THE RIVER SHRIMP OHIONE (SMITH) (, ): ITS ABUNDANCE, REPRODUCTION, AND GROWTH IN THE ATCHAFALAYA RIVER BASIN OF , U.S.A. 1)

BY

FRANK M. TRUESDALEand WARREN J. MERMILLIOD School of Forestry and Wildlife Management, Louisiana State University, Baton Rouge, Louisiana 70803, U.S.A.

The river shrimp Macrobrachium ohione ( Smith, 1 874 ) occurs from Ohio and Illinois south to Louisiana in the Mississippi Valley, from Texas to Alabama in Gulf of Mexico coastal drainages, and from Virginia to northern on the Atlantic slope (Holthuis, 1952). Although M. ohione once existed in fisheries in several parts of the Mississippi Valley (Forbes, 1876; Gunter, 1937; Hay, 1882; McCormick, 1934) and is still fished extensively in Louisiana for bait and human consumption (Mermilliod, 1976), few published accounts of this species' life history and ecology are available. As part of a baseline study of the Atchafalaya River Basin, Louisiana, the U.S. Fish and Wildlife Service and U.S. sponsored by I Army Corps of Engineers (Contract No. 14-16-008-767), we gathered two years' field and laboratory data concerning abundance, reproduction and growth of the river shrimp.

STUDY AREA The Atchafalaya Basin naturally covered an area of approximately 4662 km2 but flood-control levees have effectively reduced the basin to about 3480 km2. Seasonal discharge fluctuations of the Mississippi and Red rivers directly influence water levels in the Atchafalaya Basin. The aquatic production of the basin and other southern river swamps is dependent on an annual watering-dewatering cycle (Wharton, 1970). Two study areas were located in the Middle Basin, south of Interstate High- way 10 (1-10) and north of Morgan City, Louisiana (fig. 1). The west study area was located near 29°59'N 91°31'W; the east study area was located near 29°47'N 91 ° 16'W. In both areas stations were chosen to represent the following aquatic habitats: willow swamp, cypress-tupelo gum swamp, lake and lake shore, - bayou, canal and river major distributary (table I). Habitat designations were based on features such as vegetation, relative water movement, and water body configuration.

1) Contribution Number 17 Louisiana Cooperative Fishery Research Unit. 62

Fig. 1. Atchafalaya Basin study areas and stations. Insert (upper right) shows the middle and lower Atchafalaya Basin.

METHODS Shrimp were collected with seines measuring 3.1 m X 1.8 m X 3.2 mm (mesh) and traps constructed of 6.35 mm (mesh) hardware cloth. Seine samples were taken monthly from September 1973 through July 1 97 5 ; trap samples were taken monthly from August 1974 through July 1975. Traps were baited with chicken parts and set for three days. In situ bottom measurements of water temperature, dissolved oxygen, conduc- tivity and pH were taken at the time of trap set and retrieval with a portable water quality analyzer. Only surface water temperature was consistently measured (by hand-held thermometer) with each seine sample.