Figure 3. — Construction of fresh-water shrimp traps in the lower St. Paul River, Liberia. 



The small, mangrove-type Mesurado River, 

 which adjoins the St. Paul River, lacks the 

 runoff lag and becomes highly saline several 

 months before the St. Paul River (table 1). 

 The higher salinities and lack of rock bottom 

 habitat are believed to be the primary reasons 

 for the negligible numbers of fresh-water 

 shrimp caught in the Mesurado River estuary. 



The oceanic waters of the Monrovia Free- 

 port were directly influenced by the low sa- 

 linity runoffs of the St. Paul and Mesurado 

 Rivers. The Monrovia Freeport is located in- 

 termediate, and a short distance between the 

 two rivers. The runoff lag of the St. Paul 

 River as it decreased in December-January 

 was reflected by increased salinities in the 

 Freeport (table 2). 



Economic Value 



The economic value of the shrimp varied 

 with size. At the beginning and end of the 

 season, when shrimp were small, 18 shrimp 

 retailed for 25 cents (U.S.) to the consumer. 

 During the rest of the season, the fishermen 



Table 2. — Salinities in the Monrovia Freeport, Liberia, 

 August 1953-January 1954 



Month 



Lowest 

 salinity 



Highest 

 salinity 



Average 

 salinity 





P.p.t. 



P.p.t. 



P.p.t. 



Aug. 



11.0 



24.0 



17.1 



Sep. 



6.2 



24.4 



12.7 



Oct. 



5.2 



23.5 



13.7 



Nov. 



18.2 



30.4 



25.2 



Dec. 



23.8 



32.8 



30.0 



Jan. 



28.8 



33.3 



31.5 



