Thermal acclimation capacity and standard metabolism of the Pacific white shrimp Litopenaeus vannamei (Boone, 1931) at different temperature and salinity combinations.

In aquatic environments, rising temperatures reduce the oxygen content of the water while increasing the oxygen demand of organisms. In intensive shrimp culture, it is of great importance to know the thermal tolerance of cultured species and their oxygen consumption since this affects the physiological condition. In this study, the thermal tolerance of Litopenaeus vannamei was determined by dynamic and static thermal methodologies at different acclimation temperatures (15, 20, 25, and 30 °C) and salinities (10, 20, and 30 ppt). The oxygen consumption rate (OCR) was also measured to determine the standard metabolic rate (SMR) of shrimp. Acclimation temperature significantly affected the thermal tolerance and SMR of Litopenaeus vannamei (P < 0.01). Salinity had a large effect on SMR (P < 0.01) but did not influence the thermal acclimation of the shrimp (P > 0.01). Litopenaeus vannamei is a species that has high thermal tolerance and can survive at extreme temperatures (CTmin-CTmax: 7.2-41.9 °C) with its large dynamic (988, 992, and 1004 °C2) and static thermal polygon areas (748, 778 and 777 °C2) developed at the above temperature and salinity combinations and resistance zone (1001, 81 and 82 °C2). The optimal temperature range of Litopenaeus vannamei is the 25-30 °C range, where a decrease in standard metabolism is determined with increasing temperature. Given the SMR and optimal temperature range, the results of this study indicate that Litopenaeus vannamei should be cultured at 25-30 °C for effective production.

Thermal tolerance of Acartia tonsa: In relation to acclimation temperature and life stage.

The Acartia tonsa, a calanoid copepod species, has high survival and thermal acclimation capacity in aquatic environments characterized by temperature variations. Dynamic and static thermal polygon areas of this species are 495 °C2 and 267 °C2 for nauplii stage, while adult stage has 747 °C2 and 411 °C2 dynamic and static thermal polygon area, respectively. In addition, Acartia tonsa is a copepod species which is more resistant to both high and low lethal temperatures, with its resistance zone of 105 °C2 and 131 °C2 for nauplii and adults, respectively. Acartia tonsa nauplii acclimated to 18 °C, 23 °C and 28 °C have lover and upper thermal limit (CTMin-CTMax) of 6.82-26.15 °C, 8.65-29.49 °C, and 11.70-34.10 °C, respectively. This species in the adult stage has a CTMin-CTMax of 4.47-30.30 °C, 6.35-33.94 °C, and 9.92-35.90 °C at acclimation temperatures mentioned above. Its broad dynamic and static thermal tolerance polygon areas and, accordingly, its significant thermal limits allow Acartia tonsa to survive at warm or cold extremes in their natural environment.

Thermal tolerance and preferred temperature range of juvenile meagre acclimated to four temperatures.

The present study reports the temperature tolerance, estimated using dynamic and static methodologies, and preferred temperature range, based on oxygen consumption rate (OCR), of juvenile meagre (Argyrosomus regius) (Asso, 1801) (3.4±0.9g) after 30 days of acclimation at 18, 22, 26 and 30°C. Meagre has dynamic and static thermal tolerance zones of 551°C2 and 460°C2, respectively and is a low resistance fish species, with a resistance zone area of 87°C2. The OCR of juvenile meagre at the above acclimation temperatures was 370, 410, 618 and 642mgh-1kg-1, respectively, and is significantly different (P<0.0001, n=20). The fact that OCR increases by rising temperatures and gradually decreases after 26°C indicates that the preferred temperature range of juvenile meagre is between 26 and 30°C. Our study suggests that meagre is unable to respond to low and high temperature variation in aquaculture facilities or its natural habitats.