Chowan and Meherrin River largemouth bass population response following Hurricane Irene

CHOWAN AND MEHERRI N RIVER LARGEMOUTH BASS POPULATI ON RESPONSE FOLLOWI NG HURRI CANE I RENE Federal Aid in Sport Fish Restoration Project F-108 Final Report Kathryn M. Potoka Jeremy W. McCargo Benjamin R. Ricks North Carolina Wildlife Resources Commission Division of Inland Fisheries Raleigh 2014 Keywords: Largemouth Bass, Chowan River, electrofishing, hurricane response This project was funded under the Federal Aid in Sport Fish Restoration Program utilizing state fishing license money and federal grant funds derived from federal excise taxes on fishing tackle and otherfishing related expenditures. Funds from the Sport Fish Restoration Program are used for fisheries management and research, aquatic education, and boating access facilities. The program is administered cooperatively by the N.C Wildlife Resources Commission and the U.S. Fish and Wildlife Sen/ice. Abstract.— After landfall of Hurricane Irene on 27 August 2011, portions of the Chowan River upstream of Holiday Island experienced significant declines in dissolved oxygen resulting in a widespread fish kill. To monitor initial impacts and population recovery following Hurricane Irene, the Largemouth Bass Micropterus salmoides population was surveyed with boat mounted electrofishing gear in fall 2011, spring and fall 2012, and spring 2013. Anoxic and hypoxic conditions were documented from Wiccacon River upstream to Virginia tributaries, spanning roughly 50 river km. The lower Chowan River was largely unaffected by Hurricane Irene and by spring 2013 relative abundance of Largemouth Bass greater than 200 mm surpassed the benchmark for coastal North Carolina rivers (25 fish/h) with a mean CPUE of 28 fish/h (SE=2). The middle Chowan River Largemouth Bass population experienced significant declines in relative abundance following Hurricane Irene. However, Largemouth Bass in the middle Chowan River nearly recovered to the relative abundance coastal benchmark; mean CPUE in spring 2013 was 18 fish/h (SE=5.4). Following Hurricane Irene, hypoxic waters were documented throughout the entire upper Chowan River and widespread fish kills were reported. Relative abundance of Largemouth Bass did not reach pre-hurricane levels by spring 2013, with a mean CPUE of 5 fish/h (SE=3.3). Future survey efforts should focus on the Upper Chowan River to assess the need for management actions to supplement natural recovery of Largemouth Bass. The Meherrin River, a major tributary to the Chowan River, Largemouth Bass population was also impacted by hypoxic waters; however, relative abundance increased during the study period and reached 14 fish/h (SE=2.8) by spring 2013. In general, Largemouth Bass in the Chowan River have the capacity to naturally recover to pre-hurricane levels. Successful reproduction in spring 2012 was apparent throughout the Chowan River and was evident by the large numbers of sub stock-length Largemouth Bass collected in fall 2012. The Largemouth Bass population was also found to be shifting toward larger individuals. Spatial patterns in Largemouth Bass population recovery following hurricanes will help determine if augmentation to the population is warranted. 1