Table 3. — Total weights and weights of head (cephalothorax) and tail (abdomen) of M. vollenhovenii caught 

 commercially in the lower St. Paul River, Liberia, June to December 1953 



Date 

 1953 



Shrimp 



Body 



weight 



Head 



Weight 



% total 

 body weight 



Tail 



Weight 



% total 

 body weight 



Average 



weight of 



shrimp 



Shrimp 

 per lb. 





No. 



G. 



G. 



% 



G. 



% 



G. 



No. 



June 13 



341 



4,180 



2,017 



48.25 



2,163 



51.75 



12.26 



37.00 



June 20 



499 



8,414 



4,101 



48.74 



4,313 



51.26 



16.86 



26.90 



Aug. 28 



86 



1,662 



813 



48.92 



849 



51.08 



19.33 



23.47 



Sept. 4 



59 



1,411 



694 



49.18 



717 



50.82 



23.92 



18.96 



Sept. 11 



50 



877 



411 



46.86 



466 



53.14 



17.54 



25.86 



Oct. 2 



33 











__. 



__ 



__ 



12.79 



35.47 



Oct. 16 



167 















__ 



__ 



22.91 



19.80 



Nov. 13 



360 











__ 



__ 







26.46 



17.14 



Nov. 27 



708 



__ 











__ 



__ 



24.99 



18.15 



Dec. 4 



874 



-- 



— 



— 



— 



— 



20.96 



21.64 



distributions of the catch, weight-length re- 

 lation, fecundity and spawning, and disease. 



Distribution 



M. vollenhovenii was described by Herklots 

 (1857) from specimens collected by H. Pel in 

 "CSte de Guine'e." Holthuis (1951) believed 

 that the type locality was erroneous because 

 Pel had collected only in the Gold Coast (now 

 Ghana) . Holthuis listed the synonymy of M. 

 vollenhovenii and gave its distribution as the 

 offshore islands of Cape Verde, Fernando Po, 

 and Sao Thome', and from Senegal south along 

 the West African coast to the Kunene River 

 in southern Angola. 



Description 



M. vollenhovenii grows to a total length of 

 more than 150 mm. In life the body is gray 

 or brown with a blue lateral line on the ab- 

 domen; a blue lateral line extends from mid- 

 way on the carapace forward and bifurcates 

 with a ventral branch to the hepatic spine and 

 dorsal branch over the orbit to the tip of the 

 rostrum. The rostrum is short, deep, and 

 slightly upturned at the tip; the dorsal surface 

 bears 11 to 15 spines and the ventral surface 

 3 to 8; though the spines may or may not ex- 

 tend to the tip of the rostrum, each spine is 

 preceded by setae — in many specimens setae 

 are found near the anterior end of the rostrum 

 where no spines are present. The carpus of 

 the major chela is always shorter than the palm, 

 and the fingers are not pubescent. In early 



stages of development the external eggs of the 

 female are orange to red, but change to brown 

 in the advanced stage before hatching. 



Rostral spine counts have been used to dis- 

 tinguish species of Macrobrachium. To de- 

 termine variation in numbers of rostral spines, 

 I made counts from 218 specimens of M. vol- 

 lenhovenii taken from the lower St. Paul River 

 on October 9, October 13, and November 13, 

 1953. I then compared the rostral spine counts 

 of shrimp from the St. Paul River, Liberia, 

 with those given by Man (1904) of shrimp 

 from the Catumbella River, Angola, to discover 

 whether the populations differed between the 

 two widely separated areas (table 4). 



The number of dorsal rostral spines on M. 

 vollenhovenii ranged from 11 to 15, with one 

 exception (18) given by Man (1904). Modally 

 the St. Paul River shrimp had 13 dorsal rostral 

 spines and Catumbella River specimens had 12. 

 The small difference in counts was probably 

 caused by a difference in the sizes of specimens 

 (my specimens were larger than Man's) rather 

 than a genetic or clinical difference between the 

 two populations of M. vollenhovenii. Ventral 

 rostral spines varied from three to eight, but 

 both populations had four modally. 



Length-Frequency Distribution 



The commercial fishery was sampled for 

 length distributions of the catch from July to 

 January (1952 season) and from May to No- 

 vember (1953 season). Figure 5 shows the 

 length distributions of 7,648 commercial shrimp 



