No 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 ¼ 9.81, P ¼ 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 ¼ 13.30, P ¼ 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 r 2 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.

Chemical batch marks with compounds such as oxytetracycline hydrochloride (OTC) can be useful for estimates of stock contribution. However, no information currently exists on the feasibility of marking fingerling White Bass Morone chrysops with OTC. The objectives of this study were to determine the level of mortality on White Bass when immersed in solutions of OTC at 0, 350, and 500 mg/L at intervals up to 96 h postimmersion and to assess the quality of marks on sagittal otoliths 14 d postmarking. A total of 900 White Bass (29–41 mm) were utilized with 100 fish used in three replicates per treatment. No differences in mortality rates were detected among control and treatment groups up to 96 h postmarking. Cumulative mortality rates were ≤6.7%. Mark visibility was ranked on a scale of 0–3; mean mark score was higher in the 500‐mg/L treatment (2.5) than the 350‐mg/L treatment (2.0). Batch‐marking fingerling White Bass using the 500‐mg/L marking solution provided visible marks and low mortality rates and therefore represents a viable option for biologists seeking to assess stock contribution and year‐class strength.