Table 2. Operational schedule for the Little Pecan Lake water control structure. 



a Flap-gate raised and all stop-logs removed. 



b Flap-gate closed and stop-logs placed to approximately 15 cm below marsh level. 



catch within Little Pecan Lake that year was estimated to be approximately 680 kg. Considering 

 the annual fishing effort and the potential for shrimp to escape from the lake without being caught, 

 we estimated that one-third of the lake's shrimp population was harvested. Annual white shrimp 

 production was estimated by multiplying the annual catch by 3. This multiplication factor is equal 

 to or less than that determined by analysis of white shrimp catch data from South Carolina semi- 

 impoundments (Whetstone 1987). White shrimp production within Little Pecan Lake was estimated 

 at 14.3 kg/ha/yr. Production values for the Grand Bayou sites were 28.7 kg/ha/yr for the 

 unmanaged semi-impoundment and 8.1 kg/ha/yr for the semi-impoundment managed via fixed-crest 

 weir. These data are summarized in Table 3. 



DISCUSSION 



White shrimp production at Little Pecan Lake was approximately half that from the unmanaged 

 Grand Bayou semi-impoundment. White shrimp production from Little Pecan Lake was sub- 

 stantially greater (177%) than that from the low-level fixed-crest weir site. To determine the 

 relative effects that water control structures had on ingress and production of white shrimp within 

 semi-impoundments, all other factors influencing white shrimp production should have been equal. 

 Such was not the case. 



Data from Grand Bayou were collected during 1983 and 1984, whereas data from Little Pecan 

 Lake were collected during 1984, 1985, and 1986. White shrimp landings from inshore waters of 

 Cameron Parish, LA indicated that white shrimp production was poor during 1983 and good during 

 1984, 1985, and 1986 (National Marine Fisheries Service 1988) (see Table 4). Since data were 

 collected at Little Pecan Lake only during those years when shrimp were abundant, the average 

 white shrimp production may have been exaggerated, relative to that from the Grand Bayou sites. 



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