RESULTS AND DISCUSSION 



Attempts to culture and maintain a laboratory population of P. vulgaris 

 have been successful thus far. Ovigerous females were obtained from adults 

 hatched in the laboratory and cultured for 90 days. These egg-bearing females 

 have yielded morphologically normal larvae, thereby indicating that the eggs 

 resulting from lab-reared females are viable. After 16 months of culture, a total 

 of 21 ovigerous females have been collected from the system. Six of these 

 shrimp are females that also bore eggs in the first laboratory spawning season 

 (November, 1976 to January, 1977 or 9 to 10 months ago). Problems in 

 controlling photoperiod and water temperature have limited successful hatches 

 to only two females. Little (4) has discussed how manipulation of these two 

 environmental factors can be used to induce winter breeding in grass shrimp. 



The diet study (Table 14-1) has indicated on a gross scale that a flake food 

 can be used as a diet. Ovigerous females were collected from the four 6 

 flow-through systems used for both the brine shrimp and Tetra Marin diets. 

 Therefore, growth, survival and reproduction are acheivable with the live and 

 dried foods. 



All of the systems and techniques mentioned herein have yielded 

 satisfactory results. However, some minor problems remain. One such problem 

 is cannibahsm, especially in the 20 and 48 C hatching jars used as holding tanks 

 for juvenile and adult grass shrimp. Obvious solutions include increasing the 

 food available, either as more food per day, or as multiple daily feedings, or 

 decreasing the density of shrimp. A certain degree of cannibahsm is to be 

 expected in mass cultures during periods of molting. 



A second problem, also in the hatching jar systems, relates to the physical 

 design of the container. The concave bottom of the jar, coupled with a circular 

 flow, causes a centrifuging of the shrimp into the center near the bottom. A 

 flatter bottom with a larger bottom surface area to volume ratio could be a 

 solution. The 40 C kriesel systems (3) used in lobster culture efforts have the 

 desired flatter bottoms, and also jetted water inflow along the sides that create 

 a more uniform distribution of the shrimp. Preliminary studies indicate 

 that the kriesel design will be very successful for juveniles and adults. 

 Compared to growth in the four C beaker systems (See Table 14-1), the kriesel 

 has yielded significantly higher growth rates. Mean carapace length in the 

 kriesel after nine weeks was 6.8 ± 0.69 mm (range 5.9 to 7.9 mm), a size not 

 attained until an age of about 20 weeks in the beaker. 



One last problem is animals flipping out of the systems, especially the 48 C 

 jar. This appears to happen in conjunction with a molt, and the subsequent 

 cannibalism pressure from other shrimp in the system. A simple solution to the 



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