Differential Growth of Young-of-Year Gizzard Shad in Several Kentucky Reservoirs

Abstract Protracted spawning of gizzard shad Dorosoma cepedianumwas not responsible for the small juvenile shad collected during the fall in two Kentucky reservoirs and one hatchery pond. Gonadosomatic indices of female gizzard shad at Taylorsville Lake and the number of gizzard shad 10 mm and smaller collected in four study lakes did not increase following a mid-July water-level rise. Large numbers of small gizzard shad were collected during the fall at Cave Run and Taylorsville lakes and in one of the hatchery ponds even though spawning was not detected after the normal period. As a result, fall length-frequency distributions of juvenile gizzard shad differed among study lakes and among hatchery ponds. Our data indicated differential and density-dependent growth of young-of-year gizzard shad occurred in the reservoirs and hatchery ponds, and suggested that managers could increase availability of forage by developing techniques to manipulate shad densities.