Lake Sturgeon Age Validation using Bomb Radiocarbon and Known‐Age Fish

Abstract

Pectoral fin spines have been the accepted structure for estimating the age of various sturgeon species for nearly 100 years, though other structures have also been used (otoliths, pectoral girdle, scutes, and caudal fulcra). Accuracy of age estimates using any of these structures has not been validated, so we report the first use of bomb radiocarbon ( 14 C) assays to assess the validity of ages estimated using growth increments on pectoral fin spine and otolith frontal cross sections from lake sturgeon Acipenser fulvescens; we also assessed age estimates from pectoral fin spines of known-age lake sturgeon. Growth increments on pectoral fin spine cross sections underestimated true age of fish older than 14 years and error increased with age, whereas otoliths accurately estimated true age up to at least 52 years. Increment formation on pectoral fin spine and otolith cross sections from juvenile lake sturgeon (ages 2-11) was similar, although pectoral spines were clearer and easier to interpret. A power function (true age ¼ [estimated age] 1.054796 , where estimated age was determined from pectoral spines; r 2 ¼ 0.98) provides a means for correcting existing age estimates obtained from lake sturgeon pectoral fin spines.

Estimating Differences in Growth and Metabolism in Two Spatially Segregated Groups of Columbia River White Sturgeon Using a Field-Based Bioenergetics Model

“…Of these, pectoral fin rays have been shown to provide the most accurate age, but significant errors can still exist in age-assignment. These errors have been shown to increase with fish age and growth rates [30], however in contrast to the large errors estimated by Paragamian and Beamesderfer [31] a recent study of lake sturgeon suggests that ages derived from fin rays may be small and predictable [32]. Additionally, our method incorporates information from age estimates from both pectoral fin rays and length-increment.…”

A validated, minimally deleterious method for aging sturgeon

“…Although otoliths often are considered the best structure for aging fish (Casselman, 1987;Campana, 2001), band formation in otoliths of Gulf sturgeon was unreliable and difficult to interpret. Similar difficulties have been noted for other sturgeon species (Brennan and Cailliet, 1989); however, bomb radiocarbon dating has been used to validate band formation for 46 otoliths of lake sturgeon (Bruch et al, 2009). Fin spines provide mostly clear and interpretable banding patterns, and their use has been validated for several species (Rien and Beamesderfer, 1994;Rossiter et al, 1995), but their removal has been discouraged for threatened and endangered sturgeon species because of the possibility of deleterious effects (Kahn and Mohead, 2010).…”

“…Moreover, these life history traits, as well as habitat issues, equate to a difficult recovery process. Age estimates of several species of sturgeon in North America have been evaluated by removing and observing the banding patterns of calcified structures, such as the first marginal pectoral-fin ray, otoliths, scutes, opercula, and sphenoids (Brennan and Cailliet, 1989;Nakamoto et al 2 ;Rossiter et al, 1995;Stevenson and Secor, 1999;Hurley et al, 2004;Jackson et al, 2007;Bruch et al, 2009). Although it is not a true spine, the first marginal pectoral-fin ray of sturgeons commonly is called the fin spine, and hereafter it will be referred to as such in this article.…”

“…Gulf of Mexico mounted in 2 Ton Epoxy (ITW Devcon, Danvers, MA) and sectioned according to Bruch et al (2009). Sections (0.5 mm) were mounted on a microscope slide with Cytoseal mounting medium.…”

Inferring functional extinction based on sighting records

“…Only 13 sightings of ship sturgeon have been confirmed between 1955 and 2015 (Table 3). Of these, it is possible to estimate the ages of 12 specimens based on a regression of body length and weight (Holčik, 1989), while using the correction factor for age assignment by Bruch et al (2009;see online Appendix). Four specimens were omitted from the analysis, since they belonged to cohorts spawned before the beginning of the observation period.…”