Population dynamics and food habits of the crappie populations of Douglas Reservoir, Tennessee

Population dynamics, age and growth, and food habits of the crappie population of Douglas Reservoir, Tennessee, were examined for the period of November 1987 through November 1988. White crappie represented 89.1 ± 1.7% (p=0.95) of the crappie population. Length-frequency distributions of the black and white crappie collected during fall trapnetting revealed 74.3 and 94.9%, respectively, were 152.3 mm or less in length. The Proportional Stock Density (PSD) calculated for the black crappie population was below the accepted range (40-60) . Similarly, the Relative Stock Density for preferred blaqck crappie (RSD-P) was below the accepted range (15-20). The PSD calculated for white crappie was within the accepted range and the RSD-P for preferred white crappie exceeded the accepted range. Relative Stock Density values calculated for memerorable (RSD-M) and trophy (RSD-T) white crappie were below the accepted range (10-15). Both black and white crappie populations were evaluated using the methodology proposed by Colvin and Vasey (1984). The white crappie population was rated as good and the black crappie population as poor. The black crappie population was comprised of 4 age classes. Black crappie attained a mean length of 107 mm at age 1, 160 mm at age 2, and 222 mm at age 3. The white crappie population was comprised of 5 age classes. White crappie attained a mean length of 119 mm age 1, 170 mm at age 2, 232 mm at age 3, and 285 mm at age 4. The overall Relative weight (Wr) values for the black and white crappie populations were 66.7 and 71.1, respectively, well below the accepted range (100 ± 5). Black crappie Wr values based on 25 mm length classes were also below the accepted range. White crappie Wr values based on 25 mm length classes generally increased as the length class increased. The 251-275 mm and greater length classes had acceptable Wr values. Relative Weight values calculated monthly from December 1987 through November 1988 generally acceptable with little difference between sexes. The proportion of females was higher in both black and white crappie samples. Monthly Gonadosomatic Index (GSI) values and surface temperatures suggested white crappie spawning occurred from mid April through May. Insects represented 65% of the identified food items consumed by white crappie. Dipterans comprised 45% of the total identified insects. Although chironomid larvae was the primary food item consumed during the month of December, the highest percentage of forage fish was also consumed. The Mayfly Leptophlebia and the stonefly Taeniopteryx were the primary food items consumed during January and February. Chironomid and Chaoborus larvae were the primary food items consumed during March, April, May, June, August and September. Leptodora kindti was the primary food Item consumed in July, October, and November. In general, the larger length classes of crappie consumed the larger prey items. Only the 351-375 mm length class of white crappie consumed only fish.