Impacts of water rediversion on the spawning utilization of a formerly impounded ricefield by blueback herring

Eggs of blueback herring (Alosa aestivalis ) and other fish taxa were sampled in Mulberry Ricefield, a former impoundment, and the west branch of Cooper River, South Carolina, U.S.A. from 1 March to 27 April 1988 and from 3 March to 27 April 1989. Four taxa of fish eggs (n = 60,365) were collected in 1988 and eight taxa (n = 10,541) in 1989. No statistical difference (P > 0.05) was detected in catch of herring eggs per unit effort (CPUE) between sampling years or collection locations. Most herring eggs were collected at open water stations within Mulberry Ricefield. These results were compared to 1981-82 CPUE values of herring eggs at the same study area. A 99.6% decline in CPUE was observed from the collection years 1981-82 to 1988-89 after the rediversion in 1985 of 75% of the water from Cooper River into Santee River. Number of taxa and eggs in the collections also declined between 1981-82 and 1988-89. Only one new taxon of fish eggs was found in post-rediversion collections.