seasonal trends in larval abundance and sea- 

 sonal changes in water temperature seemed 

 to be related. In 1963, however, this relation 

 was not as apparent; it seems that spawning, 

 larval abundance, or both, may not be related 

 to a specific temperature but perhaps to changes 

 in temperature. 



Noncommercial Species 



Distinct patterns of depth distribution and 

 trends of abundance were evident for the non- 

 comnnercial planktonic- stage penaeids in our 

 plankton hauls. Species of Sicyonia and " TX " 

 occurred most frequently inside the 25-fath. 

 contour, whereas species of Solenocera and 

 Parapenaeus were most frequently found in 

 deeper waters. In addition, species of Sicyonia 

 " TX" and Solenocera occurred in greater num- 

 bers between August and October; species of 

 Parapenaeus were nnost abundant in January 

 and February. 



Clarence C. Fischer, Project Leader 



IDENTIFICATION AND CULTURE 

 OF SHRIMP LARVAE 



The prinnary aim of this project is to 

 develop nnethods of rearing penaeid shrimp 

 so that larvae of known parentage may be 

 obtained for comparative morphological 

 studies. During the past year three species 

 have been reared to postlarvae: brown shrimp, 

 pink shrimp, and Trachypeneus similis . A 

 preliminary examination showed that brown and 

 pink shrimp larvae had no significant dif- 

 ferences in setation or other easily observed 

 body parts. The ratios of various body parts 

 might be significantly different, but the larvae 

 were too few for a detailed study. Several 

 series of larvae, obtained at different seasons 

 from females of each species, are now being 

 accumulated for examination. 



A secondary goal is to determine methods 

 of rearing penaeid larvae en masse to supply 

 shrimp grown under known conditions for 

 physiological and pond-culture studies. In 

 early culture experiments, larvae in limited 

 numbers could be reared to postlarvae only 

 when they were held in enriched sea water, 

 which was changed daily. In recent rearing 

 trials, larvae of both brown and pink shrimp 

 have been reared in sea water in 20-gal. 

 (gallon) mass cultures with disodium salt of 

 the metal chelator E.D.T.A. the only additive. 



Development of an effective screening and 

 filtering system (fig. 6) made it possible to 

 discontinue the use of antibiotics during spawn- 

 ing and hatching. One end of a 20-gal. fiber- 

 glass tank has been fitted with a nylon screen 

 of a mesh size too small to allow the eggs 

 or larvae to pass through (0.18 nnm. or 0.007 

 in.). Water is then pumped from the screened 



end of the tank and recirculated through a 

 filter of crushed oyster shell without damage 

 to the larvae. Water is recirculated through 

 the filter from the tinne the ripe shrimp is 

 placed in the tank until the eggs hatch and 

 the first protozoeal stage begins to feed. 

 Subsequently, the water is filtered only for 

 I hr. a day. A metering pump furnishes a 

 constant supply of the diatonn, Skeletonema 

 species, as food. A light beneath the tank 

 attracts the larvae on the bottonn; however, 

 an air bubbler in the tank disperses the larvae 

 throughout the tank. 



Using the equipment and techniques de- 

 scribed above, we have successfully reared 

 brown and pink shrimp. During these two 

 experiments, temperatures ranged between 

 26° C. (78.8° F.) and 27° C. (80.6° F.), and 

 salinity varied from 24.1 p.p.t. to 20.5 p.p.t. 

 Under these conditions the first postlarva 

 was observed on the 13th day after hatching, 

 and almost all larvae had metamorphosed to 

 postlarvae by the 15th day. 



In an effort to determine optimum conditions 

 for population growth and maintenance of 

 organisms to be tested as food for larval 

 shrimp, four diatonns, two flagellates, and 

 three dinoflagellates were each cultivated in 

 nine different media. Although cell nnultiplica- 

 tion varied with the species and media tested, 

 each organism produced the greatest nunnber 

 of cells in Miquel's sea water with soil extract. 

 The population did not increase in sea-water 

 controls. A similar experinnent tested the 

 effects of five fertilizers on population growth 

 of the diatom, Skeletonema species. In pro- 

 moting rapid growth, fertilizer composition 

 appeared less important than its concentra- 

 tion. Dilutions in the range 1/ 10,000- 1/ 100,000 

 induced greater increases in cell number 

 than did stronger or weaker concentrations. 



Two attempts to maintain 50-gal. cultures 

 of Skeletonema with commercial fertilizers 

 as a nutrient source in water from the lab- 

 oratory's sea-water system proved unsuc- 

 cessful; later, however, following the work 

 of Johnston (1964),^ we found that by adding 

 E.D.T.A. in a concentration of 1 g. (gram) 

 per 100 1. (liters) (about 15 g. per 25 gal.) 

 of sea water, we could easily maintain mass 

 cultures. The culture tanks are indoors, well 

 aerated, and constantly illuminated with about 

 1,000 ft.-c. (foot-candles) of fluorescent light. 

 Once the diatoms reach a peak density, we 

 have maintained vigorous cultures by drawing 

 off and replacing two-thirds of the water 

 in the tank daily. 



Work continued on how various environ- 

 mental conditions and foods affect larval 

 development. We completed one temperature 

 experiment with brown shrimp larvae. Larvae 



^Johnston, R., 1964. Sea water, the natural medium of 

 phytoplankton. II. Trace metals and chelation and general 

 discussion. J. Mar. Biol. Ass. U.K. 44 (1): 87-109. 



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