Early life history of channel catfish (Ictalurus punctatus) in Navigation Pool 7 of the upper Mississippi River
Duval, Michael C.
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Young-of-the-year (YOY) channel catfish (Ictalurus punctatus) were collected from Navigation Pool 7 of the upper Mississippi River near La Crosse, Wisconsin, USA. The objectives of this study were to describe distribution and abundance patterns, identify variations in growth, and determine food habits of YOY over the entire pool. Otolith aging technique was validated in the laboratory and used to evaluate growth of wild fish. YOY were captured by otter trawl at night in the navigable main channel during summer 1984 and 1985. A total of 296 YOY (15-83 mm SL) were collected in 1984 and 183 YOY (15-68 mm SL) in 1985. No significant differences in catch were detected throughout the pool. YOY appeared in the drift in mid-July, reached peak abundance in August, then declined sharply. In general, length did not differ significantly throughout the pool, although stations associated with a large backwater tributary produced significantly smaller fish early in both collecting seasons. No differences in growth between stations were detected. Smaller YOY appeared to feed in the water column on invertebrate drift, then switched to benthic invertebrates at about 50-mm SL. All reaches of the main channel appear to be of equal nursery value for channel catfish. A large backwater area in the pool may represent critical spawning habitat. Changes in feeding behavior dramatically affect catchability of YOY. Discharge is the major factor influencing adult spawning and YOY distribution patterns. Drifting YOY could be significantly impacted by hydropower development and commercial navigation. Otter trawling represents a means of evaluating channel catfish year-class strength. Current research gaps are presented.