Table 9.- -Percentage survival of postlarval white shrimp at various 

 combinations of temperature and salinity 



« = survival of 80 percent or more. 

 - = survival less than 80 percent 

 = conditions not tested. 



estuary to water of lower salinity than that 

 entered by brown shrimp. 



Results of previous experiments suggested 

 a shift in salinity and temperature tolerance 

 during the early postlarval life of brown shrimp. 

 We designed a study to investigate this hypoth- 

 esis by using laboratory-hatched postlarval 

 brown shrimp. Tests were made at weekly 

 intervals for 3 weeks to determine the 80- 

 percent survival limits. Results indicated that 

 as postlarval shrimp became larger (or older) 

 they survived a wider range of salinities. 



In the second experiment, laboratory- 

 hatched brown shrimp were held at 11° C. 

 (52° F.), 18° C. (65° F.), 25° C. (77° F.), and 

 32° C. (89° F.) at various salinities. Best 

 growth occurred at 32° C. (89° F.). At 11° C. 

 (52° F.), all animals were dead within 12 days. 

 Shrimp survived best at 25° C. (77° F.) at all 

 salinities except 2 p.p.t., the lowest salinity 

 tested. Survival at 2 p.p.t. was poorer than in 

 previous experiments. This possibly is ex- 

 plained by the small initial size of the post- 

 larvae (6 mm. total length; 1/4 inch) as com- 

 pared with 8- to 12-mm. (3/8- to l/2-inch) 

 shrii-np collected from the surf for previous 

 experiments. 



Effect of Container Size 



One experiment was inade to determine the 

 effect of container size (volume and surface 

 area) on growth and survival of postlarval 

 brown shrimp. We kept 100 shrimp in each of 

 five containers of different dimensions for 

 1 month. Water volume and dimensions of the 

 containers are given in table 10. At the end of 

 the month, all animals were weighed and 

 measured. There was no difference inaverage 

 size of the animals from four tanks with vol- 

 unnes of 22 to 44 liters, but the animals in the 

 4-liter tank were significantly smaller than 

 any of the others. Survival in all containers 

 was above 80 percent. 



George W. Griffith, Project Leader 



Growth 



We conducted 30-day growth experiments 

 with two groups of laboratory-hatched post- 

 larvae. The first study was made with white 

 shrimp held at temperatures of 15° C. (59° F.), 

 18° C. (65° F.), 25° C. (77° F.), and 33° C. 

 (91° F.) at selected salinities. As with animals 

 collected in nature, animals grew faster at the 

 higher water tennperatures. Survival was poor- 

 est at 15° C. (59° F.); most shrimp died before 

 the end of the experiment. 



GULF OCEANOGRAPHY PROGRAM 



The Gulf Oceanography Program was con- 

 ceived in late 1965 and is concerned with 

 determining the physical factors significant to 

 shrimp in the natural environment of the Con- 

 tinental Shelf and slope and the atmospheric 

 and Qceanographic processes that influence 

 that environnnent. We need to examine the 

 short- and long-term changes of the water 

 environment over the shelf, and the relation of 

 these variations to the general dynamics of the 

 Gulf and to the atmospheric conditions through- 

 out the Gulf. Further, the sedimentary environ- 

 ment on the shelf and slope must be defined 

 and related to the prevailing water conditions 



and the biological environnnent. The essence 

 of our effort is to evolve techniques that allow 

 us to forecast the state of the environment. 



The field program became effective near 

 the beginning of the fiscal year when the R/V 

 Geronimo was transferred to the BCF Labora- 

 tory in Galveston. During the year the vessel 

 completed three sedimentary surveys of the 

 shelf and three hydrographic cruises, including 

 one of the entire Gulf of Mexico and one cooper- 

 ative cruise with Texas A&M University. In 

 addition, a detailed study of the sediments 

 within the shrimp grounds off Galveston was 

 started. Bottonn sediments on this study were 



30 



