Stable isotope analyses of otoliths in identification of hatchery origin of Atlantic salmon (Salmo salar) in Maine
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We conducted stable oxygen and carbon isotope analyses for otoliths of Atlantic salmon (Salmo salar), in an attempt to develop a reference database on isotopic variability among private and federal hatcheries in Maine which currently support the salmon aquaculture industry and recovery of endangered populations. During the first phase of our study, we collected 40–50 sagittal otoliths of juvenile Atlantic salmon from each of the five hatcheries and analyzed for stable oxygen and carbon isotope ratios (18O/16O or δ18O, and 13C/12C or δ13C). Combination of δ18O and δ13C signatures in otoliths showed that the five hatcheries can be clearly separated and chemically distinguished. By identifying stable isotopic variations of otoliths from different hatchery settings, we were able to establish some isotopic criteria or standards to assign a likelihood that an individual Atlantic salmon came from a specific hatchery within the reference database. If successful, a diagnostic tool that can provide definitive information on identification of the hatchery origin could serve as a novel marking technique, and the chemical method may provide a more effective alternative to DNA analysis for mixed stocks. Overall our isotopic data from otoliths support the hypothesis that there are detectable differences between the five hatcheries, and multiple statistical analyses indicated that we can correctly distinguish individual Atlantic salmon into a hatchery with high confidence.
KeywordsAquaculture salmon Restoration hatchery Statistical difference δ13C and δ18O
This project could not have been done without the interest and support of Makah Tribal Council and the NOAA Fisheries Protected Resources Division, Northeast Regional Office (NERO) in Gloucester. Many staff members and individuals at both federal and private hatcheries and NERO helped us during the otolith sample collection and analysis. We especially thank Mary Colligan and Pat Scida at NERO for their support for the initiation of the project. We also thank Cooke Aquaculture, Oren Kephart (Gardner Lake hatchery), Greg Lambert (Oquossoc hatchery), and Brian Wheeler (Bingham hatchery) for providing salmon smolts from commercial hatcheries; and the United States Fish and Wildlife Service, Fred Trasko (GLNFH) and Tom King (CBNFH) for providing salmon smolts from federal hatcheries for otolith sampling. In addition, Greg Lambert, Denise Buckley, and Fred Trasko kindly provided water temperature records from their hatcheries. Wesley Patrick in NERO and Tim Sheehan in Northeast Fisheries Science Center in Woods Hole helped us in statistical analyses. We are grateful to Ms. Lora Wingate at the Stable Isotope Laboratory, University of Michigan at Ann Arbor, for her assistance with processing otolith samples. Three anonymous reviewers made comments and suggestions that improved the quality of the initial manuscript.
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