Table 2. — Continued. 



1971 



Month 



Day 



Hour 



Larval 

 stage 



Algae 



Larval 

 count 



Residual 



Feed 



Anemia 



Residual Feed 



May 



31 



0800 



June 



Mysis III 



4().()()() 



No. cellslml 



35,000 S 

 33.750 T 



27,500 S 

 38,750 T 



37.500 S 

 21.250 T 



No. cells 

 fedlml 



135,000 S 

 89.750 T 



127,500 S 

 86,750 T 



No. /ml 

 5.0 



6.8 

 8.0 



8.0 



8.8 



Of the 84,000 nauplii which hatched, 71% reached 

 the mysis stage. Once again, owing to a buildup of 

 algal food on the bottom, water fouling caused high 

 mortalities. From mysis 1 to mysis II, thoseArtemia 

 fed to the shrimp were eaten; however, from mysis 

 II to postlarvae I, Xhe Artemia begin to graze quite 

 heavily on phytoplankton and some grew so rapidly 

 that the larval shrimp could not eat them. It was then 

 necessary to build the Artemia level higher in order 

 to have enough available to feed the young 

 shrimp. 



Not only was fouling on the bottom a problem, but 

 from the mysis stage on, the shrimp tended to ac- 

 cumulate at the bottom of the tank where the fouling 

 was occurring, thus increasing the stress upon the 

 population. Only 48*^ of the initial population 

 reached the postlarval stage. 



The second of the two tanks was used to test a 

 small peristaltic pump set up for feeding continu- 

 ously the algal concentrate into the larval culture 

 tank (Table 3). Unfortunately, enough Skeletonema 

 had not been concentrated and frozen for this tank, 

 so concentrated frozen Skeletonema was used in the 

 continuous feeder and concentrated fresh 

 Skeletonema was used for the initial feeding and for 

 supplemental feedings needed to raise the standing 

 cell level. At times the automatic feeder was pump- 

 ing too fast, so it was shut off or the food concentra- 

 tion was reduced. 



On 28 May. it was necessary to transfer about half 

 of the population from this lank for an additional 

 experiment, leaving 42.750 mysis Is in the tank. 



Survival was good from mysis I to postlarvae II. 

 However, when this tank was harvested, an accumu- 

 lation of debris had built up on the bottom of the 

 tank, with dark areas of decomposition, indicating 

 hydrogen sulfide production. In more recent work 

 using airlift pumps to keep the debris suspended, the 

 problems related to the accumulation of debris on 

 the bottom have been solved. 



By careful measurement of the abundance of the 

 larval shrimp populations as well as the densities of 

 food organisms at regular intervals, biologists have 

 been able to learn much concerning the survival, 

 behavior, and environmental requirements of larval 

 shrimp. While these methods may or may not have 

 commercial applications, they are a useful research 

 tool. 



LITERATURE CITED 



BROWN, A, JR. 



1972. Experimental techniques for preserving diatoms 

 used as food for larval Pciiiieiis uzleciis. Proc. Natl. 

 Shellfisheries Assoc. 1971. 62:21-25. 

 COOK. H. I.. 



1965. Rearing and identif\ing shrimp larvae. In M. J. 

 Lindner and J. H. Kutkuhn (editors). Biological Labora- 

 tory, Galveston. Tex., fishery research lor the year ending 

 June 30, 1964, p. 11-13. U.S. Fish Wildl. Serv.. Circ. 

 230. 



1966. Identification and culture of shrimp larvae. //iM.J. 

 Lindner and J. H. Kutkuhn (editors!. .Annual Report of 

 the Bureau of Commercial Fisheries Biological Labora- 

 tory. Galveston. Texas. Fiscal Near 1965. p. 12-13. U.S. 

 Fish Wildl. Serv . C irc. 246. 



38 



