summary of apparent effects), the fact that weired systems can maintain large standing crops of 

 estuarine fishes and crustaceans (Weaver and Holloway 1974; Perry 1981) suggests that more study 

 is needed to better understand the trade-offs brought about by weir construction. 



The present study, funded by the Louisiana Wildlife and Fisheries Commission, is designed to 

 develop an overview of the fishery organisms of the State Wildlife Refuge over a several-year 

 period and to try to determine the weir-induced effects on these organisms. 



Historic Salinity Trends in the Study Area 



The refuge lies at the eastern extremity of the Chenier Plain region (Gosselink et al. 1979) 

 and at the western extremity of the Atchafalaya Bay system, which has been capturing increasing 

 flows of the Mississippi since about a century ago (Gunter 1952). The refuge marsh is brackish, 

 with burning practiced over most areas every year. Consistent with this type of marsh is the large 

 production of white shrimp, Penaeus setiferus (Hebert 1968). 



Although salinity data have not been measured continuously at the refuge, there are data from 

 a number of years suggesting little change of salinity over the last four decades (Table 1). 

 Salinities may have responded to periods of either drought or floods, such as the floods of the 

 1970's (Juneau 1975; Hoese 1976), but the area has remained stable despite these events. To the 

 contrary, Gosselink et al. (1979) reported a decrease in salinity at the Vermilion Lock, but this 

 may be an artifact of several years of high salinities from drought and Hurricane Audrey in the 

 1950's. In our separate incomplete analysis of the fishery organisms studied since the 1950's, there 

 is also no evidence yet detected of large changes in the fauna, although there may be effects on 

 certain species. 



The purpose of this study is to provide a long-term (several years) analysis of the populations 

 of aquatic animals in the refuge, especially in relation to the effect of the weirs. Additionally, 

 material previously gathered on aquatic animals on the refuge will be summarized. A species list 

 with pertinent information and references is being produced, with a referenced overview of the 

 system based on historical work. The present paper will largely introduce the study and the 

 preliminary results. 



MATERIALS AND METHODS 



Starting with a trial sampling in September of 1987, monthly samples are to be taken and 

 continued through the duration of the project. Because of weather and logistical problems, no 

 sample was taken in March 1988. Samples are taken with gill nets, trawls, and a quantitative 

 barrel sampler. Representative comparative samples are taken in Fearman Lake, and in one 

 unweired pond (off Toms Bayou), and one pond (Bob's Lake) where access is restricted by a 

 13.4-m weir (Figure 1). The weir to the lake restricts a 15-m channel preventing water levels 

 falling below about mean sea level. In contrast, the small pond off Toms Bayou will go dry during 

 low tides. Both lakes are roughly circular with widths of about 330 ±50 m, but Bob's Lake has 

 an estimated area of about 11 ha, compared to 6 ha for Toms. 



The concept of the study is to test for differences between unweired and weired systems which 

 are as close to being equal as possible in distance from the bay, size, and other attributes and to 

 a common area between (Fearman Lake). Site samples will determine what animals are available 

 from the pool of spawners in the open bay and gulf systems. For example, if the weir has an 

 effect it might show up in the appearance of a species later in the weired pond than either the 

 common area or the open pond. 



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