Population Characteristics of White Catfish and Channel Catfish in the Delaware River Estuary
David H. Keller
Abstract.—In the Delaware River estuary, native white catfish Ameiurus catus have appeared to decline as the introduced channel catfish Ictalurus punctatus has become more abundant. To determine the current status of these populations and the habitats they use, I surveyed four zones of the Delaware River estuary from April to November 2007. Hoop nets (N = 497) were set in main-stem river, lower tributary, and middle tributary habitats. Upper tributary habitats near the head of tide were angled. Our findings indicated that the ratio of channel catfish to white catfish was less than documented in the early 1990s. Channel catfish and white catfish were found throughout the study area, during all seasons. Channel catfish catch per unit effort was significantly greater in the river than in tributary habitats. Relative condition differed seasonally among zones and zone groups. Both species had unstable age structures, indicating variable recruitment. Variable recruitment may account for past differences in ratios of channel catfish to white catfish. Channel catfish in this study lived longer (22 years) when compared to channel catfish collected in other nearby river systems. Few brown bullhead A. nebulosus and no yellow bullhead A. natalis or ﬂathead catfish Pylodictis olivaris were collected.