Darys Isabel Delgado’s scientific contributions

Effects of temperature and salinity on hatching rate and normal larval rate at hatching, and survival of fasting larvae after hatching (survival activity index; SAI) were investigated using spontaneously spawned eggs of captive yellowfin tuna (Thunnus albacares, YFT). Within the range of experimental temperatures, 23–35 °C, at 32 psu salinity, hatching and normal larval rates and SAI were highest at 23 and 26 °C. In the experiment exploring the most suitable salinity within the range 23–38 psu, 35 and 38 psu gave the highest hatching rate and normal larval rate; however, SAI was highest at 26 psu. The results of multi-factor experiments in each temperature (23, 26, and 29 °C) with each salinity (32, 35, and 38 psu) indicated interactive effects of temperature and salinity on the three indices and within the experimental ranges gave an optimal combination of 23 °C and 38 psu for YFT hatching and survival.

The anesthetic action of MS-222, 2-phenoxyethanol, and clove oil on early juveniles of yellowfin tuna Thunnus albacares age 24 and 25 days post hatching was examined. Three different concentrations of each anesthetic were utilized and both anesthetic efficacy and postanesthetic recovery were noted for each treatment. Survival of recovered individuals was also examined 24 hours after anesthetic treatment. Among the nine experimental treatments, 500 ppm of 2-phenoxyethanol was the most effective. The treatment showed the perfect anesthetic effect, high rate of initial recovery, and 50% survival at 24 hours after initial recovery.