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Spatial and Temporal Trends in Stable Carbon and Oxygen Isotope Ratios of Juvenile Winter Flounder
Citation:
PRUELL, R. J., B. K. TAPLIN, AND J. D. Karr. Spatial and Temporal Trends in Stable Carbon and Oxygen Isotope Ratios of Juvenile Winter Flounder. Environmental Biology of Fishes. Kluwer Academic Publishers, , Netherlands, 93(1):61-71, (2012).
Impact/Purpose:
This manuscript advances the development of methodology 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 over a period of three years. The otoliths (calcium carbonate earstones) were obtained from the fish and carbon and oxygen stable isotope measurements were made on these samples. Comparisons were then made of otolith isotope fingerprints among the three sampling years. The results indicate that the fingerprints differed among years; therefore, fingerprints need to be developed for each yearly cohort in order to study connectivity between nursery areas and the offshore fishery. This information is important to the Agency because it furthers the development of a technique that could be used to identify those habitats that are the most important to protect from alteration for estuarine dependent fish species.
Description:
Isotopic ratios of fish otoliths have been used in numerous studies as natural tags or markers to aid the study of connectivity among fish populations. We investigated the use of spatial and temporal changes in the stable carbon and oxygen isotope ratios of otoliths to differentiate juvenile habitats of winter flounder (Pseudopleuronectes americanus). Juvenile winter flounder were collected annually over a three-year period from 18 stations along the coast of Rhode Island, USA. Sagittal otoliths were removed from fish and analyzed for stable carbon (13C/12C or 13C) and oxygen (18O/16O or 18O) isotope ratios using continuous flow isotope ratio mass spectrometry. Differences in isotope ratios were observed among stations and along salinity gradients in the Narragansett Bay estuary and an estuarine river system (Narrow River). Overall, the isotope ratio patterns observed among stations were consistent over the three sampling years; however, differences were noted in isotope ratios and the magnitude of the isotope ratio gradients among years. Yearly changes in 13C and 18O did not correlate with temperature; however, significant positive correlations were noted between salinity and 13C for two of the three years. For each of the three years sampled there was a highly significant positive correlation (2002, r = 0.93, P < 0.01; 2003, r = 0.80, P < 0.01; 2004, r = 0.97, P <0.01) between 18O and the salinity of the collection site. Also, there was a strong correlation between the mean annual salinity for all stations and 18O for the three sampling years (r = 0.99, P <0.01). These findings suggest that yearly changes in the volume of freshwater inputs to these estuarine habitats may be related to the differences observed in otolith 18O isotope ratios. Because of these year-to-year differences, sampling of each cohort may be necessary in order to use this isotopic technique for winter flounder connectivity studies.