Photoperiod and tempertiture control plus endocrinological 

 manipulations have been used experimentally to induce sexual 

 maturation and spawning in crustaceans. These and other culture 

 techniques must be refined to produce seed stock reliably on 

 demand. Genetic research is needed to define strain 

 characteristics of cultured crustacean stocks, to improve growth 

 rates, increase disease resistance, and reduce aggression and 

 cannibalism. Lobsters and crabs are particularly aggressive and 

 cannibalistic, making viable commercial culture difficult. These 

 two valuable crustaceans are not yet cultured economically. 



Other Organisms 



Additional species which have interested aquaculturists include 

 eels, frogs, alligators, marine baitworms, and aquatic plants. Eel 

 culture is still dependent upon the capture of elvers (juvenile 

 eels). Techniques to induce maturation and spawning have not yet 

 been developed. Frogs, alligators, and turtles are not 

 conventional aquaculture species, but are being cultured on a 

 limited basis under controlled conditions. Not all breeding and 

 rearing problems have been solved and essentially no work has been 

 done to characterize genetic traits which would be valuable to 

 aquaculturists. Culture techniques for marine baitworms have only 

 recently been developed and further refinement would be expected 

 only if commercial production were to begin. 



Several species of freshwater and marine aquatic plants are 

 cultured commercially in various parts of the world. Culture 

 techniques range from simply fertilizing and seeding tanks or ponds 

 with single cell algae or higher vascular plants, to the more 

 complex culture of red and brown marine algae. Marine algae may be 

 cultured on the seabed but more frequently are cultured on floating 

 or hanging support structures. Most breeding and culture 

 techniques in the U.S. are still rather primitive. 



Nutrition and Diets 



Natural Foods 



Most aquatic animals require living organisms for food during some 

 stage of their life cycle and a few species require living 

 organisms throughout their entire life. Some species will feed 

 only on moving organisms, which indicates that the requirement for 

 living organisms in their diet is more behavioral than nutritional. 



Natural foods include bacteria, algae, protozoans, zooplankton, 

 other macroinvertebrates, and larger forage animals. Fertilizers 

 are commonly used to stimulate the production of these natural 

 organisms. However, the species composition of fish food organisms 

 is difficult to control, and physical influences, such as 

 temperature, dissolved oxygen, and light intensity may affect the 

 standing crop. Particular care must be taken to limit the growth 



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