JONES and DRAGOVICH: UNITED STATES SHRIMP FISHERY 



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MONTH OF LANDING 



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72 73 74 75 76 77 

 FISHING ZONE 



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80 81 



shrimp also are present off Guyana. The smaller 

 size of shrimp and higher catch rates in both areas, 

 as compared with the larger shrimp and lower 

 catch rates off Surinam, suggest that the East and 

 West Grounds represent the principal areas of re- 

 cruitment (Figure 1). Furthermore, the peaks of 

 small shrimp in March, April, and October may 

 indicate seasonal recruitment. Seasonal peaks in 

 spawning and recruitment are common in penaeid 

 shrimp populations, even where these activities 

 occur throughout the year (Cook and Lindner 

 1970; Costello and Allen 1970). To determine the 

 exact areas and chronology of recruitment for each 

 species off the Guianas and northern Brazil will 

 require additional research. 



VARIATION IN CATCH RATES 



Fishing success, or catch rate, provides a mea- 

 sure of the relative densities and availability of 

 shrimp to the fishing gear and to the skilled 

 fishermen. We examined the variations in catch 

 rate by year, month, area, depth, and time of day to 

 learn about the biology and ecology of the shrimp. 



The average annual catch rates for U.S. vessels 

 were 20.0 lb/fishing hour (1972 half year), 26.0 lb 

 ( 1973), and 18.3 lb ( 1974). To observe the monthly 

 differences in average catch rates off the Guianas 



FIGURE 7. — Distribution by month and fishing zone of the 

 mean size index of shrimp calculated from fishing log reports of 

 U.S. vessels. The size index was calculated as described in the 

 text. 



and off Brazil we plotted catch rates for each sta- 

 tistical zone (Figures 8 and 9). Fluctuations in 

 monthly catch rates followed a fairly regular pat- 

 tern, peaking each year in March and April and 

 then gradually declining during the remainder of 

 the year. There were smaller peaks in July and 

 August (Figure 8). Catch rates were consistently 

 higher off Brazil (zones 78-81) than off the 

 Guianas (zones 69-77). The highest catch rates 

 were recorded in zones 78-81, intermediate in 

 zones 75-77 and 69-71, and lowest in zones 72-74 

 (Figure 9). 



Information on water depth without specific 

 knowledge of the type of sediment, chemical con- 

 tent of water masses, and information on water 

 temperature and speed and direction of the cur- 

 rent means little in ecological terms. But, in a 

 pragmatic sense, the statistics on shrimp catches 

 versus depth are important. In our study the dis- 

 tribution of shrimp catches varied with water 



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FIGURE 8. — Distribution by month of the mean catch rate of 

 shrimp for U.S. vessels fishing off the Guianas (zones 69-77) and 

 off Brazil f zones 78-81 ), July 1972 to December 1974. Catch rate 

 is expressed as pounds and kilograms of shrimp (heads-off 

 weight) per hour of fishing. 



709 



