Adaptive stocking strategies of Hybrid Striped Bass in a Nebraska reservoir impacted by White Perch

Abstract

Branched Oak Reservoir is the largest reservoir in eastern Nebraska and provides an important recreational fishery to large urban centers including Omaha and Lincoln. Hybrid Striped Bass Morone saxatilis × Morone chrysops are an important component of the recreational fishery, but this population appears to have been negatively impacted following the introduction and subsequent overabundance of invasive White Perch Morone americana in the mid-1990s. This study analyzed long-term standardized sampling and stocking data from Branched Oak Reservoir to evaluate Hybrid Striped Bass stocking strategies in the presence of White Perch. The spring age-0 stocking era from 1988 to 1997 consisted largely of fry and fingerling stockings. From 1998 to 2015, stockings were adapted to advanced fall age-0s with mean ± SE TL of 146 ± 7 mm. From 2016 to 2019, advanced spring age-1 Hybrid Striped Bass defined the third stocking era with mean ± SE TL of 178 ± 13 mm. Age-1 Hybrid Striped Bass CPUE differed among stocking eras (KW = 9.81, P = 0.007) as mean ± SE CPUE_age-1 was 2 ± 1 fish per net night during the spring age-0 era, 1 ± 1 fish per net night during the fall age-0 era, and 3 ± 1 per net night during the spring age-1 era. Hybrid Striped Bass CPUE_QP was different among eras (KW = 13.30, P = 0.001). None of the five abiotic factors assessed exhibited significant relationships to Hybrid Striped Bass CPUE_age-1, and the strongest relationship (spring temperature) only had an r² value of 0.046. Information obtained from this study validates the current management decision to stock spring age-1 Hybrid Striped Bass based on the present White Perch abundances, and observed recruitment of Hybrid Striped Bass.

Keywords:

• Adaptive
• Hybrid Striped Bass
• Nebraska
• stocking
• recruitment
• White Perch
• wiper

Introduction

Adaptive strategies allow for flexibility to adjust management techniques and decisions as research and standardized data collection describe changing trends (Halbert 1993; Marttunen and Vehanen 2004; Cinner et al. 2009). Specifically, long-term standardized sampling data of managed fisheries allow managers to see trends and adapt strategies to achieve management objectives. One management technique that is readily utilized and often adapted to achieve management goals is fish stocking (Boxrucker 1986; Moore et al. 1991; Cowx 1994; Perrion et al. 2020). Varying the size, number, density, location, or timing of fish stockings can overcome recruitment bottlenecks within a fishery impacted by inter- and intraspecific competition or changing biotic and abiotic conditions (Miller et al. 1988; Dauwalter and Jackson 2005; Kaemingk et al. 2014).

Adaptive management strategies are often required as a result of changes in competition or predation. Stocking of predatory species has been used to take advantage of and potentially control overabundant, stunted prey species ( Irwin et al. 2003; Vrtiska et al. 2003; Denlinger et al. 2006; Wamboldt et al. 2020). Stocking strategies have also been adapted to overcome reduced natural recruitment and increased predation (Fayram et al. 2005; Grausgruber and Weber 2020). For example, stocking programs for Walleye Sander vitreus, Hybrid Striped Bass Morone saxatilis × Morone chrysops, and White Bass M. chrysops were implemented in Lake McConaughy, Nebraska following population declines attributed to competition following the introduction of Alewife (Porath et al. 2003; Schall et al. 2019; Perrion et al. 2020).Stocking strategies may also require adaptation following the introduction of an invasive species (Mercado-Silva et al. 2007; Feiner et al. 2013).

The size of stocked fish and other seasonal abiotic factors can influence stocking success. Fish size at stocking may be a large contributor to stocking success; generally larger fish have higher survival rates (Szendrey and Wahl 1996; Sutton and Ney 2001; Grausgruber and Weber 2020). Other studies have shown seasonal trends related to predator-prey relationships may be important to successful recruitment (Garvey et al. 1998; Zweifel et al. 2009). Stocking density (Fielder 1992) and stocking locations (Wilson 2004) have also been correlated to stocking success. Stocking success and recruitment is often influenced by a myriad of abiotic factors as well within aquatic ecosystems including water temperature and water level changes (Santucci and Wahl 1993; Hoxmeier et al. 2006; Hansen et al. 2015; DeBoer and Pope 2016).

The Nebraska Game and Parks Commission (NGPC) has widely stocked Hybrid Striped Bass due to their trophy potential by a means of fast growth, aggressive behavior, and sporting qualities (Schultz et al. 2013). Hybrid Striped Bass do not naturally reproduce in Nebraska waters (Lueckenhoff 2011), allowing populations to be directly managed by stocking and regulations. Hybrid Striped Bass stocking strategies have been adapted in Branched Oak reservoir following declines in relative abundance which were generally attributed to competition with overabundant invasive White Perch Morone americana. White Perch are known to overpopulate and stunt in freshwater ecosystems (Scott and Crossman 1973), and they can have negative impacts on existing fish communities by direct predation on fish eggs (Schaeffer and Margraf 1987) and larvae and competition for zooplankton and macroinvertebrates (Ballinger and Peters 1978; Hodkin 2001; Weis 2005; Couture and Watzin 2008; Gosch et al. 2010). Reduced juvenile survival of another Moronidae species, White Bass, was observed in conjunction with increasing White Perch abundance in Lake Erie (Madenjian et al. 2000). This study analyzed long-term standardized sampling and stocking data sets among three stocking strategy eras from Branched Oak Reservoir to improve our understanding of Hybrid Striped Bass stocking successes and failures. Stocking strategies included spring age-0 stockings (1988-1997), fall age-0 stockings (1998-2015), and spring age-1 stockings (2016-present). The objectives of this study were to (1) describe adaptive stocking strategies employed by NGPC, (2) assess age-1 relative abundance (CPUE_age-1) and quality to preferred length (CPUE_QP) abundance of Hybrid Striped Bass among stocking eras, (3) describe White Perch population abundances amid Hybrid Striped Bass stocking eras, and (4) analyze abiotic factors influencing Hybrid Striped Bass abundances in Branched Oak Reservoir.

Materials and methods

Study site

Branched Oak Reservoir is the largest reservoir in eastern Nebraska at 728 surface hectares and provides an important recreational fishery to large urban centers such as Omaha and Lincoln, Nebraska (Vrtiska et al. 2003). Hybrid Striped Bass, Channel Catfish Ictalurus punctatus, White Crappie Pomoxis annularis, and Walleye are among the sportfish in Branched Oak Reservoir (Vrtiska et al. 2003). White Perch were first documented in Branched Oak Reservoir in 1988 and became overabundant and stunted beginning in the mid-1990s (Jackson 1999). The impacts of the White Perch introduction in Branched Oak Reservoir became apparent in 1994 as the number of young of the year Walleye sampled showed a significant decline, Gizzard Shad Dorosoma cepedianum CPUE declined, and Gizzard Shad size structure increased reducing the presence of forage size Gizzard Shad for sport fish predation (Jackson 1999). In 2000, a catch and release regulation was implemented on Hybrid Striped Bass at Branched Oak Reservoir with the intent of increasing predatory pressure on the high-density White Perch population (Jackson 1999; Chizinski et al. 2010).

Data collection

Hybrid Striped Bass were collected in the fall during NGPC standardized gill net surveys from 1988 to 2019. Monofilament gill nets were 45.7 m long and 1.8 m deep and composed of six, 7.6 m long panels with bar mesh sizes of 19.1, 25.4, 31.8, 38.1, 50.8, and 76.2 mm (Zuerlein and Taylor 1985). Gill nets were set perpendicular to shore in stratified random locations in Branched Oak Reservoir for 24 hrs. Captured Hybrid Striped Bass and were enumerated, measured for TL (mm), and aging structures were removed for age estimation.

White Perch were collected during the fall NGPC standardized surveys from 1989 to 2019 using standardized 24 hr frame net sets. Frame nets were composed of two 0.9 by 1.4 m frames, two throats with 23.7 and 12.7 cm openings, 15.9 mm square mesh, and a 15.2 m lead (Zuerlein and Taylor 1985). Nets were set at standardized shoreline locations throughout the reservoir. All collected White Perch were enumerated and measured (TL; mm). White Perch mean annual CPUE was calculated from standardized fall fyke net sampling. Historical Hybrid Striped Bass stocking information was summarized from the NGPC stocking database which included stocking year, stocking season, number of stocked fish, size of stocked fish, and stocking density (fish/ha).

Hybrid Striped Bass age data from Branched Oak Reservoir was derived using scales from 1989-2002. Scales have been shown to provide unbiased age data for young Moronidae (Soupir et al. 1997; Schultz et al. 2013). Five scale samples were taken per 10 mm length group during standardized sampling. In 2019, sagittal otoliths were extracted for aging since otoliths have been shown to provide the least biased aging data for Moronidae species (Welch et al. 1993; Soupir et al. 1997). Otoliths were prepared and read using similar methodology to Isermann et al. (2003). Otolith sections were then photographed for reader viewing using TC Capture Software® and a Motic® 2300 live imaging module camera. Otolith sections were independently aged by two different readers (Quist et al. 2012). Age-length keys were used to assign ages to unaged fish in each annual sample from 1990 to 2002, and 2019.

Mean annual catch per unit effort (CPUE) of Hybrid Striped Bass ≥160 mm was calculated, as fish of this size have effectively recruited to the sampling gear (Shoup and Ryswyk 2016). Given that aging data was not available every year, recruitment was evaluated by calculating the mean annual CPUE within one SD of the mean length at capture at age-1 from all aged Hybrid Striped Bass. We considered a conservative approach to defining age-1 Hybrid Striped Bass CPUE in the absence of annual aging data. To evaluate stocking contribution to the fishery, mean annual CPUE of proportional size distribution quality (410 mm) to preferred (510 mm) length (PSD Q-P) (Guy et al. 2007; Dumont and Neely 2011) fish was calculated.

Statistical analysis

Hybrid Striped Bass and White Perch CPUE were assessed in relation to three Hybrid Striped Bass stocking eras in Branched Oak Reservoir. Stocking eras were defined by spring age-0 stockings from 1988 to 1997, fall age-0 stockings from 1998 to 2015, and spring age-1 stockings from 2016 to 2019. Hybrid Striped Bass CPUE_age-1 and CPUE_QP were each compared among the three stocking eras. To group annual CPUEs into eras, CPUE_age-1 of Hybrid Striped Bass was evaluated from each stocking year: spring age-0 era (1989 to 1998), fall age-0 era (1999 to 2014), and spring age-1 era (2016-2019). Years 1988, 2010, 2013, and 2015 were excluded from CPUE_age-1 analysis as no stocking occurred one year prior to sampling (i.e., no age-1 fish in the reservoir). Eras were defined for CPUE_QP as occurring 2-3 years post-stocking as fish in the PSD Q-P size range were 2 and 3 years old. Years excluded in the analysis of CPUE_QP include 1988 and 1989 since no stockings were made 2 to 3 years prior to these samples being collected (i.e., no PSD Q-P length fish in the reservoir). Since Hybrid Striped Bass are not fertile hybrids, excluding years void of stocked fish for age-1 comparisons and 2 to 3 years (i.e., PSD Q-P length) was warranted as no fish of those respective ages were present in the reservoir (i.e., no natural reproduction).

Hybrid Striped Bass CPUE_age-1 and CPUE_QP were each tested for normality using a Shapiro-Wilk’s test. Data could not be transformed to meet assumptions of normality, so nonparametric Kruskal-Wallis tests were used to compare CPUEs among eras. A post-hoc Dunn’s multiple comparison test with a Bonferroni P-value adjustment was used to evaluate differences among the stocking eras in CPUE_age-1 and CPUE_QP length fish following significant Kruskal-Wallis results. Decision probability was set a priori at α = 0.05 for all significance tests, and all statistical testing was conducted using Program R (R Core Team 2018).

White Perch CPUE was divided into three periods: establishment (1989-1996), peak (1997-2013), and recent (2014-2019) population eras that instigated adaptive stocking decisions of Hybrid Striped Bass. Mean annual White Perch CPUE was log10 transformed to meet assumptions of normality. An analysis of variance was used to compare mean CPUE among the three periods described above. A post-hoc Tukey’s Honest Significance Difference test was used to identify significance between periods. Comparisons of White Perch size structure was made by comparing proportional size distribution (PSD) values among White Perch eras. To calculate PSD, the number of quality-length (200 mm) White Perch was divided by the number of stock-length (130 mm) fish and multiplied by 100 (Gabelhouse 1984). Data could not be transformed to meet assumptions of normality, so a Kruskal-Wallis test was used with a post-hoc, Bonferroni-corrected Dunn’s multiple comparison test to determine significance among White Perch abundance periods.

Linear regression relationships were modeled to determine potential factors influencing Hybrid Striped Bass abundances. Mean annual CPUE_age-1 was plotted against mean annual White Perch CPUE, mean spring water temperatures, mean spring inflow, mean spring elevation, mean fall elevation, and mean summer water temperature. Mean spring temperatures was indexed as the average water temperature (°C) at 0.5 m depth in May. Mean spring inflow was indexed as the average water inflow in cubic feet per second (cfs) from the months of March to May. Mean spring elevation was indexed as the average reservoir elevation (m) from the months of March to May, while mean fall elevation was indexed from September and October. Mean summer temperature was indexed as the average water temperature (°C) at 0.5 m depth in July. All reservoir water data (i.e., temperature, inflow, elevation) was obtained from the United States Army Corps of Engineers (USACE 2020) and selected based on biological importance.

Results

Since 1988, approximately 4.1 million Hybrid Striped Bass have been stocked in Branched Oak Reservoir (Table 1). The spring age-0 stocking era from 1988 to 1997 consisted largely of fry and fingerling stockings in the late spring and early summer with stocking densities variable based on the stocking size: 922 to 1,059/ha for fry and 1 to 14/ha for fingerling stockings. Multiple stocking events occurred in 1995 and 1996, including stockings of 4,850 and 5,450 age-1 fish with a mean TL range of 152-178 mm. From 1998 to 2015, stockings were adapted to advanced fall age-0 fish as the White Perch abundances increased in the mid-to-late 1990s (Figure 1). Mean ± SE TL of fall age-0 stocked Hybrid Striped Bass was 146 ± 7 mm. Mean ± SE stocking densities of fall age-0 fish were 11 ± 17 fish/ha with a range of 1 to 52 fish/ha. From 2016 to 2019, advanced spring age-1 Hybrid Striped Bass defined the third stocking era with mean ± SE TL of 178 ± 13 mm. Spring age-1 stocking densities ranged from 1 to 3 fish/ha with a mean ± SE of 2 ± 1 fish/ha (Table 1).

Figure 1. Catch per net night of age-1 and PSD Q-P Hybrid Striped Bass collected in fall gill nets (top) and White Perch collected in fall fyke nets (bottom) in Branched Oak Reservoir from 1988 to 2019 with associated standard error bars. Dotted lines separate stocking eras of spring age-0 (1988-1997), fall age-0 (1998-2015), and spring age-1 (2016-2019) Hybrid Striped Bass (top) and establishment (1989-1996), peak (1997-2013), and recent (2014-2019) periods of White Perch invasion (bottom).

Table 1. Stocking era, year, number of fish stocked, mean TL of stocked fish, and stocking density (fish/ha) of Hybrid Striped Bass in Branched Oak Reservoir, Nebraska, 1988-2019. Asterisks denote years with multiple stocking events.

Era	Year	Number stocked	Mean TL (mm)	Stocking density (fish/ha)
Spring age-0	1988	1,660,000	Fry	922.2
	1989	1,000	32	0.6
	1990	1,765,000	Fry	980.6
	1991	25,000	25	13.9
	1992	1,906,000	Fry	1,058.9
	1993	17,860	76	9.9
	1994	18,030	89	10
	1995	22,850	76	2.7 − 10*
	1996	17,688	76	1.9 − 4.9*
	1997	17,250	79	9.6
Fall age-0	1998	18,000	140	10
	1999	32,625	122	18.1
	2000	87,050	135	48.4
	2001	92,835	135	51.6
	2002	13,992	168	7.8
	2003	2,573	178	1.4
	2004	1,890	127	1.1
	2005	3,000	109	1.7
	2006	3,106	178	1.7
	2007	1,468	203	0.8
	2008	3,900	147	2.2
	2009
	2010	7,365	137	4.1
	2011	8,500	127	4.7
	2012
	2013	6,895	137	3.8
	2014
	2015
Spring age-1	2016	3,988	197	2.2
	2017	980	203	0.5
	2018	5,200	160	2.9
	2019	2,693	152	1.5

Total length at capture with mean ± SD of age-1 Hybrid Striped Bass was 310 ± 60 mm (n = 125). Therefore, evaluation of CPUE_age-1 included fish ranging in length from 275 to 389 mm. Mean ± SD TLs at capture of age-2 and age-3 Hybrid Striped Bass were 415 ± 45 mm (n = 44) and 475 ± 65 mm (n = 29), approximately corresponding to the PSD Q-P length range.

Differences in Hybrid Striped Bass relative abundance were observed among stocking eras (Figure 2). Hybrid Striped Bass CPUE_age-1 differed among stocking eras (KW = 9.8, P = 0.007). The CPUE_age-1 in the fall age-0 era was lower than in the spring age-1 era (Z = 3.1, P = 0.005) but CPUE_age-1 was similar between the spring age-0 and fall age-0 eras (Z = 1.1, P = 0.806) and the spring age-0 and spring age-1 eras (Z = 2.3, P = 0.057) (Figure 2). Hybrid Striped Bass CPUE_QP differed among eras (KW = 13.3, P = 0.001). Hybrid Striped Bass CPUE_QP was lower in the fall age-0 era than in the spring age-0 (Z = 2.8, P = 0.013) and spring age-1 (Z = 3.0, P = 0.008) eras, but spring age-0 and spring age-1 eras did not exhibit differences in CPUE_QP (Z = 1.2, P = 0.694).

Figure 2. Catch per net night of PSD Q-P (top) and age-1 (bottom) Hybrid Striped Bass collected with fall gill nets during fall age-0, spring age-0, and spring age-1 stocking eras at Branched Oak Reservoir. Letters above plots denote significant differences among eras.

The relative abundance of White Perch in Branched Oak Reservoir differed during the study timeline. White Perch mean ± SE CPUE in the establishment, peak, and recent periods were 9 ± 2, 221 ± 78, and 21 ± 5 fish per net night (Figure 1) and significantly differed (F_{2, 28} = 12.33, P < 0.001). Mean CPUE during the peak period was greater than the establishment (P < 0.001) and recent (P = 0.023) periods, but no difference was observed between establishment and recent periods (P = 0.415; Figure 1).

Differences were observed in White Perch PSD values between periods (KW = 8.84, P = 0.012). Mean ± SE PSD values for the establishment, peak, and recent periods were 20 ± 12, 1 ± 1, and 7 ± 2. The lower CPUE years tended to correspond with higher PSD values. The establishment period had a greater PSD value than the peak period (P = 0.038). The recent era had similar PSD values to the peak (P = 0.790) and establishment periods (P = 0.313).

Hybrid Striped Bass CPUE_age-1 exhibited weak linear relationships when compared to abiotic variables occurring in Branched Oak Reservoir during the study timeframe. None of the five abiotic factors assessed exhibited significant relationships to Hybrid Striped Bass CPUE_age-1, and the strongest relationship (spring temperature) only had an r² value of 0.046 (Figure 3). Hybrid Striped Bass CPUE_age-1 plotted against White Perch CPUE also showed a lack of linear relationship, but as White Perch CPUE increased to 125 fish or greater; Hybrid Striped Bass CPUE_age-1 did not exceed 0.3 fish per net night (Figure 3).

Figure 3. Linear regressions of age-1 Hybrid Striped Bass catch per net night from fall gill nets plotted against White Perch CPUE, spring inflow (cfs), spring elevation (m), fall elevation (m), spring water temperature (°C), and summer water temperature (°C). Associated r² and P-values included for relationship description.

Discussion

The adaptive stocking strategies of Hybrid Striped Bass employed at Branched Oak Reservoir to increase CPUE_age-1 and CPUE_QP were developed to offset perceived negative effects of invasive White Perch. Fall age-0 stockings were largely unsuccessful, but spring age-1 Hybrid Striped Bass stocking provided recruitment as White Perch relative abundance declined and size structure increased. Stocking advanced age-1 Hybrid Striped Bass in the spring at large sizes allowed the fish to overcome several potential recruitment bottlenecks created by White Perch. Specifically, White Perch predate on larval fish (Gosch et al. 2010) and compete for prey resources (i.e., zooplankton and macroinvertebrates) prior to Hybrid Striped Bass becoming piscivorous once obtaining 100 mm TL (Ballinger and Peters 1978; Gilliland and Clady 1984; Chervinski et al. 1989; Hodkin 2001; Perrion 2016). While many state agencies stock fry and fingerling Hybrid Striped Bass, the age-1 Hybrid Striped Bass stocked in Branched Oak Reservoir were among the largest in the published literature (Ostrand et al. 2001; Hoffman et al. 2013) and may provide a model for managers looking to improve stocking success in the face of invasive species.

Spring age-1 stockings produced higher CPUE_age-1 in fall surveys than fall age-0s and appeared to be more effective than spring age-0 stockings, although these were not statistically different. The timing of the spring age-1 stockings may have a larger impact on recruitment than the size of the fish (Ludsin and DeVries 1997; Garvey et al. 1998), specially to capitalize on the seasonal timeframe of prey abundances (Zweifel et al. 2009; Sutton et al. 2013). Hybrid Striped Bass stocked as fall age-0 and spring age-1 are likely to have reached a similar life-history state based on size including similar diets, predator avoidance, and habitat selection. For instance, an abundance of age-0 clupeid prey has been related to successful recruitment of Striped Bass Morone saxatilis (Sutton and Ney 2001). Managers may consider the seasonal timeframe of prey abundances in order to stock Hybrid Striped Bass at the opportune time.

The production diet of stocked spring age-1 stockings of Hybrid Striped Bass may have influenced recruitment as well. The spring age-1 stockings were fed a diet of Fathead Minnows Pimephales promelas once reaching approximately 100 mm total length, while fall age-0 Hybrid Striped Bass were pellet-reared. Live prey feeding in production settings can have positive impacts on stocked fish performance by promoting piscivory, prey capture efficiencies, competitive ability, and decreased naiveté to increase survival of spring age-1 stocked fish (Pouder et al. 2010; Rachels et al. 2012). A paucity of information exists surrounding the effects a live fish diet may have on Hybrid Striped Bass production and post-stocking survival, warranting additional research. Additional research elucidating these mechanisms would help improve management and production practices if a live fish diet improved survival and recruitment.

Low relative abundance of Q-P length Hybrid Striped Bass during the fall age-0 stocking era corresponded with high White Perch catch rates and low White Perch PSD values. Catch of Q-P length Hybrid Striped Bass should coincide with recruitment to the fishery about 2-3 years post-stocking, based on length at age at capture estimates. This lack of PSD Q-P length fish during the fall age-0 era indicates a lack of recruitment and a decline in the Hybrid Striped Bass fishery despite advanced age-0 stockings. White Perch have been linked to reduced recruitment of other Moronidae species (Madenjian et al. 2000), and the increased competition may have exacerbated the seasonal effect of limited forage and resulted in increased overwinter mortality (Ludsin and DeVries 1997; Sutton and Ney 2001) of juvenile Hybrid Striped Bass in Branched Oak Reservoir.

Abiotic factors exhibited little relationship to Hybrid Striped Bass CPUE_age-1 in this study. Although other variables not evaluated in this study may have had an influence on the stocking success of Hybrid Striped Bass, the results may demonstrate a density-dependent relationship between White Perch on Hybrid Striped Bass recruitment and survival. As White Perch CPUE increased (e.g., >125), Hybrid Striped Bass CPUE_age-1 declined, suggesting that a potential biological threshold exists, and establishing Hybrid Striped Bass may be unlikely when White Perch CPUE exceed 125 per net night.

Results of this study can aid fishery managers and hatchery personnel also experiencing recruitment bottlenecks related to competitive interactions, specifically an introduction of an invasive species. Our findings suggest that continued stocking of advanced spring age-1 Hybrid Striped Bass is warranted as relative abundance was higher than with advanced fall age-0 stockings. Although analysis of spring age-1 stockings was limited to four years, recent success in recruitment of age-1 and PSD Q-P length Hybrid Striped Bass suggests that these stockings may be most appropriate in Branched Oak Reservoir. Observed patterns of Hybrid Striped Bass relative abundance could not be explained by the abiotic factors included in this study. Future studies could explore additional mechanisms including genetics, overwinter prey abundances, and fine-scale habitat features and characteristics for further evaluation. Continued monitoring will be necessary to determine if spring age-1 Hybrid Striped Bass stockings continue to provide recruitment in Branched Oak Reservoir. Fisheries managers experiencing recruitment failure of stocked fish in the presence of overabundant competitors will need to determine if the benefit associated with raising fish to advanced age-1 size is worth the expense to provide higher recruitment in their system.

Acknowledgements

We want to thank Bryan Sweet and Dirk Higgins from the North Platte Fish Hatchery for insight into Hybrid Striped Bass production and propagation. Zach Horstman and Joseph Spooner also deserve our gratitude for assistance with sampling and aging analysis. We thank Mark Kaemingk for review of draft versions of this manuscript.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This project was funded by the Nebraska Game and Parks Commission through Federal Aid in Sport Fish Restoration, Project F-87-R.