GROWTH AND SURVIVAL OF POSTLARVAL PENAEUS AZTECUS UNDER CONTROLLED CONDITIONS OF TEMPERATURE AND SALINITY

¹ Bureau of Commercial Fisheries, Galveston, Texas

1. The combined effects of salinity and temperature upon growth and survival of postlarvae of the brown shrimp, Penaeus aztecus, were studied under controlled conditions.

2. Test salinity ranged from 27 to 40 and temperature from 7° to 35° C.

3. With relatively short periods of acclimation, postlarval brown shrimp withstood wide fluctuations in both temperature and salinity for 24 hours.

4. The range of tolerance to these factors over periods of 28 days was only slightly less than that observed for 24 hours.

5. Postlarvae survived temperatures as low as 11° C. with almost no growth for one month in salinities of about 15 or above.

6. Growth increased with temperature, with significant growth beginning at some temperature above 11° C. but below 18° C. The most marked increase in growth rate occurred in the temperature region between 11° and 25° C.

7. At temperatures below 15° C., young (postlarval) shrimp demonstrated a decreased tolerance to low salinity. This reduced tolerance may influence the natural distribution and survival of postlarvae, which do not ordinarily enter the estuaries in abundance until spring when the temperature has increased to levels at which characteristically low estuarine salinities are no longer harmful.

8. Salinity per se had little effect on either survival or growth, except at extreme temperatures.