AN IMMUNOLOGICAL STUDY OF PREDATION ON HATCHERY-REARED, JUVENILE RED DRUM (SCIAENOPS-OCELLATUS, LINNAEUS) - DESCRIPTION OF AN ELISA AND PREDATOR-PREY STUDIES IN NATURE

This report is a continuation of an on-going study to develop immunolo gical methods for eventual use in determining the predation mortality of newly released, hatchery-reared red drum (Sciaenops ocellatus, Linn aeus). Using a specific goat antiserum produced to a purified 80 kDa r ed drum glycoprotein, we detected the glycoprotein routinely in solubl e extracts of red drum by Western blots. To supplement the immunoblott ing, we proceeded to develop a highly sensitive and specific ELISA (en zyme-linked immunosorbent assay). The major problem in developing the ELISA was defining conditions to eliminate a natural inhibitor in solu ble extracts of red drum that prevented the 80 kDa protein from bindin g to microtiter plates. The technical difficulties for a successful EL ISA were resolved by adjusting extracts to pH 4.7 and 0.3 M NaCl, base d on conditions developed for purification of the 80 kDa protein on a cationic-exchange gel by fast protein liquid chromatography (FPLC). Th e defined parameters eliminated the inhibition and resulted in optimal binding of the glycoprotein to the polymer surface of plates for ELIS A. Approximately 10 h after the release of tens of thousands of red dr um fingerlings at two sites in Biscayne Bay, FL, USA, a center-bag hau l seine was used to sample the fish and capture predators. Two species , Sphyraena barracuda (Walbaum), great barracuda, and Strongylura nota ta (Poey), redfin needlefish, were the major predators. ELISA and West ern blots were used to identify visually difficult or unidentifiable S ciaenops ocellatus in gut contents of the predators. Based on nine sam ples from seven Strongylura notata, and 10 samples from eight Sphyraen a barracuda, 100% of the samples were identified as red drum in the ne edlefish and 50% in the great barracuda. These studies confirm the fea sibility of using immunological methods to identify otherwise unidenti fiable prey in gut contents of predators in nature.