| DEVELOPMENT OF AN IDENTIFICATION MANUAL FOR THE EARLY LIFE HISTORY STAGES OF FISHES OF THE MIDDLE ST. JOHNS RIVER, FLORIDA. |
| SCRIPTER, M., Shenker, J.M., Farson, A.L., Florida Institute of Technology, Melbourne, FL, USA 32901; mscripte@fit.edu, shenker@fit.edu, afarson@gmail.com, and Miller, S.J., St. Johns River Water Management District, Palatka, FL 32177 |
| Research on the early life history (ELH) stages of fishes in fresh water, estuarine, and marine systems provides critical information on the structure and function of ecosystems, the biology, ecology, and population structure of fishes, and guides management of vital resources. One of the key difficulties with ELH studies is the accurate identification of diverse specimens from natural habitats. Ontogenetic changes in morphology, meristic characteristics, and pigmentation, habitat-influenced pigmentation variance, and intraspecific character variance make identification a challenging effort. Researchers have typically focused on developing and publishing identification methods for single species, or closely related taxa. Studies of diverse natural assemblages of larvae thus require collating the existing literature from a wide array of studies that may span decades of research and be of widely varying quality. In recent years, several magnificent collations of these studies have greatly enhanced the abilities of ELH researchers working in certain parts of the world. Our intensive study of the ELH stages of fishes of the St. Johns River required a similar effort to collate a widely-dispersed literature. The need for rapid processing of 1000s of samples by relatively untrained workers made it even more critical to design an identification manual that combined both quantitative and qualitative characteristics across the ontogenetic development of each species. We began this effort by compiling the descriptive literature for the ELH stages of species expected to reproduce in the St. Johns River, Florida. As ichthyoplankton samples were processed, individual fishes were identified, measured, and photographed to develop the identification guide. Photographs were then marked with circles, arrows, and other descriptors to help highlight specific identification features (e.g., gut length, mouth morphology, pigmentation, myomere counts, etc.) that can differentiate species. As additional larvae were examined, their photographs, updated characteristics, and corrected morphometrics were progressively incorporated into the developing manual. Identification characteristics were used to develop a dichotomous key to families, then more precise guidance for separating closely-related taxa was provided. At present, our St. Johns River identification manual includes photographic and morphometric/meristic identification methods for 41 species within 21 families of fishes. Upon completion of this work in the near future, we anticipate publication of a comprehensive identification manual for these fishes that can be easily used by trained researchers and by students just entering the field. |
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