Identification of Hatchery-Reared Lake Sturgeon Using Natural Elemental Signatures and Elemental Marking of Fin Rays

Stock enhancement programs often involve the introduction of hatchery-reared fish into wild environments, with the goal of increasing the abundance of a particular stock. To measure the success of stocking efforts for depressed populations, hatchery-reared individuals must be distinguishable from naturally spawned fish, potentially many years after release. Biological tags are attractive due to their ability to batch-mark whole cohorts in a cost-effective manner, with minimal disruption to hatchery procedures and reduced handling stress inflicted on individuals during the marking process. Elemental marking may occur naturally or via deliberate manipulation of the concentration of specific elements to create recognizable elemental signatures in the hard structures of fish (e.g., fin rays and otoliths). In this study, elemental signatures in the fin rays of known hatchery-released Lake Sturgeon Acipenser fulvescens (ages 1-7) were quantified via laser ablation (LA) inductively coupled plasma-mass spectrometry (ICP-MS) to assess whether the ambient water chemistry in a groundwater-fed hatchery would create an elemental signature that facilitated discrimination of hatchery-reared individuals from those naturally spawned in the wild. The concentrations of divalent trace elements, particularly Mn, within the first growth band of hatchery-reared fish were significantly different from those of wild conspecifics, allowing us to accurately classify hatchery- versus wild-spawned individuals with 99% success. In addition, we conducted a preliminary experiment to test the validity of two separate 24-h immersions in Sr-86 and Ba-137 (immersions were conducted 30 d apart) to induce multiple combination marks in the fin rays of juvenile Lake Sturgeon. Fin rays collected 60 d after the second immersion were analyzed for isotopic ratios via LA ICP-MS, and results indicated that elemental marking at both time points was achieved with 100% success. Induction of a combination of isotopic signatures could enable hatcheries to track the success of families or stocking groups within a single year-class or across multiple year-classes.