Insight into Danube sturgeon life history: trace element assessment in pectoral fin rays

Abstract

Sturgeon populations in the Danube River have experienced severe decline during the last several decades, mostly due to the poorly regulated fishery, river fragmentation and water pollution. This study focuses on gaining better understanding of sturgeon life history primarily by addressing the assessment of microelement accumulation in sturgeon pectoral fin rays, especially of strontium and calcium, as a method that can reveal migration patterns of anadromous sturgeons. Analysis was performed on pectoral fin samples of three anadromous Danube sturgeon species (beluga, Russian sturgeon and stellate sturgeon) by the use of a Nuclear Microprobe technique. The most frequent pattern in analyzed samples was represented by a low Sr:Ca ratio in the innermost annuli, followed by an increased ratio in the middle annuli segment, and often with a decreased ratio in the outermost annuli. Probability density estimate has revealed three distinguished maxima of the Sr:Ca ratio, 7.08×10 −3 , 8.98×10 −3 and 9.90× 10 −3 , which might correspond, respectively, to fresh, brackish and saltwater. Although the analysis of the Sr:Ca ratio in sturgeon pectoral fin rays has revealed changes that might indicate probable migration between habitats with different water salinity, further studies are needed for improvement of this method. This study represents the first analysis of this kind that was conducted on sturgeon species from the Black Sea basin.

Chemical archives in fishes beyond otoliths: A review on the use of other body parts as chronological recorders of microchemical constituents for expanding interpretations of environmental, ecological, and life‐history changes

“…These indicators have been used in sturgeon to infer anadromous migrations 30 yr after they occurred (Allen et al ). Sturgeon have also been traced back to their rivers of origin by studies seeking to identify juvenile habitats for conservation purposes (Jaric et al ). Similar “river‐of‐origin” studies via TEA of fin rays have been applied to the nursery habitats of esocids (Rude et al ), centrarchids (Smith and Whitledge ), and catastomids (Wolff et al ).…”

“…TEA has traditionally focused on migratory behavior and habitat use in individual fishes (Phelps et al 2012). Notably, the analysis of divalent ions over time in fin rays has been of interest to distinguish between saltwater and freshwater environments (Arai et al 2002;Allen et al 2009;Jaric et al 2012). In this way, researchers have been able to detect diadromous migrations using the presence of elements such as Ba and Sr, which are used as proxies for fresh water (Tzeng et al 1997;Guay and Falkner 1998).…”

Research Tools to Investigate Movements, Migrations, and Life History of Sturgeons (Acipenseridae), with an Emphasis on Marine-Oriented Populations

“…Although fin rays have the potential for remodelling, several researchers have shown the stability of elemental signatures in fin rays over time, suggesting they are stable structures appropriate for use in microchemical analyses [60], [170], [173].…”

“…The current tagging study may be more successful than the previous effort due to a moratorium on sturgeon fishing currently in place in the Romanian and Bulgarian portions of the Danube River. New research that incorporates microchemistry techniques is focusing on the use of trace elements to understand migratory patterns [60]. Future monitoring and assessment studies that incorporate tagging will be important in understanding whether fishing moratoria are being respected and if sturgeon populations are successfully recruiting and rebounding.…”

Life‐history studies by non‐lethal sampling: using microchemical constituents of fin rays as chronological recorders

“…In a variety of species, studies have documented conserved trace‐element concentrations (especially divalent ions such as Ba and Sr, which have similar ionic radii to Ca) within otoliths and fin rays that correlate with concentrations in ambient water (Clarke et al , ; Woodcock et al , ). While elements deposit into otoliths and fin rays through different internal pathways, the correlation of certain elements with the ambient environment suggests layers retain their chemical properties over time in both structures, rather than being re‐worked (Clarke et al , ; Allen et al , ; Smith & Whitledge ; Jaric et al , ; Phelps et al , ; Woodcock & Walther, ). Inner fin‐ray layers become encapsulated by growing outer layers, after which the encapsulated inner layers lose their vascularization, thus inhibiting tissue turnover within the inner layers (Sire & Huysseune, ).…”