were either partially or completely cramped in 2°/ooS. In cramped 

 shrimp the abdominal muscles tightened up, drawing the abdomen either 

 slightly or completely forward (Fig. 3c). When cramped the shrimp 

 balanced on the tips of the telson, uropods and periopods or fell on 

 their sides. These shrimp were very inactive and at times appeared 

 paralyzed except for slight flickering movements of the pleopods. 

 In 2°/ooS more than half died within 15 hours and all the shrimp 

 died by the second day. Cramping also occurred in 5°/ooS within 

 one hour after transfer; seven shrimp were dead by the second day. 

 It is interesting to note that this condition did not occur in sa- 

 linities 10°/oo and above. In general the shrimp acclimated to 

 32°C survived better in the entire salinity range than did those 

 acclimated to 18°C. But disregarding the temperature, brown shrimp 

 survived in larger numbers in 15°/ooS and above than in lower sa- 

 linities (Table 1) . 



Effect of salinity and temperature change 



A simultaneous change in salinity and temperature conditions 

 influenced the response and survival pattern more than a single 

 parameter. Brown shrimp acclimated at 25°C and transferred to 18°C 

 appeared normal in 10, 15, 25, and 36°/ooS and survived well. The 

 single death recorded in 36°/ooS was a case of attack on a freshly 

 molted shrimp. However, there was an initial hyperactivity in 

 2°/ooS for two hours and in 5°/ooS for ten minutes. In 2°/ooS 

 seven shrimp were cramped within five hours. Within 24 hours half 

 of the shrimp were dead and the others severely stressed. In 5°/ooS 

 two shrimp were cramped within five hours and half of the test animals 

 were dead after the first day. 



When transferred to 32 °C from 25 °C the shrimp were hyperactive 

 in 2, 5, 10, and 15°/ooS but were normal in 25 and 36°/ooS. The 

 duration of hyperactivity decreased with increasing salinity, rang- 

 ing from four hours in 2°/ooS to 1/2 hour at 15°/ooS. Three shrimp 



53 



