322 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



Table 1. — Station data for 161 larvae and postlarvae of 

 Penaeus duorarum taken from the plankton, 1959 



Station 



ELH79---- 

 ELH 104... 



ELHIH--- 

 ELH112.-. 

 ELH169.-. 



ELH172--- 

 EI.H175--- 

 ELH179... 

 ELH 185 '-. 

 ELH197--- 

 ELH221-.- 

 ELH 229... 

 ELH 233... 



ELH 240... 

 ELH 283... 

 ELH 317... 

 ELH334a.. 



Number and stage 

 of specimens 



2 (second post- 

 larvae) . 



22 (first, second, 

 and third post- 

 larvae). 



1 (second mysis). 



1 (first mysis) . 



46 (all stages from 

 first protozoea 

 through third 

 postlarva). 



1 (first mysis) . 



4 (third protozoea 

 and first mysis). 

 1 (third mysis). 



4 (advanced post- 

 larvae). 



1 (thtd mysis). 



4 (first and second 

 protozoea). 



2 (second and third 

 protozoea) . 



25 (aU stages from 

 first protozoea 

 through third 

 mysis). 



18 (first and second 

 mysis) . 



1 (second mysis). 



1 (advanced post- 

 larva) . 



27 (advanced post 

 larvae) . 



' One-minute trawl with seine. 



alive in transit in plastic 20-gallon trash cans 

 containing sea water circulated by a 12-volt pump. 

 About 1 dozen shrimp were held successfully in 

 each container for the duration of the 160-mile 

 trip. The water was changed midway of the trip. 

 At the laboratory three to six shrimp were 

 placed in 15-gallon aquariums, and circulation 

 was maintained by filtering sea water through 

 No. 6 silk bolting cloth (fig. 1). The small size 

 of the apertures (0.24 mm.) made it certain that 

 all eggs found in an aquariimi were spawned by 

 the shrimp being held. The runoff from each 

 tank was drained through a section of plankton 

 netting fitted to a collecting jar. During the 

 course of each experiment the (x>llecting jars and 

 aquariums were examined for eggs and larvae, 

 which were removed and studied microscopically. 

 Periodically, each tank was drained and its entire 

 contents examined. 



Eggs and nauplii removed from the aquariums 

 were held in a variety of contamers ranging from 

 petri dishes to a 4-gallon bell jar. The sea water 



in the smaller containere was changed frequently. 

 In the larger vessels it was generally not renewed 

 (luring the course of an experiment, but in several 

 instances was aerated by means of an air pump. 

 On one occasion a glass plunger provided mechan- 

 ical agitation of the water in the bell jar. 



Several types of food were introduced into the 

 containers when the lai-vae in them reached the 

 first protozoea! stage. The firet of these was 

 "Liquifry," a food intended for fish fry and made 

 up of particles the size of ciliate protozoans. In 

 subsequent experiments, cultures of the unicellular 

 green algae, Chlamydomonas sp. and Dunaliella 

 sp., were fed to the larvae. 



In the last two experiments, an attempt was 

 made to minimize bacterial contamination by add- 

 ing antibiotics to the water in which larvae were 

 being held. In one instance, approximately 

 400,000 units of penicillin were added to each of 

 several of the gallon jars; in anothei-, several 

 milliliters of a broad-spectrum antibiotic ( 10 mil- 

 ligrams/milliliter aureomycin, 2 mg./ml. chlor- 

 amphenicol, 2 mg./ml. streptomycin) were used. 



First Experiment 



The first rearing experiment took place from 

 March 26 to April 2. Six ripe female shrimp 

 were brought to the laboratory on March 30 ; three 

 shrimp were placed in a 15-gallon aquarium, and 

 the other three in a large concrete holding tank. 

 Eggs were found in the collecting jar of the 

 aquarium the following morning, and the entire 

 aquarium was drained and the eggs gathered. 

 The eggs were placed in a variety of containers 

 (in 32-, 16-, and 10-ounce jars and in petri dishes) 

 and by early afternoon they were begiiming to 

 hatch. The water in which the larvae were held 

 was changed approximately twice daily. Within 

 2 days the lan'ae that had not succumbed in the 

 nauplius stage, approximately 10 in number, had 

 developed to the first protozoea. They were fed 

 on Liquifi-y, approximately 1 milliliter being 

 added per 32 ounces of water, and examination of 

 the gut of the protozoea showed that feeding had 

 taken place. Despite this, all the remaining 

 larvae died in the first protozoeal stage within 5 

 days of the time the eggs were found. Because the 

 number of eggs spawned was relatively small and 



