Range and Seasonal Movements of Flathead Catfish in the Iowa River, Iowa
Gregory T. Gelwicks and Gregory A. Simmons
Abstract.—A radio-telemetry study was initiated in August 2004 to determine extent and timing of flathead catfish Pylodictis olivaris movements in the Iowa River, Iowa. Between 2004 and 2007, 56 flathead catfish were radio-tagged in the Iowa River between the Mississippi River and the lowermost dam at Iowa City, Iowa. Fish tagged for this study were collected during prespawn/spawn (mid-April to mid-July) and summer/fall (late-July to mid-October) periods at three sites. Radio-tagged fish were tracked through September 2009; fish included in our analyses were located 3–31 times and were tracked for 92–1,554 d. While some fish remained near original tagging locations, others made long distance movements associated with overwintering and spawning. Total linear range varied from 0.5 to 120 km with a mean of 42.4 ± 6.1 (mean ± SE) km, and there were no significant correlations between total linear range and fish length or age. There was no significant difference in total linear range of fish related to tagging period. However, seasonal movement patterns indicated that timing of sampling may affect population characteristics observed at the reach level in the Iowa River. Fish tracked for multiple years exhibited a high degree of fidelity for seasonal locations, particularly during summer/fall and overwintering periods. In addition to telemetry results, harvest of radio-tagged fish in the English and Mississippi rivers indicates that a larger scale than the reach, or Iowa River main stem, should be considered in management of flathead catfish in the Iowa River.