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Stable Carbon and Oxygen Isotope Ratios of Otoliths Differentiate Winter Flounder (Pseudopleuonectes americanus) Habitats
Citation:
PRUELL, R. J., B. K. TAPLIN, AND J. D. Karr. Stable Carbon and Oxygen Isotope Ratios of Otoliths Differentiate Winter Flounder (Pseudopleuonectes americanus) Habitats. Marine & Freshwater Research. CSIRO Publishing, Collingwood Victoria, Australia, 61(1):34-41, (2010).
Impact/Purpose:
This research involved the development of a technique that may be useful in identifying the relative importance of various nursery areas to the winter flounder fishery off of the coast of Southern New England. Juvenile winter flounder were collected from various near shore nursery areas in Narragansett Bay and several coastal ponds and otoliths (calcium carbonate earstones) were obtained from the fish. Carbon and oxygen stable isotope measurements were conducted on the otolith samples and these isotopic ratios were compared among collection sites. Adult fish from the same cohorts have recently been collected and the isotope fingerprints of the juvenile portions of these otoliths will be compared to those of the juveniles. It is believed that these comparisons will provide useful information on which nursery areas are the most important to the winter flounder fishery.
Description:
Stable carbon (13C) and oxygen (18O) isotope ratios were measured in otoliths of juvenile winter flounder (Pseudopleuronectes americanus) collected from 18 nursery areas along the coast of Rhode Island, USA. Samples were obtained during June and July of 2002 from locations that included a wide range of physical characteristics (salinity, temperature) and habitat types (unvegetated areas, macroalgae beds and eelgrass stands) from locations in Narragansett Bay, several coastal ponds and a riverine system. Sagittal otoliths were removed from the juvenile winter flounder, cleaned, and analysed for 13C and 18O using continuous flow isotope ratio mass spectrometry. Mean 13C values ranged from -3.2 ± 0.72 to -0.54 ± 0.61 permil (‰) and 18O ranged from -4.36 ± 0.48 to -1.23 ± 0.53 ‰ among nursery areas. Plots of 13C versus 18O and linear discriminant function analysis (LDFA) indicated differences among samples collected from Narragansett Bay, the coastal ponds and the Narrow River. Separations were also observed among fish collected in the upper, middle and lower portions of Narragansett Bay and along the salinity gradient in Narrow River. Otoliths from sample sites grouped on the basis of low, medium and high salinities also showed differences according to LDFA analysis. Linear regression analysis indicated a significant positive correlation (r = 0.72, P < 0.01) between 18O and salinity for the combined data set. These results indicate that 13C and 18O values of juvenile winter flounder otoliths may prove useful for differentiating individuals from various natal habitats or nearshore regions.