varied from 12,885 to 34,210 and by the large 

 shrimp from 37,550 to 45,000. 



Ovigerous females were taken in the lower 

 St. Paul River throughout the May-January 

 fishery. The lengths of the ovigerous females 

 ranged from 47 to 131 mm. and the mode was 

 in the 80- to 90-mm. interval (fig. 7). Of the 

 total number of ovigerous females, shrimp less 

 than 60 mm. made up 2.5 percent, and shrimp 

 greater than 115 mm. made up 2.7 percent of 

 the catch. The higher percentage of females 

 bearing advanced (brown and eyed) eggs oc- 

 curred in the same months as the higher per- 

 centages of females bearing less developed 

 (red) eggs (table 6). This would indicate an 

 embryonic period of less than 1 month. Ling 

 (1967a) found the embryonic period in Macro- 

 brachium rosenbergii was 19 to 20 days at 26 

 to 28° C. 



Peak spawning periods occurred during the 

 commercial seasons — in 1952, M. vollenhovenii 

 spawned in August and December, and in 1953, 

 in September and December (table 6). Raj- 

 yalakshmi and Randhir (1967), reported that 

 in India the commercial prawn, Macrobrachinm 

 malcolmsonii (Edwards), has two spawning 

 peaks. No explanation can be given for the 



20 -i 



15 



10- 



o 



<c 



41 



1952 SEASON 

 N. 148 



Lx 



1953 SEASON 

 N.336 



"H-i 



20 40 60 80 100 120 140 



TOTAL LENGTH [MM.) 



Figure 7. — Length distributions of ovigerous female 

 shrimp, M. vollenhovenii, in the commercial catch, 

 during the 1952-53 season, in the lower St. Paul 

 River, -Liberia. 



smaller percentage of ovigerous females of 

 M. vollenhovenii found in the 1952 catch than 

 in that of 1953 (table 6). 



The zero age group was subjected to an 

 intensive fishery soon after it appeared. 

 Groups of 3 to 10 women drove large push-nets 

 made of burlap sacking along the shore and 



Table 6. — Numbers and percentages of M. vollenhovenii females with eggs in the early (red) and late (brown) 

 stages of development, and total number of ovigerous females during the 1952 and 1953 commercial seasons, 

 in Liberia 



Month 



Shrimp 



Females with 

 red eggs 



Females with 

 brown eggs 



Total ovigerous 

 females 



1952 season: 



July 



August . . . 

 September 

 October . . 

 November 

 December 

 January . . 



Number 



388 

 762 

 312 

 461 

 545 

 678 

 69 



Total . . 



1953 season: 



May 



June 



July 



August . . 

 September 

 October . . 

 November 

 December 



3,215 



158 

 839 

 1,201 

 86 

 149 

 630 

 935 

 874 



Number 



13 

 35 



1 

 12 



7 

 17 







85 



4 

 8 

 47 

 2 

 22 

 41 

 35 

 55 



Percent 



3.4 

 4.6 

 0.3 

 2.6 

 1.3 

 2.5 

 0.0 



2.6 



2.5 

 1.0 

 3.9 

 2.3 

 14.7 

 6.5 

 3.7 

 6.3 



Number 



9 

 27 



1 



3 



1 

 20 



2 



63 



7 



1 

 21 



4 

 10 



8 

 22 

 49 



Percent 



2.3 

 3.5 

 0.3 

 0.7 

 0.2 

 2.9 

 2.9 



2.0 



4.4 

 0.1 

 1.7 

 4.6 

 6.7 

 1.3 

 2.4 

 5.6 



Number 



22 

 62 



2 

 15 



8 

 37 



2 



148 



11 



9 



68 



6 



32 



49 



57 



104 



Percent 



5.7 

 8.1 

 0.6 

 3.3 

 1.5 

 5.4 

 2.9 



4.6 



6.9 

 1.1 

 5.6 

 6.9 



21.4 

 7.8 

 6.1 



11.9 



Total 4,872 



214 



4.4 



122 



2.5 



336 



6.9 



10 



