(Alarcon 1999; Irons et al. 2011; Bouska et al. 2014). More males than females were found in expanding Silver Carp (1.2:1) and Bighead Carp (1.3:1) populations (Abdusamadov 1987). In the present study, Lake Barkley sex ratios were skewed towards males (1.70 males: 1 female) but the ratio was skewed towards more females (0.71 males: 1 female) in Kentucky Lake. Sex ratios may play an essential role in bigheaded carp management and facilitate inferences on population growth potential and stock–recruitment relationships (Irons et al. 2011; Bouska et al. 2014). Age-3 Silver Carp in the present were gravid with eggs. However, no age-1 or age-2 fish were collected to confirm age-at-maturity in Kentucky Lake and Lake Barkley. Maturation schedules for bigheaded carps are known to vary among systems (Kolar et al. 2007) and are determined by growth rates during the first year of life (Kamilov 1987, cited in Williamson and Garvey 2005). Silver Carp reach maturity at age 2 in the middle Mississippi River (Williamson and Garvey 2005) and age 3 in the Illinois River (Irons et al. 2010). Using mean back-calculations of lengths and examining fin rays, Silver Carp in the middle Mississippi River were estimated to reach 318 mm TL by the end of their second growing season (Williamson and Garvey 2005); whereas, YOY Silver Carp in Kentucky Lake and Lake Barkley reached 217 mm TL and 272 mm TL, respectively, by October during their first growing season. This evidence suggests female Silver Carp in Kentucky Lake and Lake Barkley may reach maturity before age 3. Gravid Silver Carp were observed in all seasons and fish devoid of eggs were observed in all seasons except winter. DeRose and Spier (Murray State University, unpublished data) collected Silver Carp each month from Kentucky Lake and they could not determine a definitive spawning time. Some of the Silver Carp collected below
(Alarcon 1999; Irons et al. 2011; Bouska et al. 2014). More males than females were found in expanding Silver Carp (1.2:1) and Bighead Carp (1.3:1) populations (Abdusamadov 1987). In the present study, Lake Barkley sex ratios were skewed towards males (1.70 males: 1 female) but the ratio was skewed towards more females (0.71 males: 1 female) in Kentucky Lake. Sex ratios may play an essential role in bigheaded carp management and facilitate inferences on population growth potential and stock–recruitment relationships (Irons et al. 2011; Bouska et al. 2014). Age-3 Silver Carp in the present were gravid with eggs. However, no age-1 or age-2 fish were collected to confirm age-at-maturity in Kentucky Lake and Lake Barkley. Maturation schedules for bigheaded carps are known to vary among systems (Kolar et al. 2007) and are determined by growth rates during the first year of life (Kamilov 1987, cited in Williamson and Garvey 2005). Silver Carp reach maturity at age 2 in the middle Mississippi River (Williamson and Garvey 2005) and age 3 in the Illinois River (Irons et al. 2010). Using mean back-calculations of lengths and examining fin rays, Silver Carp in the middle Mississippi River were estimated to reach 318 mm TL by the end of their second growing season (Williamson and Garvey 2005); whereas, YOY Silver Carp in Kentucky Lake and Lake Barkley reached 217 mm TL and 272 mm TL, respectively, by October during their first growing season. This evidence suggests female Silver Carp in Kentucky Lake and Lake Barkley may reach maturity before age 3. Gravid Silver Carp were observed in all seasons and fish devoid of eggs were observed in all seasons except winter. DeRose and Spier (Murray State University, unpublished data) collected Silver Carp each month from Kentucky Lake and they could not determine a definitive spawning time. Some of the Silver Carp collected below
Ridgway_Thesis_8_1_2016_ProQuest-1.docx