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Tuesday, January 26 • 2:40pm - 3:00pm
Age and Growth of Grass Carp in the Great Lakes Region

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AUTHORS: Joseph E. Deters*, USGS Columbia Environmental Research Center; William Edwards, USGS Great Lakes Science Center; Patrick. M. Kočovský, USGS Great Lakes Science Center; Duane C. Chapman, USGS Columbia Environmental Research Center; and Seth J. Herbst, Michigan Department of Natural Resources

ABSTRACT: Grass carp Ctenopharyngodon idella is an invasive species that has been present in the Laurentian Great Lakes basin since at least 1983. In the past five years the number captured has increased, particularly in Lake Erie and Lake Ontario, and several of those fish were fertile diploids. Increased catches and the presence of fertile individuals have raised concerns regarding the potential for establishment and proliferation of reproducing populations. The objectives of this study were to: 1) estimate age and growth of grass carp captured in the Great Lakes to gain information on years in which recruitment has occurred, and 2) to compare the growth of fertile diploid and sterile triploid individuals. We estimated age and growth of grass carp captured from Lakes Erie, Michigan, and Ontario, and some tributary rivers, and compared growth rates of diploid and triploid fish. We also compared growth of Great Lakes grass carp to grass carp captured from the Mississippi River drainage. Ages were estimated using sectioned vertebrae, postcleithra, and sectioned pectoral spines. Lengths-at-age were back-calculated using the von Bertalanffy growth equation and focus-to-annulus measurements from the sectioned vertebrae. We found that Great Lakes grass carp in this study ranged in age from 1 to at least 26 years of age, total lengths ranged from 451 mm to greater than 1 m in length, and had robust growth during the first 5-6 years of life. Age estimates can be used to hind-cast birth years of diploid fish determined by otolith microchemistry and stable isotopes to have been naturally reproduced in Great Lakes tributaries. This can in turn be used to examine hydrologic conditions that were suitable for successful natural reproduction. Growth data will be useful in bioenergetics models for estimation of the effects of grass carp herbivory on Great Lakes vegetation.

Tuesday January 26, 2016 2:40pm - 3:00pm EST
Emerald A