AFFECTATION OF GROWTH, WEIGHT AND SURVIVAL OF Crassostrea gigas IN ESTERO LA PIEDRA, GUASAVE, SINALOA IN SUBTROPICAL WATERS

The present study determines the effect of environmental variables on the growth and survival of triploid and diploid oysters, Crassostrea gigas, in the northwest Mexican Tropical Pacific. Spat sowing was conducted from winter to autumn, with the use of the Long-line culture method. Cleaning of the modules, measurement of environmental variables and population parameters were conducted on a bi-monthly basis. Meanwhile, the condition index of the organisms was determined and water samples for quantification of total suspended solids, particulate organic matter and chlorophyll a were obtained on a monthly basis. Temperature ranged between 25.01±5.29ºC and salinity varied up to 32.88±2.15 ups.  Dissolved oxygen oscillated from 6.10±1.93 mg L^-1 and pH from 7.83±0.39 UpH. Total suspended solids oscillated from 59.04±23.61 mg L^-1, particulate organic matter from 12.38±5.06 mg L^-1 and chla from 47±2.85 mg m^-3. Tukey analysis showed significant differences between the length and weight of both diploids and triploids with diploids showing a greater length of 70.36±26.58 mm; whereas triploids obtained a length of 69.47±25.44 mm. Triploids obtained a greater weight of 41.49±29.10 g, while diploid weight was 40.57±29.52 g. Triploid mortality was 2.92±5.07 organisms, while diploid mortality was 5.32±9.27 organisms (Figure 1). With respect to the condition index, significant differences were obtained between diploid and triploid organisms. Canonical correlations determined that temperature was the variable that influenced the growth of both diploids and triploids; as the highest temperatures coincided with spawning episodes. Thus it is important to take into consideration culture dates, so as to prevent excessive mortality.