Precision of Three Structures for Saugeye Age Estimation

Koch, Jeff D.; Neely, Ben C.; Sowards, Bryan

doi:10.1080/02755947.2017.1394938

Cited by 3 publications

(5 citation statements)

References 18 publications

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“…Because saugeye used in those studies were not of known age, they could not report on ageing accuracy. We determined that a single annulus formed in otoliths of juvenile saugeye, which is likely why precision was so high in recent investigations (Koch et al., ; Porta et al., ), and that these estimates may reflect accurate ages.…”

Section: Discussionmentioning

confidence: 99%

“…However, it still is necessary to either perform marginal increment analysis for multiple age classes over several years, use known age fish or use a chemical stamp to validate annulus formation in older fish (Buckmeier, Sakaris, et al., ; Buckmeier, Snow, et al., ; Campana, ). In two recent investigations of saugeye ageing precision, both studies identified the importance of sacrificing fish for otoliths to obtain precise age estimates, as otoliths were more precise than scales or dorsal spines (Koch, Neely, & Sowards, ; Porta et al., ). Because saugeye used in those studies were not of known age, they could not report on ageing accuracy.…”

Section: Discussionmentioning

confidence: 99%

“…Koch et al. () reported substantial bias between readers when estimating dorsal spine ages for juvenile saugeye. In our study, we believe the second annulus (false annulus) formed during August when water temperatures were at their highest, and as a direct result of saugeye seeking deeper, cooler areas of the reservoir to persist in thermal refugia during these hot periods.…”

Section: Discussionmentioning

confidence: 99%

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Otolith annulus validation and variables influencing false annuli formation in dorsal spines of saugeye

2018

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Marginal increment analysis is a common technique for validating formation of a single annual growth ring on an ageing structure. False annuli can form on ageing structures when environmental variables affect growth of a fish, potentially resulting in age estimation bias. Therefore, validating ageing structures is essential to ensure that accurate and precise age estimates are collected when assessing fish population dynamics. Saugeye (Sander vitreus, [Mitchill, 1818]) and S. Canadensis, [Griffith and Smith, 1834]) are highly valued sport fish that are stocked across the Midwest United States. Using marginal increment analysis, we confirmed that a single annulus was formed yearly in otoliths of juvenile saugeye, however two annuli formed in dorsal spines in a single year. Timing of the first annulus formation in both otoliths and dorsal spines was completed after a slow growth period during winter (otoliths forming in April; dorsal spines forming in March). The second annulus (false annulus) that formed during August in dorsal spines did not form in otoliths. To understand what environmental factors may influence the false annulus to form, we collected monthly water temperatures and percent empty stomachs of juvenile saugeye. The highest water temperatures of the year occur during July and August, which resulted in saugeye seeking thermal refuge and affecting feeding habits. Mean monthly temperature and percent empty stomachs were positively correlated, so during times of high temperatures foraging rates declined, suggesting the formation of false annulus on dorsal spines of juvenile saugeye. This study demonstrates how thermal stress affected accuracy of non‐lethal aging structures and further emphasizes the need for age validation studies prior to using non‐lethal ageing structures to estimate age for a particular species from different aquatic systems.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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Otolith annulus validation and variables influencing false annuli formation in dorsal spines of saugeye

2018

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“…In this instance, sectioned otolith age was significantly greater than corresponding ages of whole otoliths, suggesting difficulty in distinguishing the focus from the first annulus. Identification of the innermost annulus has also been an issue in other studies (Isermann et al 2003;Dembkowski et al 2017;Koch et al 2018) and Hales and Belk (1982) suggested that identification of the first annulus was problematic in Bluegills from a southeastern thermal reservoir because of inconsistent appearance of the otolith focus. We sampled the fish in our study in September, so age-0 fish exhibited no annuli.…”

Section: Discussionmentioning

confidence: 99%

Comparison of Sectioned and Whole Otoliths for Estimating Bluegill Age

Koch

Neely

Chance-Ossowski

2019

Journal of Fish and Wildlife Management

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Three readers independently assigned ages to 257 paired sectioned and whole Bluegill Lepomis macrochirus otoliths to examine between-reader precision of age estimates and to compare estimates obtained using the two otolith preparation methods. Percent exact between-reader agreement varied from 93.4% to 96.9% for sectioned otoliths and 92.2% to 94.2% for whole otoliths. Mean coefficient of variation values for between-reader comparisons were < 5.0% for all reader combinations and both otolith preparation methods. Exact agreement between paired whole and sectioned otoliths varied by reader from 82.8% to 85.2%; whereas coefficient of variation values ranged from 7.8% to 8.9%. The only significant departure from a 1:1 relationship for mean age estimates between the two preparation methods occurred for young fish in the estimates of one reader. This bias was not pervasive, as no significant bias was indicated in older fish. Our results suggest that age estimates obtained from sectioned and whole Bluegill otoliths are precise and the time and associated expense of mounting and sectioning Bluegill otoliths may not be necessary as whole otolith ages were generally concordant with sectioned ages to age 8 y.

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“…Moreover, differences in between-reader estimates may be linked to reader familiarity with structure types, experience, and limitations caused by using digital media. Age-precision studies have infrequently quantified reader's experience, often stating "experienced readers were used," "readers had several years of experience," or previous experience was not mentioned (Stolarski and Hartman 2008;Spiegel et al 2010;Herbst and Marsden 2011;Erhardt and Scarnecchia 2013;Koch et al 2018). Moreover, few studies clarify reader's past experience by structure type.…”

Section: Age Estimation In Brook Troutmentioning

confidence: 99%

Investigating Nonlethal Age Estimation in a Lentic Brook Trout Population

Taylor

Cross

Moore

2019

N American J Fish Manag

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Routine lethal sampling on small, conservation, or threatened populations may be unsustainable. Therefore, determining if alternative, nonlethal structures can provide accurate age data is important. We evaluated nonlethal structures (scales and pectoral fin rays) in conjunction with otoliths collected from lentic Brook Trout Salvelinus fontinalis in Washington State. We used age‐bias plots, percent agreement, and coefficient of variation to determine how scale or fin ray age estimates compared with otolith estimates, which had been validated in a previous study. Prior experience with aging specific structure types was the primary variable affecting age agreement with validated otolith‐determined age among three age readers. In general, fin rays and scales did not consistently reflect otolith age. Between‐structure coefficient of variation was 17.8–19.1% for scales and fin rays, and between‐structure percent agreement (within 1 year) was 80–82%. Individual percent agreement within 1 year was highest (92% and 86% for fin rays and scales, respectively) and coefficient of variation was lowest (9.0% and 14.8%, respectively) for the most experienced reader. Agreement of age estimates between readers improved with experience aging specific structures. Our study suggests that otolith data remains the preferred option.

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Precision of Three Structures for Saugeye Age Estimation

Cited by 3 publications

References 18 publications

Otolith annulus validation and variables influencing false annuli formation in dorsal spines of saugeye

Otolith annulus validation and variables influencing false annuli formation in dorsal spines of saugeye

Comparison of Sectioned and Whole Otoliths for Estimating Bluegill Age

Investigating Nonlethal Age Estimation in a Lentic Brook Trout Population

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