escape problem is a cover over the system. However, such a design may change 

 the cause of mortality from escape and desiccation to cannibalism. 



Each of these systems emphasizes low maintenance and unlimited scale-up 

 potential. Care was taken during the design phase to avoid sharp corners, excess 

 mesh area, or eddying currents. Hartman (2) has shown that brachyuran larvae 

 become impinged in corners that break spines or setae and impede molting. He 

 also mentioned the importance of tapered walls so that larvae and food do not 

 become caught in eddying currents. 



Even with these problems, survival of all life stages has been high. Larvae 

 cultured in the beaker systems have shown approximately 70 percent survival 

 when fed Artemia nauplii in excess. In this experiment, survival of juveniles 

 and adults reared in the 20 C hatching jar was 75 percent (since 

 metamorphosis) over a 14 week period. The diet studies have shown similar 

 survivals in smaller cultures. 



Several other comments are worthy of mention. The ages at transfer from 

 one system to another represent the schedule used in this study and most Ukely 

 could be altered without problem. Also, one key factor to consider in the two 

 C and four C flow-through systems and the hatching jars, is mesh size. A mesh 

 should be chosen that will permit debris to pass through, yet retain both larvae 

 and food organisms. For these reasons a 243 or 400 jum mesh was used. 



Use of ^. salina nauphi as a diet for larval grass shrimp has been 

 substantiated by several investigations (1, 6). The study by Broad (1) 

 confirmed that diets including brine shrimp were more successful in terms of 

 survival and development than diets lacking this animal tissue. Provenzano and 

 Goy (6) established the possibility of using Artemia from several locations, 

 including San Francisco, Canada and, to a lesser degree, Utah. 



Establishment of a laboratory population of grass shrimp should lead to 

 increased use of the animal in bioassays. Nimmo et al (5), based on cadmium 

 bioassays, concluded that adult P. vulgaris were "acutely and chronically" 

 more sensitive than the pink ^hxivcvp , Penaeus duorarum. Studies by Shealy and 

 Sandifer (7) have shown the susceptibility of P. vulgaris larvae to mercury. 

 Conversely, Vernberg et al (8) reported that P. pugio is quite resistant to 

 cadmium bioassays. Apparently animal age and species are important; P. 

 vulgaris may prove to be a better pollution indicator than P. pugio. 



REFERENCES 



1. Broad, A.C., 1957. The Relationship Between Diet and Larval Development 

 oiPalaemonetes. Biol. Bull. 1 12:162-170. 



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