Tagging the next generation: validation of trans-generational chemical tagging for an endangered fish
In this study we validated marking offspring through peritoneal injection of ripe females using two concentrations of strontium (strontium chloride hexahydrate). Larvae from treatments were monitored for condition morphometrics and tested for chemical mark incorporation in their otoliths via laser ablation inductively coupled plasma mass spectrometry (LA-ICPMS) to quantify the strontium concentration (Sr/Ca) and laser ablation multi-collector inductively coupled plasma mass spectrometry (LA-MC-ICPMS) to measure the strontium isotope ratios (87Sr:86Sr) of otoliths. Otolith strontium concentrations and strontium isotopes ratios were elevated in the high-concentration treatment, while the low-concentration and control treatments were not significantly different from each other. Larval size and eye diameter at hatch were similar among treatments; however, yolk and oil globule diameters were significantly reduced in the high-concentration treatment. Moreover, growth rates after 60 days post-hatch were significantly reduced in the high-concentration treatment relative to the low-concentration and control treatments, suggesting trans-generational tagging can have deleterious effects on offspring. Our study provides evidence for the efficacy of artificially marking offspring via injection of strontium into ripe females and could provide new tools for managing endangered fish populations; however, careful consideration of chemical concentrations and dosages may be required prior to its application in a fisheries management experiment.
KeywordsOtolith Microchemistry Trans-generational chemical tag Delta smelt Laser ablation
We thank Ashley Ratcliffe, Norm Ponferrada and Levi Lewis (UC Davis) for their invaluable assistance marking fish and processing samples; Justin Gleissner and Joel Commisso for their critical help at the ICP-MS lab. We also thank Luke Ellison and other staff members at the UC Davis Fish Conservation and Culture Laboratory for their invaluable help with experimental fish. Paul Cadrett and Kim Webb (Stockton U.S. Fish and Wildlife Service Office) provided valuable comments, and along with DWR Staff (Cassandra Enos; Russ Stein and Carl Torgerson), facilitated critical study implementation. Jewel Huckaby and Sheryl Moore (DWR) provided timely coordination of sample collections at the Skinner Fish Facility. Project was funded by U.S. Bureau of Reclamation under Cooperative Agreement #81332 7 J010 between UC Davis and the Stockton U.S. Fish and Wildlife Service Office.
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