PRELIMINARY OBSERVATIONS OF ORANGEMOUTH CORVINA SPAWN INDUCEMENT USING PHOTOPERIOD, TEMPERATURE AND SALINITY CYCLES

Subadult orangemouth corvina ( Cynoscion xanthulus ) collected in fall 1981 from the Salton Sea, California, were transported to Texas to determine methods to induce spawning in indoor closed culture systems. Sexual naturation was stimulated with artificially controlled annual photoperiod, water temperature and salinity cycles which mimicked conditions historically found at the Salton Sea. Corvina readily adapted to intensive culture and grew rapidly, approaching maturity by spring 1982. Sexual development was monitored by catheterization. Corvina were found to be summer spawners. Males approximately 500 mm total length became sexually mature, producing milt from at least June to October of the 1982 and 1982‐83 cycles. Females approximately 590 mm total length developed eggs (0.05‐0.70 mm diameter, unhydrated) from at least June to October of the 1982‐83 cycle, but did not spawn. Because spawning had not occurred by late summer 1983 and egg development stopped progressing, two females with egg diameters of 0.40‐0.55 mm were each administered a single injection of 550 USP units/kg body weight human chorionic gonadotropin. Egg hydration and ovulation occurred within 30 hours of hormone injection in each female. The first female had many eggs clumped in masses but was able to release eggs which appeared fully developed. The other female died because hydrated eggs were clumped together in large masses and could not be released. Males attended females during the time of egg hydration and ovulation and apparently released milt, but no eggs developed or hatched. Experiments to induce spawning are continuing.