Bluegill Populations Associated with Water Lily, Water Shield and Pondweed Stands: Management Implications

Small bluegills {Lepomis macrochirus) were collected weekly with unbaited minnow traps from stands of water lily (Nymphaea odorata), water shield (Brasenia schreberi), and pondweed {Potamogeton nodosus) located in Bluff Lake, Noxubee National Wildlife Refuge, Oktibbeha County, Mississippi, during July-October 1990 (JV = 1 5 sample dates). Average stem density within macrophyte stands was 19.25 (SD = 2.31), 208.81 (SD = 12.92), and 866.50 (SD = 75.11) stems/m2 for water lily, water shield, and pondweed, respectively. Pondweed exhibited significantly higher surface coverage (proportion of sample plot covered on surface, mean = 0.93, SD = 0.03) than water lily (mean = 0.72, SD = 0.06) or water shield (mean = 0.76, SD = 0.06). Catch per unit of effort (CPUE) for number of bluegill (fish/trap-night) and CPUE for weight of bluegill (g/trap-night) were significantly greater for samples from pondweed than for those from water lily or water shield. Water lily and water shield did not differ with respect to CPUE for bluegill number nor weight. Significantly longer and heavier bluegill were captured from pondweed stands, while water lily and water shield did not differ with respect to sampled bluegill length nor weight. Plant taxon appeared to have no effect on bluegill condition; while more and larger bluegill were captured from pondweed, condition of sampled bluegill remained constant among plant taxa. In small impoundments where bluegill recruitment is limited, as can be the case in clear, macrophyte-free waters, with significant predation by largemouth bass, selective management for plants such as pondweed, which have relatively dense, underwater leaf/stem complexes and relatively small interstices, may assist in the maintenance of viable bluegill stocks.

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