Use of otolith chemistry to assess recruitment and habitat use of a white bass fishery in a Nebraska reservoir

Figures & data

Figure 1. Map of Lake McConaughy with designated upper and main sections of the reservoir based on physicochemical differences.

Figure 2. Visualizing differences (NMDS plot) among natal groups using ¹³⁸Ba:⁴³Ca, ²⁴Mg:⁴³Ca, ⁵⁵Mn:⁴³Ca, ⁸⁶Sr:⁴³Ca, and ⁸⁸Sr:⁴³Ca with hatchery fish (n = 17) in red, upward-facing triangles, McConaughy natal group 1 (n = 74) in green boxes, and McConaughy natal group 2 (n = 26) in blue, downward-facing triangles (with 95% confidence interval [CI] ellipses). Arrows represent underlying element:⁴³Ca ratio differences (strength and direction).

Figure 3. Differences in ²⁴Mg:⁴³Ca, ⁵⁵Mn:⁴³Ca, ¹³⁸Ba:⁴³Ca, ⁸⁶Sr:⁴³Ca, and ⁸⁸Sr:⁴³Ca (from the otolith core) among 2 Lake McConaughy white bass natal groups (derived from cluster analysis) and hatchery fish. Differences assessed using a PERMANOVA and asterisks denote significant differences among groups (hatchery versus McConaughy natal groups) for each element:⁴³Ca ratio.

Table 1. Predicted natal group assignment and accuracy (%) of white bass fingerlings collected from the North Platte Fish hatchery and age-0 white bass collected from Lake McConaughy (derived from cluster analysis) using otolith core ratios of ¹³⁸Ba:⁴³Ca, ²⁴Mg:⁴³Ca, ⁵⁵Mn:⁴³Ca, ⁸⁶Sr:⁴³Ca, and ⁸⁸Sr:⁴³Ca. We used 75% of the data to train the Random Forest model and used the remaining 25% of the data to measure the percent classification accuracy. Bold text indicates the number of fish and percentage (in parentheses) that were correctly assigned to their respective natal group.

Natal group	Number of fish	Predicted Lake McConaughy (natal group 1)	Predicted Lake McConaughy (natal group 2)	Predicted hatchery
Lake McConaughy (natal group 1)	18	17 (94%)	1 (6%)	0 (0%)
Lake McConaughy (natal group 2)	6	0 (0%)	5 (83%)	1 (17%)
Hatchery	6	0 (0%)	2 (33%)	4 (66%)

Figure 4. Differences in ²⁴Mg:⁴³Ca, ⁵⁵Mn:⁴³Ca, ¹³⁸Ba:⁴³Ca, ⁸⁶Sr:⁴³Ca, and ⁸⁸Sr:⁴³Ca (from the otolith edge) between juvenile white bass collected from 2 sections of Lake McConaughy, Nebraska. Differences assessed using a PERMANOVA and asterisks denote significant differences between groups (upper versus main reservoir) for each element:⁴³Ca ratio.

Table 2. Predicted lake section assignment and accuracy (%) of fish collected from the upper and main sections of Lake McConaughy using white bass otolith edge ratios of ²⁴Mg:⁴³Ca, ⁵⁵Mn:⁴³Ca, ¹³⁸Ba:⁴³Ca, and ⁸⁶Sr:⁴³Ca. We used 75% of the data to train the Random Forest model and used the remaining 25% of the data to measure the percent classification accuracy. Bold text indicates the number of fish and percentage (in parentheses) that were correctly assigned to their respective lake section.

Lake section	Number of fish	Predicted main section	Predicted upper section
Main	9	9 (100%)	0 (0%)
Upper	16	4 (25%)	12 (75%)