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PD/A CRSP Aquanews-Winter 2003

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Graduate’s Corner

ongratulations to Master’s graduate Ulises Hernández Vidal on completion of his degree from Universidad Autónoma de Nuevo León (UANL), Mexico, in November 2002. His advisors were Roberto Mendoza Alfaro at UANL and Gabriel Márquez-Couturier at Universided Juárez Autónoma de Tabasco (UJAT). Márquez is a co-Principal Investigator in the PD/A CRSP Mexico Project.

In the early 1990s Hernández worked as an undergraduate volunteer in the aquaculture lab at UJAT. He conducted his graduate research with the PD/A CRSP project at UJAT in 2001 and 2002. Hernández is presently at teaching two courses at UJAT as well as serving as a technician in the PD/A CRSP Mexico Project.

TROPICAL GAR (ATRACTOSTEUS TROPICUS) SEX IDENTIFICATION AND HORMONAL INDUCED SPAWN EVALUATION
(abstract of Ulises Hernández Vidal’s M.S. thesis)

    The purpose of this study was to identify the sex and evaluate induced spawning of the tropical gar, Atractosteus tropicus, using plasmatic vitellogenin (VTG) concentrations as reference. Purified vitellogenin was obtained from estrogen treated males, which in turn was used to obtain polyclonal antibodies. These antibodies were used to measure the plasmatic concentrations of VTG in gars. Female VTG levels were used to separate groups of animals with similar levels. Spawning was then induced with intraperitoneal injections of D-Ala6-LHRHa, Des-Gly10-LHRHe, Estradiol, and OvaprimTM. Antiserum reactions between plasma samples and VTG were used along with VTG levels to identify the sex of wild and domesticated gars. Using the induction of reproduction and VTG-quantification methodologies, we have been able to obtained spawns for four consecutive months. The use of LHRH analogs and OvaprimTM were effective inducing spawning, providing high fertilization and hatching rates. High larvae quality was observed and the lowest survival rate was 80% at a density of 20 larvae per liter. The results of this study indicate than sex identification and spawning control is possible in tropical gars. The quality of the larvae obtained from early spawns was similar to that obtained during the normal period spawns. With this protocol, the reproduction events can be scheduled for several months instead of the previously restricted two-week period used in past years. The results obtained in this study are very important for hatchery optimization, broodstock management, and personnel efficiency in farms.

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