The effects of body weight, temperature, salinity, pH, light intensity and feeding condition on lethal DO levels of whiteleg shrimp, Litopenaeus vannamei (Boone, 1931)

Tolerance of whiteleg shrimp Litopenaeus vannamei exposed to different temperatures (14.5, 21.5, 24.8, 27.8, 30.8, and 35.0 degrees C), salinities (9, 15, 26, 35, and 40 parts per thousand), pH (3.3, 6.5, 7.7, 8.1, and 9.2), and light intensities (strong 2 100 lx and weak 60 lx) at various body weights (3.0, 3.7, 4.3, 5.7, 7.8, 9.0, 9.5, 10.7. 11.9, and 13.3 g) and feeding conditions (fed for 3 h, fasted for 12 h, and fasted for 48 h) to hypoxic stress was measured. Regression models for the effects of body weight, temperature, salinity, and pH on lethal dissolved oxygen (DO) levels were derived from the data. Body weight, temperature, salinity, and pH had significant effects on lethal DO levels (P < 0.01). The estimated body weight (BW), temperature (7), salinity (S), and pH (pH) for minimum lethal DO levels (LDOL) were 9.17 g, 22 degrees C, 16.6 parts per thousand, and 7.56 (LDOL = 0.0076 BW2 - 0.1394 BW + 1.1471, r(2) = 0.94; LDOL = 2.4291 x 10(-5) T-3 - 0.0008 T-2 + 0.6095, r(2) = 0.66; LDOL = - 7.8212 x 10(-5) S-3 + 0.0058S(2) - 0.1280 S + 1.2424, r(2) = 0.98. LDOL = 0.1487 pH(2) - 2.2488 pH + 8.8806, r(2) = 0.99), respectively. The lethal DO levels of the shrimps exposed to strong light (2100 lx) were 75.1% of those exposed to weak light (60 lx), but there was no significant difference (P > 0.05) between the two light intensities. The lethal DO levels of the shrimps fed for 3 h were 80.6% of those fasted for 48 h (P < 0.01), but no significant difference (P > 0.05) was found between those fed for 3 h and fasted for 12 h. These results indicated that L. vannamei cultured at optimum conditions has the best ability to withstand hypoxia. Therefore, it is suggested that water temperature be maintained at 22 degrees C, salinity 16.6 parts per thousand, pH 7.56, and strong light conditions for water management practice in L. vannamei culture when hypoxia happened. (c) 2006 Elsevier B.V. All rights reserved.