Population Size and Relative Abundance of Adult Alabama Shad Reaching Jim Woodruff Lock and Dam, Apalachicola River, Florida

Abstract

We estimated the population size of migrating Alabama shad Alosa alabamae below Jim Woodruff Lock and Dam in the Apalachicola River (located in the central panhandle of northwestern Florida) using mark–recapture and relative abundance techniques. After adjustment for tag loss, emigration, and mortality, the population size was estimated as 25,935 (95% confidence interval, 17,715–39,535) in 2005, 2,767 (838–5,031) in 2006, and 8,511 (5,211–14,674) in 2007. The cumulative catch rate from boat electrofishing averaged 20.47 Alabama shad per hour in 2005, 6.10 per hour in 2006, and 13.17 per hour in 2007. The relationship between population size (N) and electrofishing catch per unit effort (CPUE) was modeled by the equation N = −9008.2 + (electrofishing CPUE × 1616.4). Additionally, in 2007 the hook-and-line catch rate averaged 1.94 Alabama shad per rod hour. A predictive model relating the population size and hook-and-line CPUE of spawning American shad A. sapidissima was applied to Alabama shad hook-and-line CPUE and produced satisfactory results. Recent spawning populations of Alabama shad in the Apalachicola River are low relative to American shad populations in other southeastern U.S. rivers.