A pilot survey on the Lower Mississippi River, river mile 480 to 530, was conducted from April to October 1978. The objectives of this field survey were to collect data on fish, benthos, and water quality as they are impacted by the placement and design of navigational structures such as dikes and bank revetments. Information obtained on gear types and procedures from the pilot study was used to design further waterway studies on the Lower Mississippi River. Rationale for selection of sample sites, description of the study area and the 12 habitat types investigated, literature review, and general information on navigational structures are presented in this introductory report. A complete discussion of the fishery, benthos, water quality investigations, and other results of these studies as they relate to the Lower Mississippi River are found in Reports 2 through 8 of this series.

To expedite the research data management system (RDMS) required for complex and large-scale ecological field studies being done at the U.S. Army Engineer Waterways Experiment Station (WES), a graphical display system was developed. The Statistical Analysis System (SAS) provides the framework for making open-ended RDMS practical and cost-effective. PROC VIVIPLOT is the first of a series of SAS procedures that will produce copy-ready figures with some independence as to choice of plotter. Several approaches are available that minimize errors in coding variables. Numeric codes, 'smart codes, ' with embedded information allocated to positions within the value codes are widely used but unacceptable for variables with many values and/or many levels of classification. 'Nonsense' codes, or codes without embedded information, however, efficiently circumvent the problems associated with smart codes. Using nonsense codes, alphanumeric variable values are assigned a sequential numeric code as new values are encountered in the data base, irrespective of the position of the value in the classification scheme for that variable. With the use of nonsense codes, the management approach is open-ended and does not require a knowledge of the number of potential classification levels for the variables. In addition, experience with several large environmental data bases indicates that coding errors appear to be less frequent using nonsense codes than in those studies in which a smart code approach was used.

The pilot investigations provided significant guidance in the choice of methods and the experimental design for the long-term effort. In addition to increasing the overall validity of the data, cost savings were also obtained through the use of the most efficient techniques and in the reduction of unneccessary sampling. (Author).

TO PROVIDE DATA FOR DESIGN OF FIELD STUDIES TO DETERMINE THE IMPACTS AND ECOLOGICAL VALUE OF THE MAN-MADE HABITATS FORMED BY DIKE AND REVETMENT STRUCTURES IN THE LOWER Mississippi River, the aquatic habitat of a 50-mile reach of the river (mile 480 to 530 Above Head of Passes, AHP) was quantitatively mapped to determine spatial relationships among and within habitat types as a function of river stage and discharge. Twelve aquatic habitat types were defined within the study reach based on hydraulic, geomorphological, and ecological criteria: main channel, natural banks, revetted banks, sandbars, dike fields, permanent and temporary secondary channels, abandoned river channels(Types I and II), oxbow lakes, borrow pits, and inundated floodplain. By use of controlled aerial photography and hydrographic survey data, aquatic habitat surface acreages were computed for three river stages (low flow = +13.2 ft, medium flow = +24.6, and high flow = +38.4 ft on the Greenville, Mississippi, gage). Results of the habitat mapping revealed a significant change in total aquatic habitat acreage with changes in river stage and discharge. At the low flow stage 18,581 acres of habitat were present. Habitat area increased to 29,020 acres at medium flow and rose to 56,902 acres for high flow--a total increase of 222 percent in area over low flow conditions.

Based on results of the pilot study, the following recommendations are made: when the choice of gear is limited because of manpower or equipment constraints, seines, electroshocking, gill nets, and hoop nets should be used in riverine systems; the number of habitats studied should be limited to dike fields, revetted banks, natural banks, and abandoned channels; the same habitat type should be sampled at two or more different locations to determine variance and comparability of physical and biological parameters; the number of samples taken with a particular gear in any given habitat should be increased to reduce the variation in C/f values; because of considerable temporal variation in species composition and abundance of fish communities in the different habitats, sampling should be conducted throughout the year; and before beginning a major field study, a pilot study should be conducted to familiarize field personnel with the physical characteristics of a study area, the fish species associated with the different habitats, and adequate sampling methods for the different fish communities.