Seasonal Variation in Population Characteristics of Gizzard Shad

ABSTRACT

The gizzard shad (Dorosoma cepedianum) is an important species in midwestern lakes and reservoirs, which has both positive and negative effects on sport fisheries. Ths study was conducted to document seasonal variation in population characteristics (i.e., catch rates, condition, size and age structure, and growth) of gizzard shad in Glen Elder Reservoir, Kansas. Fish were sampled monthly from June 1999 to May 2000 using experimental gill nets. Catch rates were highest during the spring (March, April, May) for all year classes, except the 1998 year class where catch per unit effort was highest during the fall (September, October, November) This resulted from recruitment of the 1998 year class to the sampling gear. Recruitment of the 1998 year class to the gill nets was also reflected by a skewed age distribution and a decline in proportional stock density (PSD) from 89 during the spring to 59 in the fall. Mean relative weight (Wr) exceeded 80 for all year classes and seasons and was generally highest during the spring. Growth of gizzard shad bas similar to that of other midwestern and southern populations. Fish grew rapidly during the first year of life, and most of their annual growth was attained during late spring and early summer.