.^K 



just as frequently as they chose more 

 saline levels, up to and including the 

 30%c-34'/oo range. (See figure next 

 page. ) Maximum concentrations oc- 

 cupied by individual shrimp varied 

 from 49'/oD to TOyoo, and minimum con- 

 centrations from l%o to 10%o, again 

 indicating widely separated avoidance 

 limits for this species. 



Small (1-in.) brown shrimp swim- 

 ming in experinnental salinity gra- 

 dient. The horizontal reference line 

 just below the shrimp indicates the 

 21%o level; the next line above marks 

 the 13%o level. 



The influence of acclimation to high or low salinities is suggested 

 by the results of similar experiments which tested two shrimp grown at 5%o 

 and two held for 3 days at 53%o-54'/oo. The obvious differences between fre- 

 quency distributions of these two groups seenn to reflect the salinity history 

 of the experimental animals. Moreover, data for the low-salinity group are 

 much less widely distributed than are those for the high-salinity group. The 

 small number of shrimp tested to date, however, limits the confidence with 

 which these differences can be associated with salinity acclimation. 



Present plans are to repeat this type of work in order to determine 

 the extent of behavior variability within and between individuals. Future work 

 will also extend this approach to other species, beginning w^ith white shrimp, 

 and to another important environmental factor - temperature. 



A study of the effect of salinity and temperature on survival of small 

 brown shrimp has also been undertaken. Using five incubators, 24-hour sur- 

 vival tests involving a two-factor, five-level experimental design were con- 

 ducted with postlarvae and juveniles. Within each experiment, initial salinity 

 and temperature conditions (25%o-27%o and 22 ''-25" C. , respectively) were the 

 same for all shrimp. Changes to final experimental conditions were made 

 over a 12-hour period for each group by making periodic changes until the 



desired conditions were obtained. 



58 



