LENGTH AT AGE ESTIMATES OF BLACK CRAPPIE AND WHITE CRAPPIE AMONG LAKE CLASSES, RESERVOIRS, IMPOUNDMENTS, AND RIVERS

Abstract: We estimated lengths at ages 1 through 5 of black crappies from 964 water bodies (natural lakes, reservoirs, impoundments, and rivers) and white crappies from 76 water bodies in Minnesota. We report herein mean lengths at ages 1 through 5 of both species by lake class, reservoirs (man-made and natural), impoundments, and rivers. Mean lengths at ages 1 through 5 of black crappies differed significantly (P < 0.0001) among 32 lake classes, reservoirs, impoundments, and rivers. Conversely, white crappie lengths at the same ages did not differ as strongly (P ranged from 0.0002 to 0.0609) among nine lake classes, reservoirs, and impoundments. White crappie lengths frequently exceeded black crappie lengths at the same ages, but the opposite did not occur. Lengths at age 1 of both species increased from north to south, and appeared related to spawning and hatching times. However, longer lengths at older ages of both crappie species occurred in more productive waters, longer lengths at older ages of black crappies occurred in lakes and reservoirs with higher gill net catch per unit effort (CPUE) of walleye, and longer lengths at older ages of white crappies occurred in lakes with very low trap net CPUE of pumpkinseed. Increased lengths at age of one or both species also occurred in waters with low CPUE of bluegill, bowfin, and northern pike; high CPUE of black bullhead and yellow perch; and in lakes or reservoirs with low aquatic plant diversity or abundance. Diet of both species consisted of primarily dipterans, but fish became more important forage as crappie sizes increased. Lastly, black crappie lengths at ages 4 and 5 in lakes declined with increasing angling pressure