Reproductive Behavior, Incubation and Mortality of Eggs, and Postlarval Food Selection in the White Crappie

Abstract

Observations of white crappie nests and spawning were made during 1965 and 1966 in pens built in a pond at the Gavins Point National Fish Hatchery, Yankton, South Dakota. Males exhibited territorial behavior, swept the spawning sites, and cared for eggs and prolarvae. A well defined nest depression was not constructed. No substrate preference for nesting was apparent, but fish appeared to select areas near objects or bottom vegetation. Polygamy and multiple spawnings by an individual fish occurred. Water depths over nests ranged from 20 to 97 cm; nests were in deeper water in 1965 than in 1966. Spawning occurred over a 20-day period in 1965 (14 May to 3 June) and a 29-day period in 1966 (17 May to 15 June). Water temperatures at spawning ranged from 14 to 23 C, with most spawning taking place at 16 to 20 C. Although April and May temperatures averaged 4.5 C lower in 1966 than in 1965, spawning in 1966 began only 3 days later than in 1965. Up to 50 spawning acts were observed during one spawning run and the longest lasted 145 min. Each act lasted from 2 to 5 sec with most lasting 4. Intervals between spawning acts ranged from one-half to 20 min. The periods of egg incubation ranged from 42 to 103 hr and most rapid hatching occurred at warmer temperatures. Highest egg mortality with correspondingly longer incubation periods occurred in nests when water temperatures were lowest. The average time between start of hatching and departure of broods from the nests was 95 hr (range, 51 to 162 hr). Larvae absorbed the yolk sac when 4.5 to 4.6 mm long. Nauplii were the most important food item of larvae at the initiation of active feeding. As fish attained a size of 6.0 to 7.9 mm, a sharp increase in selection of Cyclops occurred, and Daphnia became a significant food item of fish 10.0 to 13.9 mm long. Observations suggest that low temperatures before and during the spawning season may affect year-class strength.