Meeting Abstract

45.2  Wednesday, Jan. 5  Impacts of river control structures on the juvenile migration of the amphidromous river shrimp Macrobrachium ohione: possible solutions for the restoration of upstream populations. OLIVIER, T.J.*; BAUER, R.T.; Univ. of Louisiana, Lafayette; Univ. of Louisiana, Lafayette tjo1457@ull.edu

Many shrimps conduct recurring migrations between the river and the ocean because they live and breed in fresh water, but larval development occurs in the sea, a life history pattern termed amphidromy. In the Mississippi River System (MRS), Macrobrachium ohione is an amphidromous species that has experienced population declines along the shrimps’ northern distribution, possibly due to structures like the Old River Control Complex (ORC) in Louisiana. This study tested the hypothesis that ORC (dam, lock, control gates) impedes or prevents movement of juvenile M. ohione from the Atchafalaya River (AR) into the Mississippi River (MR). Juvenile migrants were sampled using unbaited traps placed in the channels leading into and out of the river control structures. Relative densities of juveniles in the channels leading into the structures were greater than those leading out of the structures, which suggest that the upstream migration is halted at the structures. However, relative densities of juveniles differed in the channels on the AR side of the structures, implying that density of shrimps moving in the channels was related to the discharge from the respective channels. This work also tested ability of M. ohione juveniles to climb up structures, a behavior observed in many amphidromous species. In the laboratory, juveniles repeatedly displayed the ability to climb a 1.5 m ramp at a 30° incline, suggesting that they might climb up and over a dam or weir if presented with a suitable “shrimp ladder.” Installation of shrimp ladders and migratory conduits at river control structures may be a viable solution to restoring M. ohione populations in the upper MR.