A Comparison of Techniques Using Dorsal Spines to Estimate Sauger Age

Williamson, Craig W.; Dirnberger, Ryan R.

doi:10.1577/m09-140.1

Cited by 5 publications

(13 citation statements)

References 10 publications

(25 reference statements)

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“…Reader agreement rates in this study associated with standardized unsectioned Walleye dorsal spines (37%) were not as high as those observed with sectioned spines (51%) nor were they better than those of any other study that used sectioned spine-based techniques to estimate the age of Walleye Campbell and Babaluk 1979;Olson 1980;Erickson 1983;Isermann et al 2003). In addition, our standardized unsectioned dorsal spine reader agreement rates were much lower than those observed for unsectioned dorsal spines of Walleye in two Minnesota lakes (70% and 95%; Logsdon 2007) and Sauger in the lower Missouri River (73%; Williamson and Dirnberger 2010). This was somewhat expected since standard broodstock sampling in natural lakes in Iowa typically target only large, adult Walleye, thus strongly influencing age structure of the sample.…”

Section: Discussioncontrasting

confidence: 58%

“…This was somewhat expected since standard broodstock sampling in natural lakes in Iowa typically target only large, adult Walleye, thus strongly influencing age structure of the sample. Studies that have recorded high reader agreement rates (>70%) for sectioned or unsectioned dorsal spine techniques were on Walleye populations dominated by younger individuals (Campbell and Babaluk 1979;Erickson 1983;Logsdon 2007;Williamson and Dirnberger 2010). Our age analysis estimated that 44-74% of recaptured Walleye used in our study were ≥10 years old and our reader agreement rates were poor (≤51%).…”

Section: Discussionmentioning

confidence: 99%

“…Consequently, many agencies have made adjustments to incorporate dorsal spines as a valid technique to estimate age and growth parameters for nonlethal fish surveys. The unsectioned spine technique proposed by Logsdon (2007) and later found to be a better and quicker technique as compared with sectioned spines (Williamson and Dirnberger 2010) has become an attractive alternative to estimate the age of numerous fish, but no BLC technique has been described or validated for this technique, thus limiting its use in traditional fisheries surveys. Our primary objective was to develop a standardized technique to perform BCL on unsectioned dorsal spines that could be used with the two most common BCL methods (i.e., DP and FL).…”

Section: Meerbeek and Hawkinsmentioning

confidence: 99%

“…Many male Walleye in this study were estimated to be older than age 6, and we often observed compressed annuli near the edge of dorsal spines while using each technique. Both Logsdon (2007) and Williamson and Dirnberger (2010) found that crowded annuli were much more visible for the unsectioned technique because of flexibility in lighting conditions when using the fiber optic light guide. However, our standardized unsectioned technique required the fiber optic light guide to be affixed to a permanent stand so BCL measurements could be taken at a standard distance, thus reducing the flexibility of the light source and resolution of outer annuli.…”

Section: Processingmentioning

confidence: 99%

“…Logsdon (2007) modified this technique for use on the dorsal spines of Walleye Sander vitreus and found that unsectioned spines closely replicated otolith-based estimates of population age structure. Furthermore, Williamson and Dirnberger (2010) compared precision of age estimates and processing times of sectioned (as described by Beamish and Chilton 1977) and unsectioned dorsal spines of Sauger S. canadensis, and found that while both techniques yielded similar age estimates, unsectioned dorsal spines took one-half as much processing time. In addition, side illumination of the unsectioned spine increased visibility of the crowded outer annuli on older fish as compared with that of the sectioned technique where those same annuli appeared split or discrete when viewed as a thin section (Logsdon 2007;Williamson and Dirnberger 2010).…”

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confidence: 99%

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A Standardized Technique to Back‐Calculate Length at Age from Unsectioned Walleye Spines

Meerbeek

Hawkins

2013

N American J Fish Manag

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The primary assumption of using back‐calculated length‐at‐age (BCL) methods to estimate fish growth is that the body length and hard‐part radius relationship is linear. Therefore, standardized techniques are required for BCL methods to be comparable over time. Recent studies have found that unsectioned dorsal spines of Sander spp. improve efficiency and provide accurate age estimates. We evaluated a simple, standardized method of using unsectioned Walleye S. vitreus (N = 162) dorsal spines to estimate age and BCL (direct‐proportion and Fraser–Lee methods) by comparing these estimates with those of a sectioned spine technique. We validated the technique by comparing observed growth (measured via a mark–recapture study) with BCL growth estimated via sectioned and unsectioned techniques. The time required to process, prepare, view and perform BCL for each of the two techniques was also compared. Both reader age estimates and exact reader agreement rates were significantly better using the sectioned spine technique. Age frequencies varied significantly among readers and techniques as differences ranged up to 8 years. No difference was detected among the slopes of the back‐calculation methods among techniques, but there were significant differences in the mean BCL estimates for ages < 10 years old. The relationships between observed growth and growth estimated via BCL methods were significant; however, BCL methods significantly overestimated Walleye growth. Total processing time for the unsectioned technique was significantly less, but based on our poor ability to replicate ages, we do not suggest the use of our standardized unsectioned spine technique to estimate the age or BCL older Walleye. In addition, no BCL method accurately estimated annual growth regardless of technique or reader experience. We conclude that more research is necessary to validate dorsal spine‐based BCL estimates on Walleye populations. Once validated, further research evaluating new or modifying our technique for unsectioned Walleye spines needs to be explored. Received February 14, 2013; accepted June 2, 2013

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Section: Discussioncontrasting

confidence: 58%

Section: Discussionmentioning

confidence: 99%

Section: Meerbeek and Hawkinsmentioning

confidence: 99%

Section: Processingmentioning

confidence: 99%

mentioning

confidence: 99%

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A Standardized Technique to Back‐Calculate Length at Age from Unsectioned Walleye Spines

Meerbeek

Hawkins

2013

N American J Fish Manag

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Precision of Three Structures for Saugeye Age Estimation

Koch

Neely

Sowards

2018

N American J Fish Manag

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We evaluated the precision of age estimates obtained from sagittal otoliths, scales, and dorsal fin spines from 341 saugeyes (Walleye Sander vitreus × Sauger S. canadensis) collected from six Kansas reservoirs. Between-reader agreement was greatest for otoliths, followed by dorsal spines and then scales. Coefficient of variation (CV) values for between-reader comparisons were 1.3-3.1% for otoliths and 13.8-18.2% for dorsal spines. Betweenreader comparisons for scales were the most variable, with CV estimates between 19.9% and 23.1%. Age estimates from otoliths aligned with age estimates from scales more often than with estimates from dorsal spines, although age estimate comparisons between structures were generally variable. Between-reader agreement for scales and dorsal spines decreased with increasing estimated age; however, agreement for otoliths generally remained high (i.e., >80%) through age 10. Given greater precision relative to other structures, we recommend the use of sectioned otoliths to estimate ages of saugeyes, especially when sacrificing the fish is not a concern. RESULTSSectioned otoliths, scales, and sectioned dorsal spines were collected from 341 saugeyes varying in TL from 130 to 670 mm (Figure 1). Between-reader agreement was generally greatest for otoliths, followed by dorsal spines and scales (Figure 2). Agreement between readers varied from 96.2% to 98.0% for otoliths, and CVs for reader combinations were between 1.3% and 3.1%. No bias between readers was detected for otoliths for any age estimate combination. Agreement between readers for scale age estimates varied from 64.1% to 68.8%, and CV values ranged from 19.9% to 23.1%. Significant deviations in scale age estimates between readers occurred at young 32 KOCH ET AL.

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