vival and yields in ponds, tanks, and cages, and to 

 further develop techniques for pond management, 

 including procedures for assuring adequate oxygen 

 supply and optimization of other pond conditions 

 such as bottom material, depth of water, and fer- 

 tilizer regimen. Other efforts are underway on rapid 

 and efficient harvesting techniques, cage culture, 

 and testing of the important variables in the culture 

 system such as food types, stocking density, and 

 feeding methods. 



A new rotatable cage for high density culture has 

 been designed. It is intended to solve the problem of 

 fouling of the mesh. Every portion of the cage is out 

 of the water for about half the time where it is ex- 

 posed to sunlight and drying and can be easily 

 cleaned. It is not necessary to handle the animals in 

 order to clean the cage. Harvesting w ill also be great- 

 ly simplified by this design. 



In a related project at Miami, attempts are being 

 made to induce maturation of ovaries and oocytes m 

 pink shrimp. Penaeus duororuin . This is a necessary 

 step in the control of the life cycle of the animals in 

 captivity w hich will relieve the commercial culturist 

 from his dependency on wild populations for gravid 

 females as the source of fertilized eggs. The research 

 to date has included efforts to develop various mea- 

 sures of maturation and investigation of factors (light, 

 temperature, salinity, and hormones) which enhance 

 maturation by inhibiting molting. 



Another project at Miami, aimed at the general 

 objective of life cycle control of shrimp, involves the 

 development of techniques to attain in vitro fertiliza- 

 tion of ova and sperm removed from ripe animals. 

 Included in this investigation are in vitro studies of 

 maturation of oocytes and ovaries, effects of hor- 

 mones and ovarian extracts on maturation of ovarian 

 cells, and development of cryogenic techniques to 

 preserve viabilit\ of ova and sperm, fertilized eggs, 

 and cultured ovarian colls. Biochemical studies of 

 gonad maturation are underway using electrophore- 

 tic profiles to assess maturity. 



Aquacultural research at Texas A&M University 

 is aimed at shrimp farming as a commerically feasi- 

 ble operation. Twenty '/2-acre ponds (0.2 hectares) 

 are used for study of artificial feeds, shrimp stocking 

 rates, mortality, and growth rates. Some ponds are 

 stocked with hatchery-reared postlarval brown 

 shrimp. P. (iztcciis. supplied by the Dou Chemical 

 Company. Yields from 1970 harvests averaged 2.'>0 

 pounds of shrimp per acre (2S0 kg/ha), with some 

 ponds exceeding 450 pounds per acre (.'^04 kg/ha). 

 The wholesale market price of the shrimp at harvest 



ranged from SO. 65 to 50.85 per pound, heads on 

 (465-608 yen/kg). In cooperation with Ralston 

 Purina, new feed rations have been developed. Har- 

 vesting of the 1971 crop, now in progress, should 

 also reveal effects of pond fertilization on growth 

 rates and survival. 



Other shrimp research at Texas A&M includes 

 studies on temperature and salinity etTects on post- 

 larvae and feeding behavior, and diet preference of 

 postlarvae. To date one phase of this research has 

 provided information regarding upper incipient 

 lethal temperature, acclimation rate to temperature 

 change, and the influence of environmental salinity 

 on heat tolerance of postlarval brown shrimp. Pres- 

 ent work will extend results to include white shrimp 

 P. setifents. postlarvae. Differences have been 

 demonstrated between the responses to diets of 

 postlarval brown and white shrimp. It was shown 

 that shrimp responses to foods, including initial diet 

 preference, survival, growth, and resistance to 

 high temperature may vary independently. 



The 4.700 square miles (12. 17.^ km-) of brackish to 

 marine marshlands and 1.600 square miles (4.144 

 km-) of bays, estuaries, bayous, and canals in south- 

 ern Louisiana are potential sites for impoundments 

 for mass culture of brown and white shrimp without 

 supplemental feeding. A research program being 

 conducted by biologists from Francis T. Nicholls 

 State University has been attempting to solve the 

 many problems involved in demonstrating that such 

 a system is feasible. Two shallow. 10-20 acre (4-8 ha) 

 impoundments containing water and Spartina 

 patens marsh are being used to determine the basic 

 productivity (shrimp production) and for measure- 

 ments of the effect of fish and crab predator control 

 on shrimp production. Natural stocking of ingress- 

 ing postlarval shrimp occurs on nighttime flood 

 tides across weirs in the impoundments. Large 

 shrimp and predators are prevented from entering by 

 hardware cloth screening. 



Predator control is exercised in the larger, test 

 impoundment by rotenone application for fish and 

 baited wire traps for blue crabs. Efficient harvesting 

 of the ponds consists of draining surface water at 

 night across the weir into a net. Shrimp of commer- 

 cial size rise to the surface and migrate out o^ the 

 cstuarine areas and into the Gulf at night during ebb 

 tides. With predator control the brown shrimp grew 

 to .^4 count (heads on) in 75 days and to 12 count in 

 200 days; the white shrimp grew to .^4 count in 60 

 days. The total harvest of both species for one sea- 

 son was 125 pounds (57 kg) of .''4 count shrimp per 



42 



