Meeting Abstract

2.1  Sunday, Jan. 4  Nocturnal swimming patterns and speeds in the upstream juvenile migration of the amphidromous river shrimp Macrobrachium ohione and the potential for long distance migrations OLIVIER, T.J.*; MOON, B.R.; BAUER, R.T.; University of Louisiana at Lafayette; University of Louisiana at Lafayette; University of Louisiana at Lafayette tjo1457@louisiana.edu

In the river shrimp Macrobrachium ohione, larval development takes place in coastal estuaries after which postlarvae (juveniles) make a mass migration upriver into the adult freshwater habitat. To understand the timing and possible range of migration, we are studying swimming speed and duration in juveniles migrating up the Atchafalaya River, a distributary of the Mississippi river in Louisiana. We measured abundances and swimming speeds of juveniles at night using camcorders, infrared illumination, and motion analysis software. Preliminary data from 2007 showed ground speeds from 0.6-1.4 km/h measured at river velocities of 0.5-1.3 km/h. In 2008, we measured swimming patterns and velocities weekly throughout the summer migration to reveal the nocturnal patterns of movement and speeds as well as weekly relative abundances throughout the migration. These data can be used to estimate the time required for long distance migrations up the Mississippi River System (MRS). Various hypotheses are compared to explain the previously large populations of this amphidromous shrimp in the upper MRS and lower Ohio river, up to 2000 km from the coastal estuaries in which larval development occurs: (a) a long distance amphidromous migration to and from the Gulf of Mexico; (b) adaptation of northern populations to freshwater (abbreviated development); and (c) inland larval nurseries created by the formerly numerous saline springs and salt deposits in the upper Mississippi and lower Ohio Rivers. Supported by NOAA LA Sea Grant R/SA-04.