonstrated the same trends--bass and- walleye making up the majority of the catch and walleye continuing to show an increase in numbers. There T ab le 8 . N um be r an d m ea n c a tc h ra te (i n p a re n th e se s) o f fi sh c a u g h t b y e le c tr o fi s h in g , L ak e P o w e ll , A u g u st -S ep te m b er 1 9 7 8 . C at ch ra te s a re fi s h p e r h o u r o f e le c tr o fi s h in g . = H a ll 's C re ek R in co n B ay B as s R oc k Y o u n g -o f- th e -y e a r la rg e m o u th b a ss 11 8 (4 9 .3 ) 18 2 (6 1 .2 ) 15 9 (5 8 .4 ) A ge 1 an d o ld e r la rg e m o u th b a ss 5 (1 .7 ) 17 (6 .2 ) Y o u n g -o f- th e -y e a r b la c k ? ra p p ie 17 (6 .6 ) 66 (2 1 . 0 ) 7 9 (2 9 .4 ) G re en su n fi sh 92 < 3 7 .8 ) 26 1 (8 6 .8 ) 16 0 (5 9 .6 ) B lu e g il l 2 2 (9 .2 ) 43 (1 4 .7 ) 5 0 (1 8 .6 ) C h an n el c a tf is h 11 < 3 .8 ) 4 (1 .5 ) R ed sh in e r 5 (1 .6 ) (0 .4 ) Y el lo w b u ll h e a d 6 (2 .6 ) (0 .3 ) (0 .4 ) A ll sp e c ie s 25 5 (1 1 1 . 7 )a 5 7 4 (1 8 6 .2 ) 47 1 (1 3 8 .3 ) a T o ta l fi s h d iv id e d by t o ta l h o u rs o f e le c tr o fi s h in g . C ra p p ie K n o w le s C ov e C an yo n 91 (8 0 . 1 ) 7 9 < 3 5 .5 ) 42 < 3 6 .3 ) 10 (4 .7 ) 32 (2 8 .1 ) 17 8 (7 7 .9 ) 15 (1 3 .8 ) 7 5 < 3 1 .9 ) 2 (1 .9 ) 5 (1 .8 ) 18 2 (1 4 5 .4 ) 3 4 7 (1 5 0 .9 ) T o ta l 6 2 9 (5 4 .5 )a 22 (1 . 9 ) 2 1 4 (1 8 .6 ) 7 2 3 (6 2 .7 ) 2 0 5 (1 7 .8 ) 17 (1 .5 ) 11 (1 . 0 ) 8 (4 .0 ) 1 ,8 2 9 (1 5 8 .6 ) ~ o f T o ta l w ..,. C at ch 3 4 .4 1 .2 1 1 . 7 3 9 .5 1 1 . 2 0 .9 0 .6 0 .4 6 - - - B A S S • . . • .. • . . • .. W A L L E Y E 5 4 3 2 -. .... ... . ..... ..... .... 'V 7 . ' '. . .. ' '. " "' " .' . . . . .. ' '" .. ' . . . . .. .. .. ..' '. .' , . ' . . .. ' '. .... ' .. ' . '. ..' ., .... ... . 1 19 71 19 72 19 73 19 74 19 75 19 76 19 77 19 78 F ig u re 1 0 . C at ch ra te s (f is h /n e t) o f la rg em o u th b a ss a n d w al le y e fr om an n u al n e tt in g 1 9 7 1 -7 8 , L ak e P o w el l. Co > '" T ab le 9 . C at ch ra te an d th e p er ce n ta g e o f th e c a tc h b y sp e c ie s an d y e a r, an n u al g il l n e tt in g , L ak e P o w el l, 19 11 -1 9 1 8 . 19 11 19 12 19 13 19 14 19 15 19 16 19 11 19 18 C at ch ~ o f C at ch ~ o f C at ch ~ o f C at ch ~ o f C at ch ~ o f C at ch ~ o f C at ch % o f C at ch ~ o f S pe c ie s R at e C at ch R at e C at ch R at e C at ch R at e C at ch R at e C at ch R at e C at ch R at e C at ch R at e C at er L ar ge m ou th b as s 1 .6 5 4 1 .3 5 .8 2 5 1 .4 2 .1 1 6 2 .3 4. 01 6 3 .4 4 .4 9 5 6 .1 2 .1 2 4 3 .9 1 .8 5 4 2 .1 2 .6 1 3 8 .3 W al le ye 0 .2 9 1 .1 1 .1 2 1 1 .0 0 .4 1 9 .4 1 .0 9 1 1 .3 2 .1 5 2 6 .8 2 .1 1 3 4 .1 1 .1 1 2 6 .6 2 .8 4 4 1 .1 B la ck c ra p p ie 0 .1 2 3 .1 0 .6 1 6 .6 0 .1 2 6 .1 0 .2 1 4 .2 0 .3 6 4 .5 0 .2 1 4 .3 0 .2 6 5 .8 0 .3 3 4 .8 B lu e g il l 0 . 1 2 3 . 1 0 . 5 2 5 . 1 0 '. 0 6 1 . 3 0 . 0 5 0 . 8 0 . 0 4 0 . 5 0 .1 0 1 .6 0 .0 9 2 . 1 0 . 0 4 0 . 6 G re en su n fi sh 0 .1 0 2 .5 0 .1 6 1 .6 0 .0 9 2 .1 0 .1 3 2 .0 0 .0 6 0 .1 0 .0 4 0 .1 0 .0 9 2 .1 0 .1 0 1 .5 C ha nn el c a tf is h 0 .1 2 3 .1 0 .4 3 4 .2 0 .2 1 4 .6 0 .1 4 2 .3 0 .2 5 3 .1 0 .1 6 2 .6 0 .2 0 4 .5 0 .2 9 4 .3 C ar p 1 .1 4 2 8 .6 0 .1 9 1 .8 0 .3 2 1 .3 0 .3 4 5 .4 0 .3 6 4 .4 0 .3 8 6 .2 0 .4 4 1 0 .1 0 .3 4 4 .9 F la n n el m o u th su ck er 0 .1 8 4 .6 0 .2 8 2 .1 0 .2 1 2 .5 0 .1 1 2 .6 0 .0 8 0 .9 0 .0 8 1 .3 0 .0 3 0 .8 0 .0 3 0 .4 R ai nb ow tr o u t 0 . 2 4 6 . 1 0 . 3 1 3 . 0 0 . 1 0 2 . 2 0 . 0 8 1 . 2 0 . 1 9 2 . 4 0 .2 5 4 .0 0 .2 6 6 . 0 0 . 1 1 1 . 6 B ro w n tr o u t 0 .0 2 0 .5 0 .0 0 0 .0 0 .0 1 0 .2 0 .0 3 0 .5 0 .0 4 0 .5 0 .0 4 0 .1 0 .0 2 0 .4 0. 01 0 .1 S tr ip e d b as s 0 .0 0 0 .0 0 .0 0 0 .0 0 .0 0 0 .0 0 .0 0 0 .0 0 .0 0 0 .0 0 .0 0 0 .0 0 .0 2 0 .4 0 .0 8 1 .1 Y el lo w b u ll h ea d 0 .0 0 0 .0 0 .0 0 0 .0 0 .0 0 0 .0 0 .0 0 0 .0 0 .0 0 0 .0 0 .0 0 0 .0 0 .0 1 0 .2 0 .0 4 0 .6 A ll S p ec ie s 3 .9 8 10 . 10 4 .2 4 6 .3 1 8 .0 2 6 . 15 4 .4 4 6 .8 2 '" a- 37 was a statistically significant correlation (5% level) between the catc h rate for walleye and the time since the annual netting program began. according to Spearman's rank correlation coefficient (Snedecor and Cochran 1971 ) . Although the catch rate for wal leye has been increasing and exceeded that of bass for the first time in 1978. there was no indication that the expanding walleye population has adversely affected populations of largemouth bass or any other species. Bass gill-net catch rates have remained relatively stable and Spearman's rank correlation coefficient showed no statistically significant correlations between the catch rate of bass and reservoir age or walleye catch rates. Differences in the composition of the catch between stations were again evident in 1978. As in past years. few bass were caught at Padre Bay while walleye were relatively abundant there. The opposite continued to hold true for Cha Canyon in 1978. where bass were abundant and walleye scarce. The highest overall catch rate again occurred at Red Canyon in 1978. Species other than bass and walleye were relatively rare in the gillnet catches and exhibited no obvious changes in relative abundance. Electrofishing. The 1978 electrofishing catch rates for y-o-y bass were higher at all stations than those recorded in 1977 (Table 10 ) . Young-of-the-year crappie were also caught at a higher range in 1978 at all stations except Knowles Canyon. This suggests that there was a relatively stronger year class of both bass and crappie in 1978. Observations during other sampling and reports from anglers support such a hypothesis. 38 Table 10. Young-of-the-year bass and crappie per hour of electro- fishing for August-September 1977 and 1978, Lake Powell. Location Y-O-Y Bass Y-O-Y Crappie 1977 1978 1977 1978 Rincon 4.8 49.3 1.5 6.6 Hall's Bay 22.5 61. 2 13.7 21.0 Bass Rock 58.4 29.4 Crappie Cove 36.3 80. 1 6.4 36.3 Knowles Canyon 6.9 35.5 8.2 4.7 Factors other than relative abundance may influence the catch rates obtained by electro fishing and gill netting. Some of these include fish behavior, shape and structure of fish, weather conditions during sampling and operator skill and experience. Although concerted effort has been made to keep sampling variability to a minimum by standardizing sampl ing stations, sampl ing dates and technique, some uncontrolled variables will inevitably remain. The use of two different gears (electroshocker and gill nets) should provide a fuller and more accurate picture of any population changes. Additionally, electrofishing provides a means of following population dynamics of bass and crappie prior to the time that they become vulnerable to other types of gear or to the angl er • Recommendations 1. Continue standardized sampl ing of fish populations by electrofishing and gill netting. 2. Test the feasibility of other methods (beach seining, transect counts of fish using SCUBA gear ) for sampling segments of the fishery still inadequately sampled, particularly adult crappie. 3. Design a gill-net study of seasonal, special and length-frequency distribution of walleye in Lake Powell. Current test netting reflects walleye distribution only during the spawning period. REFERENCES CITED Gloss, S., B. E. May, and R. Stone. 1974. Colorado River drainage reservoirs and tailwaters fisheries management investigation and surveys. Annual Prog Report, Fed. Aid. in Fish Restoration, F-28-R-2. Utah Div. Wildl Res. Pub. No. 74-11. 10 pp. Gooch, B. 1977. The statistical analysis of gill net catches. Info. Sys. Div. Mont. Dep. Admin., Helena. 65 pp. He pworth, D. K., A. W. Gustaveson, and R. Biggins. 1976. Lake Powell postimpoundment investigations. Annual Perf. Report, Fed. Aid in Fish Restoration, F-28-R-4. Utah Div. Wildl. Res. Pub. No. 76-21. 37 pp. Hepworth, D. K., A. W. Gustaveson, and F. M. Stowell. 1977. Lake Powell post impoundment investigations, Annual Perf. Report. Fed. Aid in Fish Restoration, R-28-R-5. Utah Div. Wildl. Res. Pub. No . 77 -13. 61 pp. Hepworth, D. K., A. W. Gustaveson, F. M. Stowell, and D. L. Archer. 1977. Lake Powell postimpoundment investigations. Annual Perf. Report, Fed. Aid in Fish Restoration, F-28-R-6. Utah Div. Wildl. Res. Pub. No. 78-5. 60 pp. Lagler, K. F. Pages 7-44 prod uction 1971. Capture, sampling and examination of fishes. in W. E. Ricker, ed. Methods for assessment of fish in fresh waters. ISP Handbook 3, Blackwell, London. 39 May, B. E., and D. Hepworth. 1976. Lake Powell postimpoundment investigations. Annual Prog. Report. Fed. Aid in Fish Restoration, F-28-R-3. Utah Div. Wildl. Res. Pub . No. 76-3. 42 pp. Moyle, J. B. 1950. Gill nets for sampling fish populations in Minnesota waters. Trans. Am. Fish. Soc. (1949); 195-204. Snedecor, G. W., and W. G. Cochran. 1971. Statistical methods. Iowa State Univ. Press, Ames. 593 pp. Background STRIPED BASS CULTURE Job IV An experimental culture station for striped bass rearing research was constructed near Glen Canyon City, Utah and completed in 1973. Striped bass production began in 1974 and has been conducted annually. Objectives of the culture studies are to evaluate variables affecting survival and growth of pond-cultured striped bass and develop techniques for rearing larval striped bass to finglering size. Completed work has included studies on plankton responses to organic and inorganic fertilization, evaluation of stocking densities, food habit studies, timing of fry introductions in relation to water temperature and food availability, and time of pond filling and fertilization in relation to fry arrival from donor agencies (Hepworth et al. 1978, 1977 and 1976; May and Hepworth 1976; Gloss et al. 1974). Primary objectives for 1978 were (1) to evaluate optimum age for release of fry from tempering baskets; and (2) to evaluate aquatic weed control using potassium permanganate as a shading agent. 41 Methods Fertilization and filling of ponds were scheduled around planned fry arrival. Previous results indicated that spring weather conditions and water temperatures at the culture facility were best suited for fry survival and growth during May. Fry are generally available from California Fish and Game at this time and have been received in the past around 20 May. Fry arrival was scheduled for 20 May 1978 and pond preparation was geared for that date. All ponds were fertilized at the rate of 2,679 kg/ha (3,000 lbs/acre) with alfalfa hay (Table 11). Pond filling began 29 April 1978, 21 days before expected fry arrival. During this preparation period" the ponds were monitored for oxygen and plankton development. Oxygen was sampled daily until saturation was reached. Plankton samples were taken every four days to identify types and sizes of plankton blooms. Ponds that were slow to develop an adequate bloom were administered supplemental doses of 20-20-20 inorganic fertilizer to stimulate plankton growth. On 23 May 1978, shipment of 1.25 million fry was received from California. Ponds were stocked at an estimated rate of 308,625 fry per hectare (125,OOO/acre). Fry were tempered and stocked after dark into seran cloth baskets for observation. Ponds similar in plankton abundance and development were treated differently as to time of release to determine which age at time of release was more conducive to fry survival. Fry in Ponds 1, 2, and 5 were released from the baskets at seven days of age, while fry in Ponds 3, 4, and 6 were released at 12 days of age. A small number of fish were retained in baskets in each '" 42 pond for observation and sanpling . Fish were sanpled at four-day intervals for food habit determinations from age nine days to age 31 days. Sanple fish were taken from the basket and also from the pond when possible. Fuel oil treatments for aquatic insect control were made before fry arrival, before fry release from tempering baskets, when insects were observed to be increasing and prior to harvest. Ponds were treated at 46.75 l/ha (5 gal/acre) with a mixture of diesel fuel, gasoline and motor oil as described by Harper (1977). Table 11. Fertilization rates of culture ponds, 1978. Ponds of Hay Pounds of Hay Pounds of Initially Applied Ad ded as Suppl e- Inorganic Pond at 3,000 Ibs/acre mental Fertilizer Fertilizer 1,200 200 10 2 1,200 200 5 3 3,000 600 25 4 3,300 400 10 5 9,300 500 25 6 11 ,700 950 25 The use of potassium permanganate as a shading agent to retard aquatic weed growth was evaluated by treating Ponds 1 and 3 with a 3 ppm concentration on 12 June 1978. The dry chemical was placed in burlap bags and disseminated by towing the bag around the pond. Ponds 2 and 4 were treated with 1.5 ppm potassium permanganate on 22 June 1978 followed by a similar dose on 26 June. On 1 July 1978, Pond 1 was treated with 4 ppm and Pond 3 was treated with 6 ppm. 43 Supplemental feeding was attemped in Ponds 4 and 5. Feeding was begun when fish were 28 days old and 15-20 mm long. Initial feeding rate was 4.5 kg/ha/day (5 lbs/acre) using an equal mixture of ground beef liver and Silver Cup salmon starter. The liver mixture was fed for the first two days and then Silver Cup was fed for the remainder of the time. The amount of Silver Cup was increased to 8.9 kg/ha/day (10 lbs/ acre) when fish were 33 days of age. Supplemental feeding began in Pond 2 on 27 June 1978, when plankton counts indicated food supplies were critically low. Fish were started feeding on Silver Cup alone and fed 8.9 kg/ha/day (10 lbs/acre). Results Finglering production reached a record high of 254,290 striped bass (Table 12). The 3.28 ha (8 acre) facility produced an average of 78.383 fingerlings per hectare (31,747/acre). Of the estimated 1,200,000 fry stocked 21% survived, overshadowing the previous high survival rate of 14% achieved in 1977. Production success was attributed to timing of fry introductions to coincide with the beginning of the nauplii cope pod plankton bloom. Successful ponds were characterized by fry introduction before the copepod count reached 100 per liter (Figure 11). The nauplii copepod count in unsuccessful ponds exceeded 100 per liter before fry introduction. Oxygen depletions due to pond fertilization were overcome 11-16 days after filling began. Nauplii copepod abundance reached 100 per liter 23-35 days after filling. 44 Table 12. Production of fingerling striped bass, 1978. Estimated Sur face Number Percent Production Total Pond Acres Stocked Survival per Acre Harvested 0.46 100,000 0.20 441. 30 203 2 0.43 50,000 57.0 65,930.23 28,350 3 0.95 175,000 0.02 38.95 37 4 0.73 150,000 46.0 93,835.62 68,500 5 2.60 300,000 42.0 48,692.31 126,600 6 2.84 425,000 7.0 10,774.65 30,600 Total 8.01 1,200,000 21.0 31,746.57 254,290 Fry released from tempering baskets at seven days of age had an average production of 94,696 per hectare <38,354/acrel compared to 86,126 per hectare (34,883/acrel for fry released at 12 days of age. Fish retained in tempering baskets for food habits and growth studies were found to be slow-growing and in poor condition compared to fish collected directly from the same pond. Air breathing hemipterans were effectively eliminated in Ponds 1-4 by fuel oil treatments. The larger size of Ponds 5 and 6 made it impossible to cover the entire pond with an oil film; therefore, insect control was less effective. Aquatic insects were not a problem this year with the exception of gill-breathing Odonata larvae which were unaffected by the fuel oil treatment. 2000 1000 1000 500 1000 500 , FRY STOCKED !~ ! [441J , . i Production / Acre i~ ! 1\ Pond 1 , i I May June July Pond 3 [39J May I June July i i I , May Pond 5 [48,692J I I I I i ! ! , I i , , May_ i I I May 1 2976 TT [65,930J Pond 2 June July Pond 4 [93,836J June July Pond 6 [10,775J July Figure 11 . Timing of f r y introduct ion in re l a tion t o s t age of na uplii copepod abundance. Pr oduc t ion of f inger lin gs pe r acre lis t ed fo r each pond . 45 46 Treatment with potassium permanganate at 3 ppm concentration produced and maintained a secchi disk measurement of 0.92-1.37 m (3-4.5 ft) for a 10-day period. Treatment at 1.5 ppm followed by a subsequent treatment of 1.5 ppm produced a reading of 1.22-1.83 m (4-6 ft) initially and then showed no change as a result of the second treatment. Treatments of 4-6 ppm had a negative shading effect since phytoplankton was apparently eliminated by the heavy concentration of potassium permanganate. Secchi disk readings increased from 1.22 m (4 ft) to 1.68 m (5.5 ft) in Pond and to 1.98 m (6.5 ft) in Pond 3 following treatment. Lowest secchi disk readings (2-2.5 ft) were obtained in Pond 5 which was untreated. Dense weed growth occurred in all ponds since light was not sufficiently reduced to retard weed growth. Supplemental feeding was begun 16 June 1978 in Ponds 4 and 5. Fish in Pond 4 were immediately attracted to ground liver and salmon starter and were actively feeding by 19 June 1978. Fish in Pond 5 were never observed feeding and supplemental feeding was curtailed on 21 June 1978. Supplemental feeding began 27 June 1978 in Pond 2 when plankton counts indicated food supplies were critically low. Although fish were started without ground liver, they began feeding immediately on salmon starter . Discussion Previous experimentation indicated that timing the fry introduction to precede the bloom of nauplii cope pods was the key to successful fingerling production (Hepworth. et al. 1978). Using the filling and fertilization techniques that were proven most successful last year, we 47 achieved excellent success in four of the six ponds. The two unsuccessful ponds bloomed more quickly than the others even though all ponds were treated similarly (Figure 11). These results further substantiate the premise that timing is the key to production success. Experimentation on optimum age of release from tempering baskets was inconclusive. Production per hectare was slightly higher on fish released at seven days compared to fish released at 12 days, although there was no statistical significance. Field observations, however, suggest releasing fish at the earlier age. A significant mortality occurred on the 11th day of holding in Pond 6 when healthy fish were trapped in dislodged patches of filamentous algae. Mortality of this nature would have less chance of occurring if holding time was reduced to the shortest possible time. Future fry releases will occur near six days of age. This will allow enough time to ensure that the fry have successfully acclimated to the pond environment without exposing them to unnecessary risks due to confinement. Fry food habit studies indicated a selective preference for copepods and cladocerans while rotifers and ostracods were avoided. Food was first observed in stomachs of fry at 10-13 days of age (5-7 mm). There was some indication that rotifers were taken during the critical period when feeding began, but nauplii copepods were the preferred diet. Fry began eating adult copepods and cladocerans when they attained lengths of 10 mm. Comparison of stomachs from fish taken from the sample baskets and those taken directly from the pond indicated that fish confined in the baskets were forced to eat available food items 48 (ostracods and rotifers) rather than selecting preferred items. Growth and condition of fish held in tempering baskets were poorer than fish sampled from the pond. Future studies of fish held in tempering baskets would require daily cleaning of the mesh baskets to ensure adequate water and plankton exchange. The control of aquatic weeds by shading the pond with potassium permanganate proved ineffective. Application of 3 ppm produced a secchi disk reading of about 1 m for a 10-day period. This light reduction did not sufficiently retard weed growth. A reading of 0.46 m (18 in) or less is required for effective weed control (Harper 1977). Weed control has become the biggest challenge at the culture facility. Success of harvest depends on the absence of weed growth in the seining areas. Heavy weed growth hinders the harvest and causes serious losses of fingerlings that could otherwise be stocked into Lake Powell. Future studies will concentrate on methods of eliminating noxious weed growth by chemical and mechanical control. Supplemental feeding was found to be of value in ponds where plankton production could not keep pace with striped bass predation. When plankton numbers were high, fry would not eat Silver Cup feed. r feel that the health and condition of the fish were maintained by supplemental feeding in Ponds 2 and 4. Recommendations 1. Replicate the successful technique of filling and fertilizing the ponds approximately 20 days prior to planned fry arrival. 49 2. Apply a preemergent herbicide to the dry pond bottans of selected ponds to evaluate the utility of this method of aquatic weed control. 3. Release fry from tempering baskets at 6-7 days of age. 4. Evaluate other methods of aquatic weed control to include: potassium permanganate shading, lining the seining areas with plastic sheets and experimenting with herbicide treatments. 5. Drain and refill those ponds that bloom prior to fry arrival. REFERENCES CITED Gloss, S., B. May, and R. Stone. 1974. Pond rearing of striped bass. Completion Report, Fed. Aid in Fish Restoration, F-29-R. Utah Div. Wildl. Res. Pub. No. 74-11. 12 pp. Harper, J. L. 1977. Culture of striped bass. Final Report, Fed. Aid in Fish Restoration, F-25-R. Okla. Dept. Wildl. Conserv. 65 pp. Hepworth, D. K., A. W. Gustaveson, and F. M. Stowell. 1978. Lake Powell postimpoundment investigations. Annual Perf. Report, Fed. Aid in Fish Restoration, F-28-R-6. Utah Div. Wildl. Res. 60 pp. 1977. Lake Powell postimpoundment investigations. Annual Perf. Report, Fed. Aid in Fish Restoration, F-28-R-5. Utah Div. Wildl. Res. Pub. No. 77-13. 60 pp. Hepworth, D. K., A. W. Gustaveson, and R. Biggins. 1976. Lake Powell postimpoundment investigations. Annual Perf. Report, Fed. Aid in Fish Restoration, F-28-R-4. Utah Div. Wildl. Res. Pub. No. 76-21. 37 pp. May, B., and D. Hepworth. 1976. Lake Powell postimpoundment investigations. Annual Perf. Report, Fed. Aid in Fish Restoration, F-28-R-3. Utah Div. Wildl. Res. Pub. No. 76-3. 42 pp. Background EVALUATION OF STRIPED BASS INTRODUCTION J~ V Striped bass have been stocked annually into Lake Powell since 1974 with approximately 80% of the fingerling stripers stocked in Wahweap Bay. Bullfrog Bay has been stocked annually since 1976. Sampling of the striped bass pcpulation was designed to supply information on survival, growth and food habits. Data on distribution and development of a sport fishery were largely collected as part of the regular creel census program (Job II). The striped bass have continued to show excellent growth and high utilization of threadfin shad in their diet. Most of the returns to the creel have been incidental although a small group of anglers are successfully fishing for striped bass in the southern end of the reservoir. Methods Collections of striped bass from Lake Powell were largely made by gill netting. A few young-of-the-year striped bass were caught with beach seines. Creel census returns and angler repcrts were used to describe distribution and movement from the original stocking areas. 51 Lengths, weights, stomachs and scales were collected from all striped bass. Stomach contents were preserved in 10% formalin for later examination . Stomachs were examined to determine composition of food items by number, volume and occurrence. Scales were taken from below the lateral line and posterior to the pectoral fin. Impressions of the scales were made on acetate cards with a heated press. They were read and measured with the aid of a microprojector. Scale characteristics were compared to growth of introduced known age striped bass. Striped bass stocking procedures and times are covered under Job IV. Results A total of 254,290 striped bass fingerlings were stocked in Lake Powell in 1978. Wahweap Bay received 169,469 and 84,821 were planted in Bullfrog Bay (Tab le 13). A total of 592,763 striped bass have been planted in Lake Powell since 1974. Catches with both beach seines and small mesh gill nets indicated good survival of the fingerlings stocked in Wahweap Bay. An average of four young-of-the-year stripers were collected per seine haul in Wahweap Bay. Sampling success was poor at Bullfrog for the second year. It is not known whether the lack of success in the Bullfrog area is the result of poor survival, migration, gear and site selectivity or a combinati0n of all three. The average growth of each age class is illustrated in Table 14. Mean total lengths at ages 1-4 were 261, 442, 566 and 676 mm, respectively. 52 Table 13. Stocking record of striped bass introduced into Lake Powell. Number Stocked Year Wahweap Bullfrog Total 1974 49,885 0 49,885 1975 94,878 0 94,878 1976 35,752 19 , 305 55,057 1977 86,003 52,650 138,653 1978 169 , 469 84,821 254,290 Total 435,987 156,776 592,763 Threadfin shad dominated the diet of 272 striped bass examined during 1977 and 1978 . Shad comprised 71-100% of the diet by number and 82-100% by volume (Table 15). The lowest numbers and volumes of thread fin shad were observed in the summer and the highest in the winter . Crayfish were the second most abundant organism in striped bass stomachs followed by unidentified fishes and centrarchids, respectively. Discussion Growth of Lake Powell striped bass was better than most other reported populations (Table 14). The mean total lengths at ages 1-4 were 261, 442, 566 and 676 mm , respectively. Growth rates of both sexes have been combined to date . Edwards (1974) and Robinson (1960) found that males and females grow at the same rate through age
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