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W 2800.7 F532r/w no.32 F-50-R-17 2010 c.1 FINAL REPORT FEDERAL AID GRANT NO. F-50-R-17 Fish Research for Oklahoma Waters PROJECT NO. 32 Growout channel catfish stocking evaluation of Oklahoma's small impoundments OKLAHOMA DEPARTMENT OF WILDLIFE CONSERVATION JANUARY 1, 2010 through DECEMBER 31, 2010 FINAL REPORT State: Oklahoma Grant Number: F-50-R-17 Grant Title: Fish Research for Oklahoma Waters Project Number: 32 Project Title: Growout channel catfish stocking evaluation of Oklahoma's small impoundments Project Leader: Greg Summers Contract Period: From: January l, 2010 to: December 3l, 2010 I. Project Objective: Determine/calculate 1.) catch rates, length frequencies, condition, and age structure on nine small lakes before and after experimental stocking rate manipulations and 2.)angler catch rates and satisfaction before and after stocking rate manipulations on nine small lakes. II. Summary of Progress A. Introduction Channel catfish (lctalurus punctatus) are stocked in small impoundments throughout Oklahoma as put-grow-take or put-take fisheries. These stockings are necessary to sustain an acceptable sport fishery as natural recruitment of channel catfish in small impoundments is often low (Santucci et. al. 1994). It is important these stockings make a significant contribution to the fishery as the Oklahoma Department of Wildlife Conservation (ODWC) invests considerable resources in them. Channel catfish are difficult to sample in small impoundments with most gear types. As a consequence, the ODWC has conducted few catfish surveys on small lakes. Recently, tandem hoop nets (3 tied in a series) have been used to effectively collect these fish in small impoundments (Flamming and Schultz 2007, Michaletz and Sullivan 2002). Tandem hoop nets collect channel catfish more efficiently than gill nets or electrofishing and also produce representative samples offish >250 mm (Buckmeier and Schlechte 2009, Michaletz and Sullivan 2002). Many small impoundments are stocked annually with growout (229 mm) channel catfish at rates as high as 99 fish/ha. It is possible that some of these small bodies of water are overstocked as stocking rates remain high and the number of catfish anglers in Oklahoma have decreased since 1996 (US. Dept. ofInterior et. al. 2006). Michaletz (2009) found size structure, condition, and growth to be highly variable on 60 small impoundments in Missouri; therefore he suggested that stocking rates be individually determined for each lake. The population structure of channel catfish in department lakes needs to be determined as well as stocking rates evaluated. Since channel catfish are one of the few species managed in small impoundments by stocking, the number of fish stocked can have a direct effect on angler catch rates and satisfaction. Reduced stocking rates could potentially improve the size structure of overcrowded populations and in turn increase angler satisfaction. Unless angler catch rates and satisfaction are negatively impacted, reduced stocking rates could also potentially free hatchery ponds and resources for production of other species. B. Methods Population characteristics Nine small impoundments, American Horse, Burtschi, Dahlgren, Evan Chambers, Hall, Nanih Waiya, Ozzie Cobb, Raymond Gary, and Watonga, were sampled with tandem hoop nets (three in a series) during July and August 2009. Historically these lakes have been stocked annually in August through October with growout (229 mm) channel catfish at the rate of 99 fishlha. These impoundments are highly diverse, ranging geographically from the panhandle in Northwest Oklahoma to Southeast Oklahoma. The nine lakes range in size from 14 to 96 ha and encompass trophic levels from oligotrophic to hypereutrophic. In addition to channel catfish, these impoundments primarily support populations of sunfish, largemouth bass, and crappie. Each tandem hoop net set consisted of three hoop nets that were approximately 3.4 m long with seven fiberglass hoops. The largest hoop was .8 m in diameter at the mouth and successive hoops slightly decreased in size to the cod end. Two hoop nets with 25- mm-bar mesh and one hoop net with 12.5-mm-bar mesh were randomly ordered in each series. Hoop nets were connected mouth to cod end by bridles that were l.8 m total length. This allowed nets in a series to be fished approximately 0.9 m apart. Each net was baited with approximately 0.9 kg of cheese log in a 907 g plastic sample jar with approximately 25 to 30 holes that were 6 mm in diameter. Effort at each lake was determined by lake size: <20 ha -3 series, ::::2:0 and <61 ha - 5 series, :::::61to <1Olha - 8 series, :::::1 01ha - 10 series (Kline et al. 1995). Sites were randomly selected in the littoral zone at each lake. Nets were set parallel to the shoreline in 2.4 to 3.7 m of water to limit by-catch of turtles. If insufficient depth or anoxic conditions were encountered « 4mg/ml in 8 to 12 feet of water), nets were set shallower. Shorelines with more than a 45° slope were avoided to keep hoop nets from rolling to deeper water. Tandem hoop nets were fished for 72 h before being retrieved. All channel catfish collected were measured (mm.TL), and 20 fish from each 20 mm length group were weighed and retained for age determination by lapilli (Long and Stewart 2010) otoliths. All other fish were released back into the lakes. Catches were recorded separately by each net but were pooled by series to express CPUE as number of channel catfish per series. CPUE and mean length were calculated at each lake and compared among lakes. Size structure at each lake was analyzed by length frequency histograms and PSDs. In addition relative weights (Wr) were determined for the overall population as well as specific length groups. Mean length at age was determined from age analysis oflapilli otoliths using methods described by Mauck and Boxrucker (2005). Since some lakes were stocked with fish from one cohort in different years, Von Bertalanffy growth curves were used to estimate length at age in the respective year. Total annual mortality was determined from catch curve data. Angler survey In order to assess channel catfish angler catch rates and satisfaction, a survey box was placed in a high traffic area at each lake at the beginning of October 2010. A sign was attached above each survey box to encourage catfish anglers to complete a survey (Figure 1). Survey cards briefly explained the purpose of the survey and asked party size, hours spent fishing, number of channel catfish caught and kept, length of fish caught and kept, and satisfaction of number and length of fish caught (Figure 2). Anglers were given the choice to either drop the completed survey in the box or mail it in with prepaid postage. The total number of anglers, hours of angling effort, and number of fish caught/kept were summarized for each lake. The number of angling hours required per fish, mean length of fish caught/kept, percentage of fish caught that was kept, and mean satisfaction for number and length of fish were also calculated for each lake. C. Results/Discussion Population characteristics Overall, the nine lakes sampled yielded a mean catch rate of 80 fish/series with 3,922 channel catfish being caught from the nine lakes in 2010. Catch rates varied substantially among lakes. Raymond Gary and Ozzie Cobb produced the lowest CPUE (5 fish/series, n=54 and 18 fish/series, n=90, respectively) while Burtschi and Watonga had the highest CPUE (172 fish/series, n=I,372, and 135 fish/series, n=676, respectively). The other lakes yielded catch rates between 51 and 103 fish/series (Table 1). Mean length among lakes ranged from 374 mm at American Horse to 293 mm at Burtschi (Table 1). Growth seemed to be negatively correlated with relative abundance suggesting density dependence. Results from length at age data suggest channel catfish from American Horse and Raymond Gary had the highest mean length at age while channel catfish from Evan Chambers and Burtschi grew slowest (Table 2). Fish stocked in Dahlgren, Nanih Waiya, and Ozzie Cobb, reached 305 mm within one year after being stocked. Lakes American Horse and Raymond Gary were similar in length after the first year of growth at 301 and 299 mm respectively. Channel catfish at lakes Burtschi, Hall, and Watonga did not reach 305 mm until the third year after being stocked, while it took fish at Evan Chambers five years to reach this size. Catch curve analysis from length at age data indicated mortality was moderately high and similar among lakes (44%-59%) except at Chambers where it was 34% (Table 1). Length frequencies and low PSDs further indicated a proportionally large number of small individuals in lakes Burtschi, Chambers, Hall, and Watonga (Figure 3, Table2). In addition, Dahlgren and Nanih Waiya also had a low proportion of quality size individual as indicated by PSDs (Table 4). Low PSDs are often an indication of slow growth (Guy and Brown 2007). Channel catfish populations at American Horse, Ozzie Cobb and Raymond Gary had higher PSDs and resembled more of a balanced population. Relative weights ranged from 93 at Burtschi to 79 at Raymond Gary (Table 3). Body condition did not seem to be associated with growth as Raymond Gary, Ozzie Cobb, Dahlgren, and Nanih Waiya. All had substantially lower relative weights than the other populations. At the time of sampling, these four lakes were all stratified at <3 m with no dissolved oxygen in the hypolimnium while the other lakes supported dissolved oxygen at depths >5 m. Thermal stress and reduced dissolved oxygen may have exacerbated the poor body condition of channel catfish in these lakes. Angler survey Twenty-nine angler surveys were received between October and December 2009. Lake Burtschi had the highest number of respondents (n=8) while no surveys were received from Lake Ozzie Cobb. The mean catch rate (no./hour) channel catfish was lowest at Watonga (0.014). The other lakes were substantially higher ranging from (0.125 at Nanih Waiya to (0.667) at Raymond Gary and Burtschi. Mean length offish caught by anglers at each lake was similar to mean length obtained from tandem hoop net samples. Anglers from American Horse, Nanih Waiya, and Raymond Gary kept an average of>67% of the fish they caught while all other lakes kept <20% of fish caught. Satisfaction for number offish caught and length offish was highest at Lake Nanih Waiya and lowest at Lake Watonga. D. Conclusions/Recommendations • Relative abundance, as measured by tandem hoop nets, was highly variable among lakes. Growth seemed to be negatively correlated with relative abundance suggesting density dependence. • Length frequencies and low PSDs further indicated slow growth at Lakes Burtschi, Evan Chambers, Hall, and Watonga. • Relative weights (Wr) were not associated with growth. Environmental conditions such as temperature and dissolved oxygen may be related to body condition. • The angler survey should continue through September 2011. If angler survey returns continue to be low, interviews will be conducted to increase the number of respondents. • All nine lakes should be sampled in 2011 to determine catch rates, length frequencies and body condition. • Lakes with slow growth and high relative abundance (Burts chi, Evan Chambers, Hall, and Watonga) should be stocked with 13 fish/ha while lakes with fast growth rates and moderate abundance (American Horse, Dahlgren, and Nanih Waiya) should continue to be stocked with 99 fishlha. Stocking rates at Raymond Gary and Ozzie Cobb should be increased to 150 fish/ha as they exhibited fast growth but had low relative abundance. III. Significant Deviations: None Preparedby: _ Chas Patterson, Senior Fisheries Biologist Date: Approved by:_---'-"0IY<!i?:;c_-=-=--------'------'Cb_'-----=~=___J__ _ Fisheries Administration Oklahoma Department .f Wildlife Conservation -:r' ,~ John Stafford Federal Aid Coordinator Oklahoma Department of Wildlife Conservation IV. Literature Cited U.S. Department of the Interior, Fish and Wildlife Service, and U.S. Department of Commerce, U.S. Census Bureau. 2006. 2006 National Survey of Fishing, Hunting, and Wildlife-Associated Recreation. Buckmeier, D. L., and J. Warner. 2009. Capture efficiency and size structure of channel catfish and blue catfish sampling gears. North American Journal of Fisheries Management. 29 :404-416 Flamming, M. K., and R. Schultz. 2007. Evaluation of hoop-net size and bait selection for sampling channel catfish in Iowa impoundments. North American Journal of Fisheries Management. 14:781-789 Kline, D., B. DeCook, L. Mitzner, J. Pitlo, J. Schwartz, G. Sobotka, and L. Squibb. 1995. Standard gear and techniques for fisheries surveys in Iowa. Des Moines, Iowa Long, J. M. and D. Stewart. 2010. Verification of otolith identity used by fisheries scientists for aging channel catfish. Transactions of the American Fisheries Society. 139: 1775-1779 Mauck, P. and J. Boxrucker. 2005. Abundance, growth, and mortality of the Lake Texoma blue catfish population: implications for management. Proceedings of the Annual Conference of the Southeastern Association ofFish and Wildlife Agencies. 58:57-65 Michaletz, P. H., and K. Sullivan. 2002. Sampling channel catfish with tandem hoop nets in small impoundments. North American Journal of Fisheries Management. 22:870-878 Michaletz, P. H. 2009. Variable responses of channel catfish populations to stocking rate: density dependent and lake productivity effects. North American Journal of Fisheries Management. 29:177-188 Santucci, V. J., D. Wahl, and T. Storck. 1994. Growth, mortality, harvest, and cost-effectiveness of stocked channel catfish in a small impoundment. North American Journal of Fisheries Management. 14:781-789 Table 1. Sample size, CPUE (fish/series), mean length (mm), annual mortality, and PSDs of channel catfish from nine Oklahoma small impoundments in July and August 2010. Lake SaSmizpele CPUE lMenegatnh Annual PSD (mm) mortality American Horse 257 51 374 46 19 Burtschi 1372 172 275 59 2 Evan Chambers 498 100 293 34 6 Dahlgren 244 81 352 45 5 Hall 310 103 302 54 3 Nanih Waiya 426 85 333 55 6 Ozzie Cobb 90 18 367 44 28 Raymond Gary 54 5 348 58 33 Watonga 676 135 318 47 6 Table 2. Mean lengthatage (mm) of channel catfishfrom nine smallimpoundments acrossOklahoma in2010. Lengths noted with * were derivedfrom Von Bertalanffygrowth curves. Year American Evan stocked Horse Burtschi Chambers Dahlgren Hall 2009 301 262 275 330 281 2008 401* 275* 277* 336* 304* 2007 462* 309* 299* 378* 335* 2006 509 273 279 349 381 2005 582 396 350 506 380 2004 660 421 337 490 480 2003 320 326 2001 505 630 371 2000 450 439 1999 410 1998 408 1997 387 1996 430 1995 440 1994 1993 350 Naniah Waiya Ozzie Cobb Raymod Gary Watonga 313 324 368 449* 498* 319 343 429 446* 473* 454 299 393 461 532* 601* 392 265 290* 325* 352 392 432 520 576 570 580 Table 3. Relative weights (W;.) of channel catfish from nine small impoundments in Oklahoma in July and August 2010. Mean Relative Weights (WrJ Sub- Stock Quality Preferred stock (2:281 (~411 to (~611 to s Memorable (:::;280 to s 410 :::;610mm 710mm (~ 711 to :::; Lake Overall Wr mmTL) mmTL) TL) TL) 910 mm TL) American Horse 90 117 87 88 91 94 Burtschi 93 98 86 89 104 Dahlgren 80 83 79 80 Evan Chambers 88 92 86 84 Hall 90 97 86 83 Nanih Waiya 83 90 82 84 72 Ozzie Cobb 82 95 82 80 Raymond Gary 79 80 78 82 Watonga 87 99 84 80 Table 4. Summary of angler survey responses administered at nine Oklahoma small impoundments starting in October 2010. Satisfaction was ranked on a scale from 1 to 5 with 1 being dissatisfied and 5 being satisfied. Nanih Ozzie American Burtschi Chambers Dahlgren Hall Wayia Cobb Raymond Watonga Horse n=4 n=8 n=4 n=3 n=l n=l n=O Gary n=4 n=4 Total # of anglers 9 17 7 9 2 2 4 14 Total angling effort (hrs) 91.2 52.5 39.0 17.5 8.0 18.5 72.0 Total # fish caught 44 35 6 3 0 1 12 1 Angling hours/fish 2.1 1.5 6.5 5.8 8.0 1.5 72.0 Total # fish kept 30 6 1 0 0 1 8 % fish kept that were caught 68 17 17 0 0 100 67 0 Mean length of fish caught (in) 13-16 8-12 8-12 13-16 13-16 13-16 8-12 Mean length of fish kept (in) 13-16 8-12 8-12 13-16 13-16 13-16 8-12 Mean satisfaction of # caught 3.3 2.6 1.8 4.0 5.0 3.5 1.0 Mean satisfaction of length 1.8 1.9 1.7 3.0 5.0 3.5 1.0 Figure 1. Sign specifications used above channel catfish survey box at nine small impoundments in Oklahoma starting in October 2010. f------------- 24·' ----------------j ~---------------.--"'\ ______TTENTION: ,..--- -atfish Anglers LEASE FILL OUT SURVEY below Figure 4. Channel catfish survey administered at nine small impoundments across Oklahoma starting in October 2010. Channel Catfish Survey The Oklahoma Department of Wildlife Conservation is evaluating the channel catfish stocking program on Department lakes. Different stocking rates are being tested to determine which best meets the needs of both anglers and fish populations Channel catfish anglers, we need your help! After you're done fishing today, please fill out the attached survey and drop it in the box (or in the mail at your convenience). We'd like you to complete this channel catflsh survey each time you fish here during the next year ' We appreciate your support Thank you for taking tile time to complete a channel catfish survey! Sincerely, Chas Patterson Fisheries Biologist (405) 325-7288 Date: . _ 2. Your home zip code: _ 3. Did you fish for channel catfish today? 0 Yes 0 No ~ If no, survey is complete! 4. Number of people fishing for channel catfish in your group today: 5. What time did your group. a) ..start fishing for catfish today? 0 a.rn. 0 p.rn b) . finish fishing for catfish today? 0 a.rn 0 p.rn. 6. How many channel catfish did your group .. a) ... catch today? (If zero, skip to question 8) b) . keep today? 7 What was the average lengtll of channel catfish your group. a) caught today? 0 8-12" 0 '13-'16" 0 17-20" b) kept today? 0 8-12" 0 "13-'16" 0 '17-20" 020"+ 020"+ o rva 8. How satisfied are you with .. Number of channel catfish caught: Length of channel catfish caught: Dissatisfied 1 1 2 2 3 3 4 4 Satisfied 5 5 9. Comments: _ Figure 3. Length frequencies from nine Oklahoma small impoundments in 2010. American Horse 20% 18% 16% 14% .•..12% c: ~ 10% ~~~ .''''.luultultllll'J~.._...J..l~ 140 170 220 250 280 310 340 370 400 430 460 530 560 600 630 730 lenght (mm) 16% 14% 12% .•.. 10% c: Q1): 8% Q) c.. 6% 4% 2% 0% Burtschi ~ r' I 1 I r I r ~Tl 1111" 140 180 220 260 300 340 380 420 460 500 540 580 620 660 700 lenght (mm) Dahlgren 20% 18% 16% 14% .•..12% c: ~ 10% ~ 8% j 6% ; 4% 1 2% 0% '" 20% 18% 16% 14% .c•.:. 12% Q) o 10% cQ.;. 8% 6% 4% 2% 0% ;-. ,.. ,..,., Evan Chambers »l,.,a,.~~ ,1 '1'" - ("'1 1 r I' , 1 1'1 t r I r 11-, 1 1 140 180 220 260 300 340 380 420 460 500 540 580 620 660 700 lenght (m m) 140 180 220 260 300 340 380 420 460 500 540 580 620 660 700 lenght(mm) Figure 3 continued. Length frequencies from nine Oklahoma small impoundments in 2010. Hall Nanih Waiya 20% 18% i 16% 14% i:: 12% ! ~ 10% ~ 8% 6% 4% 2% ! 0% I ,., 20% 18% 16% 14% •c::.•12% ~ 10% Qc;. 8% 6% 4% 2% 0% ,IJ.,1. '#,-,I,.,..,.., '" , , ,.,..,.,..,,-, ,.,-, , , " , .J1J~I~d_~~~ .d 140 180 220 260 300 340 380 420 460 500 540 580 620 660 700 lenght (mm) 140 180 220 260 300 340 380 420 460 500 540 580 620 660 700 lenght (mm) Ozzie Cobb 14% 12% 12% i • 10% •.. 10% I I. •.. 8% c:: 8% 1 cQ:): Qo) II ~ 6% Q) •.. Qc). 6% c. 4% 4% lilllJd . .JL 2% ,,,,,,,,,ftw, 2% 0% ,-- . 0% I 140 180 220 260 300 340 380 420 460 500 540 580 620 660 700 140 Raym ond Gary J~.~L! lit I I I" rl 1,-' 11 J lenght(mm) 180 220 260 300 340 380 420 460 500 540 580 620 660 700 lenght(mm) Figure 3 continued. Length frequencies from nine Oklahoma small impoundments in 2010. 20% 18% 16% 14% •.• 12% c:: ~ 10% ~ 8% 6% 4% 2% 0% Watonga 140 180 220 260 300 340 380 420 460 500 540 580 620 660 700 lenght (mm)
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Title | Growout channel catfish stocking evaluation of Oklahoma's small impoundments 2010 |
OkDocs Class# | W2800.7 F532r/w no.32 F-50-R-17 2010 |
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ODL electronic copy | Deposited by agency in print; scanned by Oklahoma Department of Libraries 6/2011 |
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Language | English |
Full text | W 2800.7 F532r/w no.32 F-50-R-17 2010 c.1 FINAL REPORT FEDERAL AID GRANT NO. F-50-R-17 Fish Research for Oklahoma Waters PROJECT NO. 32 Growout channel catfish stocking evaluation of Oklahoma's small impoundments OKLAHOMA DEPARTMENT OF WILDLIFE CONSERVATION JANUARY 1, 2010 through DECEMBER 31, 2010 FINAL REPORT State: Oklahoma Grant Number: F-50-R-17 Grant Title: Fish Research for Oklahoma Waters Project Number: 32 Project Title: Growout channel catfish stocking evaluation of Oklahoma's small impoundments Project Leader: Greg Summers Contract Period: From: January l, 2010 to: December 3l, 2010 I. Project Objective: Determine/calculate 1.) catch rates, length frequencies, condition, and age structure on nine small lakes before and after experimental stocking rate manipulations and 2.)angler catch rates and satisfaction before and after stocking rate manipulations on nine small lakes. II. Summary of Progress A. Introduction Channel catfish (lctalurus punctatus) are stocked in small impoundments throughout Oklahoma as put-grow-take or put-take fisheries. These stockings are necessary to sustain an acceptable sport fishery as natural recruitment of channel catfish in small impoundments is often low (Santucci et. al. 1994). It is important these stockings make a significant contribution to the fishery as the Oklahoma Department of Wildlife Conservation (ODWC) invests considerable resources in them. Channel catfish are difficult to sample in small impoundments with most gear types. As a consequence, the ODWC has conducted few catfish surveys on small lakes. Recently, tandem hoop nets (3 tied in a series) have been used to effectively collect these fish in small impoundments (Flamming and Schultz 2007, Michaletz and Sullivan 2002). Tandem hoop nets collect channel catfish more efficiently than gill nets or electrofishing and also produce representative samples offish >250 mm (Buckmeier and Schlechte 2009, Michaletz and Sullivan 2002). Many small impoundments are stocked annually with growout (229 mm) channel catfish at rates as high as 99 fish/ha. It is possible that some of these small bodies of water are overstocked as stocking rates remain high and the number of catfish anglers in Oklahoma have decreased since 1996 (US. Dept. ofInterior et. al. 2006). Michaletz (2009) found size structure, condition, and growth to be highly variable on 60 small impoundments in Missouri; therefore he suggested that stocking rates be individually determined for each lake. The population structure of channel catfish in department lakes needs to be determined as well as stocking rates evaluated. Since channel catfish are one of the few species managed in small impoundments by stocking, the number of fish stocked can have a direct effect on angler catch rates and satisfaction. Reduced stocking rates could potentially improve the size structure of overcrowded populations and in turn increase angler satisfaction. Unless angler catch rates and satisfaction are negatively impacted, reduced stocking rates could also potentially free hatchery ponds and resources for production of other species. B. Methods Population characteristics Nine small impoundments, American Horse, Burtschi, Dahlgren, Evan Chambers, Hall, Nanih Waiya, Ozzie Cobb, Raymond Gary, and Watonga, were sampled with tandem hoop nets (three in a series) during July and August 2009. Historically these lakes have been stocked annually in August through October with growout (229 mm) channel catfish at the rate of 99 fishlha. These impoundments are highly diverse, ranging geographically from the panhandle in Northwest Oklahoma to Southeast Oklahoma. The nine lakes range in size from 14 to 96 ha and encompass trophic levels from oligotrophic to hypereutrophic. In addition to channel catfish, these impoundments primarily support populations of sunfish, largemouth bass, and crappie. Each tandem hoop net set consisted of three hoop nets that were approximately 3.4 m long with seven fiberglass hoops. The largest hoop was .8 m in diameter at the mouth and successive hoops slightly decreased in size to the cod end. Two hoop nets with 25- mm-bar mesh and one hoop net with 12.5-mm-bar mesh were randomly ordered in each series. Hoop nets were connected mouth to cod end by bridles that were l.8 m total length. This allowed nets in a series to be fished approximately 0.9 m apart. Each net was baited with approximately 0.9 kg of cheese log in a 907 g plastic sample jar with approximately 25 to 30 holes that were 6 mm in diameter. Effort at each lake was determined by lake size: <20 ha -3 series, ::::2:0 and <61 ha - 5 series, :::::61to <1Olha - 8 series, :::::1 01ha - 10 series (Kline et al. 1995). Sites were randomly selected in the littoral zone at each lake. Nets were set parallel to the shoreline in 2.4 to 3.7 m of water to limit by-catch of turtles. If insufficient depth or anoxic conditions were encountered « 4mg/ml in 8 to 12 feet of water), nets were set shallower. Shorelines with more than a 45° slope were avoided to keep hoop nets from rolling to deeper water. Tandem hoop nets were fished for 72 h before being retrieved. All channel catfish collected were measured (mm.TL), and 20 fish from each 20 mm length group were weighed and retained for age determination by lapilli (Long and Stewart 2010) otoliths. All other fish were released back into the lakes. Catches were recorded separately by each net but were pooled by series to express CPUE as number of channel catfish per series. CPUE and mean length were calculated at each lake and compared among lakes. Size structure at each lake was analyzed by length frequency histograms and PSDs. In addition relative weights (Wr) were determined for the overall population as well as specific length groups. Mean length at age was determined from age analysis oflapilli otoliths using methods described by Mauck and Boxrucker (2005). Since some lakes were stocked with fish from one cohort in different years, Von Bertalanffy growth curves were used to estimate length at age in the respective year. Total annual mortality was determined from catch curve data. Angler survey In order to assess channel catfish angler catch rates and satisfaction, a survey box was placed in a high traffic area at each lake at the beginning of October 2010. A sign was attached above each survey box to encourage catfish anglers to complete a survey (Figure 1). Survey cards briefly explained the purpose of the survey and asked party size, hours spent fishing, number of channel catfish caught and kept, length of fish caught and kept, and satisfaction of number and length of fish caught (Figure 2). Anglers were given the choice to either drop the completed survey in the box or mail it in with prepaid postage. The total number of anglers, hours of angling effort, and number of fish caught/kept were summarized for each lake. The number of angling hours required per fish, mean length of fish caught/kept, percentage of fish caught that was kept, and mean satisfaction for number and length of fish were also calculated for each lake. C. Results/Discussion Population characteristics Overall, the nine lakes sampled yielded a mean catch rate of 80 fish/series with 3,922 channel catfish being caught from the nine lakes in 2010. Catch rates varied substantially among lakes. Raymond Gary and Ozzie Cobb produced the lowest CPUE (5 fish/series, n=54 and 18 fish/series, n=90, respectively) while Burtschi and Watonga had the highest CPUE (172 fish/series, n=I,372, and 135 fish/series, n=676, respectively). The other lakes yielded catch rates between 51 and 103 fish/series (Table 1). Mean length among lakes ranged from 374 mm at American Horse to 293 mm at Burtschi (Table 1). Growth seemed to be negatively correlated with relative abundance suggesting density dependence. Results from length at age data suggest channel catfish from American Horse and Raymond Gary had the highest mean length at age while channel catfish from Evan Chambers and Burtschi grew slowest (Table 2). Fish stocked in Dahlgren, Nanih Waiya, and Ozzie Cobb, reached 305 mm within one year after being stocked. Lakes American Horse and Raymond Gary were similar in length after the first year of growth at 301 and 299 mm respectively. Channel catfish at lakes Burtschi, Hall, and Watonga did not reach 305 mm until the third year after being stocked, while it took fish at Evan Chambers five years to reach this size. Catch curve analysis from length at age data indicated mortality was moderately high and similar among lakes (44%-59%) except at Chambers where it was 34% (Table 1). Length frequencies and low PSDs further indicated a proportionally large number of small individuals in lakes Burtschi, Chambers, Hall, and Watonga (Figure 3, Table2). In addition, Dahlgren and Nanih Waiya also had a low proportion of quality size individual as indicated by PSDs (Table 4). Low PSDs are often an indication of slow growth (Guy and Brown 2007). Channel catfish populations at American Horse, Ozzie Cobb and Raymond Gary had higher PSDs and resembled more of a balanced population. Relative weights ranged from 93 at Burtschi to 79 at Raymond Gary (Table 3). Body condition did not seem to be associated with growth as Raymond Gary, Ozzie Cobb, Dahlgren, and Nanih Waiya. All had substantially lower relative weights than the other populations. At the time of sampling, these four lakes were all stratified at <3 m with no dissolved oxygen in the hypolimnium while the other lakes supported dissolved oxygen at depths >5 m. Thermal stress and reduced dissolved oxygen may have exacerbated the poor body condition of channel catfish in these lakes. Angler survey Twenty-nine angler surveys were received between October and December 2009. Lake Burtschi had the highest number of respondents (n=8) while no surveys were received from Lake Ozzie Cobb. The mean catch rate (no./hour) channel catfish was lowest at Watonga (0.014). The other lakes were substantially higher ranging from (0.125 at Nanih Waiya to (0.667) at Raymond Gary and Burtschi. Mean length offish caught by anglers at each lake was similar to mean length obtained from tandem hoop net samples. Anglers from American Horse, Nanih Waiya, and Raymond Gary kept an average of>67% of the fish they caught while all other lakes kept <20% of fish caught. Satisfaction for number offish caught and length offish was highest at Lake Nanih Waiya and lowest at Lake Watonga. D. Conclusions/Recommendations • Relative abundance, as measured by tandem hoop nets, was highly variable among lakes. Growth seemed to be negatively correlated with relative abundance suggesting density dependence. • Length frequencies and low PSDs further indicated slow growth at Lakes Burtschi, Evan Chambers, Hall, and Watonga. • Relative weights (Wr) were not associated with growth. Environmental conditions such as temperature and dissolved oxygen may be related to body condition. • The angler survey should continue through September 2011. If angler survey returns continue to be low, interviews will be conducted to increase the number of respondents. • All nine lakes should be sampled in 2011 to determine catch rates, length frequencies and body condition. • Lakes with slow growth and high relative abundance (Burts chi, Evan Chambers, Hall, and Watonga) should be stocked with 13 fish/ha while lakes with fast growth rates and moderate abundance (American Horse, Dahlgren, and Nanih Waiya) should continue to be stocked with 99 fishlha. Stocking rates at Raymond Gary and Ozzie Cobb should be increased to 150 fish/ha as they exhibited fast growth but had low relative abundance. III. Significant Deviations: None Preparedby: _ Chas Patterson, Senior Fisheries Biologist Date: Approved by:_---'-"0IY |
Date created | 2011-06-09 |
Date modified | 2011-10-28 |
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