28 DECEMBER 2012 • WORLD AQUACULTURE • WWW.WAS.ORG can spawn with any sunfish. However, a bluegill female will not spawn naturally with a redear male. Ten females and five males of each cross (one cross per pond) were stocked into each spawning structure on the same day. Nests were inspected each day and, when successful spawns were observed, adults were removed from the structure. When fry left the nests, spawning structures were removed from ponds. Two weeks after swimup we began feeding a crumbled diet for fry (Silver Cup® Granulated) with 52 percent protein and 16 percent lipid. Feed particle sizes were increased through the summer as fish grew. Fish were fed ad libitum twice daily. Overwinter in RAS Phase All fish were harvested from each pond in late October and placed in an indoor recirculating system (Fig. 3) for continued grow-out, which is particularly important in northern climates where growth in nature stops. The duration of the indoor phase was 150 days. The recirculating system at Lincoln University consists of 24 794-L tanks, a UV-light system, two 3-m3 partially submerged Evaluating Hybrid Sunfish Production at Lincoln University At Lincoln University in Jefferson City, MO, we investigated methods for producing food-size bluegill and compared the growth of hybrids with bluegills. Studies comparing bluegill with a green sunfish ♀ × bluegill ♂ sunfish hybrid are limited. A study was designed to compare the following crosses (female × male): bluegill × bluegill (control), redear sunfish × bluegill, green sunfish × bluegill and warmouth × bluegill. The objectives were to measure performance over the entire life-cycle of the fish, from breeding to maturity (two-year fish). First-Year Pond Phase Four 0.10-ha ponds were fertilized with alfalfa meal and triple superphosphate. Spawning structures (Fig. 1) were placed in each pond with five nests in each structure (Fig. 2). Nests were made with plastic tubs that were about 8 in in diameter and 4 in deep. Nests were half-filled with small (¼ to ½ in) washed gravel or rocks. We used crosses that occur in nature because male bluegill FIGURE 4. Final weight of sunfish hybrids cultured in indoor recirculating systems. These fish were then stocked in ponds for second-year grow-out. FIGURE 6. Feed conversion ratio by aggregate populations of sunfish hybrids in four 100-m2 ponds. FIGURE 5. Final weight of sunfish hybrids after second-year pond harvest. FIGURE 7. Fillet yield and dress-out percentage in bluegill and sunfish hybrids.
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