title
Lake Powell fisheries investigations : 1988 (segment 4) annual report, Dingell-Johnson Project F-46-R-4
author
Array ( [0] => Gustaveson, A. Wayne [1] => Bonebrake, Bruce L. [2] => Christopherson, Kevin )
abstract
UDWR Publication Number 89-12
date
1989-01-01
organization
Utah. Division of Wildlife Resources
species
Array ( [0] => Not Specified )
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https://grey-lit.s3.wasabisys.com/lake-powell-fisheries-investigations-1988-segment-4-annual-report-dingell-johnson-project-f-46-r-4.pdf
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Lake Powell Fisheries Investigations 1988 (Segment 4) Annual Report Dingell-Johnson Project F -46-R-4 P",blieo..+""h N ",mbex" 'l'1 - I.:L 1P.1UIAH ~~ NAIUAAl A{SOUACES .,........ wnowe QelOUfc., LAKE POWELL FISHERIES INVESTIGATIONS 1988 Performance Report A. Wayne Gustaveson, Project Leader Bruce L. Bonebrake, Project Biologist Kevin Christopherson, Special Projects Biologist, SRO Dingell-Johnson Project F- 46-R-4 May 1, 1988 - April 30, 1989 May 1989 Utah Department of Natural Resources Division of Wildlife Resources 1596 West North Temple Salt Lake City, UT 84116 Tim Provan Director An Equal Opportunity Employer TABLE OF CONTENTS LIST OF TABLES . LIST OF FIGURES ABSTRACT . JOB NUMBER I. II. III. IV. V. FORAGE CONDITION STUDY MEASUREMENT OF FISHERY HARVEST, PRESSURE AND SUCCESS INDEX TO ANNUAL FISH POPULATION TRENDS Annual netting E1ectrofishing STRIPED BASS POPULATION DEVELOPMENT SMALLMOUTH BASS POPULATION DEVELOPMENT 1988 SMALLMOUTH BASS CULTURE SUMMARY REFERENCES CITED • • - iii- v vii ix 1 9 15 15 21 25 29 33 35 LIST OF TABLES Tables 1. 2. 3. 4. 5. 6. 7. 8. 9. Mean number of larval threadfin shad collected per ichthyoplankton net tow, Navajo Canyon, Lake Powell 1984-1988 . • . • • • • • . . . . . • • . • • • • . Mean number of larval thread fin shad collected per ichthyoplankton net tow, San Juan River, Lake Powell 1987-1988. Species composition (percent) of total angler harvest at Lake Powell by anglers at five access April through October, 1988 Sport fisheries creel rates (fish/angler hr) by species and access area, Lake Powell, April-October 1988 Catch rate, including fish released, by species, Lake Powell, April-October 1988 • . • • • . • •. •• • • Species sought by anglers (percent) at Lake Powell, April-October 1988 . • • • • • • • Anglers residence listed by access area, Lake Powell, April- October 1988 • • • • • • . • • • Catch rates (fish/net day) during annual gillnetting, Lake Powell, March 1988 •••..• • •••••• Percent occurrence of food items in fish stomachs collected in gill nets, Lake Powell, March 1988. (Percentages based only on number of stomachs containing food.) •.••••• 10. Mean catch rate (fish/hr) of fish collected by electrofishing, Lake Powell, September 1988 11. Mean total length (mm) measured by subsampling young of year 6 6 12 12 13 14 14 16 19 22 fish collected by electrofishing, Lake Powell, September 1988 23 12. Percent occurrence of food items in striped bass stomachs collected during summer creel census and fall gill netting, Lake Powell, 1988. (Percentage based only on number of stomachs containing food.). . • • • . • • • • . . • • • . 23 13. Smallmouth bass stocking history, Lake Powell, 1982-1988 31 14 . Mean catch rate (fish/hour) of young-of-the-year smallmouth bass collected by electrofishing, Lake Powell, 1982-88 32 15. Smallmouth bass production at the Wahweap Warmwater Hatchery, 1988 •••••••.••• • . . . • . • • • . . 34 -v- LIST OF FIGURES Figures 1. 2. 3. 4. Map of Lake Powell showing trawling and ichthyoplankton netting stations for threadfin shad . ". .. ..•...• •••• Mean number of larval shad collected per ichthyoplankton net tow, lower Lake Powell, 1987-1988 •.•••••••••••• Mean number of larval shad collected per ichthyoplankton net tow, mid Lake Powell, 1987-1988 •••. Mean number of threadfin shad collected per trawl tow, July-September, Lake Powell, 1977-1988 5. Indices of total recreational boat use and angling pressure, Lake 3 4 5 7 Powell, 1965-1988 • • •. •••••••••••• 11 6. Catch rate (fish/net-day) for walleye annual netting, Lake Powell, 1971-1988 •.•• • • • • • • • • • • • • 17 7. Catch rate (fish/net-day) for Largemouth Bass annual netting Lake Powell, 1971-1988 • • • • • • •• •••••. 18 8. 9. Average number of striped on Lake Powell, expressed set, 1981-1988 •••• bass caught during fall gill netting as fish caught/lOOO ft 2 of net/12 hr Average condition factor (Kfl) of adult and juvenile striped bass at Lake Powell, 1975-1988 ••••••••• -vii- 27 28 ABSTRACT For the fourth consecutive year threadfin shad, Lake Powell's only pelagic forage species, produced a very small year class. Reproduction was quite low and there was virtually no recruitment of young- of-the-year (yoy) shad into the pelagic zone of Lake Powell. Poor forage conditions caused the striped bass population to decrease in mean total length for the fourth consecutive year. Sport fish were caught at an average rate of 0.41 fish per hour with the majority of these fish being striped bass. Fishing pressure decreased from previous surveys. Relative abundance of sport fish sampled by trend gill netting was the lowest reported since sampling began. Production of yoy sport fi sh was low for all species except smallmouth bass, whose population continued to expand. A total of 71,000 fingerling smallmouth bass was produced at the Wahweap Warmwater Hatchery. All of these fish were stocked at five locations in Lake Powell. Smallmouth bass yoy grew at rates similar to largemouth bass yoy. - ix- FORAGE CONDITION STUDY JOB I METHODS Threadfin shad (Dorosoma petenense) spawning was monitored with ichthyoplankton net collections, which began in May and continued until October. Weekly samples were taken in the backs of bays at Wahweap Creek, Warm Creek, Bullfrog Creek and Halls Creek. Biweekly samples were collected at Piute Farms Wash, Piute Farms Red Wall, the San Juan River inflow and Navajo Canyon (Figure 1) . Recruitment of young-of-the-year (yoy) thread fin shad into the pelagic areas of Lake Powell was monitored by monthly midwater trawl collections and eight-minute sonar transects. Sampling was conducted from July through September at Wahweap, Bullfrog and Good Hope bays (Figure 1). A complete description of both the ichthyoplankton and trawling sampling methods can be found in Gustaveson et al. 1985. RESULTS AND DISCUSSION Ichthyoplankton netting began in May and continued until October, when shad spawning ended. At the lower lake stations spawning was quite similar to 1987. Wahweap Creek showed a slight increase in spawning production over 1987. Shad spawning peaked at the same level in Warm Creek but the peak came in June 1988 compared to the previous year's peak in May (Figure 2). Mid- lake stations also experienced a similar spawn of shad over the last two years with a little improvement at the Bullfrog station in 1988 (Figure 3). Shad spawning in Navajo Canyon showed two peaks during 1988, one in May and one in July (Table 1). Shad spawning in the San Juan River arm peaked in June but at lower levels than 1987 at Piute Red Wall. No definite peak was noted at Piute Farms Wash in 1988. A new marina was constructed at Piute Farms Wash during 1987 but it is unlikely that marina activity was responsible for the decrease in spawning activity. A few shad larvae were collected from the San Juan River, mostly in Augus t samples, indicating that at least some shad used the inflow for spawning in 1988 (Table 2). Midwater trawl catches of yoy shad during 1988 were among the lowest observed since trawling began at Lake Powell eleven years ago (Figure 4). Echograms made during each sample period also reflected the lack of shad in the open water zone. Although it was anticipated that a peak in the pelagic population of threadfin shad might be seen in 1987, no recovery of shad numbers occurred in 1987 or 1988. Striped bass (Morone saxatilis) predation in the open water has been intense enough to all but - 1- eliminate the pelagic shad population in Lake Powell . Unless the striped bass population suffers a dramatic reduction, or other forage items become available to reduce predation on threadfin shad, the pelagic population of shad will most likely continue to be depressed in the future. -2- , w W a rm C re e k T • I M ile s I I o 5 10 T ra w li n g S ta ti o n Ic ht hy op la nk to n S ta ti on H a li , C re e k ~ A r/ zo ni -- -_ C ha ol C an yo n T lc ab oo C a n yo n S an J ua n R iv e r '- - " ( - - - - P lu ta F ar m s W as h F ig u re 1 . M ap o f L ak e P o w el l sh ow in g tr a w li n g a nd ic h th y o p 1 an k to n n e tt in g s ta ti o n s fo r th re a d fi n s h ad . , -'" 2 0 0 0 1 0 0 0 3 0 0 2 0 0 1 0 0 2 0 0 0 1 0 0 0 3 0 0 2 0 0 1 0 0 '- '0 : -.. • • • • : -.. · , · " • • , • • • • • • • • • · • • • • • • • • • • • • • • • • • • • • • • • , ... , , " , , , \ , , , , , , , \ , , , ... -. , , " , , " , ~ 1 9 8 8 - - - - 1 9 8 7 • •• •• •• •• •• •• •• •• • .. .. .. ... ... · / .... '" M ay Ju ne W ah w ea p Ju ly A ug us t C re e k S ep t. M a y Ju ne J u ly W ar m C re e k F ig u re 2 . M ea n nu m b e r o f la rv a l sh ad c o ll e c te d p e r ic h th y o p la n k to n n e t to w , lo w e r L ak e P ow e ll , 1 9 8 7 -8 8 . A u g u st S e p t. , <.n 2 0 0 0 3 0 0 2 0 0 10 0 2 0 0 0 1 0 0 0 3 0 0 2 0 0 >z ~ . ... .. .-- ... ... .•. ... .. o o . . . . . . . . . . . . 1 0 0 M ay Ju ne Ju l y A ug us t S ep t. B u ll fr o g C re e k •.. , ... .- . M ay 1 9 8 8 - - - - - 1 9 8 7 . •• •• •• •• •• •• •• •• • • Ju n e Ju ly A ug us t S ep t. H a ll s C re e k F ig u re 3 . M ea n nu m be r o f la rv a l sh ad c o ll e c te d p e r ic h th y o p la n k to n n e t to w , m id L ak e P o w el l, 1 9 8 7 -8 8 . Table 1. Mean number of larval threadfin shad collected per ichthyoplankton net tow, Navajo Canyon; Lake Powell, 1984-1988 . Saml1.le Month May June July August September *not sampled Table 2 . Sample River Month May June July August September 1984 1985 1986 1987 1988 791 48 23 551 273 47 40 702 251 59 4 24 2 149 209 2 65 0 4 4 ns* 10 1 1 0 Mean number of larval threadfin shad collected per ichthyoplankton net tow, San Juan River Arm, Lake Powell , 1987- 1988. Piute Red Wall Piute Farms Wash San Juan 1987 1988 1987 19~ 1987 1988 16 4 3 3 0 1 473 156 151 1 7 0 37 24 0 12 3 3 6 14 1 16 1 25 ns* 6 ns 0 ns 1 *not sampled -6- 'c _. " u , -..j , . OJ :., ... '" . ., E " z - - - - .,.. ..,. ... ~o - "" '" 1/ '·' \ .. / ' \ Y \\ f\ " I \ \ i ~ I t.\ 77 7. 7 . \ I \~' \ ; i ' j' ,\ \ ! " -\ V / ,,"= = 8 0 81 .2 Y ea r !A ~, ., jI -:,. !/ \. I.' . / \ .L ___ ~:.:'::= ."'. 8' .4 8 5 sa 87 F ig u re 4 . M ea n nu m be r o f th re a d fi n sh ad c o ll e c te d p er tr a w l to w , Ju ly -S e p te m b e r, L ak e Po w e 1 1 , 19 87 -8 8 . 8 8 -8- MEASUREMENT OF FISHERY HARVEST, PRESSURE AND SUCCESS JOB II METHODS Creel census was conducted from April through October 1988, at five major access areas on Lake Powell: Wahweap, Bullfrog, Hall's Crossing, Piute Farms, and Hite. Anglers were interviewed as they returned to launch ramps. Catch rates (fish/angler hour) were estimated from data reported by anglers for the census day and previous day of fishing. Estimates of angling pressure were based on recreational use data collected by National Park Service (NPS) at access points. Food habits of striped bass, walleye (Stizostedion vitreum) and largemouth bass (Micropterus salmoides) were observed and recorded by percent occurrence and presented in Jobs III and IV of this report. A computer program was utilized to summarize data collected from the creel survey. RESULTS AND DISCUSSION In 1988, a total of 3,224 boating parties were interviewed by creel clerks. A total of 737 parties (22.9 percent) had fished. Recreational boating use (fishing and non- fishing) has increased from 342,887 boat-days in 1985 to 429,347 in 1988. Angling pressure has not kept pace. Fishing boat-days has fallen from 128,186 (41 percent of total) in 1985 to 98,148 (22.9 percent) in 1988 (Figure 5). The decline in percentage of fishing boats may reflect the change that has occurred in Lake Powell fisheries since the last census. Percentage of walleye and black crappie in the total harvest has declined. Largemouth bass, and striped bass harvest percentage has stayed essentially the same while the percentage of bluegill (Lepomis macrochirus), channel catfish (Ictahirus punctatus) and smallmouth bass (Micropterus dolomieui) has increased (Table 3). A larger percentage of boaters fished in 1985 when the average size of striped bass, the most commonly harvested fish, was larger (Job IV). The lake wide mean creel rate was the same as measured in 1985 at 0.41 fish/hour (Table 4). The highest creel rate was observed at the Bullfrog access area at 0.53 fish/hour. Hite had the highest creel rates for largemouth bass (0.06) and bluegill (0.11). Bullfrog had the highest rate for striped bass (0 . 40) while Piute Farms had the highest rates for black crappie (Pomoxis nogromaculatus) (0.03), walleye (0.03) and channel catfish (0 . 11). Many fish that are caught by anglers are not harvested but returned to the lake alive. The total catch rate, including creeled and released fish, was 0.81 fish/hour which is double the creel rate (Table 5) . -9- Largemouth bass are released at an equal rate to those that are kept (0.04 fish/hr) while smallmouth bass are released (0.04 fish/hour) much more often than they are kept (0.01 fish/hour). Striped bass are kept more often than released while bluegill are released more often. The majority of anglers interViewed (45 percent) were willing to harvest any species of fish while 37 percent were actively pursuing striped bass (Table 6). Anglers specifically seeking largemouth bass and smallmouth bass comprised 13 percent. The fisheries at Hite and Bull f rog were used most often by Utah anglers, while Hall's Crossing had more fi shermen from Colorado. Piute Farms and Wahweap were used primarily by anglers from Arizona (Table 7). Lakewide, only 30 percent of the anglers were from Utah. Clearly, Lake Powell is an important recreation area and sport fishery for the states of Utah and Arizona and many surrounding states. - 10- , ~ ~ , 45 0 40 0 35 0 ~ 3 0 0 , T ot al 0 0 ..- -.. ~ U l 0 - 0 O c 25 0 rn o U l " - : 1 0 0 20 0 L '- f - 1l' --- ' E 15 0 :1 Z 10 0 50 0 ' / ff i ~ ff i n n ~ n 79 ff i ~ ff i ~ 66 68 70 72 74 76 78 80 82 84 86 88 Y ea r F ig u re 5 . In d ic e s o f to ta l r e c r e a ti o n a l b o a t u se an d a n g li n g p r e ss u r e , L ak e Po w e ll , 19 6 5- 1 9 8 8 . Table 3. Species composition (percent) of total angler harvest at Lake Powell April through October, 1988. Piute SQecies Hite Hall's Bullfrog Farms WahweaQ Largemouth bass 13.1 12 . 0 6.2 9.8 8.1 Black crappie 1.3 0 . 0 0 . 1 5 . 8 1.4 Walleye 1.8 2.3 0 . 3 6 . 0 3 . 2 Striped bass 42.8 65.8 52 . 4 42 . 9 73 . 8 Channel catfish 12.7 12.0 9 . 1 21.8 8 . 9 Bluegill 25.0 5.5 24.6 10 . 8 1.3 Smallmouth bass 1.7 1.3 5 . 6 1.2 1.7 Other 1.6 0.6 1.8 1.9 1.6 Table 4. Sport fisheries creel rates (fish/angler hour) by species and access area, Lake Powell, April-October 1988 . Piute SQecies Hite Hall's Bullfrog Farms WahweaQ Largemouth bass 0.06 0 . 04 0.02 0.05 0 . 03 Black crappie 0.01 0.00 0.00 0.03 0 . 00 Walleye 0.01 0.01 0.01 0.03 0.01 Striped bass 0.18 0.24 0 . 40 0.22 0.24 Channel catfish 0.05 0.04 0 . 03 0 . 11 0.03 Bluegill 0.11 0 . 02 0 . 06 0.06 0.00 Smallmouth bass 0.01 0 . 00 0.00 0.01 0 . 01 Other 0 . 01 0.00 0.01 0.01 0 . 01 All species 0.43 0.36 0.53 0.51 0.33 - 12- Total 8.7 1.2 2.5 60.3 10.9 13.4 1.4 1.6 Total 0.04 0.00 0.01 0.25 0.04 0 . 05 0 . 01 0.01 0.41 Table 5. Catch rate, including fish released, by species, Lake Powell, April-October 1988. Percent Released Creeled *Catch Released (fish/hr) (fish/hr) ( fish/hr) Largemouth Bass 56.0 0.04 0 . 04 0.08 Black crappie 44.7 0.00 0 . 00 0.01 Walleye 19.4 0.00 0.01 0.01 Striped Bass 37.9 0.15 0 . 25 0.40 Channel Catfish 49.0 0.04 0 . 04 0.09 Bluegill 66.5 0.11 0.05 0.16 Smallmouth bass 87.9 0.04 0.01 0.05 Other/any 63.0 0.01 0.01 0.02 Total 0.41 0.41 0.81 *Catch = total fish/hr = No. Creeled + No. Released / Total hours -13- Table 6. Species sought by anglers (percent) at Lake Powell, April-October 1988 . Piute Species Hite Hall ' s Bullfrog Farms Wahweap Largemouth bass 13 14 11 13 13 Black crappie 0 0.6 0.0 1 0.0 Walleye 2 2 2 5 2 Striped bass 24 31 52 24 45 Channel catfish 3 3 0.4 7 2 Bluegill 1 0.6 0 . 4 0.0 0.4 Smallmouth bass 0.3 0.0 0.4 2 1 Any 56 48 34 48 36 Table 7. Angler residence (percent) listed by access area, Lake Powell, April through October, 1988. Lake Location Piute Residence Hite Hall's Bullfrog Farms Wahweap Arizona 1.2 13.2 1.3 50.0 55.0 California 5.2 10 . 5 4.0 10.7 23 . 5 Colorado 30 . 8 40.1 36 . 3 9 . 3 5.2 New Mexico 3 . 4 6.6 0.9 11. 7 3.5 Utah 53 . 5 23.0 54.9 16.3 10.9 Other 5 . 9 6 . 6 2.7 2.3 2 . 0 -14- Total 13 0.2 2 37 3 0.7 0.7 45 Total 27 .5 12.6 21.4 3.7 30.9 3.95 INDEX TO ANNUAL FISH POPULATION TRENDS JOB III ANNUAL NETTING METHODS Methods for standardized gillnetting are described in Gustaveson et al. 1985. Stomachs from largemouth bass, walleye, and striped bass were examined to quantify food habits by percent occurrence. RESULTS AND DISCUSSION A total of 130 fish was collected in 80 net-days . Catch rate was highest at the Rincon, which was the only station where fish were caught at the same level as in 1987 (Table 8). The total catch rate for 1988 was 1.62 fish/net-day, which is lower than the previous two years, 2.18 and 2 . 16 fish/net-day, respectively. Walleye were the most frequently sampled fish in 1988 . Walleye catch rates remained stable (Figure 6), while striped bass continued a decline of recent years, to only 0.18 fish/net-day in 1988. Largemouth bass catch rates remained stable maintaining the small gains of recent years (Figure 7) . The percent of stomachs with food was greater in 1988 than in 1987. All three species sampled had a higher percent of stomachs with food, walleye being the lowest at 58%. In 1987 crayfish (Orconectes virilis) was the dominant food item for all three species, while in 1988 threadfin shad dominated the diet of striped bass and walleye at 46% and 76% occurrence, respectively. Crayfish was still the most common food item for largemouth bass at 96% (Table 9). - 15- Table 8. Catch rates (fish/net day) during annual gi11netting, Lake Powell, March 1988. Good Good San Padre % of Species Hope Rincon Juan Bay Total Catch Striped bass 0.20 0 . 50 0.00 0 . 00 0 .18 10.8 Walleye 0 . 50 1.25 0.60 0.15 0 .63 38 . 6 Largemouth bass 0 . 55 0.25 0 .50 0.25 0.39 24.1 Channel catfish 0.00 0.35 0 . 10 0 . 05 0.13 7.7 Carp 0.25 0 .25 0.10 0 .25 0.21 13.0 Yellow bullhead 0 . 05 0.00 0.00 0.00 0.01 0.6 Bluegill 0.00 0 . 00 0.05 0.10 0.04 2.3 Green sunfish 0 . 00 0.00 0 .10 0.05 0.04 2 . 3 Sma11mouth bass 0 . 00 0.05 0 . 00 0 . 00 0.01 0 . 6 Total 1.55 2.65 1.45 0.85 1.62 100 - 16- Lake Powell Trend Netting Walleye 6,------------------------------------, 5 ........... ............ .......................... ..... .... .............. .......................... ............ ........ . 4 ........................ ................................... .................. ....... ..................... . 3 ·············· 2 ···· . o ,-.-.-.-.-'-.-.--r-r~ ~ ~ ~ n ~ ~ ~ ffi ~ n ~ ~ ~ 00 ~ M ffi ffi F igure 6 . Year Catch rates ( f ish/net day) for walleye annual netting, Lake Powe ll, 1971-88 . - 17- -8~ l. OJ z ',- ~ "- Lake Powell Trend Netting Largerrlouth Bass 5'.----------------------------------------~ 5 4' 3 ' 2 , .. ' .". ') ''---,--,--,--,--,--,--,--,--,-,--,--,--,--,--,--,---,-,-' {- I I I I I I I I I I I I I I ! I 71 73 75 77 79 81 83 85 87 n ~ ~ ~ 00 ~ M ffi ffi Yair Figure 7. Catch rates (fish/net day) for l argemouth bass annual netting, Lake Powel l 197 1- 1988 . -18- Table 9. Percent occurrence of food items in fish stomachs collected in gill nets, Lake Powell, March 1988. (Percentages based only on number of stomachs containing food.) Striped bass Largemouth bass Walleye Sample size (n) 14 31 50 Empty Stomachs 1 (7%) 8 (26%) 21 (42%) Stomachs with food 13 23 29 Food Item Crayfish 3 (23%) 22 (96%) 0 (0%) Plankton 5 (38%) 0 (0%) 1 (3%) Fish Threadfin shad 6 (46%) 2 (9%) 22 (76%) Centrarchids 1 (8%) 2 (9%) 4 (14%) Green sunfish 0 (0%) 3 (13%) 1 (3%) Unknown fi sh 0 (0%) 0 (0%) 3 (10%) - 19- -20- ELECTRO FISHING METHODS E1ectrofishing procedures were ·simi1ar to those described by Gustaveson et a1. 1985. Each of five stations was sampled for one hour. Index of species abundance at each location was mean catch rate (fish/hr of e1ectrofishing). RESULTS AND DISCUSSION A total of 1,558 fish was collected during 5 nights of e1ectrofishing. This value is down from 2,217 fish caught in 1987, with the San Juan station having the greatest decline. The San Juan station fell from 826 fish/hr in 1987 to only 175 fish/hr in 1988 (Table 10) with most of the decline represented by fewer green sunfish. Largemouth bass yoy, bluegill and green sunfish all declined in relative abundance. Largemouth bass yoy fell from 4.8 percent of the catch in 1987 to 0.6% in 1988; bluegill fell from 18.7% to 6 . 7% and green sunfish (Lepomis cyane1lus) fell from 50.7% to 35.3%. Smallmouth bass was the the only species to show a significant gain. They rose from 16.0% of the catch in 1987 to 42.5% of the catch in 1988. Sma11mouth bass continue to show good reproduction and an expanding population (Job V). Lakewide the yoy smallmouth bass had a mean length of 115 mm (Table 11). This compares favorably with largemouth bass with a lake-wide mean of 90 mm total length. -21- Table 10. Mean catch rate (fish/hr) of fish collected by electrofishing, Lake Powell, September, 1988. Good % of Hope Stanton San Warm Total Species Bay Creek Rincon Juan Creek Catch Largemouth bass, yoy 0 1 0 0 8 0.6 Largemouth bass, age 1 and older 3 2 0 0 0 0.3 Black crappie, yoy 0 0 0 1 5 0.4 Striped bass, yoy 41 3 0 1 0 2 . 9 Smallmouth bass, yoy 108 425 96 35 59 46 . 4 Smallmouth bass, age 1 and older 2 8 0 2 0 0.8 Bluegill, all ages 10 11 17 9 59 6 . 8 Green sunfish all ages 85 174 143 123 34 35.9 Channel catfish, 4 1 14 4 69 5 . 9 all ages Yellow bullhead, 1 0 0 0 0 0.0 all ages All species 254 625 270 175 234 100 . 0 - 22- Table 11. Mean total length (mm) measured by subsampling young- of- year fish collected by electrofishing, Lake Powell, September, 1988 . Good Mean % Hope Stanton San Warm of Total Bay Creel Rincon Juan Creek Catch Species TL (mm) (TL (mm) TL (mm) TL (mm) TL (mm) TL (mm ) Largemouth bass 130 0 0 85 90 Sma11mouth bass 147 118 108 126 79 115 Striped bass 104 123 105 107 Black crappie 82 67 69 Table 12 . Percent occurrence of food items in striped bass stomachs collected during summer creel census and fall gill netting, Lake Powell, 1988 (percentage based only on number of stomachs containing food) . Sample size (n) Empty stomachs Stomachs with food Food Items Zooplankton Crayfish Fish Shad Sunfish spp . Unknown fish Bai t (Anchovy) Debris Uplake creel census 298 22% 233 46% 17% 14% 0 . 4% 7% 46% 1% - 23- Downlake Fall gill net creel (4 stations census combined) 273 402 30% 54% 190 187 29% 71% 18% 13% 6% 8% 0 . 5% 3% 16% 11% 37% 0 3% 0.5% - 24 - PROJECT AGREEMENT NARRATIVE OPMENT Job IV METHODS Biological information was obtained from all striped bass sampled during normal field collections. Data necessary to determine age and growth, food habits, maturity, and condition (Kf1) were routinely taken as described in Gustaveson et a1. 1985 . RESULTS AND DISCUSSION Striped bass spawning began 13 April and continued through 26 May 1988. Spawning occurred when calm weather allowed rapid warming of the water surface layers in a short time. A five degree surface temperature rise on one day triggered spawning activity. Spawning occurred from 17-22 Co. Windy conditions which mixed the lake and cooled surface temperatures curtailed spawning activity. The spawning season exhibited at least three distinct peaks in activity during April and May. Relative abundance of yoy striped bass sampled by electro fishing was lower than other years with only 4 fish captured at mid and down lake stations. Some 41 striped bass were sampled at Good Hope Bay near the inflow of the Colorado River which was less than collected at that station last year (Table 10). These data suggest that reproduction from the tributaries was more important than in-lake spawning during 1988. Young-of-year sampled during annual trend netting was the lowest reported in any year except 1985. In contrast, relative abundance of striped bass yearlings was the second highest reported and abundance of older striped bass was the highest reported (Figure 8). The large population of juvenile striped bass is advancing in age but not in size. Average total length of striped bass captured during annual fall netting was 348 mm. Total length of striped bass collected during this survey continued to decline. Respective size of fish sampled has decreased from 555 mm, to 423 mm, 393 mm, and 348 mm over the past four years. Some 973 striped bass stomachs examined in 1988 showed zooplankton to be the most commonly used food item (Table 12). Fish taken by angling or by netting during all season of the year at any location were most likely to have zooplankton in their stomachs. Crayfish continued to be an important secondary food item. Shad and fish digested beyond recognition were third in importance. Piscivorous striped bass continued to be unable to effectively exploit centrarchids as an alternative food source. In the absence of a pelagic schooling forage fish (Job I), striped bass have used plankton as their primary food instead of consuming other fish species. Some 9% of all stomachs examined contained -25- an ulcerous lesion. It is chronic stress that occurs of low food availability. theorized that stomach ulcers are a symptom of in the striped bass population during periods Incident of ulcers increased with age of fish. Physical condition of striped bass sampled with gill nets in 1988 was essentially the same as in 1986 and 1987 (Figure 9). Juvenile fish «500 mm) had an average condition factor (Kfl) of 1 . 17 . Only 21 striped bass larger than 500 mm (range 503-583) were captured during annual netting and had an average Kfl of 0.94. Larger fish taken by anglers during the summer had an average K factor of 1 . 02 while striped bass under 500 mm had a Kfl of 1.10. In both groups of fish, condition declined as fish size increased. -26- , N ...... S tr ip ed B a ss R el a ti v e A b u n d a n ce F a ll n e tt in g a ll s ta ti o n s c o m b in e d ~ ~ 01 S ill c '6> ~ ~ g a a a , m f- U1 Fig u re 8 . 14 12 1 0 8 6 4 2 0 ' ~ ~ ~ ) ~ t d h 2 ~ ) ~ ) " " , ! ! 19 8 1 19 83 19 8 5 19 87 1 9 82 19 84 19 8 6 1 9 88 Y E A R A v er ag e nu m be r o f s tr ip e d b as s ca ug h t d u ri n g fa ll g il l ne t t in g o n L ak e Po w e ll , e x p re ss e d as f is h ca u gh t/ IO O O f t L o f ne t / 12 h r se t , 19 81 - 19 88 . ~ ~ ~ y - o - y Y ea rli ng ~ ~ . ~ A g e 2 + , N (X l , 1. 6 ~ _ 1 .5 [l ) <: CD 1 .4 .¥ ... o 1 .3 II. . 1 .2 a: 1 .1 0 l- o 1. 0
geography
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https://digitallibrary.utah.gov/awweb/awarchive?type=download&item=68720
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1989
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Content: 7bc498a0f22d2afd52aad81e66054ab8b1a783a7 | Abstract: 70e2b7ea7d07ee69a7c2b23908458e83f76fcd1d