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STABLE ISOTOPE RATIOS IN ARCHIVED STRIPED BASS SCALES
Citation:
Taplin, B K. AND R J. Pruell. STABLE ISOTOPE RATIOS IN ARCHIVED STRIPED BASS SCALES. Presented at New England Estuarine Research Society, Block Island, RI, November 2, 2000.
Description:
In recent years fishermen and scientists have noted that striped bass caught along the East Coast of the United States have reduced weight to length ratios with many of the fish caught in Chesapeake Bay exhibiting skin lesions. Several theories have been suggested to explain these occurrences including bacterial disease, habitat changes due to anthropogenic impacts or dietary shift as a result of reduced prey abundance for the striped bass.
Measurements of stable isotopes of nitrogen (15N/14N and carbon (13C/12C) in striped bass scales and muscle tissue were used to determine trophic structure and changes in diet of striped bass over the past two decades. Archived striped bass scales
and muscle tissue from Rhode Island and Chesapeake Bay were prepared and analyzed for stable isotopes of carbon and nitrogen using Isotope Ratio Mass Spectrometry (IRMS).
Consistent relationships were observed between isotope ratios in striped bass scales and muscle tissue for Rhode Island fish. Nitrogen isotope ratios were enriched by about 2? in scales compared to muscle, and carbon isotope ratios were depleted in scales by about 3? compared to muscle tissue. In Rhode Island striped bass scales, carbon isotope ratios increased from 1989 to 1996; carbon isotope ratios in Chesapeake Bay striped bass scales increased from 1982 to 1997. Isotopic analysis of potential striped bass prey items from Rhode Island and Chesapeake Bay showed that benthic/invertebrate species were isotopically enriched in 13C relative to pelagic/fish species. Changes in 13C in scales were consistent with a shift in the feeding patterns of striped bass from a diet of fish (menhaden, anchovy, and herring) to a diet higher in benthic/invertebrate species (crabs and shrimp). Preliminary results from this study support the idea that over the past 20 years there has been a detectable shift in feeding patterns of striped bass.