A validated, minimally deleterious method for aging sturgeon

Abstract

Abstract-To determine the most suitable aging structure for sturgeons, band counts of transverse sections of otoliths and the pectoral-, dorsal-, pelvic-, and anal-fin rays of Gulf sturgeon (Acipenser oxyrinchus desotoi) were compared. The otoliths and dorsal-, pelvic-and anal-fin rays produced inconsistent band patterns, but bands formed in the first (fin spine) and second marginal pectoral-fin rays were easily read and the most consistent. The index of average percent error and the coefficient of variation between final ages from the fin spines and the second marginal fin ray were 0.75% and 1.06%, respectfully. Percent agreement between the assigned age of the fin spine and second marginal fin ray was high. The fin spine is commonly used to age sturgeon species; however, removal of the fin spine was considered potentially deleterious, especially to larger sturgeon. Sampling the second marginal fin ray appeared to be less harmful. Annual band formation in the second marginal fin ray for 3 Gulf sturgeon was validated with the use of oxytetracycline. We propose the second marginal pectoral-fin ray as an acceptable and less harmful alternative structure to the fin spine for aging Gulf sturgeon and recommend its use for other threatened and endangered sturgeon species. An extraction method of minimal invasiveness is presented here for field removal of the second marginal pectoral-fin ray from live sturgeon.

Validating Fin Ray Microchemistry as a Tool to Reconstruct the Migratory History of White Sturgeon

“…There are also some challenges to accurately delineating annual growth rings in older individuals, which could limit the application of this method for studies that aim to determine the effects of specific environmental conditions to rearing and spawning migration behavior. Some studies have reported good correspondence between age estimates from fin rays (Rossiter et al 1995;Baremore and Rosati 2014), while estimation errors of up to 2-4 years have been reported in other studies (Rien and Beamesderfer 1994;Paragamian and Beamesderfer 2003;Hurley et al 2004;Whiteman et al 2004;Jackson et al 2007). These errors may not be as important when examining questions of the relative importance of different rivers for successful recruitment or when determining river fidelity, but caution should be exercised when using fin ray microchemistry to examine the effects of interannual environmental variation on spawning, out-migration timing, or age at first spawn.…”

“…One potential limitation of otolith and fin ray trace elements and isotope ratios as tools to reconstruct migratory history is uncertainty in age determination. Harkness (1923) and Schneberger and Woodbury (1944) used otoliths to estimate sturgeon age and reported high precision, but more recent studies have reported difficulty in obtaining interpretable age estimates from otoliths (Currier 1951;Brennan and Cailliet 1989;Stevenson and Secor 1999;Baremore and Rosati 2014). Although age estimates from pectoral fin rays have sometimes been found to be inaccurate or imprecise (e.g., Paragamian and Beamesderfer 2003), they appear to be the most reliable structure for use in sturgeon age estimation (Kohlhorst et al 1980;Rien and Beamesderfer 1994;Jackson et al 2007).…”

Fin healing and regeneration in sturgeon

“…Three different fin sampling treatments were applied to the right pectoral fin of fish (n = 8-9 fish per treatment): entire leading fin spine removed, a 1-2 cm portion removed near the point of articulation or a 1-2 cm portion removed from a secondary fin ray using a coping saw or a scalpel and bone clippers ( Figure 1). Removal techniques were based on those used for field sampling (Baremore & Rosati, 2014;Rien & Beamesderfer, 1994). After fin treatments, all fish were given an injection into the dorsal musculature of 25 mg OTC kg −1 body mass (Liquamycin, Zoetis; www.zoetis.com), following Stevenson and Secor (1999), except for an additional group (n = 8) that had the entire fin spine removed but no antibiotic to assess effects on healing.…”

Growth Estimation of Western Population Segment Gulf Sturgeon Using Length‐at‐Age and Mark–Recapture Data

“…). Moreover, the occasional formation of double rings (Sulak and Randall ) and false annuli (Stevenson and Secor ) in spines make it complicated, but Baremore and Rosati () suggested an alternative approach using the second fin ray for Gulf Sturgeon. Therefore, using an additional source for growth estimation, such as mark–recapture data, may help to elucidate bias between the two age estimation techniques (Paragamian and Beamesderfer ; Dippold et al.…”

“…Unfortunately, the accuracy of counting fin spine annuli may be unreliable for Gulf Sturgeon after about age 8-10 because of the convergence of ring margins and the loss of core rings (Sulak et al 2016). Moreover, the occasional formation of double rings (Sulak and Randall 2002) and false annuli (Stevenson and Secor 1999) in spines make it complicated, but Baremore and Rosati (2014) suggested an alternative approach using the second fin ray for Gulf Sturgeon. Therefore, using an additional source for growth estimation, such as mark-recapture data, may help to elucidate bias between the two age estimation techniques (Paragamian and Beamesderfer 2003;Dippold et al 2016).…”