Comparative Age-Determination Techniques for White Sturgeon in California

Abstract

We compared growth patterns of clavicles, cleithra, opercles, medial nuchals, dorsal scutes, and pectoral fin ray sections from white sturgeon Acipenser transmontanus in California. The legibility and interpretability of growth patterns, ease of collection and processing, and relative precision of age estimates were evaluated for each structure with data collected on skeletal structures and morphometric measurements of 147 individuals ranging in size from 31 to 224 cm total length. Various methods were used to elucidate growth zones (thin-sectioning, oil and water clearing, staining, and X-ray radiography) to determine the most useful ageing technique for each structure. All calcified structures contained concentric growth zones that increased in number with the size of the fish and were interpreted as annual events. There was a direct linear relationship between size of the structures and size of the fish. Pectoral fin sections were the most practical ageing structure in terms of ease of collection, processing, legibility, and precision of interpretation. Age estimates from other structures resulted in poor precision between readers but relatively good intrareader precision. This suggests possible corroborative use with the development of better interpretive criteria and elucidation techniques. The von Bertalanffy growth curve calculated from age estimates based on pectoral fin sections for all samples produced a growth model for white sturgeon that compared favorably with those from previous studies.

A validated, minimally deleterious method for aging sturgeon

“…Brennan and Cailliet (1989) noted that bands from this fi n ray were consistent with the bands from fi n spines but did not evalu-ate the use of this fin ray as an aging structure. We found that the second marginal fin ray was simple to remove and that sections provided reliable and clear band counts.…”

“…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.…”

“…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. All structures except the fin spine have proved to be detrimental to or have required sacrifice of the fish (Brennan and Cailliet, 1989); therefore, the most widely used aging structure for sturgeon species is the fin 2 Nakamoto, R. J., T. T. Kisanuki, and G. H. Goldsmith. 1995 spine (Rien and Beamesderfer, 1994;Rossiter et al, 1995;Stevenson and Secor, 1999;Berg, 2004;Hurley et al, 2004;Whiteman et al, 2004;Allen et al, 2009).…”

“…Digital images of each section were taken with a MicroPublisher 5.0 real-time viewing camera (QImaging, Surrey, Canada) mounted on an RZ Series CMO stereo microscope (Meiji Techno America, Santa Clara, CA). Growth bands were counted by using standard aging methods (Brennan and Cailliet, 1989;Morrow et al, 1998;Stevenson and Secor, 1999), whereby a band pair consisted of one opaque and one translucent ring that was continuous around the section.…”

Changes in age composition and growth characteristics of Atlantic sturgeon ( Acipenser oxyrinchus oxyrinchus ) over 400 years

“…Modern samples came from ship strike mortalities and collections by commercial fishermen (8-35 cm stretch gill nets) ensuring that no fish were killed for this project. A piece of the pectoral spine near the base was removed and used to determine age by counting annual rings using transmitted light at 40Â magnification (Brennan & Cailliet 1989;Van Eenennaam et al 1996;Stevenson & Secor 1999;Sulak & Randall 2002). All samples were read blind by two experienced readers.…”