Table 2. Percentage of change in catch when comparing catches from the 

 weired pond to catches from the unweired pond. (The unweired pond catch 

 was subtracted from the weired pond catch, the result was divided by the 

 unweired pond catch, and that result was multiplied by 100. The species 

 listed are the same as in Table 1.) 



The traps were operated continuously from 15 February to 30 July 1986. Catch of brown shrimp 

 from the pond with the slotted weir was 2.4 times greater in number, and 84% greater in weight, 

 than the catch from the pond with the standard fixed-crest weir. During this study, members of 

 57 species were taken in the trap on the slotted weir pond, whereas members of only 42 species 

 were taken in the trap on the standard fixed-crest weir pond (Rogers et al. 1987). Moreover, the 

 slotted weir appeared to control water levels adequately for other management purposes. Nursery 

 usage, however, was still apparently lower in both the slotted weir and the standard fixed-crest weir 

 ponds than in a nearby unimpounded pond. During the study, equal trawling efforts in each of 

 the ponds collected members of 46 species in the unimpounded pond, 29 in the slotted weir pond, 

 and 27 in the standard weir pond. 



We consider the slotted weir to be an improvement for fishery purposes, but realize that testing 

 of other water-control designs should continue if the use of water-control devices in the marsh is 

 also going to continue. In furtherance of this goal, and in cooperation with the National Audubon 

 Society at their Paul J. Rainey Wildlife Sanctuary, we are currently studying the effects of a rock 

 weir designed and installed by the sanctuary personnel. We believe the best design for passing 

 young aquatic organisms into semi-impounded areas has yet to be determined, but with sufficient 

 research, satisfactory solutions to the passage problem may be possible. Moreover, our past studies 

 indicate the habitat in semi-impounded areas is generally suitable for those organisms that do gain 

 access. As will be evident in the next section, however, in many circumstances we suspect semi- 

 impoundment may be destructive to the habitat itself. 



MARSH MANAGEMENT 



Herke (1979) stated, "Before anyone makes substantial expenditures to (1) build more weirs of 

 conventional design, or (2) design new weir types, or (3) tear out existing weirs, or (4) maintain 

 existing weirs, I believe the true effects of semi-impoundment on nursery production (not standing 

 crops) should be determined." We believe these effects have now been sufficiently determined to 

 say that marsh management usually is detrimental to fisheries in the short run when it is done by 

 means of levees and weirs or other water-control structures that interfere with the migratory cycles 



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