acre. In the pond with no predator control, the total 

 harvest was 44 pounds (20 kg) of 70 count shrimp per 

 acre, which is probably about the natural productiv- 

 ity of unmanaged marshes. 



In a study of the penaeid shrimp, Pemieiis 

 ifiaifiinatus, aimed at developing techniques for in- 

 tensive cultivation under manipulated environmen- 

 tal conditions, investigators at the University of 

 Hawaii have successfully spawned females and 

 reared the larvae through all stages. A new, 

 intensive-culture enclosure is being built that will 

 boost production by vertically arranging the shrimp 

 in small cages on frames, so as to allow the use of the 

 entire water column. Also, a shrimp nutrition study 

 is underway. This project is to provide the technical 

 information needed for a commercial-scale opera- 

 tion to be established and operated by a community 

 group in Hawaii. 



Biologists and food scientists at Louisiana State 

 University are developing new rations (foods) for 

 crustaceans in culture. Emphasis has been on the 

 utilization of products such as crustacean meals, 

 single-cell protein (torula yeast), food processing 

 "waste" fiber and cellulosic products, and other 

 products of the fishery processing industries. Spe- 

 cial attention is being given to the evaluation of 

 the nutritional value of sun-dried shrimp meal and 

 other shrimp meal prepared by various processing 

 procedures. These rations will be tested for feeding 

 efficiency rates, durability and acceptability, and the 

 effect of various attractants to stimulate shrimp feed- 

 ing will be identified. A suitable ration which uses 

 alginates as a pellet binder has been developed and is 

 being evaluated under a range of environmental con- 

 ditions. Other hydrocolloids and modified starches 

 are also being evaluated as pellet binders. Experi- 

 mental samples are being made available to inves- 

 tigators for testing on a range of economically valu- 

 able crustacean species, i.e., penaeid shrimp, 

 freshwater shrimp, and crawfish. 



A part of this project includes work to prepare the 



feeds developed as microcapsules in varying sizes 

 and densities according to the stage of development 

 of the animal. Forexample. the feed forthe nauplius, 

 zoea, mysis, and early postlarval stages will be small 

 and have near-neutral buoyancy, whereas that for 

 the late postlarval and juvenile stages would be 

 larger, would sink, and exhibit good water stability. 

 Although the microcapsules are expensive initially. 

 they should result in healthier animals and greater 

 survival through provision of all nutritional require- 

 ments and controlled amounts of expensive sophis- 



ticated chemicals (hormones, antibiotics, stimu- 

 lants, etc.). Use of the microcapsules will also re- 

 lieve the culturist from the tedious and expensive 

 algal cultural systems now employed in most aqua- 

 culture operations. 



Another study into the environmental and nutri- 

 tional requirements of shrimp in culture is being 

 carried out at the Skidaway Institute of Oceanog- 

 raphy in Georgia. Following a series of experiments 

 which established a suitable water flow rate, type of 

 substrate, oxygen level, stocking density, and light 

 intensity, preliminary nutritional studies using 

 purified pelleted diets were conducted. Eighteen dif- 

 ferent diets which varied in level and quality of pro- 

 tein, carbohydrate, lipid, vitamins, and minerals 

 were evaluated by growth rate and percent survival. 

 Rates of ingestion under given environmental condi- 

 tions, rates of assimilation of specific biochemical 

 entities and calorie-protein relationships are now 

 being investigated. To date, a semipurified diet, con- 

 taining about 70% shrimp meal and 8% anchovy 

 meal, fed at a rate of 15% of the total biomass daily 

 has produced the best results (164% increase in 

 weight with 95-100% survival during a 3-mo period). 



Crabs 



Mass culture techniques to produce large numbers 

 of larval stone crabs, Meiiippe mercenaria. and blue 

 crabs, Calliiiectes sapiclus, have been achieved in a 

 project at the University of Miami. However, tech- 

 niques must be improved to reduce and control the 

 problem of cannibalism among larval stone crabs. 

 The stone crab matures, copulates, and spawns via- 

 ble eggs under conditions of captivity. P., offspring 

 of blue crabs have also been attained in captivity. 

 Investigations are now underway to improve techni- 

 ques of larval culture and to test feasibility of rearing 

 crabs to marketable size in cages placed in natural 

 waters. 



A Samoan or mangrove crab, Syclla seirata. has 

 been studied at the Hawaii Institute of Marine Biol- 

 ogy. The Samoan crab has been maintained in cages 

 suspended from rafts and its growth rate measured. 

 This study indicated this crab could attain market- 

 able size of 1 - 1 '/2 pounds (0.5 - 0.7 kg) in about 1 Vi 

 yr at ambient temperatures (24°C). Tests at higher 

 temperatures (27°C) indicated that the time to reach 

 market size could be reduced to 1 yr. Also, a diet of 

 artificial food resulted in faster growth than natural 

 foods. 



In another crab culture project, efforts are under- 

 way at Humboldt State College in northern Califor- 



43 



