polyurethane carboys used as culture vessels, 

 16,000 postlarvae were produced; 3,396 were 

 reared in one carboy. These larvae were 

 cultured at a temperature of 28.5° C, and 

 salinity was maintained at 30 p.p.t. by addition 

 of artificial sea salts to 24 p.p.t. sea water 

 from the laboratory's recirculating sea-water 

 system. The first postlarvae were found late 

 on the eighth day after hatching. A series of 

 larvae was preserved for future morphological 

 studies. 



Before the successful culture of white shrimp 

 larvae, we nnade two attempts to obtain viable 

 eggs of this species. Four pairs of shrimp 

 were placed in each of two 555-liter tanks 

 during the first trial. They spawned between 

 10:30 and 11:00 p.m. The females did not have 

 an externally attached spermatophore, and 

 spermatophore transfer did not take place prior 

 to spawning. As soon as eggs were seen, 

 spermatophores were taken from several 

 males, opened, and the sperm placed in the 

 tanks with the eggs. The eggs in this experi- 

 ment appeared normal, but they did not develop 

 to the point where nauplii could be distinguished 

 within them. For the second trial, three fe- 

 males, without attached spermatophores, were 

 placed in each of three tanks. Males were not 

 placed in the tanks. Spawning occurred in only 

 two of the tauiks, again between 10:30 amd 

 11:00 p.m. Sperm was imnnediately added to 

 one tank but not the other. Eggs in both tanks 

 developed to a point where nauplii could be 

 seen moving inside the eggs but they did not 

 hatch. The salinity in the tanks was 18.4 p.p.t. 

 which might have been too low for hatching. 



Larval Food Cultures 



We have been growing Skeletonema in open 

 cultures (up to 74 liters) in filtered estuarine 

 water and different additives. During the 

 summer and early fall, this diatom was cul- 

 tured by adding the metal chelator EDTA 

 (Ethylenediaminetetraacetate) to the water, 

 but beginning in October it could no longer 

 be cultured in this manner. We have since 

 learned that additions of commercial fer- 

 tilizers, iron, and EDTA to estuarine water 

 will support growth of Skeletonema in the late 

 fall. 



Because the quality of the water varies 

 during the year, we have begun a series of 

 experiments to determine which additives 

 must be used to obtain the best growth of 

 Skeletonema as water conditions change. Test- 

 tube cultures are started every 4 to 6 weeks 

 with the following additives in varying com- 

 binations: nitrate and phosphate, EDTA, iron, 

 and a trace-metal mixture. The nitrate and 

 phosphate, EDTA, and trace-metal combina- 

 tion gave the best growth in April; trace 

 metals were not needed in May and June. 

 Eventually, one should be able to make this 

 determination in 3 days with only a few tubes. 



In the summer of 1965, we found that Skele- 

 tonema in a rapidly growing culture used about 

 100 //g.at./l. (microgram atoms per liter) of 

 nitrate per day. The nitrate -phosphate ratio 

 was 20 to 1, KNO3 andNa2P04 have been added 

 to the cultures daily to supplythese quantities. 



A colorimeter is used to monitor the diatom 

 cultures, and in the large cultures, we try to 

 keep the density near a colorimeter unit count 

 of 100 (about 250,000 chains per milliliter). 

 In our last culture, two -thirds of the culture 

 volume was drawn daily. Each culture is 

 usually kept only 8 to 10 days. 



Harry L. Cook, Project Leader 



CULTIVATION OF SHRIMP IN 

 ARTIFICIAL PONDS 



Postlarval brown shrimp for our pond studies 

 were collected from the Galveston Pass as they 

 migrated into the bay. These shrimp were 

 separated from accompsmying organisms and 

 stocked in two 1/20-hectare (l/8-acre) 

 shallow-water ponds at the rate of 9,000 post- 

 larvae per pond. In one pond, water was ex- 

 changed continuously, and the shrimp were 

 fed a prepared diet. In the other, we added 

 water only to compensate for loss fronn 

 evaporation and seepage, and adjusted the 

 pond's fertility by adding inorgemic fertilizer 

 to promote plankton growth. Shrimp were 

 taken from each pond each week, weighed, 

 nneasured, and returned. 



During a 95-day period (March 31, 1965, 

 to July 4, 1965), shrimp stocked in the 

 circulating-water pond grew steadily, attaining 

 an average total length of 97.4 mm. aind an 

 average total weight of 6.08 g. Average daily 

 growth was .88 mm. in length and .06 g. in 

 weight. This study was ended prematurely by 

 heavy mortality as a result of a dense bloom 

 of algae accompanied by high water tempera- 

 tures, poor circulation, and continuous heavy 

 cloud cover for 2 days. On the basis of the 

 projection of the weights of dead shrimp re- 

 covered from the banks and water's edge (dead 

 shrimp on the bottom of the pond were not 

 recovered), the total production of shrimp was 

 38 kg. per hectare (207 pounds per acre). 



Shrimp in the static -water pond did not grow 

 as well as those in the circulating pond. In 

 120 days, shrimp grew to an average total 

 length of 79.6 mm. and an average total weight 

 of 3.45 g. Shrimp growth, characterized by 

 initial rapid gains, retardation, and finally 

 cessation, appeared to depend on the density 

 of plcinkton. Although one -half of the popula- 

 tion was removed 1 month after growth had 

 stopped, the remaining Shrimp continued to 

 lose weight. The addition of fertilizer, how- 

 ever, restimulated plankton growth, and the 

 shrimp began to gain weight. Projection of 

 the weights of shrimp harvested resulted in an 



