Growth, spawning and habitat use of catfishes in the Delaware River Estuary:

In the Delaware River estuary, native white catfish (Ameiurus catus Linnaeus 1758) have appeared to decline as the introduced channel catfish (Ictalurus punctatus Rafinesque 1818) has become more abundant. To determine the current status of these populations and the habitats they use, we surveyed four zones of the Delaware River estuary from April to November, 2007. Hoop nets (N=497) were set in mainstem 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 much less than documented in the early 1990’s. Channel catfish and white catfish were found throughout the study area, during all seasons. Channel catfish and white catfish catch-per-net-night (CPNN) increased significantly from spring to fall. ANOVA of white catfish CPNN revealed a significant two-way interaction indicating movement downstream and into the lower estuary during the fall. 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. This difference may be a function of comparing otolith ages (in this study) with age maxima determined by spines and other techniques known to underestimate the age of old catfishes. Few brown bullhead and no yellow bullhead or flathead catfish were collected.M.S.Includes bibliographical references (p. 113-118)by David H. Kelle