Natural Resource Ecology and Management Natural Resource Ecology and Management Conference Papers, Posters and Presentations
2017 Survival and Growth of Three Geographically Distinct Stocks of Muskellunge Introduced into Midwestern Reservoirs Curtis P. Wagner Illinois Natural History Survey
Max H. Wolter Illinois Natural History Survey
Corey S. DeBloom Illinois Natural History Survey
Matthew .J Diana Illinois Natural History Survey
Michael J. Weber Iowa State University, [email protected]
See next page for additional authors
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Recommended Citation Wagner, Curtis P.; Wolter, Max H.; DeBloom, Corey S.; Diana, Matthew J.; Weber, Michael J.; and Wahl, David H., "Survival and Growth of Three Geographically Distinct Stocks of Muskellunge Introduced into Midwestern Reservoirs" (2017). Natural Resource Ecology and Management Conference Papers, Posters and Presentations. 27. https://lib.dr.iastate.edu/nrem_conf/27
This Conference Proceeding is brought to you for free and open access by the Natural Resource Ecology and Management at Iowa State University Digital Repository. It has been accepted for inclusion in Natural Resource Ecology and Management Conference Papers, Posters and Presentations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Survival and Growth of Three Geographically Distinct Stocks of Muskellunge Introduced into Midwestern Reservoirs
Abstract Muskellunge Esox masquinongy management programs often rely on stocking to create and maintain populations. In many instances, a native and nearby stocking source is unavailable or a genetically suitable brood source is unclear. Genetic differences among stocks of Muskellunge may influence survival and growth when introduced into novel environments. Consequently, the selection of a suitable brood source can be difficult and possibly critical to the success of Muskellunge stocking programs. We examined differences in long-term survival and growth among introduced Muskellunge stocks from the Ohio and upper Mississippi River drainages and a mixed-origin Illinois broodstock population in three Illinois reservoirs. Catch per unit effort (CPUE) from spring modified-fyke netting suggested that the upper Mississippi River drainage stock at ages 3 and 4 persisted at lower relative abundance compared to conspecifics; however, low lake- and stock- specific catches of older ages precluded robust CPUE comparisons among stocks. Apparent survival, estimated from mark-recapture data with the Cormack-Jolly-Seber open population model, differed among stocks I-year poststocking, with the upper Mississippi River drainage stock exhibiting markedly lower survival compared to conspecifics. Annual variation in survival to age 1.5 was related to water temperature at stocking, fish size at stocking, first winter temperatures, and first summer temperatures. However, survival did not differ among stocks for Muskellunge age 2 and older, indicating that important factors structuring long-term survival exert their effects most strongly in the first year poststocking. Despite overall low survival of Muskellunge from the upper Mississippi River drainage, males that survived exhibited a slight growth advantage compared to conspecifics. No growth advantage was observed for upper Mississippi River drainage stock females. Our findings suggest that stock selection in addition to environmental conditions can influence survival of introduced Muskellunge and subsequent contribution to the fishery.
Disciplines Ecology and Evolutionary Biology | Natural Resources Management and Policy | Terrestrial and Aquatic Ecology
Comments This is a proceeding from Wagner, C, M Diana, M Wolter, C DeBoom, MJ Weber, and DH Wahl. 2017. Survival and growth of three geographically distinct stocks of Muskellunge introduced into Midwestern reservoirs. Pages 437‐465 in KL Kapuscinski, TD Simonson, DP Crane, SJ Kerr, JS Diana, and JM Farrell, editors. Muskellunge management: fifty years of cooperating among anglers, scientists, and fisheries biologists. American Fisheries Society, Symposium 85, Bethesda, Maryland.
Authors Curtis P. Wagner, Max H. Wolter, Corey S. DeBloom, Matthew J. Diana, Michael J. Weber, and David H. Wahl
This conference proceeding is available at Iowa State University Digital Repository: https://lib.dr.iastate.edu/nrem_conf/27 Muskellunge Management: Fifty Years of Cooperation Among Anglers, Scientists, and Fisheries Biologists
Edited By
KEVIN l. KAPUSCINSKI School of Biological Sciences, Lake Superior State University 650 West Easterday Avenue, Sault Ste. Marie, Michigan 49783, USA
TIMOTHY D. SIMONSON Wisconsin Department of Natural Resources 3911 Fish Hatchery Road, Fitchburg, Wisconsin 53711, USA
DEREK P. CRANE Department of Biology, Coastal Carolina University 107 Chanticleer Drive East, Conway, South Carolina 29526, USA
STEVEN J. KERR Ontario Ministry of Natural Resources and Forestry (retired) 264 Clonakilty Line, Ennismore, Ontario KOL 1TO, Canada
JAMES s. DIANA School of Natural Resources and Environment, University of Michigan 440 Church Street, Ann Arbor, Michigan 48109, USA
JOHN M. FAR RELL Department of Environmental and Forest Biology State University of New York College of Environmental Science and Forestry 1 Forestry Drive, 250 Illick Hall, Syracuse, New York 13210, USA
American Fisheries Society Symposium 85
Proceedings of the "Hugh C. Becker Memorial Muskie Symposium" Held in Minnetonka, Minnesota, USA March 13-15, 2016
American Fisheries Society Bethesda, Maryland, uc A 2017 LIBRARY OF THE UNIVERSITY OF WYOMING LARAMIE, 82071 Suggested citation formats follow.
Entire book Kapuscinski, K. L., T. D. Simonson, D. P. Crane, S. ]. Kerr,]. S. Diana, and]. M. Farrell, editors. 2017. Muskellunge management: fifty years of cooperation among anglers, scientists, and fisheries biologists. American Fisheries Society, Symposium 85, Bethesda, Maryland.
Chapter in book Page, K. S., and E. Lewis. 2017. Integrating voluntary angler catch reports with mark-recapture data to model a Muskellunge fishery in Clear Fork Reservoir, Ohio. Pages 75-94 in K. L. Kapuscinski, T. D. Simonson, D. P. Crane, S.]. Kerr,]. S. Diana, and]. M. Farrell, editors. Muskellunge management: fifty years of cooperation among anglers, scientists, and fisheries biologists. American Fisheries Society, Symposium 85, Bethesda, Maryland.
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American Fisheries Society 425 Barlow Place, Suite 110 Bethesda, Maryland 20814 USA American Fisheries Society Symposium 85:437-465, 2017 © 2017 by the American Fisheries Society
Survival and Growth of Three Geographically Distinct Stocks of Muskellunge Introduced into Midwestern Reservoirs
CURTIS P. WAGNER* 1 Illinois Natural History Survey, Kaskaskia Biological Station 1235 County Road lOOON, Sullivan, Illinois 61951, USA and Department ofNatural Resources and Environmental Sciences, University ofIllinois 1816 South Oak Street, Champaign, Illinois 61820, USA
MAx H. WoLTER2 Illinois Natural History Survey, Kaskaskia Biologfral Station 1235 County Road lOOON, Sullivan, Illinois 61951, USA and Department ofNatural Resources and Environmental Sciences, University ofIllinois 1816 South Oak Street, Champaign, Illinois 61820, USA
COREY s. DEBOOM3 Illinois Natural History Survey, Kaskaskia Biological Station 1235 County Road lOOON, Sullivan, Illinois 61951, USA and Department ofNatural Resources and Environmental Sciences, University ofIllinois 1816 South Oak Street, Champaign, Illinois 61820, USA
MATTHEW J. DIANA4 Illinois Natural History Survey, Kaskaskia Biological Station 1235 County Road lOOON, Sullivan, Illinois 61951, USA
' Corresponding author: [email protected]. oh.us 1 Present address: Ohio Department of Natu ral Resources, Division of Wildlife, 912 Portage Lakes Drive, Akron, Ohio 44319, USA 2 Present address: Wisconsin Department ofN at ural Resources, 10220 State Highway 27 South, Hayward, Wisconsin 54843 USA 3 Present address: Indiana Department of Natu ral Resources, Cikana State Fish Hatchery, 2650 State Route 44, Martinsville, Indiana 46151 USA 4 Present address: Michigan Department ofN atu ral Resources, 621 North 10th Street, Plainwell, Michigan 49080 USA 437 438 WAGNER ET AL.
MICHAEL J. WEBER Department ofNatural Resource Ecology and Management, Iowa State University 339 Science Hall IL Ames, Iowa 50011, USA
DAVID H. WAHL Illinois Natural History Survey, Kaskaskia Biological Station 1235 County Road JODON, Sullivan, Illinois 61951, USA and Department ofNatural Resources and Environmental Sciences, University ofIllinois 1816 South Oak Street, Champaign, Illinois 61820, USA
Abstract.-Muskellunge Esox masquinongy management programs often rely on stocking to create and maintain populations. In many instances, a native and nearby stocking source is unavailable or a genetically suitable brood source is un clear. Genetic differences among stocks of Muskellunge may influence survival and growth when introduced into novel environments. Consequently, the selec tion of a suitable brood source can be difficult and possibly critical to the success of Muskellunge stocking programs. We examined differences in long-term sur vival and growth among introduced Muskellunge stocks from the Ohio and upper Mississippi River drainages and a mixed-origin Illinois broodstock population in three Illinois reservoirs. Catch per unit effort (CPUE) from spring modified-fyke netting suggested that the upper Mississippi River drainage stock at ages 3 and 4 persisted at lower relative abundance compared to conspecifics; however, low lake- and stock-specific catches of older ages precluded robust CPUE compari sons among stocks. Apparent survival, estimated from mark-recapture data with the Cormack-Jolly-Seber open population model, differed among stocks I-year poststocking, with the upper Mississippi River drainage stock exhibiting mark edly lower survival compared to conspecifics. Annual variation in survival to age 1.5 was related to water temperature at stocking, fish size at stocking, first winter temperatures, and first summer temperatures. However, survival did not differ among stocks for Muskellunge age 2 and older, indicating that important factors structuring long-term survival exert their effects most strongly in the first year poststocking. Despite overall low survival of Muskellunge from the upper Missis sippi River drainage, males that survived exhibited a slight growth advantage com pared to conspecifics. No growth advantage was observed for upper Mississippi River drainage stock females. Our findings suggest that stock selection in addition to environmental conditions can influence survival of introduced Muskellunge and subsequent contribution to the fishery.
Introduction tant fisheries resources (Maclean and Evans 1981). Many temperate fishes are distributed Understanding phenotypic and life history across a broad latitudinal and geographic variation among individuals and popula range, subjecting them to wide variation in tions within a species is essential for proper environmental conditions. Consequently, a management and conservation of impor- MUSKELLUNGE STOCK DIFFERENCES 439 species group is not panmictic, but is com and shorter growing seasons at high latitudes, prised of many partially or entirely geneti generate selective pressure for increased indi cally isolated, divergent units. A fundamen vidual growth rates (Conover and Schultz tal principal of the stock concept (Berst and 1995; Belk et al. 2005). The countergradient Simon 1981) is that these divergent units, or variation model suggests faster growth and stocks, are specifically adapted to their native improved survival, due to size-dependent ef environmental conditions through natural fects, of fish from more northern populations selection (Mayr 1975; Stearns 1992). As a when placed in southern (i.e., warmer) en consequence of natural selection and adap vironments compared to local conspecifics. tive evolution in geographically distinct en Understanding how the influences of genetic vironments, it is predicted that, when intro history and environmental conditions inter duced outside their native range, stocks will act for important sport fish species can help exhibit differing physiological and behavioral guide management and stocking decisions. responses to new environmental conditions Muskellunge Esox masquinongy are large, that may be maladaptive (Philipp and Whitt piscivorous fish widely distributed through 1991; Cooke et al. 2001). out the north temperate United States and Latitudinal variation in ambient tem Canada. Thought to have persisted through perature and length of the growing season the Wisconsin glacial period in the Mississippi is likely one of the most important envi refugium, the species moved north through ronmental conditions leading to population the Mississippi valley upon glacial recession, differentiation among freshwater fish stocks establishing their current range via the Mis (Fry 1971; Philipp 1992). Two competing sissippi and Ohio River systems as well as models explain the manner that responses through precursors to tributaries of the Great vary across a latitudinal gradient (i.e., among Lakes (Crossman 1978, 1986). Genetic analy stocks). Local adaptation, or cogradient vari ses of various populations have revealed three ation (Conover and Schultz 1995), suggests distinct dusters related to separation by these that genetic influence covaries with environ major river drainages, suggesting the existence mental influence and predicts that growth of divergent stocks (Koppelman and Philipp rates are altered through natural selection in 1986). As Muskellunge were isolated by major concert with the local (i.e., native) tempera river drainages and experienced differing envi ture range (Levinton 1983; Yamahira and ronmental conditions, it is likely that natural Conover 2002). Consequently, reduced sur selection acted on these groups to structure vival and reduced or altered growth would be adaptive physiological and behavioral differ expected when introducing fish to environ ences (Altukhov 1981; Maclean and Evans ments that differ dramatically from their na 1981). The three distinct dusters represent tive waters. Alternatively, the countergradient major regional genetic lineages that we will variation model portrays situations where the refer to as the upper Mississippi River drain genetic influence counters the environmen age stock, the Great Lakes/St. Lawrence River tal influence (Conover and Present 1990; drainage stock, and the Ohio River drainage Yamahira and Conover 2002). Countergra stock (Koppelman and Philipp 1986; Miller dient variation is based on the premise that et al. 2017, this volume). environments that impose strong impedi Muskellunge are highly sought after by ments to growth, such as low temperatures anglers, and the economic and societal value ....
440 WAGNER ET AL. of Muskellunge fisheries is high and contin ferences have been observed in laboratory ues to increase (Hanson 1986; Margenau studies among populations of age-0 Mus 1999; Margenau and Petchenik 2004). Most kellunge (Clapp and Wahl 1996). Although Muskellunge fisheries native to natural lakes these patterns did not conform solely to es occur at low densities (Scott and Crossman tablished genetic groupings, these differenc 1998), and lentic Muskellunge fisheries in es may translate into survival and growth constructed reservoirs rarely support natu differences among Muskellunge stocks in ral reproduction (Ragan et al. 1986; Wahl troduced into a common environment. For 1999). Consequently, Muskellunge fisheries instance, Diana et al. (2017) found differ are frequently supplemented or entirely sup ences in survival I-year poststocking among ported by stocking subadults (Wingate 1986; stocks of Muskellunge in field settings, and Margenau 1992; Szendrey and Wahl 1996; these short-term differences may indicate Wahl 1999). Even as Muskellunge are regu potential for substantial longer-term differ larly stocked into new waters (within and ences in adult survival and growth among outside the native range) to create additional Muskellunge stocks. recreational angling opportunities, certain In locations where native populations wild populations have been and are being either do not exist or have been extirpated, extirpated from their native range (Koppel a suitable brood source for stocking is not man and Philipp 1986; Wingate 1986; Wahl always clear. This management dilemma 1999). The anthropogenic effects on the is often exacerbated throughout the lower Muskellunge range add to the challenge of Midwest where recipient fisheries are typi understanding the suitability of source stocks cally constructed reservoirs and the only for management purposes (Crossman 1986; historical native Muskellunge populations Clapp and Wahl 1996). were riverine. The Illinois Department of Substantial effort has been directed to Natural Resources (IDNR) has historically wards understanding factors influencing used a brood source population established Muskellunge stocking success, including using multiple populations from throughout size of fish and timing of stocking to maxi the native Muskellunge range (multiple up mize survival and growth (Margenau 1992; per Mississippi River and Ohio River drain Johnson and Margenau 1993; Wahl and age sources, S. Krueger, IDNR, personal Stein 1993; Szendrey and Wahl 1996; Wahl communication), and the introgression and 1999) as well as biotic and abiotic sources contribution of individual founding popula of stocking mortality (Carline et al. 1986; tions to a given year's hatchery production is Mather and Wahl 1989; Wahl and Stein unknown. Our objectives were to evaluate 1989; Hanson and Margenau 1992; Szen long-term survival and growth differences drey and Wahl 1995). Comparatively little among two of the major river drainage stocks work has focused on physiological (Clapp of Muskellunge and the Illinois mixed-origin and Wahl 1996; Wagner and Wahl 2007) brood source simultaneously introduced into and behavioral (Wagner and Wahl 2011) reservoirs throughout Illinois using a com differences among populations and stocks mon garden approach. Differences observed of Muskellunge that may be important for were discussed in the context of the cogradi stocking and management programs. Short ent and countergradient theories of adapta term food consumption and growth dif- tion for Muskellunge. MUSKELLUNGE STOCK DIFFERENCES 441 Methods house 1991), tempered to the lake water Muskellunge Sources and Stocking temperature (±2°C), and released at a target density of approximately four fish per surface We evaluated differences in survival and ha (Szendrey and Wahl 1996; Clapp et al. growth among Muskellunge stockings from 1997; Diana et al. 2017). Because markings the upper Mississippi River drainage (Missis were administered very quickly (~ 15 s/ fish, sippi stock [MISS]), the Ohio River drain authors' unpublished data), Muskellunge age (Ohio stock, [OH]), and a mixed-origin were not anesthetized during the marking population (Illinois stock, [IL]) used by the and stocking events. Cohort TL of stocked Illinois Department of Natural Resources as Muskellunge was estimated by measuring a the brood source for their Muskellunge pro random subsample of fish (typically n = 50) gram (Diana et al. 2017). Although Illinois from each stocking event immediately prior fish are not a true genetic stock, we refer to to release. Attempts were made to acquire these fish as Illinois stock here. Each stock Muskellunge :'.::250 mm mean TL (Szendrey was represented by commonly used hatchery and Wahl 1996); however, in approximately sources within their respective major river 30% of the stocking events, Muskellunge ob drainages. Upper Mississippi River drainage tained were slightly smaller than this target Muskellunge were represented solely by the size (Table 1). Mean stocking size across all Leech Lake, Minnesota population, the most lakes and stocks was 263 mm (±6 SE) and, consistently available hatchery-reared source despite considerable among-cohort varia from this drainage. Ohio River drainage tion, was similar among the three stocks (P Muskellunge were represented by multiple = 0.16; 274 mm± 3.3 SE for Illinois, 250 populations, including Lake Chautauqua, mm± 9 SE for Ohio River drainage, and 265 New York; Clear Fork Lake, Ohio; and Cave mm ± 14 SE for Mississippi River drainage Run Lake, Kentucky, depending on avail Muskellunge). ability (Figure 1). All populations evaluated All three stocks were introduced in Pierce in this study are commonly used for agency (61 ha), Mingo (72 ha), and Sam Dale (79 stocking programs throughout the native ha) lakes in Illinois. Study systems were shal range of the species. low, eutrophic reservoirs with Gizzard Shad Muskellunge from all sources were reared Dorosoma cepedianum and Bluegill Lepomis in hatcheries in close proximity to their na macrochirus prey fish communities (Austen et tive population source. Fish were grown to al. 1993). Muskellunge had historically been approximately 100 mm total length (TL) in stocked in Pierce and Mingo lakes, but num raceways before being transferred to earthen bers were very low at the initiation of this ponds and fed Fathead Minnows Pimephales study. Muskellunge from all three stocks were promelas until they were harvested in late first introduced into Mingo Lake in 2002, summer or early fall. Muskellunge were har Pierce Lake in 2003, and Sam Dale Lake in vested from hatchery ponds and transport 2005 (Table 1). The final study stockings ed directly to study lakes where they were were completed in Pierce and Mingo lakes in marked using a stock-specific fin clip (Wagner 2007 and in Sam Dale Lake in 2008 (Table et al. 2009) followed by cauterization of the 1). Effort was made to stock similar length wound, given a stocking-year-specific freeze Muskellunge in each lake at approximately brand as an age mark (Lajeone and Berger- the same water temperatures within a given 442 WAGNER ET AL.
Ohio River drainage • Upper Mississippi River drainage
Figure 1.-The upper Mississippi River and Ohio River drainages forming a large portion of the native Muskellunge range in the United States. Study populations (large black dots) include Leech Lake, Minnesota; Chautauqua Lake, New York; Clear Fork Lake, Ohio; Cave Run Lake, Kentucky; and North Spring Lake, Illinois. Although geographically situated in the upper Mississippi River drainage, the Illinois population is a mixed-origin broodstock con taining genotypes from several major river drainage sources. year; however, logistical constraints of ob A, pulse DC) was conducted on a weekly or taining Muskellunge from across a large geo biweekly interval during the spring (March graphical range resulted in frequent instances April) and fall (October-November) from of differing stocking sizes and water tempera spring 2003 through fall 2011 (years vary tures at the time of stocking (Table 1). by lake; 10.4 ± 7.5 electrofishing hours/lake/ season [mean ± SD]). Electrofishing tran Muskellunge Sampling sects were conducted along a majority of the Muskellunge were sampled using a boat elec lake shoreline and all Muskellunge encoun trofisher and modified fyke nets (Table 2). tered were netted. Although all Muskellunge Nighttime electrofishing (250 V, 4.0-5.0 encountered were collected, electrofishing MUSKELLUNGE STOCK DIFFERENCES 443
Table 1.-Stocking summary of three stocks (IL: Illinois stock, MISS: upper Mississippi River drainage stock, OH: Ohio River drainage stock) of age-0 Muskellunge introduced into Pierce, Mingo, and Sam Dale lakes in Illinois, USA during falls 2002-2008. Total length and weight were measured on a subsample prior to stocking and standard deviations are in pa- rentheses. Total Wet Stocking Stocking length weight density Srock Population date (mm) (g) (#/ha) Pierce Lake IL North Spring Lake, Illinois 08/29/03 257.8 (12.8) 76.7 (11.1) 8.2 MISS Leech Lake, Minnesota 11/07/03 196.7 (17.7) 28.1 (9.0) 1.6 OH Chautauqua Lake, New York 09/19/03 225.4 (13.0) 43.6 (8.4) 3.8 IL North Spring Lake, lllinois 08/26/04 271.9 (16.5) 87.8 (17.8) 4.9 MISS Leech Lake, Minnesota 10/29/04 287.5 (27.8) 96.4 (34.1) 3.3 OH Cave Run Lake, Kentucky 09/14/04 261.4 (17.7) 75.9 (17.8) 4.0 IL North Spring Lake, Illinois 08/31105 270.2 (16.3) 87.1 (17.8) 4.9 MISS Leech Lake, Minnesota 10/10/05 235.2 (18.6) 49.6 (13.6) 2.7 OH Clear Fork Lake, Ohio 09/24/05 261.2 (17.9) 74.7 (16.5) 4.9 IL North Spring Lake, Illinois 08123106 285.5 (16.9) 115.9 (23.6) 5.0 MISS 0.0 OH 0.0 IL North Spring Lake, Illinois 09/13/07 285.0 (13.0) 124.8 (18.8) 4.9 MISS Leech Lake, Minnesota 11/29/07 325.3 (25.5) 153.2 (38.2) 4.1 OH Clear Fork Lake, Ohio 09127107 234.2 (17.0) 54.8 (13.4) 4.3 Mingo Lake IL North Spring Lake, lllinois 10/24/02 335.9 (19.7) 199.6 (41.1) 5.6 MISS 0.0 OH Cave Run Lake, Kentucky 10/30/02 315.2 (20.0) 115.0 (22.0) 2.4 IL North Spring Lake, Illinois 08129103 257.8 (12.8) 76.7 (11.1) 7.0 MISS Leech Lake, Minnesota 10/31 /03 238.1 (45.2) 60.5 (38.8) 4.0 OH Clear Fork Lake, Ohio 09/04/03 226.9 (12.8) 55.6 (11.0) 4.0 IL North Spring Lake, Illinois 08/27/04 273.0 (16.2) 87.9 (18.7) 4.2 MISS Leech Lake, Minnesota 10/30/04 280.3 (29.0) 85.4 (31.0) 2.7 OH Clear Fork Lake, Ohio 09/14/04 260.6 (19.8) 73.6 (18.5) 3.4 IL North Spring Lake, Illinois 08/30/05 266.5 (16.8) 78.9 (20.4) 4.5 MISS Leech Lake, Minnesota 10/11/05 233.3 (23.4) 47.8 (16.2) 2.7 OH Chautauqua Lake, New York 09/28/05 233.9 (13.0) 44.6 (8.0) 2.7 IL North Spring Lake, Illinois 08123106 280.6 (20.4) 112.3 (26.9) 4.2 MISS 0.0 OH Cave Run Lake, Kentucky 08/16/06 244.0 (18.0) 65.6 (20.1) 4.6 444 WAGNER ET AL. Table 1.-Continued. Total Wet Stocking Stocking length weight density Stock Population date (mm) (g) (#/ha) IL North Spring Lake, Illinois 09/13/07 285.8 (11.6) 125.8 (11.6) 4.2 MISS Leech Lake, Minnesota 11/30/07 325.7 (26.9) 155.1 (40.6) 3.8 OH Cave Run Lake, Kentucky 08/02107 230.9 (12.5) 54.4 (8.8) 5.5 Sam Dale Lake IL North Spring Lake, Illinois 08/31/05 272.5 (14.3) 87.6 (18.2) 3.8 MISS Leech Lake, Minnesota 11/16/05 254.9 (22.1) 57.3 (18.4) 2.4 OH Clear Fork Lake, Ohio 09/23/05 261.2 (17.9) 74.7 (16.5) 3.9 IL North Spring Lake, Illinois 08/23/06 278.1 (19 .2) 105.8 (26.8) 3.9 MISS 0.0 OH 0.0 IL North Spring Lake, Illinois 09/13/07 284.3 (12.5) 123.7 (17.9) 3.8 MISS Leech Lake, Minnesota 11/30/07 325.4 (26.7) 156.3 (40.3) 3.3 OH Clear Fork Lake, Ohio 09127107 232.3 (16.2) 53.5 (12.8) 4.1 IL North Spring Lake, Illinois 08/24/08 290 (20.9) 119 (28.5) 3.8 MISS Leech Lake, Minnesota 11/19/08 217(19.5) 40 (11.5) 3.3 OH Cave Run Lake, Kentucky 11/18/08 338 (26.3) 174 (51.2) 2.5 surveys targeted and predominately captured previously estimated ages for recaptured fish. immature fish (ages 0-2). Mature Muskel Captured Muskellunge were scanned for the lunge (generally ages 3+) were sampled with presence of a passive integrated transponder modified fyke nets (3.8-cm bar mesh, 1.2 x (passive integrated transponder [PIT tag]) 1.8 m frames, six 0.75-m hoops) in Pierce and all individuals :::age 1.5 (fish that have and Mingo lakes beginning in spring 2006 been in the reservoir for at least 1 year) that and in spring 2010 in Sam Dale Lake and did not already have a tag were anesthetized were used through spring 2012 in all systems and implanted in the peritoneal cavity with (75.6 ± 75.9 net-nights/lake/spring [mean± a uniquely numbered PIT tag (Wagner et SD]). Nets were deployed during a 2-4-week al. 2007). All sampled Muskellunge were re period each spring when surface water tem turned into the respective reservoir. peratures were between 7 .0°C and 1 l .0°C Catch-per-Unit-Effort Analysis and were checked daily between 0800 and 1200 hours Spring modified fyke net CPUE was used Muskellunge were measured for TL to evaluate relative abundance differences (mm) and weighed (g) and examined for among stocks for Muskellunge age 3 through stock-specific fin clips and freeze-brand age age 7 (the oldest age that allowed for a com marks. Scales were taken from all fish to pletely balanced design across stocks, lakes, confirm age marks or estimate age when age and ages). An adjusted CPUE, corrected for marks were undetectable and also to validate differences in initial stocking numbers (num- MUSKELLUNGE STOCK DIFFERENCES 445
Table 2.-Mean electrofishing (EF) and modified-fyke netting (NET) effort per year tar- geted by age-class of three stocks of Muskellunge introduced into Pierce, Mingo, and Sam Dale Lakes, Illinois during 2002-2008. Total number of Muskellunge is reported by stock for all years targeted. IL= Illinois stock; MISS - upper Mississippi River drainage stock; OH= Ohio River drainage stock. Mean Mean electrofishing netting effort effort Total number of fish Lake Age-class (h) (net-nights) IL MISS OH Pierce Age 1 16 0 33 37 26 Age2 14 23 8 0 2 Age3 0 27 82 2 18 Age4 0 40 149 2 28 Age 5+ 0 37 137 3 61
Mingo Age 1 17 0 166 71 113 Age2 14 58 77 2 53 Age3 11 66 110 2 67 Age4 8 90 85 1 51 Age 5+ 3 90 48 4 35
Sam Dale Age 1 7 0 1 0 2 Age2 5 70 27 1 14 Age3 0 142 65 5 39 Age4 0 185 31 1 20 Age 5+ 0 116 2 0 3 ber captured/net-night/number stocked x al. 2011), a robust mark-recapture model 1,000), for each age-class was calculated and ing approach was employed to obtain esti differences among stock-adjusted CPUEs mates of apparent survival rates (~) using were assessed using a repeated measures individual 0.5-year live-encounter histories. analysis of variance model (Proc Mixed, SAS Individual Muskellunge-encounter histories System) with lake as a random variable and were analyzed in Program MARK (White stocking event as the subject. Tukey's mean and Burnham 1999) using the live-capture separation procedure was used to test for sig Cormack-Jolly-Seber open population nificant differences at P:::; 0.05. model (Cormack 1964; Jolly 1965; Seber 1965) to generate maximum-likelihood es Capture-Recapture Survival Analysis timates of apparent survival ( ~J: conditional Because Muskellunge frequently occur at probability of surviving interval j provided low densities and catch rates can be low the individual is alive and available for re and affected by numerous sources of sam capture during the interval, meaning fish pling variation (Schoenebeck and Hansen emigration cannot be separated from mor 2005; Younk and Pereira 2007; Jennings et talities; hereafter, referred to as "survival") 446 WAGNER ET AL. and detection probability (p. : conditional provide a surrogate for water temperatures in J probability of recapture in year j, provided lakes (Livingstone and Lotter 1998; Sharma the individual is alive; White and Burnham et al. 2008). Further, air temperature was a 1999). The model assumptions include strong predictor of water temperature (1 m tagged individuals are representative of the depth) across lakes when examining available population to which inference is made, water temperature data in this study (R 2 = number of individuals tagged is known, 0.85, P < 0.0001, unpublished data). tagging does not affect survival, releases and Age-based models were constructed that recaptures are made within short time pe allowed Muskellunge (that were all stocked riods (2 months here) relative to the time as age 0.5 during first fall) to transition and between tagging (6 months), recapture does have differential survival to ages 1.5 (first time not affect subsequent survival or recapture, individual recapture histories were recorded), fates of individuals within and among co 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0, 5.5, 6.0, 6.5, horts are independent, and individuals in a 7.0, 7.5, and 8.0. Due to a large number cohort have the same survival and recapture of possible model structures for each of the probability for each time interval (Burnham survival and detection parameters, running et al. 1987). every possible model combination was im We developed a set of a priori hypoth practical. Instead, we ran a set of candidate eses to evaluate factors that may influence models whereby the model complexity with apparent survival and detection of Muskel in the apparent survival parameter (variation lunge. In addition to the main parameter of among lakes and stocks from age 1.5 to age stock, other parameters that may affect Mus 8.0) was used in all models while the effects kellunge survival or detection probability of lake, stock, age, time, and sampling effort include lake (Pierce, Mingo, or Sam Dale), (trap-net nights and electrofishing minutes) cohort stocking length (mean TL of a Mus on detection were evaluated (Doherty et al. kellunge stock by year and lake), and stock 2012). After evaluating model structures of ing temperature (lake water temperature on interest for detection, the most supported stocking date; Szendrey and Wahl 1996; model structure for detection was retained Wahl 1999; Diana et al. 2017). To account and held constant when evaluating various for the potential effects of winter and sum survival model combinations. To evaluate mer temperature variation among lakes and survival, we started by comparing which age years, potentially accounting for variation in structure was most appropriate while main stock-specific apparent survival, winter se taining differences in survival among lakes verity (the number of days air temperature and stocks. After identifying the age-struc never exceeded 0°C during the first winter ture with the most model support, we com poststocking; October-March) and summer pared the effects of Muskellunge stock and severity (the 90th percentile of the individual lake on survival for each age-class. Finally, we daily maximum air temperatures during the added single and multiple environmental co first summer poststocking; April-September) variates additively (i.e., relationship between were included as potential covariates. Water environmental covariate and survival is the temperatures were not available for all years same among stocks) and as an interaction ef and lakes for this study; however; air tem fect of stock (i.e., relationship between envi peratures have been shown to predict and ronmental covariate and survival has separate MUSKELLUNGE STOCK DIFFERENCES 447 intercept and slope for each stock) to account assignments from prior capture events. In for variation in survival from stocking to age the absence of a PIT tag recapture history, 1.5 among stocking events. the presence and location of the freeze brand Competing hypotheses were stated in provided the assigned age when the estimated model form in Program MARK using the log scale age was ± 1 year of that indicated by the it link function and compared using Akaike's freeze brand. Low numbers of fish were dis information criterion corrected for small sam carded from analyses (<5% of all recaptured ple size (AI Cc; Burnham and Anderson 1998) Muskellunge) when no PIT tag recapture his to determine the most supported model (low tory existed, freeze brands were unidentifiable, est AIC). The change in AI Cc (MIC) was freeze brand age and scale age estimate had calculated as the AfCc of the model with the greater than ±1 year discrepancy, or, last, mul smallest AICc value minus the AICc of a given tiple readers could not independently reach model. Akaike weights (W:) were also calcu- consensus from scale aging in the absence of lated to address potential uncertainty concern a PIT tag recapture history and identifiable ing the selection of the top model (Burnham freeze brand. Fish from all three study lakes and Anderson 1998). The Bayesian paradigm were pooled to compensate for the low in using Markov chain Monte Carlo was used to stances of capture for upper Mississippi River obtain estimates of process variances and co drainage fish. Data were stratified by sex with variances (White et al. 2009). immature fish (age 1 and age 2) included in both male and female data sets. Sex-stratified Growth Analysis models (nonlinear least squares) were built von Bertalanffy growth parameters (L"', K, to test if van Bertalanffy growth parameters t ; differed among stocks using likelihood ra and 0 Beverton and Holt 1957) were esti mated for each stock using the maximum tio tests (Kimura 1980) within the "fish likelihood method. The average asymptotic methods" package in program R. If stock length of fish from that stock is represented specific differences among parameters were
, detected, pairwise comparisons of param by L00 Kis a growth coefficient that describes the rate at which the stock approaches as eters between stocks were made. Significant differences were declared at P < 0.05. ymptotic length, and t0 is a time coefficient at which length is theoretically 0. Growth parameters, with specific interest in L"', were Results compared to assess differences in growth and Catch-per-unit-effort analysis maximum size among stocks. Only fish cap tured in spring (February through May) via Adjusted CPUE from spring modified-fyke electrofishing or modified fyke netting and nets differed among stocks across ages (Fig ure 2; F , = 2.82, P = 0.006). Relative with a reliable age estimate were used in these 8 150 comparisons. Age estimates were considered abundance of age-3 and age-4 Muskellunge reliable when there was consensus among scale from the Illinois stock was significantly high age, presence and location of freeze brand, and er than the upper Mississippi River drainage PIT tag recapture history (if present). When stock (P < 0.001 age 3, P = 0.001 age 4). complete consensus among aging methods Catch rates of the Ohio River drainage stock did not occur, PIT tag recapture history was were intermediate but not statistically dif first used to examine the reliability of the age ferent from the other two stocks (P 2': 0.13 448 WAGNER ET AL.
1.6 --. 0 c:J IL 0 0 c=i MISS 'C""" 1.4 i< -OH "'O (1) ~u 1.2 ..,..,0 (/) :;t: ".;::J 1.0 .r::. .2> c ..,..,I 0.8 (1) c -~ 0.6 w :'.) a.. (_) 0.4 "'O ..,..,(1) (/) :J 0.2 :0 <( 0.0 3 4 5 6 7 Age (years)
Figure 2.-Age-specific catch per unit effort (CPUE), adjusted to correct for different stocking numbers, for three stocks of Muskellunge from spring modified-fyke nets following introduction in Pierce, Mingo, and Sam Dale lakes, Illinois. Cohorts were treated as repeated subjects and lake was specified as a random factor in the analysis of variance model. Error bars represent ±1 standard error. IL= Illinois stock; MISS - upper Mississippi River drainage stock; OH = Ohio River drainage stock. age 3; P ?_ 0.17 age 4). No age-specific dif that there were differences in detection of ferences in relative abundance among stocks Muskellunge among lakes and among ages were detected for ages 5, 6, and 7 (Figure 2; to age 8. Less complex models with fewer P?. 0.05). Low capture numbers of fish older age-classes and more complex models that than age 4 (Table 2) resulted in high varia included effects of Muskellunge stock and tion relative to the adjusted CPUE estimates sampling effort were not well supported and consequently low power to ascribe sig (MICc> 100, W: = O), indicating that these nificance to any differences. parameters had little effect on P. Overall, detection probability was low (< 0.1 O) but Capture-Recapture Survival Analysis tended to increase through age 6 before de Fifty-seven models were compared to evalu clining again at older ages (Figure 3). Detec ate the effects of stock, lake, age, and envi tion also tended to be similar among lakes ronmental covariates on Muskellunge and until age 5 when Muskellunge in Pierce P. Models comparing P structure indicated Lake tended to have higher detection prob- MUSKELLUNGE STOCK DIFFERENCES 449 0.6 .....------. - Pierce 0.5 c::::::J Mingo s c:::::J Sam Dale ~ :a 0.4 ro .0 ~ 0.3 c: 0 u 0.2 ~ 0 0.1
1 2 3 4 5 6 7 8 Muskellunge age (years)
Figure 3.-Estimated detection probability (P; ±95% confidence interval) of Muskellunge in Pierce (black), Mingo (white), and Sam Dale (gray) lakes from age 1.5 through age 8. Note that the maximum age of Muskellunge in Sam Dale Lake was age 6 for the data incorporated into the Program MARK analysis. Whole number ages represent spring sampling and 0.5- year age intervals represent fall sampling. ability compared to fish in Mingo and Sam of stocks to age 1.5 was higher for the Illinois Dale lakes. stock (cj> = 0.53, 95% CI = 0.36-0.69) com Retaining the most supported P model pared to the Ohio River drainage stock (cj> = structure, multiple age structure comparisons 0.24, 95% CI = 0.16-0.33) and the upper indicated that cj> to age 1.5 (first sampling Mississippi River drainage stock (cj> = 0.03, interval) was different than cj> for fish >age 95% CI = 0.01-0.06) in Pierce Lake (Figure 2, which were similar to one another. Mod 4). In contrast, cj> was similar between Illinois els with more complex age structure received and Ohio River drainage stocks but both of little support (MICc > 50, W: = O). Overall, these stocks had higher cj> than the upper Mis Muskellunge cj> to age 1.5 regardless of lake sissippi River drainage stock in Mingo Lake or stock was 0.23 (95% confidence interval (IL: cj> = 0.31, 95% CI = 0.24-0.39; MISS: cj> [CI]: 0.20-0.27), whereas cj> >age 2 was 0.88 = 0.02, 95% CI = 0.01-0.05; OH: cj> = 0.23, (95% CI: 0.84-0.92). However, this model 95% CI = 0.18-0.30) and Sam Dale Lake (IL: received no support among candidate models cj> = 0.22, 95% CI = 0.12-0.34; MISS: cj> = (MICc> 580, W: = O). The most supported 0.03, 95% CI = 0.01-0.06; OH: cj> = 0.20, model that did not include environmental 95% CI = 0.11-0.33; Figure 4). Illinois stock covariates indicated that cj> to age 1.5 varied cj> was higher in Pierce Lake compared to Sam among lakes and stocks, whereas cj> >age 2 Dale Lake, but 95% confidence intervals for was different among stocks but similar among cj> overlapped for all other stock comparisons lakes (Table 3; model 11). Apparent survival among lakes. Combined across lakes, average Table 3.-Cormack-Jolly-Seber open population models used to estimate apparent survival (
Mingo, and Sam Dale lakes in Illinois, USA during falls 2002-2008. The top 18 models (based on AICc [Akaike's information criterion corrected for small sample size] and W; [Akaike weights] model selection criteria) are shown for comparison. Effects included Lake, Muskellunge stock (Stock), water temperature at stocking (Stocking Temp), 90th percentile of the daily maximum air temperature during the first summer poststocking (Summer Temp), number of days air temperatures did not exceed 0°C during the first winter poststocking (Winter Temp), and cohort mean length at stocking (Length). K = number of parameters. Deviance= -2 . log-likelihood of the model less-2 ·log-likelihood of the saturated model (same number of parameters and degrees of freedom). Model Model AIC LlAIC w likelihood K Deviance c c t
Pierce Mingo Sam Dale
1.0 ~2 years old
--...... ~ 0.8 ro > ·~ :::l 0.6 U') ...... c: ~ ro 0.4 a.. a.. <( 0.2
0.0 IL MISS OH
Figure 4.-Estimated apparent survival (
$to age 1.5 for Illinois Muskellunge was 0.35 CI: 0.84-0.92) and 95% Cis overlapped for (95% CI: 0.29-0.40), for upper Mississippi all stocks (Figure 4). River drainage Muskellunge was 0.02 (95% Models that included environmental co CI: 0.01-0.04), and for Ohio River drainage variates were well supported (Table 3; top 10 Muskellunge was 0.20 (95% CI: 0.16-0.24, models; only model where W:: > 0), indicating Table 3, model 18). Beyond age 1.5, of all that they were useful in explaining variation in stocks >2 years old was high (
1.0 ,------,..rr----, 1.0 ,------r.----~ A 0 c 0 o IL ~ 0.8 ~ 0.8 • MISS 0 f} § 0
1.0 ,------n-~-----~ 1.0 ,------n----, B 0 D
~ 0.8 ~ 0.8 T O cP 0 0 0 ~ ·~ 0.6 1 0.6 :::J 0 :::J 0 VI 0 Figure 5.-Estimated apparent survival ( Water temperature at stocking also had Survivorship curves, assuming an m1- a large effect on first-interval 300 Pierce Lake -- IL ...... MISS 250 OH ~ --- 'l ~ 200 ~, ~\ 150 ~\ ~\ ~ , 100 ~ , \ \ 50 ~ ' ... (f) ~. -...... "- ~ ------~--~-· 0 0 .•••·••········••······ .2:! 2 3 4 5 6 7 300 c Mingo Lake IL :J ••••••• MISS (f) 250 --- OH '+-- 0 200 "- (].) .c 150 E :J c: 100 -0 50 (].) t5 0 ····•········· -0 2 3 4 5 6 7 (].) 300 "- Sam Dale Lake IL a.. MISS 250 --- OH 200 150 100 50 0 ··············•·•··• ... 2 3 4 5 6 7 Age (years) Figure 6.-Predicted survivorship curves representing the estimated number of Mus· kellunge surviving to each modeled age increment following hypothetical stockings of300 individuals from the Illinois stock (solid lines), upper Mississippi River drainage (dotted lines), and Ohio River drainage (dashed lines) introduced into Pierce, Mingo, and Sam Dale lakes us· ing estimates derived from Program MARK analyses. MUSKELLUNGE STOCK DIFFERENCES 455 Table 4.-Sex-stratified von Bertalanffy growth parameters for three stocks of Muskel lunge stocked into Pierce, Mingo, and Sam Dale lakes during falls 2002-2008. Letters indi cate statistically significant differencess of P < 0.05. Cl =confidence interval. Von Bertalanffy parameters (95% CI) Sex Stock Linr K to Male Illinois 915 (±20) )' 0.55 (±0.07) -0.05 (±0.18) )' Mississippi 992(±116) z 0.53 (±0.22) -0.48 (±0.40) z Ohio 925 (±25) zy 0.62 (±0.1 O) -0.31 (±0.23) z Female Illinois 1,030 (±36) 0.47 (±0.08) y -0.09 (±0.28) x Mississipppi 965 (±84) 0.81 (±0.31) z -0.51 (±0.21) z Ohio 1,024 (±35) 0.52 (±0.07) y -0.24 (±0.14) y on average by age 6, longer than Ohio River Mississippi River drainage females were longer drainage (898 mm TL) and Illinois (883 mm at age 3 (836 mm mean TL) than Illinois fe TL) male estimates (Figure 7). There were males (789 mm TL) and Ohio River drainage no differences in K values among the three females (780 mm TL). The growth advantage stocks (P ~ 0.28). Upper Mississippi drain of the upper Mississippi River drainage fe age males and Ohio River drainage males males was no longer present at age 6 (953 mm t to both exhibited 0 values that were statistically mean TL) compared Illinois (971 mm TL) similar (P = 0.37), but both were significant and Ohio (973 mm TL) females. ly higher than the value for Illinois males (P < 0.01 and P = 0.02, respectively). Discussion The main effects model for female Mus In his seminal introduction to the first in kellunge detected significant differences in ternational Muskellunge symposium, Cross von Bertalanffy growth parameters associ man (1986) stressed the need for research ated with stock (df = 664, P < 0.01). There directed towards understanding physiologi were no observed differences in L for females "' cal, behavioral, and performance differences, among the three stocks (P ~ 0.17; Figure 7). or "uniqueness," among genetically distinct Upper Mississippi drainage females showed a populations and stocks of Muskellunge. Pre significantly higher K value than both Illinois vious work has documented survival and females (P = 0.01) and Ohio River drainage growth differences among Muskellunge pop females (P = 0.03). There was no difference ulations within a relatively small geographic in K values between Illinois and Ohio River region of Minnesota and Wisconsin (Younk drainage females (P = 0.34). Upper Missis and Strand 1992; Margenau and Hanson sippi River drainage females demonstrated a 1996; Miller et al. 2009). Our findings sug t value that was significantly higher than both 0 gest that differences observed among popula Illinois (P< 0.01) and Ohio River drainage fe tions in relatively close proximity can scale to males (P= 0.04). Ohio River drainage females differences among stocks from distant sourc also had a significantly higher t value than Il 0 es when introduced into common environ linois females (P = 0.03). Based on van Ber ments. Low first-year poststocking survival talanffy growth curves for each stock, upper of upper Mississippi River drainage Muskel- Figure 7.-Fitted von Bertalanffy growth functions for male (top panel) and female (bot tom panel) spring-captured Muskellunge from the lllinoi stock (solid lines), upper Mississippi River drainage (dotted lines), and Ohio River drainage (dashed lines) pooled across Pierce, Mingo, and Sam Dale lakes. lunge was the primary among-stock survival ability to conduct robust individual growth difference we observed. For older ages (2:age rate assessments. However, von Bertalanffy 2), modified-Fyke net CPUE and apparent growth models were able to be constructed survival estimates suggested that age-specific for all stocks pooled across the three study survival among stocks did not differ. The lakes. Upper Mississippi River drainage fe considerably lower survival of upper Missis males exhibited a faster rate of growth (KJ ap sippi River drainage Muskellunge limited our proaching the maximum average length (L) MUSKELLUNGE STOCK DIFFERENCES 457 compared to conspecifics; however, this did ferences among stocks emerged (Diana et not translate into differing among stocks. L00 al. 20 I 7). In our work, winter severity had In contrast, there was some indication of a a weak positive effect and summer severity higher maximum average length for upper a weak negative effect on apparent survival Mississippi River drainage males. The ob estimates across stocks, suggesting that cold served growth differences among stocks were winters may improve I-year poststocking small, suggesting that genetic origin (stock) survival while especially hot summers impair most strongly affects subadult survival with survival I year following stocking. Account some growth differences expressed among re ing for covariates in our models, including sultant survivors into adult ages. mean length at stocking, stocking water tem Survival to 1 year poststocking (age 1.5), perature and seasonal severities, allowed for the first apparent survival interval able to be more precise estimates of stocking-specific estimated, was significantly different among apparent survival. stocks. Muskellunge from the upper Missis The Cormack-Jolly-Seber model does sippi River drainage stock exhibited lower not provide estimates of actual survival, but apparent survival (2%) compared to the Il rather apparent survival, an estimate that as linois (35%) and Ohio River drainage (20%) sumes that the animal is alive and remains in stockings during the first year in study res the study area and thus available for recap ervoirs. Poststocking survival (1-3 months ture. Muskellunge have been documented to after stocking) of fall fingerlings can be vari exhibit significant emigration from lakes via able but is often less than 40% (Hanson et escapement through dam structures (O.I3- al. 1986b; Margenau I992; Margenau and 0.25 annual escapement probability; Weiss Hanson 1996) and is positively related to to 2009; Wolter et al. 20 I 3; Page and Lewis tal length at stocking (Margenau I 992; Szen 20 I 7, this volume). Estimates of apparent drey and Wahl 1996; Wahl I 999) and nega survival in our study are likely low as a re tive related to water temperature at stocking sult of unknown emigration likely occurring (Wahl 1999). In agreement with earlier work, without the ability to return to the lake. How mean length at stocking had a large positive ever, differences in apparent survival and rela effect and stocking water temperature a large tive CPUE (Diana et al. 20 I 7) among stocks negative effect on I -year poststocking surviv were documented only for subadults, the life al in our study. Evaluation of initial stocking stage less likely to emigrate through dams success and first-year survival of these same (Wolter et al. 2013), suggesting that dam stocks using electrofishing sampling (Diana escapement did not have a significant influ et al. 2017) showed that the upper Mississip ence on the observed among-stock survival pi River drainage stock consistently exhibited differences to age 1.5. Muskellunge from dis lower relative abundance than conspecifics tinct stocks could differ in their probability the fall following stocking (age I .5) despite of emigration via dam escapement, but few the three stocks having similar electrofish differences in movement rates, home ranges, ing CPUE the spring immediately following and habitat selection among subadults from stocking (age I). Among-stock CPUE differ these same stocks were observed in an Illi ences suggest that it was during the first sum nois reservoir (Wagner and Wahl 2011). As a mer period, not the short-term poststocking result, it is unlikely that emigration through or first-winter periods, when survival dif- dam structures contributed to the estimated 458 WAGNER ET AL. lower apparent survival of upper Mississippi concluded that the Leech Lake population, River drainage Muskellunge at the early ages the same upper Mississippi River drainage observed in our study. population used in our study, consistently Muskellunge older than age 1.5 exhib exhibited superior growth characteristics ited no differences in survival among stocks in two Minnesota lakes (Younk and Strand for the remainder of ages examined. Appar 1992). In contrast, assessments of growth ent survival estimates were similar (88%) for differences among native Wisconsin popu all ages and stocks beyond age 1.5 for every lations and the Leech Lake population in 6-month interval modeled (77% for calcu six northern Wisconsin lakes could not as lated annual survival). Due to the charac sess growth of Leech Lake Muskellunge due teristically low catch rates and longevity of to low sample sizes, presumably due to low Muskellunge, obtaining adult survival rates survival of Leech Lake fish (Margenau and is difficult and sparsely reported in the litera Hanson 1996). Our study compared Leech ture. Apparent survival estimates for stocks Lake Muskellunge to other stocks in Illinois examined in these Illinois study lakes are lakes and found few growth differences. Al within the range of 6 month (96.3% winter, though upper Mississippi River drainage 98.7% summer, Frohnauer et al. 2007) and males exhibited significantly longer maxi annual survival (62-71 %, Page and Lewis mum average length (('-') compared to con 2017) estimates in the literature and suggest specifics, no differences in L were observed 00 that survival is most influenced at the age- among stocks for females. Because the larg 0 life stage to age 1.5 (Szendrey and Wahl est individuals in a Muskellunge population 1996; Wahl 1999). Despite similar among are typically female, the trophy potential of stock adult survival rates, drastic survival a fishery is judged by the growth trajectory, differences during the first year poststocking or growth potential, of females (Casselman result in different numbers of Muskellunge and Crossman 1986; Casselman 2007; Faust from each stock in the adult, fishable popu et al. 2015). Consequently, the lackoffemale lation. For example, based on stock-specific growth differences, specifically maximum av apparent survival estimates, by age 5 there is erage length, among stocks observed in this a predicted 9: 1 ratio of Ohio River drainage study suggests that source populations are to upper Mississippi River drainage Muskel not a primary determinant of growth poten lunge and an 11: 1 ratio of Illinois stock to tial for introduced Muskellunge populations upper Mississippi River drainage Muskel in Midwestern reservoirs. lunge in the adult population across study A common garden experiment is a gen lakes. Similar adult survival rates among eral approach to explore survival and growth stocks does not mitigate the drastic differ responses of stocks from across a latitu ences observed in survival among stocks at dinal gradient and to evaluate cogradient the subadult stage. and countergradient patterns of latitudinal The quality of a Muskellunge fishery to variation (Clausen et al. 1940; Conover and anglers is based on the occurrence oflarge in Schultz 1997). Common garden designs are dividuals (Casselman et al. 1999; Isermann often difficult to achieve with fish, as in our et al. 2011). Comparisons of growth among study. Muskellunge were raised near their native Minnesota populations and nearby source locations to approximately age 0.5 Wisconsin populations in an agency report rather than in a common environment. As a MUSKELLUNGE STOCK DIFFERENCES 459 result, early environmental differences, ma should not be stocked in locations distant ternal effects, and transportation effects may from the region of origin in an attempt to have contributed to potential among-stock obtain larger maximum size. Consequently, differences in addition to genetic differences. Muskellunge from the Ohio River drainage However, we included body length and wa stock are more suitable for management pur ter temperature at stocking as covariates in poses than fishes from the upper Mississippi survival models. Results were also consistent River drainage stock in lower Midwestern over multiple years of stocking, and survival waters, including Illinois. Stocking is a prom differences did not become evident until the inent practice in Muskellunge management summer following stocking, not immediately (Wahl 1999; Wingate and Younk 2007), and following stocking (Diana et al. 2017), sug maintaining the genetic integrity of conspe gesting a genetic component to survival dif cific~ must be considered when introducing ferences. Muskellunge (Hanson et al. 1986a; Koppel Our findings support the cogradient man and Philipp 1986; Philipp et al. 1993). (i.e., local adaptation) model of physiologi When Muskellunge are introduced into wa cal responses for Muskellunge. Although few ters in which a native population exists, the growth differences were observed among same population should ideally be used as a stocks, low survival of the upper Mississippi brood source to avoid outbreeding depres River drainage stock compared to conspe sion and the breakdown of coadapted gene cifics suggests maladapted physiological re complexes (Dobzhansky 1948; Templeton sponses of this stock of Muskellunge to the 1986). Muskellunge are also introduced into thermal regimes experienced in the lower reservoirs in previously uninhabited water Midwestern study lakes, especially at the sub sheds to create new fisheries. Under these adult life stage. Apparent survival estimates circumstances, knowledge of population were similar among stocks from age 1.5 and differentiation may be useful for planning older and growth parameters varied little, stocking programs. indicating that subadult physiological pro cesses are likely the most locally adapted and Acknowledgments least plastic. For subadults, the first summer We thank the personnel of the Kaskaskia following stocking is when most the differen and Sam Parr Biological Stations, includ tial among-stock mortality occurred (Diana ing B. Alger, M. Anderson, M. Baldock, W et al. 2017). It is possible that subadult upper Bauer, J. Butler, J. Clark, R. Damstra, T. Mississippi River drainage Muskellunge were Edison, L. Einfalt, J. English, L. Freeman, not able to acclimate to the warmer summers I E. Giebelstein, J. Godbout, M. Harrington, experienced in the study lakes, compared A. Larsen, K. Mann, J. Maxwell, J. Mulhol with their native climate, resulting in higher lem, M. Nannini, K. Ostrand, P. Port, C. mortality than conspecifics. Salzmann, D. Schermerhorn, K. Schnake, Management Implications.-lntroduc E. Smolik, and J. Wisher, for field assis ing populations or stocks that maximize sur tance and S. Dinsmore for assistance with vival and growth in new waters increases the survival models. We are indebted to the chances of creating a successful Muskellunge Illinois Department of Natural Resources fishery. Our findings suggest that Muskel (IDNR) Jake Wolf Memorial Fish Hatchery lunge are locally (thermally) adapted and staff, especially T. Hayes and S. Krueger, for 460 WAGNER ET AL. providing Muskellunge. We also thank M. of the international stock concept sympo Hearn and the Kentucky Department of sium. Canadian Journal of Fisheries and Fish and Wildlife, E. Heyob and J. Navarro Aquatic Sciences 38. and the Ohio Department of Natural Re Beverton, R. J. H., and S. ]. Holt. 1957. On sources, P. Hulbert and the New York State the dynamics of exploited fish populations. Department of Environmental Conserva Great Britain Ministry of Agriculture, tion, and R. Johannes and the Minnesota Fisheries and Food, Fishery Investigation Department of Natural Resources for pro Series 2, volume 19. viding fingerling Muskellunge. Funding was Burnham, K. P., and D. A. Anderson. 1998. Model selection and inference. Springer provided by Federal Aid in Sport Fish Res Verlag, New York. toration project F-151-R administered by Burnham, K. P., D.R. Anderson, G. C. White, the IDNR. L. Dunham, S. Pallo, M. Con C. Brownie, and K. H. Pollock. 1987. De lin, and S. Stuewe helped coordinate activi sign and analysis methods for fish survival ties with the Division of Fisheries, IDNR. experiments based on release-recapture. The Illinois Muskie Alliance and Muskies, American Fisheries Society, Monograph 5, Inc., at both the international level and lo Bethesda, Maryland. cal chapters, provided additional funding Carline, R. F., R. A. Stein, and L. M. Riley. for the study. In particular, the Central Illi 1986. Effects of size at stocking, season, nois Muskies Hunters, Chicagoland Muskie Largemouth Bass predation, and forage Hunters, Flatlanders, and Quad County abundance on survival of tiger muskel Hawg Hunters chapters provided support. lunge. Pages 151-167 in G. E. Hall, edi tor. Managing muskies: a treatise on the References biology and propagation of Muskellunge Altukhov, Y. P. 1981. The stock concept from in North America. American Fisheries the viewpoint of population genetics. Ca Society, Special Publication 15, Bethesda, nadian Journal of Fisheries and Aquatic Maryland. Sciences 38:1523-1538. Casselman, J. M. 2007. Determining mini Austen, D. J., J. T. Petersen, B. 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